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     GNAT User's Guide for Native Platforms , November 18, 2015

     AdaCore

     Copyright (C) 2008-2016, Free Software Foundation


File: gnat_ugn.info,  Node: Top,  Next: About This Guide,  Up: (dir)

GNAT User's Guide for Native Platforms
**************************************

     GNAT User's Guide for Native Platforms , November 18, 2015

     AdaCore

     Copyright (C) 2008-2016, Free Software Foundation

`GNAT, The GNU Ada Development Environment'

GCC version 6.5.0
AdaCore

Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3 or
any later version published by the Free Software Foundation; with no
Invariant Sections, with the Front-Cover Texts being "GNAT User's Guide
for Native Platforms", and with no Back-Cover Texts.  A copy of the
license is included in the section entitled *note GNU Free
Documentation License: 1.

* Menu:

* About This Guide::
* Getting Started with GNAT::
* The GNAT Compilation Model::
* Building Executable Programs with GNAT::
* GNAT Project Manager::
* Tools Supporting Project Files::
* GNAT Utility Programs::
* GNAT and Program Execution::
* Platform-Specific Information::
* Example of Binder Output File::
* Elaboration Order Handling in GNAT::
* Inline Assembler::
* GNU Free Documentation License::
* Index::

 --- The Detailed Node Listing ---

About This Guide

* What This Guide Contains::
* What You Should Know before Reading This Guide::
* Related Information::
* A Note to Readers of Previous Versions of the Manual::
* Conventions::

Getting Started with GNAT

* Running GNAT::
* Running a Simple Ada Program::
* Running a Program with Multiple Units::
* Using the gnatmake Utility::

The GNAT Compilation Model

* Source Representation::
* Foreign Language Representation::
* File Naming Topics and Utilities::
* Configuration Pragmas::
* Generating Object Files::
* Source Dependencies::
* The Ada Library Information Files::
* Binding an Ada Program::
* GNAT and Libraries::
* Conditional Compilation::
* Mixed Language Programming::
* GNAT and Other Compilation Models::
* Using GNAT Files with External Tools::

Foreign Language Representation

* Latin-1::
* Other 8-Bit Codes::
* Wide_Character Encodings::
* Wide_Wide_Character Encodings::

File Naming Topics and Utilities

* File Naming Rules::
* Using Other File Names::
* Alternative File Naming Schemes::
* Handling Arbitrary File Naming Conventions with gnatname::
* File Name Krunching with gnatkr::
* Renaming Files with gnatchop::

Handling Arbitrary File Naming Conventions with gnatname

* Arbitrary File Naming Conventions::
* Running gnatname::
* Switches for gnatname::
* Examples of gnatname Usage::

File Name Krunching with gnatkr

* About gnatkr::
* Using gnatkr::
* Krunching Method::
* Examples of gnatkr Usage::

Renaming Files with gnatchop

* Handling Files with Multiple Units::
* Operating gnatchop in Compilation Mode::
* Command Line for gnatchop::
* Switches for gnatchop::
* Examples of gnatchop Usage::

Configuration Pragmas

* Handling of Configuration Pragmas::
* The Configuration Pragmas Files::

GNAT and Libraries

* Introduction to Libraries in GNAT::
* General Ada Libraries::
* Stand-alone Ada Libraries::
* Rebuilding the GNAT Run-Time Library::

General Ada Libraries

* Building a library::
* Installing a library::
* Using a library::

Stand-alone Ada Libraries

* Introduction to Stand-alone Libraries::
* Building a Stand-alone Library::
* Creating a Stand-alone Library to be used in a non-Ada context::
* Restrictions in Stand-alone Libraries::

Conditional Compilation

* Modeling Conditional Compilation in Ada::
* Preprocessing with gnatprep::
* Integrated Preprocessing::

Modeling Conditional Compilation in Ada

* Use of Boolean Constants::
* Debugging - A Special Case::
* Conditionalizing Declarations::
* Use of Alternative Implementations::
* Preprocessing::

Preprocessing with gnatprep

* Preprocessing Symbols::
* Using gnatprep::
* Switches for gnatprep::
* Form of Definitions File::
* Form of Input Text for gnatprep::

Mixed Language Programming

* Interfacing to C::
* Calling Conventions::
* Building Mixed Ada and C++ Programs::
* Generating Ada Bindings for C and C++ headers::
* Generating C Headers for Ada Specifications::

Building Mixed Ada and C++ Programs

* Interfacing to C++::
* Linking a Mixed C++ & Ada Program::
* A Simple Example::
* Interfacing with C++ constructors::
* Interfacing with C++ at the Class Level::

Generating Ada Bindings for C and C++ headers

* Running the Binding Generator::
* Generating Bindings for C++ Headers::
* Switches::

Generating C Headers for Ada Specifications

* Running the C Header Generator::

GNAT and Other Compilation Models

* Comparison between GNAT and C/C++ Compilation Models::
* Comparison between GNAT and Conventional Ada Library Models::

Using GNAT Files with External Tools

* Using Other Utility Programs with GNAT::
* The External Symbol Naming Scheme of GNAT::

Building Executable Programs with GNAT

* Building with gnatmake::
* Compiling with gcc::
* Compiler Switches::
* Binding with gnatbind::
* Linking with gnatlink::
* Using the GNU make Utility::

Building with gnatmake

* Running gnatmake::
* Switches for gnatmake::
* Mode Switches for gnatmake::
* Notes on the Command Line::
* How gnatmake Works::
* Examples of gnatmake Usage::

Compiling with gcc

* Compiling Programs::
* Search Paths and the Run-Time Library (RTL): Search Paths and the Run-Time Library RTL.
* Order of Compilation Issues::
* Examples::

Compiler Switches

* Alphabetical List of All Switches::
* Output and Error Message Control::
* Warning Message Control::
* Debugging and Assertion Control::
* Validity Checking::
* Style Checking::
* Run-Time Checks::
* Using gcc for Syntax Checking::
* Using gcc for Semantic Checking::
* Compiling Different Versions of Ada::
* Character Set Control::
* File Naming Control::
* Subprogram Inlining Control::
* Auxiliary Output Control::
* Debugging Control::
* Exception Handling Control::
* Units to Sources Mapping Files::
* Code Generation Control::

Binding with gnatbind

* Running gnatbind::
* Switches for gnatbind::
* Command-Line Access::
* Search Paths for gnatbind::
* Examples of gnatbind Usage::

Switches for gnatbind

* Consistency-Checking Modes::
* Binder Error Message Control::
* Elaboration Control::
* Output Control::
* Dynamic Allocation Control::
* Binding with Non-Ada Main Programs::
* Binding Programs with No Main Subprogram::

Linking with gnatlink

* Running gnatlink::
* Switches for gnatlink::

Using the GNU make Utility

* Using gnatmake in a Makefile::
* Automatically Creating a List of Directories::
* Generating the Command Line Switches::
* Overcoming Command Line Length Limits::

GNAT Project Manager

* Introduction::
* Building With Projects::
* Organizing Projects into Subsystems::
* Scenarios in Projects::
* Library Projects::
* Project Extension::
* Aggregate Projects::
* Aggregate Library Projects::
* Project File Reference::

Building With Projects

* Source Files and Directories::
* Duplicate Sources in Projects::
* Object and Exec Directory::
* Main Subprograms::
* Tools Options in Project Files::
* Compiling with Project Files::
* Executable File Names::
* Avoid Duplication With Variables::
* Naming Schemes::
* Installation::
* Distributed support::

Organizing Projects into Subsystems

* Project Dependencies::
* Cyclic Project Dependencies::
* Sharing Between Projects::
* Global Attributes::

Library Projects

* Building Libraries::
* Using Library Projects::
* Stand-alone Library Projects::
* Installing a library with project files::

Project Extension

* Project Hierarchy Extension::

Aggregate Projects

* Building all main programs from a single project tree::
* Building a set of projects with a single command::
* Define a build environment::
* Performance improvements in builder::
* Syntax of aggregate projects::
* package Builder in aggregate projects::

Aggregate Library Projects

* Building aggregate library projects::
* Syntax of aggregate library projects::

Project File Reference

* Project Declaration::
* Qualified Projects::
* Declarations::
* Packages::
* Expressions::
* External Values::
* Typed String Declaration::
* Variables::
* Case Constructions::
* Attributes::

Attributes

* Project Level Attributes::
* Package Binder Attributes::
* Package Builder Attributes::
* Package Clean Attributes::
* Package Compiler Attributes::
* Package Cross_Reference Attributes::
* Package Finder Attributes::
* Package gnatls Attributes::
* Package IDE Attributes::
* Package Install Attributes::
* Package Linker Attributes::
* Package Naming Attributes::
* Package Remote Attributes::
* Package Stack Attributes::
* Package Synchronize Attributes::

Tools Supporting Project Files

* gnatmake and Project Files::
* The GNAT Driver and Project Files::

gnatmake and Project Files

* Switches Related to Project Files::
* Switches and Project Files::
* Specifying Configuration Pragmas::
* Project Files and Main Subprograms::
* Library Project Files::

GNAT Utility Programs

* The File Cleanup Utility gnatclean::
* The GNAT Library Browser gnatls::
* The Cross-Referencing Tools gnatxref and gnatfind::
* The Ada to HTML Converter gnathtml::

The File Cleanup Utility gnatclean

* Running gnatclean::
* Switches for gnatclean::

The GNAT Library Browser gnatls

* Running gnatls::
* Switches for gnatls::
* Example of gnatls Usage::

The Cross-Referencing Tools gnatxref and gnatfind

* gnatxref Switches::
* gnatfind Switches::
* Project Files for gnatxref and gnatfind::
* Regular Expressions in gnatfind and gnatxref::
* Examples of gnatxref Usage::
* Examples of gnatfind Usage::

Examples of gnatxref Usage

* General Usage::
* Using gnatxref with vi::

The Ada to HTML Converter gnathtml

* Invoking gnathtml::
* Installing gnathtml::

GNAT and Program Execution

* Running and Debugging Ada Programs::
* Code Coverage and Profiling::
* Improving Performance::
* Overflow Check Handling in GNAT::
* Performing Dimensionality Analysis in GNAT::
* Stack Related Facilities::
* Memory Management Issues::

Running and Debugging Ada Programs

* The GNAT Debugger GDB::
* Running GDB::
* Introduction to GDB Commands::
* Using Ada Expressions::
* Calling User-Defined Subprograms::
* Using the next Command in a Function::
* Stopping When Ada Exceptions Are Raised::
* Ada Tasks::
* Debugging Generic Units::
* Remote Debugging with gdbserver::
* GNAT Abnormal Termination or Failure to Terminate::
* Naming Conventions for GNAT Source Files::
* Getting Internal Debugging Information::
* Stack Traceback::

Stack Traceback

* Non-Symbolic Traceback::
* Symbolic Traceback::

Code Coverage and Profiling

* Code Coverage of Ada Programs with gcov::
* Profiling an Ada Program with gprof::

Code Coverage of Ada Programs with gcov

* Quick startup guide::
* GNAT specifics::

Profiling an Ada Program with gprof

* Compilation for profiling::
* Program execution::
* Running gprof::
* Interpretation of profiling results::

Improving Performance

* Performance Considerations::
* Text_IO Suggestions::
* Reducing Size of Executables with Unused Subprogram/Data Elimination::

Performance Considerations

* Controlling Run-Time Checks::
* Use of Restrictions::
* Optimization Levels::
* Debugging Optimized Code::
* Inlining of Subprograms::
* Floating_Point_Operations::
* Vectorization of loops::
* Other Optimization Switches::
* Optimization and Strict Aliasing::
* Aliased Variables and Optimization::
* Atomic Variables and Optimization::
* Passive Task Optimization::

Reducing Size of Executables with Unused Subprogram/Data Elimination

* About unused subprogram/data elimination::
* Compilation options::
* Example of unused subprogram/data elimination::

Overflow Check Handling in GNAT

* Background::
* Management of Overflows in GNAT::
* Specifying the Desired Mode::
* Default Settings::
* Implementation Notes::

Stack Related Facilities

* Stack Overflow Checking::
* Static Stack Usage Analysis::
* Dynamic Stack Usage Analysis::

Memory Management Issues

* Some Useful Memory Pools::
* The GNAT Debug Pool Facility::

Platform-Specific Information

* Run-Time Libraries::
* Specifying a Run-Time Library::
* Microsoft Windows Topics::
* Mac OS Topics::

Run-Time Libraries

* Summary of Run-Time Configurations::

Specifying a Run-Time Library

* Choosing the Scheduling Policy::
* Solaris-Specific Considerations::
* Solaris Threads Issues::
* AIX-Specific Considerations::

Microsoft Windows Topics

* Using GNAT on Windows::
* Using a network installation of GNAT::
* CONSOLE and WINDOWS subsystems::
* Temporary Files::
* Mixed-Language Programming on Windows::
* Windows Specific Add-Ons::

Mixed-Language Programming on Windows

* Windows Calling Conventions::
* Introduction to Dynamic Link Libraries (DLLs): Introduction to Dynamic Link Libraries DLLs.
* Using DLLs with GNAT::
* Building DLLs with GNAT Project files::
* Building DLLs with GNAT::
* Building DLLs with gnatdll::
* Ada DLLs and Finalization::
* Creating a Spec for Ada DLLs::
* GNAT and Windows Resources::
* Using GNAT DLLs from Microsoft Visual Studio Applications::
* Debugging a DLL::
* Setting Stack Size from gnatlink::
* Setting Heap Size from gnatlink::

Windows Calling Conventions

* C Calling Convention::
* Stdcall Calling Convention::
* Win32 Calling Convention::
* DLL Calling Convention::

Using DLLs with GNAT

* Creating an Ada Spec for the DLL Services::
* Creating an Import Library::

Building DLLs with gnatdll

* Limitations When Using Ada DLLs from Ada::
* Exporting Ada Entities::
* Ada DLLs and Elaboration::

Creating a Spec for Ada DLLs

* Creating the Definition File::
* Using gnatdll::

GNAT and Windows Resources

* Building Resources::
* Compiling Resources::
* Using Resources::

Debugging a DLL

* Program and DLL Both Built with GCC/GNAT::
* Program Built with Foreign Tools and DLL Built with GCC/GNAT::

Windows Specific Add-Ons

* Win32Ada::
* wPOSIX::

Mac OS Topics

* Codesigning the Debugger::

Elaboration Order Handling in GNAT

* Elaboration Code::
* Checking the Elaboration Order::
* Controlling the Elaboration Order::
* Controlling Elaboration in GNAT - Internal Calls::
* Controlling Elaboration in GNAT - External Calls::
* Default Behavior in GNAT - Ensuring Safety::
* Treatment of Pragma Elaborate::
* Elaboration Issues for Library Tasks::
* Mixing Elaboration Models::
* What to Do If the Default Elaboration Behavior Fails::
* Elaboration for Indirect Calls::
* Summary of Procedures for Elaboration Control::
* Other Elaboration Order Considerations::
* Determining the Chosen Elaboration Order::

Inline Assembler

* Basic Assembler Syntax::
* A Simple Example of Inline Assembler::
* Output Variables in Inline Assembler::
* Input Variables in Inline Assembler::
* Inlining Inline Assembler Code::
* Other Asm Functionality::

Other Asm Functionality

* The Clobber Parameter::
* The Volatile Parameter::


File: gnat_ugn.info,  Node: About This Guide,  Next: Getting Started with GNAT,  Prev: Top,  Up: Top

1 About This Guide
******************

This guide describes the use of GNAT, a compiler and software
development toolset for the full Ada programming language.  It
documents the features of the compiler and tools, and explains how to
use them to build Ada applications.

GNAT implements Ada 95, Ada 2005 and Ada 2012, and it may also be
invoked in Ada 83 compatibility mode.  By default, GNAT assumes Ada
2012, but you can override with a compiler switch (*note Compiling
Different Versions of Ada: 6.)  to explicitly specify the language
version.  Throughout this manual, references to 'Ada' without a year
suffix apply to all Ada 95/2005/2012 versions of the language.

* Menu:

* What This Guide Contains::
* What You Should Know before Reading This Guide::
* Related Information::
* A Note to Readers of Previous Versions of the Manual::
* Conventions::


File: gnat_ugn.info,  Node: What This Guide Contains,  Next: What You Should Know before Reading This Guide,  Up: About This Guide

1.1 What This Guide Contains
============================

This guide contains the following chapters:

   * *note Getting Started with GNAT: 8. describes how to get started
     compiling and running Ada programs with the GNAT Ada programming
     environment.

   * *note The GNAT Compilation Model: 9. describes the compilation
     model used by GNAT.

   * *note Building Executable Programs with GNAT: a. describes how to
     use the main GNAT tools to build executable programs, and it also
     gives examples of using the GNU make utility with GNAT.

   * *note GNAT Project Manager: b. describes how to use project files
     to organize large projects.

   * *note Tools Supporting Project Files: c. described how to use the
     project facility in conjunction with various GNAT tools.

   * *note GNAT Utility Programs: d. explains the various utility
     programs that are included in the GNAT environment

   * *note GNAT and Program Execution: e. covers a number of topics
     related to running, debugging, and tuning the performace of
     programs developed with GNAT

Appendices cover several additional topics:

   * *note Platform-Specific Information: f. describes the different
     run-time library implementations and also presents information on
     how to use GNAT on several specific platforms

   * *note Example of Binder Output File: 10. shows the source code for
     the binder output file for a sample program.

   * *note Elaboration Order Handling in GNAT: 11. describes how GNAT
     helps you deal with elaboration order issues.

   * *note Inline Assembler: 12. shows how to use the inline assembly
     facility in an Ada program.


File: gnat_ugn.info,  Node: What You Should Know before Reading This Guide,  Next: Related Information,  Prev: What This Guide Contains,  Up: About This Guide

1.2 What You Should Know before Reading This Guide
==================================================

This guide assumes a basic familiarity with the Ada 95 language, as
described in the International Standard ANSI/ISO/IEC-8652:1995, January
1995.  It does not require knowledge of the features introduced by Ada
2005 or Ada 2012.  Reference manuals for Ada 95, Ada 2005, and Ada 2012
are included in the GNAT documentation package.


File: gnat_ugn.info,  Node: Related Information,  Next: A Note to Readers of Previous Versions of the Manual,  Prev: What You Should Know before Reading This Guide,  Up: About This Guide

1.3 Related Information
=======================

For further information about Ada and related tools, please refer to the
following documents:

   * `Ada 95 Reference Manual', `Ada 2005 Reference Manual', and `Ada
     2012 Reference Manual', which contain reference material for the
     several revisions of the Ada language standard.

   * `GNAT Reference_Manual', which contains all reference material for
     the GNAT implementation of Ada.

   * `Using the GNAT Programming Studio', which describes the GPS
     Integrated Development Environment.

   * `GNAT Programming Studio Tutorial', which introduces the main GPS
     features through examples.

   * `Debugging with GDB', for all details on the use of the GNU
     source-level debugger.

   * `GNU Emacs Manual', for full information on the extensible editor
     and programming environment Emacs.


File: gnat_ugn.info,  Node: A Note to Readers of Previous Versions of the Manual,  Next: Conventions,  Prev: Related Information,  Up: About This Guide

1.4 A Note to Readers of Previous Versions of the Manual
========================================================

In early 2015 the GNAT manuals were transitioned to the
reStructuredText (rst) / Sphinx documentation generator technology.
During that process the `GNAT User's Guide' was reorganized so that
related topics would be described together in the same chapter or
appendix.  Here's a summary of the major changes realized in the new
document structure.

   * *note The GNAT Compilation Model: 9. has been extended so that it
     now covers the following material:

        - The `gnatname', `gnatkr', and `gnatchop' tools

        - *note Configuration Pragmas: 16.

        - *note GNAT and Libraries: 17.

        - *note Conditional Compilation: 18. including *note
          Preprocessing with gnatprep: 19.  and *note Integrated
          Preprocessing: 1a.

        - *note Generating Ada Bindings for C and C++ headers: 1b.

        - *note Using GNAT Files with External Tools: 1c.

   * *note Building Executable Programs with GNAT: a. is a new chapter
     consolidating the following content:

        - *note Building with gnatmake: 1d.

        - *note Compiling with gcc: 1e.

        - *note Binding with gnatbind: 1f.

        - *note Linking with gnatlink: 20.

        - *note Using the GNU make Utility: 21.

   * *note GNAT Utility Programs: d. is a new chapter consolidating the
     information about several GNAT tools:

        - *note The File Cleanup Utility gnatclean: 22.

        - *note The GNAT Library Browser gnatls: 23.

        - *note The Cross-Referencing Tools gnatxref and gnatfind: 24.

        - *note The Ada to HTML Converter gnathtml: 25.

   * *note GNAT and Program Execution: e. is a new chapter
     consolidating the following:

        - *note Running and Debugging Ada Programs: 26.

        - *note Code Coverage and Profiling: 27.

        - *note Improving Performance: 28.

        - *note Overflow Check Handling in GNAT: 29.

        - *note Performing Dimensionality Analysis in GNAT: 2a.

        - *note Stack Related Facilities: 2b.

        - *note Memory Management Issues: 2c.

   * *note Platform-Specific Information: f. is a new appendix
     consolidating the following:

        - *note Run-Time Libraries: 2d.

        - *note Microsoft Windows Topics: 2e.

        - *note Mac OS Topics: 2f.

   * The `Compatibility and Porting Guide' appendix has been moved to
     the `GNAT Reference Manual'. It now includes a section `Writing
     Portable Fixed-Point Declarations' which was previously a separate
     chapter in the `GNAT User's Guide'.


File: gnat_ugn.info,  Node: Conventions,  Prev: A Note to Readers of Previous Versions of the Manual,  Up: About This Guide

1.5 Conventions
===============

Following are examples of the typographical and graphic conventions used
in this guide:

   * `Functions', `utility program names', `standard names', and
     `classes'.

   * `Option flags'

   * `File names'

   * `Variables'

   * `Emphasis'

   * [optional information or parameters]

   * Examples are described by text

         and then shown this way.

   * Commands that are entered by the user are shown as preceded by a
     prompt string comprising the `$' character followed by a space.

   * Full file names are shown with the '/' character as the directory
     separator; e.g., `parent-dir/subdir/myfile.adb'.  If you are using
     GNAT on a Windows platform, please note that the '\' character
     should be used instead.


File: gnat_ugn.info,  Node: Getting Started with GNAT,  Next: The GNAT Compilation Model,  Prev: About This Guide,  Up: Top

2 Getting Started with GNAT
***************************

This chapter describes how to use GNAT's command line interface to build
executable Ada programs.  On most platforms a visually oriented
Integrated Development Environment is also available, the GNAT
Programming Studio (GPS).  GPS offers a graphical "look and feel",
support for development in other programming languages, comprehensive
browsing features, and many other capabilities.  For information on GPS
please refer to `Using the GNAT Programming Studio'.

* Menu:

* Running GNAT::
* Running a Simple Ada Program::
* Running a Program with Multiple Units::
* Using the gnatmake Utility::


File: gnat_ugn.info,  Node: Running GNAT,  Next: Running a Simple Ada Program,  Up: Getting Started with GNAT

2.1 Running GNAT
================

Three steps are needed to create an executable file from an Ada source
file:

   * The source file(s) must be compiled.

   * The file(s) must be bound using the GNAT binder.

   * All appropriate object files must be linked to produce an
     executable.

All three steps are most commonly handled by using the `gnatmake'
utility program that, given the name of the main program, automatically
performs the necessary compilation, binding and linking steps.


File: gnat_ugn.info,  Node: Running a Simple Ada Program,  Next: Running a Program with Multiple Units,  Prev: Running GNAT,  Up: Getting Started with GNAT

2.2 Running a Simple Ada Program
================================

Any text editor may be used to prepare an Ada program.  (If Emacs is
used, the optional Ada mode may be helpful in laying out the program.)
The program text is a normal text file. We will assume in our initial
example that you have used your editor to prepare the following
standard format text file:

    with Ada.Text_IO; use Ada.Text_IO;
    procedure Hello is
    begin
       Put_Line ("Hello WORLD!");
    end Hello;

This file should be named `hello.adb'.  With the normal default file
naming conventions, GNAT requires that each file contain a single
compilation unit whose file name is the unit name, with periods
replaced by hyphens; the extension is `ads' for a spec and `adb' for a
body.  You can override this default file naming convention by use of
the special pragma `Source_File_Name' (for further information please
see *note Using Other File Names: 37.).  Alternatively, if you want to
rename your files according to this default convention, which is
probably more convenient if you will be using GNAT for all your
compilations, then the `gnatchop' utility can be used to generate
correctly-named source files (see *note Renaming Files with gnatchop:
38.).

You can compile the program using the following command (`$' is used as
the command prompt in the examples in this document):

    $ gcc -c hello.adb

`gcc' is the command used to run the compiler. This compiler is capable
of compiling programs in several languages, including Ada and C. It
assumes that you have given it an Ada program if the file extension is
either `.ads' or `.adb', and it will then call the GNAT compiler to
compile the specified file.

The `-c' switch is required. It tells `gcc' to only do a compilation.
(For C programs, `gcc' can also do linking, but this capability is not
used directly for Ada programs, so the `-c' switch must always be
present.)

This compile command generates a file `hello.o', which is the object
file corresponding to your Ada program. It also generates an 'Ada
Library Information' file `hello.ali', which contains additional
information used to check that an Ada program is consistent.  To build
an executable file, use `gnatbind' to bind the program and `gnatlink'
to link it. The argument to both `gnatbind' and `gnatlink' is the name
of the `ALI' file, but the default extension of `.ali' can be omitted.
This means that in the most common case, the argument is simply the
name of the main program:

    $ gnatbind hello
    $ gnatlink hello

A simpler method of carrying out these steps is to use `gnatmake', a
master program that invokes all the required compilation, binding and
linking tools in the correct order. In particular, `gnatmake'
automatically recompiles any sources that have been modified since they
were last compiled, or sources that depend on such modified sources, so
that 'version skew' is avoided.

    $ gnatmake hello.adb

The result is an executable program called `hello', which can be run by
entering:

    $ hello

assuming that the current directory is on the search path for
executable programs.

and, if all has gone well, you will see:

    Hello WORLD!

appear in response to this command.


File: gnat_ugn.info,  Node: Running a Program with Multiple Units,  Next: Using the gnatmake Utility,  Prev: Running a Simple Ada Program,  Up: Getting Started with GNAT

2.3 Running a Program with Multiple Units
=========================================

Consider a slightly more complicated example that has three files: a
main program, and the spec and body of a package:

    package Greetings is
       procedure Hello;
       procedure Goodbye;
    end Greetings;

    with Ada.Text_IO; use Ada.Text_IO;
    package body Greetings is
       procedure Hello is
       begin
          Put_Line ("Hello WORLD!");
       end Hello;

       procedure Goodbye is
       begin
          Put_Line ("Goodbye WORLD!");
       end Goodbye;
    end Greetings;

    with Greetings;
    procedure Gmain is
    begin
       Greetings.Hello;
       Greetings.Goodbye;
    end Gmain;

Following the one-unit-per-file rule, place this program in the
following three separate files:

`greetings.ads'
     spec of package `Greetings'

`greetings.adb'
     body of package `Greetings'

`gmain.adb'
     body of main program

To build an executable version of this program, we could use four
separate steps to compile, bind, and link the program, as follows:

    $ gcc -c gmain.adb
    $ gcc -c greetings.adb
    $ gnatbind gmain
    $ gnatlink gmain

Note that there is no required order of compilation when using GNAT.
In particular it is perfectly fine to compile the main program first.
Also, it is not necessary to compile package specs in the case where
there is an accompanying body; you only need to compile the body. If
you want to submit these files to the compiler for semantic checking
and not code generation, then use the `-gnatc' switch:

    $ gcc -c greetings.ads -gnatc

Although the compilation can be done in separate steps as in the above
example, in practice it is almost always more convenient to use the
`gnatmake' tool. All you need to know in this case is the name of the
main program's source file. The effect of the above four commands can
be achieved with a single one:

    $ gnatmake gmain.adb

In the next section we discuss the advantages of using `gnatmake' in
more detail.


File: gnat_ugn.info,  Node: Using the gnatmake Utility,  Prev: Running a Program with Multiple Units,  Up: Getting Started with GNAT

2.4 Using the `gnatmake' Utility
================================

If you work on a program by compiling single components at a time using
`gcc', you typically keep track of the units you modify. In order to
build a consistent system, you compile not only these units, but also
any units that depend on the units you have modified.  For example, in
the preceding case, if you edit `gmain.adb', you only need to recompile
that file. But if you edit `greetings.ads', you must recompile both
`greetings.adb' and `gmain.adb', because both files contain units that
depend on `greetings.ads'.

`gnatbind' will warn you if you forget one of these compilation steps,
so that it is impossible to generate an inconsistent program as a
result of forgetting to do a compilation. Nevertheless it is tedious and
error-prone to keep track of dependencies among units.  One approach to
handle the dependency-bookkeeping is to use a makefile. However,
makefiles present maintenance problems of their own: if the
dependencies change as you change the program, you must make sure that
the makefile is kept up-to-date manually, which is also an error-prone
process.

The `gnatmake' utility takes care of these details automatically.
Invoke it using either one of the following forms:

    $ gnatmake gmain.adb
    $ gnatmake gmain

The argument is the name of the file containing the main program; you
may omit the extension. `gnatmake' examines the environment,
automatically recompiles any files that need recompiling, and binds and
links the resulting set of object files, generating the executable
file, `gmain'.  In a large program, it can be extremely helpful to use
`gnatmake', because working out by hand what needs to be recompiled can
be difficult.

Note that `gnatmake' takes into account all the Ada rules that
establish dependencies among units. These include dependencies that
result from inlining subprogram bodies, and from generic instantiation.
Unlike some other Ada make tools, `gnatmake' does not rely on the
dependencies that were found by the compiler on a previous compilation,
which may possibly be wrong when sources change. `gnatmake' determines
the exact set of dependencies from scratch each time it is run.


File: gnat_ugn.info,  Node: The GNAT Compilation Model,  Next: Building Executable Programs with GNAT,  Prev: Getting Started with GNAT,  Up: Top

3 The GNAT Compilation Model
****************************

This chapter describes the compilation model used by GNAT. Although
similar to that used by other languages such as C and C++, this model
is substantially different from the traditional Ada compilation models,
which are based on a centralized program library. The chapter covers
the following material:

   * Topics related to source file makeup and naming

        * *note Source Representation: 3f.

        * *note Foreign Language Representation: 40.

        * *note File Naming Topics and Utilities: 41.

   * *note Configuration Pragmas: 16.

   * *note Generating Object Files: 42.

   * *note Source Dependencies: 43.

   * *note The Ada Library Information Files: 44.

   * *note Binding an Ada Program: 45.

   * *note GNAT and Libraries: 17.

   * *note Conditional Compilation: 18.

   * *note Mixed Language Programming: 46.

   * *note GNAT and Other Compilation Models: 47.

   * *note Using GNAT Files with External Tools: 1c.

* Menu:

* Source Representation::
* Foreign Language Representation::
* File Naming Topics and Utilities::
* Configuration Pragmas::
* Generating Object Files::
* Source Dependencies::
* The Ada Library Information Files::
* Binding an Ada Program::
* GNAT and Libraries::
* Conditional Compilation::
* Mixed Language Programming::
* GNAT and Other Compilation Models::
* Using GNAT Files with External Tools::


File: gnat_ugn.info,  Node: Source Representation,  Next: Foreign Language Representation,  Up: The GNAT Compilation Model

3.1 Source Representation
=========================

Ada source programs are represented in standard text files, using
Latin-1 coding. Latin-1 is an 8-bit code that includes the familiar
7-bit ASCII set, plus additional characters used for representing
foreign languages (see *note Foreign Language Representation: 40.  for
support of non-USA character sets). The format effector characters are
represented using their standard ASCII encodings, as follows:

      Character       Effect                      Code
     `VT'            Vertical tab                `16#0B#'
     `HT'            Horizontal tab              `16#09#'
     `CR'            Carriage return             `16#0D#'
     `LF'            Line feed                   `16#0A#'
     `FF'            Form feed                   `16#0C#'


Source files are in standard text file format. In addition, GNAT will
recognize a wide variety of stream formats, in which the end of
physical lines is marked by any of the following sequences: `LF', `CR',
`CR-LF', or `LF-CR'. This is useful in accommodating files that are
imported from other operating systems.

The end of a source file is normally represented by the physical end of
file. However, the control character `16#1A#' (`SUB') is also
recognized as signalling the end of the source file. Again, this is
provided for compatibility with other operating systems where this code
is used to represent the end of file.

Each file contains a single Ada compilation unit, including any pragmas
associated with the unit. For example, this means you must place a
package declaration (a package `spec') and the corresponding body in
separate files. An Ada `compilation' (which is a sequence of
compilation units) is represented using a sequence of files. Similarly,
you will place each subunit or child unit in a separate file.


File: gnat_ugn.info,  Node: Foreign Language Representation,  Next: File Naming Topics and Utilities,  Prev: Source Representation,  Up: The GNAT Compilation Model

3.2 Foreign Language Representation
===================================

GNAT supports the standard character sets defined in Ada as well as
several other non-standard character sets for use in localized versions
of the compiler (*note Character Set Control: 4a.).

* Menu:

* Latin-1::
* Other 8-Bit Codes::
* Wide_Character Encodings::
* Wide_Wide_Character Encodings::


File: gnat_ugn.info,  Node: Latin-1,  Next: Other 8-Bit Codes,  Up: Foreign Language Representation

3.2.1 Latin-1
-------------

The basic character set is Latin-1. This character set is defined by ISO
standard 8859, part 1. The lower half (character codes `16#00#' ...
`16#7F#)' is identical to standard ASCII coding, but the upper half is
used to represent additional characters. These include extended letters
used by European languages, such as French accents, the vowels with
umlauts used in German, and the extra letter A-ring used in Swedish.

For a complete list of Latin-1 codes and their encodings, see the source
file of library unit `Ada.Characters.Latin_1' in file `a-chlat1.ads'.
You may use any of these extended characters freely in character or
string literals. In addition, the extended characters that represent
letters can be used in identifiers.


File: gnat_ugn.info,  Node: Other 8-Bit Codes,  Next: Wide_Character Encodings,  Prev: Latin-1,  Up: Foreign Language Representation

3.2.2 Other 8-Bit Codes
-----------------------

GNAT also supports several other 8-bit coding schemes:

`ISO 8859-2 (Latin-2)'
     Latin-2 letters allowed in identifiers, with uppercase and
     lowercase equivalence.

`ISO 8859-3 (Latin-3)'
     Latin-3 letters allowed in identifiers, with uppercase and
     lowercase equivalence.

`ISO 8859-4 (Latin-4)'
     Latin-4 letters allowed in identifiers, with uppercase and
     lowercase equivalence.

`ISO 8859-5 (Cyrillic)'
     ISO 8859-5 letters (Cyrillic) allowed in identifiers, with
     uppercase and lowercase equivalence.

`ISO 8859-15 (Latin-9)'
     ISO 8859-15 (Latin-9) letters allowed in identifiers, with
     uppercase and lowercase equivalence

`IBM PC (code page 437)'
     This code page is the normal default for PCs in the U.S. It
     corresponds to the original IBM PC character set. This set has
     some, but not all, of the extended Latin-1 letters, but these
     letters do not have the same encoding as Latin-1. In this mode,
     these letters are allowed in identifiers with uppercase and
     lowercase equivalence.

`IBM PC (code page 850)'
     This code page is a modification of 437 extended to include all the
     Latin-1 letters, but still not with the usual Latin-1 encoding. In
     this mode, all these letters are allowed in identifiers with
     uppercase and lowercase equivalence.

`Full Upper 8-bit'
     Any character in the range 80-FF allowed in identifiers, and all
     are considered distinct. In other words, there are no uppercase
     and lowercase equivalences in this range. This is useful in
     conjunction with certain encoding schemes used for some foreign
     character sets (e.g., the typical method of representing Chinese
     characters on the PC).

`No Upper-Half'
     No upper-half characters in the range 80-FF are allowed in
     identifiers.  This gives Ada 83 compatibility for identifier names.

For precise data on the encodings permitted, and the uppercase and
lowercase equivalences that are recognized, see the file `csets.adb' in
the GNAT compiler sources. You will need to obtain a full source release
of GNAT to obtain this file.


File: gnat_ugn.info,  Node: Wide_Character Encodings,  Next: Wide_Wide_Character Encodings,  Prev: Other 8-Bit Codes,  Up: Foreign Language Representation

3.2.3 Wide_Character Encodings
------------------------------

GNAT allows wide character codes to appear in character and string
literals, and also optionally in identifiers, by means of the following
possible encoding schemes:

`Hex Coding'
     In this encoding, a wide character is represented by the following
     five character sequence:

         ESC a b c d

     where `a', `b', `c', `d' are the four hexadecimal characters
     (using uppercase letters) of the wide character code. For example,
     ESC A345 is used to represent the wide character with code
     `16#A345#'.  This scheme is compatible with use of the full
     Wide_Character set.

`Upper-Half Coding'
     The wide character with encoding `16#abcd#' where the upper bit is
     on (in other words, 'a' is in the range 8-F) is represented as two
     bytes, `16#ab#' and `16#cd#'. The second byte cannot be a format
     control character, but is not required to be in the upper half.
     This method can be also used for shift-JIS or EUC, where the
     internal coding matches the external coding.

`Shift JIS Coding'
     A wide character is represented by a two-character sequence,
     `16#ab#' and `16#cd#', with the restrictions described for
     upper-half encoding as described above. The internal character
     code is the corresponding JIS character according to the standard
     algorithm for Shift-JIS conversion. Only characters defined in the
     JIS code set table can be used with this encoding method.

`EUC Coding'
     A wide character is represented by a two-character sequence
     `16#ab#' and `16#cd#', with both characters being in the upper
     half. The internal character code is the corresponding JIS
     character according to the EUC encoding algorithm. Only characters
     defined in the JIS code set table can be used with this encoding
     method.

`UTF-8 Coding'
     A wide character is represented using UCS Transformation Format 8
     (UTF-8) as defined in Annex R of ISO 10646-1/Am.2. Depending on
     the character value, the representation is a one, two, or three
     byte sequence:

         16#0000#-16#007f#: 2#0`xxxxxxx`#
         16#0080#-16#07ff#: 2#110`xxxxx`# 2#10`xxxxxx`#
         16#0800#-16#ffff#: 2#1110`xxxx`# 2#10`xxxxxx`# 2#10`xxxxxx`#

     where the `xxx' bits correspond to the left-padded bits of the
     16-bit character value. Note that all lower half ASCII characters
     are represented as ASCII bytes and all upper half characters and
     other wide characters are represented as sequences of upper-half
     (The full UTF-8 scheme allows for encoding 31-bit characters as
     6-byte sequences, and in the following section on wide wide
     characters, the use of these sequences is documented).

`Brackets Coding'
     In this encoding, a wide character is represented by the following
     eight character sequence:

         [ " a b c d " ]

     where `a', `b', `c', `d' are the four hexadecimal characters
     (using uppercase letters) of the wide character code. For example,
     ['A345'] is used to represent the wide character with code
     `16#A345#'. It is also possible (though not required) to use the
     Brackets coding for upper half characters. For example, the code
     `16#A3#' can be represented as `['A3']'.

     This scheme is compatible with use of the full Wide_Character set,
     and is also the method used for wide character encoding in some
     standard ACATS (Ada Conformity Assessment Test Suite) test suite
     distributions.

     Note: Some of these coding schemes do not permit the full use of
     the Ada character set. For example, neither Shift JIS nor EUC
     allow the use of the upper half of the Latin-1 set.


File: gnat_ugn.info,  Node: Wide_Wide_Character Encodings,  Prev: Wide_Character Encodings,  Up: Foreign Language Representation

3.2.4 Wide_Wide_Character Encodings
-----------------------------------

GNAT allows wide wide character codes to appear in character and string
literals, and also optionally in identifiers, by means of the following
possible encoding schemes:

`UTF-8 Coding'
     A wide character is represented using UCS Transformation Format 8
     (UTF-8) as defined in Annex R of ISO 10646-1/Am.2. Depending on
     the character value, the representation of character codes with
     values greater than 16#FFFF# is a is a four, five, or six byte
     sequence:

         16#01_0000#-16#10_FFFF#:     11110xxx 10xxxxxx 10xxxxxx
                                      10xxxxxx
         16#0020_0000#-16#03FF_FFFF#: 111110xx 10xxxxxx 10xxxxxx
                                      10xxxxxx 10xxxxxx
         16#0400_0000#-16#7FFF_FFFF#: 1111110x 10xxxxxx 10xxxxxx
                                      10xxxxxx 10xxxxxx 10xxxxxx

     where the `xxx' bits correspond to the left-padded bits of the
     32-bit character value.

`Brackets Coding'
     In this encoding, a wide wide character is represented by the
     following ten or twelve byte character sequence:

         [ " a b c d e f " ]
         [ " a b c d e f g h " ]

     where `a-h' are the six or eight hexadecimal characters (using
     uppercase letters) of the wide wide character code. For example,
     ["1F4567"] is used to represent the wide wide character with code
     `16#001F_4567#'.

     This scheme is compatible with use of the full Wide_Wide_Character
     set, and is also the method used for wide wide character encoding
     in some standard ACATS (Ada Conformity Assessment Test Suite) test
     suite distributions.


File: gnat_ugn.info,  Node: File Naming Topics and Utilities,  Next: Configuration Pragmas,  Prev: Foreign Language Representation,  Up: The GNAT Compilation Model

3.3 File Naming Topics and Utilities
====================================

GNAT has a default file naming scheme and also provides the user with a
high degree of control over how the names and extensions of the source
files correspond to the Ada compilation units that they contain.

* Menu:

* File Naming Rules::
* Using Other File Names::
* Alternative File Naming Schemes::
* Handling Arbitrary File Naming Conventions with gnatname::
* File Name Krunching with gnatkr::
* Renaming Files with gnatchop::


File: gnat_ugn.info,  Node: File Naming Rules,  Next: Using Other File Names,  Up: File Naming Topics and Utilities

3.3.1 File Naming Rules
-----------------------

The default file name is determined by the name of the unit that the
file contains. The name is formed by taking the full expanded name of
the unit and replacing the separating dots with hyphens and using
lowercase for all letters.

An exception arises if the file name generated by the above rules starts
with one of the characters `a', `g', `i', or `s', and the second
character is a minus. In this case, the character tilde is used in place
of the minus. The reason for this special rule is to avoid clashes with
the standard names for child units of the packages System, Ada,
Interfaces, and GNAT, which use the prefixes `s-', `a-', `i-', and `g-',
respectively.

The file extension is `.ads' for a spec and `.adb' for a body. The
following table shows some examples of these rules.

      Source File                      Ada Compilation Unit
     `main.ads'                       Main (spec)
     `main.adb'                       Main (body)
     `arith_functions.ads'            Arith_Functions (package spec)
     `arith_functions.adb'            Arith_Functions (package body)
     `func-spec.ads'                  Func.Spec (child package spec)
     `func-spec.adb'                  Func.Spec (child package body)
     `main-sub.adb'                   Sub (subunit of Main)
     `a~bad.adb'                      A.Bad (child package body)


Following these rules can result in excessively long file names if
corresponding unit names are long (for example, if child units or
subunits are heavily nested). An option is available to shorten such
long file names (called file name 'krunching'). This may be
particularly useful when programs being developed with GNAT are to be
used on operating systems with limited file name lengths. *note Using
gnatkr: 56.

Of course, no file shortening algorithm can guarantee uniqueness over
all possible unit names; if file name krunching is used, it is your
responsibility to ensure no name clashes occur. Alternatively you can
specify the exact file names that you want used, as described in the
next section. Finally, if your Ada programs are migrating from a
compiler with a different naming convention, you can use the gnatchop
utility to produce source files that follow the GNAT naming conventions.
(For details see *note Renaming Files with gnatchop: 38.)

Note: in the case of Windows or Mac OS operating systems, case is not
significant. So for example on `Windows' if the canonical name is
`main-sub.adb', you can use the file name `Main-Sub.adb' instead.
However, case is significant for other operating systems, so for
example, if you want to use other than canonically cased file names on
a Unix system, you need to follow the procedures described in the next
section.


File: gnat_ugn.info,  Node: Using Other File Names,  Next: Alternative File Naming Schemes,  Prev: File Naming Rules,  Up: File Naming Topics and Utilities

3.3.2 Using Other File Names
----------------------------

In the previous section, we have described the default rules used by
GNAT to determine the file name in which a given unit resides. It is
often convenient to follow these default rules, and if you follow them,
the compiler knows without being explicitly told where to find all the
files it needs.

However, in some cases, particularly when a program is imported from
another Ada compiler environment, it may be more convenient for the
programmer to specify which file names contain which units. GNAT allows
arbitrary file names to be used by means of the Source_File_Name pragma.
The form of this pragma is as shown in the following examples:

    pragma Source_File_Name (My_Utilities.Stacks,
      Spec_File_Name => "myutilst_a.ada");
    pragma Source_File_name (My_Utilities.Stacks,
      Body_File_Name => "myutilst.ada");

As shown in this example, the first argument for the pragma is the unit
name (in this example a child unit). The second argument has the form
of a named association. The identifier indicates whether the file name
is for a spec or a body; the file name itself is given by a string
literal.

The source file name pragma is a configuration pragma, which means that
normally it will be placed in the `gnat.adc' file used to hold
configuration pragmas that apply to a complete compilation environment.
For more details on how the `gnat.adc' file is created and used see
*note Handling of Configuration Pragmas: 58.

GNAT allows completely arbitrary file names to be specified using the
source file name pragma. However, if the file name specified has an
extension other than `.ads' or `.adb' it is necessary to use a special
syntax when compiling the file. The name in this case must be preceded
by the special sequence `-x' followed by a space and the name of the
language, here `ada', as in:

    $ gcc -c -x ada peculiar_file_name.sim

`gnatmake' handles non-standard file names in the usual manner (the
non-standard file name for the main program is simply used as the
argument to gnatmake). Note that if the extension is also non-standard,
then it must be included in the `gnatmake' command, it may not be
omitted.


File: gnat_ugn.info,  Node: Alternative File Naming Schemes,  Next: Handling Arbitrary File Naming Conventions with gnatname,  Prev: Using Other File Names,  Up: File Naming Topics and Utilities

3.3.3 Alternative File Naming Schemes
-------------------------------------

The previous section described the use of the `Source_File_Name' pragma
to allow arbitrary names to be assigned to individual source files.
However, this approach requires one pragma for each file, and
especially in large systems can result in very long `gnat.adc' files,
and also create a maintenance problem.

GNAT also provides a facility for specifying systematic file naming
schemes other than the standard default naming scheme previously
described. An alternative scheme for naming is specified by the use of
`Source_File_Name' pragmas having the following format:

    pragma Source_File_Name (
       Spec_File_Name  => FILE_NAME_PATTERN
     [ , Casing          => CASING_SPEC]
     [ , Dot_Replacement => STRING_LITERAL ] );

    pragma Source_File_Name (
       Body_File_Name  => FILE_NAME_PATTERN
     [ , Casing          => CASING_SPEC ]
     [ , Dot_Replacement => STRING_LITERAL ] ) ;

    pragma Source_File_Name (
       Subunit_File_Name  => FILE_NAME_PATTERN
     [ , Casing          => CASING_SPEC ]
     [ , Dot_Replacement => STRING_LITERAL ] ) ;

    FILE_NAME_PATTERN ::= STRING_LITERAL
    CASING_SPEC ::= Lowercase | Uppercase | Mixedcase

The `FILE_NAME_PATTERN' string shows how the file name is constructed.
It contains a single asterisk character, and the unit name is
substituted systematically for this asterisk. The optional parameter
`Casing' indicates whether the unit name is to be all upper-case
letters, all lower-case letters, or mixed-case. If no `Casing'
parameter is used, then the default is all lower-case.

The optional `Dot_Replacement' string is used to replace any periods
that occur in subunit or child unit names. If no `Dot_Replacement'
argument is used then separating dots appear unchanged in the resulting
file name.  Although the above syntax indicates that the `Casing'
argument must appear before the `Dot_Replacement' argument, but it is
also permissible to write these arguments in the opposite order.

As indicated, it is possible to specify different naming schemes for
bodies, specs, and subunits. Quite often the rule for subunits is the
same as the rule for bodies, in which case, there is no need to give a
separate `Subunit_File_Name' rule, and in this case the
`Body_File_name' rule is used for subunits as well.

The separate rule for subunits can also be used to implement the rather
unusual case of a compilation environment (e.g., a single directory)
which contains a subunit and a child unit with the same unit name.
Although both units cannot appear in the same partition, the Ada
Reference Manual allows (but does not require) the possibility of the
two units coexisting in the same environment.

The file name translation works in the following steps:

   * If there is a specific `Source_File_Name' pragma for the given
     unit, then this is always used, and any general pattern rules are
     ignored.

   * If there is a pattern type `Source_File_Name' pragma that applies
     to the unit, then the resulting file name will be used if the file
     exists. If more than one pattern matches, the latest one will be
     tried first, and the first attempt resulting in a reference to a
     file that exists will be used.

   * If no pattern type `Source_File_Name' pragma that applies to the
     unit for which the corresponding file exists, then the standard
     GNAT default naming rules are used.

As an example of the use of this mechanism, consider a commonly used
scheme in which file names are all lower case, with separating periods
copied unchanged to the resulting file name, and specs end with
`.1.ada', and bodies end with `.2.ada'. GNAT will follow this scheme if
the following two pragmas appear:

    pragma Source_File_Name
      (Spec_File_Name => ".1.ada");
    pragma Source_File_Name
      (Body_File_Name => ".2.ada");

The default GNAT scheme is actually implemented by providing the
following default pragmas internally:

    pragma Source_File_Name
      (Spec_File_Name => ".ads", Dot_Replacement => "-");
    pragma Source_File_Name
      (Body_File_Name => ".adb", Dot_Replacement => "-");

Our final example implements a scheme typically used with one of the
Ada 83 compilers, where the separator character for subunits was '__'
(two underscores), specs were identified by adding `_.ADA', bodies by
adding `.ADA', and subunits by adding `.SEP'. All file names were upper
case. Child units were not present of course since this was an Ada 83
compiler, but it seems reasonable to extend this scheme to use the same
double underscore separator for child units.

    pragma Source_File_Name
      (Spec_File_Name => "_.ADA",
       Dot_Replacement => "__",
       Casing = Uppercase);
    pragma Source_File_Name
      (Body_File_Name => ".ADA",
       Dot_Replacement => "__",
       Casing = Uppercase);
    pragma Source_File_Name
      (Subunit_File_Name => ".SEP",
       Dot_Replacement => "__",
       Casing = Uppercase);


File: gnat_ugn.info,  Node: Handling Arbitrary File Naming Conventions with gnatname,  Next: File Name Krunching with gnatkr,  Prev: Alternative File Naming Schemes,  Up: File Naming Topics and Utilities

3.3.4 Handling Arbitrary File Naming Conventions with `gnatname'
----------------------------------------------------------------

* Menu:

* Arbitrary File Naming Conventions::
* Running gnatname::
* Switches for gnatname::
* Examples of gnatname Usage::


File: gnat_ugn.info,  Node: Arbitrary File Naming Conventions,  Next: Running gnatname,  Up: Handling Arbitrary File Naming Conventions with gnatname

3.3.4.1 Arbitrary File Naming Conventions
.........................................

The GNAT compiler must be able to know the source file name of a
compilation unit.  When using the standard GNAT default file naming
conventions (`.ads' for specs, `.adb' for bodies), the GNAT compiler
does not need additional information.

When the source file names do not follow the standard GNAT default file
naming conventions, the GNAT compiler must be given additional
information through a configuration pragmas file (*note Configuration
Pragmas: 16.)  or a project file.  When the non-standard file naming
conventions are well-defined, a small number of pragmas
`Source_File_Name' specifying a naming pattern (*note Alternative File
Naming Schemes: 5a.) may be sufficient. However, if the file naming
conventions are irregular or arbitrary, a number of pragma
`Source_File_Name' for individual compilation units must be defined.
To help maintain the correspondence between compilation unit names and
source file names within the compiler, GNAT provides a tool `gnatname'
to generate the required pragmas for a set of files.


File: gnat_ugn.info,  Node: Running gnatname,  Next: Switches for gnatname,  Prev: Arbitrary File Naming Conventions,  Up: Handling Arbitrary File Naming Conventions with gnatname

3.3.4.2 Running `gnatname'
..........................

The usual form of the `gnatname' command is:

    $ gnatname [`switches`] `naming_pattern` [`naming_patterns`]
        [--and [`switches`] `naming_pattern` [`naming_patterns`]]

All of the arguments are optional. If invoked without any argument,
`gnatname' will display its usage.

When used with at least one naming pattern, `gnatname' will attempt to
find all the compilation units in files that follow at least one of the
naming patterns. To find these compilation units, `gnatname' will use
the GNAT compiler in syntax-check-only mode on all regular files.

One or several Naming Patterns may be given as arguments to `gnatname'.
Each Naming Pattern is enclosed between double quotes (or single quotes
on Windows).  A Naming Pattern is a regular expression similar to the
wildcard patterns used in file names by the Unix shells or the DOS
prompt.

`gnatname' may be called with several sections of directories/patterns.
Sections are separated by switch `-and'. In each section, there must be
at least one pattern. If no directory is specified in a section, the
current directory (or the project directory is `-P' is used) is implied.
The options other that the directory switches and the patterns apply
globally even if they are in different sections.

Examples of Naming Patterns are:

    "*.[12].ada"
    "*.ad[sb]*"
    "body_*"    "spec_*"

For a more complete description of the syntax of Naming Patterns, see
the second kind of regular expressions described in `g-regexp.ads' (the
'Glob' regular expressions).

When invoked with no switch `-P', `gnatname' will create a
configuration pragmas file `gnat.adc' in the current working directory,
with pragmas `Source_File_Name' for each file that contains a valid Ada
unit.


File: gnat_ugn.info,  Node: Switches for gnatname,  Next: Examples of gnatname Usage,  Prev: Running gnatname,  Up: Handling Arbitrary File Naming Conventions with gnatname

3.3.4.3 Switches for `gnatname'
...............................

Switches for `gnatname' must precede any specified Naming Pattern.

You may specify any of the following switches to `gnatname':

`--version'
     Display Copyright and version, then exit disregarding all other
     options.

`--help'
     If `-version' was not used, display usage, then exit disregarding
     all other options.

`--subdirs=`dir''
     Real object, library or exec directories are subdirectories <dir>
     of the specified ones.

`--no-backup'
     Do not create a backup copy of an existing project file.

`--and'
     Start another section of directories/patterns.

`-c`filename''
     Create a configuration pragmas file `filename' (instead of the
     default `gnat.adc').  There may be zero, one or more space between
     `-c' and `filename'.  `filename' may include directory
     information. `filename' must be writable. There may be only one
     switch `-c'.  When a switch `-c' is specified, no switch `-P' may
     be specified (see below).

`-d`dir''
     Look for source files in directory `dir'. There may be zero, one
     or more spaces between `-d' and `dir'.  `dir' may end with `/**',
     that is it may be of the form `root_dir/**'. In this case, the
     directory `root_dir' and all of its subdirectories, recursively,
     have to be searched for sources.  When a switch `-d' is specified,
     the current working directory will not be searched for source
     files, unless it is explicitly specified with a `-d' or `-D'
     switch.  Several switches `-d' may be specified.  If `dir' is a
     relative path, it is relative to the directory of the
     configuration pragmas file specified with switch `-c', or to the
     directory of the project file specified with switch `-P' or, if
     neither switch `-c' nor switch `-P' are specified, it is relative
     to the current working directory. The directory specified with
     switch `-d' must exist and be readable.

`-D`filename''
     Look for source files in all directories listed in text file
     `filename'.  There may be zero, one or more spaces between `-D'
     and `filename'.  `filename' must be an existing, readable text
     file.  Each nonempty line in `filename' must be a directory.
     Specifying switch `-D' is equivalent to specifying as many
     switches `-d' as there are nonempty lines in `file'.

`-eL'
     Follow symbolic links when processing project files.

`-f`pattern''
     Foreign patterns. Using this switch, it is possible to add sources
     of languages other than Ada to the list of sources of a project
     file.  It is only useful if a -P switch is used.  For example,

         gnatname -Pprj -f"*.c" "*.ada"

     will look for Ada units in all files with the `.ada' extension,
     and will add to the list of file for project `prj.gpr' the C files
     with extension `.c'.

`-h'
     Output usage (help) information. The output is written to `stdout'.

`-P`proj''
     Create or update project file `proj'. There may be zero, one or
     more space between `-P' and `proj'. `proj' may include directory
     information. `proj' must be writable.  There may be only one
     switch `-P'.  When a switch `-P' is specified, no switch `-c' may
     be specified.  On all platforms, except on VMS, when `gnatname' is
     invoked for an existing project file <proj>.gpr, a backup copy of
     the project file is created in the project directory with file
     name <proj>.gpr.saved_x. 'x' is the first non negative number that
     makes this backup copy a new file.

`-v'
     Verbose mode. Output detailed explanation of behavior to `stdout'.
     This includes name of the file written, the name of the
     directories to search and, for each file in those directories
     whose name matches at least one of the Naming Patterns, an
     indication of whether the file contains a unit, and if so the name
     of the unit.

`-v -v'
     Very Verbose mode. In addition to the output produced in verbose
     mode, for each file in the searched directories whose name matches
     none of the Naming Patterns, an indication is given that there is
     no match.

`-x`pattern''
     Excluded patterns. Using this switch, it is possible to exclude
     some files that would match the name patterns. For example,

         gnatname -x "*_nt.ada" "*.ada"

     will look for Ada units in all files with the `.ada' extension,
     except those whose names end with `_nt.ada'.


File: gnat_ugn.info,  Node: Examples of gnatname Usage,  Prev: Switches for gnatname,  Up: Handling Arbitrary File Naming Conventions with gnatname

3.3.4.4 Examples of `gnatname' Usage
....................................

    $ gnatname -c /home/me/names.adc -d sources "[a-z]*.ada*"

In this example, the directory `/home/me' must already exist and be
writable. In addition, the directory `/home/me/sources' (specified by
`-d sources') must exist and be readable.

Note the optional spaces after `-c' and `-d'.

    $ gnatname -P/home/me/proj -x "*_nt_body.ada"
    -dsources -dsources/plus -Dcommon_dirs.txt "body_*" "spec_*"

Note that several switches `-d' may be used, even in conjunction with
one or several switches `-D'. Several Naming Patterns and one excluded
pattern are used in this example.


File: gnat_ugn.info,  Node: File Name Krunching with gnatkr,  Next: Renaming Files with gnatchop,  Prev: Handling Arbitrary File Naming Conventions with gnatname,  Up: File Naming Topics and Utilities

3.3.5 File Name Krunching with `gnatkr'
---------------------------------------

This chapter discusses the method used by the compiler to shorten the
default file names chosen for Ada units so that they do not exceed the
maximum length permitted. It also describes the `gnatkr' utility that
can be used to determine the result of applying this shortening.

* Menu:

* About gnatkr::
* Using gnatkr::
* Krunching Method::
* Examples of gnatkr Usage::


File: gnat_ugn.info,  Node: About gnatkr,  Next: Using gnatkr,  Up: File Name Krunching with gnatkr

3.3.5.1 About `gnatkr'
......................

The default file naming rule in GNAT is that the file name must be
derived from the unit name. The exact default rule is as follows:

   * Take the unit name and replace all dots by hyphens.

   * If such a replacement occurs in the second character position of a
     name, and the first character is `a', `g', `s', or `i', then
     replace the dot by the character `~' (tilde) instead of a minus.

     The reason for this exception is to avoid clashes with the
     standard names for children of System, Ada, Interfaces, and GNAT,
     which use the prefixes `s-', `a-', `i-', and `g-', respectively.

The `-gnatk`nn'' switch of the compiler activates a 'krunching' circuit
that limits file names to nn characters (where nn is a decimal integer).

The `gnatkr' utility can be used to determine the krunched name for a
given file, when krunched to a specified maximum length.


File: gnat_ugn.info,  Node: Using gnatkr,  Next: Krunching Method,  Prev: About gnatkr,  Up: File Name Krunching with gnatkr

3.3.5.2 Using `gnatkr'
......................

The `gnatkr' command has the form:

    $ gnatkr `name` [`length`]

`name' is the uncrunched file name, derived from the name of the unit
in the standard manner described in the previous section (i.e., in
particular all dots are replaced by hyphens). The file name may or may
not have an extension (defined as a suffix of the form period followed
by arbitrary characters other than period). If an extension is present
then it will be preserved in the output. For example, when krunching
`hellofile.ads' to eight characters, the result will be hellofil.ads.

Note: for compatibility with previous versions of `gnatkr' dots may
appear in the name instead of hyphens, but the last dot will always be
taken as the start of an extension. So if `gnatkr' is given an argument
such as `Hello.World.adb' it will be treated exactly as if the first
period had been a hyphen, and for example krunching to eight characters
gives the result `hellworl.adb'.

Note that the result is always all lower case.  Characters of the other
case are folded as required.

`length' represents the length of the krunched name. The default when
no argument is given is 8 characters. A length of zero stands for
unlimited, in other words do not chop except for system files where the
implied crunching length is always eight characters.

The output is the krunched name. The output has an extension only if the
original argument was a file name with an extension.


File: gnat_ugn.info,  Node: Krunching Method,  Next: Examples of gnatkr Usage,  Prev: Using gnatkr,  Up: File Name Krunching with gnatkr

3.3.5.3 Krunching Method
........................

The initial file name is determined by the name of the unit that the
file contains. The name is formed by taking the full expanded name of
the unit and replacing the separating dots with hyphens and using
lowercase for all letters, except that a hyphen in the second character
position is replaced by a tilde if the first character is `a', `i',
`g', or `s'.  The extension is `.ads' for a spec and `.adb' for a body.
Krunching does not affect the extension, but the file name is shortened
to the specified length by following these rules:

   * The name is divided into segments separated by hyphens, tildes or
     underscores and all hyphens, tildes, and underscores are
     eliminated. If this leaves the name short enough, we are done.

   * If the name is too long, the longest segment is located (left-most
     if there are two of equal length), and shortened by dropping its
     last character. This is repeated until the name is short enough.

     As an example, consider the krunching of
     `our-strings-wide_fixed.adb' to fit the name into 8 characters as
     required by some operating systems:

         our-strings-wide_fixed 22
         our strings wide fixed 19
         our string  wide fixed 18
         our strin   wide fixed 17
         our stri    wide fixed 16
         our stri    wide fixe  15
         our str     wide fixe  14
         our str     wid  fixe  13
         our str     wid  fix   12
         ou  str     wid  fix   11
         ou  st      wid  fix   10
         ou  st      wi   fix   9
         ou  st      wi   fi    8
         Final file name: oustwifi.adb

   * The file names for all predefined units are always krunched to
     eight characters. The krunching of these predefined units uses the
     following special prefix replacements:

     Prefix                    Replacement
     `ada-'                    `a-'
     `gnat-'                   `g-'
     `interfac es-'            `i-'
     `system-'                 `s-'

     These system files have a hyphen in the second character position.
     That is why normal user files replace such a character with a
     tilde, to avoid confusion with system file names.

     As an example of this special rule, consider
     `ada-strings-wide_fixed.adb', which gets krunched as follows:

         ada-strings-wide_fixed 22
         a-  strings wide fixed 18
         a-  string  wide fixed 17
         a-  strin   wide fixed 16
         a-  stri    wide fixed 15
         a-  stri    wide fixe  14
         a-  str     wide fixe  13
         a-  str     wid  fixe  12
         a-  str     wid  fix   11
         a-  st      wid  fix   10
         a-  st      wi   fix   9
         a-  st      wi   fi    8
         Final file name: a-stwifi.adb

Of course no file shortening algorithm can guarantee uniqueness over all
possible unit names, and if file name krunching is used then it is your
responsibility to ensure that no name clashes occur. The utility
program `gnatkr' is supplied for conveniently determining the krunched
name of a file.


File: gnat_ugn.info,  Node: Examples of gnatkr Usage,  Prev: Krunching Method,  Up: File Name Krunching with gnatkr

3.3.5.4 Examples of `gnatkr' Usage
..................................

    $ gnatkr very_long_unit_name.ads      --> velounna.ads
    $ gnatkr grandparent-parent-child.ads --> grparchi.ads
    $ gnatkr Grandparent.Parent.Child.ads --> grparchi.ads
    $ gnatkr grandparent-parent-child     --> grparchi
    $ gnatkr very_long_unit_name.ads/count=6 --> vlunna.ads
    $ gnatkr very_long_unit_name.ads/count=0 --> very_long_unit_name.ads


File: gnat_ugn.info,  Node: Renaming Files with gnatchop,  Prev: File Name Krunching with gnatkr,  Up: File Naming Topics and Utilities

3.3.6 Renaming Files with `gnatchop'
------------------------------------

This chapter discusses how to handle files with multiple units by using
the `gnatchop' utility. This utility is also useful in renaming files
to meet the standard GNAT default file naming conventions.

* Menu:

* Handling Files with Multiple Units::
* Operating gnatchop in Compilation Mode::
* Command Line for gnatchop::
* Switches for gnatchop::
* Examples of gnatchop Usage::


File: gnat_ugn.info,  Node: Handling Files with Multiple Units,  Next: Operating gnatchop in Compilation Mode,  Up: Renaming Files with gnatchop

3.3.6.1 Handling Files with Multiple Units
..........................................

The basic compilation model of GNAT requires that a file submitted to
the compiler have only one unit and there be a strict correspondence
between the file name and the unit name.

The `gnatchop' utility allows both of these rules to be relaxed,
allowing GNAT to process files which contain multiple compilation units
and files with arbitrary file names. `gnatchop' reads the specified
file and generates one or more output files, containing one unit per
file. The unit and the file name correspond, as required by GNAT.

If you want to permanently restructure a set of 'foreign' files so that
they match the GNAT rules, and do the remaining development using the
GNAT structure, you can simply use `gnatchop' once, generate the new
set of files and work with them from that point on.

Alternatively, if you want to keep your files in the 'foreign' format,
perhaps to maintain compatibility with some other Ada compilation
system, you can set up a procedure where you use `gnatchop' each time
you compile, regarding the source files that it writes as temporary
files that you throw away.

Note that if your file containing multiple units starts with a byte
order mark (BOM) specifying UTF-8 encoding, then the files generated by
gnatchop will each start with a copy of this BOM, meaning that they can
be compiled automatically in UTF-8 mode without needing to specify an
explicit encoding.


File: gnat_ugn.info,  Node: Operating gnatchop in Compilation Mode,  Next: Command Line for gnatchop,  Prev: Handling Files with Multiple Units,  Up: Renaming Files with gnatchop

3.3.6.2 Operating gnatchop in Compilation Mode
..............................................

The basic function of `gnatchop' is to take a file with multiple units
and split it into separate files. The boundary between files is
reasonably clear, except for the issue of comments and pragmas. In
default mode, the rule is that any pragmas between units belong to the
previous unit, except that configuration pragmas always belong to the
following unit. Any comments belong to the following unit. These rules
almost always result in the right choice of the split point without
needing to mark it explicitly and most users will find this default to
be what they want. In this default mode it is incorrect to submit a
file containing only configuration pragmas, or one that ends in
configuration pragmas, to `gnatchop'.

However, using a special option to activate 'compilation mode',
`gnatchop' can perform another function, which is to provide exactly
the semantics required by the RM for handling of configuration pragmas
in a compilation.  In the absence of configuration pragmas (at the main
file level), this option has no effect, but it causes such
configuration pragmas to be handled in a quite different manner.

First, in compilation mode, if `gnatchop' is given a file that consists
of only configuration pragmas, then this file is appended to the
`gnat.adc' file in the current directory. This behavior provides the
required behavior described in the RM for the actions to be taken on
submitting such a file to the compiler, namely that these pragmas
should apply to all subsequent compilations in the same compilation
environment. Using GNAT, the current directory, possibly containing a
`gnat.adc' file is the representation of a compilation environment. For
more information on the `gnat.adc' file, see *note Handling of
Configuration Pragmas: 58.

Second, in compilation mode, if `gnatchop' is given a file that starts
with configuration pragmas, and contains one or more units, then these
configuration pragmas are prepended to each of the chopped files. This
behavior provides the required behavior described in the RM for the
actions to be taken on compiling such a file, namely that the pragmas
apply to all units in the compilation, but not to subsequently compiled
units.

Finally, if configuration pragmas appear between units, they are
appended to the previous unit. This results in the previous unit being
illegal, since the compiler does not accept configuration pragmas that
follow a unit. This provides the required RM behavior that forbids
configuration pragmas other than those preceding the first compilation
unit of a compilation.

For most purposes, `gnatchop' will be used in default mode. The
compilation mode described above is used only if you need exactly
accurate behavior with respect to compilations, and you have files that
contain multiple units and configuration pragmas. In this circumstance
the use of `gnatchop' with the compilation mode switch provides the
required behavior, and is for example the mode in which GNAT processes
the ACVC tests.


File: gnat_ugn.info,  Node: Command Line for gnatchop,  Next: Switches for gnatchop,  Prev: Operating gnatchop in Compilation Mode,  Up: Renaming Files with gnatchop

3.3.6.3 Command Line for `gnatchop'
...................................

The `gnatchop' command has the form:

    $ gnatchop switches file_name [file_name ...]
          [directory]

The only required argument is the file name of the file to be chopped.
There are no restrictions on the form of this file name. The file itself
contains one or more Ada units, in normal GNAT format, concatenated
together. As shown, more than one file may be presented to be chopped.

When run in default mode, `gnatchop' generates one output file in the
current directory for each unit in each of the files.

`directory', if specified, gives the name of the directory to which the
output files will be written. If it is not specified, all files are
written to the current directory.

For example, given a file called `hellofiles' containing

    procedure Hello;

    with Ada.Text_IO; use Ada.Text_IO;
    procedure Hello is
    begin
       Put_Line ("Hello");
    end Hello;

the command

    $ gnatchop hellofiles

generates two files in the current directory, one called `hello.ads'
containing the single line that is the procedure spec, and the other
called `hello.adb' containing the remaining text. The original file is
not affected. The generated files can be compiled in the normal manner.

When gnatchop is invoked on a file that is empty or that contains only
empty lines and/or comments, gnatchop will not fail, but will not
produce any new sources.

For example, given a file called `toto.txt' containing

    --  Just a comment

the command

    $ gnatchop toto.txt

will not produce any new file and will result in the following warnings:

    toto.txt:1:01: warning: empty file, contains no compilation units
    no compilation units found
    no source files written


File: gnat_ugn.info,  Node: Switches for gnatchop,  Next: Examples of gnatchop Usage,  Prev: Command Line for gnatchop,  Up: Renaming Files with gnatchop

3.3.6.4 Switches for `gnatchop'
...............................

`gnatchop' recognizes the following switches:

`--version'
     Display Copyright and version, then exit disregarding all other
     options.

`--help'
     If `-version' was not used, display usage, then exit disregarding
     all other options.

`-c'
     Causes `gnatchop' to operate in compilation mode, in which
     configuration pragmas are handled according to strict RM rules. See
     previous section for a full description of this mode.

`-gnat`xxx''
     This passes the given `-gnat`xxx*` switch to `gnat` which is used
     to parse the given file. Not all `xxx` options make sense, but for
     example, the use of *-gnati2' allows `gnatchop' to process a
     source file that uses Latin-2 coding for identifiers.

`-h'
     Causes `gnatchop' to generate a brief help summary to the standard
     output file showing usage information.

`-k`mm''
     Limit generated file names to the specified number `mm' of
     characters.  This is useful if the resulting set of files is
     required to be interoperable with systems which limit the length
     of file names.  No space is allowed between the `-k' and the
     numeric value. The numeric value may be omitted in which case a
     default of `-k8', suitable for use with DOS-like file systems, is
     used. If no `-k' switch is present then there is no limit on the
     length of file names.

`-p'
     Causes the file modification time stamp of the input file to be
     preserved and used for the time stamp of the output file(s). This
     may be useful for preserving coherency of time stamps in an
     environment where `gnatchop' is used as part of a standard build
     process.

`-q'
     Causes output of informational messages indicating the set of
     generated files to be suppressed. Warnings and error messages are
     unaffected.

`-r'
     Generate `Source_Reference' pragmas. Use this switch if the output
     files are regarded as temporary and development is to be done in
     terms of the original unchopped file. This switch causes
     `Source_Reference' pragmas to be inserted into each of the
     generated files to refers back to the original file name and line
     number.  The result is that all error messages refer back to the
     original unchopped file.  In addition, the debugging information
     placed into the object file (when the `-g' switch of `gcc' or
     `gnatmake' is specified) also refers back to this original file so
     that tools like profilers and debuggers will give information in
     terms of the original unchopped file.

     If the original file to be chopped itself contains a
     `Source_Reference' pragma referencing a third file, then gnatchop
     respects this pragma, and the generated `Source_Reference' pragmas
     in the chopped file refer to the original file, with appropriate
     line numbers. This is particularly useful when `gnatchop' is used
     in conjunction with `gnatprep' to compile files that contain
     preprocessing statements and multiple units.

`-v'
     Causes `gnatchop' to operate in verbose mode. The version number
     and copyright notice are output, as well as exact copies of the
     gnat1 commands spawned to obtain the chop control information.

`-w'
     Overwrite existing file names. Normally `gnatchop' regards it as a
     fatal error if there is already a file with the same name as a
     file it would otherwise output, in other words if the files to be
     chopped contain duplicated units. This switch bypasses this check,
     and causes all but the last instance of such duplicated units to
     be skipped.

`--GCC=`xxxx''
     Specify the path of the GNAT parser to be used. When this switch
     is used, no attempt is made to add the prefix to the GNAT parser
     executable.


File: gnat_ugn.info,  Node: Examples of gnatchop Usage,  Prev: Switches for gnatchop,  Up: Renaming Files with gnatchop

3.3.6.5 Examples of `gnatchop' Usage
....................................

    $ gnatchop -w hello_s.ada prerelease/files

Chops the source file `hello_s.ada'. The output files will be placed in
the directory `prerelease/files', overwriting any files with matching
names in that directory (no files in the current directory are
modified).

    $ gnatchop archive

Chops the source file `archive' into the current directory. One useful
application of `gnatchop' is in sending sets of sources around, for
example in email messages. The required sources are simply concatenated
(for example, using a Unix `cat' command), and then `gnatchop' is used
at the other end to reconstitute the original file names.

    $ gnatchop file1 file2 file3 direc

Chops all units in files `file1', `file2', `file3', placing the
resulting files in the directory `direc'. Note that if any units occur
more than once anywhere within this set of files, an error message is
generated, and no files are written. To override this check, use the
`-w' switch, in which case the last occurrence in the last file will be
the one that is output, and earlier duplicate occurrences for a given
unit will be skipped.


File: gnat_ugn.info,  Node: Configuration Pragmas,  Next: Generating Object Files,  Prev: File Naming Topics and Utilities,  Up: The GNAT Compilation Model

3.4 Configuration Pragmas
=========================

Configuration pragmas include those pragmas described as such in the
Ada Reference Manual, as well as implementation-dependent pragmas that
are configuration pragmas.  See the `Implementation_Defined_Pragmas'
chapter in the `GNAT_Reference_Manual' for details on these additional
GNAT-specific configuration pragmas.  Most notably, the pragma
`Source_File_Name', which allows specifying non-default names for
source files, is a configuration pragma. The following is a complete
list of configuration pragmas recognized by GNAT:

    Ada_83
    Ada_95
    Ada_05
    Ada_2005
    Ada_12
    Ada_2012
    Allow_Integer_Address
    Annotate
    Assertion_Policy
    Assume_No_Invalid_Values
    C_Pass_By_Copy
    Check_Name
    Check_Policy
    Compile_Time_Error
    Compile_Time_Warning
    Compiler_Unit
    Component_Alignment
    Convention_Identifier
    Debug_Policy
    Detect_Blocking
    Default_Storage_Pool
    Discard_Names
    Elaboration_Checks
    Eliminate
    Extend_System
    Extensions_Allowed
    External_Name_Casing
    Fast_Math
    Favor_Top_Level
    Float_Representation
    Implicit_Packing
    Initialize_Scalars
    Interrupt_State
    License
    Locking_Policy
    Long_Float
    No_Run_Time
    No_Strict_Aliasing
    Normalize_Scalars
    Optimize_Alignment
    Persistent_BSS
    Polling
    Priority_Specific_Dispatching
    Profile
    Profile_Warnings
    Propagate_Exceptions
    Queuing_Policy
    Ravenscar
    Restricted_Run_Time
    Restrictions
    Restrictions_Warnings
    Reviewable
    Short_Circuit_And_Or
    Source_File_Name
    Source_File_Name_Project
    SPARK_Mode
    Style_Checks
    Suppress
    Suppress_Exception_Locations
    Task_Dispatching_Policy
    Universal_Data
    Unsuppress
    Use_VADS_Size
    Validity_Checks
    Warnings
    Wide_Character_Encoding

* Menu:

* Handling of Configuration Pragmas::
* The Configuration Pragmas Files::


File: gnat_ugn.info,  Node: Handling of Configuration Pragmas,  Next: The Configuration Pragmas Files,  Up: Configuration Pragmas

3.4.1 Handling of Configuration Pragmas
---------------------------------------

Configuration pragmas may either appear at the start of a compilation
unit, or they can appear in a configuration pragma file to apply to all
compilations performed in a given compilation environment.

GNAT also provides the `gnatchop' utility to provide an automatic way
to handle configuration pragmas following the semantics for
compilations (that is, files with multiple units), described in the RM.
See *note Operating gnatchop in Compilation Mode: 71. for details.
However, for most purposes, it will be more convenient to edit the
`gnat.adc' file that contains configuration pragmas directly, as
described in the following section.

In the case of `Restrictions' pragmas appearing as configuration
pragmas in individual compilation units, the exact handling depends on
the type of restriction.

Restrictions that require partition-wide consistency (like
`No_Tasking') are recognized wherever they appear and can be freely
inherited, e.g. from a `with'ed unit to the `with'ing unit. This makes
sense since the binder will in any case insist on seeing consistent
use, so any unit not conforming to any restrictions that are anywhere
in the partition will be rejected, and you might as well find that out
at compile time rather than at bind time.

For restrictions that do not require partition-wide consistency, e.g.
SPARK or No_Implementation_Attributes, in general the restriction
applies only to the unit in which the pragma appears, and not to any
other units.

The exception is No_Elaboration_Code which always applies to the entire
object file from a compilation, i.e. to the body, spec, and all
subunits.  This restriction can be specified in a configuration pragma
file, or it can be on the body and/or the spec (in eithe case it
applies to all the relevant units). It can appear on a subunit only if
it has previously appeared in the body of spec.


File: gnat_ugn.info,  Node: The Configuration Pragmas Files,  Prev: Handling of Configuration Pragmas,  Up: Configuration Pragmas

3.4.2 The Configuration Pragmas Files
-------------------------------------

In GNAT a compilation environment is defined by the current directory
at the time that a compile command is given. This current directory is
searched for a file whose name is `gnat.adc'. If this file is present,
it is expected to contain one or more configuration pragmas that will
be applied to the current compilation.  However, if the switch `-gnatA'
is used, `gnat.adc' is not considered. When taken into account,
`gnat.adc' is added to the dependencies, so that if `gnat.adc' is
modified later, an invocation of `gnatmake' will recompile the source.

Configuration pragmas may be entered into the `gnat.adc' file either by
running `gnatchop' on a source file that consists only of configuration
pragmas, or more conveniently by direct editing of the `gnat.adc' file,
which is a standard format source file.

Besides `gnat.adc', additional files containing configuration pragmas
may be applied to the current compilation using the switch
`-gnatec=`path'' where `path' must designate an existing file that
contains only configuration pragmas. These configuration pragmas are in
addition to those found in `gnat.adc' (provided `gnat.adc' is present
and switch `-gnatA' is not used).

It is allowable to specify several switches `-gnatec=', all of which
will be taken into account.

Files containing configuration pragmas specified with switches
`-gnatec=' are added to the dependencies, unless they are temporary
files. A file is considered temporary if its name ends in `.tmp' or
`.TMP'. Certain tools follow this naming convention because they pass
information to `gcc' via temporary files that are immediately deleted;
it doesn't make sense to depend on a file that no longer exists. Such
tools include `gprbuild', `gnatmake', and `gnatcheck'.

If you are using project file, a separate mechanism is provided using
project attributes, see *note Specifying Configuration Pragmas: 7d. for
more details.


File: gnat_ugn.info,  Node: Generating Object Files,  Next: Source Dependencies,  Prev: Configuration Pragmas,  Up: The GNAT Compilation Model

3.5 Generating Object Files
===========================

An Ada program consists of a set of source files, and the first step in
compiling the program is to generate the corresponding object files.
These are generated by compiling a subset of these source files.  The
files you need to compile are the following:

   * If a package spec has no body, compile the package spec to produce
     the object file for the package.

   * If a package has both a spec and a body, compile the body to
     produce the object file for the package. The source file for the
     package spec need not be compiled in this case because there is
     only one object file, which contains the code for both the spec
     and body of the package.

   * For a subprogram, compile the subprogram body to produce the
     object file for the subprogram. The spec, if one is present, is as
     usual in a separate file, and need not be compiled.

   * In the case of subunits, only compile the parent unit. A single
     object file is generated for the entire subunit tree, which
     includes all the subunits.

   * Compile child units independently of their parent units (though,
     of course, the spec of all the ancestor unit must be present in
     order to compile a child unit).

   * Compile generic units in the same manner as any other units. The
     object files in this case are small dummy files that contain at
     most the flag used for elaboration checking. This is because GNAT
     always handles generic instantiation by means of macro expansion.
     However, it is still necessary to compile generic units, for
     dependency checking and elaboration purposes.

The preceding rules describe the set of files that must be compiled to
generate the object files for a program. Each object file has the same
name as the corresponding source file, except that the extension is
`.o' as usual.

You may wish to compile other files for the purpose of checking their
syntactic and semantic correctness. For example, in the case where a
package has a separate spec and body, you would not normally compile the
spec. However, it is convenient in practice to compile the spec to make
sure it is error-free before compiling clients of this spec, because
such compilations will fail if there is an error in the spec.

GNAT provides an option for compiling such files purely for the
purposes of checking correctness; such compilations are not required as
part of the process of building a program. To compile a file in this
checking mode, use the `-gnatc' switch.


File: gnat_ugn.info,  Node: Source Dependencies,  Next: The Ada Library Information Files,  Prev: Generating Object Files,  Up: The GNAT Compilation Model

3.6 Source Dependencies
=======================

A given object file clearly depends on the source file which is compiled
to produce it. Here we are using "depends" in the sense of a typical
`make' utility; in other words, an object file depends on a source file
if changes to the source file require the object file to be recompiled.
In addition to this basic dependency, a given object may depend on
additional source files as follows:

   * If a file being compiled `with's a unit `X', the object file
     depends on the file containing the spec of unit `X'. This includes
     files that are `with'ed implicitly either because they are parents
     of `with'ed child units or they are run-time units required by the
     language constructs used in a particular unit.

   * If a file being compiled instantiates a library level generic
     unit, the object file depends on both the spec and body files for
     this generic unit.

   * If a file being compiled instantiates a generic unit defined
     within a package, the object file depends on the body file for the
     package as well as the spec file.

   * If a file being compiled contains a call to a subprogram for which
     pragma `Inline' applies and inlining is activated with the
     `-gnatn' switch, the object file depends on the file containing the
     body of this subprogram as well as on the file containing the
     spec. Note that for inlining to actually occur as a result of the
     use of this switch, it is necessary to compile in optimizing mode.

     The use of `-gnatN' activates  inlining optimization that is
     performed by the front end of the compiler. This inlining does not
     require that the code generation be optimized. Like `-gnatn', the
     use of this switch generates additional dependencies.

     When using a gcc-based back end (in practice this means using any
     version of GNAT other than for the JVM, .NET or GNAAMP platforms),
     then the use of `-gnatN' is deprecated, and the use of `-gnatn' is
     preferred.  Historically front end inlining was more extensive
     than the gcc back end inlining, but that is no longer the case.

   * If an object file `O' depends on the proper body of a subunit
     through inlining or instantiation, it depends on the parent unit
     of the subunit.  This means that any modification of the parent
     unit or one of its subunits affects the compilation of `O'.

   * The object file for a parent unit depends on all its subunit body
     files.

   * The previous two rules meant that for purposes of computing
     dependencies and recompilation, a body and all its subunits are
     treated as an indivisible whole.

     These rules are applied transitively: if unit `A' `with's unit
     `B', whose elaboration calls an inlined procedure in package `C',
     the object file for unit `A' will depend on the body of `C', in
     file `c.adb'.

     The set of dependent files described by these rules includes all
     the files on which the unit is semantically dependent, as dictated
     by the Ada language standard. However, it is a superset of what the
     standard describes, because it includes generic, inline, and
     subunit dependencies.

     An object file must be recreated by recompiling the corresponding
     source file if any of the source files on which it depends are
     modified. For example, if the `make' utility is used to control
     compilation, the rule for an Ada object file must mention all the
     source files on which the object file depends, according to the
     above definition.  The determination of the necessary
     recompilations is done automatically when one uses `gnatmake'.


File: gnat_ugn.info,  Node: The Ada Library Information Files,  Next: Binding an Ada Program,  Prev: Source Dependencies,  Up: The GNAT Compilation Model

3.7 The Ada Library Information Files
=====================================

Each compilation actually generates two output files. The first of these
is the normal object file that has a `.o' extension. The second is a
text file containing full dependency information. It has the same name
as the source file, but an `.ali' extension.  This file is known as the
Ada Library Information (`ALI') file.  The following information is
contained in the `ALI' file.

   * Version information (indicates which version of GNAT was used to
     compile the unit(s) in question)

   * Main program information (including priority and time slice
     settings, as well as the wide character encoding used during
     compilation).

   * List of arguments used in the `gcc' command for the compilation

   * Attributes of the unit, including configuration pragmas used, an
     indication of whether the compilation was successful, exception
     model used etc.

   * A list of relevant restrictions applying to the unit (used for
     consistency) checking.

   * Categorization information (e.g., use of pragma `Pure').

   * Information on all `with'ed units, including presence of
     Elaborate` or `Elaborate_All' pragmas.

   * Information from any `Linker_Options' pragmas used in the unit

   * Information on the use of `Body_Version' or `Version' attributes
     in the unit.

   * Dependency information. This is a list of files, together with
     time stamp and checksum information. These are files on which the
     unit depends in the sense that recompilation is required if any of
     these units are modified.

   * Cross-reference data. Contains information on all entities
     referenced in the unit. Used by tools like `gnatxref' and
     `gnatfind' to provide cross-reference information.

For a full detailed description of the format of the `ALI' file, see
the source of the body of unit `Lib.Writ', contained in file
`lib-writ.adb' in the GNAT compiler sources.


File: gnat_ugn.info,  Node: Binding an Ada Program,  Next: GNAT and Libraries,  Prev: The Ada Library Information Files,  Up: The GNAT Compilation Model

3.8 Binding an Ada Program
==========================

When using languages such as C and C++, once the source files have been
compiled the only remaining step in building an executable program is
linking the object modules together. This means that it is possible to
link an inconsistent version of a program, in which two units have
included different versions of the same header.

The rules of Ada do not permit such an inconsistent program to be built.
For example, if two clients have different versions of the same package,
it is illegal to build a program containing these two clients.  These
rules are enforced by the GNAT binder, which also determines an
elaboration order consistent with the Ada rules.

The GNAT binder is run after all the object files for a program have
been created. It is given the name of the main program unit, and from
this it determines the set of units required by the program, by reading
the corresponding ALI files. It generates error messages if the program
is inconsistent or if no valid order of elaboration exists.

If no errors are detected, the binder produces a main program, in Ada by
default, that contains calls to the elaboration procedures of those
compilation unit that require them, followed by a call to the main
program. This Ada program is compiled to generate the object file for
the main program. The name of the Ada file is `b~xxx'.adb` (with the
corresponding spec `b~xxx'.ads`) where `xxx' is the name of the main
program unit.

Finally, the linker is used to build the resulting executable program,
using the object from the main program from the bind step as well as the
object files for the Ada units of the program.


File: gnat_ugn.info,  Node: GNAT and Libraries,  Next: Conditional Compilation,  Prev: Binding an Ada Program,  Up: The GNAT Compilation Model

3.9 GNAT and Libraries
======================

This chapter describes how to build and use libraries with GNAT, and
also shows how to recompile the GNAT run-time library. You should be
familiar with the Project Manager facility (*note GNAT Project Manager:
b.) before reading this chapter.

* Menu:

* Introduction to Libraries in GNAT::
* General Ada Libraries::
* Stand-alone Ada Libraries::
* Rebuilding the GNAT Run-Time Library::


File: gnat_ugn.info,  Node: Introduction to Libraries in GNAT,  Next: General Ada Libraries,  Up: GNAT and Libraries

3.9.1 Introduction to Libraries in GNAT
---------------------------------------

A library is, conceptually, a collection of objects which does not have
its own main thread of execution, but rather provides certain services
to the applications that use it. A library can be either statically
linked with the application, in which case its code is directly
included in the application, or, on platforms that support it, be
dynamically linked, in which case its code is shared by all
applications making use of this library.

GNAT supports both types of libraries.  In the static case, the
compiled code can be provided in different ways. The simplest approach
is to provide directly the set of objects resulting from compilation of
the library source files. Alternatively, you can group the objects into
an archive using whatever commands are provided by the operating
system. For the latter case, the objects are grouped into a shared
library.

In the GNAT environment, a library has three types of components:

   * Source files,

   * `ALI' files (see *note The Ada Library Information Files: 44.), and

   * Object files, an archive or a shared library.

A GNAT library may expose all its source files, which is useful for
documentation purposes. Alternatively, it may expose only the units
needed by an external user to make use of the library. That is to say,
the specs reflecting the library services along with all the units
needed to compile those specs, which can include generic bodies or any
body implementing an inlined routine. In the case of `stand-alone
libraries' those exposed units are called `interface units' (*note
Stand-alone Ada Libraries: 85.).

All compilation units comprising an application, including those in a
library, need to be elaborated in an order partially defined by Ada's
semantics. GNAT computes the elaboration order from the `ALI' files and
this is why they constitute a mandatory part of GNAT libraries.
`Stand-alone libraries' are the exception to this rule because a
specific library elaboration routine is produced independently of the
application(s) using the library.


File: gnat_ugn.info,  Node: General Ada Libraries,  Next: Stand-alone Ada Libraries,  Prev: Introduction to Libraries in GNAT,  Up: GNAT and Libraries

3.9.2 General Ada Libraries
---------------------------

* Menu:

* Building a library::
* Installing a library::
* Using a library::


File: gnat_ugn.info,  Node: Building a library,  Next: Installing a library,  Up: General Ada Libraries

3.9.2.1 Building a library
..........................

The easiest way to build a library is to use the Project Manager, which
supports a special type of project called a `Library Project' (see
*note Library Projects: 8a.).

A project is considered a library project, when two project-level
attributes are defined in it: `Library_Name' and `Library_Dir'. In
order to control different aspects of library configuration, additional
optional project-level attributes can be specified:

   *
    `Library_Kind'
          This attribute controls whether the library is to be static
          or dynamic

   *
    `Library_Version'
          This attribute specifies the library version; this value is
          used during dynamic linking of shared libraries to determine
          if the currently installed versions of the binaries are
          compatible.

   * `Library_Options'

   *
    `Library_GCC'
          These attributes specify additional low-level options to be
          used during library generation, and redefine the actual
          application used to generate library.

The GNAT Project Manager takes full care of the library maintenance
task, including recompilation of the source files for which objects do
not exist or are not up to date, assembly of the library archive, and
installation of the library (i.e., copying associated source, object
and `ALI' files to the specified location).

Here is a simple library project file:

    project My_Lib is
      for Source_Dirs use ("src1", "src2");
      for Object_Dir use "obj";
      for Library_Name use "mylib";
      for Library_Dir use "lib";
      for Library_Kind use "dynamic";
    end My_lib;

and the compilation command to build and install the library:

    $ gnatmake -Pmy_lib

It is not entirely trivial to perform manually all the steps required to
produce a library. We recommend that you use the GNAT Project Manager
for this task. In special cases where this is not desired, the necessary
steps are discussed below.

There are various possibilities for compiling the units that make up the
library: for example with a Makefile (*note Using the GNU make Utility:
21.) or with a conventional script. For simple libraries, it is also
possible to create a dummy main program which depends upon all the
packages that comprise the interface of the library. This dummy main
program can then be given to `gnatmake', which will ensure that all
necessary objects are built.

After this task is accomplished, you should follow the standard
procedure of the underlying operating system to produce the static or
shared library.

Here is an example of such a dummy program:

    with My_Lib.Service1;
    with My_Lib.Service2;
    with My_Lib.Service3;
    procedure My_Lib_Dummy is
    begin
       null;
    end;

Here are the generic commands that will build an archive or a shared
library.

    # compiling the library
    $ gnatmake -c my_lib_dummy.adb

    # we don't need the dummy object itself
    $ rm my_lib_dummy.o my_lib_dummy.ali

    # create an archive with the remaining objects
    $ ar rc libmy_lib.a *.o
    # some systems may require "ranlib" to be run as well

    # or create a shared library
    $ gcc -shared -o libmy_lib.so *.o
    # some systems may require the code to have been compiled with -fPIC

    # remove the object files that are now in the library
    $ rm *.o

    # Make the ALI files read-only so that gnatmake will not try to
    # regenerate the objects that are in the library
    $ chmod -w *.ali

Please note that the library must have a name of the form `lib`xxx'.a'
or `lib`xxx'.so' (or `lib`xxx'.dll' on Windows) in order to be accessed
by the directive `-l`xxx'' at link time.


File: gnat_ugn.info,  Node: Installing a library,  Next: Using a library,  Prev: Building a library,  Up: General Ada Libraries

3.9.2.2 Installing a library
............................

If you use project files, library installation is part of the library
build process (*note Installing a library with project files: 8d.).

When project files are not an option, it is also possible, but not
recommended, to install the library so that the sources needed to use
the library are on the Ada source path and the ALI files & libraries be
on the Ada Object path (see *note Search Paths and the Run-Time Library
(RTL): 8e. Alternatively, the system administrator can place
general-purpose libraries in the default compiler paths, by specifying
the libraries' location in the configuration files `ada_source_path'
and `ada_object_path'. These configuration files must be located in the
GNAT installation tree at the same place as the gcc spec file. The
location of the gcc spec file can be determined as follows:

    $ gcc -v

The configuration files mentioned above have a simple format: each line
must contain one unique directory name.  Those names are added to the
corresponding path in their order of appearance in the file. The names
can be either absolute or relative; in the latter case, they are
relative to where theses files are located.

The files `ada_source_path' and `ada_object_path' might not be present
in a GNAT installation, in which case, GNAT will look for its run-time
library in the directories `adainclude' (for the sources) and `adalib'
(for the objects and `ALI' files). When the files exist, the compiler
does not look in `adainclude' and `adalib', and thus the
`ada_source_path' file must contain the location for the GNAT run-time
sources (which can simply be `adainclude'). In the same way, the
`ada_object_path' file must contain the location for the GNAT run-time
objects (which can simply be `adalib').

You can also specify a new default path to the run-time library at
compilation time with the switch `-RTS=rts-path'. You can thus choose /
change the run-time library you want your program to be compiled with.
This switch is recognized by `gcc', `gnatmake', `gnatbind', `gnatls',
`gnatfind' and `gnatxref'.

It is possible to install a library before or after the standard GNAT
library, by reordering the lines in the configuration files. In
general, a library must be installed before the GNAT library if it
redefines any part of it.


File: gnat_ugn.info,  Node: Using a library,  Prev: Installing a library,  Up: General Ada Libraries

3.9.2.3 Using a library
.......................

Once again, the project facility greatly simplifies the use of
libraries. In this context, using a library is just a matter of adding a
`with' clause in the user project. For instance, to make use of the
library `My_Lib' shown in examples in earlier sections, you can write:

    with "my_lib";
    project My_Proj is
      ...
    end My_Proj;

Even if you have a third-party, non-Ada library, you can still use
GNAT's Project Manager facility to provide a wrapper for it. For
example, the following project, when `with'ed by your main project,
will link with the third-party library `liba.a':

    project Liba is
       for Externally_Built use "true";
       for Source_Files use ();
       for Library_Dir use "lib";
       for Library_Name use "a";
       for Library_Kind use "static";
    end Liba;

This is an alternative to the use of `pragma Linker_Options'. It is
especially interesting in the context of systems with several
interdependent static libraries where finding a proper linker order is
not easy and best be left to the tools having visibility over project
dependence information.

In order to use an Ada library manually, you need to make sure that this
library is on both your source and object path (see *note Search Paths
and the Run-Time Library (RTL): 8e.  and *note Search Paths for
gnatbind: 91.). Furthermore, when the objects are grouped in an archive
or a shared library, you need to specify the desired library at link
time.

For example, you can use the library `mylib' installed in
`/dir/my_lib_src' and `/dir/my_lib_obj' with the following commands:

    $ gnatmake -aI/dir/my_lib_src -aO/dir/my_lib_obj my_appl \\
      -largs -lmy_lib

This can be expressed more simply:

    $ gnatmake my_appl

when the following conditions are met:

   * `/dir/my_lib_src' has been added by the user to the environment
     variable `ADA_INCLUDE_PATH', or by the administrator to the file
     `ada_source_path'

   * `/dir/my_lib_obj' has been added by the user to the environment
     variable `ADA_OBJECTS_PATH', or by the administrator to the file
     `ada_object_path'

   * a pragma `Linker_Options' has been added to one of the sources.
     For example:

         pragma Linker_Options ("-lmy_lib");

Note that you may also load a library dynamically at run time given its
filename, as illustrated in the GNAT `plugins' example in the directory
`share/examples/gnat/plugins' within the GNAT install area.


File: gnat_ugn.info,  Node: Stand-alone Ada Libraries,  Next: Rebuilding the GNAT Run-Time Library,  Prev: General Ada Libraries,  Up: GNAT and Libraries

3.9.3 Stand-alone Ada Libraries
-------------------------------

* Menu:

* Introduction to Stand-alone Libraries::
* Building a Stand-alone Library::
* Creating a Stand-alone Library to be used in a non-Ada context::
* Restrictions in Stand-alone Libraries::


File: gnat_ugn.info,  Node: Introduction to Stand-alone Libraries,  Next: Building a Stand-alone Library,  Up: Stand-alone Ada Libraries

3.9.3.1 Introduction to Stand-alone Libraries
.............................................

A Stand-alone Library (abbreviated 'SAL') is a library that contains the
necessary code to elaborate the Ada units that are included in the
library. In contrast with an ordinary library, which consists of all
sources, objects and `ALI' files of the library, a SAL may specify a
restricted subset of compilation units to serve as a library interface.
In this case, the fully self-sufficient set of files will normally
consist of an objects archive, the sources of interface units' specs,
and the `ALI' files of interface units.  If an interface spec contains
a generic unit or an inlined subprogram, the body's source must also be
provided; if the units that must be provided in the source form depend
on other units, the source and `ALI' files of those must also be
provided.

The main purpose of a SAL is to minimize the recompilation overhead of
client applications when a new version of the library is installed.
Specifically, if the interface sources have not changed, client
applications do not need to be recompiled. If, furthermore, a SAL is
provided in the shared form and its version, controlled by
`Library_Version' attribute, is not changed, then the clients do not
need to be relinked.

SALs also allow the library providers to minimize the amount of library
source text exposed to the clients.  Such 'information hiding' might be
useful or necessary for various reasons.

Stand-alone libraries are also well suited to be used in an executable
whose main routine is not written in Ada.


File: gnat_ugn.info,  Node: Building a Stand-alone Library,  Next: Creating a Stand-alone Library to be used in a non-Ada context,  Prev: Introduction to Stand-alone Libraries,  Up: Stand-alone Ada Libraries

3.9.3.2 Building a Stand-alone Library
......................................

GNAT's Project facility provides a simple way of building and installing
stand-alone libraries; see *note Stand-alone Library Projects: 97.  To
be a Stand-alone Library Project, in addition to the two attributes
that make a project a Library Project (`Library_Name' and
`Library_Dir'; see *note Library Projects: 8a.), the attribute
`Library_Interface' must be defined.  For example:

    for Library_Dir use "lib_dir";
    for Library_Name use "dummy";
    for Library_Interface use ("int1", "int1.child");

Attribute `Library_Interface' has a non-empty string list value, each
string in the list designating a unit contained in an immediate source
of the project file.

When a Stand-alone Library is built, first the binder is invoked to
build a package whose name depends on the library name (`b~dummy.ads/b'
in the example above).  This binder-generated package includes
initialization and finalization procedures whose names depend on the
library name (`dummyinit' and `dummyfinal' in the example above). The
object corresponding to this package is included in the library.

You must ensure timely (e.g., prior to any use of interfaces in the SAL)
calling of these procedures if a static SAL is built, or if a shared SAL
is built with the project-level attribute `Library_Auto_Init' set to
`"false"'.

For a Stand-Alone Library, only the `ALI' files of the Interface Units
(those that are listed in attribute `Library_Interface') are copied to
the Library Directory. As a consequence, only the Interface Units may be
imported from Ada units outside of the library. If other units are
imported, the binding phase will fail.

It is also possible to build an encapsulated library where not only the
code to elaborate and finalize the library is embedded but also
ensuring that the library is linked only against static libraries. So
an encapsulated library only depends on system libraries, all other
code, including the GNAT runtime, is embedded. To build an encapsulated
library the attribute `Library_Standalone' must be set to
`encapsulated':

    for Library_Dir use "lib_dir";
    for Library_Name use "dummy";
    for Library_Kind use "dynamic";
    for Library_Interface use ("int1", "int1.child");
    for Library_Standalone use "encapsulated";

The default value for this attribute is `standard' in which case a
stand-alone library is built.

The attribute `Library_Src_Dir' may be specified for a Stand-Alone
Library. `Library_Src_Dir' is a simple attribute that has a single
string value. Its value must be the path (absolute or relative to the
project directory) of an existing directory. This directory cannot be
the object directory or one of the source directories, but it can be
the same as the library directory. The sources of the Interface Units
of the library that are needed by an Ada client of the library will be
copied to the designated directory, called the Interface Copy directory.
These sources include the specs of the Interface Units, but they may
also include bodies and subunits, when pragmas `Inline' or
`Inline_Always' are used, or when there is a generic unit in the spec.
Before the sources are copied to the Interface Copy directory, an
attempt is made to delete all files in the Interface Copy directory.

Building stand-alone libraries by hand is somewhat tedious, but for
those occasions when it is necessary here are the steps that you need
to perform:

   * Compile all library sources.

   * Invoke the binder with the switch `-n' (No Ada main program), with
     all the `ALI' files of the interfaces, and with the switch `-L' to
     give specific names to the `init' and `final' procedures.  For
     example:

         $ gnatbind -n int1.ali int2.ali -Lsal1

   * Compile the binder generated file:

         $ gcc -c b~int2.adb

   * Link the dynamic library with all the necessary object files,
     indicating to the linker the names of the `init' (and possibly
     `final') procedures for automatic initialization (and
     finalization).  The built library should be placed in a directory
     different from the object directory.

   * Copy the `ALI' files of the interface to the library directory,
     add in this copy an indication that it is an interface to a SAL
     (i.e., add a word `SL' on the line in the `ALI' file that starts
     with letter 'P') and make the modified copy of the `ALI' file
     read-only.

Using SALs is not different from using other libraries (see *note Using
a library: 8f.).


File: gnat_ugn.info,  Node: Creating a Stand-alone Library to be used in a non-Ada context,  Next: Restrictions in Stand-alone Libraries,  Prev: Building a Stand-alone Library,  Up: Stand-alone Ada Libraries

3.9.3.3 Creating a Stand-alone Library to be used in a non-Ada context
......................................................................

It is easy to adapt the SAL build procedure discussed above for use of
a SAL in a non-Ada context.

The only extra step required is to ensure that library interface
subprograms are compatible with the main program, by means of `pragma
Export' or `pragma Convention'.

Here is an example of simple library interface for use with C main
program:

    package My_Package is

       procedure Do_Something;
       pragma Export (C, Do_Something, "do_something");

       procedure Do_Something_Else;
       pragma Export (C, Do_Something_Else, "do_something_else");

    end My_Package;

On the foreign language side, you must provide a 'foreign' view of the
library interface; remember that it should contain elaboration routines
in addition to interface subprograms.

The example below shows the content of `mylib_interface.h' (note that
there is no rule for the naming of this file, any name can be used)

    /* the library elaboration procedure */
    extern void mylibinit (void);

    /* the library finalization procedure */
    extern void mylibfinal (void);

    /* the interface exported by the library */
    extern void do_something (void);
    extern void do_something_else (void);

Libraries built as explained above can be used from any program,
provided that the elaboration procedures (named `mylibinit' in the
previous example) are called before the library services are used. Any
number of libraries can be used simultaneously, as long as the
elaboration procedure of each library is called.

Below is an example of a C program that uses the `mylib' library.

    #include "mylib_interface.h"

    int
    main (void)
    {
       /* First, elaborate the library before using it */
       mylibinit ();

       /* Main program, using the library exported entities */
       do_something ();
       do_something_else ();

       /* Library finalization at the end of the program */
       mylibfinal ();
       return 0;
    }

Note that invoking any library finalization procedure generated by
`gnatbind' shuts down the Ada run-time environment.  Consequently, the
finalization of all Ada libraries must be performed at the end of the
program.  No call to these libraries or to the Ada run-time library
should be made after the finalization phase.

Note also that special care must be taken with multi-tasks
applications. The initialization and finalization routines are not
protected against concurrent access. If such requirement is needed it
must be ensured at the application level using a specific operating
system services like a mutex or a critical-section.


File: gnat_ugn.info,  Node: Restrictions in Stand-alone Libraries,  Prev: Creating a Stand-alone Library to be used in a non-Ada context,  Up: Stand-alone Ada Libraries

3.9.3.4 Restrictions in Stand-alone Libraries
.............................................

The pragmas listed below should be used with caution inside libraries,
as they can create incompatibilities with other Ada libraries:

   * pragma `Locking_Policy'

   * pragma `Partition_Elaboration_Policy'

   * pragma `Queuing_Policy'

   * pragma `Task_Dispatching_Policy'

   * pragma `Unreserve_All_Interrupts'

When using a library that contains such pragmas, the user must make sure
that all libraries use the same pragmas with the same values. Otherwise,
`Program_Error' will be raised during the elaboration of the conflicting
libraries. The usage of these pragmas and its consequences for the user
should therefore be well documented.

Similarly, the traceback in the exception occurrence mechanism should be
enabled or disabled in a consistent manner across all libraries.
Otherwise, Program_Error will be raised during the elaboration of the
conflicting libraries.

If the `Version' or `Body_Version' attributes are used inside a
library, then you need to perform a `gnatbind' step that specifies all
`ALI' files in all libraries, so that version identifiers can be
properly computed.  In practice these attributes are rarely used, so
this is unlikely to be a consideration.


File: gnat_ugn.info,  Node: Rebuilding the GNAT Run-Time Library,  Prev: Stand-alone Ada Libraries,  Up: GNAT and Libraries

3.9.4 Rebuilding the GNAT Run-Time Library
------------------------------------------

It may be useful to recompile the GNAT library in various contexts, the
most important one being the use of partition-wide configuration pragmas
such as `Normalize_Scalars'. A special Makefile called
`Makefile.adalib' is provided to that effect and can be found in the
directory containing the GNAT library. The location of this directory
depends on the way the GNAT environment has been installed and can be
determined by means of the command:

    $ gnatls -v

The last entry in the object search path usually contains the gnat
library. This Makefile contains its own documentation and in particular
the set of instructions needed to rebuild a new library and to use it.


File: gnat_ugn.info,  Node: Conditional Compilation,  Next: Mixed Language Programming,  Prev: GNAT and Libraries,  Up: The GNAT Compilation Model

3.10 Conditional Compilation
============================

This section presents some guidelines for modeling conditional
compilation in Ada and describes the gnatprep preprocessor utility.

* Menu:

* Modeling Conditional Compilation in Ada::
* Preprocessing with gnatprep::
* Integrated Preprocessing::


File: gnat_ugn.info,  Node: Modeling Conditional Compilation in Ada,  Next: Preprocessing with gnatprep,  Up: Conditional Compilation

3.10.1 Modeling Conditional Compilation in Ada
----------------------------------------------

It is often necessary to arrange for a single source program to serve
multiple purposes, where it is compiled in different ways to achieve
these different goals. Some examples of the need for this feature are

   * Adapting a program to a different hardware environment

   * Adapting a program to a different target architecture

   * Turning debugging features on and off

   * Arranging for a program to compile with different compilers

In C, or C++, the typical approach would be to use the preprocessor
that is defined as part of the language. The Ada language does not
contain such a feature. This is not an oversight, but rather a very
deliberate design decision, based on the experience that overuse of the
preprocessing features in C and C++ can result in programs that are
extremely difficult to maintain. For example, if we have ten switches
that can be on or off, this means that there are a thousand separate
programs, any one of which might not even be syntactically correct, and
even if syntactically correct, the resulting program might not work
correctly. Testing all combinations can quickly become impossible.

Nevertheless, the need to tailor programs certainly exists, and in this
section we will discuss how this can be achieved using Ada in general,
and GNAT in particular.

* Menu:

* Use of Boolean Constants::
* Debugging - A Special Case::
* Conditionalizing Declarations::
* Use of Alternative Implementations::
* Preprocessing::


File: gnat_ugn.info,  Node: Use of Boolean Constants,  Next: Debugging - A Special Case,  Up: Modeling Conditional Compilation in Ada

3.10.1.1 Use of Boolean Constants
.................................

In the case where the difference is simply which code sequence is
executed, the cleanest solution is to use Boolean constants to control
which code is executed.

    FP_Initialize_Required : constant Boolean := True;
    ...
    if FP_Initialize_Required then
    ...
    end if;

Not only will the code inside the `if' statement not be executed if the
constant Boolean is `False', but it will also be completely deleted
from the program.  However, the code is only deleted after the `if'
statement has been checked for syntactic and semantic correctness.  (In
contrast, with preprocessors the code is deleted before the compiler
ever gets to see it, so it is not checked until the switch is turned
on.)

Typically the Boolean constants will be in a separate package,
something like:

    package Config is
       FP_Initialize_Required : constant Boolean := True;
       Reset_Available        : constant Boolean := False;
       ...
    end Config;

The `Config' package exists in multiple forms for the various targets,
with an appropriate script selecting the version of `Config' needed.
Then any other unit requiring conditional compilation can do a `with'
of `Config' to make the constants visible.


File: gnat_ugn.info,  Node: Debugging - A Special Case,  Next: Conditionalizing Declarations,  Prev: Use of Boolean Constants,  Up: Modeling Conditional Compilation in Ada

3.10.1.2 Debugging - A Special Case
...................................

A common use of conditional code is to execute statements (for example
dynamic checks, or output of intermediate results) under control of a
debug switch, so that the debugging behavior can be turned on and off.
This can be done using a Boolean constant to control whether the code
is active:

    if Debugging then
       Put_Line ("got to the first stage!");
    end if;

or

    if Debugging and then Temperature > 999.0 then
       raise Temperature_Crazy;
    end if;

Since this is a common case, there are special features to deal with
this in a convenient manner. For the case of tests, Ada 2005 has added
a pragma `Assert' that can be used for such tests. This pragma is
modeled on the `Assert' pragma that has always been available in GNAT,
so this feature may be used with GNAT even if you are not using Ada
2005 features.  The use of pragma `Assert' is described in the
`GNAT_Reference_Manual', but as an example, the last test could be
written:

    pragma Assert (Temperature <= 999.0, "Temperature Crazy");

or simply

    pragma Assert (Temperature <= 999.0);

In both cases, if assertions are active and the temperature is
excessive, the exception `Assert_Failure' will be raised, with the
given string in the first case or a string indicating the location of
the pragma in the second case used as the exception message.

You can turn assertions on and off by using the `Assertion_Policy'
pragma.

This is an Ada 2005 pragma which is implemented in all modes by GNAT.
Alternatively, you can use the `-gnata' switch to enable assertions
from the command line, which applies to all versions of Ada.

For the example above with the `Put_Line', the GNAT-specific pragma
`Debug' can be used:

    pragma Debug (Put_Line ("got to the first stage!"));

If debug pragmas are enabled, the argument, which must be of the form of
a procedure call, is executed (in this case, `Put_Line' will be called).
Only one call can be present, but of course a special debugging
procedure containing any code you like can be included in the program
and then called in a pragma `Debug' argument as needed.

One advantage of pragma `Debug' over the `if Debugging then' construct
is that pragma `Debug' can appear in declarative contexts, such as at
the very beginning of a procedure, before local declarations have been
elaborated.

Debug pragmas are enabled using either the `-gnata' switch that also
controls assertions, or with a separate Debug_Policy pragma.

The latter pragma is new in the Ada 2005 versions of GNAT (but it can
be used in Ada 95 and Ada 83 programs as well), and is analogous to
pragma `Assertion_Policy' to control assertions.

`Assertion_Policy' and `Debug_Policy' are configuration pragmas, and
thus they can appear in `gnat.adc' if you are not using a project file,
or in the file designated to contain configuration pragmas in a project
file.  They then apply to all subsequent compilations. In practice the
use of the `-gnata' switch is often the most convenient method of
controlling the status of these pragmas.

Note that a pragma is not a statement, so in contexts where a statement
sequence is required, you can't just write a pragma on its own. You have
to add a `null' statement.

    if ... then
       ... -- some statements
    else
       pragma Assert (Num_Cases < 10);
       null;
    end if;


File: gnat_ugn.info,  Node: Conditionalizing Declarations,  Next: Use of Alternative Implementations,  Prev: Debugging - A Special Case,  Up: Modeling Conditional Compilation in Ada

3.10.1.3 Conditionalizing Declarations
......................................

In some cases it may be necessary to conditionalize declarations to meet
different requirements. For example we might want a bit string whose
length is set to meet some hardware message requirement.

This may be possible using declare blocks controlled by conditional
constants:

    if Small_Machine then
       declare
          X : Bit_String (1 .. 10);
       begin
          ...
       end;
    else
       declare
          X : Large_Bit_String (1 .. 1000);
       begin
          ...
       end;
    end if;

Note that in this approach, both declarations are analyzed by the
compiler so this can only be used where both declarations are legal,
even though one of them will not be used.

Another approach is to define integer constants, e.g., `Bits_Per_Word',
or Boolean constants, e.g., `Little_Endian', and then write declarations
that are parameterized by these constants. For example

    for Rec use
      Field1 at 0 range Boolean'Pos (Little_Endian) * 10 .. Bits_Per_Word;
    end record;

If `Bits_Per_Word' is set to 32, this generates either

    for Rec use
      Field1 at 0 range 0 .. 32;
    end record;

for the big endian case, or

    for Rec use record
        Field1 at 0 range 10 .. 32;
    end record;

for the little endian case. Since a powerful subset of Ada expression
notation is usable for creating static constants, clever use of this
feature can often solve quite difficult problems in conditionalizing
compilation (note incidentally that in Ada 95, the little endian
constant was introduced as `System.Default_Bit_Order', so you do not
need to define this one yourself).


File: gnat_ugn.info,  Node: Use of Alternative Implementations,  Next: Preprocessing,  Prev: Conditionalizing Declarations,  Up: Modeling Conditional Compilation in Ada

3.10.1.4 Use of Alternative Implementations
...........................................

In some cases, none of the approaches described above are adequate. This
can occur for example if the set of declarations required is radically
different for two different configurations.

In this situation, the official Ada way of dealing with conditionalizing
such code is to write separate units for the different cases. As long as
this does not result in excessive duplication of code, this can be done
without creating maintenance problems. The approach is to share common
code as far as possible, and then isolate the code and declarations
that are different. Subunits are often a convenient method for breaking
out a piece of a unit that is to be conditionalized, with separate files
for different versions of the subunit for different targets, where the
build script selects the right one to give to the compiler.

As an example, consider a situation where a new feature in Ada 2005
allows something to be done in a really nice way. But your code must be
able to compile with an Ada 95 compiler. Conceptually you want to say:

    if Ada_2005 then
       ... neat Ada 2005 code
    else
       ... not quite as neat Ada 95 code
    end if;

where `Ada_2005' is a Boolean constant.

But this won't work when `Ada_2005' is set to `False', since the `then'
clause will be illegal for an Ada 95 compiler.  (Recall that although
such unreachable code would eventually be deleted by the compiler, it
still needs to be legal.  If it uses features introduced in Ada 2005,
it will be illegal in Ada 95.)

So instead we write

    procedure Insert is separate;

Then we have two files for the subunit `Insert', with the two sets of
code.  If the package containing this is called `File_Queries', then we
might have two files

   * `file_queries-insert-2005.adb'

   * `file_queries-insert-95.adb'

and the build script renames the appropriate file to
`file_queries-insert.adb' and then carries out the compilation.

This can also be done with project files' naming schemes. For example:

    for body ("File_Queries.Insert") use "file_queries-insert-2005.ada";

Note also that with project files it is desirable to use a different
extension than `ads' / `adb' for alternative versions. Otherwise a
naming conflict may arise through another commonly used feature: to
declare as part of the project a set of directories containing all the
sources obeying the default naming scheme.

The use of alternative units is certainly feasible in all situations,
and for example the Ada part of the GNAT run-time is conditionalized
based on the target architecture using this approach. As a specific
example, consider the implementation of the AST feature in VMS. There
is one spec: `s-asthan.ads' which is the same for all architectures,
and three bodies:

   *
    `s-asthan.adb'
          used for all non-VMS operating systems

   *
    `s-asthan-vms-alpha.adb'
          used for VMS on the Alpha

   *
    `s-asthan-vms-ia64.adb'
          used for VMS on the ia64

The dummy version `s-asthan.adb' simply raises exceptions noting that
this operating system feature is not available, and the two remaining
versions interface with the corresponding versions of VMS to provide
VMS-compatible AST handling. The GNAT build script knows the
architecture and operating system, and automatically selects the right
version, renaming it if necessary to `s-asthan.adb' before the run-time
build.

Another style for arranging alternative implementations is through Ada's
access-to-subprogram facility.  In case some functionality is to be
conditionally included, you can declare an access-to-procedure variable
`Ref' that is initialized to designate a 'do nothing' procedure, and
then invoke `Ref.all' when appropriate.  In some library package, set
`Ref' to `Proc'Access' for some procedure `Proc' that performs the
relevant processing.  The initialization only occurs if the library
package is included in the program.  The same idea can also be
implemented using tagged types and dispatching calls.


File: gnat_ugn.info,  Node: Preprocessing,  Prev: Use of Alternative Implementations,  Up: Modeling Conditional Compilation in Ada

3.10.1.5 Preprocessing
......................

Although it is quite possible to conditionalize code without the use of
C-style preprocessing, as described earlier in this section, it is
nevertheless convenient in some cases to use the C approach. Moreover,
older Ada compilers have often provided some preprocessing capability,
so legacy code may depend on this approach, even though it is not
standard.

To accommodate such use, GNAT provides a preprocessor (modeled to a
large extent on the various preprocessors that have been used with
legacy code on other compilers, to enable easier transition).

The preprocessor may be used in two separate modes. It can be used quite
separately from the compiler, to generate a separate output source file
that is then fed to the compiler as a separate step. This is the
`gnatprep' utility, whose use is fully described in *note Preprocessing
with gnatprep: 19.

The preprocessing language allows such constructs as

    #if DEBUG or else (PRIORITY > 4) then
       bunch of declarations
    #else
       completely different bunch of declarations
    #end if;

The values of the symbols `DEBUG' and `PRIORITY' can be defined either
on the command line or in a separate file.

The other way of running the preprocessor is even closer to the C style
and often more convenient. In this approach the preprocessing is
integrated into the compilation process. The compiler is fed the
preprocessor input which includes `#if' lines etc, and then the
compiler carries out the preprocessing internally and processes the
resulting output.  For more details on this approach, see *note
Integrated Preprocessing: 1a.


File: gnat_ugn.info,  Node: Preprocessing with gnatprep,  Next: Integrated Preprocessing,  Prev: Modeling Conditional Compilation in Ada,  Up: Conditional Compilation

3.10.2 Preprocessing with `gnatprep'
------------------------------------

This section discusses how to use GNAT's `gnatprep' utility for simple
preprocessing.  Although designed for use with GNAT, `gnatprep' does
not depend on any special GNAT features.  For further discussion of
conditional compilation in general, see *note Conditional Compilation:
18.

* Menu:

* Preprocessing Symbols::
* Using gnatprep::
* Switches for gnatprep::
* Form of Definitions File::
* Form of Input Text for gnatprep::


File: gnat_ugn.info,  Node: Preprocessing Symbols,  Next: Using gnatprep,  Up: Preprocessing with gnatprep

3.10.2.1 Preprocessing Symbols
..............................

Preprocessing symbols are defined in definition files and referred to in
sources to be preprocessed. A Preprocessing symbol is an identifier,
following normal Ada (case-insensitive) rules for its syntax, with the
restriction that all characters need to be in the ASCII set (no
accented letters).


File: gnat_ugn.info,  Node: Using gnatprep,  Next: Switches for gnatprep,  Prev: Preprocessing Symbols,  Up: Preprocessing with gnatprep

3.10.2.2 Using `gnatprep'
.........................

To call `gnatprep' use:

    $ gnatprep [`switches`] `infile` `outfile` [`deffile`]

where

   *
    `switches'
          is an optional sequence of switches as described in the next
          section.

   *
    `infile'
          is the full name of the input file, which is an Ada source
          file containing preprocessor directives.

   *
    `outfile'
          is the full name of the output file, which is an Ada source
          in standard Ada form. When used with GNAT, this file name will
          normally have an ads or adb suffix.

   *
    `deffile'
          is the full name of a text file containing definitions of
          preprocessing symbols to be referenced by the preprocessor.
          This argument is optional, and can be replaced by the use of
          the `-D' switch.


File: gnat_ugn.info,  Node: Switches for gnatprep,  Next: Form of Definitions File,  Prev: Using gnatprep,  Up: Preprocessing with gnatprep

3.10.2.3 Switches for `gnatprep'
................................

`-b'
     Causes both preprocessor lines and the lines deleted by
     preprocessing to be replaced by blank lines in the output source
     file, preserving line numbers in the output file.

`-c'
     Causes both preprocessor lines and the lines deleted by
     preprocessing to be retained in the output source as comments
     marked with the special string `"-! "'. This option will result in
     line numbers being preserved in the output file.

`-C'
     Causes comments to be scanned. Normally comments are ignored by
     gnatprep.  If this option is specified, then comments are scanned
     and any $symbol substitutions performed as in program text. This
     is particularly useful when structured comments are used (e.g.,
     when writing programs in the SPARK dialect of Ada). Note that this
     switch is not available when doing integrated preprocessing (it
     would be useless in this context since comments are ignored by the
     compiler in any case).

`-D`symbol'=`value''
     Defines a new preprocessing symbol, associated with value. If no
     value is given on the command line, then symbol is considered to
     be `True'. This switch can be used in place of a definition file.

`-r'
     Causes a `Source_Reference' pragma to be generated that references
     the original input file, so that error messages will use the file
     name of this original file. The use of this switch implies that
     preprocessor lines are not to be removed from the file, so its use
     will force `-b' mode if `-c' has not been specified explicitly.

     Note that if the file to be preprocessed contains multiple units,
     then it will be necessary to `gnatchop' the output file from
     `gnatprep'. If a `Source_Reference' pragma is present in the
     preprocessed file, it will be respected by `gnatchop -r' so that
     the final chopped files will correctly refer to the original input
     source file for `gnatprep'.

`-s'
     Causes a sorted list of symbol names and values to be listed on
     the standard output file.

`-u'
     Causes undefined symbols to be treated as having the value FALSE
     in the context of a preprocessor test. In the absence of this
     option, an undefined symbol in a `#if' or `#elsif' test will be
     treated as an error.

Note: if neither `-b' nor `-c' is present, then preprocessor lines and
deleted lines are completely removed from the output, unless -r is
specified, in which case -b is assumed.


File: gnat_ugn.info,  Node: Form of Definitions File,  Next: Form of Input Text for gnatprep,  Prev: Switches for gnatprep,  Up: Preprocessing with gnatprep

3.10.2.4 Form of Definitions File
.................................

The definitions file contains lines of the form:

    symbol := value

where `symbol' is a preprocessing symbol, and `value' is one of the
following:

   * Empty, corresponding to a null substitution,

   * A string literal using normal Ada syntax, or

   * Any sequence of characters from the set {letters, digits, period,
     underline}.

Comment lines may also appear in the definitions file, starting with
the usual `--', and comments may be added to the definitions lines.


File: gnat_ugn.info,  Node: Form of Input Text for gnatprep,  Prev: Form of Definitions File,  Up: Preprocessing with gnatprep

3.10.2.5 Form of Input Text for `gnatprep'
..........................................

The input text may contain preprocessor conditional inclusion lines, as
well as general symbol substitution sequences.

The preprocessor conditional inclusion commands have the form:

    #if <expression> [then]
       lines
    #elsif <expression> [then]
       lines
    #elsif <expression> [then]
       lines
    ...
    #else
       lines
    #end if;

In this example, <expression> is defined by the following grammar:

    <expression> ::=  <symbol>
    <expression> ::=  <symbol> = "<value>"
    <expression> ::=  <symbol> = <symbol>
    <expression> ::=  <symbol> = <integer>
    <expression> ::=  <symbol> > <integer>
    <expression> ::=  <symbol> >= <integer>
    <expression> ::=  <symbol> < <integer>
    <expression> ::=  <symbol> <= <integer>
    <expression> ::=  <symbol> 'Defined
    <expression> ::=  not <expression>
    <expression> ::=  <expression> and <expression>
    <expression> ::=  <expression> or <expression>
    <expression> ::=  <expression> and then <expression>
    <expression> ::=  <expression> or else <expression>
    <expression> ::=  ( <expression> )

Note the following restriction: it is not allowed to have "and" or "or"
following "not" in the same expression without parentheses. For
example, this is not allowed:

    not X or Y

This can be expressed instead as one of the following forms:

    (not X) or Y
    not (X or Y)

For the first test (<expression> ::= <symbol>) the symbol must have
either the value true or false, that is to say the right-hand of the
symbol definition must be one of the (case-insensitive) literals `True'
or `False'. If the value is true, then the corresponding lines are
included, and if the value is false, they are excluded.

When comparing a symbol to an integer, the integer is any non negative
literal integer as defined in the Ada Reference Manual, such as 3,
16#FF# or 2#11#. The symbol value must also be a non negative integer.
Integer values in the range 0 .. 2**31-1 are supported.

The test (<expression> ::= <symbol>'Defined) is true only if the symbol
has been defined in the definition file or by a `-D' switch on the
command line. Otherwise, the test is false.

The equality tests are case insensitive, as are all the preprocessor
lines.

If the symbol referenced is not defined in the symbol definitions file,
then the effect depends on whether or not switch `-u' is specified. If
so, then the symbol is treated as if it had the value false and the
test fails. If this switch is not specified, then it is an error to
reference an undefined symbol. It is also an error to reference a
symbol that is defined with a value other than `True' or `False'.

The use of the `not' operator inverts the sense of this logical test.
The `not' operator cannot be combined with the `or' or `and' operators,
without parentheses. For example, "if not X or Y then" is not allowed,
but "if (not X) or Y then" and "if not (X or Y) then" are.

The `then' keyword is optional as shown

The `#' must be the first non-blank character on a line, but otherwise
the format is free form. Spaces or tabs may appear between the `#' and
the keyword. The keywords and the symbols are case insensitive as in
normal Ada code. Comments may be used on a preprocessor line, but other
than that, no other tokens may appear on a preprocessor line. Any
number of `elsif' clauses can be present, including none at all. The
`else' is optional, as in Ada.

The `#' marking the start of a preprocessor line must be the first
non-blank character on the line, i.e., it must be preceded only by
spaces or horizontal tabs.

Symbol substitution outside of preprocessor lines is obtained by using
the sequence:

    $symbol

anywhere within a source line, except in a comment or within a string
literal. The identifier following the `$' must match one of the symbols
defined in the symbol definition file, and the result is to substitute
the value of the symbol in place of `$symbol' in the output file.

Note that although the substitution of strings within a string literal
is not possible, it is possible to have a symbol whose defined value is
a string literal. So instead of setting XYZ to `hello' and writing:

    Header : String := "$XYZ";

you should set XYZ to `"hello"' and write:

    Header : String := $XYZ;

and then the substitution will occur as desired.


File: gnat_ugn.info,  Node: Integrated Preprocessing,  Prev: Preprocessing with gnatprep,  Up: Conditional Compilation

3.10.3 Integrated Preprocessing
-------------------------------

GNAT sources may be preprocessed immediately before compilation.  In
this case, the actual text of the source is not the text of the source
file, but is derived from it through a process called preprocessing.
Integrated preprocessing is specified through switches `-gnatep' and/or
`-gnateD'. `-gnatep' indicates, through a text file, the preprocessing
data to be used.  `-gnateD' specifies or modifies the values of
preprocessing symbol.  Note that integrated preprocessing applies only
to Ada source files, it is not available for configuration pragma files.

Note that when integrated preprocessing is used, the output from the
preprocessor is not written to any external file. Instead it is passed
internally to the compiler. If you need to preserve the result of
preprocessing in a file, then you should use `gnatprep' to perform the
desired preprocessing in stand-alone mode.

It is recommended that `gnatmake' switch -s should be used when
Integrated Preprocessing is used. The reason is that preprocessing with
another Preprocessing Data file without changing the sources will not
trigger recompilation without this switch.

Note that `gnatmake' switch -m will almost always trigger recompilation
for sources that are preprocessed, because `gnatmake' cannot compute
the checksum of the source after preprocessing.

The actual preprocessing function is described in detail in section
*note Preprocessing with gnatprep: 19. This section only describes how
integrated preprocessing is triggered and parameterized.

`-gnatep=`file''
     This switch indicates to the compiler the file name (without
     directory information) of the preprocessor data file to use. The
     preprocessor data file should be found in the source directories.
     Note that when the compiler is called by a builder such as
     (`gnatmake' with a project file, if the object directory is not
     also a source directory, the builder needs to be called with `-x'.

     A preprocessing data file is a text file with significant lines
     indicating how should be preprocessed either a specific source or
     all sources not mentioned in other lines. A significant line is a
     nonempty, non-comment line.  Comments are similar to Ada comments.

     Each significant line starts with either a literal string or the
     character '*'.  A literal string is the file name (without
     directory information) of the source to preprocess. A character
     '*' indicates the preprocessing for all the sources that are not
     specified explicitly on other lines (order of the lines is not
     significant). It is an error to have two lines with the same file
     name or two lines starting with the character '*'.

     After the file name or the character '*', another optional literal
     string indicating the file name of the definition file to be used
     for preprocessing (*note Form of Definitions File: b2.). The
     definition files are found by the compiler in one of the source
     directories. In some cases, when compiling a source in a directory
     other than the current directory, if the definition file is in the
     current directory, it may be necessary to add the current
     directory as a source directory through switch -I., otherwise the
     compiler would not find the definition file.

     Then, optionally, switches similar to those of `gnatprep' may be
     found. Those switches are:

    `-b'
          Causes both preprocessor lines and the lines deleted by
          preprocessing to be replaced by blank lines, preserving the
          line number.  This switch is always implied; however, if
          specified after `-c' it cancels the effect of `-c'.

    `-c'
          Causes both preprocessor lines and the lines deleted by
          preprocessing to be retained as comments marked with the
          special string '`-!'.

    `-Dsymbol=`value''
          Define or redefine a symbol, associated with value. A symbol
          is an Ada identifier, or an Ada reserved word, with the
          exception of `if', `else', `elsif', `end', `and', `or' and
          `then'.  `value' is either a literal string, an Ada
          identifier or any Ada reserved word. A symbol declared with
          this switch replaces a symbol with the same name defined in a
          definition file.

    `-s'
          Causes a sorted list of symbol names and values to be listed
          on the standard output file.

    `-u'
          Causes undefined symbols to be treated as having the value
          `FALSE' in the context of a preprocessor test. In the absence
          of this option, an undefined symbol in a `#if' or `#elsif'
          test will be treated as an error.

     Examples of valid lines in a preprocessor data file:

         "toto.adb"  "prep.def" -u
         --  preprocess "toto.adb", using definition file "prep.def",
         --  undefined symbol are False.

         * -c -DVERSION=V101
         --  preprocess all other sources without a definition file;
         --  suppressed lined are commented; symbol VERSION has the value V101.

         "titi.adb" "prep2.def" -s
         --  preprocess "titi.adb", using definition file "prep2.def";
         --  list all symbols with their values.

`-gnateDsymbol[=value]'
     Define or redefine a preprocessing symbol, associated with value.
     If no value is given on the command line, then the value of the
     symbol is `True'.  A symbol is an identifier, following normal Ada
     (case-insensitive) rules for its syntax, and value is either an
     arbitrary string between double quotes or any sequence (including
     an empty sequence) of characters from the set (letters, digits,
     period, underline).  Ada reserved words may be used as symbols,
     with the exceptions of `if', `else', `elsif', `end', `and', `or'
     and `then'.

     Examples:

         -gnateDToto=Titi
         -gnateDFoo
         -gnateDFoo=\"Foo-Bar\"

     A symbol declared with this switch on the command line replaces a
     symbol with the same name either in a definition file or specified
     with a switch -D in the preprocessor data file.

     This switch is similar to switch `-D' of `gnatprep'.

`-gnateG'
     When integrated preprocessing is performed and the preprocessor
     modifies the source text, write the result of this preprocessing
     into a file <source>.prep.


File: gnat_ugn.info,  Node: Mixed Language Programming,  Next: GNAT and Other Compilation Models,  Prev: Conditional Compilation,  Up: The GNAT Compilation Model

3.11 Mixed Language Programming
===============================

This section describes how to develop a mixed-language program, with a
focus on combining Ada with C or C++.

* Menu:

* Interfacing to C::
* Calling Conventions::
* Building Mixed Ada and C++ Programs::
* Generating Ada Bindings for C and C++ headers::
* Generating C Headers for Ada Specifications::


File: gnat_ugn.info,  Node: Interfacing to C,  Next: Calling Conventions,  Up: Mixed Language Programming

3.11.1 Interfacing to C
-----------------------

Interfacing Ada with a foreign language such as C involves using
compiler directives to import and/or export entity definitions in each
language - using `extern' statements in C, for instance, and the
`Import', `Export', and `Convention' pragmas in Ada.  A full treatment
of these topics is provided in Appendix B, section 1 of the Ada
Reference Manual.

There are two ways to build a program using GNAT that contains some Ada
sources and some foreign language sources, depending on whether or not
the main subprogram is written in Ada.  Here is a source example with
the main subprogram in Ada:

    /* file1.c */
    #include <stdio.h>

    void print_num (int num)
    {
      printf ("num is %d.\\n", num);
      return;
    }

    /* file2.c */

    /* num_from_Ada is declared in my_main.adb */
    extern int num_from_Ada;

    int get_num (void)
    {
      return num_from_Ada;
    }

    --  my_main.adb
    procedure My_Main is

       --  Declare then export an Integer entity called num_from_Ada
       My_Num : Integer := 10;
       pragma Export (C, My_Num, "num_from_Ada");

       --  Declare an Ada function spec for Get_Num, then use
       --  C function get_num for the implementation.
       function Get_Num return Integer;
       pragma Import (C, Get_Num, "get_num");

       --  Declare an Ada procedure spec for Print_Num, then use
       --  C function print_num for the implementation.
       procedure Print_Num (Num : Integer);
       pragma Import (C, Print_Num, "print_num";

    begin
       Print_Num (Get_Num);
    end My_Main;

To build this example:

   * First compile the foreign language files to generate object files:

         $ gcc -c file1.c
         $ gcc -c file2.c

   * Then, compile the Ada units to produce a set of object files and
     ALI files:

         $ gnatmake -c my_main.adb

   * Run the Ada binder on the Ada main program:

         $ gnatbind my_main.ali

   * Link the Ada main program, the Ada objects and the other language
     objects:

         $ gnatlink my_main.ali file1.o file2.o

The last three steps can be grouped in a single command:

    $ gnatmake my_main.adb -largs file1.o file2.o

If the main program is in a language other than Ada, then you may have
more than one entry point into the Ada subsystem. You must use a special
binder option to generate callable routines that initialize and
finalize the Ada units (*note Binding with Non-Ada Main Programs: ba.).
Calls to the initialization and finalization routines must be inserted
in the main program, or some other appropriate point in the code. The
call to initialize the Ada units must occur before the first Ada
subprogram is called, and the call to finalize the Ada units must occur
after the last Ada subprogram returns. The binder will place the
initialization and finalization subprograms into the `b~xxx.adb' file
where they can be accessed by your C sources.  To illustrate, we have
the following example:

    /* main.c */
    extern void adainit (void);
    extern void adafinal (void);
    extern int add (int, int);
    extern int sub (int, int);

    int main (int argc, char *argv[])
    {
       int a = 21, b = 7;

       adainit();

       /* Should print "21 + 7 = 28" */
       printf ("%d + %d = %d\\n", a, b, add (a, b));

       /* Should print "21 - 7 = 14" */
       printf ("%d - %d = %d\\n", a, b, sub (a, b));

       adafinal();
    }

    --  unit1.ads
    package Unit1 is
       function Add (A, B : Integer) return Integer;
       pragma Export (C, Add, "add");
    end Unit1;

    --  unit1.adb
    package body Unit1 is
       function Add (A, B : Integer) return Integer is
       begin
          return A + B;
       end Add;
    end Unit1;

    --  unit2.ads
    package Unit2 is
       function Sub (A, B : Integer) return Integer;
       pragma Export (C, Sub, "sub");
    end Unit2;

    --  unit2.adb
    package body Unit2 is
       function Sub (A, B : Integer) return Integer is
       begin
          return A - B;
       end Sub;
    end Unit2;

The build procedure for this application is similar to the last
example's:

   * First, compile the foreign language files to generate object files:

         $ gcc -c main.c

   * Next, compile the Ada units to produce a set of object files and
     ALI files:

         $ gnatmake -c unit1.adb
         $ gnatmake -c unit2.adb

   * Run the Ada binder on every generated ALI file.  Make sure to use
     the `-n' option to specify a foreign main program:

         $ gnatbind -n unit1.ali unit2.ali

   * Link the Ada main program, the Ada objects and the foreign language
     objects. You need only list the last ALI file here:

         $ gnatlink unit2.ali main.o -o exec_file

     This procedure yields a binary executable called `exec_file'.

Depending on the circumstances (for example when your non-Ada main
object does not provide symbol `main'), you may also need to instruct
the GNAT linker not to include the standard startup objects by passing
the `-nostartfiles' switch to `gnatlink'.


File: gnat_ugn.info,  Node: Calling Conventions,  Next: Building Mixed Ada and C++ Programs,  Prev: Interfacing to C,  Up: Mixed Language Programming

3.11.2 Calling Conventions
--------------------------

GNAT follows standard calling sequence conventions and will thus
interface to any other language that also follows these conventions.
The following Convention identifiers are recognized by GNAT:

`Ada'
     This indicates that the standard Ada calling sequence will be used
     and all Ada data items may be passed without any limitations in the
     case where GNAT is used to generate both the caller and callee. It
     is also possible to mix GNAT generated code and code generated by
     another Ada compiler. In this case, the data types should be
     restricted to simple cases, including primitive types. Whether
     complex data types can be passed depends on the situation.
     Probably it is safe to pass simple arrays, such as arrays of
     integers or floats. Records may or may not work, depending on
     whether both compilers lay them out identically. Complex structures
     involving variant records, access parameters, tasks, or protected
     types, are unlikely to be able to be passed.

     Note that in the case of GNAT running on a platform that supports
     HP Ada 83, a higher degree of compatibility can be guaranteed, and
     in particular records are laid out in an identical manner in the
     two compilers. Note also that if output from two different
     compilers is mixed, the program is responsible for dealing with
     elaboration issues. Probably the safest approach is to write the
     main program in the version of Ada other than GNAT, so that it
     takes care of its own elaboration requirements, and then call the
     GNAT-generated adainit procedure to ensure elaboration of the GNAT
     components. Consult the documentation of the other Ada compiler
     for further details on elaboration.

     However, it is not possible to mix the tasking run time of GNAT and
     HP Ada 83, All the tasking operations must either be entirely
     within GNAT compiled sections of the program, or entirely within
     HP Ada 83 compiled sections of the program.

`Assembler'
     Specifies assembler as the convention. In practice this has the
     same effect as convention Ada (but is not equivalent in the sense
     of being considered the same convention).

`Asm'
     Equivalent to Assembler.


`COBOL'
     Data will be passed according to the conventions described in
     section B.4 of the Ada Reference Manual.

`C'
     Data will be passed according to the conventions described in
     section B.3 of the Ada Reference Manual.

     A note on interfacing to a C 'varargs' function:

          In C, `varargs' allows a function to take a variable number of
          arguments. There is no direct equivalent in this to Ada. One
          approach that can be used is to create a C wrapper for each
          different profile and then interface to this C wrapper. For
          example, to print an `int' value using `printf', create a C
          function `printfi' that takes two arguments, a pointer to a
          string and an int, and calls `printf'.  Then in the Ada
          program, use pragma `Import' to interface to `printfi'.

          It may work on some platforms to directly interface to a
          `varargs' function by providing a specific Ada profile for a
          particular call. However, this does not work on all
          platforms, since there is no guarantee that the calling
          sequence for a two argument normal C function is the same as
          for calling a `varargs' C function with the same two
          arguments.

`Default'
     Equivalent to C.

`External'
     Equivalent to C.

`C_Plus_Plus (or CPP)'
     This stands for C++. For most purposes this is identical to C.
     See the separate description of the specialized GNAT pragmas
     relating to C++ interfacing for further details.

`Fortran'
     Data will be passed according to the conventions described in
     section B.5 of the Ada Reference Manual.

`Intrinsic'
     This applies to an intrinsic operation, as defined in the Ada
     Reference Manual. If a pragma Import (Intrinsic) applies to a
     subprogram, this means that the body of the subprogram is provided
     by the compiler itself, usually by means of an efficient code
     sequence, and that the user does not supply an explicit body for
     it. In an application program, the pragma may be applied to the
     following sets of names:

        * Rotate_Left, Rotate_Right, Shift_Left, Shift_Right,
          Shift_Right_Arithmetic.  The corresponding subprogram
          declaration must have two formal parameters. The first one
          must be a signed integer type or a modular type with a binary
          modulus, and the second parameter must be of type Natural.
          The return type must be the same as the type of the first
          argument. The size of this type can only be 8, 16, 32, or 64.

        * Binary arithmetic operators: '+', '-', '*', '/'.  The
          corresponding operator declaration must have parameters and
          result type that have the same root numeric type (for
          example, all three are long_float types). This simplifies the
          definition of operations that use type checking to perform
          dimensional checks:

           type Distance is new Long_Float;
           type Time     is new Long_Float;
           type Velocity is new Long_Float;
           function "/" (D : Distance; T : Time)
             return Velocity;
           pragma Import (Intrinsic, "/");

         This common idiom is often programmed with a generic definition and an
         explicit body. The pragma makes it simpler to introduce such declarations.
         It incurs no overhead in compilation time or code size, because it is
         implemented as a single machine instruction.

        * General subprogram entities. This is used  to bind an Ada
          subprogram declaration to a compiler builtin by name with
          back-ends where such interfaces are available. A typical
          example is the set of `__builtin' functions exposed by the
          GCC back-end, as in the following example:

              function builtin_sqrt (F : Float) return Float;
              pragma Import (Intrinsic, builtin_sqrt, "__builtin_sqrtf");

          Most of the GCC builtins are accessible this way, and as for
          other import conventions (e.g. C), it is the user's
          responsibility to ensure that the Ada subprogram profile
          matches the underlying builtin expectations.

`Stdcall'
     This is relevant only to Windows implementations of GNAT, and
     specifies that the `Stdcall' calling sequence will be used, as
     defined by the NT API. Nevertheless, to ease building
     cross-platform bindings this convention will be handled as a `C'
     calling convention on non-Windows platforms.

`DLL'
     This is equivalent to `Stdcall'.

`Win32'
     This is equivalent to `Stdcall'.

`Stubbed'
     This is a special convention that indicates that the compiler
     should provide a stub body that raises `Program_Error'.

GNAT additionally provides a useful pragma `Convention_Identifier' that
can be used to parameterize conventions and allow additional synonyms
to be specified. For example if you have legacy code in which the
convention identifier Fortran77 was used for Fortran, you can use the
configuration pragma:

    pragma Convention_Identifier (Fortran77, Fortran);

And from now on the identifier Fortran77 may be used as a convention
identifier (for example in an `Import' pragma) with the same meaning as
Fortran.


File: gnat_ugn.info,  Node: Building Mixed Ada and C++ Programs,  Next: Generating Ada Bindings for C and C++ headers,  Prev: Calling Conventions,  Up: Mixed Language Programming

3.11.3 Building Mixed Ada and C++ Programs
------------------------------------------

A programmer inexperienced with mixed-language development may find that
building an application containing both Ada and C++ code can be a
challenge.  This section gives a few hints that should make this task
easier.

* Menu:

* Interfacing to C++::
* Linking a Mixed C++ & Ada Program::
* A Simple Example::
* Interfacing with C++ constructors::
* Interfacing with C++ at the Class Level::


File: gnat_ugn.info,  Node: Interfacing to C++,  Next: Linking a Mixed C++ & Ada Program,  Up: Building Mixed Ada and C++ Programs

3.11.3.1 Interfacing to C++
...........................

GNAT supports interfacing with the G++ compiler (or any C++ compiler
generating code that is compatible with the G++ Application Binary
Interface --see <http://www.codesourcery.com/archives/cxx-abi>).

Interfacing can be done at 3 levels: simple data, subprograms, and
classes. In the first two cases, GNAT offers a specific `Convention
C_Plus_Plus' (or `CPP') that behaves exactly like `Convention C'.
Usually, C++ mangles the names of subprograms. To generate proper
mangled names automatically, see *note Generating Ada Bindings for C
and C++ headers: 1b.).  This problem can also be addressed manually in
two ways:

   * by modifying the C++ code in order to force a C convention using
     the `extern "C"' syntax.

   * by figuring out the mangled name (using e.g. `nm') and using it as
     the Link_Name argument of the pragma import.

Interfacing at the class level can be achieved by using the GNAT
specific pragmas such as `CPP_Constructor'.  See the
`GNAT_Reference_Manual' for additional information.


File: gnat_ugn.info,  Node: Linking a Mixed C++ & Ada Program,  Next: A Simple Example,  Prev: Interfacing to C++,  Up: Building Mixed Ada and C++ Programs

3.11.3.2 Linking a Mixed C++ & Ada Program
..........................................

Usually the linker of the C++ development system must be used to link
mixed applications because most C++ systems will resolve elaboration
issues (such as calling constructors on global class instances)
transparently during the link phase. GNAT has been adapted to ease the
use of a foreign linker for the last phase. Three cases can be
considered:

   * Using GNAT and G++ (GNU C++ compiler) from the same GCC
     installation: The C++ linker can simply be called by using the C++
     specific driver called `g++'.

     Note that if the C++ code uses inline functions, you will need to
     compile your C++ code with the `-fkeep-inline-functions' switch in
     order to provide an existing function implementation that the Ada
     code can link with.

         $ g++ -c -fkeep-inline-functions file1.C
         $ g++ -c -fkeep-inline-functions file2.C
         $ gnatmake ada_unit -largs file1.o file2.o --LINK=g++

   * Using GNAT and G++ from two different GCC installations: If both
     compilers are on the :envvar`PATH`, the previous method may be
     used. It is important to note that environment variables such as `C_INCLUDE_PATH', `GCC_EXEC_PREFIX', `BINUTILS_ROOT',
     and `GCC_ROOT' will affect both compilers at the same time and may
     make one of the two compilers operate improperly if set during
     invocation of the wrong compiler.  It is also very important that
     the linker uses the proper `libgcc.a' GCC library - that is, the
     one from the C++ compiler installation. The implicit link command
     as suggested in the `gnatmake' command from the former example can
     be replaced by an explicit link command with the full-verbosity
     option in order to verify which library is used:

         $ gnatbind ada_unit
         $ gnatlink -v -v ada_unit file1.o file2.o --LINK=c++

     If there is a problem due to interfering environment variables, it
     can be worked around by using an intermediate script. The
     following example shows the proper script to use when GNAT has not
     been installed at its default location and g++ has been installed
     at its default location:

         $ cat ./my_script
         #!/bin/sh
         unset BINUTILS_ROOT
         unset GCC_ROOT
         c++ $*
         $ gnatlink -v -v ada_unit file1.o file2.o --LINK=./my_script

   * Using a non-GNU C++ compiler: The commands previously described
     can be used to insure that the C++ linker is used. Nonetheless,
     you need to add a few more parameters to the link command line,
     depending on the exception mechanism used.

     If the `setjmp/longjmp' exception mechanism is used, only the paths
     to the libgcc libraries are required:

         $ cat ./my_script
         #!/bin/sh
         CC $* `gcc -print-file-name=libgcc.a` `gcc -print-file-name=libgcc_eh.a`
         $ gnatlink ada_unit file1.o file2.o --LINK=./my_script

     where CC is the name of the non-GNU C++ compiler.

     If the `zero cost' exception mechanism is used, and the platform
     supports automatic registration of exception tables (e.g.,
     Solaris), paths to more objects are required:

         $ cat ./my_script
         #!/bin/sh
         CC `gcc -print-file-name=crtbegin.o` $* \\
         `gcc -print-file-name=libgcc.a` `gcc -print-file-name=libgcc_eh.a` \\
         `gcc -print-file-name=crtend.o`
         $ gnatlink ada_unit file1.o file2.o --LINK=./my_script

     If the "zero cost exception" mechanism is used, and the platform
     doesn't support automatic registration of exception tables (e.g.,
     HP-UX or AIX), the simple approach described above will not work
     and a pre-linking phase using GNAT will be necessary.

Another alternative is to use the `gprbuild' multi-language builder
which has a large knowledge base and knows how to link Ada and C++ code
together automatically in most cases.


File: gnat_ugn.info,  Node: A Simple Example,  Next: Interfacing with C++ constructors,  Prev: Linking a Mixed C++ & Ada Program,  Up: Building Mixed Ada and C++ Programs

3.11.3.3 A Simple Example
.........................

The following example, provided as part of the GNAT examples, shows how
to achieve procedural interfacing between Ada and C++ in both
directions. The C++ class A has two methods. The first method is
exported to Ada by the means of an extern C wrapper function. The
second method calls an Ada subprogram. On the Ada side, The C++ calls
are modelled by a limited record with a layout comparable to the C++
class. The Ada subprogram, in turn, calls the C++ method. So, starting
from the C++ main program, the process passes back and forth between
the two languages.

Here are the compilation commands:

    $ gnatmake -c simple_cpp_interface
    $ g++ -c cpp_main.C
    $ g++ -c ex7.C
    $ gnatbind -n simple_cpp_interface
    $ gnatlink simple_cpp_interface -o cpp_main --LINK=g++ -lstdc++ ex7.o cpp_main.o

Here are the corresponding sources:

    //cpp_main.C

    #include "ex7.h"

    extern "C" {
      void adainit (void);
      void adafinal (void);
      void method1 (A *t);
    }

    void method1 (A *t)
    {
      t->method1 ();
    }

    int main ()
    {
      A obj;
      adainit ();
      obj.method2 (3030);
      adafinal ();
    }

    //ex7.h

    class Origin {
     public:
      int o_value;
    };
    class A : public Origin {
     public:
      void method1 (void);
      void method2 (int v);
      A();
      int   a_value;
    };

    //ex7.C

    #include "ex7.h"
    #include <stdio.h>

    extern "C" { void ada_method2 (A *t, int v);}

    void A::method1 (void)
    {
      a_value = 2020;
      printf ("in A::method1, a_value = %d \\n",a_value);
    }

    void A::method2 (int v)
    {
       ada_method2 (this, v);
       printf ("in A::method2, a_value = %d \\n",a_value);
    }

    A::A(void)
    {
       a_value = 1010;
      printf ("in A::A, a_value = %d \\n",a_value);
    }

    -- simple_cpp_interface.ads
    with System;
    package Simple_Cpp_Interface is
       type A is limited
          record
             Vptr    : System.Address;
             O_Value : Integer;
             A_Value : Integer;
          end record;
       pragma Convention (C, A);

       procedure Method1 (This : in out A);
       pragma Import (C, Method1);

       procedure Ada_Method2 (This : in out A; V : Integer);
       pragma Export (C, Ada_Method2);

    end Simple_Cpp_Interface;

    -- simple_cpp_interface.adb
    package body Simple_Cpp_Interface is

       procedure Ada_Method2 (This : in out A; V : Integer) is
       begin
          Method1 (This);
          This.A_Value := V;
       end Ada_Method2;

    end Simple_Cpp_Interface;


File: gnat_ugn.info,  Node: Interfacing with C++ constructors,  Next: Interfacing with C++ at the Class Level,  Prev: A Simple Example,  Up: Building Mixed Ada and C++ Programs

3.11.3.4 Interfacing with C++ constructors
..........................................

In order to interface with C++ constructors GNAT provides the `pragma
CPP_Constructor' (see the `GNAT_Reference_Manual' for additional
information).  In this section we present some common uses of C++
constructors in mixed-languages programs in GNAT.

Let us assume that we need to interface with the following C++ class:

    class Root {
    public:
      int  a_value;
      int  b_value;
      virtual int Get_Value ();
      Root();              // Default constructor
      Root(int v);         // 1st non-default constructor
      Root(int v, int w);  // 2nd non-default constructor
    };

For this purpose we can write the following package spec (further
information on how to build this spec is available in *note Interfacing
with C++ at the Class Level: c7. and *note Generating Ada Bindings for
C and C++ headers: 1b.).

    with Interfaces.C; use Interfaces.C;
    package Pkg_Root is
      type Root is tagged limited record
         A_Value : int;
         B_Value : int;
      end record;
      pragma Import (CPP, Root);

      function Get_Value (Obj : Root) return int;
      pragma Import (CPP, Get_Value);

      function Constructor return Root;
      pragma Cpp_Constructor (Constructor, "_ZN4RootC1Ev");

      function Constructor (v : Integer) return Root;
      pragma Cpp_Constructor (Constructor, "_ZN4RootC1Ei");

      function Constructor (v, w : Integer) return Root;
      pragma Cpp_Constructor (Constructor, "_ZN4RootC1Eii");
    end Pkg_Root;

On the Ada side the constructor is represented by a function (whose
name is arbitrary) that returns the classwide type corresponding to the
imported C++ class. Although the constructor is described as a
function, it is typically a procedure with an extra implicit argument
(the object being initialized) at the implementation level. GNAT issues
the appropriate call, whatever it is, to get the object properly
initialized.

Constructors can only appear in the following contexts:

   * On the right side of an initialization of an object of type `T'.

   * On the right side of an initialization of a record component of
     type `T'.

   * In an Ada 2005 limited aggregate.

   * In an Ada 2005 nested limited aggregate.

   * In an Ada 2005 limited aggregate that initializes an object built
     in place by an extended return statement.

In a declaration of an object whose type is a class imported from C++,
either the default C++ constructor is implicitly called by GNAT, or
else the required C++ constructor must be explicitly called in the
expression that initializes the object. For example:

    Obj1 : Root;
    Obj2 : Root := Constructor;
    Obj3 : Root := Constructor (v => 10);
    Obj4 : Root := Constructor (30, 40);

The first two declarations are equivalent: in both cases the default C++
constructor is invoked (in the former case the call to the constructor
is implicit, and in the latter case the call is explicit in the object
declaration). `Obj3' is initialized by the C++ non-default constructor
that takes an integer argument, and `Obj4' is initialized by the
non-default C++ constructor that takes two integers.

Let us derive the imported C++ class in the Ada side. For example:

    type DT is new Root with record
       C_Value : Natural := 2009;
    end record;

In this case the components DT inherited from the C++ side must be
initialized by a C++ constructor, and the additional Ada components of
type DT are initialized by GNAT. The initialization of such an object
is done either by default, or by means of a function returning an
aggregate of type DT, or by means of an extension aggregate.

    Obj5 : DT;
    Obj6 : DT := Function_Returning_DT (50);
    Obj7 : DT := (Constructor (30,40) with C_Value => 50);

The declaration of `Obj5' invokes the default constructors: the C++
default constructor of the parent type takes care of the initialization
of the components inherited from Root, and GNAT takes care of the
default initialization of the additional Ada components of type DT
(that is, `C_Value' is initialized to value 2009). The order of
invocation of the constructors is consistent with the order of
elaboration required by Ada and C++. That is, the constructor of the
parent type is always called before the constructor of the derived type.

Let us now consider a record that has components whose type is imported
from C++. For example:

    type Rec1 is limited record
       Data1 : Root := Constructor (10);
       Value : Natural := 1000;
    end record;

    type Rec2 (D : Integer := 20) is limited record
       Rec   : Rec1;
       Data2 : Root := Constructor (D, 30);
    end record;

The initialization of an object of type `Rec2' will call the
non-default C++ constructors specified for the imported components.
For example:

    Obj8 : Rec2 (40);

Using Ada 2005 we can use limited aggregates to initialize an object
invoking C++ constructors that differ from those specified in the type
declarations. For example:

    Obj9 : Rec2 := (Rec => (Data1 => Constructor (15, 16),
                            others => <>),
                    others => <>);

The above declaration uses an Ada 2005 limited aggregate to initialize
`Obj9', and the C++ constructor that has two integer arguments is
invoked to initialize the `Data1' component instead of the constructor
specified in the declaration of type `Rec1'. In Ada 2005 the box in the
aggregate indicates that unspecified components are initialized using
the expression (if any) available in the component declaration. That
is, in this case discriminant `D' is initialized to value `20', `Value'
is initialized to value 1000, and the non-default C++ constructor that
handles two integers takes care of initializing component `Data2' with
values `20,30'.

In Ada 2005 we can use the extended return statement to build the Ada
equivalent to C++ non-default constructors. For example:

    function Constructor (V : Integer) return Rec2 is
    begin
       return Obj : Rec2 := (Rec => (Data1  => Constructor (V, 20),
                                     others => <>),
                             others => <>) do
          --  Further actions required for construction of
          --  objects of type Rec2
          ...
       end record;
    end Constructor;

In this example the extended return statement construct is used to
build in place the returned object whose components are initialized by
means of a limited aggregate. Any further action associated with the
constructor can be placed inside the construct.


File: gnat_ugn.info,  Node: Interfacing with C++ at the Class Level,  Prev: Interfacing with C++ constructors,  Up: Building Mixed Ada and C++ Programs

3.11.3.5 Interfacing with C++ at the Class Level
................................................

In this section we demonstrate the GNAT features for interfacing with
C++ by means of an example making use of Ada 2005 abstract interface
types. This example consists of a classification of animals; classes
have been used to model our main classification of animals, and
interfaces provide support for the management of secondary
classifications. We first demonstrate a case in which the types and
constructors are defined on the C++ side and imported from the Ada
side, and latter the reverse case.

The root of our derivation will be the `Animal' class, with a single
private attribute (the `Age' of the animal), a constructor, and two
public primitives to set and get the value of this attribute.

    class Animal {
     public:
       virtual void Set_Age (int New_Age);
       virtual int Age ();
       Animal() {Age_Count = 0;};
     private:
       int Age_Count;
    };

Abstract interface types are defined in C++ by means of classes with
pure virtual functions and no data members. In our example we will use
two interfaces that provide support for the common management of
`Carnivore' and `Domestic' animals:

    class Carnivore {
    public:
       virtual int Number_Of_Teeth () = 0;
    };

    class Domestic {
    public:
       virtual void Set_Owner (char* Name) = 0;
    };

Using these declarations, we can now say that a `Dog' is an animal that
is both Carnivore and Domestic, that is:

    class Dog : Animal, Carnivore, Domestic {
     public:
       virtual int  Number_Of_Teeth ();
       virtual void Set_Owner (char* Name);

       Dog(); // Constructor
     private:
       int  Tooth_Count;
       char *Owner;
    };

In the following examples we will assume that the previous declarations
are located in a file named `animals.h'. The following package
demonstrates how to import these C++ declarations from the Ada side:

    with Interfaces.C.Strings; use Interfaces.C.Strings;
    package Animals is
      type Carnivore is limited interface;
      pragma Convention (C_Plus_Plus, Carnivore);
      function Number_Of_Teeth (X : Carnivore)
         return Natural is abstract;

      type Domestic is limited interface;
      pragma Convention (C_Plus_Plus, Domestic);
      procedure Set_Owner
        (X    : in out Domestic;
         Name : Chars_Ptr) is abstract;

      type Animal is tagged limited record
        Age : Natural;
      end record;
      pragma Import (C_Plus_Plus, Animal);

      procedure Set_Age (X : in out Animal; Age : Integer);
      pragma Import (C_Plus_Plus, Set_Age);

      function Age (X : Animal) return Integer;
      pragma Import (C_Plus_Plus, Age);

      function New_Animal return Animal;
      pragma CPP_Constructor (New_Animal);
      pragma Import (CPP, New_Animal, "_ZN6AnimalC1Ev");

      type Dog is new Animal and Carnivore and Domestic with record
        Tooth_Count : Natural;
        Owner       : String (1 .. 30);
      end record;
      pragma Import (C_Plus_Plus, Dog);

      function Number_Of_Teeth (A : Dog) return Natural;
      pragma Import (C_Plus_Plus, Number_Of_Teeth);

      procedure Set_Owner (A : in out Dog; Name : Chars_Ptr);
      pragma Import (C_Plus_Plus, Set_Owner);

      function New_Dog return Dog;
      pragma CPP_Constructor (New_Dog);
      pragma Import (CPP, New_Dog, "_ZN3DogC2Ev");
    end Animals;

Thanks to the compatibility between GNAT run-time structures and the
C++ ABI, interfacing with these C++ classes is easy. The only
requirement is that all the primitives and components must be declared
exactly in the same order in the two languages.

Regarding the abstract interfaces, we must indicate to the GNAT
compiler by means of a `pragma Convention (C_Plus_Plus)', the
convention used to pass the arguments to the called primitives will be
the same as for C++. For the imported classes we use `pragma Import'
with convention `C_Plus_Plus' to indicate that they have been defined
on the C++ side; this is required because the dispatch table associated
with these tagged types will be built in the C++ side and therefore
will not contain the predefined Ada primitives which Ada would
otherwise expect.

As the reader can see there is no need to indicate the C++ mangled names
associated with each subprogram because it is assumed that all the
calls to these primitives will be dispatching calls. The only exception
is the constructor, which must be registered with the compiler by means
of `pragma CPP_Constructor' and needs to provide its associated C++
mangled name because the Ada compiler generates direct calls to it.

With the above packages we can now declare objects of type Dog on the
Ada side and dispatch calls to the corresponding subprograms on the C++
side. We can also extend the tagged type Dog with further fields and
primitives, and override some of its C++ primitives on the Ada side.
For example, here we have a type derivation defined on the Ada side
that inherits all the dispatching primitives of the ancestor from the
C++ side.

    with Animals; use Animals;
    package Vaccinated_Animals is
      type Vaccinated_Dog is new Dog with null record;
      function Vaccination_Expired (A : Vaccinated_Dog) return Boolean;
    end Vaccinated_Animals;

It is important to note that, because of the ABI compatibility, the
programmer does not need to add any further information to indicate
either the object layout or the dispatch table entry associated with
each dispatching operation.

Now let us define all the types and constructors on the Ada side and
export them to C++, using the same hierarchy of our previous example:

    with Interfaces.C.Strings;
    use Interfaces.C.Strings;
    package Animals is
      type Carnivore is limited interface;
      pragma Convention (C_Plus_Plus, Carnivore);
      function Number_Of_Teeth (X : Carnivore)
         return Natural is abstract;

      type Domestic is limited interface;
      pragma Convention (C_Plus_Plus, Domestic);
      procedure Set_Owner
        (X    : in out Domestic;
         Name : Chars_Ptr) is abstract;

      type Animal is tagged record
        Age : Natural;
      end record;
      pragma Convention (C_Plus_Plus, Animal);

      procedure Set_Age (X : in out Animal; Age : Integer);
      pragma Export (C_Plus_Plus, Set_Age);

      function Age (X : Animal) return Integer;
      pragma Export (C_Plus_Plus, Age);

      function New_Animal return Animal'Class;
      pragma Export (C_Plus_Plus, New_Animal);

      type Dog is new Animal and Carnivore and Domestic with record
        Tooth_Count : Natural;
        Owner       : String (1 .. 30);
      end record;
      pragma Convention (C_Plus_Plus, Dog);

      function Number_Of_Teeth (A : Dog) return Natural;
      pragma Export (C_Plus_Plus, Number_Of_Teeth);

      procedure Set_Owner (A : in out Dog; Name : Chars_Ptr);
      pragma Export (C_Plus_Plus, Set_Owner);

      function New_Dog return Dog'Class;
      pragma Export (C_Plus_Plus, New_Dog);
    end Animals;

Compared with our previous example the only differences are the use of
`pragma Convention' (instead of `pragma Import'), and the use of
`pragma Export' to indicate to the GNAT compiler that the primitives
will be available to C++. Thanks to the ABI compatibility, on the C++
side there is nothing else to be done; as explained above, the only
requirement is that all the primitives and components are declared in
exactly the same order.

For completeness, let us see a brief C++ main program that uses the
declarations available in `animals.h' (presented in our first example)
to import and use the declarations from the Ada side, properly
initializing and finalizing the Ada run-time system along the way:

    #include "animals.h"
    #include <iostream>
    using namespace std;

    void Check_Carnivore (Carnivore *obj) {...}
    void Check_Domestic (Domestic *obj)   {...}
    void Check_Animal (Animal *obj)       {...}
    void Check_Dog (Dog *obj)             {...}

    extern "C" {
      void adainit (void);
      void adafinal (void);
      Dog* new_dog ();
    }

    void test ()
    {
      Dog *obj = new_dog();  // Ada constructor
      Check_Carnivore (obj); // Check secondary DT
      Check_Domestic (obj);  // Check secondary DT
      Check_Animal (obj);    // Check primary DT
      Check_Dog (obj);       // Check primary DT
    }

    int main ()
    {
      adainit ();  test();  adafinal ();
      return 0;
    }


File: gnat_ugn.info,  Node: Generating Ada Bindings for C and C++ headers,  Next: Generating C Headers for Ada Specifications,  Prev: Building Mixed Ada and C++ Programs,  Up: Mixed Language Programming

3.11.4 Generating Ada Bindings for C and C++ headers
----------------------------------------------------

GNAT includes a binding generator for C and C++ headers which is
intended to do 95% of the tedious work of generating Ada specs from C
or C++ header files.

Note that this capability is not intended to generate 100% correct Ada
specs, and will is some cases require manual adjustments, although it
can often be used out of the box in practice.

Some of the known limitations include:

   * only very simple character constant macros are translated into Ada
     constants. Function macros (macros with arguments) are partially
     translated as comments, to be completed manually if needed.

   * some extensions (e.g. vector types) are not supported

   * pointers to pointers or complex structures are mapped to
     System.Address

   * identifiers with identical name (except casing) will generate
     compilation errors (e.g. `shm_get' vs `SHM_GET').

The code generated is using the Ada 2005 syntax, which makes it easier
to interface with other languages than previous versions of Ada.

* Menu:

* Running the Binding Generator::
* Generating Bindings for C++ Headers::
* Switches::


File: gnat_ugn.info,  Node: Running the Binding Generator,  Next: Generating Bindings for C++ Headers,  Up: Generating Ada Bindings for C and C++ headers

3.11.4.1 Running the Binding Generator
......................................

The binding generator is part of the `gcc' compiler and can be invoked
via the `-fdump-ada-spec' switch, which will generate Ada spec files
for the header files specified on the command line, and all header
files needed by these files transitively. For example:

    $ g++ -c -fdump-ada-spec -C /usr/include/time.h
    $ gcc -c -gnat05 *.ads

will generate, under GNU/Linux, the following files: `time_h.ads',
`bits_time_h.ads', `stddef_h.ads', `bits_types_h.ads' which correspond
to the files `/usr/include/time.h', `/usr/include/bits/time.h', etc...,
and will then compile in Ada 2005 mode these Ada specs.

The `-C' switch tells `gcc' to extract comments from headers, and will
attempt to generate corresponding Ada comments.

If you want to generate a single Ada file and not the transitive
closure, you can use instead the `-fdump-ada-spec-slim' switch.

You can optionally specify a parent unit, of which all generated units
will be children, using `-fada-spec-parent=<unit>'.

Note that we recommend when possible to use the `g++' driver to
generate bindings, even for most C headers, since this will in general
generate better Ada specs. For generating bindings for C++ headers, it
is mandatory to use the `g++' command, or `gcc -x c++' which is
equivalent in this case. If `g++' cannot work on your C headers because
of incompatibilities between C and C++, then you can fallback to `gcc'
instead.

For an example of better bindings generated from the C++ front-end, the
name of the parameters (when available) are actually ignored by the C
front-end. Consider the following C header:

    extern void foo (int variable);

with the C front-end, `variable' is ignored, and the above is handled
as:

    extern void foo (int);

generating a generic:

    procedure foo (param1 : int);

with the C++ front-end, the name is available, and we generate:

    procedure foo (variable : int);

In some cases, the generated bindings will be more complete or more
meaningful when defining some macros, which you can do via the `-D'
switch. This is for example the case with `Xlib.h' under GNU/Linux:

    $ g++ -c -fdump-ada-spec -DXLIB_ILLEGAL_ACCESS -C /usr/include/X11/Xlib.h

The above will generate more complete bindings than a straight call
without the `-DXLIB_ILLEGAL_ACCESS' switch.

In other cases, it is not possible to parse a header file in a
stand-alone manner, because other include files need to be included
first. In this case, the solution is to create a small header file
including the needed `#include' and possible `#define' directives. For
example, to generate Ada bindings for `readline/readline.h', you need
to first include `stdio.h', so you can create a file with the following
two lines in e.g. `readline1.h':

    #include <stdio.h>
    #include <readline/readline.h>

and then generate Ada bindings from this file:

    $ g++ -c -fdump-ada-spec readline1.h


File: gnat_ugn.info,  Node: Generating Bindings for C++ Headers,  Next: Switches,  Prev: Running the Binding Generator,  Up: Generating Ada Bindings for C and C++ headers

3.11.4.2 Generating Bindings for C++ Headers
............................................

Generating bindings for C++ headers is done using the same options,
always with the `g++' compiler. Note that generating Ada spec from C++
headers is a much more complex job and support for C++ headers is much
more limited that support for C headers. As a result, you will need to
modify the resulting bindings by hand more extensively when using C++
headers.

In this mode, C++ classes will be mapped to Ada tagged types,
constructors will be mapped using the `CPP_Constructor' pragma, and
when possible, multiple inheritance of abstract classes will be mapped
to Ada interfaces (see the `Interfacing to C++' section in the `GNAT
Reference Manual' for additional information on interfacing to C++).

For example, given the following C++ header file:

    class Carnivore {
    public:
       virtual int Number_Of_Teeth () = 0;
    };

    class Domestic {
    public:
       virtual void Set_Owner (char* Name) = 0;
    };

    class Animal {
    public:
      int Age_Count;
      virtual void Set_Age (int New_Age);
    };

    class Dog : Animal, Carnivore, Domestic {
     public:
      int  Tooth_Count;
      char *Owner;

      virtual int  Number_Of_Teeth ();
      virtual void Set_Owner (char* Name);

      Dog();
    };

The corresponding Ada code is generated:

    package Class_Carnivore is
      type Carnivore is limited interface;
      pragma Import (CPP, Carnivore);

      function Number_Of_Teeth (this : access Carnivore) return int is abstract;
    end;
    use Class_Carnivore;

    package Class_Domestic is
      type Domestic is limited interface;
      pragma Import (CPP, Domestic);

      procedure Set_Owner
        (this : access Domestic;
         Name : Interfaces.C.Strings.chars_ptr) is abstract;
    end;
    use Class_Domestic;

    package Class_Animal is
      type Animal is tagged limited record
        Age_Count : aliased int;
      end record;
      pragma Import (CPP, Animal);

      procedure Set_Age (this : access Animal; New_Age : int);
      pragma Import (CPP, Set_Age, "_ZN6Animal7Set_AgeEi");
    end;
    use Class_Animal;

    package Class_Dog is
      type Dog is new Animal and Carnivore and Domestic with record
        Tooth_Count : aliased int;
        Owner : Interfaces.C.Strings.chars_ptr;
      end record;
      pragma Import (CPP, Dog);

      function Number_Of_Teeth (this : access Dog) return int;
      pragma Import (CPP, Number_Of_Teeth, "_ZN3Dog15Number_Of_TeethEv");

      procedure Set_Owner
        (this : access Dog; Name : Interfaces.C.Strings.chars_ptr);
      pragma Import (CPP, Set_Owner, "_ZN3Dog9Set_OwnerEPc");

      function New_Dog return Dog;
      pragma CPP_Constructor (New_Dog);
      pragma Import (CPP, New_Dog, "_ZN3DogC1Ev");
    end;
    use Class_Dog;


File: gnat_ugn.info,  Node: Switches,  Prev: Generating Bindings for C++ Headers,  Up: Generating Ada Bindings for C and C++ headers

3.11.4.3 Switches
.................

`-fdump-ada-spec'
     Generate Ada spec files for the given header files transitively
     (including all header files that these headers depend upon).

`-fdump-ada-spec-slim'
     Generate Ada spec files for the header files specified on the
     command line only.

`-fada-spec-parent=`unit''
     Specifies that all files generated by `-fdump-ada-spec*' are to be
     child units of the specified parent unit.

`-C'
     Extract comments from headers and generate Ada comments in the Ada
     spec files.


File: gnat_ugn.info,  Node: Generating C Headers for Ada Specifications,  Prev: Generating Ada Bindings for C and C++ headers,  Up: Mixed Language Programming

3.11.5 Generating C Headers for Ada Specifications
--------------------------------------------------

GNAT includes a C header generator for Ada specifications which supports
Ada types that have a direct mapping to C types. This includes in
particular support for:

   * Scalar types

   * Constrained arrays

   * Records (untagged)

   * Composition of the above types

   * Constant declarations

   * Object declarations

   * Subprogram declarations

* Menu:

* Running the C Header Generator::


File: gnat_ugn.info,  Node: Running the C Header Generator,  Up: Generating C Headers for Ada Specifications

3.11.5.1 Running the C Header Generator
.......................................

The C header generator is part of the GNAT compiler and can be invoked
via the `-gnatceg' combination of switches, which will generate a `.h'
file corresponding to the given input file (Ada spec or body). Note that
only spec files are processed in any case, so giving a spec or a body
file as input is equivalent. For example:

    $ gcc -c -gnatceg pack1.ads

will generate a self-contained file called `pack1.h' including common
definitions from the Ada Standard package, followed by the definitions
included in `pack1.ads', as well as all the other units withed by this
file.

For instance, given the following Ada files:

    package Pack2 is
       type Int is range 1 .. 10;
    end Pack2;

    with Pack2;

    package Pack1 is
       type Rec is record
          Field1, Field2 : Pack2.Int;
       end record;

       Global : Rec := (1, 2);

       procedure Proc1 (R : Rec);
       procedure Proc2 (R : in out Rec);
    end Pack1;

The above `gcc' command will generate the following `pack1.h' file:

    /* Standard definitions skipped */
    #ifndef PACK2_ADS
    #define PACK2_ADS
    typedef short_short_integer pack2__TintB;
    typedef pack2__TintB pack2__int;
    #endif /* PACK2_ADS */

    #ifndef PACK1_ADS
    #define PACK1_ADS
    typedef struct _pack1__rec {
      pack2__int field1;
      pack2__int field2;
    } pack1__rec;
    extern pack1__rec pack1__global;
    extern void pack1__proc1(const pack1__rec r);
    extern void pack1__proc2(pack1__rec *r);
    #endif /* PACK1_ADS */

You can then `include' `pack1.h' from a C source file and use the types,
call subprograms, reference objects, and constants.


File: gnat_ugn.info,  Node: GNAT and Other Compilation Models,  Next: Using GNAT Files with External Tools,  Prev: Mixed Language Programming,  Up: The GNAT Compilation Model

3.12 GNAT and Other Compilation Models
======================================

This section compares the GNAT model with the approaches taken in other
environents, first the C/C++ model and then the mechanism that has been
used in other Ada systems, in particular those traditionally used for
Ada 83.

* Menu:

* Comparison between GNAT and C/C++ Compilation Models::
* Comparison between GNAT and Conventional Ada Library Models::


File: gnat_ugn.info,  Node: Comparison between GNAT and C/C++ Compilation Models,  Next: Comparison between GNAT and Conventional Ada Library Models,  Up: GNAT and Other Compilation Models

3.12.1 Comparison between GNAT and C/C++ Compilation Models
-----------------------------------------------------------

The GNAT model of compilation is close to the C and C++ models. You can
think of Ada specs as corresponding to header files in C. As in C, you
don't need to compile specs; they are compiled when they are used. The
Ada `with' is similar in effect to the `#include' of a C header.

One notable difference is that, in Ada, you may compile specs separately
to check them for semantic and syntactic accuracy. This is not always
possible with C headers because they are fragments of programs that have
less specific syntactic or semantic rules.

The other major difference is the requirement for running the binder,
which performs two important functions. First, it checks for
consistency. In C or C++, the only defense against assembling
inconsistent programs lies outside the compiler, in a makefile, for
example. The binder satisfies the Ada requirement that it be impossible
to construct an inconsistent program when the compiler is used in normal
mode.

The other important function of the binder is to deal with elaboration
issues. There are also elaboration issues in C++ that are handled
automatically. This automatic handling has the advantage of being
simpler to use, but the C++ programmer has no control over elaboration.
Where `gnatbind' might complain there was no valid order of
elaboration, a C++ compiler would simply construct a program that
malfunctioned at run time.


File: gnat_ugn.info,  Node: Comparison between GNAT and Conventional Ada Library Models,  Prev: Comparison between GNAT and C/C++ Compilation Models,  Up: GNAT and Other Compilation Models

3.12.2 Comparison between GNAT and Conventional Ada Library Models
------------------------------------------------------------------

This section is intended for Ada programmers who have used an Ada
compiler implementing the traditional Ada library model, as described
in the Ada Reference Manual.

In GNAT, there is no 'library' in the normal sense. Instead, the set of
source files themselves acts as the library. Compiling Ada programs does
not generate any centralized information, but rather an object file and
a ALI file, which are of interest only to the binder and linker.  In a
traditional system, the compiler reads information not only from the
source file being compiled, but also from the centralized library.
This means that the effect of a compilation depends on what has been
previously compiled. In particular:

   * When a unit is `with'ed, the unit seen by the compiler corresponds
     to the version of the unit most recently compiled into the library.

   * Inlining is effective only if the necessary body has already been
     compiled into the library.

   * Compiling a unit may obsolete other units in the library.

In GNAT, compiling one unit never affects the compilation of any other
units because the compiler reads only source files. Only changes to
source files can affect the results of a compilation. In particular:

   * When a unit is `with'ed, the unit seen by the compiler corresponds
     to the source version of the unit that is currently accessible to
     the compiler.

   * Inlining requires the appropriate source files for the package or
     subprogram bodies to be available to the compiler. Inlining is
     always effective, independent of the order in which units are
     compiled.

   * Compiling a unit never affects any other compilations. The editing
     of sources may cause previous compilations to be out of date if
     they depended on the source file being modified.

The most important result of these differences is that order of
compilation is never significant in GNAT. There is no situation in
which one is required to do one compilation before another. What shows
up as order of compilation requirements in the traditional Ada library
becomes, in GNAT, simple source dependencies; in other words, there is
only a set of rules saying what source files must be present when a
file is compiled.


File: gnat_ugn.info,  Node: Using GNAT Files with External Tools,  Prev: GNAT and Other Compilation Models,  Up: The GNAT Compilation Model

3.13 Using GNAT Files with External Tools
=========================================

This section explains how files that are produced by GNAT may be used
with tools designed for other languages.

* Menu:

* Using Other Utility Programs with GNAT::
* The External Symbol Naming Scheme of GNAT::


File: gnat_ugn.info,  Node: Using Other Utility Programs with GNAT,  Next: The External Symbol Naming Scheme of GNAT,  Up: Using GNAT Files with External Tools

3.13.1 Using Other Utility Programs with GNAT
---------------------------------------------

The object files generated by GNAT are in standard system format and in
particular the debugging information uses this format. This means
programs generated by GNAT can be used with existing utilities that
depend on these formats.

In general, any utility program that works with C will also often work
with Ada programs generated by GNAT. This includes software utilities
such as gprof (a profiling program), gdb (the FSF debugger), and
utilities such as Purify.


File: gnat_ugn.info,  Node: The External Symbol Naming Scheme of GNAT,  Prev: Using Other Utility Programs with GNAT,  Up: Using GNAT Files with External Tools

3.13.2 The External Symbol Naming Scheme of GNAT
------------------------------------------------

In order to interpret the output from GNAT, when using tools that are
originally intended for use with other languages, it is useful to
understand the conventions used to generate link names from the Ada
entity names.

All link names are in all lowercase letters. With the exception of
library procedure names, the mechanism used is simply to use the full
expanded Ada name with dots replaced by double underscores. For
example, suppose we have the following package spec:

    package QRS is
       MN : Integer;
    end QRS;

The variable `MN' has a full expanded Ada name of `QRS.MN', so the
corresponding link name is `qrs__mn'.  Of course if a `pragma Export'
is used this may be overridden:

    package Exports is
       Var1 : Integer;
       pragma Export (Var1, C, External_Name => "var1_name");
       Var2 : Integer;
       pragma Export (Var2, C, Link_Name => "var2_link_name");
    end Exports;

In this case, the link name for `Var1' is whatever link name the C
compiler would assign for the C function `var1_name'. This typically
would be either `var1_name' or `_var1_name', depending on operating
system conventions, but other possibilities exist. The link name for
`Var2' is `var2_link_name', and this is not operating system dependent.

One exception occurs for library level procedures. A potential ambiguity
arises between the required name `_main' for the C main program, and
the name we would otherwise assign to an Ada library level procedure
called `Main' (which might well not be the main program).

To avoid this ambiguity, we attach the prefix `_ada_' to such names. So
if we have a library level procedure such as:

    procedure Hello (S : String);

the external name of this procedure will be `_ada_hello'.


File: gnat_ugn.info,  Node: Building Executable Programs with GNAT,  Next: GNAT Project Manager,  Prev: The GNAT Compilation Model,  Up: Top

4 Building Executable Programs with GNAT
****************************************

This chapter describes first the gnatmake tool (*note Building with
gnatmake: 1d.), which automatically determines the set of sources
needed by an Ada compilation unit and executes the necessary
(re)compilations, binding and linking.  It also explains how to use
each tool individually: the compiler (gcc, see *note Compiling with
gcc: 1e.), binder (gnatbind, see *note Binding with gnatbind: 1f.), and
linker (gnatlink, see *note Linking with gnatlink: 20.)  to build
executable programs.  Finally, this chapter provides examples of how to
make use of the general GNU make mechanism in a GNAT context (see *note
Using the GNU make Utility: 21.).

* Menu:

* Building with gnatmake::
* Compiling with gcc::
* Compiler Switches::
* Binding with gnatbind::
* Linking with gnatlink::
* Using the GNU make Utility::


File: gnat_ugn.info,  Node: Building with gnatmake,  Next: Compiling with gcc,  Up: Building Executable Programs with GNAT

4.1 Building with `gnatmake'
============================

A typical development cycle when working on an Ada program consists of
the following steps:

  1. Edit some sources to fix bugs;

  2. Add enhancements;

  3. Compile all sources affected;

  4. Rebind and relink; and

  5. Test.

The third step in particular can be tricky, because not only do the
modified files have to be compiled, but any files depending on these
files must also be recompiled. The dependency rules in Ada can be quite
complex, especially in the presence of overloading, `use' clauses,
generics and inlined subprograms.

`gnatmake' automatically takes care of the third and fourth steps of
this process. It determines which sources need to be compiled, compiles
them, and binds and links the resulting object files.

Unlike some other Ada make programs, the dependencies are always
accurately recomputed from the new sources. The source based approach of
the GNAT compilation model makes this possible. This means that if
changes to the source program cause corresponding changes in
dependencies, they will always be tracked exactly correctly by
`gnatmake'.

Note that for advanced description of project structure, we recommend
creating a project file as explained in *note GNAT Project Manager: b.
and use the `gprbuild' tool which supports building with project files
and works similarly to `gnatmake'.

* Menu:

* Running gnatmake::
* Switches for gnatmake::
* Mode Switches for gnatmake::
* Notes on the Command Line::
* How gnatmake Works::
* Examples of gnatmake Usage::


File: gnat_ugn.info,  Node: Running gnatmake,  Next: Switches for gnatmake,  Up: Building with gnatmake

4.1.1 Running `gnatmake'
------------------------

The usual form of the `gnatmake' command is

    $ gnatmake [<switches>] <file_name> [<file_names>] [<mode_switches>]

The only required argument is one `file_name', which specifies a
compilation unit that is a main program. Several `file_names' can be
specified: this will result in several executables being built.  If
`switches' are present, they can be placed before the first
`file_name', between `file_names' or after the last `file_name'.  If
`mode_switches' are present, they must always be placed after the last
`file_name' and all `switches'.

If you are using standard file extensions (`.adb' and `.ads'), then the
extension may be omitted from the `file_name' arguments. However, if
you are using non-standard extensions, then it is required that the
extension be given. A relative or absolute directory path can be
specified in a `file_name', in which case, the input source file will
be searched for in the specified directory only. Otherwise, the input
source file will first be searched in the directory where `gnatmake'
was invoked and if it is not found, it will be search on the source
path of the compiler as described in *note Search Paths and the
Run-Time Library (RTL): 8e.

All `gnatmake' output (except when you specify `-M') is sent to
`stderr'. The output produced by the `-M' switch is sent to `stdout'.


File: gnat_ugn.info,  Node: Switches for gnatmake,  Next: Mode Switches for gnatmake,  Prev: Running gnatmake,  Up: Building with gnatmake

4.1.2 Switches for `gnatmake'
-----------------------------

You may specify any of the following switches to `gnatmake':

`--version'
     Display Copyright and version, then exit disregarding all other
     options.

`--help'
     If `--version' was not used, display usage, then exit disregarding
     all other options.

`--GCC=`compiler_name''
     Program used for compiling. The default is `gcc'. You need to use
     quotes around `compiler_name' if `compiler_name' contains spaces
     or other separator characters.  As an example `--GCC="foo -x  -y"'
     will instruct `gnatmake' to use `foo -x -y' as your compiler. A
     limitation of this syntax is that the name and path name of the
     executable itself must not include any embedded spaces. Note that
     switch `-c' is always inserted after your command name. Thus in the
     above example the compiler command that will be used by `gnatmake'
     will be `foo -c -x -y'. If several `--GCC=compiler_name' are used,
     only the last `compiler_name' is taken into account. However, all
     the additional switches are also taken into account. Thus,
     `--GCC="foo -x -y" --GCC="bar -z -t"' is equivalent to `--GCC="bar
     -x -y -z -t"'.

`--GNATBIND=`binder_name''
     Program used for binding. The default is `gnatbind'. You need to
     use quotes around `binder_name' if `binder_name' contains spaces
     or other separator characters.  As an example `--GNATBIND="bar -x
     -y"' will instruct `gnatmake' to use `bar -x -y' as your binder.
     Binder switches that are normally appended by `gnatmake' to
     `gnatbind' are now appended to the end of `bar -x -y'.  A
     limitation of this syntax is that the name and path name of the
     executable itself must not include any embedded spaces.

`--GNATLINK=`linker_name''
     Program used for linking. The default is `gnatlink'. You need to
     use quotes around `linker_name' if `linker_name' contains spaces
     or other separator characters.  As an example `--GNATLINK="lan -x
     -y"' will instruct `gnatmake' to use `lan -x -y' as your linker.
     Linker switches that are normally appended by `gnatmake' to
     `gnatlink' are now appended to the end of `lan -x -y'.  A
     limitation of this syntax is that the name and path name of the
     executable itself must not include any embedded spaces.

`--create-map-file'
     When linking an executable, create a map file. The name of the map
     file has the same name as the executable with extension ".map".

`--create-map-file=`mapfile''
     When linking an executable, create a map file with the specified
     name.

`--create-missing-dirs'
     When using project files (`-P`project''), automatically create
     missing object directories, library directories and exec
     directories.

`--single-compile-per-obj-dir'
     Disallow simultaneous compilations in the same object directory
     when project files are used.

`--subdirs=`subdir''
     Actual object directory of each project file is the subdirectory
     subdir of the object directory specified or defaulted in the
     project file.

`--unchecked-shared-lib-imports'
     By default, shared library projects are not allowed to import
     static library projects. When this switch is used on the command
     line, this restriction is relaxed.

`--source-info=`source info file''
     Specify a source info file. This switch is active only when
     project files are used. If the source info file is specified as a
     relative path, then it is relative to the object directory of the
     main project. If the source info file does not exist, then after
     the Project Manager has successfully parsed and processed the
     project files and found the sources, it creates the source info
     file. If the source info file already exists and can be read
     successfully, then the Project Manager will get all the needed
     information about the sources from the source info file and will
     not look for them. This reduces the time to process the project
     files, especially when looking for sources that take a long time.
     If the source info file exists but cannot be parsed successfully,
     the Project Manager will attempt to recreate it. If the Project
     Manager fails to create the source info file, a message is issued,
     but gnatmake does not fail. `gnatmake' "trusts" the source info
     file. This means that if the source files have changed (addition,
     deletion, moving to a different source directory), then the source
     info file need to be deleted and recreated.

`-a'
     Consider all files in the make process, even the GNAT internal
     system files (for example, the predefined Ada library files), as
     well as any locked files. Locked files are files whose ALI file is
     write-protected.  By default, `gnatmake' does not check these
     files, because the assumption is that the GNAT internal files are
     properly up to date, and also that any write protected ALI files
     have been properly installed. Note that if there is an
     installation problem, such that one of these files is not up to
     date, it will be properly caught by the binder.  You may have to
     specify this switch if you are working on GNAT itself. The switch
     `-a' is also useful in conjunction with `-f' if you need to
     recompile an entire application, including run-time files, using
     special configuration pragmas, such as a `Normalize_Scalars'
     pragma.

     By default `gnatmake -a' compiles all GNAT internal files with
     `gcc -c -gnatpg' rather than `gcc -c'.

`-b'
     Bind only. Can be combined with `-c' to do compilation and
     binding, but no link.  Can be combined with `-l' to do binding and
     linking. When not combined with `-c' all the units in the closure
     of the main program must have been previously compiled and must be
     up to date. The root unit specified by `file_name' may be given
     without extension, with the source extension or, if no GNAT
     Project File is specified, with the ALI file extension.

`-c'
     Compile only. Do not perform binding, except when `-b' is also
     specified. Do not perform linking, except if both `-b' and `-l'
     are also specified.  If the root unit specified by `file_name' is
     not a main unit, this is the default. Otherwise `gnatmake' will
     attempt binding and linking unless all objects are up to date and
     the executable is more recent than the objects.

`-C'
     Use a temporary mapping file. A mapping file is a way to
     communicate to the compiler two mappings: from unit names to file
     names (without any directory information) and from file names to
     path names (with full directory information). A mapping file can
     make the compiler's file searches faster, especially if there are
     many source directories, or the sources are read over a slow
     network connection. If `-P' is used, a mapping file is always
     used, so `-C' is unnecessary; in this case the mapping file is
     initially populated based on the project file. If `-C' is used
     without `-P', the mapping file is initially empty. Each invocation
     of the compiler will add any newly accessed sources to the mapping
     file.

`-C=`file''
     Use a specific mapping file. The file, specified as a path name
     (absolute or relative) by this switch, should already exist,
     otherwise the switch is ineffective. The specified mapping file
     will be communicated to the compiler.  This switch is not
     compatible with a project file (-P`file`) or with multiple
     compiling processes (-jnnn, when nnn is greater than 1).

`-d'
     Display progress for each source, up to date or not, as a single
     line:

         completed x out of y (zz%)

     If the file needs to be compiled this is displayed after the
     invocation of the compiler. These lines are displayed even in
     quiet output mode.

`-D `dir''
     Put all object files and ALI file in directory `dir'.  If the `-D'
     switch is not used, all object files and ALI files go in the
     current working directory.

     This switch cannot be used when using a project file.

`-eI`nnn''
     Indicates that the main source is a multi-unit source and the rank
     of the unit in the source file is nnn. nnn needs to be a positive
     number and a valid index in the source. This switch cannot be used
     when `gnatmake' is invoked for several mains.

`-eL'
     Follow all symbolic links when processing project files.  This
     should be used if your project uses symbolic links for files or
     directories, but is not needed in other cases.

     This also assumes that no directory matches the naming scheme for
     files (for instance that you do not have a directory called
     "sources.ads" when using the default GNAT naming scheme).

     When you do not have to use this switch (i.e., by default),
     gnatmake is able to save a lot of system calls (several per source
     file and object file), which can result in a significant speed up
     to load and manipulate a project file, especially when using
     source files from a remote system.

`-eS'
     Output the commands for the compiler, the binder and the linker on
     standard output, instead of standard error.

`-f'
     Force recompilations. Recompile all sources, even though some
     object files may be up to date, but don't recompile predefined or
     GNAT internal files or locked files (files with a write-protected
     ALI file), unless the `-a' switch is also specified.

`-F'
     When using project files, if some errors or warnings are detected
     during parsing and verbose mode is not in effect (no use of switch
     -v), then error lines start with the full path name of the project
     file, rather than its simple file name.

`-g'
     Enable debugging. This switch is simply passed to the compiler and
     to the linker.

`-i'
     In normal mode, `gnatmake' compiles all object files and ALI files
     into the current directory. If the `-i' switch is used, then
     instead object files and ALI files that already exist are
     overwritten in place. This means that once a large project is
     organized into separate directories in the desired manner, then
     `gnatmake' will automatically maintain and update this
     organization. If no ALI files are found on the Ada object path
     (see *note Search Paths and the Run-Time Library (RTL): 8e.), the
     new object and ALI files are created in the directory containing
     the source being compiled. If another organization is desired,
     where objects and sources are kept in different directories, a
     useful technique is to create dummy ALI files in the desired
     directories.  When detecting such a dummy file, `gnatmake' will be
     forced to recompile the corresponding source file, and it will be
     put the resulting object and ALI files in the directory where it
     found the dummy file.

`-j`n''
     Use `n' processes to carry out the (re)compilations. On a
     multiprocessor machine compilations will occur in parallel. If `n'
     is 0, then the maximum number of parallel compilations is the
     number of core processors on the platform. In the event of
     compilation errors, messages from various compilations might get
     interspersed (but `gnatmake' will give you the full ordered list
     of failing compiles at the end). If this is problematic, rerun the
     make process with n set to 1 to get a clean list of messages.

`-k'
     Keep going. Continue as much as possible after a compilation
     error. To ease the programmer's task in case of compilation
     errors, the list of sources for which the compile fails is given
     when `gnatmake' terminates.

     If `gnatmake' is invoked with several `file_names' and with this
     switch, if there are compilation errors when building an
     executable, `gnatmake' will not attempt to build the following
     executables.

`-l'
     Link only. Can be combined with `-b' to binding and linking.
     Linking will not be performed if combined with `-c' but not with
     `-b'.  When not combined with `-b' all the units in the closure of
     the main program must have been previously compiled and must be up
     to date, and the main program needs to have been bound.  The root
     unit specified by `file_name' may be given without extension, with
     the source extension or, if no GNAT Project File is specified,
     with the ALI file extension.

`-m'
     Specify that the minimum necessary amount of recompilations be
     performed. In this mode `gnatmake' ignores time stamp differences
     when the only modifications to a source file consist in
     adding/removing comments, empty lines, spaces or tabs. This means
     that if you have changed the comments in a source file or have
     simply reformatted it, using this switch will tell `gnatmake' not
     to recompile files that depend on it (provided other sources on
     which these files depend have undergone no semantic
     modifications). Note that the debugging information may be out of
     date with respect to the sources if the `-m' switch causes a
     compilation to be switched, so the use of this switch represents a
     trade-off between compilation time and accurate debugging
     information.

`-M'
     Check if all objects are up to date. If they are, output the object
     dependences to `stdout' in a form that can be directly exploited in
     a `Makefile'. By default, each source file is prefixed with its
     (relative or absolute) directory name. This name is whatever you
     specified in the various `-aI' and `-I' switches. If you use
     `gnatmake -M'  `-q' (see below), only the source file names,
     without relative paths, are output. If you just specify the  `-M'
     switch, dependencies of the GNAT internal system files are
     omitted. This is typically what you want. If you also specify the
     `-a' switch, dependencies of the GNAT internal files are also
     listed. Note that dependencies of the objects in external Ada
     libraries (see switch  `-aL`dir'' in the following list) are never
     reported.

`-n'
     Don't compile, bind, or link. Checks if all objects are up to date.
     If they are not, the full name of the first file that needs to be
     recompiled is printed.  Repeated use of this option, followed by
     compiling the indicated source file, will eventually result in
     recompiling all required units.

`-o `exec_name''
     Output executable name. The name of the final executable program
     will be `exec_name'. If the `-o' switch is omitted the default
     name for the executable will be the name of the input file in
     appropriate form for an executable file on the host system.

     This switch cannot be used when invoking `gnatmake' with several
     `file_names'.

`-p'
     Same as `--create-missing-dirs'

`-P`project''
     Use project file `project'. Only one such switch can be used.
     *note gnatmake and Project Files: e4.

`-q'
     Quiet. When this flag is not set, the commands carried out by
     `gnatmake' are displayed.

`-s'
     Recompile if compiler switches have changed since last compilation.
     All compiler switches but -I and -o are taken into account in the
     following way: orders between different 'first letter' switches
     are ignored, but orders between same switches are taken into
     account. For example, `-O -O2' is different than `-O2 -O', but `-g
     -O' is equivalent to `-O -g'.

     This switch is recommended when Integrated Preprocessing is used.

`-u'
     Unique. Recompile at most the main files. It implies -c. Combined
     with -f, it is equivalent to calling the compiler directly. Note
     that using -u with a project file and no main has a special meaning
     (*note Project Files and Main Subprograms: e5.).

`-U'
     When used without a project file or with one or several mains on
     the command line, is equivalent to -u. When used with a project
     file and no main on the command line, all sources of all project
     files are checked and compiled if not up to date, and libraries
     are rebuilt, if necessary.

`-v'
     Verbose. Display the reason for all recompilations `gnatmake'
     decides are necessary, with the highest verbosity level.

`-vl'
     Verbosity level Low. Display fewer lines than in verbosity Medium.

`-vm'
     Verbosity level Medium. Potentially display fewer lines than in
     verbosity High.

`-vh'
     Verbosity level High. Equivalent to -v.

`-vP`x''
     Indicate the verbosity of the parsing of GNAT project files.  See
     *note Switches Related to Project Files: e6.

`-x'
     Indicate that sources that are not part of any Project File may be
     compiled.  Normally, when using Project Files, only sources that
     are part of a Project File may be compile. When this switch is
     used, a source outside of all Project Files may be compiled. The
     ALI file and the object file will be put in the object directory
     of the main Project. The compilation switches used will only be
     those specified on the command line. Even when `-x' is used, mains
     specified on the command line need to be sources of a project file.

`-X`name'=`value''
     Indicate that external variable `name' has the value `value'.  The
     Project Manager will use this value for occurrences of
     `external(name)' when parsing the project file.  *note Switches
     Related to Project Files: e6.

`-z'
     No main subprogram. Bind and link the program even if the unit name
     given on the command line is a package name. The resulting
     executable will execute the elaboration routines of the package
     and its closure, then the finalization routines.

GCC switches
............

Any uppercase or multi-character switch that is not a `gnatmake' switch
is passed to `gcc' (e.g., `-O', `-gnato,' etc.)

Source and library search path switches
.......................................

`-aI`dir''
     When looking for source files also look in directory `dir'.  The
     order in which source files search is undertaken is described in
     *note Search Paths and the Run-Time Library (RTL): 8e.

`-aL`dir''
     Consider `dir' as being an externally provided Ada library.
     Instructs `gnatmake' to skip compilation units whose `.ALI' files
     have been located in directory `dir'. This allows you to have
     missing bodies for the units in `dir' and to ignore out of date
     bodies for the same units. You still need to specify the location
     of the specs for these units by using the switches `-aI`dir''  or
     `-I`dir''.  Note: this switch is provided for compatibility with
     previous versions of `gnatmake'. The easier method of causing
     standard libraries to be excluded from consideration is to
     write-protect the corresponding ALI files.

`-aO`dir''
     When searching for library and object files, look in directory
     `dir'. The order in which library files are searched is described
     in *note Search Paths for gnatbind: 91.

`-A`dir''
     Equivalent to `-aL`dir'' `-aI`dir''.

`-I`dir''
     Equivalent to `-aO`dir' -aI`dir''.

`-I-'
     Do not look for source files in the directory containing the source
     file named in the command line.  Do not look for ALI or object
     files in the directory where `gnatmake' was invoked.

`-L`dir''
     Add directory `dir' to the list of directories in which the linker
     will search for libraries. This is equivalent to `-largs'
     `-L`dir''.  Furthermore, under Windows, the sources pointed to by
     the libraries path set in the registry are not searched for.

`-nostdinc'
     Do not look for source files in the system default directory.

`-nostdlib'
     Do not look for library files in the system default directory.

`--RTS=`rts-path''
     Specifies the default location of the runtime library. GNAT looks
     for the runtime in the following directories, and stops as soon as
     a valid runtime is found (`adainclude' or `ada_source_path', and
     `adalib' or `ada_object_path' present):

        * `<current directory>/$rts_path'

        * `<default-search-dir>/$rts_path'

        * `<default-search-dir>/rts-$rts_path'

        * The selected path is handled like a normal RTS path.


File: gnat_ugn.info,  Node: Mode Switches for gnatmake,  Next: Notes on the Command Line,  Prev: Switches for gnatmake,  Up: Building with gnatmake

4.1.3 Mode Switches for `gnatmake'
----------------------------------

The mode switches (referred to as `mode_switches') allow the inclusion
of switches that are to be passed to the compiler itself, the binder or
the linker. The effect of a mode switch is to cause all subsequent
switches up to the end of the switch list, or up to the next mode
switch, to be interpreted as switches to be passed on to the designated
component of GNAT.

`-cargs `switches''
     Compiler switches. Here `switches' is a list of switches that are
     valid switches for `gcc'. They will be passed on to all compile
     steps performed by `gnatmake'.

`-bargs `switches''
     Binder switches. Here `switches' is a list of switches that are
     valid switches for `gnatbind'. They will be passed on to all bind
     steps performed by `gnatmake'.

`-largs `switches''
     Linker switches. Here `switches' is a list of switches that are
     valid switches for `gnatlink'. They will be passed on to all link
     steps performed by `gnatmake'.

`-margs `switches''
     Make switches. The switches are directly interpreted by `gnatmake',
     regardless of any previous occurrence of `-cargs', `-bargs' or
     `-largs'.


File: gnat_ugn.info,  Node: Notes on the Command Line,  Next: How gnatmake Works,  Prev: Mode Switches for gnatmake,  Up: Building with gnatmake

4.1.4 Notes on the Command Line
-------------------------------

This section contains some additional useful notes on the operation of
the `gnatmake' command.

   * If `gnatmake' finds no ALI files, it recompiles the main program
     and all other units required by the main program.  This means that
     `gnatmake' can be used for the initial compile, as well as during
     subsequent steps of the development cycle.

   * If you enter `gnatmake foo.adb', where `foo' is a subunit or body
     of a generic unit, `gnatmake' recompiles `foo.adb' (because it
     finds no ALI) and stops, issuing a warning.

   * In `gnatmake' the switch `-I' is used to specify both source and
     library file paths. Use `-aI' instead if you just want to specify
     source paths only and `-aO' if you want to specify library paths
     only.

   * `gnatmake' will ignore any files whose ALI file is write-protected.
     This may conveniently be used to exclude standard libraries from
     consideration and in particular it means that the use of the `-f'
     switch will not recompile these files unless `-a' is also
     specified.

   * `gnatmake' has been designed to make the use of Ada libraries
     particularly convenient. Assume you have an Ada library organized
     as follows: `obj-dir' contains the objects and ALI files for of
     your Ada compilation units, whereas `include-dir' contains the
     specs of these units, but no bodies. Then to compile a unit stored
     in `main.adb', which uses this Ada library you would just type:

         $ gnatmake -aI`include-dir`  -aL`obj-dir`  main

   * Using `gnatmake' along with the `-m (minimal recompilation)'
     switch provides a mechanism for avoiding unnecessary
     recompilations. Using this switch, you can update the
     comments/format of your source files without having to recompile
     everything. Note, however, that adding or deleting lines in a
     source files may render its debugging info obsolete. If the file
     in question is a spec, the impact is rather limited, as that
     debugging info will only be useful during the elaboration phase of
     your program. For bodies the impact can be more significant. In
     all events, your debugger will warn you if a source file is more
     recent than the corresponding object, and alert you to the fact
     that the debugging information may be out of date.


File: gnat_ugn.info,  Node: How gnatmake Works,  Next: Examples of gnatmake Usage,  Prev: Notes on the Command Line,  Up: Building with gnatmake

4.1.5 How `gnatmake' Works
--------------------------

Generally `gnatmake' automatically performs all necessary
recompilations and you don't need to worry about how it works. However,
it may be useful to have some basic understanding of the `gnatmake'
approach and in particular to understand how it uses the results of
previous compilations without incorrectly depending on them.

First a definition: an object file is considered `up to date' if the
corresponding ALI file exists and if all the source files listed in the
dependency section of this ALI file have time stamps matching those in
the ALI file. This means that neither the source file itself nor any
files that it depends on have been modified, and hence there is no need
to recompile this file.

`gnatmake' works by first checking if the specified main unit is up to
date. If so, no compilations are required for the main unit. If not,
`gnatmake' compiles the main program to build a new ALI file that
reflects the latest sources. Then the ALI file of the main unit is
examined to find all the source files on which the main program depends,
and `gnatmake' recursively applies the above procedure on all these
files.

This process ensures that `gnatmake' only trusts the dependencies in an
existing ALI file if they are known to be correct. Otherwise it always
recompiles to determine a new, guaranteed accurate set of dependencies.
As a result the program is compiled 'upside down' from what may be more
familiar as the required order of compilation in some other Ada
systems. In particular, clients are compiled before the units on which
they depend. The ability of GNAT to compile in any order is critical in
allowing an order of compilation to be chosen that guarantees that
`gnatmake' will recompute a correct set of new dependencies if
necessary.

When invoking `gnatmake' with several `file_names', if a unit is
imported by several of the executables, it will be recompiled at most
once.

Note: when using non-standard naming conventions (*note Using Other
File Names: 37.), changing through a configuration pragmas file the
version of a source and invoking `gnatmake' to recompile may have no
effect, if the previous version of the source is still accessible by
`gnatmake'. It may be necessary to use the switch -f.


File: gnat_ugn.info,  Node: Examples of gnatmake Usage,  Prev: How gnatmake Works,  Up: Building with gnatmake

4.1.6 Examples of `gnatmake' Usage
----------------------------------

`gnatmake hello.adb'
     Compile all files necessary to bind and link the main program
     `hello.adb' (containing unit `Hello') and bind and link the
     resulting object files to generate an executable file `hello'.

`gnatmake main1 main2 main3'
     Compile all files necessary to bind and link the main programs
     `main1.adb' (containing unit `Main1'), `main2.adb' (containing
     unit `Main2') and `main3.adb' (containing unit `Main3') and bind
     and link the resulting object files to generate three executable
     files `main1', `main2'  and `main3'.

`gnatmake -q Main_Unit -cargs -O2 -bargs -l'
     Compile all files necessary to bind and link the main program unit
     `Main_Unit' (from file `main_unit.adb'). All compilations will be
     done with optimization level 2 and the order of elaboration will be
     listed by the binder. `gnatmake' will operate in quiet mode, not
     displaying commands it is executing.


File: gnat_ugn.info,  Node: Compiling with gcc,  Next: Compiler Switches,  Prev: Building with gnatmake,  Up: Building Executable Programs with GNAT

4.2 Compiling with `gcc'
========================

This section discusses how to compile Ada programs using the `gcc'
command. It also describes the set of switches that can be used to
control the behavior of the compiler.

* Menu:

* Compiling Programs::
* Search Paths and the Run-Time Library (RTL): Search Paths and the Run-Time Library RTL.
* Order of Compilation Issues::
* Examples::


File: gnat_ugn.info,  Node: Compiling Programs,  Next: Search Paths and the Run-Time Library RTL,  Up: Compiling with gcc

4.2.1 Compiling Programs
------------------------

The first step in creating an executable program is to compile the units
of the program using the `gcc' command. You must compile the following
files:

   * the body file (`.adb') for a library level subprogram or generic
     subprogram

   * the spec file (`.ads') for a library level package or generic
     package that has no body

   * the body file (`.adb') for a library level package or generic
     package that has a body

You need `not' compile the following files

   * the spec of a library unit which has a body

   * subunits

because they are compiled as part of compiling related units. GNAT
package specs when the corresponding body is compiled, and subunits
when the parent is compiled.

If you attempt to compile any of these files, you will get one of the
following error messages (where `fff' is the name of the file you
compiled):

         cannot generate code for file `fff` (package spec)
         to check package spec, use -gnatc

         cannot generate code for file `fff` (missing subunits)
         to check parent unit, use -gnatc

         cannot generate code for file `fff` (subprogram spec)
         to check subprogram spec, use -gnatc

         cannot generate code for file `fff` (subunit)
         to check subunit, use -gnatc

As indicated by the above error messages, if you want to submit one of
these files to the compiler to check for correct semantics without
generating code, then use the `-gnatc' switch.

The basic command for compiling a file containing an Ada unit is:

    $ gcc -c [switches] <file name>

where `file name' is the name of the Ada file (usually having an
extension `.ads' for a spec or `.adb' for a body).  You specify the
`-c' switch to tell `gcc' to compile, but not link, the file.  The
result of a successful compilation is an object file, which has the
same name as the source file but an extension of `.o' and an Ada
Library Information (ALI) file, which also has the same name as the
source file, but with `.ali' as the extension. GNAT creates these two
output files in the current directory, but you may specify a source
file in any directory using an absolute or relative path specification
containing the directory information.

`gcc' is actually a driver program that looks at the extensions of the
file arguments and loads the appropriate compiler. For example, the GNU
C compiler is `cc1', and the Ada compiler is `gnat1'.  These programs
are in directories known to the driver program (in some configurations
via environment variables you set), but need not be in your path. The
`gcc' driver also calls the assembler and any other utilities needed to
complete the generation of the required object files.

It is possible to supply several file names on the same `gcc' command.
This causes `gcc' to call the appropriate compiler for each file. For
example, the following command lists two separate files to be compiled:

    $ gcc -c x.adb y.adb

calls `gnat1' (the Ada compiler) twice to compile `x.adb' and `y.adb'.
The compiler generates two object files `x.o' and `y.o' and the two ALI
files `x.ali' and `y.ali'.

Any switches apply to all the files listed, see *note Compiler
Switches: f2. for a list of available `gcc' switches.


File: gnat_ugn.info,  Node: Search Paths and the Run-Time Library RTL,  Next: Order of Compilation Issues,  Prev: Compiling Programs,  Up: Compiling with gcc

4.2.2 Search Paths and the Run-Time Library (RTL)
-------------------------------------------------

With the GNAT source-based library system, the compiler must be able to
find source files for units that are needed by the unit being compiled.
Search paths are used to guide this process.

The compiler compiles one source file whose name must be given
explicitly on the command line. In other words, no searching is done
for this file. To find all other source files that are needed (the most
common being the specs of units), the compiler examines the following
directories, in the following order:

   * The directory containing the source file of the main unit being
     compiled (the file name on the command line).

   * Each directory named by an `-I' switch given on the `gcc' command
     line, in the order given.

   * Each of the directories listed in the text file whose name is given
     by the `ADA_PRJ_INCLUDE_FILE' environment variable.  `ADA_PRJ_INCLUDE_FILE'
     is normally set by gnatmake or by the gnat driver when project
     files are used. It should not normally be set by other means.

   * Each of the directories listed in the value of the `ADA_INCLUDE_PATH'
     environment variable.  Construct this value exactly as the `PATH'
     environment variable: a list of directory names separated by
     colons (semicolons when working with the NT version).

   * The content of the `ada_source_path' file which is part of the GNAT
     installation tree and is used to store standard libraries such as
     the GNAT Run Time Library (RTL) source files.  *note Installing a
     library: 8b.

Specifying the switch `-I-' inhibits the use of the directory
containing the source file named in the command line. You can still
have this directory on your search path, but in this case it must be
explicitly requested with a `-I' switch.

Specifying the switch `-nostdinc' inhibits the search of the default
location for the GNAT Run Time Library (RTL) source files.

The compiler outputs its object files and ALI files in the current
working directory.  Caution: The object file can be redirected with the
`-o' switch; however, `gcc' and `gnat1' have not been coordinated on
this so the `ALI' file will not go to the right place. Therefore, you
should avoid using the `-o' switch.

The packages `Ada', `System', and `Interfaces' and their children make
up the GNAT RTL, together with the simple `System.IO' package used in
the `"Hello World"' example. The sources for these units are needed by
the compiler and are kept together in one directory. Not all of the
bodies are needed, but all of the sources are kept together anyway. In
a normal installation, you need not specify these directory names when
compiling or binding. Either the environment variables or the built-in
defaults cause these files to be found.

In addition to the language-defined hierarchies (`System', `Ada' and
`Interfaces'), the GNAT distribution provides a fourth hierarchy,
consisting of child units of `GNAT'. This is a collection of generally
useful types, subprograms, etc. See the `GNAT_Reference_Manual' for
further details.

Besides simplifying access to the RTL, a major use of search paths is
in compiling sources from multiple directories. This can make
development environments much more flexible.


File: gnat_ugn.info,  Node: Order of Compilation Issues,  Next: Examples,  Prev: Search Paths and the Run-Time Library RTL,  Up: Compiling with gcc

4.2.3 Order of Compilation Issues
---------------------------------

If, in our earlier example, there was a spec for the `hello' procedure,
it would be contained in the file `hello.ads'; yet this file would not
have to be explicitly compiled. This is the result of the model we
chose to implement library management. Some of the consequences of this
model are as follows:

   * There is no point in compiling specs (except for package specs
     with no bodies) because these are compiled as needed by clients. If
     you attempt a useless compilation, you will receive an error
     message.  It is also useless to compile subunits because they are
     compiled as needed by the parent.

   * There are no order of compilation requirements: performing a
     compilation never obsoletes anything. The only way you can obsolete
     something and require recompilations is to modify one of the
     source files on which it depends.

   * There is no library as such, apart from the ALI files (*note The
     Ada Library Information Files: 44, for information on the format
     of these files). For now we find it convenient to create separate
     ALI files, but eventually the information therein may be
     incorporated into the object file directly.

   * When you compile a unit, the source files for the specs of all
     units that it `with's, all its subunits, and the bodies of any
     generics it instantiates must be available (reachable by the
     search-paths mechanism described above), or you will receive a
     fatal error message.


File: gnat_ugn.info,  Node: Examples,  Prev: Order of Compilation Issues,  Up: Compiling with gcc

4.2.4 Examples
--------------

The following are some typical Ada compilation command line examples:

    $ gcc -c xyz.adb

Compile body in file `xyz.adb' with all default options.

    $ gcc -c -O2 -gnata xyz-def.adb

Compile the child unit package in file `xyz-def.adb' with extensive
optimizations, and pragma `Assert'/`Debug' statements enabled.

    $ gcc -c -gnatc abc-def.adb

Compile the subunit in file `abc-def.adb' in semantic-checking-only
mode.


File: gnat_ugn.info,  Node: Compiler Switches,  Next: Binding with gnatbind,  Prev: Compiling with gcc,  Up: Building Executable Programs with GNAT

4.3 Compiler Switches
=====================

The `gcc' command accepts switches that control the compilation
process. These switches are fully described in this section: first an
alphabetical listing of all switches with a brief description, and then
functionally grouped sets of switches with more detailed information.

More switches exist for GCC than those documented here, especially for
specific targets. However, their use is not recommended as they may
change code generation in ways that are incompatible with the Ada
run-time library, or can cause inconsistencies between compilation
units.

* Menu:

* Alphabetical List of All Switches::
* Output and Error Message Control::
* Warning Message Control::
* Debugging and Assertion Control::
* Validity Checking::
* Style Checking::
* Run-Time Checks::
* Using gcc for Syntax Checking::
* Using gcc for Semantic Checking::
* Compiling Different Versions of Ada::
* Character Set Control::
* File Naming Control::
* Subprogram Inlining Control::
* Auxiliary Output Control::
* Debugging Control::
* Exception Handling Control::
* Units to Sources Mapping Files::
* Code Generation Control::


File: gnat_ugn.info,  Node: Alphabetical List of All Switches,  Next: Output and Error Message Control,  Up: Compiler Switches

4.3.1 Alphabetical List of All Switches
---------------------------------------

`-b `target''
     Compile your program to run on `target', which is the name of a
     system configuration. You must have a GNAT cross-compiler built if
     `target' is not the same as your host system.

`-B`dir''
     Load compiler executables (for example, `gnat1', the Ada compiler)
     from `dir' instead of the default location. Only use this switch
     when multiple versions of the GNAT compiler are available.  See
     the "Options for Directory Search" section in the `Using the GNU
     Compiler Collection (GCC)' manual for further details.  You would
     normally use the `-b' or `-V' switch instead.

`-c'
     Compile. Always use this switch when compiling Ada programs.

     Note: for some other languages when using `gcc', notably in the
     case of C and C++, it is possible to use use `gcc' without a `-c'
     switch to compile and link in one step. In the case of GNAT, you
     cannot use this approach, because the binder must be run and `gcc'
     cannot be used to run the GNAT binder.

`-fcallgraph-info[=su,da]'
     Makes the compiler output callgraph information for the program,
     on a per-file basis. The information is generated in the VCG
     format.  It can be decorated with additional, per-node and/or
     per-edge information, if a list of comma-separated markers is
     additionally specified. When the `su' marker is specified, the
     callgraph is decorated with stack usage information; it is
     equivalent to `-fstack-usage'. When the `da' marker is specified,
     the callgraph is decorated with information about dynamically
     allocated objects.

`-fdump-scos'
     Generates SCO (Source Coverage Obligation) information in the ALI
     file.  This information is used by advanced coverage tools. See
     unit `SCOs' in the compiler sources for details in files
     `scos.ads' and `scos.adb'.

`-fdump-xref'
     Generates cross reference information in GLI files for C and C++
     sources.  The GLI files have the same syntax as the ALI files for
     Ada, and can be used for source navigation in IDEs and on the
     command line using e.g. gnatxref and the `-ext=gli' switch.

`-flto[=`n']'
     Enables Link Time Optimization. This switch must be used in
     conjunction with the traditional `-Ox' switches and instructs the
     compiler to defer most optimizations until the link stage. The
     advantage of this approach is that the compiler can do a
     whole-program analysis and choose the best interprocedural
     optimization strategy based on a complete view of the program,
     instead of a fragmentary view with the usual approach.  This can
     also speed up the compilation of big programs and reduce the size
     of the executable, compared with a traditional per-unit compilation
     with inlining across modules enabled by the `-gnatn' switch.  The
     drawback of this approach is that it may require more memory and
     that the debugging information generated by -g with it might be
     hardly usable.  The switch, as well as the accompanying `-Ox'
     switches, must be specified both for the compilation and the link
     phases.  If the `n' parameter is specified, the optimization and
     final code generation at link time are executed using `n' parallel
     jobs by means of an installed `make' program.

`-fno-inline'
     Suppresses all inlining, unless requested with pragma
     `Inline_Always'. The effect is enforced regardless of other
     optimization or inlining switches.  Note that inlining can also be
     suppressed on a finer-grained basis with pragma `No_Inline'.

`-fno-inline-functions'
     Suppresses automatic inlining of subprograms, which is enabled if
     `-O3' is used.

`-fno-inline-small-functions'
     Suppresses automatic inlining of small subprograms, which is
     enabled if `-O2' is used.

`-fno-inline-functions-called-once'
     Suppresses inlining of subprograms local to the unit and called
     once from within it, which is enabled if `-O1' is used.

`-fno-ivopts'
     Suppresses high-level loop induction variable optimizations, which
     are enabled if `-O1' is used. These optimizations are generally
     profitable but, for some specific cases of loops with numerous uses
     of the iteration variable that follow a common pattern, they may
     end up destroying the regularity that could be exploited at a
     lower level and thus producing inferior code.

`-fno-strict-aliasing'
     Causes the compiler to avoid assumptions regarding non-aliasing of
     objects of different types. See *note Optimization and Strict
     Aliasing: fb. for details.

`-fno-strict-overflow'
     Causes the compiler to avoid assumptions regarding the rules of
     signed integer overflow. These rules specify that signed integer
     overflow will result in a Constraint_Error exception at run time
     and are enforced in default mode by the compiler, so this switch
     should not be necessary in normal operating mode. It might be
     useful in conjunction with `-gnato0' for very peculiar cases of
     low-level programming.

`-fstack-check'
     Activates stack checking.  See *note Stack Overflow Checking: fc.
     for details.

`-fstack-usage'
     Makes the compiler output stack usage information for the program,
     on a per-subprogram basis. See *note Static Stack Usage Analysis:
     fd. for details.

`-g'
     Generate debugging information. This information is stored in the
     object file and copied from there to the final executable file by
     the linker, where it can be read by the debugger. You must use the
     `-g' switch if you plan on using the debugger.

`-gnat05'
     Allow full Ada 2005 features.

`-gnat12'
     Allow full Ada 2012 features.

`-gnat2005'
     Allow full Ada 2005 features (same as `-gnat05')

`-gnat2012'
     Allow full Ada 2012 features (same as `-gnat12')

`-gnat83'
     Enforce Ada 83 restrictions.

`-gnat95'
     Enforce Ada 95 restrictions.

     Note: for compatibility with some Ada 95 compilers which support
     only the `overriding' keyword of Ada 2005, the `-gnatd.D' switch
     can be used along with `-gnat95' to achieve a similar effect with
     GNAT.

     `-gnatd.D' instructs GNAT to consider `overriding' as a keyword
     and handle its associated semantic checks, even in Ada 95 mode.

`-gnata'
     Assertions enabled. `Pragma Assert' and `pragma Debug' to be
     activated. Note that these pragmas can also be controlled using the
     configuration pragmas `Assertion_Policy' and `Debug_Policy'.  It
     also activates pragmas `Check', `Precondition', and
     `Postcondition'. Note that these pragmas can also be controlled
     using the configuration pragma `Check_Policy'. In Ada 2012, it
     also activates all assertions defined in the RM as aspects:
     preconditions, postconditions, type invariants and (sub)type
     predicates. In all Ada modes, corresponding pragmas for type
     invariants and (sub)type predicates are also activated. The
     default is that all these assertions are disabled, and have no
     effect, other than being checked for syntactic validity, and in
     the case of subtype predicates, constructions such as membership
     tests still test predicates even if assertions are turned off.

`-gnatA'
     Avoid processing `gnat.adc'. If a `gnat.adc' file is present, it
     will be ignored.

`-gnatb'
     Generate brief messages to `stderr' even if verbose mode set.

`-gnatB'
     Assume no invalid (bad) values except for 'Valid attribute use
     (*note Validity Checking: fe.).

`-gnatc'
     Check syntax and semantics only (no code generation attempted).
     When the compiler is invoked by `gnatmake', if the switch `-gnatc'
     is only given to the compiler (after `-cargs' or in package
     Compiler of the project file, `gnatmake' will fail because it will
     not find the object file after compilation. If `gnatmake' is
     called with `-gnatc' as a builder switch (before `-cargs' or in
     package Builder of the project file) then `gnatmake' will not fail
     because it will not look for the object files after compilation,
     and it will not try to build and link. This switch may not be
     given if a previous `-gnatR' switch has been given, since `-gnatR'
     requires that the code generator be called to complete
     determination of representation information.

`-gnatC'
     Generate CodePeer intermediate format (no code generation
     attempted).  This switch will generate an intermediate
     representation suitable for use by CodePeer (`.scil' files). This
     switch is not compatible with code generation (it will, among
     other things, disable some switches such as -gnatn, and enable
     others such as -gnata).

`-gnatd'
     Specify debug options for the compiler. The string of characters
     after the `-gnatd' specify the specific debug options. The possible
     characters are 0-9, a-z, A-Z, optionally preceded by a dot. See
     compiler source file `debug.adb' for details of the implemented
     debug options. Certain debug options are relevant to applications
     programmers, and these are documented at appropriate points in this
     users guide.

`-gnatD'
     Create expanded source files for source level debugging. This
     switch also suppress generation of cross-reference information
     (see `-gnatx'). Note that this switch is not allowed if a previous
     -gnatR switch has been given, since these two switches are not
     compatible.

`-gnateA'
     Check that the actual parameters of a subprogram call are not
     aliases of one another. To qualify as aliasing, the actuals must
     denote objects of a composite type, their memory locations must be
     identical or overlapping, and at least one of the corresponding
     formal parameters must be of mode OUT or IN OUT.

         type Rec_Typ is record
            Data : Integer := 0;
         end record;

         function Self (Val : Rec_Typ) return Rec_Typ is
         begin
            return Val;
         end Self;

         procedure Detect_Aliasing (Val_1 : in out Rec_Typ; Val_2 : Rec_Typ) is
         begin
            null;
         end Detect_Aliasing;

         Obj : Rec_Typ;

         Detect_Aliasing (Obj, Obj);
         Detect_Aliasing (Obj, Self (Obj));

     In the example above, the first call to `Detect_Aliasing' fails
     with a `Program_Error' at runtime because the actuals for `Val_1'
     and `Val_2' denote the same object. The second call executes
     without raising an exception because `Self(Obj)' produces an
     anonymous object which does not share the memory location of `Obj'.

`-gnatec=`path''
     Specify a configuration pragma file (the equal sign is optional)
     (*note The Configuration Pragmas Files: 7b.).

`-gnateC'
     Generate CodePeer messages in a compiler-like format. This switch
     is only effective if `-gnatcC' is also specified and requires an
     installation of CodePeer.

`-gnated'
     Disable atomic synchronization

`-gnateDsymbol[=`value']'
     Defines a symbol, associated with `value', for preprocessing.
     (*note Integrated Preprocessing: 1a.).

`-gnateE'
     Generate extra information in exception messages. In particular,
     display extra column information and the value and range
     associated with index and range check failures, and extra column
     information for access checks.  In cases where the compiler is
     able to determine at compile time that a check will fail, it gives
     a warning, and the extra information is not produced at run time.

`-gnatef'
     Display full source path name in brief error messages.

`-gnateF'
     Check for overflow on all floating-point operations, including
     those for unconstrained predefined types. See description of pragma
     `Check_Float_Overflow' in GNAT RM.

`-gnateg' `-gnatceg'

     The `-gnatc' switch must always be specified before this switch,
     e.g.  `-gnatceg'. Generate a C header from the Ada input file. See
     *note Generating C Headers for Ada Specifications: d0. for more
     information.

`-gnateG'
     Save result of preprocessing in a text file.

`-gnatei`nnn''
     Set maximum number of instantiations during compilation of a
     single unit to `nnn'. This may be useful in increasing the default
     maximum of 8000 for the rare case when a single unit legitimately
     exceeds this limit.

`-gnateI`nnn''
     Indicates that the source is a multi-unit source and that the
     index of the unit to compile is `nnn'. `nnn' needs to be a
     positive number and need to be a valid index in the multi-unit
     source.

`-gnatel'
     This switch can be used with the static elaboration model to issue
     info messages showing where implicit `pragma Elaborate' and
     `pragma Elaborate_All' are generated. This is useful in diagnosing
     elaboration circularities caused by these implicit pragmas when
     using the static elaboration model. See See the section in this
     guide on elaboration checking for further details. These messages
     are not generated by default, and are intended only for temporary
     use when debugging circularity problems.

`-gnateL'
     This switch turns off the info messages about implicit elaboration
     pragmas.

`-gnatem=`path''
     Specify a mapping file (the equal sign is optional) (*note Units
     to Sources Mapping Files: ff.).

`-gnatep=`file''
     Specify a preprocessing data file (the equal sign is optional)
     (*note Integrated Preprocessing: 1a.).

`-gnateP'
     Turn categorization dependency errors into warnings.  Ada requires
     that units that WITH one another have compatible categories, for
     example a Pure unit cannot WITH a Preelaborate unit. If this
     switch is used, these errors become warnings (which can be
     ignored, or suppressed in the usual manner). This can be useful in
     some specialized circumstances such as the temporary use of
     special test software.

`-gnateS'
     Synonym of `-fdump-scos', kept for backwards compatibility.

`-gnatet=`path''
     Generate target dependent information. The format of the output
     file is described in the section about switch `-gnateT'.

`-gnateT=`path''
     Read target dependent information, such as endianness or sizes and
     alignments of base type. If this switch is passed, the default
     target dependent information of the compiler is replaced by the
     one read from the input file.  This is used by tools other than
     the compiler, e.g. to do semantic analysis of programs that will
     run on some other target than the machine on which the tool is run.

     The following target dependent values should be defined, where
     `Nat' denotes a natural integer value, `Pos' denotes a positive
     integer value, and fields marked with a question mark are boolean
     fields, where a value of 0 is False, and a value of 1 is True:

         Bits_BE                    : Nat; -- Bits stored big-endian?
         Bits_Per_Unit              : Pos; -- Bits in a storage unit
         Bits_Per_Word              : Pos; -- Bits in a word
         Bytes_BE                   : Nat; -- Bytes stored big-endian?
         Char_Size                  : Pos; -- Standard.Character'Size
         Double_Float_Alignment     : Nat; -- Alignment of double float
         Double_Scalar_Alignment    : Nat; -- Alignment of double length scalar
         Double_Size                : Pos; -- Standard.Long_Float'Size
         Float_Size                 : Pos; -- Standard.Float'Size
         Float_Words_BE             : Nat; -- Float words stored big-endian?
         Int_Size                   : Pos; -- Standard.Integer'Size
         Long_Double_Size           : Pos; -- Standard.Long_Long_Float'Size
         Long_Long_Size             : Pos; -- Standard.Long_Long_Integer'Size
         Long_Size                  : Pos; -- Standard.Long_Integer'Size
         Maximum_Alignment          : Pos; -- Maximum permitted alignment
         Max_Unaligned_Field        : Pos; -- Maximum size for unaligned bit field
         Pointer_Size               : Pos; -- System.Address'Size
         Short_Enums                : Nat; -- Short foreign convention enums?
         Short_Size                 : Pos; -- Standard.Short_Integer'Size
         Strict_Alignment           : Nat; -- Strict alignment?
         System_Allocator_Alignment : Nat; -- Alignment for malloc calls
         Wchar_T_Size               : Pos; -- Interfaces.C.wchar_t'Size
         Words_BE                   : Nat; -- Words stored big-endian?

     The format of the input file is as follows. First come the values
     of the variables defined above, with one line per value:

         name  value

     where `name' is the name of the parameter, spelled out in full,
     and cased as in the above list, and `value' is an unsigned decimal
     integer. Two or more blanks separates the name from the value.

     All the variables must be present, in alphabetical order (i.e. the
     same order as the list above).

     Then there is a blank line to separate the two parts of the file.
     Then come the lines showing the floating-point types to be
     registered, with one line per registered mode:

         name  digs float_rep size alignment

     where `name' is the string name of the type (which can have single
     spaces embedded in the name (e.g. long double), `digs' is the
     number of digits for the floating-point type, `float_rep' is the
     float representation (I/V/A for IEEE-754-Binary, Vax_Native,
     AAMP), `size' is the size in bits, `alignment' is the alignment in
     bits. The name is followed by at least two blanks, fields are
     separated by at least one blank, and a LF character immediately
     follows the alignment field.

     Here is an example of a target parameterization file:

         Bits_BE                       0
         Bits_Per_Unit                 8
         Bits_Per_Word                64
         Bytes_BE                      0
         Char_Size                     8
         Double_Float_Alignment        0
         Double_Scalar_Alignment       0
         Double_Size                  64
         Float_Size                   32
         Float_Words_BE                0
         Int_Size                     64
         Long_Double_Size            128
         Long_Long_Size               64
         Long_Size                    64
         Maximum_Alignment            16
         Max_Unaligned_Field          64
         Pointer_Size                 64
         Short_Size                   16
         Strict_Alignment              0
         System_Allocator_Alignment   16
         Wchar_T_Size                 32
         Words_BE                      0

         float         15  I  64  64
         double        15  I  64  64
         long double   18  I  80 128
         TF            33  I 128 128

`-gnateu'
     Ignore unrecognized validity, warning, and style switches that
     appear after this switch is given. This may be useful when
     compiling sources developed on a later version of the compiler
     with an earlier version. Of course the earlier version must
     support this switch.

`-gnateV'
     Check that all actual parameters of a subprogram call are valid
     according to the rules of validity checking (*note Validity
     Checking: fe.).

`-gnateY'
     Ignore all STYLE_CHECKS pragmas. Full legality checks are still
     carried out, but the pragmas have no effect on what style checks
     are active. This allows all style checking options to be
     controlled from the command line.

`-gnatE'
     Full dynamic elaboration checks.

`-gnatf'
     Full errors. Multiple errors per line, all undefined references,
     do not attempt to suppress cascaded errors.

`-gnatF'
     Externals names are folded to all uppercase.

`-gnatg'
     Internal GNAT implementation mode. This should not be used for
     applications programs, it is intended only for use by the compiler
     and its run-time library. For documentation, see the GNAT sources.
     Note that `-gnatg' implies `-gnatw.ge' and `-gnatyg' so that all
     standard warnings and all standard style options are turned on.
     All warnings and style messages are treated as errors.

`-gnatG=nn'
     List generated expanded code in source form.

`-gnath'
     Output usage information. The output is written to `stdout'.

`-gnati`c''
     Identifier character set (`c' = 1/2/3/4/8/9/p/f/n/w).  For details
     of the possible selections for `c', see *note Character Set
     Control: 4a.

`-gnatI'
     Ignore representation clauses. When this switch is used,
     representation clauses are treated as comments. This is useful
     when initially porting code where you want to ignore rep clause
     problems, and also for compiling foreign code (particularly for
     use with ASIS). The representation clauses that are ignored are:
     enumeration_representation_clause, record_representation_clause,
     and attribute_definition_clause for the following attributes:
     Address, Alignment, Bit_Order, Component_Size, Machine_Radix,
     Object_Size, Size, Small, Stream_Size, and Value_Size.  Note that
     this option should be used only for compiling - the code is likely
     to malfunction at run time.

     Note that when `-gnatct' is used to generate trees for input into
     `ASIS' tools, these representation clauses are removed from the
     tree and ignored. This means that the tool will not see them.

`-gnatj`nn''
     Reformat error messages to fit on `nn' character lines

`-gnatk=`n''
     Limit file names to `n' (1-999) characters (`k' = krunch).

`-gnatl'
     Output full source listing with embedded error messages.

`-gnatL'
     Used in conjunction with -gnatG or -gnatD to intersperse original
     source lines (as comment lines with line numbers) in the expanded
     source output.

`-gnatm=`n''
     Limit number of detected error or warning messages to `n' where
     `n' is in the range 1..999999. The default setting if no switch is
     given is 9999. If the number of warnings reaches this limit, then
     a message is output and further warnings are suppressed, but the
     compilation is continued. If the number of error messages reaches
     this limit, then a message is output and the compilation is
     abandoned. The equal sign here is optional. A value of zero means
     that no limit applies.

`-gnatn[12]'
     Activate inlining for subprograms for which pragma `Inline' is
     specified. This inlining is performed by the GCC back-end. An
     optional digit sets the inlining level: 1 for moderate inlining
     across modules or 2 for full inlining across modules. If no
     inlining level is specified, the compiler will pick it based on
     the optimization level.

`-gnatN'
     Activate front end inlining for subprograms for which pragma
     `Inline' is specified. This inlining is performed by the front end
     and will be visible in the `-gnatG' output.

     When using a gcc-based back end (in practice this means using any
     version of GNAT other than the JGNAT, .NET or GNAAMP versions),
     then the use of `-gnatN' is deprecated, and the use of `-gnatn' is
     preferred.  Historically front end inlining was more extensive
     than the gcc back end inlining, but that is no longer the case.

`-gnato0'
     Suppresses overflow checking. This causes the behavior of the
     compiler to match the default for older versions where overflow
     checking was suppressed by default. This is equivalent to having
     `pragma Suppress (Overflow_Mode)' in a configuration pragma file.

`-gnato??'
     Set default mode for handling generation of code to avoid
     intermediate arithmetic overflow. Here `??' is two digits, a
     single digit, or nothing. Each digit is one of the digits `1'
     through `3':

     Digit     Interpretation
     `1'       All intermediate overflows checked against base type (`STRICT')
     `2'       Minimize intermediate overflows (`MINIMIZED')
     `3'       Eliminate intermediate overflows (`ELIMINATED')

     If only one digit appears, then it applies to all cases; if two
     digits are given, then the first applies outside assertions,
     pre/postconditions, and type invariants, and the second applies
     within assertions, pre/postconditions, and type invariants.

     If no digits follow the `-gnato', then it is equivalent to
     `-gnato11', causing all intermediate overflows to be handled in
     strict mode.

     This switch also causes arithmetic overflow checking to be
     performed (as though `pragma Unsuppress (Overflow_Mode)' had been
     specified).

     The default if no option `-gnato' is given is that overflow
     handling is in `STRICT' mode (computations done using the base
     type), and that overflow checking is enabled.

     Note that division by zero is a separate check that is not
     controlled by this switch (divide-by-zero checking is on by
     default).

     See also *note Specifying the Desired Mode: 100.

`-gnatp'
     Suppress all checks. See *note Run-Time Checks: 101. for details.
     This switch has no effect if cancelled by a subsequent `-gnat-p'
     switch.

`-gnat-p'
     Cancel effect of previous `-gnatp' switch.

`-gnatP'
     Enable polling. This is required on some systems (notably Windows
     NT) to obtain asynchronous abort and asynchronous transfer of
     control capability.  See `Pragma_Polling' in the
     `GNAT_Reference_Manual' for full details.

`-gnatq'
     Don't quit. Try semantics, even if parse errors.

`-gnatQ'
     Don't quit. Generate `ALI' and tree files even if illegalities.
     Note that code generation is still suppressed in the presence of
     any errors, so even with `-gnatQ' no object file is generated.

`-gnatr'
     Treat pragma Restrictions as Restriction_Warnings.

`-gnatR[0/1/2/3[s]]'
     Output representation information for declared types and objects.
     Note that this switch is not allowed if a previous `-gnatD' switch
     has been given, since these two switches are not compatible.

`-gnatRm[s]'
     Output convention and parameter passing mechanisms for all
     subprograms.

`-gnats'
     Syntax check only.

`-gnatS'
     Print package Standard.

`-gnatt'
     Generate tree output file.

`-gnatT`nnn''
     All compiler tables start at `nnn' times usual starting size.

`-gnatu'
     List units for this compilation.

`-gnatU'
     Tag all error messages with the unique string 'error:'

`-gnatv'
     Verbose mode. Full error output with source lines to `stdout'.

`-gnatV'
     Control level of validity checking (*note Validity Checking: fe.).

`-gnatw`xxx''
     Warning mode where `xxx' is a string of option letters that denotes
     the exact warnings that are enabled or disabled (*note Warning
     Message Control: 102.).

`-gnatW`e''
     Wide character encoding method (`e'=n/h/u/s/e/8).

`-gnatx'
     Suppress generation of cross-reference information.

`-gnatX'
     Enable GNAT implementation extensions and latest Ada version.

`-gnaty'
     Enable built-in style checks (*note Style Checking: 103.).

`-gnatz`m''
     Distribution stub generation and compilation (`m'=r/c for
     receiver/caller stubs).

`-I`dir''
     Direct GNAT to search the `dir' directory for source files needed
     by the current compilation (see *note Search Paths and the
     Run-Time Library (RTL): 8e.).

`-I-'
     Except for the source file named in the command line, do not look
     for source files in the directory containing the source file named
     in the command line (see *note Search Paths and the Run-Time
     Library (RTL): 8e.).

`-o `file''
     This switch is used in `gcc' to redirect the generated object file
     and its associated ALI file. Beware of this switch with GNAT,
     because it may cause the object file and ALI file to have
     different names which in turn may confuse the binder and the
     linker.

`-nostdinc'
     Inhibit the search of the default location for the GNAT Run Time
     Library (RTL) source files.

`-nostdlib'
     Inhibit the search of the default location for the GNAT Run Time
     Library (RTL) ALI files.

`-O[`n']'
     `n' controls the optimization level:

     `n'         Effect
     `0'         No optimization, the default setting if no `-O' appears
     `1'         Normal optimization, the default if you specify `-O' without an
                 operand. A good compromise between code quality and compilation time.
     `2'         Extensive optimization, may improve execution time, possibly at the
                 cost of substantially increased compilation time.
     `3'         Same as `-O2', and also includes inline expansion for small
                 subprograms in the same unit.
     `s'         Optimize space usage

     See also *note Optimization Levels: 104.

`-pass-exit-codes'
     Catch exit codes from the compiler and use the most meaningful as
     exit status.

`--RTS=`rts-path''
     Specifies the default location of the runtime library. Same
     meaning as the equivalent `gnatmake' flag (*note Switches for
     gnatmake: e2.).

`-S'
     Used in place of `-c' to cause the assembler source file to be
     generated, using `.s' as the extension, instead of the object file.
     This may be useful if you need to examine the generated assembly
     code.

`-fverbose-asm'
     Used in conjunction with `-S' to cause the generated assembly code
     file to be annotated with variable names, making it significantly
     easier to follow.

`-v'
     Show commands generated by the `gcc' driver. Normally used only for
     debugging purposes or if you need to be sure what version of the
     compiler you are executing.

`-V `ver''
     Execute `ver' version of the compiler. This is the `gcc' version,
     not the GNAT version.

`-w'
     Turn off warnings generated by the back end of the compiler. Use of
     this switch also causes the default for front end warnings to be
     set to suppress (as though `-gnatws' had appeared at the start of
     the options).

You may combine a sequence of GNAT switches into a single switch. For
example, the combined switch

         -gnatofi3

is equivalent to specifying the following sequence of switches:

         -gnato -gnatf -gnati3

The following restrictions apply to the combination of switches in this
manner:

   * The switch `-gnatc' if combined with other switches must come
     first in the string.

   * The switch `-gnats' if combined with other switches must come
     first in the string.

   * The switches `-gnatzc' and `-gnatzr' may not be combined with any
     other switches, and only one of them may appear in the command
     line.

   * The switch `-gnat-p' may not be combined with any other switch.

   * Once a 'y' appears in the string (that is a use of the `-gnaty'
     switch), then all further characters in the switch are interpreted
     as style modifiers (see description of `-gnaty').

   * Once a 'd' appears in the string (that is a use of the `-gnatd'
     switch), then all further characters in the switch are interpreted
     as debug flags (see description of `-gnatd').

   * Once a 'w' appears in the string (that is a use of the `-gnatw'
     switch), then all further characters in the switch are interpreted
     as warning mode modifiers (see description of `-gnatw').

   * Once a 'V' appears in the string (that is a use of the `-gnatV'
     switch), then all further characters in the switch are interpreted
     as validity checking options (*note Validity Checking: fe.).

   * Option 'em', 'ec', 'ep', 'l=' and 'R' must be the last options in
     a combined list of options.


File: gnat_ugn.info,  Node: Output and Error Message Control,  Next: Warning Message Control,  Prev: Alphabetical List of All Switches,  Up: Compiler Switches

4.3.2 Output and Error Message Control
--------------------------------------

The standard default format for error messages is called 'brief format'.
Brief format messages are written to `stderr' (the standard error file)
and have the following form:

    e.adb:3:04: Incorrect spelling of keyword "function"
    e.adb:4:20: ";" should be "is"

The first integer after the file name is the line number in the file,
and the second integer is the column number within the line.  `GPS' can
parse the error messages and point to the referenced character.  The
following switches provide control over the error message format:

`-gnatv'
     The `v' stands for verbose.  The effect of this setting is to
     write long-format error messages to `stdout' (the standard output
     file.  The same program compiled with the `-gnatv' switch would
     generate:

         3. funcion X (Q : Integer)
            |
         >>> Incorrect spelling of keyword "function"
         4. return Integer;
                          |
         >>> ";" should be "is"

     The vertical bar indicates the location of the error, and the `>>>'
     prefix can be used to search for error messages. When this switch
     is used the only source lines output are those with errors.

`-gnatl'
     The `l' stands for list.  This switch causes a full listing of the
     file to be generated. In the case where a body is compiled, the
     corresponding spec is also listed, along with any subunits.
     Typical output from compiling a package body `p.adb' might look
     like:

         Compiling: p.adb

              1. package body p is
              2.    procedure a;
              3.    procedure a is separate;
              4. begin
              5.    null
                        |
                 >>> missing ";"

              6. end;

         Compiling: p.ads

              1. package p is
              2.    pragma Elaborate_Body
                                         |
                 >>> missing ";"

              3. end p;

         Compiling: p-a.adb

              1. separate p
                         |
                 >>> missing "("

              2. procedure a is
              3. begin
              4.    null
                        |
                 >>> missing ";"

              5. end;

     When you specify the `-gnatv' or `-gnatl' switches and standard
     output is redirected, a brief summary is written to `stderr'
     (standard error) giving the number of error messages and warning
     messages generated.

`-gnatl=`fname''
     This has the same effect as `-gnatl' except that the output is
     written to a file instead of to standard output. If the given name
     `fname' does not start with a period, then it is the full name of
     the file to be written. If `fname' is an extension, it is appended
     to the name of the file being compiled. For example, if file
     `xyz.adb' is compiled with `-gnatl=.lst', then the output is
     written to file xyz.adb.lst.

`-gnatU'
     This switch forces all error messages to be preceded by the unique
     string 'error:'. This means that error messages take a few more
     characters in space, but allows easy searching for and
     identification of error messages.

`-gnatb'
     The `b' stands for brief.  This switch causes GNAT to generate the
     brief format error messages to `stderr' (the standard error file)
     as well as the verbose format message or full listing (which as
     usual is written to `stdout' (the standard output file).

`-gnatm=`n''
     The `m' stands for maximum.  `n' is a decimal integer in the range
     of 1 to 999999 and limits the number of error or warning messages
     to be generated. For example, using `-gnatm2' might yield

         e.adb:3:04: Incorrect spelling of keyword "function"
         e.adb:5:35: missing ".."
         fatal error: maximum number of errors detected
         compilation abandoned

     The default setting if no switch is given is 9999. If the number
     of warnings reaches this limit, then a message is output and
     further warnings are suppressed, but the compilation is continued.
     If the number of error messages reaches this limit, then a message
     is output and the compilation is abandoned. A value of zero means
     that no limit applies.

     Note that the equal sign is optional, so the switches `-gnatm2'
     and `-gnatm=2' are equivalent.

`-gnatf'
     The `f' stands for full.  Normally, the compiler suppresses error
     messages that are likely to be redundant. This switch causes all
     error messages to be generated. In particular, in the case of
     references to undefined variables. If a given variable is
     referenced several times, the normal format of messages is

         e.adb:7:07: "V" is undefined (more references follow)

     where the parenthetical comment warns that there are additional
     references to the variable `V'. Compiling the same program with the
     `-gnatf' switch yields

         e.adb:7:07: "V" is undefined
         e.adb:8:07: "V" is undefined
         e.adb:8:12: "V" is undefined
         e.adb:8:16: "V" is undefined
         e.adb:9:07: "V" is undefined
         e.adb:9:12: "V" is undefined

     The `-gnatf' switch also generates additional information for some
     error messages.  Some examples are:

        * Details on possibly non-portable unchecked conversion

        * List possible interpretations for ambiguous calls

        * Additional details on incorrect parameters

`-gnatjnn'
     In normal operation mode (or if `-gnatj0' is used), then error
     messages with continuation lines are treated as though the
     continuation lines were separate messages (and so a warning with
     two continuation lines counts as three warnings, and is listed as
     three separate messages).

     If the `-gnatjnn' switch is used with a positive value for nn, then
     messages are output in a different manner. A message and all its
     continuation lines are treated as a unit, and count as only one
     warning or message in the statistics totals. Furthermore, the
     message is reformatted so that no line is longer than nn
     characters.

`-gnatq'
     The `q' stands for quit (really 'don't quit').  In normal
     operation mode, the compiler first parses the program and
     determines if there are any syntax errors. If there are,
     appropriate error messages are generated and compilation is
     immediately terminated.  This switch tells GNAT to continue with
     semantic analysis even if syntax errors have been found. This may
     enable the detection of more errors in a single run. On the other
     hand, the semantic analyzer is more likely to encounter some
     internal fatal error when given a syntactically invalid tree.

`-gnatQ'
     In normal operation mode, the `ALI' file is not generated if any
     illegalities are detected in the program. The use of `-gnatQ'
     forces generation of the `ALI' file. This file is marked as being
     in error, so it cannot be used for binding purposes, but it does
     contain reasonably complete cross-reference information, and thus
     may be useful for use by tools (e.g., semantic browsing tools or
     integrated development environments) that are driven from the
     `ALI' file. This switch implies `-gnatq', since the semantic phase
     must be run to get a meaningful ALI file.

     In addition, if `-gnatt' is also specified, then the tree file is
     generated even if there are illegalities. It may be useful in this
     case to also specify `-gnatq' to ensure that full semantic
     processing occurs. The resulting tree file can be processed by
     ASIS, for the purpose of providing partial information about
     illegal units, but if the error causes the tree to be badly
     malformed, then ASIS may crash during the analysis.

     When `-gnatQ' is used and the generated `ALI' file is marked as
     being in error, `gnatmake' will attempt to recompile the source
     when it finds such an `ALI' file, including with switch `-gnatc'.

     Note that `-gnatQ' has no effect if `-gnats' is specified, since
     ALI files are never generated if `-gnats' is set.


File: gnat_ugn.info,  Node: Warning Message Control,  Next: Debugging and Assertion Control,  Prev: Output and Error Message Control,  Up: Compiler Switches

4.3.3 Warning Message Control
-----------------------------

In addition to error messages, which correspond to illegalities as
defined in the Ada Reference Manual, the compiler detects two kinds of
warning situations.

First, the compiler considers some constructs suspicious and generates a
warning message to alert you to a possible error. Second, if the
compiler detects a situation that is sure to raise an exception at run
time, it generates a warning message. The following shows an example of
warning messages:

    e.adb:4:24: warning: creation of object may raise Storage_Error
    e.adb:10:17: warning: static value out of range
    e.adb:10:17: warning: "Constraint_Error" will be raised at run time

GNAT considers a large number of situations as appropriate for the
generation of warning messages. As always, warnings are not definite
indications of errors. For example, if you do an out-of-range
assignment with the deliberate intention of raising a
`Constraint_Error' exception, then the warning that may be issued does
not indicate an error. Some of the situations for which GNAT issues
warnings (at least some of the time) are given in the following list.
This list is not complete, and new warnings are often added to
subsequent versions of GNAT. The list is intended to give a general idea
of the kinds of warnings that are generated.

   * Possible infinitely recursive calls

   * Out-of-range values being assigned

   * Possible order of elaboration problems

   * Size not a multiple of alignment for a record type

   * Assertions (pragma Assert) that are sure to fail

   * Unreachable code

   * Address clauses with possibly unaligned values, or where an
     attempt is made to overlay a smaller variable with a larger one.

   * Fixed-point type declarations with a null range

   * Direct_IO or Sequential_IO instantiated with a type that has
     access values

   * Variables that are never assigned a value

   * Variables that are referenced before being initialized

   * Task entries with no corresponding `accept' statement

   * Duplicate accepts for the same task entry in a `select'

   * Objects that take too much storage

   * Unchecked conversion between types of differing sizes

   * Missing `return' statement along some execution path in a function

   * Incorrect (unrecognized) pragmas

   * Incorrect external names

   * Allocation from empty storage pool

   * Potentially blocking operation in protected type

   * Suspicious parenthesization of expressions

   * Mismatching bounds in an aggregate

   * Attempt to return local value by reference

   * Premature instantiation of a generic body

   * Attempt to pack aliased components

   * Out of bounds array subscripts

   * Wrong length on string assignment

   * Violations of style rules if style checking is enabled

   * Unused `with' clauses

   * `Bit_Order' usage that does not have any effect

   * `Standard.Duration' used to resolve universal fixed expression

   * Dereference of possibly null value

   * Declaration that is likely to cause storage error

   * Internal GNAT unit `with'ed by application unit

   * Values known to be out of range at compile time

   * Unreferenced or unmodified variables. Note that a special
     exemption applies to variables which contain any of the substrings
     `DISCARD, DUMMY, IGNORE, JUNK, UNUSED', in any casing. Such
     variables are considered likely to be intentionally used in a
     situation where otherwise a warning would be given, so warnings of
     this kind are always suppressed for such variables.

   * Address overlays that could clobber memory

   * Unexpected initialization when address clause present

   * Bad alignment for address clause

   * Useless type conversions

   * Redundant assignment statements and other redundant constructs

   * Useless exception handlers

   * Accidental hiding of name by child unit

   * Access before elaboration detected at compile time

   * A range in a `for' loop that is known to be null or might be null

The following section lists compiler switches that are available to
control the handling of warning messages. It is also possible to
exercise much finer control over what warnings are issued and
suppressed using the GNAT pragma Warnings (see the description of the
pragma in the `GNAT_Reference_manual').

`-gnatwa'
     `Activate most optional warnings.'

     This switch activates most optional warning messages.  See the
     remaining list in this section for details on optional warning
     messages that can be individually controlled.  The warnings that
     are not turned on by this switch are:

        * `-gnatwd' (implicit dereferencing)

        * `-gnatw.d' (tag warnings with -gnatw switch)

        * `-gnatwh' (hiding)

        * `-gnatw.h' (holes in record layouts)

        * `-gnatw.k' (redefinition of names in standard)

        * `-gnatwl' (elaboration warnings)

        * `-gnatw.l' (inherited aspects)

        * `-gnatw.n' (atomic synchronization)

        * `-gnatwo' (address clause overlay)

        * `-gnatw.o' (values set by out parameters ignored)

        * `-gnatw.s' (overridden size clause)

        * `-gnatwt' (tracking of deleted conditional code)

        * `-gnatw.u' (unordered enumeration)

        * `-gnatw.w' (use of Warnings Off)

        * `-gnatw.y' (reasons for package needing body)

     All other optional warnings are turned on.

`-gnatwA'
     `Suppress all optional errors.'

     This switch suppresses all optional warning messages, see
     remaining list in this section for details on optional warning
     messages that can be individually controlled. Note that unlike
     switch `-gnatws', the use of switch `-gnatwA' does not suppress
     warnings that are normally given unconditionally and cannot be
     individually controlled (for example, the warning about a missing
     exit path in a function).  Also, again unlike switch `-gnatws',
     warnings suppressed by the use of switch `-gnatwA' can be
     individually turned back on. For example the use of switch
     `-gnatwA' followed by switch `-gnatwd' will suppress all optional
     warnings except the warnings for implicit dereferencing.

`-gnatw.a'
     `Activate warnings on failing assertions.'

     This switch activates warnings for assertions where the compiler
     can tell at compile time that the assertion will fail. Note that
     this warning is given even if assertions are disabled. The default
     is that such warnings are generated.

`-gnatw.A'
     `Suppress warnings on failing assertions.'

     This switch suppresses warnings for assertions where the compiler
     can tell at compile time that the assertion will fail.

`-gnatwb'
     `Activate warnings on bad fixed values.'

     This switch activates warnings for static fixed-point expressions
     whose value is not an exact multiple of Small. Such values are
     implementation dependent, since an implementation is free to
     choose either of the multiples that surround the value. GNAT
     always chooses the closer one, but this is not required behavior,
     and it is better to specify a value that is an exact multiple,
     ensuring predictable execution. The default is that such warnings
     are not generated.

`-gnatwB'
     `Suppress warnings on bad fixed values.'

     This switch suppresses warnings for static fixed-point expressions
     whose value is not an exact multiple of Small.

`-gnatw.b'
     `Activate warnings on biased representation.'

     This switch activates warnings when a size clause, value size
     clause, component clause, or component size clause forces the use
     of biased representation for an integer type (e.g. representing a
     range of 10..11 in a single bit by using 0/1 to represent 10/11).
     The default is that such warnings are generated.

`-gnatw.B'
     `Suppress warnings on biased representation.'

     This switch suppresses warnings for representation clauses that
     force the use of biased representation.

`-gnatwc'
     `Activate warnings on conditionals.'

     This switch activates warnings for conditional expressions used in
     tests that are known to be True or False at compile time. The
     default is that such warnings are not generated.  Note that this
     warning does not get issued for the use of boolean variables or
     constants whose values are known at compile time, since this is a
     standard technique for conditional compilation in Ada, and this
     would generate too many false positive warnings.

     This warning option also activates a special test for comparisons
     using the operators '>=' and' <='.  If the compiler can tell that
     only the equality condition is possible, then it will warn that
     the '>' or '<' part of the test is useless and that the operator
     could be replaced by '='.  An example would be comparing a
     `Natural' variable <= 0.

     This warning option also generates warnings if one or both tests
     is optimized away in a membership test for integer values if the
     result can be determined at compile time. Range tests on
     enumeration types are not included, since it is common for such
     tests to include an end point.

     This warning can also be turned on using `-gnatwa'.

`-gnatwC'
     `Suppress warnings on conditionals.'

     This switch suppresses warnings for conditional expressions used in
     tests that are known to be True or False at compile time.

`-gnatw.c'
     `Activate warnings on missing component clauses.'

     This switch activates warnings for record components where a record
     representation clause is present and has component clauses for the
     majority, but not all, of the components. A warning is given for
     each component for which no component clause is present.

`-gnatw.C'
     `Suppress warnings on missing component clauses.'

     This switch suppresses warnings for record components that are
     missing a component clause in the situation described above.

`-gnatwd'
     `Activate warnings on implicit dereferencing.'

     If this switch is set, then the use of a prefix of an access type
     in an indexed component, slice, or selected component without an
     explicit `.all' will generate a warning. With this warning
     enabled, access checks occur only at points where an explicit
     `.all' appears in the source code (assuming no warnings are
     generated as a result of this switch). The default is that such
     warnings are not generated.

`-gnatwD'
     `Suppress warnings on implicit dereferencing.'

     This switch suppresses warnings for implicit dereferences in
     indexed components, slices, and selected components.

`-gnatw.d'
     `Activate tagging of warning and info messages.'

     If this switch is set, then warning messages are tagged, with one
     of the following strings:

             - `[-gnatw?]'  Used to tag warnings controlled by the
               switch `-gnatwx' where x is a letter a-z.

             - `[-gnatw.?]'  Used to tag warnings controlled by the
               switch `-gnatw.x' where x is a letter a-z.

             - `[-gnatel]' Used to tag elaboration information (info)
               messages generated when the static model of elaboration
               is used and the `-gnatel' switch is set.

             - `[restriction warning]' Used to tag warning messages for
               restriction violations, activated by use of the pragma
               `Restriction_Warnings'.

             - `[warning-as-error]' Used to tag warning messages that
               have been converted to error messages by use of the
               pragma Warning_As_Error. Note that such warnings are
               prefixed by the string "error: " rather than "warning: ".

             - `[enabled by default]' Used to tag all other warnings
               that are always given by default, unless warnings are
               completely suppressed using pragma `Warnings(Off)' or
               the switch `-gnatws'.

`-gnatw.D'
     `Deactivate tagging of warning and info messages messages.'

     If this switch is set, then warning messages return to the default
     mode in which warnings and info messages are not tagged as
     described above for `-gnatw.d'.

`-gnatwe'
     `Treat warnings and style checks as errors.'

     This switch causes warning messages and style check messages to be
     treated as errors.  The warning string still appears, but the
     warning messages are counted as errors, and prevent the generation
     of an object file. Note that this is the only -gnatw switch that
     affects the handling of style check messages.  Note also that this
     switch has no effect on info (information) messages, which are not
     treated as errors if this switch is present.

`-gnatw.e'
     `Activate every optional warning.'

     This switch activates all optional warnings, including those which
     are not activated by `-gnatwa'. The use of this switch is not
     recommended for normal use. If you turn this switch on, it is
     almost certain that you will get large numbers of useless
     warnings. The warnings that are excluded from `-gnatwa' are
     typically highly specialized warnings that are suitable for use
     only in code that has been specifically designed according to
     specialized coding rules.

`-gnatwf'
     `Activate warnings on unreferenced formals.'

     This switch causes a warning to be generated if a formal parameter
     is not referenced in the body of the subprogram. This warning can
     also be turned on using `-gnatwu'. The default is that these
     warnings are not generated.

`-gnatwF'
     `Suppress warnings on unreferenced formals.'

     This switch suppresses warnings for unreferenced formal
     parameters. Note that the combination `-gnatwu' followed by
     `-gnatwF' has the effect of warning on unreferenced entities other
     than subprogram formals.

`-gnatwg'
     `Activate warnings on unrecognized pragmas.'

     This switch causes a warning to be generated if an unrecognized
     pragma is encountered. Apart from issuing this warning, the pragma
     is ignored and has no effect. The default is that such warnings
     are issued (satisfying the Ada Reference Manual requirement that
     such warnings appear).

`-gnatwG'
     `Suppress warnings on unrecognized pragmas.'

     This switch suppresses warnings for unrecognized pragmas.

`-gnatw.g'
     `Warnings used for GNAT sources.'

     This switch sets the warning categories that are used by the
     standard GNAT style. Currently this is equivalent to
     `-gnatwAao.sI.C.V.X' but more warnings may be added in the future
     without advanced notice.

`-gnatwh'
     `Activate warnings on hiding.'

     This switch activates warnings on hiding declarations.  A
     declaration is considered hiding if it is for a non-overloadable
     entity, and it declares an entity with the same name as some other
     entity that is directly or use-visible. The default is that such
     warnings are not generated.

`-gnatwH'
     `Suppress warnings on hiding.'

     This switch suppresses warnings on hiding declarations.

`-gnatw.h'
     `Activate warnings on holes/gaps in records.'

     This switch activates warnings on component clauses in record
     representation clauses that leave holes (gaps) in the record
     layout.  If this warning option is active, then record
     representation clauses should specify a contiguous layout, adding
     unused fill fields if needed.

`-gnatw.H'
     `Suppress warnings on holes/gaps in records.'

     This switch suppresses warnings on component clauses in record
     representation clauses that leave holes (haps) in the record
     layout.

`-gnatwi'
     `Activate warnings on implementation units.'

     This switch activates warnings for a `with' of an internal GNAT
     implementation unit, defined as any unit from the `Ada',
     `Interfaces', `GNAT', or `System' hierarchies that is not
     documented in either the Ada Reference Manual or the GNAT
     Programmer's Reference Manual. Such units are intended only for
     internal implementation purposes and should not be `with'ed by
     user programs. The default is that such warnings are generated

`-gnatwI'
     `Disable warnings on implementation units.'

     This switch disables warnings for a `with' of an internal GNAT
     implementation unit.

`-gnatw.i'
     `Activate warnings on overlapping actuals.'

     This switch enables a warning on statically detectable overlapping
     actuals in a subprogram call, when one of the actuals is an in-out
     parameter, and the types of the actuals are not by-copy types.
     This warning is off by default.

`-gnatw.I'
     `Disable warnings on overlapping actuals.'

     This switch disables warnings on overlapping actuals in a call..

`-gnatwj'
     `Activate warnings on obsolescent features (Annex J).'

     If this warning option is activated, then warnings are generated
     for calls to subprograms marked with `pragma Obsolescent' and for
     use of features in Annex J of the Ada Reference Manual. In the
     case of Annex J, not all features are flagged. In particular use
     of the renamed packages (like `Text_IO') and use of package
     `ASCII' are not flagged, since these are very common and would
     generate many annoying positive warnings. The default is that such
     warnings are not generated.

     In addition to the above cases, warnings are also generated for
     GNAT features that have been provided in past versions but which
     have been superseded (typically by features in the new Ada
     standard).  For example, `pragma Ravenscar' will be flagged since
     its function is replaced by `pragma Profile(Ravenscar)', and
     `pragma Interface_Name' will be flagged since its function is
     replaced by `pragma Import'.

     Note that this warning option functions differently from the
     restriction `No_Obsolescent_Features' in two respects.  First, the
     restriction applies only to annex J features.  Second, the
     restriction does flag uses of package `ASCII'.

`-gnatwJ'
     `Suppress warnings on obsolescent features (Annex J).'

     This switch disables warnings on use of obsolescent features.

`-gnatwk'
     `Activate warnings on variables that could be constants.'

     This switch activates warnings for variables that are initialized
     but never modified, and then could be declared constants. The
     default is that such warnings are not given.

`-gnatwK'
     `Suppress warnings on variables that could be constants.'

     This switch disables warnings on variables that could be declared
     constants.

`-gnatw.k'
     `Activate warnings on redefinition of names in standard.'

     This switch activates warnings for declarations that declare a
     name that is defined in package Standard. Such declarations can be
     confusing, especially since the names in package Standard continue
     to be directly visible, meaning that use visibiliy on such
     redeclared names does not work as expected. Names of discriminants
     and components in records are not included in this check.

`-gnatw.K'
     `Suppress warnings on redefinition of names in standard.'

     This switch activates warnings for declarations that declare a
     name that is defined in package Standard.

`-gnatwl'
     `Activate warnings for elaboration pragmas.'

     This switch activates warnings for possible elaboration problems,
     including suspicious use of `Elaborate' pragmas, when using the
     static elaboration model, and possible situations that may raise
     `Program_Error' when using the dynamic elaboration model.  See the
     section in this guide on elaboration checking for further details.
     The default is that such warnings are not generated.

`-gnatwL'
     `Suppress warnings for elaboration pragmas.'

     This switch suppresses warnings for possible elaboration problems.

`-gnatw.l'
     `List inherited aspects.'

     This switch causes the compiler to list inherited invariants,
     preconditions, and postconditions from Type_Invariant'Class,
     Invariant'Class, Pre'Class, and Post'Class aspects. Also list
     inherited subtype predicates.

`-gnatw.L'
     `Suppress listing of inherited aspects.'

     This switch suppresses listing of inherited aspects.

`-gnatwm'
     `Activate warnings on modified but unreferenced variables.'

     This switch activates warnings for variables that are assigned
     (using an initialization value or with one or more assignment
     statements) but whose value is never read. The warning is
     suppressed for volatile variables and also for variables that are
     renamings of other variables or for which an address clause is
     given.  The default is that these warnings are not given.

`-gnatwM'
     `Disable warnings on modified but unreferenced variables.'

     This switch disables warnings for variables that are assigned or
     initialized, but never read.

`-gnatw.m'
     `Activate warnings on suspicious modulus values.'

     This switch activates warnings for modulus values that seem
     suspicious.  The cases caught are where the size is the same as
     the modulus (e.g.  a modulus of 7 with a size of 7 bits), and
     modulus values of 32 or 64 with no size clause. The guess in both
     cases is that 2**x was intended rather than x. In addition
     expressions of the form 2*x for small x generate a warning (the
     almost certainly accurate guess being that 2**x was intended). The
     default is that these warnings are given.

`-gnatw.M'
     `Disable warnings on suspicious modulus values.'

     This switch disables warnings for suspicious modulus values.

`-gnatwn'
     `Set normal warnings mode.'

     This switch sets normal warning mode, in which enabled warnings are
     issued and treated as warnings rather than errors. This is the
     default mode. the switch `-gnatwn' can be used to cancel the
     effect of an explicit `-gnatws' or `-gnatwe'. It also cancels the
     effect of the implicit `-gnatwe' that is activated by the use of
     `-gnatg'.

`-gnatw.n'
     `Activate warnings on atomic synchronization.'

     This switch actives warnings when an access to an atomic variable
     requires the generation of atomic synchronization code. These
     warnings are off by default.

`-gnatw.N'
     `Suppress warnings on atomic synchronization.'

     This switch suppresses warnings when an access to an atomic
     variable requires the generation of atomic synchronization code.

`-gnatwo'
     `Activate warnings on address clause overlays.'

     This switch activates warnings for possibly unintended
     initialization effects of defining address clauses that cause one
     variable to overlap another. The default is that such warnings are
     generated.

`-gnatwO'
     `Suppress warnings on address clause overlays.'

     This switch suppresses warnings on possibly unintended
     initialization effects of defining address clauses that cause one
     variable to overlap another.

`-gnatw.o'
     `Activate warnings on modified but unreferenced out parameters.'

     This switch activates warnings for variables that are modified by
     using them as actuals for a call to a procedure with an out mode
     formal, where the resulting assigned value is never read. It is
     applicable in the case where there is more than one out mode
     formal. If there is only one out mode formal, the warning is
     issued by default (controlled by -gnatwu).  The warning is
     suppressed for volatile variables and also for variables that are
     renamings of other variables or for which an address clause is
     given.  The default is that these warnings are not given.

`-gnatw.O'
     `Disable warnings on modified but unreferenced out parameters.'

     This switch suppresses warnings for variables that are modified by
     using them as actuals for a call to a procedure with an out mode
     formal, where the resulting assigned value is never read.

`-gnatwp'
     `Activate warnings on ineffective pragma Inlines.'

     This switch activates warnings for failure of front end inlining
     (activated by `-gnatN') to inline a particular call. There are
     many reasons for not being able to inline a call, including most
     commonly that the call is too complex to inline. The default is
     that such warnings are not given.  Warnings on ineffective
     inlining by the gcc back-end can be activated separately, using
     the gcc switch -Winline.

`-gnatwP'
     `Suppress warnings on ineffective pragma Inlines.'

     This switch suppresses warnings on ineffective pragma Inlines. If
     the inlining mechanism cannot inline a call, it will simply ignore
     the request silently.

`-gnatw.p'
     `Activate warnings on parameter ordering.'

     This switch activates warnings for cases of suspicious parameter
     ordering when the list of arguments are all simple identifiers that
     match the names of the formals, but are in a different order. The
     warning is suppressed if any use of named parameter notation is
     used, so this is the appropriate way to suppress a false positive
     (and serves to emphasize that the "misordering" is deliberate). The
     default is that such warnings are not given.

`-gnatw.P'
     `Suppress warnings on parameter ordering.'

     This switch suppresses warnings on cases of suspicious parameter
     ordering.

`-gnatwq'
     `Activate warnings on questionable missing parentheses.'

     This switch activates warnings for cases where parentheses are not
     used and the result is potential ambiguity from a readers point of
     view. For example (not a > b) when a and b are modular means ((not
     a) > b) and very likely the programmer intended (not (a > b)).
     Similarly (-x mod 5) means (-(x mod 5)) and quite likely ((-x) mod
     5) was intended. In such situations it seems best to follow the
     rule of always parenthesizing to make the association clear, and
     this warning switch warns if such parentheses are not present. The
     default is that these warnings are given.

`-gnatwQ'
     `Suppress warnings on questionable missing parentheses.'

     This switch suppresses warnings for cases where the association is
     not clear and the use of parentheses is preferred.

`-gnatwr'
     `Activate warnings on redundant constructs.'

     This switch activates warnings for redundant constructs. The
     following is the current list of constructs regarded as redundant:

        * Assignment of an item to itself.

        * Type conversion that converts an expression to its own type.

        * Use of the attribute `Base' where `typ'Base' is the same as
          `typ'.

        * Use of pragma `Pack' when all components are placed by a
          record representation clause.

        * Exception handler containing only a reraise statement (raise
          with no operand) which has no effect.

        * Use of the operator abs on an operand that is known at
          compile time to be non-negative

        * Comparison of boolean expressions to an explicit True value.

     The default is that warnings for redundant constructs are not
     given.

`-gnatwR'
     `Suppress warnings on redundant constructs.'

     This switch suppresses warnings for redundant constructs.

`-gnatw.r'
     `Activate warnings for object renaming function.'

     This switch activates warnings for an object renaming that renames
     a function call, which is equivalent to a constant declaration (as
     opposed to renaming the function itself).  The default is that
     these warnings are given.

`-gnatw.R'
     `Suppress warnings for object renaming function.'

     This switch suppresses warnings for object renaming function.

`-gnatws'
     `Suppress all warnings.'

     This switch completely suppresses the output of all warning
     messages from the GNAT front end, including both warnings that can
     be controlled by switches described in this section, and those
     that are normally given unconditionally. The effect of this
     suppress action can only be cancelled by a subsequent use of the
     switch `-gnatwn'.

     Note that switch `-gnatws' does not suppress warnings from the
     `gcc' back end.  To suppress these back end warnings as well, use
     the switch `-w' in addition to `-gnatws'. Also this switch has no
     effect on the handling of style check messages.

`-gnatw.s'
     `Activate warnings on overridden size clauses.'

     This switch activates warnings on component clauses in record
     representation clauses where the length given overrides that
     specified by an explicit size clause for the component type. A
     warning is similarly given in the array case if a specified
     component size overrides an explicit size clause for the array
     component type.

`-gnatw.S'
     `Suppress warnings on overridden size clauses.'

     This switch suppresses warnings on component clauses in record
     representation clauses that override size clauses, and similar
     warnings when an array component size overrides a size clause.

`-gnatwt'
     `Activate warnings for tracking of deleted conditional code.'

     This switch activates warnings for tracking of code in
     conditionals (IF and CASE statements) that is detected to be dead
     code which cannot be executed, and which is removed by the front
     end. This warning is off by default. This may be useful for
     detecting deactivated code in certified applications.

`-gnatwT'
     `Suppress warnings for tracking of deleted conditional code.'

     This switch suppresses warnings for tracking of deleted
     conditional code.

`-gnatw.t'
     `Activate warnings on suspicious contracts.'

     This switch activates warnings on suspicious contracts. This
     includes warnings on suspicious postconditions (whether a pragma
     `Postcondition' or a `Post' aspect in Ada 2012) and suspicious
     contract cases (pragma or aspect `Contract_Cases'). A function
     postcondition or contract case is suspicious when no postcondition
     or contract case for this function mentions the result of the
     function.  A procedure postcondition or contract case is suspicious
     when it only refers to the pre-state of the procedure, because in
     that case it should rather be expressed as a precondition. This
     switch also controls warnings on suspicious cases of expressions
     typically found in contracts like quantified expressions and uses
     of Update attribute. The default is that such warnings are
     generated.

`-gnatw.T'
     `Suppress warnings on suspicious contracts.'

     This switch suppresses warnings on suspicious contracts.

`-gnatwu'
     `Activate warnings on unused entities.'

     This switch activates warnings to be generated for entities that
     are declared but not referenced, and for units that are `with'ed
     and not referenced. In the case of packages, a warning is also
     generated if no entities in the package are referenced. This means
     that if a with'ed package is referenced but the only references
     are in `use' clauses or `renames' declarations, a warning is still
     generated. A warning is also generated for a generic package that
     is `with'ed but never instantiated.  In the case where a package
     or subprogram body is compiled, and there is a `with' on the
     corresponding spec that is only referenced in the body, a warning
     is also generated, noting that the `with' can be moved to the
     body. The default is that such warnings are not generated.  This
     switch also activates warnings on unreferenced formals (it
     includes the effect of `-gnatwf').

`-gnatwU'
     `Suppress warnings on unused entities.'

     This switch suppresses warnings for unused entities and packages.
     It also turns off warnings on unreferenced formals (and thus
     includes the effect of `-gnatwF').

`-gnatw.u'
     `Activate warnings on unordered enumeration types.'

     This switch causes enumeration types to be considered as
     conceptually unordered, unless an explicit pragma `Ordered' is
     given for the type.  The effect is to generate warnings in clients
     that use explicit comparisons or subranges, since these constructs
     both treat objects of the type as ordered. (A `client' is defined
     as a unit that is other than the unit in which the type is
     declared, or its body or subunits.) Please refer to the
     description of pragma `Ordered' in the `GNAT Reference Manual' for
     further details.  The default is that such warnings are not
     generated.

`-gnatw.U'
     `Deactivate warnings on unordered enumeration types.'

     This switch causes all enumeration types to be considered as
     ordered, so that no warnings are given for comparisons or
     subranges for any type.

`-gnatwv'
     `Activate warnings on unassigned variables.'

     This switch activates warnings for access to variables which may
     not be properly initialized. The default is that such warnings are
     generated.

`-gnatwV'
     `Suppress warnings on unassigned variables.'

     This switch suppresses warnings for access to variables which may
     not be properly initialized.  For variables of a composite type,
     the warning can also be suppressed in Ada 2005 by using a default
     initialization with a box. For example, if Table is an array of
     records whose components are only partially uninitialized, then
     the following code:

         Tab : Table := (others => <>);

     will suppress warnings on subsequent statements that access
     components of variable Tab.

`-gnatw.v'
     `Activate info messages for non-default bit order.'

     This switch activates messages (labeled "info", they are not
     warnings, just informational messages) about the effects of
     non-default bit-order on records to which a component clause is
     applied. The effect of specifying non-default bit ordering is a
     bit subtle (and changed with Ada 2005), so these messages, which
     are given by default, are useful in understanding the exact
     consequences of using this feature.

`-gnatw.V'
     `Suppress info messages for non-default bit order.'

     This switch suppresses information messages for the effects of
     specifying non-default bit order on record components with
     component clauses.

`-gnatww'
     `Activate warnings on wrong low bound assumption.'

     This switch activates warnings for indexing an unconstrained
     string parameter with a literal or S'Length. This is a case where
     the code is assuming that the low bound is one, which is in
     general not true (for example when a slice is passed). The default
     is that such warnings are generated.

`-gnatwW'
     `Suppress warnings on wrong low bound assumption.'

     This switch suppresses warnings for indexing an unconstrained
     string parameter with a literal or S'Length. Note that this
     warning can also be suppressed in a particular case by adding an
     assertion that the lower bound is 1, as shown in the following
     example:

         procedure K (S : String) is
            pragma Assert (S'First = 1);
            ...

`-gnatw.w'
     `Activate warnings on Warnings Off pragmas.'

     This switch activates warnings for use of `pragma Warnings (Off,
     entity)' where either the pragma is entirely useless (because it
     suppresses no warnings), or it could be replaced by `pragma
     Unreferenced' or `pragma Unmodified'.  Also activates warnings for
     the case of Warnings (Off, String), where either there is no
     matching Warnings (On, String), or the Warnings (Off) did not
     suppress any warning.  The default is that these warnings are not
     given.

`-gnatw.W'
     `Suppress warnings on unnecessary Warnings Off pragmas.'

     This switch suppresses warnings for use of `pragma Warnings (Off,
     ...)'.

`-gnatwx'
     `Activate warnings on Export/Import pragmas.'

     This switch activates warnings on Export/Import pragmas when the
     compiler detects a possible conflict between the Ada and foreign
     language calling sequences. For example, the use of default
     parameters in a convention C procedure is dubious because the C
     compiler cannot supply the proper default, so a warning is issued.
     The default is that such warnings are generated.

`-gnatwX'
     `Suppress warnings on Export/Import pragmas.'

     This switch suppresses warnings on Export/Import pragmas.  The
     sense of this is that you are telling the compiler that you know
     what you are doing in writing the pragma, and it should not
     complain at you.

`-gnatw.x'
     `Activate warnings for No_Exception_Propagation mode.'

     This switch activates warnings for exception usage when pragma
     Restrictions (No_Exception_Propagation) is in effect. Warnings are
     given for implicit or explicit exception raises which are not
     covered by a local handler, and for exception handlers which do
     not cover a local raise. The default is that these warnings are
     not given.

`-gnatw.X'
     `Disable warnings for No_Exception_Propagation mode.'

     This switch disables warnings for exception usage when pragma
     Restrictions (No_Exception_Propagation) is in effect.

`-gnatwy'
     `Activate warnings for Ada compatibility issues.'

     For the most part, newer versions of Ada are upwards compatible
     with older versions. For example, Ada 2005 programs will almost
     always work when compiled as Ada 2012.  However there are some
     exceptions (for example the fact that `some' is now a reserved
     word in Ada 2012). This switch activates several warnings to help
     in identifying and correcting such incompatibilities. The default
     is that these warnings are generated. Note that at one point Ada
     2005 was called Ada 0Y, hence the choice of character.

`-gnatwY'
     `Disable warnings for Ada compatibility issues.'

     This switch suppresses the warnings intended to help in identifying
     incompatibilities between Ada language versions.

`-gnatw.y'
     `Activate information messages for why package spec needs body.'

     There are a number of cases in which a package spec needs a body.
     For example, the use of pragma Elaborate_Body, or the declaration
     of a procedure specification requiring a completion. This switch
     causes information messages to be output showing why a package
     specification requires a body. This can be useful in the case of a
     large package specification which is unexpectedly requiring a
     body. The default is that such information messages are not output.

`-gnatw.Y'
     `Disable information messages for why package spec needs body.'

     This switch suppresses the output of information messages showing
     why a package specification needs a body.

`-gnatwz'
     `Activate warnings on unchecked conversions.'

     This switch activates warnings for unchecked conversions where the
     types are known at compile time to have different sizes. The
     default is that such warnings are generated. Warnings are also
     generated for subprogram pointers with different conventions.

`-gnatwZ'
     `Suppress warnings on unchecked conversions.'

     This switch suppresses warnings for unchecked conversions where
     the types are known at compile time to have different sizes or
     conventions.

`-gnatw.z'
     `Activate warnings for size not a multiple of alignment.'

     This switch activates warnings for cases of record types with
     specified `Size' and `Alignment' attributes where the size is not
     a multiple of the alignment, resulting in an object size that is
     greater than the specified size. The default is that such warnings
     are generated.

`-gnatw.Z'
     `Suppress warnings for size not a multiple of alignment.'

     This switch suppresses warnings for cases of record types with
     specified `Size' and `Alignment' attributes where the size is not
     a multiple of the alignment, resulting in an object size that is
     greater than the specified size.  The warning can also be
     suppressed by giving an explicit `Object_Size' value.

`-Wunused'
     The warnings controlled by the `-gnatw' switch are generated by
     the front end of the compiler. The `GCC' back end can provide
     additional warnings and they are controlled by the `-W' switch.
     For example, `-Wunused' activates back end warnings for entities
     that are declared but not referenced.

`-Wuninitialized'
     Similarly, `-Wuninitialized' activates the back end warning for
     uninitialized variables. This switch must be used in conjunction
     with an optimization level greater than zero.

`-Wstack-usage=`len''
     Warn if the stack usage of a subprogram might be larger than `len'
     bytes.  See *note Static Stack Usage Analysis: fd. for details.

`-Wall'
     This switch enables most warnings from the `GCC' back end.  The
     code generator detects a number of warning situations that are
     missed by the `GNAT' front end, and this switch can be used to
     activate them.  The use of this switch also sets the default front
     end warning mode to `-gnatwa', that is, most front end warnings
     activated as well.

`-w'
     Conversely, this switch suppresses warnings from the `GCC' back
     end.  The use of this switch also sets the default front end
     warning mode to `-gnatws', that is, front end warnings suppressed
     as well.

`-Werror'
     This switch causes warnings from the `GCC' back end to be treated
     as errors.  The warning string still appears, but the warning
     messages are counted as errors, and prevent the generation of an
     object file.

A string of warning parameters can be used in the same parameter. For
example:

    -gnatwaGe

will turn on all optional warnings except for unrecognized pragma
warnings, and also specify that warnings should be treated as errors.

When no switch `-gnatw' is used, this is equivalent to:

        * `-gnatw.a'

        * `-gnatwB'

        * `-gnatw.b'

        * `-gnatwC'

        * `-gnatw.C'

        * `-gnatwD'

        * `-gnatwF'

        * `-gnatwg'

        * `-gnatwH'

        * `-gnatwi'

        * `-gnatw.I'

        * `-gnatwJ'

        * `-gnatwK'

        * `-gnatwL'

        * `-gnatw.L'

        * `-gnatwM'

        * `-gnatw.m'

        * `-gnatwn'

        * `-gnatwo'

        * `-gnatw.O'

        * `-gnatwP'

        * `-gnatw.P'

        * `-gnatwq'

        * `-gnatwR'

        * `-gnatw.R'

        * `-gnatw.S'

        * `-gnatwT'

        * `-gnatw.T'

        * `-gnatwU'

        * `-gnatwv'

        * `-gnatww'

        * `-gnatw.W'

        * `-gnatwx'

        * `-gnatw.X'

        * `-gnatwy'

        * `-gnatwz'


File: gnat_ugn.info,  Node: Debugging and Assertion Control,  Next: Validity Checking,  Prev: Warning Message Control,  Up: Compiler Switches

4.3.4 Debugging and Assertion Control
-------------------------------------

`-gnata'
     The `-gnata' option is equivalent to the following
     Assertion_Policy pragma:

         pragma Assertion_Policy (Check);

     Which is a shorthand for:

         pragma Assertion_Policy
           (Assert               => Check,
            Static_Predicate     => Check,
            Dynamic_Predicate    => Check,
            Pre                  => Check,
            Pre'Class            => Check,
            Post                 => Check,
            Post'Class           => Check,
            Type_Invariant       => Check,
            Type_Invariant'Class => Check);

     The pragmas `Assert' and `Debug' normally have no effect and are
     ignored. This switch, where `a' stands for assert, causes pragmas
     `Assert' and `Debug' to be activated. This switch also causes
     preconditions, postconditions, subtype predicates, and type
     invariants to be activated.

     The pragmas have the form:

         pragma Assert (<Boolean-expression> [, <static-string-expression>])
         pragma Debug (<procedure call>)
         pragma Type_Invariant (<type-local-name>, <Boolean-expression>)
         pragma Predicate (<type-local-name>, <Boolean-expression>)
         pragma Precondition (<Boolean-expression>, <string-expression>)
         pragma Postcondition (<Boolean-expression>, <string-expression>)

     The aspects have the form:

         with [Pre|Post|Type_Invariant|Dynamic_Predicate|Static_Predicate]
           => <Boolean-expression>;

     The `Assert' pragma causes `Boolean-expression' to be tested.  If
     the result is `True', the pragma has no effect (other than
     possible side effects from evaluating the expression). If the
     result is `False', the exception `Assert_Failure' declared in the
     package `System.Assertions' is raised (passing
     `static-string-expression', if present, as the message associated
     with the exception). If no string expression is given, the default
     is a string containing the file name and line number of the pragma.

     The `Debug' pragma causes `procedure' to be called. Note that
     `pragma Debug' may appear within a declaration sequence, allowing
     debugging procedures to be called between declarations.

     For the aspect specification, the `<Boolean-expression>' is
     evaluated.  If the result is `True', the aspect has no effect. If
     the result is `False', the exception `Assert_Failure' is raised.


File: gnat_ugn.info,  Node: Validity Checking,  Next: Style Checking,  Prev: Debugging and Assertion Control,  Up: Compiler Switches

4.3.5 Validity Checking
-----------------------

The Ada Reference Manual defines the concept of invalid values (see RM
13.9.1). The primary source of invalid values is uninitialized
variables. A scalar variable that is left uninitialized may contain an
invalid value; the concept of invalid does not apply to access or
composite types.

It is an error to read an invalid value, but the RM does not require
run-time checks to detect such errors, except for some minimal checking
to prevent erroneous execution (i.e. unpredictable behavior). This
corresponds to the `-gnatVd' switch below, which is the default. For
example, by default, if the expression of a case statement is invalid,
it will raise Constraint_Error rather than causing a wild jump, and if
an array index on the left-hand side of an assignment is invalid, it
will raise Constraint_Error rather than overwriting an arbitrary memory
location.

The `-gnatVa' may be used to enable additional validity checks, which
are not required by the RM. These checks are often very expensive
(which is why the RM does not require them). These checks are useful in
tracking down uninitialized variables, but they are not usually
recommended for production builds, and in particular we do not
recommend using these extra validity checking options in combination
with optimization, since this can confuse the optimizer.  If
performance is a consideration, leading to the need to optimize, then
the validity checking options should not be used.

The other `-gnatV'`x' switches below allow finer-grained control; you
can enable whichever validity checks you desire. However, for most
debugging purposes, `-gnatVa' is sufficient, and the default `-gnatVd'
(i.e. standard Ada behavior) is usually sufficient for non-debugging
use.

The `-gnatB' switch tells the compiler to assume that all values are
valid (that is, within their declared subtype range) except in the
context of a use of the Valid attribute. This means the compiler can
generate more efficient code, since the range of values is better known
at compile time. However, an uninitialized variable can cause wild
jumps and memory corruption in this mode.

The `-gnatV'`x' switch allows control over the validity checking mode
as described below.  The `x' argument is a string of letters that
indicate validity checks that are performed or not performed in addition
to the default checks required by Ada as described above.

`-gnatVa'
     `All validity checks.'

     All validity checks are turned on.  That is, `-gnatVa' is
     equivalent to `gnatVcdfimorst'.

`-gnatVc'
     `Validity checks for copies.'

     The right hand side of assignments, and the initializing values of
     object declarations are validity checked.

`-gnatVd'
     `Default (RM) validity checks.'

     Some validity checks are done by default following normal Ada
     semantics (RM 13.9.1 (9-11)).  A check is done in case statements
     that the expression is within the range of the subtype. If it is
     not, Constraint_Error is raised.  For assignments to array
     components, a check is done that the expression used as index is
     within the range. If it is not, Constraint_Error is raised.  Both
     these validity checks may be turned off using switch `-gnatVD'.
     They are turned on by default. If `-gnatVD' is specified, a
     subsequent switch `-gnatVd' will leave the checks turned on.
     Switch `-gnatVD' should be used only if you are sure that all such
     expressions have valid values. If you use this switch and invalid
     values are present, then the program is erroneous, and wild jumps
     or memory overwriting may occur.

`-gnatVe'
     `Validity checks for elementary components.'

     In the absence of this switch, assignments to record or array
     components are not validity checked, even if validity checks for
     assignments generally (`-gnatVc') are turned on. In Ada,
     assignment of composite values do not require valid data, but
     assignment of individual components does. So for example, there is
     a difference between copying the elements of an array with a slice
     assignment, compared to assigning element by element in a loop.
     This switch allows you to turn off validity checking for
     components, even when they are assigned component by component.

`-gnatVf'
     `Validity checks for floating-point values.'

     In the absence of this switch, validity checking occurs only for
     discrete values. If `-gnatVf' is specified, then validity checking
     also applies for floating-point values, and NaNs and infinities
     are considered invalid, as well as out of range values for
     constrained types. Note that this means that standard IEEE
     infinity mode is not allowed. The exact contexts in which
     floating-point values are checked depends on the setting of other
     options. For example, `-gnatVif' or `-gnatVfi' (the order does not
     matter) specifies that floating-point parameters of mode `in'
     should be validity checked.

`-gnatVi'
     `Validity checks for `in` mode parameters.'

     Arguments for parameters of mode `in' are validity checked in
     function and procedure calls at the point of call.

`-gnatVm'
     `Validity checks for `in out` mode parameters.'

     Arguments for parameters of mode `in out' are validity checked in
     procedure calls at the point of call. The `'m'' here stands for
     modify, since this concerns parameters that can be modified by the
     call.  Note that there is no specific option to test `out'
     parameters, but any reference within the subprogram will be tested
     in the usual manner, and if an invalid value is copied back, any
     reference to it will be subject to validity checking.

`-gnatVn'
     `No validity checks.'

     This switch turns off all validity checking, including the default
     checking for case statements and left hand side subscripts. Note
     that the use of the switch `-gnatp' suppresses all run-time
     checks, including validity checks, and thus implies `-gnatVn'.
     When this switch is used, it cancels any other `-gnatV' previously
     issued.

`-gnatVo'
     `Validity checks for operator and attribute operands.'

     Arguments for predefined operators and attributes are validity
     checked.  This includes all operators in package `Standard', the
     shift operators defined as intrinsic in package `Interfaces' and
     operands for attributes such as `Pos'. Checks are also made on
     individual component values for composite comparisons, and on the
     expressions in type conversions and qualified expressions. Checks
     are also made on explicit ranges using `..' (e.g., slices, loops
     etc).

`-gnatVp'
     `Validity checks for parameters.'

     This controls the treatment of parameters within a subprogram (as
     opposed to `-gnatVi' and `-gnatVm' which control validity testing
     of parameters on a call. If either of these call options is used,
     then normally an assumption is made within a subprogram that the
     input arguments have been validity checking at the point of call,
     and do not need checking again within a subprogram). If `-gnatVp'
     is set, then this assumption is not made, and parameters are not
     assumed to be valid, so their validity will be checked (or
     rechecked) within the subprogram.

`-gnatVr'
     `Validity checks for function returns.'

     The expression in `return' statements in functions is validity
     checked.

`-gnatVs'
     `Validity checks for subscripts.'

     All subscripts expressions are checked for validity, whether they
     appear on the right side or left side (in default mode only left
     side subscripts are validity checked).

`-gnatVt'
     `Validity checks for tests.'

     Expressions used as conditions in `if', `while' or `exit'
     statements are checked, as well as guard expressions in entry
     calls.

The `-gnatV' switch may be followed by a string of letters to turn on a
series of validity checking options.  For example, `-gnatVcr' specifies
that in addition to the default validity checking, copies and function
return expressions are to be validity checked.  In order to make it
easier to specify the desired combination of effects, the upper case
letters `CDFIMORST' may be used to turn off the corresponding lower
case option.  Thus `-gnatVaM' turns on all validity checking options
except for checking of `**in out**' procedure arguments.

The specification of additional validity checking generates extra code
(and in the case of `-gnatVa' the code expansion can be substantial).
However, these additional checks can be very useful in detecting
uninitialized variables, incorrect use of unchecked conversion, and
other errors leading to invalid values. The use of pragma
`Initialize_Scalars' is useful in conjunction with the extra validity
checking, since this ensures that wherever possible uninitialized
variables have invalid values.

See also the pragma `Validity_Checks' which allows modification of the
validity checking mode at the program source level, and also allows for
temporary disabling of validity checks.


File: gnat_ugn.info,  Node: Style Checking,  Next: Run-Time Checks,  Prev: Validity Checking,  Up: Compiler Switches

4.3.6 Style Checking
--------------------

The `-gnatyx' switch causes the compiler to enforce specified style
rules. A limited set of style rules has been used in writing the GNAT
sources themselves. This switch allows user programs to activate all or
some of these checks. If the source program fails a specified style
check, an appropriate message is given, preceded by the character
sequence '(style)'. This message does not prevent successful
compilation (unless the `-gnatwe' switch is used).

Note that this is by no means intended to be a general facility for
checking arbitrary coding standards. It is simply an embedding of the
style rules we have chosen for the GNAT sources. If you are starting a
project which does not have established style standards, you may find
it useful to adopt the entire set of GNAT coding standards, or some
subset of them.

The string `x' is a sequence of letters or digits indicating the
particular style checks to be performed. The following checks are
defined:

`-gnaty0'
     `Specify indentation level.'

     If a digit from 1-9 appears in the string after `-gnaty' then
     proper indentation is checked, with the digit indicating the
     indentation level required. A value of zero turns off this style
     check.  The general style of required indentation is as specified
     by the examples in the Ada Reference Manual. Full line comments
     must be aligned with the `-' starting on a column that is a
     multiple of the alignment level, or they may be aligned the same
     way as the following non-blank line (this is useful when full line
     comments appear in the middle of a statement, or they may be
     aligned with the source line on the previous non-blank line.

`-gnatya'
     `Check attribute casing.'

     Attribute names, including the case of keywords such as `digits'
     used as attributes names, must be written in mixed case, that is,
     the initial letter and any letter following an underscore must be
     uppercase.  All other letters must be lowercase.

`-gnatyA'
     `Use of array index numbers in array attributes.'

     When using the array attributes First, Last, Range, or Length, the
     index number must be omitted for one-dimensional arrays and is
     required for multi-dimensional arrays.

`-gnatyb'
     `Blanks not allowed at statement end.'

     Trailing blanks are not allowed at the end of statements. The
     purpose of this rule, together with h (no horizontal tabs), is to
     enforce a canonical format for the use of blanks to separate
     source tokens.

`-gnatyB'
     `Check Boolean operators.'

     The use of AND/OR operators is not permitted except in the cases
     of modular operands, array operands, and simple stand-alone
     boolean variables or boolean constants. In all other cases `and
     then'/`or else' are required.

`-gnatyc'
     `Check comments, double space.'

     Comments must meet the following set of rules:

        * The '`-' that starts the column must either start in column
          one, or else at least one blank must precede this sequence.

        * Comments that follow other tokens on a line must have at
          least one blank following the '`-' at the start of the
          comment.

        * Full line comments must have at least two blanks following the
          '`-' that starts the comment, with the following exceptions.

        * A line consisting only of the '`-' characters, possibly
          preceded by blanks is permitted.

        * A comment starting with '`-x' where `x' is a special character
          is permitted.  This allows proper processing of the output
          generated by specialized tools including `gnatprep' (where
          '`-!' is used) and the SPARK annotation language (where '`-#'
          is used). For the purposes of this rule, a special character
          is defined as being in one of the ASCII ranges
          `16#21#...16#2F#' or `16#3A#...16#3F#'.  Note that this usage
          is not permitted in GNAT implementation units (i.e., when
          `-gnatg' is used).

        * A line consisting entirely of minus signs, possibly preceded
          by blanks, is permitted. This allows the construction of box
          comments where lines of minus signs are used to form the top
          and bottom of the box.

        * A comment that starts and ends with '`-' is permitted as long
          as at least one blank follows the initial '`-'. Together with
          the preceding rule, this allows the construction of box
          comments, as shown in the following example:

              ---------------------------
              -- This is a box comment --
              -- with two text lines.  --
              ---------------------------

`-gnatyC'
     `Check comments, single space.'

     This is identical to `c' except that only one space is required
     following the `-' of a comment instead of two.

`-gnatyd'
     `Check no DOS line terminators present.'

     All lines must be terminated by a single ASCII.LF character (in
     particular the DOS line terminator sequence CR/LF is not allowed).

`-gnatye'
     `Check end/exit labels.'

     Optional labels on `end' statements ending subprograms and on
     `exit' statements exiting named loops, are required to be present.

`-gnatyf'
     `No form feeds or vertical tabs.'

     Neither form feeds nor vertical tab characters are permitted in
     the source text.

`-gnatyg'
     `GNAT style mode.'

     The set of style check switches is set to match that used by the
     GNAT sources.  This may be useful when developing code that is
     eventually intended to be incorporated into GNAT. Currently this
     is equivalent to `-gnatwydISux') but additional style switches may
     be added to this set in the future without advance notice.

`-gnatyh'
     `No horizontal tabs.'

     Horizontal tab characters are not permitted in the source text.
     Together with the b (no blanks at end of line) check, this
     enforces a canonical form for the use of blanks to separate source
     tokens.

`-gnatyi'
     `Check if-then layout.'

     The keyword `then' must appear either on the same line as
     corresponding `if', or on a line on its own, lined up under the
     `if'.

`-gnatyI'
     `check mode IN keywords.'

     Mode `in' (the default mode) is not allowed to be given
     explicitly. `in out' is fine, but not `in' on its own.

`-gnatyk'
     `Check keyword casing.'

     All keywords must be in lower case (with the exception of keywords
     such as `digits' used as attribute names to which this check does
     not apply).

`-gnatyl'
     `Check layout.'

     Layout of statement and declaration constructs must follow the
     recommendations in the Ada Reference Manual, as indicated by the
     form of the syntax rules. For example an `else' keyword must be
     lined up with the corresponding `if' keyword.

     There are two respects in which the style rule enforced by this
     check option are more liberal than those in the Ada Reference
     Manual. First in the case of record declarations, it is
     permissible to put the `record' keyword on the same line as the
     `type' keyword, and then the `end' in `end record' must line up
     under `type'.  This is also permitted when the type declaration is
     split on two lines.  For example, any of the following three
     layouts is acceptable:

         type q is record
            a : integer;
            b : integer;
         end record;

         type q is
            record
               a : integer;
               b : integer;
            end record;

         type q is
            record
               a : integer;
               b : integer;
         end record;

     Second, in the case of a block statement, a permitted alternative
     is to put the block label on the same line as the `declare' or
     `begin' keyword, and then line the `end' keyword up under the
     block label. For example both the following are permitted:

         Block : declare
            A : Integer := 3;
         begin
            Proc (A, A);
         end Block;

         Block :
            declare
               A : Integer := 3;
            begin
               Proc (A, A);
            end Block;

     The same alternative format is allowed for loops. For example,
     both of the following are permitted:

         Clear : while J < 10 loop
            A (J) := 0;
         end loop Clear;

         Clear :
            while J < 10 loop
               A (J) := 0;
            end loop Clear;

`-gnatyL'
     `Set maximum nesting level.'

     The maximum level of nesting of constructs (including subprograms,
     loops, blocks, packages, and conditionals) may not exceed the
     given value `nnn'. A value of zero disconnects this style check.

`-gnatym'
     `Check maximum line length.'

     The length of source lines must not exceed 79 characters, including
     any trailing blanks. The value of 79 allows convenient display on
     an 80 character wide device or window, allowing for possible
     special treatment of 80 character lines. Note that this count is of
     characters in the source text. This means that a tab character
     counts as one character in this count and a wide character
     sequence counts as a single character (however many bytes are
     needed in the encoding).

`-gnatyM'
     `Set maximum line length.'

     The length of lines must not exceed the given value `nnn'. The
     maximum value that can be specified is 32767.  If neither style
     option for setting the line length is used, then the default is
     255. This also controls the maximum length of lexical elements,
     where the only restriction is that they must fit on a single line.

`-gnatyn'
     `Check casing of entities in Standard.'

     Any identifier from Standard must be cased to match the
     presentation in the Ada Reference Manual (for example, `Integer'
     and `ASCII.NUL').

`-gnatyN'
     `Turn off all style checks.'

     All style check options are turned off.

`-gnatyo'
     `Check order of subprogram bodies.'

     All subprogram bodies in a given scope (e.g., a package body) must
     be in alphabetical order. The ordering rule uses normal Ada rules
     for comparing strings, ignoring casing of letters, except that if
     there is a trailing numeric suffix, then the value of this suffix
     is used in the ordering (e.g., Junk2 comes before Junk10).

`-gnatyO'
     `Check that overriding subprograms are explicitly marked as such.'

     This applies to all subprograms of a derived type that override a
     primitive operation of the type, for both tagged and untagged
     types. In particular, the declaration of a primitive operation of
     a type extension that overrides an inherited operation must carry
     an overriding indicator. Another case is the declaration of a
     function that overrides a predefined operator (such as an equality
     operator).

`-gnatyp'
     `Check pragma casing.'

     Pragma names must be written in mixed case, that is, the initial
     letter and any letter following an underscore must be uppercase.
     All other letters must be lowercase. An exception is that
     SPARK_Mode is allowed as an alternative for Spark_Mode.

`-gnatyr'
     `Check references.'

     All identifier references must be cased in the same way as the
     corresponding declaration. No specific casing style is imposed on
     identifiers. The only requirement is for consistency of references
     with declarations.

`-gnatys'
     `Check separate specs.'

     Separate declarations ('specs') are required for subprograms (a
     body is not allowed to serve as its own declaration). The only
     exception is that parameterless library level procedures are not
     required to have a separate declaration. This exception covers the
     most frequent form of main program procedures.

`-gnatyS'
     `Check no statements after then/else.'

     No statements are allowed on the same line as a `then' or `else'
     keyword following the keyword in an `if' statement. `or else' and
     `and then' are not affected, and a special exception allows a
     pragma to appear after `else'.

`-gnatyt'
     `Check token spacing.'

     The following token spacing rules are enforced:

        * The keywords `abs' and `not' must be followed by a space.

        * The token `=>' must be surrounded by spaces.

        * The token `<>' must be preceded by a space or a left
          parenthesis.

        * Binary operators other than `**' must be surrounded by spaces.
          There is no restriction on the layout of the `**' binary
          operator.

        * Colon must be surrounded by spaces.

        * Colon-equal (assignment, initialization) must be surrounded
          by spaces.

        * Comma must be the first non-blank character on the line, or be
          immediately preceded by a non-blank character, and must be
          followed by a space.

        * If the token preceding a left parenthesis ends with a letter
          or digit, then a space must separate the two tokens.

        * If the token following a right parenthesis starts with a
          letter or digit, then a space must separate the two tokens.

        * A right parenthesis must either be the first non-blank
          character on a line, or it must be preceded by a non-blank
          character.

        * A semicolon must not be preceded by a space, and must not be
          followed by a non-blank character.

        * A unary plus or minus may not be followed by a space.

        * A vertical bar must be surrounded by spaces.

     Exactly one blank (and no other white space) must appear between a
     `not' token and a following `in' token.

`-gnatyu'
     `Check unnecessary blank lines.'

     Unnecessary blank lines are not allowed. A blank line is considered
     unnecessary if it appears at the end of the file, or if more than
     one blank line occurs in sequence.

`-gnatyx'
     `Check extra parentheses.'

     Unnecessary extra level of parentheses (C-style) are not allowed
     around conditions in `if' statements, `while' statements and
     `exit' statements.

`-gnatyy'
     `Set all standard style check options.'

     This is equivalent to `gnaty3aAbcefhiklmnprst', that is all
     checking options enabled with the exception of `-gnatyB',
     `-gnatyd', `-gnatyI', `-gnatyLnnn', `-gnatyo', `-gnatyO',
     `-gnatyS', `-gnatyu', and `-gnatyx'.

`-gnaty-'
     `Remove style check options.'

     This causes any subsequent options in the string to act as
     canceling the corresponding style check option. To cancel maximum
     nesting level control, use `L' parameter witout any integer value
     after that, because any digit following `-' in the parameter
     string of the `-gnaty' option will be threated as canceling
     indentation check. The same is true for `M' parameter. `y' and `N'
     parameters are not allowed after `-'.

`-gnaty+'
     `Enable style check options.'

     This causes any subsequent options in the string to enable the
     corresponding style check option. That is, it cancels the effect
     of a previous -, if any.

In the above rules, appearing in column one is always permitted, that
is, counts as meeting either a requirement for a required preceding
space, or as meeting a requirement for no preceding space.

Appearing at the end of a line is also always permitted, that is, counts
as meeting either a requirement for a following space, or as meeting a
requirement for no following space.

If any of these style rules is violated, a message is generated giving
details on the violation. The initial characters of such messages are
always '`(style)'. Note that these messages are treated as warning
messages, so they normally do not prevent the generation of an object
file. The `-gnatwe' switch can be used to treat warning messages,
including style messages, as fatal errors.

The switch `-gnaty' on its own (that is not followed by any letters or
digits) is equivalent to the use of `-gnatyy' as described above, that
is all built-in standard style check options are enabled.

The switch `-gnatyN' clears any previously set style checks.


File: gnat_ugn.info,  Node: Run-Time Checks,  Next: Using gcc for Syntax Checking,  Prev: Style Checking,  Up: Compiler Switches

4.3.7 Run-Time Checks
---------------------

By default, the following checks are suppressed: stack overflow checks,
and checks for access before elaboration on subprogram calls. All other
checks, including overflow checks, range checks and array bounds
checks, are turned on by default. The following `gcc' switches refine
this default behavior.

`-gnatp'
     This switch causes the unit to be compiled as though `pragma
     Suppress (All_checks)' had been present in the source. Validity
     checks are also eliminated (in other words `-gnatp' also implies
     `-gnatVn'.  Use this switch to improve the performance of the code
     at the expense of safety in the presence of invalid data or
     program bugs.

     Note that when checks are suppressed, the compiler is allowed, but
     not required, to omit the checking code. If the run-time cost of
     the checking code is zero or near-zero, the compiler will generate
     it even if checks are suppressed. In particular, if the compiler
     can prove that a certain check will necessarily fail, it will
     generate code to do an unconditional 'raise', even if checks are
     suppressed. The compiler warns in this case. Another case in which
     checks may not be eliminated is when they are embedded in certain
     run time routines such as math library routines.

     Of course, run-time checks are omitted whenever the compiler can
     prove that they will not fail, whether or not checks are
     suppressed.

     Note that if you suppress a check that would have failed, program
     execution is erroneous, which means the behavior is totally
     unpredictable. The program might crash, or print wrong answers, or
     do anything else. It might even do exactly what you wanted it to do
     (and then it might start failing mysteriously next week or next
     year). The compiler will generate code based on the assumption that
     the condition being checked is true, which can result in erroneous
     execution if that assumption is wrong.

     The checks subject to suppression include all the checks defined
     by the Ada standard, the additional implementation defined checks
     `Alignment_Check', `Duplicated_Tag_Check', `Predicate_Check',
     Container_Checks, Tampering_Check, and `Validity_Check', as well
     as any checks introduced using `pragma Check_Name'. Note that
     `Atomic_Synchronization' is not automatically suppressed by use of
     this option.

     If the code depends on certain checks being active, you can use
     pragma `Unsuppress' either as a configuration pragma or as a local
     pragma to make sure that a specified check is performed even if
     `gnatp' is specified.

     The `-gnatp' switch has no effect if a subsequent `-gnat-p' switch
     appears.

`-gnat-p'
     This switch cancels the effect of a previous `gnatp' switch.

`-gnato??'
     This switch controls the mode used for computing intermediate
     arithmetic integer operations, and also enables overflow checking.
     For a full description of overflow mode and checking control, see
     the 'Overflow Check Handling in GNAT' appendix in this User's
     Guide.

     Overflow checks are always enabled by this switch. The argument
     controls the mode, using the codes

    `1 = STRICT'
          In STRICT mode, intermediate operations are always done using
          the base type, and overflow checking ensures that the result
          is within the base type range.

    `2 = MINIMIZED'
          In MINIMIZED mode, overflows in intermediate operations are
          avoided where possible by using a larger integer type for the
          computation (typically `Long_Long_Integer'). Overflow
          checking ensures that the result fits in this larger integer
          type.

    `3 = ELIMINATED'
          In ELIMINATED mode, overflows in intermediate operations are
          avoided by using multi-precision arithmetic. In this case,
          overflow checking has no effect on intermediate operations
          (since overflow is impossible).

     If two digits are present after `-gnato' then the first digit sets
     the mode for expressions outside assertions, and the second digit
     sets the mode for expressions within assertions. Here assertions
     is used in the technical sense (which includes for example
     precondition and postcondition expressions).

     If one digit is present, the corresponding mode is applicable to
     both expressions within and outside assertion expressions.

     If no digits are present, the default is to enable overflow checks
     and set STRICT mode for both kinds of expressions. This is
     compatible with the use of `-gnato' in previous versions of GNAT.

     Note that the `-gnato??' switch does not affect the code generated
     for any floating-point operations; it applies only to integer
     semantics.  For floating-point, GNAT has the `Machine_Overflows'
     attribute set to `False' and the normal mode of operation is to
     generate IEEE NaN and infinite values on overflow or invalid
     operations (such as dividing 0.0 by 0.0).

     The reason that we distinguish overflow checking from other kinds
     of range constraint checking is that a failure of an overflow
     check, unlike for example the failure of a range check, can result
     in an incorrect value, but cannot cause random memory destruction
     (like an out of range subscript), or a wild jump (from an out of
     range case value). Overflow checking is also quite expensive in
     time and space, since in general it requires the use of double
     length arithmetic.

     Note again that the default is `-gnato11' (equivalent to
     `-gnato1'), so overflow checking is performed in STRICT mode by
     default.

`-gnatE'
     Enables dynamic checks for access-before-elaboration on subprogram
     calls and generic instantiations.  Note that `-gnatE' is not
     necessary for safety, because in the default mode, GNAT ensures
     statically that the checks would not fail.  For full details of
     the effect and use of this switch, *note Compiling with gcc: 1e.

`-fstack-check'
     Activates stack overflow checking. For full details of the effect
     and use of this switch see *note Stack Overflow Checking: fc.

The setting of these switches only controls the default setting of the
checks. You may modify them using either `Suppress' (to remove checks)
or `Unsuppress' (to add back suppressed checks) pragmas in the program
source.


File: gnat_ugn.info,  Node: Using gcc for Syntax Checking,  Next: Using gcc for Semantic Checking,  Prev: Run-Time Checks,  Up: Compiler Switches

4.3.8 Using `gcc' for Syntax Checking
-------------------------------------

`-gnats'
     The `s' stands for 'syntax'.

     Run GNAT in syntax checking only mode. For example, the command

         $ gcc -c -gnats x.adb

     compiles file `x.adb' in syntax-check-only mode. You can check a
     series of files in a single command , and can use wild cards to
     specify such a group of files.  Note that you must specify the
     `-c' (compile only) flag in addition to the `-gnats' flag.

     You may use other switches in conjunction with `-gnats'. In
     particular, `-gnatl' and `-gnatv' are useful to control the format
     of any generated error messages.

     When the source file is empty or contains only empty lines and/or
     comments, the output is a warning:

         $ gcc -c -gnats -x ada toto.txt
         toto.txt:1:01: warning: empty file, contains no compilation units
         $

     Otherwise, the output is simply the error messages, if any. No
     object file or ALI file is generated by a syntax-only compilation.
     Also, no units other than the one specified are accessed. For
     example, if a unit `X' `with's a unit `Y', compiling unit `X' in
     syntax check only mode does not access the source file containing
     unit `Y'.

     Normally, GNAT allows only a single unit in a source file.
     However, this restriction does not apply in syntax-check-only
     mode, and it is possible to check a file containing multiple
     compilation units concatenated together. This is primarily used by
     the `gnatchop' utility (*note Renaming Files with gnatchop: 38.).


File: gnat_ugn.info,  Node: Using gcc for Semantic Checking,  Next: Compiling Different Versions of Ada,  Prev: Using gcc for Syntax Checking,  Up: Compiler Switches

4.3.9 Using `gcc' for Semantic Checking
---------------------------------------

`-gnatc'
     The `c' stands for 'check'.  Causes the compiler to operate in
     semantic check mode, with full checking for all illegalities
     specified in the Ada Reference Manual, but without generation of
     any object code (no object file is generated).

     Because dependent files must be accessed, you must follow the GNAT
     semantic restrictions on file structuring to operate in this mode:

        * The needed source files must be accessible (see *note Search
          Paths and the Run-Time Library (RTL): 8e.).

        * Each file must contain only one compilation unit.

        * The file name and unit name must match (*note File Naming
          Rules: 54.).

     The output consists of error messages as appropriate. No object
     file is generated. An `ALI' file is generated for use in the
     context of cross-reference tools, but this file is marked as not
     being suitable for binding (since no object file is generated).
     The checking corresponds exactly to the notion of legality in the
     Ada Reference Manual.

     Any unit can be compiled in semantics-checking-only mode, including
     units that would not normally be compiled (subunits, and
     specifications where a separate body is present).


File: gnat_ugn.info,  Node: Compiling Different Versions of Ada,  Next: Character Set Control,  Prev: Using gcc for Semantic Checking,  Up: Compiler Switches

4.3.10 Compiling Different Versions of Ada
------------------------------------------

The switches described in this section allow you to explicitly specify
the version of the Ada language that your programs are written in.  The
default mode is Ada 2012, but you can also specify Ada 95, Ada 2005
mode, or indicate Ada 83 compatibility mode.

`-gnat83' (Ada 83 Compatibility Mode)
     Although GNAT is primarily an Ada 95 / Ada 2005 compiler, this
     switch specifies that the program is to be compiled in Ada 83
     mode. With `-gnat83', GNAT rejects most post-Ada 83 extensions and
     applies Ada 83 semantics where this can be done easily.  It is not
     possible to guarantee this switch does a perfect job; some subtle
     tests, such as are found in earlier ACVC tests (and that have been
     removed from the ACATS suite for Ada 95), might not compile
     correctly.  Nevertheless, this switch may be useful in some
     circumstances, for example where, due to contractual reasons,
     existing code needs to be maintained using only Ada 83 features.

     With few exceptions (most notably the need to use `<>' on
     unconstrained generic formal parameters, the use of the new Ada 95
     / Ada 2005 reserved words, and the use of packages with optional
     bodies), it is not necessary to specify the `-gnat83' switch when
     compiling Ada 83 programs, because, with rare exceptions, Ada 95
     and Ada 2005 are upwardly compatible with Ada 83. Thus a correct
     Ada 83 program is usually also a correct program in these later
     versions of the language standard. For further information please
     refer to the `Compatibility_and_Porting_Guide' chapter in the
     `GNAT Reference Manual'.

`-gnat95' (Ada 95 mode)
     This switch directs the compiler to implement the Ada 95 version
     of the language.  Since Ada 95 is almost completely upwards
     compatible with Ada 83, Ada 83 programs may generally be compiled
     using this switch (see the description of the `-gnat83' switch for
     further information about Ada 83 mode).  If an Ada 2005 program is
     compiled in Ada 95 mode, uses of the new Ada 2005 features will
     cause error messages or warnings.

     This switch also can be used to cancel the effect of a previous
     `-gnat83', `-gnat05/2005', or `-gnat12/2012' switch earlier in the
     command line.

`-gnat05' or `-gnat2005' (Ada 2005 mode)
     This switch directs the compiler to implement the Ada 2005 version
     of the language, as documented in the official Ada standards
     document.  Since Ada 2005 is almost completely upwards compatible
     with Ada 95 (and thus also with Ada 83), Ada 83 and Ada 95 programs
     may generally be compiled using this switch (see the description
     of the `-gnat83' and `-gnat95' switches for further information).

`-gnat12' or `-gnat2012' (Ada 2012 mode)
     This switch directs the compiler to implement the Ada 2012 version
     of the language (also the default).  Since Ada 2012 is almost
     completely upwards compatible with Ada 2005 (and thus also with
     Ada 83, and Ada 95), Ada 83 and Ada 95 programs may generally be
     compiled using this switch (see the description of the `-gnat83',
     `-gnat95', and `-gnat05/2005' switches for further information).

`-gnatX' (Enable GNAT Extensions)
     This switch directs the compiler to implement the latest version
     of the language (currently Ada 2012) and also to enable certain
     GNAT implementation extensions that are not part of any Ada
     standard. For a full list of these extensions, see the GNAT
     reference manual.


File: gnat_ugn.info,  Node: Character Set Control,  Next: File Naming Control,  Prev: Compiling Different Versions of Ada,  Up: Compiler Switches

4.3.11 Character Set Control
----------------------------

`-gnati`c''
     Normally GNAT recognizes the Latin-1 character set in source
     program identifiers, as described in the Ada Reference Manual.
     This switch causes GNAT to recognize alternate character sets in
     identifiers. `c' is a single character  indicating the character
     set, as follows:

     `1'            ISO 8859-1 (Latin-1) identifiers
     `2'            ISO 8859-2 (Latin-2) letters allowed in identifiers
     `3'            ISO 8859-3 (Latin-3) letters allowed in identifiers
     `4'            ISO 8859-4 (Latin-4) letters allowed in identifiers
     `5'            ISO 8859-5 (Cyrillic) letters allowed in identifiers
     `9'            ISO 8859-15 (Latin-9) letters allowed in identifiers
     `p'            IBM PC letters (code page 437) allowed in identifiers
     `8'            IBM PC letters (code page 850) allowed in identifiers
     `f'            Full upper-half codes allowed in identifiers
     `n'            No upper-half codes allowed in identifiers
     `w'            Wide-character codes (that is, codes greater than 255)
                    allowed in identifiers

     See *note Foreign Language Representation: 40. for full details on
     the implementation of these character sets.

`-gnatW`e''
     Specify the method of encoding for wide characters.  `e' is one of
     the following:

     `h'            Hex encoding (brackets coding also recognized)
     `u'            Upper half encoding (brackets encoding also recognized)
     `s'            Shift/JIS encoding (brackets encoding also recognized)
     `e'            EUC encoding (brackets encoding also recognized)
     `8'            UTF-8 encoding (brackets encoding also recognized)
     `b'            Brackets encoding only (default value)

     For full details on these encoding methods see *note
     Wide_Character Encodings: 50.  Note that brackets coding is always
     accepted, even if one of the other options is specified, so for
     example `-gnatW8' specifies that both brackets and UTF-8 encodings
     will be recognized. The units that are with'ed directly or
     indirectly will be scanned using the specified representation
     scheme, and so if one of the non-brackets scheme is used, it must
     be used consistently throughout the program. However, since
     brackets encoding is always recognized, it may be conveniently
     used in standard libraries, allowing these libraries to be used
     with any of the available coding schemes.

     Note that brackets encoding only applies to program text. Within
     comments, brackets are considered to be normal graphic characters,
     and bracket sequences are never recognized as wide characters.

     If no `-gnatW?' parameter is present, then the default
     representation is normally Brackets encoding only. However, if the
     first three characters of the file are 16#EF# 16#BB# 16#BF# (the
     standard byte order mark or BOM for UTF-8), then these three
     characters are skipped and the default representation for the file
     is set to UTF-8.

     Note that the wide character representation that is specified
     (explicitly or by default) for the main program also acts as the
     default encoding used for Wide_Text_IO files if not specifically
     overridden by a WCEM form parameter.

When no `-gnatW?' is specified, then characters (other than wide
characters represented using brackets notation) are treated as 8-bit
Latin-1 codes. The codes recognized are the Latin-1 graphic characters,
and ASCII format effectors (CR, LF, HT, VT). Other lower half control
characters in the range 16#00#..16#1F# are not accepted in program text
or in comments. Upper half control characters (16#80#..16#9F#) are
rejected in program text, but allowed and ignored in comments. Note in
particular that the Next Line (NEL) character whose encoding is 16#85#
is not recognized as an end of line in this default mode. If your
source program contains instances of the NEL character used as a line
terminator, you must use UTF-8 encoding for the whole source program.
In default mode, all lines must be ended by a standard end of line
sequence (CR, CR/LF, or LF).

Note that the convention of simply accepting all upper half characters
in comments means that programs that use standard ASCII for program
text, but UTF-8 encoding for comments are accepted in default mode,
providing that the comments are ended by an appropriate (CR, or CR/LF,
or LF) line terminator.  This is a common mode for many programs with
foreign language comments.


File: gnat_ugn.info,  Node: File Naming Control,  Next: Subprogram Inlining Control,  Prev: Character Set Control,  Up: Compiler Switches

4.3.12 File Naming Control
--------------------------

`-gnatk`n''
     Activates file name 'krunching'. `n', a decimal integer in the
     range 1-999, indicates the maximum allowable length of a file name
     (not including the `.ads' or `.adb' extension). The default is not
     to enable file name krunching.

     For the source file naming rules, *note File Naming Rules: 54.


File: gnat_ugn.info,  Node: Subprogram Inlining Control,  Next: Auxiliary Output Control,  Prev: File Naming Control,  Up: Compiler Switches

4.3.13 Subprogram Inlining Control
----------------------------------

`-gnatn[12]'
     The `n' here is intended to suggest the first syllable of the word
     'inline'.  GNAT recognizes and processes `Inline' pragmas.
     However, for the inlining to actually occur, optimization must be
     enabled and, in order to enable inlining of subprograms specified
     by pragma `Inline', you must also specify this switch.  In the
     absence of this switch, GNAT does not attempt inlining and does
     not need to access the bodies of subprograms for which `pragma
     Inline' is specified if they are not in the current unit.

     You can optionally specify the inlining level: 1 for moderate
     inlining across modules, which is a good compromise between
     compilation times and performances at run time, or 2 for full
     inlining across modules, which may bring about longer compilation
     times. If no inlining level is specified, the compiler will pick
     it based on the optimization level: 1 for `-O1', `-O2' or `-Os'
     and 2 for `-O3'.

     If you specify this switch the compiler will access these bodies,
     creating an extra source dependency for the resulting object file,
     and where possible, the call will be inlined.  For further details
     on when inlining is possible see *note Inlining of Subprograms:
     117.

`-gnatN'
     This switch activates front-end inlining which also generates
     additional dependencies.

     When using a gcc-based back end (in practice this means using any
     version of GNAT other than the JGNAT, .NET or GNAAMP versions),
     then the use of `-gnatN' is deprecated, and the use of `-gnatn' is
     preferred.  Historically front end inlining was more extensive
     than the gcc back end inlining, but that is no longer the case.


File: gnat_ugn.info,  Node: Auxiliary Output Control,  Next: Debugging Control,  Prev: Subprogram Inlining Control,  Up: Compiler Switches

4.3.14 Auxiliary Output Control
-------------------------------

`-gnatt'
     Causes GNAT to write the internal tree for a unit to a file (with
     the extension `.adt'.  This not normally required, but is used by
     separate analysis tools.  Typically these tools do the necessary
     compilations automatically, so you should not have to specify this
     switch in normal operation.  Note that the combination of switches
     `-gnatct' generates a tree in the form required by ASIS
     applications.

`-gnatu'
     Print a list of units required by this compilation on `stdout'.
     The listing includes all units on which the unit being compiled
     depends either directly or indirectly.

`-pass-exit-codes'
     If this switch is not used, the exit code returned by `gcc' when
     compiling multiple files indicates whether all source files have
     been successfully used to generate object files or not.

     When `-pass-exit-codes' is used, `gcc' exits with an extended exit
     status and allows an integrated development environment to better
     react to a compilation failure. Those exit status are:

     `5'            There was an error in at least one source file.
     `3'            At least one source file did not generate an object file.
     `2'            The compiler died unexpectedly (internal error for example).
     `0'            An object file has been generated for every source file.



File: gnat_ugn.info,  Node: Debugging Control,  Next: Exception Handling Control,  Prev: Auxiliary Output Control,  Up: Compiler Switches

4.3.15 Debugging Control
------------------------

 
`-gnatd`x''
     Activate internal debugging switches. `x' is a letter or digit, or
     string of letters or digits, which specifies the type of debugging
     outputs desired. Normally these are used only for internal
     development or system debugging purposes. You can find full
     documentation for these switches in the body of the `Debug' unit
     in the compiler source file `debug.adb'.

`-gnatG[=`nn']'
     This switch causes the compiler to generate auxiliary output
     containing a pseudo-source listing of the generated expanded code.
     Like most Ada compilers, GNAT works by first transforming the high
     level Ada code into lower level constructs. For example, tasking
     operations are transformed into calls to the tasking run-time
     routines. A unique capability of GNAT is to list this expanded
     code in a form very close to normal Ada source.  This is very
     useful in understanding the implications of various Ada usage on
     the efficiency of the generated code. There are many cases in Ada
     (e.g., the use of controlled types), where simple Ada statements
     can generate a lot of run-time code. By using `-gnatG' you can
     identify these cases, and consider whether it may be desirable to
     modify the coding approach to improve efficiency.

     The optional parameter `nn' if present after -gnatG specifies an
     alternative maximum line length that overrides the normal default
     of 72.  This value is in the range 40-999999, values less than 40
     being silently reset to 40. The equal sign is optional.

     The format of the output is very similar to standard Ada source,
     and is easily understood by an Ada programmer. The following
     special syntactic additions correspond to low level features used
     in the generated code that do not have any exact analogies in pure
     Ada source form. The following is a partial list of these special
     constructions. See the spec of package `Sprint' in file
     `sprint.ads' for a full list.

     If the switch `-gnatL' is used in conjunction with `-gnatG', then
     the original source lines are interspersed in the expanded source
     (as comment lines with the original line number).

    `new `xxx' [storage_pool = `yyy']'
          Shows the storage pool being used for an allocator.

    `at end `procedure-name';'
          Shows the finalization (cleanup) procedure for a scope.

    `(if `expr' then `expr' else `expr')'
          Conditional expression equivalent to the `x?y:z' construction
          in C.

    ``target'^(`source')'
          A conversion with floating-point truncation instead of
          rounding.

    ``target'?(`source')'
          A conversion that bypasses normal Ada semantic checking. In
          particular enumeration types and fixed-point types are
          treated simply as integers.

    ``target'?^(`source')'
          Combines the above two cases.

     ``x' #/ `y''

     ``x' #mod `y''

     ``x' # `y''

    ``x' #rem `y''
          A division or multiplication of fixed-point values which are
          treated as integers without any kind of scaling.

    `free `expr' [storage_pool = `xxx']'
          Shows the storage pool associated with a `free' statement.

    `[subtype or type declaration]'
          Used to list an equivalent declaration for an internally
          generated type that is referenced elsewhere in the listing.

    `freeze `type-name' [`actions']'
          Shows the point at which `type-name' is frozen, with possible
          associated actions to be performed at the freeze point.

    `reference `itype''
          Reference (and hence definition) to internal type `itype'.

    ``function-name'! (`arg', `arg', `arg')'
          Intrinsic function call.

    ``label-name' : label'
          Declaration of label `labelname'.

    `#$ `subprogram-name''
          An implicit call to a run-time support routine (to meet the
          requirement of H.3.1(9) in a convenient manner).

    ``expr' && `expr' && `expr' ... && `expr''
          A multiple concatenation (same effect as `expr' & `expr' &
          `expr', but handled more efficiently).

    `[constraint_error]'
          Raise the `Constraint_Error' exception.

    ``expression''reference'
          A pointer to the result of evaluating {expression}.

    ``target-type'!(`source-expression')'
          An unchecked conversion of `source-expression' to
          `target-type'.

    `[`numerator'/`denominator']'
          Used to represent internal real literals (that) have no exact
          representation in base 2-16 (for example, the result of
          compile time evaluation of the expression 1.0/27.0).

`-gnatD[=nn]'
     When used in conjunction with `-gnatG', this switch causes the
     expanded source, as described above for `-gnatG' to be written to
     files with names `xxx.dg', where `xxx' is the normal file name,
     instead of to the standard output file. For example, if the source
     file name is `hello.adb', then a file `hello.adb.dg' will be
     written.  The debugging information generated by the `gcc' `-g'
     switch will refer to the generated `xxx.dg' file. This allows you
     to do source level debugging using the generated code which is
     sometimes useful for complex code, for example to find out exactly
     which part of a complex construction raised an exception. This
     switch also suppress generation of cross-reference information (see
     `-gnatx') since otherwise the cross-reference information would
     refer to the `.dg' file, which would cause confusion since this is
     not the original source file.

     Note that `-gnatD' actually implies `-gnatG' automatically, so it
     is not necessary to give both options.  In other words `-gnatD' is
     equivalent to `-gnatDG').

     If the switch `-gnatL' is used in conjunction with `-gnatDG', then
     the original source lines are interspersed in the expanded source
     (as comment lines with the original line number).

     The optional parameter `nn' if present after -gnatD specifies an
     alternative maximum line length that overrides the normal default
     of 72.  This value is in the range 40-999999, values less than 40
     being silently reset to 40. The equal sign is optional.

`-gnatr'
     This switch causes pragma Restrictions to be treated as
     Restriction_Warnings so that violation of restrictions causes
     warnings rather than illegalities.  This is useful during the
     development process when new restrictions are added or
     investigated. The switch also causes pragma Profile to be treated
     as Profile_Warnings, and pragma Restricted_Run_Time and pragma
     Ravenscar set restriction warnings rather than restrictions.

`-gnatR[0|1|2|3[s]]'
     This switch controls output from the compiler of a listing showing
     representation information for declared types and objects. For
     `-gnatR0', no information is output (equivalent to omitting the
     `-gnatR' switch). For `-gnatR1' (which is the default, so `-gnatR'
     with no parameter has the same effect), size and alignment
     information is listed for declared array and record types. For
     `-gnatR2', size and alignment information is listed for all
     declared types and objects. The `Linker_Section' is also listed
     for any entity for which the `Linker_Section' is set explicitly or
     implicitly (the latter case occurs for objects of a type for which
     a `Linker_Section' is set).

     Finally `-gnatR3' includes symbolic expressions for values that
     are computed at run time for variant records. These symbolic
     expressions have a mostly obvious format with #n being used to
     represent the value of the n'th discriminant. See source files
     `repinfo.ads/adb' in the `GNAT' sources for full details on the
     format of `-gnatR3' output. If the switch is followed by an s
     (e.g., `-gnatR2s'), then the output is to a file with the name
     `file.rep' where file is the name of the corresponding source file.

`-gnatRm[s]'
     This form of the switch controls output of subprogram conventions
     and parameter passing mechanisms for all subprograms. A following
     `s' means output to a file as described above.

     Note that it is possible for record components to have zero size.
     In this case, the component clause uses an obvious extension of
     permitted Ada syntax, for example `at 0 range 0 .. -1'.

     Representation information requires that code be generated (since
     it is the code generator that lays out complex data structures).
     If an attempt is made to output representation information when no
     code is generated, for example when a subunit is compiled on its
     own, then no information can be generated and the compiler outputs
     a message to this effect.

`-gnatS'
     The use of the switch `-gnatS' for an Ada compilation will cause
     the compiler to output a representation of package Standard in a
     form very close to standard Ada. It is not quite possible to do
     this entirely in standard Ada (since new numeric base types cannot
     be created in standard Ada), but the output is easily readable to
     any Ada programmer, and is useful to determine the characteristics
     of target dependent types in package Standard.

`-gnatx'
     Normally the compiler generates full cross-referencing information
     in the `ALI' file. This information is used by a number of tools,
     including `gnatfind' and `gnatxref'. The `-gnatx' switch
     suppresses this information. This saves some space and may slightly
     speed up compilation, but means that these tools cannot be used.


File: gnat_ugn.info,  Node: Exception Handling Control,  Next: Units to Sources Mapping Files,  Prev: Debugging Control,  Up: Compiler Switches

4.3.16 Exception Handling Control
---------------------------------

GNAT uses two methods for handling exceptions at run-time. The
`setjmp/longjmp' method saves the context when entering a frame with an
exception handler. Then when an exception is raised, the context can be
restored immediately, without the need for tracing stack frames. This
method provides very fast exception propagation, but introduces
significant overhead for the use of exception handlers, even if no
exception is raised.

The other approach is called 'zero cost' exception handling.  With this
method, the compiler builds static tables to describe the exception
ranges. No dynamic code is required when entering a frame containing an
exception handler. When an exception is raised, the tables are used to
control a back trace of the subprogram invocation stack to locate the
required exception handler. This method has considerably poorer
performance for the propagation of exceptions, but there is no overhead
for exception handlers if no exception is raised. Note that in this
mode and in the context of mixed Ada and C/C++ programming, to
propagate an exception through a C/C++ code, the C/C++ code must be
compiled with the `-funwind-tables' GCC's option.

The following switches may be used to control which of the two
exception handling methods is used.

`--RTS=sjlj'
     This switch causes the setjmp/longjmp run-time (when available) to
     be used for exception handling. If the default mechanism for the
     target is zero cost exceptions, then this switch can be used to
     modify this default, and must be used for all units in the
     partition.  This option is rarely used. One case in which it may be
     advantageous is if you have an application where exception raising
     is common and the overall performance of the application is
     improved by favoring exception propagation.

`--RTS=zcx'
     This switch causes the zero cost approach to be used for exception
     handling. If this is the default mechanism for the target (see
     below), then this switch is unneeded. If the default mechanism for
     the target is setjmp/longjmp exceptions, then this switch can be
     used to modify this default, and must be used for all units in the
     partition.  This option can only be used if the zero cost approach
     is available for the target in use, otherwise it will generate an
     error.

The same option `-RTS' must be used both for `gcc' and `gnatbind'.
Passing this option to `gnatmake' (*note Switches for gnatmake: e2.)
will ensure the required consistency through the compilation and
binding steps.


File: gnat_ugn.info,  Node: Units to Sources Mapping Files,  Next: Code Generation Control,  Prev: Exception Handling Control,  Up: Compiler Switches

4.3.17 Units to Sources Mapping Files
-------------------------------------

`-gnatem=`path''
     A mapping file is a way to communicate to the compiler two
     mappings: from unit names to file names (without any directory
     information) and from file names to path names (with full
     directory information). These mappings are used by the compiler to
     short-circuit the path search.

     The use of mapping files is not required for correct operation of
     the compiler, but mapping files can improve efficiency,
     particularly when sources are read over a slow network connection.
     In normal operation, you need not be concerned with the format or
     use of mapping files, and the `-gnatem' switch is not a switch
     that you would use explicitly. It is intended primarily for use by
     automatic tools such as `gnatmake' running under the project file
     facility. The description here of the format of mapping files is
     provided for completeness and for possible use by other tools.

     A mapping file is a sequence of sets of three lines. In each set,
     the first line is the unit name, in lower case, with `%s' appended
     for specs and `%b' appended for bodies; the second line is the
     file name; and the third line is the path name.

     Example:

         main%b
         main.2.ada
         /gnat/project1/sources/main.2.ada

     When the switch `-gnatem' is specified, the compiler will create
     in memory the two mappings from the specified file. If there is
     any problem (nonexistent file, truncated file or duplicate
     entries), no mapping will be created.

     Several `-gnatem' switches may be specified; however, only the
     last one on the command line will be taken into account.

     When using a project file, `gnatmake' creates a temporary mapping
     file and communicates it to the compiler using this switch.


File: gnat_ugn.info,  Node: Code Generation Control,  Prev: Units to Sources Mapping Files,  Up: Compiler Switches

4.3.18 Code Generation Control
------------------------------

The GCC technology provides a wide range of target dependent `-m'
switches for controlling details of code generation with respect to
different versions of architectures. This includes variations in
instruction sets (e.g., different members of the power pc family), and
different requirements for optimal arrangement of instructions (e.g.,
different members of the x86 family). The list of available `-m'
switches may be found in the GCC documentation.

Use of these `-m' switches may in some cases result in improved code
performance.

The GNAT technology is tested and qualified without any `-m' switches,
so generally the most reliable approach is to avoid the use of these
switches. However, we generally expect most of these switches to work
successfully with GNAT, and many customers have reported successful use
of these options.

Our general advice is to avoid the use of `-m' switches unless special
needs lead to requirements in this area. In particular, there is no
point in using `-m' switches to improve performance unless you actually
see a performance improvement.


File: gnat_ugn.info,  Node: Binding with gnatbind,  Next: Linking with gnatlink,  Prev: Compiler Switches,  Up: Building Executable Programs with GNAT

4.4 Binding with `gnatbind'
===========================

This chapter describes the GNAT binder, `gnatbind', which is used to
bind compiled GNAT objects.

Note: to invoke `gnatbind' with a project file, use the `gnat' driver
(see *note The GNAT Driver and Project Files: 122.).

The `gnatbind' program performs four separate functions:

   * Checks that a program is consistent, in accordance with the rules
     in Chapter 10 of the Ada Reference Manual. In particular, error
     messages are generated if a program uses inconsistent versions of a
     given unit.

   * Checks that an acceptable order of elaboration exists for the
     program and issues an error message if it cannot find an order of
     elaboration that satisfies the rules in Chapter 10 of the Ada
     Language Manual.

   * Generates a main program incorporating the given elaboration order.
     This program is a small Ada package (body and spec) that must be
     subsequently compiled using the GNAT compiler. The necessary
     compilation step is usually performed automatically by `gnatlink'.
     The two most important functions of this program are to call the
     elaboration routines of units in an appropriate order and to call
     the main program.

   * Determines the set of object files required by the given main
     program.  This information is output in the forms of comments in
     the generated program, to be read by the `gnatlink' utility used
     to link the Ada application.

* Menu:

* Running gnatbind::
* Switches for gnatbind::
* Command-Line Access::
* Search Paths for gnatbind::
* Examples of gnatbind Usage::


File: gnat_ugn.info,  Node: Running gnatbind,  Next: Switches for gnatbind,  Up: Binding with gnatbind

4.4.1 Running `gnatbind'
------------------------

The form of the `gnatbind' command is

    $ gnatbind [`switches`] `mainprog`[.ali] [`switches`]

where `mainprog.adb' is the Ada file containing the main program unit
body. `gnatbind' constructs an Ada package in two files whose names are
`b~mainprog.ads', and `b~mainprog.adb'.  For example, if given the
parameter `hello.ali', for a main program contained in file
`hello.adb', the binder output files would be `b~hello.ads' and
`b~hello.adb'.

When doing consistency checking, the binder takes into consideration
any source files it can locate. For example, if the binder determines
that the given main program requires the package `Pack', whose `.ALI'
file is `pack.ali' and whose corresponding source spec file is
`pack.ads', it attempts to locate the source file `pack.ads' (using the
same search path conventions as previously described for the `gcc'
command). If it can locate this source file, it checks that the time
stamps or source checksums of the source and its references to in `ALI'
files match. In other words, any `ALI' files that mentions this spec
must have resulted from compiling this version of the source file (or
in the case where the source checksums match, a version close enough
that the difference does not matter).

The effect of this consistency checking, which includes source files, is
that the binder ensures that the program is consistent with the latest
version of the source files that can be located at bind time. Editing a
source file without compiling files that depend on the source file cause
error messages to be generated by the binder.

For example, suppose you have a main program `hello.adb' and a package
`P', from file `p.ads' and you perform the following steps:

   * Enter `gcc -c hello.adb' to compile the main program.

   * Enter `gcc -c p.ads' to compile package `P'.

   * Edit file `p.ads'.

   * Enter `gnatbind hello'.

At this point, the file `p.ali' contains an out-of-date time stamp
because the file `p.ads' has been edited. The attempt at binding fails,
and the binder generates the following error messages:

    error: "hello.adb" must be recompiled ("p.ads" has been modified)
    error: "p.ads" has been modified and must be recompiled

Now both files must be recompiled as indicated, and then the bind can
succeed, generating a main program. You need not normally be concerned
with the contents of this file, but for reference purposes a sample
binder output file is given in *note Example of Binder Output File: 10.

In most normal usage, the default mode of `gnatbind' which is to
generate the main package in Ada, as described in the previous section.
In particular, this means that any Ada programmer can read and
understand the generated main program. It can also be debugged just
like any other Ada code provided the `-g' switch is used for `gnatbind'
and `gnatlink'.


File: gnat_ugn.info,  Node: Switches for gnatbind,  Next: Command-Line Access,  Prev: Running gnatbind,  Up: Binding with gnatbind

4.4.2 Switches for `gnatbind'
-----------------------------

The following switches are available with `gnatbind'; details will be
presented in subsequent sections.

`--version'
     Display Copyright and version, then exit disregarding all other
     options.

`--help'
     If `-version' was not used, display usage, then exit disregarding
     all other options.

`-a'
     Indicates that, if supported by the platform, the adainit
     procedure should be treated as an initialisation routine by the
     linker (a constructor). This is intended to be used by the Project
     Manager to automatically initialize shared Stand-Alone Libraries.

`-aO'
     Specify directory to be searched for ALI files.

`-aI'
     Specify directory to be searched for source file.

`-A[=`filename']'
     Output ALI list (to standard output or to the named file).

`-b'
     Generate brief messages to `stderr' even if verbose mode set.

`-c'
     Check only, no generation of binder output file.

`-d`nn'[k|m]'
     This switch can be used to change the default task stack size value
     to a specified size `nn', which is expressed in bytes by default,
     or in kilobytes when suffixed with `k' or in megabytes when
     suffixed with `m'.  In the absence of a `[k|m]' suffix, this
     switch is equivalent, in effect, to completing all task specs with

         pragma Storage_Size (nn);

     When they do not already have such a pragma.

`-D`nn'[k|m]'
     This switch can be used to change the default secondary stack size
     value to a specified size `nn', which is expressed in bytes by
     default, or in kilobytes when suffixed with `k' or in megabytes
     when suffixed with `m'.

     The secondary stack is used to deal with functions that return a
     variable sized result, for example a function returning an
     unconstrained String. There are two ways in which this secondary
     stack is allocated.

     For most targets, the secondary stack is growing on demand and is
     allocated as a chain of blocks in the heap. The -D option is not
     very relevant. It only give some control over the size of the
     allocated blocks (whose size is the minimum of the default
     secondary stack size value, and the actual size needed for the
     current allocation request).

     For certain targets, notably VxWorks 653, the secondary stack is
     allocated by carving off a fixed ratio chunk of the primary task
     stack. The -D option is used to define the size of the environment
     task's secondary stack.

`-e'
     Output complete list of elaboration-order dependencies.

`-Ea'
     Store tracebacks in exception occurrences when the target supports
     it.  The "a" is for "address"; tracebacks will contain hexadecimal
     addresses, unless symbolic tracebacks are enabled.

     See also the packages `GNAT.Traceback' and
     `GNAT.Traceback.Symbolic' for more information.  Note that on x86
     ports, you must not use `-fomit-frame-pointer' `gcc' option.

`-Es'
     Store tracebacks in exception occurrences when the target supports
     it.  The "s" is for "symbolic"; symbolic tracebacks are enabled.

`-E'
     Currently the same as `-Ea'.

`-F'
     Force the checks of elaboration flags. `gnatbind' does not normally
     generate checks of elaboration flags for the main executable,
     except when a Stand-Alone Library is used. However, there are
     cases when this cannot be detected by gnatbind. An example is
     importing an interface of a Stand-Alone Library through a pragma
     Import and only specifying through a linker switch this
     Stand-Alone Library. This switch is used to guarantee that
     elaboration flag checks are generated.

`-h'
     Output usage (help) information.

`-H32'
     Use 32-bit allocations for `__gnat_malloc' (and thus for access
     types).  For further details see *note Dynamic Allocation Control:
     127.

`-H64'
     Use 64-bit allocations for `__gnat_malloc' (and thus for access
     types).  For further details see *note Dynamic Allocation Control:
     127.

`-I'
     Specify directory to be searched for source and ALI files.

`-I-'
     Do not look for sources in the current directory where `gnatbind'
     was invoked, and do not look for ALI files in the directory
     containing the ALI file named in the `gnatbind' command line.

`-l'
     Output chosen elaboration order.

`-L`xxx''
     Bind the units for library building. In this case the adainit and
     adafinal procedures (*note Binding with Non-Ada Main Programs: ba.)
     are renamed to `xxx`init and `xxx`final. Implies -n.
     (:ref:`GNAT_and_Libraries', for more details.)

`-M`xyz''
     Rename generated main program from main to xyz. This option is
     supported on cross environments only.

`-m`n''
     Limit number of detected errors or warnings to `n', where `n' is
     in the range 1..999999. The default value if no switch is given is
     9999. If the number of warnings reaches this limit, then a message
     is output and further warnings are suppressed, the bind continues
     in this case. If the number of errors reaches this limit, then a
     message is output and the bind is abandoned.  A value of zero
     means that no limit is enforced. The equal sign is optional.

`-n'
     No main program.

`-nostdinc'
     Do not look for sources in the system default directory.

`-nostdlib'
     Do not look for library files in the system default directory.

`--RTS=`rts-path''
     Specifies the default location of the runtime library. Same
     meaning as the equivalent `gnatmake' flag (*note Switches for
     gnatmake: e2.).

`-o `file''
     Name the output file `file' (default is `b~`xxx'.adb`).  Note that
     if this option is used, then linking must be done manually,
     gnatlink cannot be used.

`-O[=`filename']'
     Output object list (to standard output or to the named file).

`-p'
     Pessimistic (worst-case) elaboration order.

`-P'
     Generate binder file suitable for CodePeer.

`-R'
     Output closure source list, which includes all non-run-time units
     that are included in the bind.

`-Ra'
     Like `-R' but the list includes run-time units.

`-s'
     Require all source files to be present.

`-S`xxx''
     Specifies the value to be used when detecting uninitialized scalar
     objects with pragma Initialize_Scalars.  The `xxx' string
     specified with the switch is one of:

        * `in' for an invalid value.

          If zero is invalid for the discrete type in question, then
          the scalar value is set to all zero bits.  For signed
          discrete types, the largest possible negative value of the
          underlying scalar is set (i.e. a one bit followed by all zero
          bits).  For unsigned discrete types, the underlying scalar
          value is set to all one bits. For floating-point types, a NaN
          value is set (see body of package System.Scalar_Values for
          exact values).

        * `lo' for low value.

          If zero is invalid for the discrete type in question, then
          the scalar value is set to all zero bits.  For signed
          discrete types, the largest possible negative value of the
          underlying scalar is set (i.e. a one bit followed by all zero
          bits).  For unsigned discrete types, the underlying scalar
          value is set to all zero bits. For floating-point, a small
          value is set (see body of package System.Scalar_Values for
          exact values).

        * `hi' for high value.

          If zero is invalid for the discrete type in question, then
          the scalar value is set to all one bits.  For signed discrete
          types, the largest possible positive value of the underlying
          scalar is set (i.e. a zero bit followed by all one bits).
          For unsigned discrete types, the underlying scalar value is
          set to all one bits. For floating-point, a large value is set
          (see body of package System.Scalar_Values for exact values).

        * `xx' for hex value (two hex digits).

          The underlying scalar is set to a value consisting of
          repeated bytes, whose value corresponds to the given value.
          For example if `BF' is given, then a 32-bit scalar value will
          be set to the bit patterm `16#BFBFBFBF#'.

     In addition, you can specify `-Sev' to indicate that the value is
     to be set at run time. In this case, the program will look for an
     environment variable of the form `GNAT_INIT_SCALARS=`yy'', where
     `yy' is one of `in/lo/hi/`xx*` with the same meanings as above.
     If no environment variable is found, or if it does not have a
     valid value, then the default is *in' (invalid values).

`-static'
     Link against a static GNAT run time.

`-shared'
     Link against a shared GNAT run time when available.

`-t'
     Tolerate time stamp and other consistency errors.

`-T`n''
     Set the time slice value to `n' milliseconds. If the system
     supports the specification of a specific time slice value, then
     the indicated value is used. If the system does not support
     specific time slice values, but does support some general notion
     of round-robin scheduling, then any nonzero value will activate
     round-robin scheduling.

     A value of zero is treated specially. It turns off time slicing,
     and in addition, indicates to the tasking run time that the
     semantics should match as closely as possible the Annex D
     requirements of the Ada RM, and in particular sets the default
     scheduling policy to `FIFO_Within_Priorities'.

`-u`n''
     Enable dynamic stack usage, with `n' results stored and displayed
     at program termination. A result is generated when a task
     terminates. Results that can't be stored are displayed on the fly,
     at task termination. This option is currently not supported on
     Itanium platforms. (See *note Dynamic Stack Usage Analysis: 128.
     for details.)

`-v'
     Verbose mode. Write error messages, header, summary output to
     `stdout'.

`-V`key'=`value''
     Store the given association of `key' to `value' in the bind
     environment.  Values stored this way can be retrieved at run time
     using `GNAT.Bind_Environment'.

`-w`x''
     Warning mode; `x' = s/e for suppress/treat as error.

`-Wx`e''
     Override default wide character encoding for standard Text_IO
     files.

`-x'
     Exclude source files (check object consistency only).

`-X`nnn''
     Set default exit status value, normally 0 for POSIX compliance.

`-y'
     Enable leap seconds support in `Ada.Calendar' and its children.

`-z'
     No main subprogram.

You may obtain this listing of switches by running `gnatbind' with no
arguments.

* Menu:

* Consistency-Checking Modes::
* Binder Error Message Control::
* Elaboration Control::
* Output Control::
* Dynamic Allocation Control::
* Binding with Non-Ada Main Programs::
* Binding Programs with No Main Subprogram::


File: gnat_ugn.info,  Node: Consistency-Checking Modes,  Next: Binder Error Message Control,  Up: Switches for gnatbind

4.4.2.1 Consistency-Checking Modes
..................................

As described earlier, by default `gnatbind' checks that object files
are consistent with one another and are consistent with any source
files it can locate. The following switches control binder access to
sources.

 
`-s'
     Require source files to be present. In this mode, the binder must
     be able to locate all source files that are referenced, in order
     to check their consistency. In normal mode, if a source file
     cannot be located it is simply ignored. If you specify this
     switch, a missing source file is an error.

`-Wx`e''
     Override default wide character encoding for standard Text_IO
     files.  Normally the default wide character encoding method used
     for standard [Wide_[Wide_]]Text_IO files is taken from the
     encoding specified for the main source input (see description of
     switch `-gnatWx' for the compiler). The use of this switch for the
     binder (which has the same set of possible arguments) overrides
     this default as specified.

`-x'
     Exclude source files. In this mode, the binder only checks that ALI
     files are consistent with one another. Source files are not
     accessed.  The binder runs faster in this mode, and there is still
     a guarantee that the resulting program is self-consistent.  If a
     source file has been edited since it was last compiled, and you
     specify this switch, the binder will not detect that the object
     file is out of date with respect to the source file. Note that
     this is the mode that is automatically used by `gnatmake' because
     in this case the checking against sources has already been
     performed by `gnatmake' in the course of compilation (i.e., before
     binding).


File: gnat_ugn.info,  Node: Binder Error Message Control,  Next: Elaboration Control,  Prev: Consistency-Checking Modes,  Up: Switches for gnatbind

4.4.2.2 Binder Error Message Control
....................................

The following switches provide control over the generation of error
messages from the binder:

 
`-v'
     Verbose mode. In the normal mode, brief error messages are
     generated to `stderr'. If this switch is present, a header is
     written to `stdout' and any error messages are directed to
     `stdout'.  All that is written to `stderr' is a brief summary
     message.

`-b'
     Generate brief error messages to `stderr' even if verbose mode is
     specified. This is relevant only when used with the `-v' switch.

`-m`n''
     Limits the number of error messages to `n', a decimal integer in
     the range 1-999. The binder terminates immediately if this limit
     is reached.

`-M`xxx''
     Renames the generated main program from `main' to `xxx'.  This is
     useful in the case of some cross-building environments, where the
     actual main program is separate from the one generated by
     `gnatbind'.

`-ws'
     Suppress all warning messages.

`-we'
     Treat any warning messages as fatal errors.

`-t'
     The binder performs a number of consistency checks including:

        * Check that time stamps of a given source unit are consistent

        * Check that checksums of a given source unit are consistent

        * Check that consistent versions of `GNAT' were used for
          compilation

        * Check consistency of configuration pragmas as required

     Normally failure of such checks, in accordance with the consistency
     requirements of the Ada Reference Manual, causes error messages to
     be generated which abort the binder and prevent the output of a
     binder file and subsequent link to obtain an executable.

     The `-t' switch converts these error messages into warnings, so
     that binding and linking can continue to completion even in the
     presence of such errors. The result may be a failed link (due to
     missing symbols), or a non-functional executable which has
     undefined semantics.

          Note: This means that `-t' should be used only in unusual
          situations, with extreme care.


File: gnat_ugn.info,  Node: Elaboration Control,  Next: Output Control,  Prev: Binder Error Message Control,  Up: Switches for gnatbind

4.4.2.3 Elaboration Control
...........................

The following switches provide additional control over the elaboration
order. For full details see *note Elaboration Order Handling in GNAT:
11.

 
`-p'
     Normally the binder attempts to choose an elaboration order that is
     likely to minimize the likelihood of an elaboration order error
     resulting in raising a `Program_Error' exception. This switch
     reverses the action of the binder, and requests that it
     deliberately choose an order that is likely to maximize the
     likelihood of an elaboration error.  This is useful in ensuring
     portability and avoiding dependence on accidental fortuitous
     elaboration ordering.

     Normally it only makes sense to use the `-p' switch if dynamic
     elaboration checking is used (`-gnatE' switch used for
     compilation).  This is because in the default static elaboration
     mode, all necessary `Elaborate' and `Elaborate_All' pragmas are
     implicitly inserted.  These implicit pragmas are still respected
     by the binder in `-p' mode, so a safe elaboration order is assured.

     Note that `-p' is not intended for production use; it is more for
     debugging/experimental use.


File: gnat_ugn.info,  Node: Output Control,  Next: Dynamic Allocation Control,  Prev: Elaboration Control,  Up: Switches for gnatbind

4.4.2.4 Output Control
......................

The following switches allow additional control over the output
generated by the binder.

 
`-c'
     Check only. Do not generate the binder output file. In this mode
     the binder performs all error checks but does not generate an
     output file.

`-e'
     Output complete list of elaboration-order dependencies, showing the
     reason for each dependency. This output can be rather extensive
     but may be useful in diagnosing problems with elaboration order.
     The output is written to `stdout'.

`-h'
     Output usage information. The output is written to `stdout'.

`-K'
     Output linker options to `stdout'. Includes library search paths,
     contents of pragmas Ident and Linker_Options, and libraries added
     by `gnatbind'.

`-l'
     Output chosen elaboration order. The output is written to `stdout'.

`-O'
     Output full names of all the object files that must be linked to
     provide the Ada component of the program. The output is written to
     `stdout'.  This list includes the files explicitly supplied and
     referenced by the user as well as implicitly referenced run-time
     unit files. The latter are omitted if the corresponding units
     reside in shared libraries. The directory names for the run-time
     units depend on the system configuration.

`-o `file''
     Set name of output file to `file' instead of the normal
     `b~`mainprog'.adb` default. Note that `file' denote the Ada binder
     generated body filename.  Note that if this option is used, then
     linking must be done manually.  It is not possible to use gnatlink
     in this case, since it cannot locate the binder file.

`-r'
     Generate list of `pragma Restrictions' that could be applied to
     the current unit. This is useful for code audit purposes, and also
     may be used to improve code generation in some cases.


File: gnat_ugn.info,  Node: Dynamic Allocation Control,  Next: Binding with Non-Ada Main Programs,  Prev: Output Control,  Up: Switches for gnatbind

4.4.2.5 Dynamic Allocation Control
..................................

The heap control switches - `-H32' and `-H64' - determine whether
dynamic allocation uses 32-bit or 64-bit memory.  They only affect
compiler-generated allocations via `__gnat_malloc'; explicit calls to
`malloc' and related functions from the C run-time library are
unaffected.

`-H32'
     Allocate memory on 32-bit heap

`-H64'
     Allocate memory on 64-bit heap.  This is the default unless
     explicitly overridden by a `'Size' clause on the access type.

These switches are only effective on VMS platforms.


File: gnat_ugn.info,  Node: Binding with Non-Ada Main Programs,  Next: Binding Programs with No Main Subprogram,  Prev: Dynamic Allocation Control,  Up: Switches for gnatbind

4.4.2.6 Binding with Non-Ada Main Programs
..........................................

The description so far has assumed that the main program is in Ada, and
that the task of the binder is to generate a corresponding function
`main' that invokes this Ada main program. GNAT also supports the
building of executable programs where the main program is not in Ada,
but some of the called routines are written in Ada and compiled using
GNAT (*note Mixed Language Programming: 46.).  The following switch is
used in this situation:

 
`-n'
     No main program. The main program is not in Ada.

In this case, most of the functions of the binder are still required,
but instead of generating a main program, the binder generates a file
containing the following callable routines:

    `adainit'
          You must call this routine to initialize the Ada part of the
          program by calling the necessary elaboration routines. A call
          to `adainit' is required before the first call to an Ada
          subprogram.

          Note that it is assumed that the basic execution environment
          must be setup to be appropriate for Ada execution at the
          point where the first Ada subprogram is called. In
          particular, if the Ada code will do any floating-point
          operations, then the FPU must be setup in an appropriate
          manner. For the case of the x86, for example, full precision
          mode is required. The procedure GNAT.Float_Control.Reset may
          be used to ensure that the FPU is in the right state.

    `adafinal'
          You must call this routine to perform any library-level
          finalization required by the Ada subprograms. A call to
          `adafinal' is required after the last call to an Ada
          subprogram, and before the program terminates.

If the `-n' switch is given, more than one ALI file may appear on the
command line for `gnatbind'. The normal `closure' calculation is
performed for each of the specified units. Calculating the closure
means finding out the set of units involved by tracing `with'
references. The reason it is necessary to be able to specify more than
one ALI file is that a given program may invoke two or more quite
separate groups of Ada units.

The binder takes the name of its output file from the last specified ALI
file, unless overridden by the use of the `-o file'.

The output is an Ada unit in source form that can be compiled with GNAT.
This compilation occurs automatically as part of the `gnatlink'
processing.

Currently the GNAT run time requires a FPU using 80 bits mode
precision. Under targets where this is not the default it is required to
call GNAT.Float_Control.Reset before using floating point numbers (this
include float computation, float input and output) in the Ada code. A
side effect is that this could be the wrong mode for the foreign code
where floating point computation could be broken after this call.


File: gnat_ugn.info,  Node: Binding Programs with No Main Subprogram,  Prev: Binding with Non-Ada Main Programs,  Up: Switches for gnatbind

4.4.2.7 Binding Programs with No Main Subprogram
................................................

It is possible to have an Ada program which does not have a main
subprogram. This program will call the elaboration routines of all the
packages, then the finalization routines.

The following switch is used to bind programs organized in this manner:

 
`-z'
     Normally the binder checks that the unit name given on the command
     line corresponds to a suitable main subprogram. When this switch
     is used, a list of ALI files can be given, and the execution of
     the program consists of elaboration of these units in an
     appropriate order. Note that the default wide character encoding
     method for standard Text_IO files is always set to Brackets if
     this switch is set (you can use the binder switch `-Wx' to
     override this default).


File: gnat_ugn.info,  Node: Command-Line Access,  Next: Search Paths for gnatbind,  Prev: Switches for gnatbind,  Up: Binding with gnatbind

4.4.3 Command-Line Access
-------------------------

The package `Ada.Command_Line' provides access to the command-line
arguments and program name. In order for this interface to operate
correctly, the two variables

    int gnat_argc;
    char **gnat_argv;

are declared in one of the GNAT library routines. These variables must
be set from the actual `argc' and `argv' values passed to the main
program. With no `n' present, `gnatbind' generates the C main program
to automatically set these variables.  If the `n' switch is used, there
is no automatic way to set these variables. If they are not set, the
procedures in `Ada.Command_Line' will not be available, and any attempt
to use them will raise `Constraint_Error'. If command line access is
required, your main program must set `gnat_argc' and `gnat_argv' from
the `argc' and `argv' values passed to it.


File: gnat_ugn.info,  Node: Search Paths for gnatbind,  Next: Examples of gnatbind Usage,  Prev: Command-Line Access,  Up: Binding with gnatbind

4.4.4 Search Paths for `gnatbind'
---------------------------------

The binder takes the name of an ALI file as its argument and needs to
locate source files as well as other ALI files to verify object
consistency.

For source files, it follows exactly the same search rules as `gcc'
(see *note Search Paths and the Run-Time Library (RTL): 8e.). For ALI
files the directories searched are:

   * The directory containing the ALI file named in the command line,
     unless the switch `-I-' is specified.

   * All directories specified by `-I' switches on the `gnatbind'
     command line, in the order given.

   * Each of the directories listed in the text file whose name is given
     by the `ADA_PRJ_OBJECTS_FILE' environment variable.

     `ADA_PRJ_OBJECTS_FILE' is normally set by gnatmake or by the gnat
     driver when project files are used. It should not normally be set
     by other means.

   * Each of the directories listed in the value of the `ADA_OBJECTS_PATH'
     environment variable.  Construct this value exactly as the `PATH'
     environment variable: a list of directory names separated by
     colons (semicolons when working with the NT version of GNAT).

   * The content of the `ada_object_path' file which is part of the GNAT
     installation tree and is used to store standard libraries such as
     the GNAT Run Time Library (RTL) unless the switch `-nostdlib' is
     specified. See *note Installing a library: 8b.

In the binder the switch `-I' is used to specify both source and
library file paths. Use `-aI' instead if you want to specify source
paths only, and `-aO' if you want to specify library paths only. This
means that for the binder `-I`dir'' is equivalent to `-aI`dir''
`-aO``dir''.  The binder generates the bind file (a C language source
file) in the current working directory.

The packages `Ada', `System', and `Interfaces' and their children make
up the GNAT Run-Time Library, together with the package GNAT and its
children, which contain a set of useful additional library functions
provided by GNAT. The sources for these units are needed by the
compiler and are kept together in one directory. The ALI files and
object files generated by compiling the RTL are needed by the binder
and the linker and are kept together in one directory, typically
different from the directory containing the sources. In a normal
installation, you need not specify these directory names when compiling
or binding. Either the environment variables or the built-in defaults
cause these files to be found.

Besides simplifying access to the RTL, a major use of search paths is
in compiling sources from multiple directories. This can make
development environments much more flexible.


File: gnat_ugn.info,  Node: Examples of gnatbind Usage,  Prev: Search Paths for gnatbind,  Up: Binding with gnatbind

4.4.5 Examples of `gnatbind' Usage
----------------------------------

Here are some examples of `gnatbind' invovations:

         gnatbind hello

     The main program `Hello' (source program in `hello.adb') is bound
     using the standard switch settings. The generated main program is
     `b~hello.adb'. This is the normal, default use of the binder.

         gnatbind hello -o mainprog.adb

     The main program `Hello' (source program in `hello.adb') is bound
     using the standard switch settings. The generated main program is
     `mainprog.adb' with the associated spec in `mainprog.ads'. Note
     that you must specify the body here not the spec. Note that if
     this option is used, then linking must be done manually, since
     gnatlink will not be able to find the generated file.


File: gnat_ugn.info,  Node: Linking with gnatlink,  Next: Using the GNU make Utility,  Prev: Binding with gnatbind,  Up: Building Executable Programs with GNAT

4.5 Linking with `gnatlink'
===========================

This chapter discusses `gnatlink', a tool that links an Ada program and
builds an executable file. This utility invokes the system linker (via
the `gcc' command) with a correct list of object files and library
references.  `gnatlink' automatically determines the list of files and
references for the Ada part of a program. It uses the binder file
generated by the `gnatbind' to determine this list.

Note: to invoke `gnatlink' with a project file, use the `gnat' driver
(see *note The GNAT Driver and Project Files: 122.).

* Menu:

* Running gnatlink::
* Switches for gnatlink::


File: gnat_ugn.info,  Node: Running gnatlink,  Next: Switches for gnatlink,  Up: Linking with gnatlink

4.5.1 Running `gnatlink'
------------------------

The form of the `gnatlink' command is

    $ gnatlink [`switches`] `mainprog`[.ali]
               [`non-Ada objects`] [`linker options`]

The arguments of `gnatlink' (switches, main `ALI' file, non-Ada objects
or linker options) may be in any order, provided that no non-Ada object
may be mistaken for a main `ALI' file.  Any file name `F' without the
`.ali' extension will be taken as the main `ALI' file if a file exists
whose name is the concatenation of `F' and `.ali'.

`mainprog.ali' references the ALI file of the main program.  The `.ali'
extension of this file can be omitted. From this reference, `gnatlink'
locates the corresponding binder file `b~mainprog.adb' and, using the
information in this file along with the list of non-Ada objects and
linker options, constructs a linker command file to create the
executable.

The arguments other than the `gnatlink' switches and the main `ALI'
file are passed to the linker uninterpreted.  They typically include
the names of object files for units written in other languages than Ada
and any library references required to resolve references in any of
these foreign language units, or in `Import' pragmas in any Ada units.

`linker options' is an optional list of linker specific switches.  The
default linker called by gnatlink is `gcc' which in turn calls the
appropriate system linker.

One useful option for the linker is `-s': it reduces the size of the
executable by removing all symbol table and relocation information from
the executable.

Standard options for the linker such as `-lmy_lib' or `-Ldir' can be
added as is.  For options that are not recognized by `gcc' as linker
options, use the `gcc' switches `-Xlinker' or `-Wl,'.

Refer to the GCC documentation for details.

Here is an example showing how to generate a linker map:

    $ gnatlink my_prog -Wl,-Map,MAPFILE

Using `linker options' it is possible to set the program stack and heap
size.  See *note Setting Stack Size from gnatlink: 13d. and *note
Setting Heap Size from gnatlink: 13e.

`gnatlink' determines the list of objects required by the Ada program
and prepends them to the list of objects passed to the linker.
`gnatlink' also gathers any arguments set by the use of `pragma
Linker_Options' and adds them to the list of arguments presented to the
linker.


File: gnat_ugn.info,  Node: Switches for gnatlink,  Prev: Running gnatlink,  Up: Linking with gnatlink

4.5.2 Switches for `gnatlink'
-----------------------------

The following switches are available with the `gnatlink' utility:

`--version'
     Display Copyright and version, then exit disregarding all other
     options.

`--help'
     If `-version' was not used, display usage, then exit disregarding
     all other options.

`-f'
     On some targets, the command line length is limited, and `gnatlink'
     will generate a separate file for the linker if the list of object
     files is too long.  The `-f' switch forces this file to be
     generated even if the limit is not exceeded. This is useful in
     some cases to deal with special situations where the command line
     length is exceeded.

`-g'
     The option to include debugging information causes the Ada bind
     file (in other words, `b~mainprog.adb') to be compiled with `-g'.
     In addition, the binder does not delete the `b~mainprog.adb',
     `b~mainprog.o' and `b~mainprog.ali' files.  Without `-g', the
     binder removes these files by default.

`-n'
     Do not compile the file generated by the binder. This may be used
     when a link is rerun with different options, but there is no need
     to recompile the binder file.

`-v'
     Verbose mode. Causes additional information to be output,
     including a full list of the included object files.  This switch
     option is most useful when you want to see what set of object
     files are being used in the link step.

`-v -v'
     Very verbose mode. Requests that the compiler operate in verbose
     mode when it compiles the binder file, and that the system linker
     run in verbose mode.

`-o `exec-name''
     `exec-name' specifies an alternate name for the generated
     executable program. If this switch is omitted, the executable has
     the same name as the main unit. For example, `gnatlink try.ali'
     creates an executable called `try'.

`-b `target''
     Compile your program to run on `target', which is the name of a
     system configuration. You must have a GNAT cross-compiler built if
     `target' is not the same as your host system.

`-B`dir''
     Load compiler executables (for example, `gnat1', the Ada compiler)
     from `dir' instead of the default location. Only use this switch
     when multiple versions of the GNAT compiler are available.  See
     the `Directory Options' section in `The_GNU_Compiler_Collection'
     for further details. You would normally use the `-b' or `-V'
     switch instead.

`-M'
     When linking an executable, create a map file. The name of the map
     file has the same name as the executable with extension ".map".

`-M=`mapfile''
     When linking an executable, create a map file. The name of the map
     file is `mapfile'.

`--GCC=`compiler_name''
     Program used for compiling the binder file. The default is `gcc'.
     You need to use quotes around `compiler_name' if `compiler_name'
     contains spaces or other separator characters.  As an example
     `--GCC="foo -x -y"' will instruct `gnatlink' to use `foo -x -y' as
     your compiler. Note that switch `-c' is always inserted after your
     command name. Thus in the above example the compiler command that
     will be used by `gnatlink' will be `foo -c -x -y'.  A limitation
     of this syntax is that the name and path name of the executable
     itself must not include any embedded spaces. If the compiler
     executable is different from the default one (gcc or
     <prefix>-gcc), then the back-end switches in the ALI file are not
     used to compile the binder generated source.  For example, this is
     the case with `--GCC="foo -x -y"'. But the back end switches will
     be used for `--GCC="gcc -gnatv"'. If several `--GCC=compiler_name'
     are used, only the last `compiler_name' is taken into account.
     However, all the additional switches are also taken into account.
     Thus, `--GCC="foo -x -y" --GCC="bar -z -t"' is equivalent to
     `--GCC="bar -x -y -z -t"'.

`--LINK=`name''
     `name' is the name of the linker to be invoked. This is especially
     useful in mixed language programs since languages such as C++
     require their own linker to be used. When this switch is omitted,
     the default name for the linker is `gcc'. When this switch is
     used, the specified linker is called instead of `gcc' with exactly
     the same parameters that would have been passed to `gcc' so if the
     desired linker requires different parameters it is necessary to
     use a wrapper script that massages the parameters before invoking
     the real linker. It may be useful to control the exact invocation
     by using the verbose switch.


File: gnat_ugn.info,  Node: Using the GNU make Utility,  Prev: Linking with gnatlink,  Up: Building Executable Programs with GNAT

4.6 Using the GNU `make' Utility
================================

This chapter offers some examples of makefiles that solve specific
problems. It does not explain how to write a makefile, nor does it try
to replace the `gnatmake' utility (*note Building with gnatmake: 1d.).

All the examples in this section are specific to the GNU version of
make. Although `make' is a standard utility, and the basic language is
the same, these examples use some advanced features found only in `GNU
make'.

* Menu:

* Using gnatmake in a Makefile::
* Automatically Creating a List of Directories::
* Generating the Command Line Switches::
* Overcoming Command Line Length Limits::


File: gnat_ugn.info,  Node: Using gnatmake in a Makefile,  Next: Automatically Creating a List of Directories,  Up: Using the GNU make Utility

4.6.1 Using gnatmake in a Makefile
----------------------------------

Complex project organizations can be handled in a very powerful way by
using GNU make combined with gnatmake. For instance, here is a Makefile
which allows you to build each subsystem of a big project into a
separate shared library. Such a makefile allows you to significantly
reduce the link time of very big applications while maintaining full
coherence at each step of the build process.

The list of dependencies are handled automatically by `gnatmake'. The
Makefile is simply used to call gnatmake in each of the appropriate
directories.

Note that you should also read the example on how to automatically
create the list of directories (*note Automatically Creating a List of
Directories: 144.)  which might help you in case your project has a lot
of subdirectories.

    ## This Makefile is intended to be used with the following directory
    ## configuration:
    ##  - The sources are split into a series of csc (computer software components)
    ##    Each of these csc is put in its own directory.
    ##    Their name are referenced by the directory names.
    ##    They will be compiled into shared library (although this would also work
    ##    with static libraries
    ##  - The main program (and possibly other packages that do not belong to any
    ##    csc is put in the top level directory (where the Makefile is).
    ##       toplevel_dir __ first_csc  (sources) __ lib (will contain the library)
    ##                    \\_ second_csc (sources) __ lib (will contain the library)
    ##                    \\_ ...
    ## Although this Makefile is build for shared library, it is easy to modify
    ## to build partial link objects instead (modify the lines with -shared and
    ## gnatlink below)
    ##
    ## With this makefile, you can change any file in the system or add any new
    ## file, and everything will be recompiled correctly (only the relevant shared
    ## objects will be recompiled, and the main program will be re-linked).

    # The list of computer software component for your project. This might be
    # generated automatically.
    CSC_LIST=aa bb cc

    # Name of the main program (no extension)
    MAIN=main

    # If we need to build objects with -fPIC, uncomment the following line
    #NEED_FPIC=-fPIC

    # The following variable should give the directory containing libgnat.so
    # You can get this directory through 'gnatls -v'. This is usually the last
    # directory in the Object_Path.
    GLIB=...

    # The directories for the libraries
    # (This macro expands the list of CSC to the list of shared libraries, you
    # could simply use the expanded form:
    # LIB_DIR=aa/lib/libaa.so bb/lib/libbb.so cc/lib/libcc.so
    LIB_DIR=${foreach dir,${CSC_LIST},${dir}/lib/lib${dir}.so}

    ${MAIN}: objects ${LIB_DIR}
        gnatbind ${MAIN} ${CSC_LIST:%=-aO%/lib} -shared
        gnatlink ${MAIN} ${CSC_LIST:%=-l%}

    objects::
        # recompile the sources
        gnatmake -c -i ${MAIN}.adb ${NEED_FPIC} ${CSC_LIST:%=-I%}

    # Note: In a future version of GNAT, the following commands will be simplified
    # by a new tool, gnatmlib
    ${LIB_DIR}:
        mkdir -p ${dir $@ }
        cd ${dir $@ } && gcc -shared -o ${notdir $@ } ../*.o -L${GLIB} -lgnat
        cd ${dir $@ } && cp -f ../*.ali .

    # The dependencies for the modules
    # Note that we have to force the expansion of *.o, since in some cases
    # make won't be able to do it itself.
    aa/lib/libaa.so: ${wildcard aa/*.o}
    bb/lib/libbb.so: ${wildcard bb/*.o}
    cc/lib/libcc.so: ${wildcard cc/*.o}

    # Make sure all of the shared libraries are in the path before starting the
    # program
    run::
        LD_LIBRARY_PATH=`pwd`/aa/lib:`pwd`/bb/lib:`pwd`/cc/lib ./${MAIN}

    clean::
        ${RM} -rf ${CSC_LIST:%=%/lib}
        ${RM} ${CSC_LIST:%=%/*.ali}
        ${RM} ${CSC_LIST:%=%/*.o}
        ${RM} *.o *.ali ${MAIN}


File: gnat_ugn.info,  Node: Automatically Creating a List of Directories,  Next: Generating the Command Line Switches,  Prev: Using gnatmake in a Makefile,  Up: Using the GNU make Utility

4.6.2 Automatically Creating a List of Directories
--------------------------------------------------

In most makefiles, you will have to specify a list of directories, and
store it in a variable. For small projects, it is often easier to
specify each of them by hand, since you then have full control over what
is the proper order for these directories, which ones should be
included.

However, in larger projects, which might involve hundreds of
subdirectories, it might be more convenient to generate this list
automatically.

The example below presents two methods. The first one, although less
general, gives you more control over the list. It involves wildcard
characters, that are automatically expanded by `make'. Its shortcoming
is that you need to explicitly specify some of the organization of your
project, such as for instance the directory tree depth, whether some
directories are found in a separate tree, etc.

The second method is the most general one. It requires an external
program, called `find', which is standard on all Unix systems. All the
directories found under a given root directory will be added to the
list.

    # The examples below are based on the following directory hierarchy:
    # All the directories can contain any number of files
    # ROOT_DIRECTORY ->  a  ->  aa  ->  aaa
    #                       ->  ab
    #                       ->  ac
    #                ->  b  ->  ba  ->  baa
    #                       ->  bb
    #                       ->  bc
    # This Makefile creates a variable called DIRS, that can be reused any time
    # you need this list (see the other examples in this section)

    # The root of your project's directory hierarchy
    ROOT_DIRECTORY=.

    ####
    # First method: specify explicitly the list of directories
    # This allows you to specify any subset of all the directories you need.
    ####

    DIRS := a/aa/ a/ab/ b/ba/

    ####
    # Second method: use wildcards
    # Note that the argument(s) to wildcard below should end with a '/'.
    # Since wildcards also return file names, we have to filter them out
    # to avoid duplicate directory names.
    # We thus use make's `dir` and `sort` functions.
    # It sets DIRs to the following value (note that the directories aaa and baa
    # are not given, unless you change the arguments to wildcard).
    # DIRS= ./a/a/ ./b/ ./a/aa/ ./a/ab/ ./a/ac/ ./b/ba/ ./b/bb/ ./b/bc/
    ####

    DIRS := ${sort ${dir ${wildcard ${ROOT_DIRECTORY}/*/
                        ${ROOT_DIRECTORY}/*/*/}}}

    ####
    # Third method: use an external program
    # This command is much faster if run on local disks, avoiding NFS slowdowns.
    # This is the most complete command: it sets DIRs to the following value:
    # DIRS= ./a ./a/aa ./a/aa/aaa ./a/ab ./a/ac ./b ./b/ba ./b/ba/baa ./b/bb ./b/bc
    ####

    DIRS := ${shell find ${ROOT_DIRECTORY} -type d -print}


File: gnat_ugn.info,  Node: Generating the Command Line Switches,  Next: Overcoming Command Line Length Limits,  Prev: Automatically Creating a List of Directories,  Up: Using the GNU make Utility

4.6.3 Generating the Command Line Switches
------------------------------------------

Once you have created the list of directories as explained in the
previous section (*note Automatically Creating a List of Directories:
144.), you can easily generate the command line arguments to pass to
gnatmake.

For the sake of completeness, this example assumes that the source path
is not the same as the object path, and that you have two separate lists
of directories.

    # see "Automatically creating a list of directories" to create
    # these variables
    SOURCE_DIRS=
    OBJECT_DIRS=

    GNATMAKE_SWITCHES := ${patsubst %,-aI%,${SOURCE_DIRS}}
    GNATMAKE_SWITCHES += ${patsubst %,-aO%,${OBJECT_DIRS}}

    all:
            gnatmake ${GNATMAKE_SWITCHES} main_unit


File: gnat_ugn.info,  Node: Overcoming Command Line Length Limits,  Prev: Generating the Command Line Switches,  Up: Using the GNU make Utility

4.6.4 Overcoming Command Line Length Limits
-------------------------------------------

One problem that might be encountered on big projects is that many
operating systems limit the length of the command line. It is thus hard
to give gnatmake the list of source and object directories.

This example shows how you can set up environment variables, which will
make `gnatmake' behave exactly as if the directories had been specified
on the command line, but have a much higher length limit (or even none
on most systems).

It assumes that you have created a list of directories in your Makefile,
using one of the methods presented in *note Automatically Creating a
List of Directories: 144.  For the sake of completeness, we assume that
the object path (where the ALI files are found) is different from the
sources patch.

Note a small trick in the Makefile below: for efficiency reasons, we
create two temporary variables (SOURCE_LIST and OBJECT_LIST), that are
expanded immediately by `make'. This way we overcome the standard make
behavior which is to expand the variables only when they are actually
used.

On Windows, if you are using the standard Windows command shell, you
must replace colons with semicolons in the assignments to these
variables.

    # In this example, we create both ADA_INCLUDE_PATH and ADA_OBJECTS_PATH.
    # This is the same thing as putting the -I arguments on the command line.
    # (the equivalent of using -aI on the command line would be to define
    #  only ADA_INCLUDE_PATH, the equivalent of -aO is ADA_OBJECTS_PATH).
    # You can of course have different values for these variables.
    #
    # Note also that we need to keep the previous values of these variables, since
    # they might have been set before running 'make' to specify where the GNAT
    # library is installed.

    # see "Automatically creating a list of directories" to create these
    # variables
    SOURCE_DIRS=
    OBJECT_DIRS=

    empty:=
    space:=${empty} ${empty}
    SOURCE_LIST := ${subst ${space},:,${SOURCE_DIRS}}
    OBJECT_LIST := ${subst ${space},:,${OBJECT_DIRS}}
    ADA_INCLUDE_PATH += ${SOURCE_LIST}
    ADA_OBJECTS_PATH += ${OBJECT_LIST}
    export ADA_INCLUDE_PATH
    export ADA_OBJECTS_PATH

    all:
            gnatmake main_unit


File: gnat_ugn.info,  Node: GNAT Project Manager,  Next: Tools Supporting Project Files,  Prev: Building Executable Programs with GNAT,  Up: Top

5 GNAT Project Manager
**********************

* Menu:

* Introduction::
* Building With Projects::
* Organizing Projects into Subsystems::
* Scenarios in Projects::
* Library Projects::
* Project Extension::
* Aggregate Projects::
* Aggregate Library Projects::
* Project File Reference::


File: gnat_ugn.info,  Node: Introduction,  Next: Building With Projects,  Up: GNAT Project Manager

5.1 Introduction
================

This chapter describes GNAT's `Project Manager', a facility that allows
you to manage complex builds involving a number of source files,
directories, and options for different system configurations. In
particular, project files allow you to specify:

   * The directory or set of directories containing the source files,
     and/or the names of the specific source files themselves

   * The directory in which the compiler's output (`ALI' files, object
     files, tree files, etc.) is to be placed

   * The directory in which the executable programs are to be placed

   * Switch settings for any of the project-enabled tools; you can
     apply these settings either globally or to individual compilation
     units.

   * The source files containing the main subprogram(s) to be built

   * The source programming language(s)

   * Source file naming conventions; you can specify these either
     globally or for individual compilation units (see *note Naming
     Schemes: 14e.).

   * Change any of the above settings depending on external values,
     thus enabling the reuse of the projects in various `scenarios'
     (see *note Scenarios in Projects: 14f.).

   * Automatically build libraries as part of the build process (see
     *note Library Projects: 8a.).

Project files are written in a syntax close to that of Ada, using
familiar notions such as packages, context clauses, declarations,
default values, assignments, and inheritance (see *note Project File
Reference: 150.).

Project files can be built hierarchically from other project files,
simplifying complex system integration and project reuse (see *note
Organizing Projects into Subsystems: 151.).

   * One project can import other projects containing needed source
     files.  More generally, the Project Manager lets you structure
     large development efforts into hierarchical subsystems, where
     build decisions are delegated to the subsystem level, and thus
     different compilation environments (switch settings) used for
     different subsystems.

   * You can organize GNAT projects in a hierarchy: a child project can
     extend a parent project, inheriting the parent's source files and
     optionally overriding any of them with alternative versions (see
     *note Project Extension: 152.).

Several tools support project files, generally in addition to specifying
the information on the command line itself). They share common switches
to control the loading of the project (in particular `-P`projectfile''
and `-X`vbl'=`value'').

The Project Manager supports a wide range of development strategies,
for systems of all sizes.  Here are some typical practices that are
easily handled:

   * Using a common set of source files and generating object files in
     different directories via different switch settings. It can be
     used for instance, for generating separate sets of object files
     for debugging and for production.

   * Using a mostly-shared set of source files with different versions
     of some units or subunits. It can be used for instance, for
     grouping and hiding all OS dependencies in a small number of
     implementation units.

Project files can be used to achieve some of the effects of a source
versioning system (for example, defining separate projects for the
different sets of sources that comprise different releases) but the
Project Manager is independent of any source configuration management
tool that might be used by the developers.

The various sections below introduce the different concepts related to
projects. Each section starts with examples and use cases, and then
goes into the details of related project file capabilities.


File: gnat_ugn.info,  Node: Building With Projects,  Next: Organizing Projects into Subsystems,  Prev: Introduction,  Up: GNAT Project Manager

5.2 Building With Projects
==========================

In its simplest form, a unique project is used to build a single
executable.  This section concentrates on such a simple setup. Later
sections will extend this basic model to more complex setups.

The following concepts are the foundation of project files, and will be
further detailed later in this documentation. They are summarized here
as a reference.

`Project file':
     A text file using an Ada-like syntax, generally using the `.gpr'
     extension. It defines build-related characteristics of an
     application.  The characteristics include the list of sources, the
     location of those sources, the location for the generated object
     files, the name of the main program, and the options for the
     various tools involved in the build process.

`Project attribute':
     A specific project characteristic is defined by an attribute
     clause. Its value is a string or a sequence of strings. All
     settings in a project are defined through a list of predefined
     attributes with precise semantics. See *note Attributes: 155.

`Package in a project':
     Global attributes are defined at the top level of a project.
     Attributes affecting specific tools are grouped in a package whose
     name is related to tool's function. The most common packages are
     `Builder', `Compiler', `Binder', and `Linker'. See *note Packages:
     156.

`Project variables':
     In addition to attributes, a project can use variables to store
     intermediate values and avoid duplication in complex expressions.
     It can be initialized with a value coming from the environment.  A
     frequent use of variables is to define scenarios.  See *note
     External Values: 157, *note Scenarios in Projects: 14f, and *note
     Variables: 158.

`Source files' and `source directories':
     A source file is associated with a language through a naming
     convention. For instance, `foo.c' is typically the name of a C
     source file; `bar.ads' or `bar.1.ada' are two common naming
     conventions for a file containing an Ada spec. A compilation unit
     is often composed of a main source file and potentially several
     auxiliary ones, such as header files in C.  The naming conventions
     can be user defined *note Naming Schemes: 14e, and will drive the
     builder to call the appropriate compiler for the given source file.
     Source files are searched for in the source directories associated
     with the project through the `Source_Dirs' attribute. By default,
     all the files (in these source directories) following the naming
     conventions associated with the declared languages are considered
     to be part of the project. It is also possible to limit the list
     of source files using the `Source_Files' or `Source_List_File'
     attributes. Note that those last two attributes only accept
     basenames with no directory information.

`Object files' and `object directory':
     An object file is an intermediate file produced by the compiler
     from a compilation unit. It is used by post-compilation tools to
     produce final executables or libraries. Object files produced in
     the context of a given project are stored in a single directory
     that can be specified by the `Object_Dir' attribute. In order to
     store objects in two or more object directories, the system must
     be split into distinct subsystems with their own project file.

The following subsections introduce gradually all the attributes of
interest for simple build needs. Here is the simple setup that will be
used in the following examples.

The Ada source files `pack.ads', `pack.adb', and `proc.adb' are in the
`common/' directory. The file `proc.adb' contains an Ada main
subprogram `Proc' that `with's package `Pack'. We want to compile these
source files with the switch `-O2', and put the resulting files in the
directory `obj/'.

    common/
      pack.ads
      pack.adb
      proc.adb
    common/obj/
      proc.ali, proc.o pack.ali, pack.o

Our project is to be called `Build'. The name of the file is the name
of the project (case-insensitive) with the `.gpr' extension, therefore
the project file name is `build.gpr'. This is not mandatory, but a
warning is issued when this convention is not followed.

This is a very simple example, and as stated above, a single project
file is enough for it. We will thus create a new file, that for now
should contain the following code:

    project Build is
    end Build;

* Menu:

* Source Files and Directories::
* Duplicate Sources in Projects::
* Object and Exec Directory::
* Main Subprograms::
* Tools Options in Project Files::
* Compiling with Project Files::
* Executable File Names::
* Avoid Duplication With Variables::
* Naming Schemes::
* Installation::
* Distributed support::


File: gnat_ugn.info,  Node: Source Files and Directories,  Next: Duplicate Sources in Projects,  Up: Building With Projects

5.2.1 Source Files and Directories
----------------------------------

When you create a new project, the first thing to describe is how to
find the corresponding source files. These are the only settings that
are needed by all the tools that will use this project (builder,
compiler, binder and linker for the compilation, IDEs to edit the
source files,...).

The first step is to declare the source directories, which are the
directories to be searched to find source files. In the case of the
example, the `common' directory is the only source directory.

There are several ways of defining source directories:

   * When the attribute `Source_Dirs' is not used, a project contains a
     single source directory which is the one where the project file
     itself resides. In our example, if `build.gpr' is placed in the
     `common' directory, the project has the needed implicit source
     directory.

   * The attribute `Source_Dirs' can be set to a list of path names, one
     for each of the source directories. Such paths can either be
     absolute names (for instance `"/usr/local/common/"' on UNIX), or
     relative to the directory in which the project file resides (for
     instance "." if `build.gpr' is inside `common/', or "common" if it
     is one level up).  Each of the source directories must exist and
     be readable.

     The syntax for directories is platform specific. For portability,
     however, the project manager will always properly translate
     UNIX-like path names to the native format of the specific
     platform. For instance, when the same project file is to be used
     both on Unix and Windows, "/" should be used as the directory
     separator rather than "\".

   * The attribute `Source_Dirs' can automatically include
     subdirectories using a special syntax inspired by some UNIX
     shells. If any of the paths in the list ends with "`**'", then
     that path and all its subdirectories (recursively) are included in
     the list of source directories. For instance, `**' and `./**'
     represent the complete directory tree rooted at the directory in
     which the project file resides.

     When using that construct, it can sometimes be convenient to also
     use the attribute `Excluded_Source_Dirs', which is also a list of
     paths. Each entry specifies a directory whose immediate content,
     not including subdirs, is to be excluded. It is also possible to
     exclude a complete directory subtree using the "**" notation.

     It is often desirable to remove, from the source directories,
     directory subtrees rooted at some subdirectories. An example is
     the subdirectories created by a Version Control System such as
     Subversion that creates directory subtrees rooted at
     subdirectories ".svn". To do that, attribute
     `Ignore_Source_Sub_Dirs' can be used. It specifies the list of
     simple file names for the roots of these undesirable directory
     subtrees.

         for Source_Dirs use ("./**");
         for Ignore_Source_Sub_Dirs use (".svn");

When applied to the simple example, and because we generally prefer to
have the project file at the toplevel directory rather than mixed with
the sources, we will create the following file

    build.gpr
    project Build is
       for Source_Dirs use ("common");  --  <<<<
    end Build;

Once source directories have been specified, one may need to indicate
source files of interest. By default, all source files present in the
source directories are considered by the project manager. When this is
not desired, it is possible to specify the list of sources to consider
explicitly.  In such a case, only source file base names are indicated
and not their absolute or relative path names. The project manager is
in charge of locating the specified source files in the specified
source directories.

   * By default, the project manager searches for all source files of
     all specified languages in all the source directories.

     Since the project manager was initially developed for Ada
     environments, the default language is usually Ada and the above
     project file is complete: it defines without ambiguity the sources
     composing the project: that is to say, all the sources in
     subdirectory "common" for the default language (Ada) using the
     default naming convention.

     However, when compiling a multi-language application, or a pure C
     application, the project manager must be told which languages are
     of interest, which is done by setting the `Languages' attribute to
     a list of strings, each of which is the name of a language.

     Even when using only Ada, the default naming might not be
     suitable. Indeed, how does the project manager recognizes an "Ada
     file" from any other file? Project files can describe the naming
     scheme used for source files, and override the default (see *note
     Naming Schemes: 14e.). The default is the standard GNAT extension
     (`.adb' for bodies and `.ads' for specs), which is what is used in
     our example, explaining why no naming scheme is explicitly
     specified.  See *note Naming Schemes: 14e.

   * `Source_Files'.  In some cases, source directories might contain
     files that should not be included in a project. One can specify
     the explicit list of file names to be considered through the
     `Source_Files' attribute.  When this attribute is defined, instead
     of looking at every file in the source directories, the project
     manager takes only those names into consideration  reports  errors
     if they cannot be found in the source directories or does not
     correspond to the naming scheme.

   * For various reasons, it is sometimes useful to have a project with
     no sources (most of the time because the attributes defined in the
     project file will be reused in other projects, as explained in
     *note Organizing Projects into Subsystems: 151. To do this, the
     attribute `Source_Files' is set to the empty list, i.e. `()'.
     Alternatively, `Source_Dirs' can be set to the empty list, with
     the same result.

   * `Source_List_File'.  If there is a great number of files, it might
     be more convenient to use the attribute `Source_List_File', which
     specifies the full path of a file.  This file must contain a list
     of source file names (one per line, no directory information) that
     are searched as if they had been defined through `Source_Files'.
     Such a file can easily be created through external tools.

     A warning is issued if both attributes `Source_Files' and
     `Source_List_File' are given explicit values. In this case, the
     attribute `Source_Files' prevails.

   * `Excluded_Source_Files'.  Specifying an explicit list of files is
     not always convenient.It might be more convenient to use the
     default search rules with specific exceptions.  This can be done
     thanks to the attribute `Excluded_Source_Files' (or its synonym
     `Locally_Removed_Files').  Its value is the list of file names
     that should not be taken into account.  This attribute is often
     used when extending a project, see *note Project Extension: 152. A
     similar attribute `Excluded_Source_List_File' plays the same role
     but takes the name of file containing file names similarly to
     `Source_List_File'.

In most simple cases, such as the above example, the default source
file search behavior provides the expected result, and we do not need
to add anything after setting `Source_Dirs'. The project manager
automatically finds `pack.ads', `pack.adb', and `proc.adb' as source
files of the project.

Note that by default a warning is issued when a project has no sources
attached to it and this is not explicitly indicated in the project file.


File: gnat_ugn.info,  Node: Duplicate Sources in Projects,  Next: Object and Exec Directory,  Prev: Source Files and Directories,  Up: Building With Projects

5.2.2 Duplicate Sources in Projects
-----------------------------------

If the order of the source directories is known statically, that is if
`"/**"' is not used in the string list `Source_Dirs', then there may be
several files with the same name sitting in different directories of the
project. In this case, only the file in the first directory is
considered as a source of the project and the others are hidden. If
`"/**"' is used in the string list `Source_Dirs', it is an error to
have several files with the same name in the same directory `"/**"'
subtree, since there would be an ambiguity as to which one should be
used. However, two files with the same name may exist in two single
directories or directory subtrees. In this case, the one in the first
directory or directory subtree is a source of the project.

If there are two sources in different directories of the same `"/**"'
subtree, one way to resolve the problem is to exclude the directory of
the file that should not be used as a source of the project.


File: gnat_ugn.info,  Node: Object and Exec Directory,  Next: Main Subprograms,  Prev: Duplicate Sources in Projects,  Up: Building With Projects

5.2.3 Object and Exec Directory
-------------------------------

The next step when writing a project is to indicate where the compiler
should put the object files. In fact, the compiler and other tools
might create several different kind of files (for GNAT, there is the
object file and the ALI file for instance). One of the important
concepts in projects is that most tools may consider source directories
as read-only and do not attempt to create new or temporary files there.
Instead, all files are created in the object directory. It is of course
not true for project-aware IDEs, whose purpose it is to create the
source files.

The object directory is specified through the `Object_Dir' attribute.
Its value is the path to the object directory, either absolute or
relative to the directory containing the project file. This directory
must already exist and be readable and writable, although some tools
have a switch to create the directory if needed (See the switch `-p'
for `gprbuild').

If the attribute `Object_Dir' is not specified, it defaults to the
project directory, that is the directory containing the project file.

For our example, we can specify the object dir in this way:

    project Build is
       for Source_Dirs use ("common");
       for Object_Dir use "obj";   --  <<<<
    end Build;

As mentioned earlier, there is a single object directory per project.
As a result, if you have an existing system where the object files are
spread across several directories, you can either move all of them into
the same directory if you want to build it with a single project file,
or study the section on subsystems (see *note Organizing Projects into
Subsystems: 151.) to see how each separate object directory can be
associated with one of the subsystems constituting the application.

When the `linker' is called, it usually creates an executable. By
default, this executable is placed in the object directory of the
project. It might be convenient to store it in its own directory.

This can be done through the `Exec_Dir' attribute, which, like
`Object_Dir' contains a single absolute or relative path and must point
to an existing and writable directory, unless you ask the tool to
create it on your behalf. When not specified, It defaults to the object
directory and therefore to the project file's directory if neither
`Object_Dir' nor `Exec_Dir' was specified.

In the case of the example, let's place the executable in the root of
the hierarchy, ie the same directory as `build.gpr'. Hence the project
file is now

    project Build is
       for Source_Dirs use ("common");
       for Object_Dir use "obj";
       for Exec_Dir use ".";  --   <<<<
    end Build;


File: gnat_ugn.info,  Node: Main Subprograms,  Next: Tools Options in Project Files,  Prev: Object and Exec Directory,  Up: Building With Projects

5.2.4 Main Subprograms
----------------------

In the previous section, executables were mentioned. The project
manager needs to be taught what they are. In a project file, an
executable is indicated by pointing to the source file of a main
subprogram. In C this is the file that contains the `main' function,
and in Ada the file that contains the main unit.

There can be any number of such main files within a given project, and
thus several executables can be built in the context of a single
project file. Of course, one given executable might not (and in fact
will not) need all the source files referenced by the project. As
opposed to other build environments such as `makefile', one does not
need to specify the list of dependencies of each executable, the
project-aware builder knows enough of the semantics of the languages to
build and link only the necessary elements.

The list of main files is specified via the `Main' attribute. It
contains a list of file names (no directories). If a project defines
this attribute, it is not necessary to identify  main files on the
command line when invoking a builder, and editors like `GPS' will be
able to create extra menus to spawn or debug the corresponding
executables.

    project Build is
       for Source_Dirs use ("common");
       for Object_Dir use "obj";
       for Exec_Dir use ".";
       for Main use ("proc.adb");  --   <<<<
    end Build;

If this attribute is defined in the project, then spawning the builder
with a command such as

    gprbuild -Pbuild

automatically builds all the executables corresponding to the files
listed in the `Main' attribute. It is possible to specify one or more
executables on the command line to build a subset of them.


File: gnat_ugn.info,  Node: Tools Options in Project Files,  Next: Compiling with Project Files,  Prev: Main Subprograms,  Up: Building With Projects

5.2.5 Tools Options in Project Files
------------------------------------

We now have a project file that fully describes our environment, and
can be used to build the application with a simple `gprbuild' command
as seen in the previous section. In fact, the empty project we showed
immediately at the beginning (with no attribute at all) could already
fulfill that need if it was put in the `common' directory.

Of course, we might want more control. This section shows you how to
specify the compilation switches that the various tools involved in the
building of the executable should use.

Since source names and locations are described in the project file, it
is not necessary to use switches on the command line for this purpose
(switches such as -I for gcc). This removes a major source of command
line length overflow.  Clearly, the builders will have to communicate
this information one way or another to the underlying compilers and
tools they call but they usually use response files for this and thus
are not subject to command line overflows.

Several tools participate to the creation of an executable: the compiler
produces object files from the source files; the binder (in the Ada
case) creates a "source" file that takes care, among other things, of
elaboration issues and global variable initialization; and the linker
gathers everything into a single executable that users can execute. All
these tools are known to the project manager and will be called with
user defined switches from the project files. However, we need to
introduce a new project file concept to express the switches to be used
for any of the tools involved in the build.

A project file is subdivided into zero or more `packages', each of which
contains the attributes specific to one tool (or one set of tools).
Project files use an Ada-like syntax for packages. Package names
permitted in project files are restricted to a predefined set (see
*note Packages: 156.), and the contents of packages are limited to a
small set of constructs and attributes (see *note Attributes: 155.).

Our example project file can be extended with the following empty
packages. At this stage, they could all be omitted since they are
empty, but they show which packages would be involved in the build
process.

    project Build is
       for Source_Dirs use ("common");
       for Object_Dir use "obj";
       for Exec_Dir use ".";
       for Main use ("proc.adb");

       package Builder is  --<<<  for gprbuild
       end Builder;

       package Compiler is --<<<  for the compiler
       end Compiler;

       package Binder is   --<<<  for the binder
       end Binder;

       package Linker is   --<<<  for the linker
       end Linker;
    end Build;

Let's first examine the compiler switches. As stated in the initial
description of the example, we want to compile all files with `-O2'.
This is a compiler switch, although it is usual, on the command line,
to pass it to the builder which then passes it to the compiler. It is
recommended to use directly the right package, which will make the
setup easier to understand for other people.

Several attributes can be used to specify the switches:

`Default_Switches':

     This is the first mention in this manual of an `indexed
     attribute'. When this attribute is defined, one must supply an
     `index' in the form of a literal string.  In the case of
     `Default_Switches', the index is the name of the language to which
     the switches apply (since a different compiler will likely be used
     for each language, and each compiler has its own set of switches).
     The value of the attribute is a list of switches.

     In this example, we want to compile all Ada source files with the
     switch `-O2', and the resulting project file is as follows (only
     the `Compiler' package is shown):

         package Compiler is
           for Default_Switches ("Ada") use ("-O2");
         end Compiler;

`Switches':

     In some cases, we might want to use specific switches for one or
     more files. For instance, compiling `proc.adb' might not be
     possible at high level of optimization because of a compiler issue.
     In such a case, the `Switches' attribute (indexed on the file
     name) can be used and will override the switches defined by
     `Default_Switches'. Our project file would become:

         package Compiler is
            for Default_Switches ("Ada")
                use ("-O2");
            for Switches ("proc.adb")
                use ("-O0");
         end Compiler;

     `Switches' may take a pattern as an index, such as in:

         package Compiler is
           for Default_Switches ("Ada")
               use ("-O2");
           for Switches ("pkg*")
               use ("-O0");
         end Compiler;

     Sources `pkg.adb' and `pkg-child.adb' would be compiled with -O0,
     not -O2.

     `Switches' can also be given a language name as index instead of a
     file name in which case it has the same semantics as
     `Default_Switches'.  However, indexes with wild cards are never
     valid for language name.

`Local_Configuration_Pragmas':

     This attribute may specify the path of a file containing
     configuration pragmas for use by the Ada compiler, such as `pragma
     Restrictions (No_Tasking)'. These pragmas will be used for all the
     sources of the project.

The switches for the other tools are defined in a similar manner
through the `Default_Switches' and `Switches' attributes, respectively
in the `Builder' package (for `gprbuild'), the `Binder' package
(binding Ada executables) and the `Linker' package (for linking
executables).


File: gnat_ugn.info,  Node: Compiling with Project Files,  Next: Executable File Names,  Prev: Tools Options in Project Files,  Up: Building With Projects

5.2.6 Compiling with Project Files
----------------------------------

Now that our project files are written, let's build our executable.
Here is the command we would use from the command line:

    gprbuild -Pbuild

This will automatically build the executables specified through the
`Main' attribute: for each, it will compile or recompile the sources
for which the object file does not exist or is not up-to-date; it will
then run the binder; and finally run the linker to create the
executable itself.

The `gprbuild' builder, can automatically manage C files the same way:
create the file `utils.c' in the `common' directory, set the attribute
`Languages' to `"(Ada, C)"', and re-run

    gprbuild -Pbuild

Gprbuild knows how to recompile the C files and will recompile them
only if one of their dependencies has changed. No direct indication on
how to build the various elements is given in the project file, which
describes the project properties rather than a set of actions to be
executed. Here is the invocation of `gprbuild' when building a
multi-language program:

    $ gprbuild -Pbuild
    gcc -c proc.adb
    gcc -c pack.adb
    gcc -c utils.c
    gprbind proc
    ...
    gcc proc.o -o proc

Notice the three steps described earlier:

   * The first three gcc commands correspond to the compilation phase.

   * The gprbind command corresponds to the post-compilation phase.

   * The last gcc command corresponds to the final link.

The default output of GPRbuild's execution is kept reasonably simple
and easy to understand. In particular, some of the less frequently used
commands are not shown, and some parameters are abbreviated. So it is
not possible to rerun the effect of the `gprbuild' command by
cut-and-pasting its output.  GPRbuild's option `-v' provides a much
more verbose output which includes, among other information, more
complete compilation, post-compilation and link commands.


File: gnat_ugn.info,  Node: Executable File Names,  Next: Avoid Duplication With Variables,  Prev: Compiling with Project Files,  Up: Building With Projects

5.2.7 Executable File Names
---------------------------

By default, the executable name corresponding to a main file is
computed from the main source file name. Through the attribute
`Builder.Executable', it is possible to change this default.

For instance, instead of building `proc' (or `proc.exe' on Windows), we
could configure our project file to build "proc1" (resp proc1.exe) with
the following addition:

    project Build is
       ...  --  same as before
       package Builder is
          for Executable ("proc.adb") use "proc1";
       end Builder
    end Build;

Attribute `Executable_Suffix', when specified, may change the suffix of
the executable files, when no attribute `Executable' applies: its value
replaces the platform-specific executable suffix.  The default
executable suffix is empty on UNIX and ".exe" on Windows.

It is also possible to change the name of the produced executable by
using the command line switch `-o'. When several mains are defined in
the project, it is not possible to use the `-o' switch and the only way
to change the names of the executable is provided by Attributes
`Executable' and `Executable_Suffix'.


File: gnat_ugn.info,  Node: Avoid Duplication With Variables,  Next: Naming Schemes,  Prev: Executable File Names,  Up: Building With Projects

5.2.8 Avoid Duplication With Variables
--------------------------------------

To illustrate some other project capabilities, here is a slightly more
complex project using similar sources and a main program in C:

    project C_Main is
       for Languages    use ("Ada", "C");
       for Source_Dirs  use ("common");
       for Object_Dir   use  "obj";
       for Main         use ("main.c");
       package Compiler is
          C_Switches := ("-pedantic");
          for Default_Switches ("C")   use C_Switches;
          for Default_Switches ("Ada") use ("-gnaty");
          for Switches ("main.c") use C_Switches & ("-g");
       end Compiler;
    end C_Main;

This project has many similarities with the previous one.  As expected,
its `Main' attribute now refers to a C source.  The attribute
`Exec_Dir' is now omitted, thus the resulting executable will be put in
the directory `obj'.

The most noticeable difference is the use of a variable in the
`Compiler' package to store settings used in several attributes.  This
avoids text duplication, and eases maintenance (a single place to
modify if we want to add new switches for C files). We will revisit the
use of variables in the context of scenarios (see *note Scenarios in
Projects: 14f.).

In this example, we see how the file `main.c' can be compiled with the
switches used for all the other C files, plus `-g'.  In this specific
situation the use of a variable could have been replaced by a reference
to the `Default_Switches' attribute:

    for Switches ("c_main.c") use Compiler'Default_Switches ("C") & ("-g");

Note the tick (`'') used to refer to attributes defined in a package.

Here is the output of the GPRbuild command using this project:

    $ gprbuild -Pc_main
    gcc -c -pedantic -g main.c
    gcc -c -gnaty proc.adb
    gcc -c -gnaty pack.adb
    gcc -c -pedantic utils.c
    gprbind main.bexch
    ...
    gcc main.o -o main

The default switches for Ada sources, the default switches for C
sources (in the compilation of `lib.c'), and the specific switches for
`main.c' have all been taken into account.


File: gnat_ugn.info,  Node: Naming Schemes,  Next: Installation,  Prev: Avoid Duplication With Variables,  Up: Building With Projects

5.2.9 Naming Schemes
--------------------

Sometimes an Ada software system is ported from one compilation
environment to another (say GNAT), and the file are not named using the
default GNAT conventions. Instead of changing all the file names, which
for a variety of reasons might not be possible, you can define the
relevant file naming scheme in the `Naming' package of your project
file.

The naming scheme has two distinct goals for the project manager: it
allows finding of source files when searching in the source
directories, and given a source file name it makes it possible to guess
the associated language, and thus the compiler to use.

Note that the use by the Ada compiler of pragmas Source_File_Name is not
supported when using project files. You must use the features described
in this paragraph. You can however specify other configuration pragmas.

The following attributes can be defined in package `Naming':

`Casing':

     Its value must be one of `"lowercase"' (the default if
     unspecified), `"uppercase"' or `"mixedcase"'. It describes the
     casing of file names with regards to the Ada unit name. Given an
     Ada unit My_Unit, the file name will respectively be `my_unit.adb'
     (lowercase), `MY_UNIT.ADB' (uppercase) or `My_Unit.adb'
     (mixedcase).  On Windows, file names are case insensitive, so this
     attribute is irrelevant.

`Dot_Replacement':

     This attribute specifies the string that should replace the "." in
     unit names. Its default value is `"-"' so that a unit
     `Parent.Child' is expected to be found in the file
     `parent-child.adb'. The replacement string must satisfy the
     following requirements to avoid ambiguities in the naming scheme:

        * It must not be empty

        * It cannot start or end with an alphanumeric character

        * It cannot be a single underscore

        * It cannot start with an underscore followed by an alphanumeric

        * It cannot contain a dot `'.'' except if the entire string is
          `"."'

`Spec_Suffix' and `Specification_Suffix':

     For Ada, these attributes give the suffix used in file names that
     contain specifications. For other languages, they give the
     extension for files that contain declaration (header files in C
     for instance). The attribute is indexed on the language.  The two
     attributes are equivalent, but the latter is obsolescent.

     If the value of the attribute is the empty string, it indicates to
     the Project Manager that the only specifications/header files for
     the language are those specified with attributes `Spec' or
     `Specification_Exceptions'.

     If `Spec_Suffix ("Ada")' is not specified, then the default is
     `".ads"'.

     A non empty value must satisfy the following requirements:

        * It must include at least one dot

        * If `Dot_Replacement' is a single dot, then it cannot include
          more than one dot.

`Body_Suffix' and `Implementation_Suffix':

     These attributes give the extension used for file names that
     contain code (bodies in Ada). They are indexed on the language.
     The second version is obsolescent and fully replaced by the first
     attribute.

     For each language of a project, one of these two attributes need
     to be specified, either in the project itself or in the
     configuration project file.

     If the value of the attribute is the empty string, it indicates to
     the Project Manager that the only source files for the language
     are those specified with attributes `Body' or
     `Implementation_Exceptions'.

     These attributes must satisfy the same requirements as
     `Spec_Suffix'.  In addition, they must be different from any of
     the values in `Spec_Suffix'.  If `Body_Suffix ("Ada")' is not
     specified, then the default is `".adb"'.

     If `Body_Suffix ("Ada")' and `Spec_Suffix ("Ada")' end with the
     same string, then a file name that ends with the longest of these
     two suffixes will be a body if the longest suffix is `Body_Suffix
     ("Ada")' or a spec if the longest suffix is `Spec_Suffix ("Ada")'.

     If the suffix does not start with a '.', a file with a name
     exactly equal to the suffix will also be part of the project (for
     instance if you define the suffix as `Makefile.in', a file called
     `Makefile.in' will be part of the project. This capability is
     usually not interesting when building.  However, it might become
     useful when a project is also used to find the list of source
     files in an editor, like the GNAT Programming System (GPS).

`Separate_Suffix':

     This attribute is specific to Ada. It denotes the suffix used in
     file names that contain separate bodies. If it is not specified,
     then it defaults to same value as `Body_Suffix ("Ada")'.

     The value of this attribute cannot be the empty string.

     Otherwise, the same rules apply as for the `Body_Suffix'
     attribute. The only accepted index is "Ada".

`Spec' or `Specification':

     This attribute `Spec' can be used to define the source file name
     for a given Ada compilation unit's spec. The index is the literal
     name of the Ada unit (case insensitive). The value is the literal
     base name of the file that contains this unit's spec (case
     sensitive or insensitive depending on the operating system). This
     attribute allows the definition of exceptions to the general
     naming scheme, in case some files do not follow the usual
     convention.

     When a source file contains several units, the relative position
     of the unit can be indicated. The first unit in the file is at
     position 1

         for Spec ("MyPack.MyChild") use "mypack.mychild.spec";
         for Spec ("top") use "foo.a" at 1;
         for Spec ("foo") use "foo.a" at 2;

`Body' or `Implementation':

     These attribute play the same role as `Spec' for Ada bodies.

`Specification_Exceptions' and `Implementation_Exceptions':

     These attributes define exceptions to the naming scheme for
     languages other than Ada. They are indexed on the language name,
     and contain a list of file names respectively for headers and
     source code.

For example, the following package models the Apex file naming rules:

    package Naming is
      for Casing               use "lowercase";
      for Dot_Replacement      use ".";
      for Spec_Suffix ("Ada")  use ".1.ada";
      for Body_Suffix ("Ada")  use ".2.ada";
    end Naming;


File: gnat_ugn.info,  Node: Installation,  Next: Distributed support,  Prev: Naming Schemes,  Up: Building With Projects

5.2.10 Installation
-------------------

After building an application or a library it is often required to
install it into the development environment. For instance this step is
required if the library is to be used by another application.  The
`gprinstall' tool provides an easy way to install libraries, executable
or object code generated during the build. The `Install' package can be
used to change the default locations.

The following attributes can be defined in package `Install':

`Active'
     Whether the project is to be installed, values are `true'
     (default) or `false'.

`Artifacts'

     An array attribute to declare a set of files not part of the
     sources to be installed. The array discriminant is the directory
     where the file is to be installed. If a relative directory then
     Prefix (see below) is prepended. Note also that if the same file
     name occurs multiple time in the attribute list, the last one will
     be the one installed.

`Prefix':

     Root directory for the installation.

`Exec_Subdir'

     Subdirectory of `Prefix' where executables are to be installed.
     Default is `bin'.

`Lib_Subdir'

     Subdirectory of `Prefix' where directory with the library or object
     files is to be installed. Default is `lib'.

`Sources_Subdir'

     Subdirectory of `Prefix' where directory with sources is to be
     installed. Default is `include'.

`Project_Subdir'

     Subdirectory of `Prefix' where the generated project file is to be
     installed. Default is `share/gpr'.

`Mode'

     The installation mode, it is either `dev' (default) or `usage'.
     See `gprbuild' user's guide for details.

`Install_Name'

     Specify the name to use for recording the installation. The
     default is the project name without the extension.


File: gnat_ugn.info,  Node: Distributed support,  Prev: Installation,  Up: Building With Projects

5.2.11 Distributed support
--------------------------

For large projects the compilation time can become a limitation in the
development cycle. To cope with that, GPRbuild supports distributed
compilation.

The following attributes can be defined in package `Remote':

`Root_Dir':

     Root directory of the project's sources. The default value is the
     project's directory.


File: gnat_ugn.info,  Node: Organizing Projects into Subsystems,  Next: Scenarios in Projects,  Prev: Building With Projects,  Up: GNAT Project Manager

5.3 Organizing Projects into Subsystems
=======================================

A `subsystem' is a coherent part of the complete system to be built. It
is represented by a set of sources and one single object directory. A
system can be composed of a single subsystem when it is simple as we
have seen in the first section. Complex systems are usually composed of
several interdependent subsystems. A subsystem is dependent on another
subsystem if knowledge of the other one is required to build it, and in
particular if visibility on some of the sources of this other subsystem
is required. Each subsystem is usually represented by its own project
file.

In this section, the previous example is being extended. Let's assume
some sources of our `Build' project depend on other sources.  For
instance, when building a graphical interface, it is usual to depend
upon a graphical library toolkit such as GtkAda. Furthermore, we also
need sources from a logging module we had previously written.

* Menu:

* Project Dependencies::
* Cyclic Project Dependencies::
* Sharing Between Projects::
* Global Attributes::


File: gnat_ugn.info,  Node: Project Dependencies,  Next: Cyclic Project Dependencies,  Up: Organizing Projects into Subsystems

5.3.1 Project Dependencies
--------------------------

GtkAda comes with its own project file (appropriately called
`gtkada.gpr'), and we will assume we have already built a project
called `logging.gpr' for the logging module. With the information
provided so far in `build.gpr', building the application would fail
with an error indicating that the gtkada and logging units that are
relied upon by the sources of this project cannot be found.

This is solved by adding the following `with' clauses at the beginning
of our project:

    with "gtkada.gpr";
    with "a/b/logging.gpr";
    project Build is
      ...  --  as before
    end Build;

When such a project is compiled, `gprbuild' will automatically check
the other projects and recompile their sources when needed. It will also
recompile the sources from `Build' when needed, and finally create the
executable. In some cases, the implementation units needed to recompile
a project are not available, or come from some third party and you do
not want to recompile it yourself. In this case, set the attribute
`Externally_Built' to "true", indicating to the builder that this
project can be assumed to be up-to-date, and should not be considered
for recompilation. In Ada, if the sources of this externally built
project were compiled with another version of the compiler or with
incompatible options, the binder will issue an error.

The project's `with' clause has several effects. It provides source
visibility between projects during the compilation process. It also
guarantees that the necessary object files from `Logging' and `GtkAda'
are available when linking `Build'.

As can be seen in this example, the syntax for importing projects is
similar to the syntax for importing compilation units in Ada. However,
project files use literal strings instead of names, and the `with'
clause identifies project files rather than packages.

Each literal string after `with' is the path (absolute or relative) to
a project file. The `.gpr' extension is optional, although we recommend
adding it. If no extension is specified, and no project file with the
`.gpr' extension is found, then the file is searched for exactly as
written in the `with' clause, that is with no extension.

As mentioned above, the path after a `with' has to be a literal string,
and you cannot use concatenation, or lookup the value of external
variables to change the directories from which a project is loaded.  A
solution if you need something like this is to use aggregate projects
(see *note Aggregate Projects: 171.).

When a relative path or a base name is used, the project files are
searched relative to each of the directories in the `project path'.
This path includes all the directories found with the following
algorithm, in this order; the first matching file is used:

   * First, the file is searched relative to the directory that
     contains the current project file.

   * Then it is searched relative to all the directories specified in
     the environment variables `GPR_PROJECT_PATH_FILE',
     `GPR_PROJECT_PATH' and `ADA_PROJECT_PATH' (in that order) if they
     exist.  The value of `GPR_PROJECT_PATH_FILE', when defined, is the
     path name of a text file that contains project directory path
     names, one per line.  `GPR_PROJECT_PATH' and `ADA_PROJECT_PATH',
     when defined, contain project directory path names separated by
     directory separators.  `ADA_PROJECT_PATH' is used for
     compatibility, it is recommended to use `GPR_PROJECT_PATH_FILE' or
     `GPR_PROJECT_PATH'.

   * Finally, it is searched relative to the default project
     directories.  Such directories depend on the tool used. The
     locations searched in the specified order are:

        * `<prefix>/<target>/lib/gnat' if option `-target' is specified

        * `<prefix>/<target>/share/gpr' if option `-target' is specified

        * `<prefix>/share/gpr/'

        * `<prefix>/lib/gnat/'

     In our example, `gtkada.gpr' is found in the predefined directory
     if it was installed at the same root as GNAT.

Some tools also support extending the project path from the command
line, generally through the `-aP'. You can see the value of the project
path by using the `gnatls -v' command.

Any symbolic link will be fully resolved in the directory of the
importing project file before the imported project file is examined.

Any source file in the imported project can be used by the sources of
the importing project, transitively.  Thus if `A' imports `B', which
imports `C', the sources of `A' may depend on the sources of `C', even
if `A' does not import `C' explicitly. However, this is not
recommended, because if and when `B' ceases to import `C', some sources
in `A' will no longer compile. `gprbuild' has a switch
`-no-indirect-imports' that will report such indirect dependencies.

     Note: One very important aspect of a project hierarchy is that `a
     given source can only belong to one project' (otherwise the
     project manager would not know which settings apply to it and when
     to recompile it). It means that different project files do not
     usually share source directories or when they do, they need to
     specify precisely which project owns which sources using attribute
     `Source_Files' or equivalent. By contrast, 2 projects can each own
     a source with the same base file name as long as they live in
     different directories. The latter is not true for Ada Sources
     because of the correlation between source files and Ada units.


File: gnat_ugn.info,  Node: Cyclic Project Dependencies,  Next: Sharing Between Projects,  Prev: Project Dependencies,  Up: Organizing Projects into Subsystems

5.3.2 Cyclic Project Dependencies
---------------------------------

Cyclic dependencies are mostly forbidden: if `A' imports `B' (directly
or indirectly) then `B' is not allowed to import `A'. However, there
are cases when cyclic dependencies would be beneficial. For these
cases, another form of import between projects exists: the `limited
with'.  A project `A' that imports a project `B' with a straight `with'
may also be imported, directly or indirectly, by `B' through a `limited
with'.

The difference between straight `with' and `limited with' is that the
name of a project imported with a `limited with' cannot be used in the
project importing it. In particular, its packages cannot be renamed and
its variables cannot be referred to.

    with "b.gpr";
    with "c.gpr";
    project A is
        for Exec_Dir use B'Exec_Dir; -- ok
    end A;

    limited with "a.gpr";   --  Cyclic dependency: A -> B -> A
    project B is
       for Exec_Dir use A'Exec_Dir; -- not ok
    end B;

    with "d.gpr";
    project C is
    end C;

    limited with "a.gpr";  --  Cyclic dependency: A -> C -> D -> A
    project D is
       for Exec_Dir use A'Exec_Dir; -- not ok
    end D;


File: gnat_ugn.info,  Node: Sharing Between Projects,  Next: Global Attributes,  Prev: Cyclic Project Dependencies,  Up: Organizing Projects into Subsystems

5.3.3 Sharing Between Projects
------------------------------

When building an application, it is common to have similar needs in
several of the projects corresponding to the subsystems under
construction. For instance, they will all have the same compilation
switches.

As seen before (see *note Tools Options in Project Files: 161.),
setting compilation switches for all sources of a subsystem is simple:
it is just a matter of adding a `Compiler.Default_Switches' attribute
to each project files with the same value. Of course, that means
duplication of data, and both places need to be changed in order to
recompile the whole application with different switches. It can become
a real problem if there are many subsystems and thus many project files
to edit.

There are two main approaches to avoiding this duplication:

   * Since `build.gpr' imports `logging.gpr', we could change it to
     reference the attribute in Logging, either through a package
     renaming, or by referencing the attribute. The following example
     shows both cases:

         project Logging is
            package Compiler is
               for Switches ("Ada")
                   use ("-O2");
            end Compiler;
            package Binder is
               for Switches ("Ada")
                   use ("-E");
            end Binder;
         end Logging;

         with "logging.gpr";
         project Build is
            package Compiler renames Logging.Compiler;
            package Binder is
               for Switches ("Ada") use Logging.Binder'Switches ("Ada");
            end Binder;
         end Build;

     The solution used for `Compiler' gets the same value for all
     attributes of the package, but you cannot modify anything from the
     package (adding extra switches or some exceptions). The second
     version is more flexible, but more verbose.

     If you need to refer to the value of a variable in an imported
     project, rather than an attribute, the syntax is similar but uses
     a "." rather than an apostrophe. For instance:

         with "imported";
         project Main is
            Var1 := Imported.Var;
         end Main;

   * The second approach is to define the switches in a third project.
     That project is set up without any sources (so that, as opposed to
     the first example, none of the project plays a special role), and
     will only be used to define the attributes. Such a project is
     typically called `shared.gpr'.

         abstract project Shared is
            for Source_Files use ();   --  no sources
            package Compiler is
               for Switches ("Ada")
                   use ("-O2");
            end Compiler;
         end Shared;

         with "shared.gpr";
         project Logging is
            package Compiler renames Shared.Compiler;
         end Logging;

         with "shared.gpr";
         project Build is
            package Compiler renames Shared.Compiler;
         end Build;

     As for the first example, we could have chosen to set the
     attributes one by one rather than to rename a package. The reason
     we explicitly indicate that `Shared' has no sources is so that it
     can be created in any directory and we are sure it shares no
     sources with `Build' or `Logging', which of course would be
     invalid.

     Note the additional use of the `abstract' qualifier in
     `shared.gpr'.  This qualifier is optional, but helps convey the
     message that we do not intend this project to have sources (see
     *note Qualified Projects: 176. for more qualifiers).


File: gnat_ugn.info,  Node: Global Attributes,  Prev: Sharing Between Projects,  Up: Organizing Projects into Subsystems

5.3.4 Global Attributes
-----------------------

We have already seen many examples of attributes used to specify a
special option of one of the tools involved in the build process. Most
of those attributes are project specific. That it to say, they only
affect the invocation of tools on the sources of the project where they
are defined.

There are a few additional attributes that apply to all projects in a
hierarchy as long as they are defined on the "main" project.  The main
project is the project explicitly mentioned on the command-line.  The
project hierarchy is the "with"-closure of the main project.

Here is a list of commonly used global attributes:

`Builder.Global_Configuration_Pragmas':

     This attribute points to a file that contains configuration pragmas
     to use when building executables. These pragmas apply for all
     executables built from this project hierarchy. As we have seen
     before, additional pragmas can be specified on a per-project basis
     by setting the `Compiler.Local_Configuration_Pragmas' attribute.

`Builder.Global_Compilation_Switches':

     This attribute is a list of compiler switches to use when
     compiling any source file in the project hierarchy. These switches
     are used in addition to the ones defined in the `Compiler'
     package, which only apply to the sources of the corresponding
     project. This attribute is indexed on the name of the language.

Using such global capabilities is convenient. It can also lead to
unexpected behavior. Especially when several subsystems are shared
among different main projects and the different global attributes are
not compatible. Note that using aggregate projects can be a safer and
more powerful replacement to global attributes.


File: gnat_ugn.info,  Node: Scenarios in Projects,  Next: Library Projects,  Prev: Organizing Projects into Subsystems,  Up: GNAT Project Manager

5.4 Scenarios in Projects
=========================

Various aspects of the projects can be modified based on `scenarios'.
These are user-defined modes that change the behavior of a project.
Typical examples are the setup of platform-specific compiler options,
or the use of a debug and a release mode (the former would activate the
generation of debug information, while the second will focus on
improving code optimization).

Let's enhance our example to support debug and release modes. The issue
is to let the user choose what kind of system he is building: use `-g'
as compiler switches in debug mode and `-O2' in release mode. We will
also set up the projects so that we do not share the same object
directory in both modes; otherwise switching from one to the other
might trigger more recompilations than needed or mix objects from the
two modes.

One naive approach is to create two different project files, say
`build_debug.gpr' and `build_release.gpr', that set the appropriate
attributes as explained in previous sections. This solution does not
scale well, because in the presence of multiple projects depending on
each other, you will also have to duplicate the complete hierarchy and
adapt the project files to point to the right copies.

Instead, project files support the notion of scenarios controlled by
external values. Such values can come from several sources (in
decreasing order of priority):

`Command line':
     When launching `gprbuild', the user can pass extra `-X' switches
     to define the external value. In our case, the command line might
     look like

         gprbuild -Pbuild.gpr -Xmode=release

`Environment variables':
     When the external value does not come from the command line, it
     can come from the value of environment variables of the
     appropriate name.  In our case, if an environment variable called
     "mode" exists, its value will be taken into account.

`External function second parameter'.

We now need to get that value in the project. The general form is to use
the predefined function `external' which returns the current value of
the external. For instance, we could set up the object directory to
point to either `obj/debug' or `obj/release' by changing our project to

    project Build is
        for Object_Dir use "obj/" & external ("mode", "debug");
        ... --  as before
    end Build;

The second parameter to `external' is optional, and is the default
value to use if "mode" is not set from the command line or the
environment.

In order to set the switches according to the different scenarios, other
constructs have to be introduced such as typed variables and case
constructions.

A `typed variable' is a variable that can take only a limited number of
values, similar to an enumeration in Ada.  Such a variable can then be
used in a `case construction' and create conditional sections in the
project. The following example shows how this can be done:

    project Build is
       type Mode_Type is ("debug", "release");  --  all possible values
       Mode : Mode_Type := external ("mode", "debug"); -- a typed variable

       package Compiler is
          case Mode is
             when "debug" =>
                for Switches ("Ada")
                    use ("-g");
             when "release" =>
                for Switches ("Ada")
                    use ("-O2");
          end case;
       end Compiler;
    end Build;

The project has suddenly grown in size, but has become much more
flexible.  `Mode_Type' defines the only valid values for the `mode'
variable. If any other value is read from the environment, an error is
reported and the project is considered as invalid.

The `Mode' variable is initialized with an external value defaulting to
`"debug"'. This default could be omitted and that would force the user
to define the value. Finally, we can use a case construction to set the
switches depending on the scenario the user has chosen.

Most aspects of the projects can depend on scenarios. The notable
exception are project dependencies (`with' clauses), which cannot
depend on a scenario.

Scenarios work the same way with `project hierarchies': you can either
duplicate a variable similar to `Mode' in each of the project (as long
as the first argument to `external' is always the same and the type is
the same), or simply set the variable in the `shared.gpr' project (see
*note Sharing Between Projects: 174.).


File: gnat_ugn.info,  Node: Library Projects,  Next: Project Extension,  Prev: Scenarios in Projects,  Up: GNAT Project Manager

5.5 Library Projects
====================

So far, we have seen examples of projects that create executables.
However, it is also possible to create libraries instead. A `library'
is a specific type of subsystem where, for convenience, objects are
grouped together using system-specific means such as archives or
windows DLLs.

Library projects provide a system- and language-independent way of
building both `static' and `dynamic' libraries. They also support the
concept of `standalone libraries' (SAL) which offer two significant
properties: the elaboration (e.g. initialization) of the library is
either automatic or very simple; a change in the implementation part of
the library implies minimal post-compilation actions on the complete
system and potentially no action at all for the rest of the system in
the case of dynamic SALs.

There is a restriction on shared library projects: by default, they are
only allowed to import other shared library projects. They are not
allowed to import non library projects or static library projects.

The GNAT Project Manager takes complete care of the library build,
rebuild and installation tasks, including recompilation of the source
files for which objects do not exist or are not up to date, assembly of
the library archive, and installation of the library (i.e., copying
associated source, object and `ALI' files to the specified location).

* Menu:

* Building Libraries::
* Using Library Projects::
* Stand-alone Library Projects::
* Installing a library with project files::


File: gnat_ugn.info,  Node: Building Libraries,  Next: Using Library Projects,  Up: Library Projects

5.5.1 Building Libraries
------------------------

Let's enhance our example and transform the `logging' subsystem into a
library.  In order to do so, a few changes need to be made to
`logging.gpr'.  Some attributes need to be defined: at least
`Library_Name' and `Library_Dir'; in addition, some other attributes
can be used to specify specific aspects of the library. For
readability, it is also recommended (although not mandatory), to use
the qualifier `library' in front of the `project' keyword.

`Library_Name':

     This attribute is the name of the library to be built. There is no
     restriction on the name of a library imposed by the project
     manager, except for stand-alone libraries whose names must follow
     the syntax of Ada identifiers; however, there may be
     system-specific restrictions on the name.  In general, it is
     recommended to stick to alphanumeric characters (and possibly
     single underscores) to help portability.

`Library_Dir':

     This attribute  is the path (absolute or relative) of the
     directory where the library is to be installed. In the process of
     building a library, the sources are compiled, the object files end
     up  in the explicit or implicit `Object_Dir' directory. When all
     sources of a library are compiled, some of the compilation
     artifacts, including the library itself, are copied to the
     library_dir directory. This directory must exist and be writable.
     It must also be different from the object directory so that cleanup
     activities in the Library_Dir do not affect recompilation needs.

Here is the new version of `logging.gpr' that makes it a library:

    library project Logging is          --  "library" is optional
       for Library_Name use "logging";  --  will create "liblogging.a" on Unix
       for Object_Dir   use "obj";
       for Library_Dir  use "lib";      --  different from object_dir
    end Logging;

Once the above two attributes are defined, the library project is valid
and is enough for building a library with default characteristics.
Other library-related attributes can be used to change the defaults:

`Library_Kind':

     The value of this attribute must be either `"static"', `"dynamic"'
     or `"relocatable"' (the latter is a synonym for dynamic). It
     indicates which kind of library should be built (the default is to
     build a static library, that is an archive of object files that
     can potentially be linked into a static executable). When the
     library is set to be dynamic, a separate image is created that
     will be loaded independently, usually at the start of the main
     program execution. Support for dynamic libraries is very platform
     specific, for instance on Windows it takes the form of a DLL while
     on GNU/Linux, it is a dynamic elf image whose suffix is usually
     `.so'. Library project files, on the other hand, can be written in
     a platform independent way so that the same project file can be
     used to build a library on different operating systems.

     If you need to build both a static and a dynamic library, it is
     recommended to use two different object directories, since in some
     cases some extra code needs to be generated for the latter. For
     such cases, one can either define two different project files, or
     a single one that uses scenarios to indicate the various kinds of
     library to be built and their corresponding object_dir.

`Library_ALI_Dir':

     This attribute may be specified to indicate the directory where
     the ALI files of the library are installed. By default, they are
     copied into the `Library_Dir' directory, but as for the
     executables where we have a separate `Exec_Dir' attribute, you
     might want to put them in a separate directory since there can be
     hundreds of them. The same restrictions as for the `Library_Dir'
     attribute apply.

`Library_Version':

     This attribute is platform dependent, and has no effect on Windows.
     On Unix, it is used only for dynamic libraries as the internal
     name of the library (the `"soname"'). If the library file name
     (built from the `Library_Name') is different from the
     `Library_Version', then the library file will be a symbolic link
     to the actual file whose name will be `Library_Version'. This
     follows the usual installation schemes for dynamic libraries on
     many Unix systems.

         project Logging is
            Version := "1";
            for Library_Dir use "lib";
            for Library_Name use "logging";
            for Library_Kind use "dynamic";
            for Library_Version use "liblogging.so." & Version;
         end Logging;

     After the compilation, the directory `lib' will contain both a
     `libdummy.so.1' library and a symbolic link to it called
     `libdummy.so'.

`Library_GCC':

     This attribute is the name of the tool to use instead of "gcc" to
     link shared libraries. A common use of this attribute is to define
     a wrapper script that accomplishes specific actions before calling
     gcc (which itself calls the linker to build the library image).

`Library_Options':

     This attribute may be used to specify additional switches (last
     switches) when linking a shared library.

     It may also be used to add foreign object files to a static
     library.  Each string in Library_Options is an absolute or
     relative path of an object file. When a relative path, it is
     relative to the object directory.

`Leading_Library_Options':

     This attribute, that is taken into account only by `gprbuild', may
     be used to specified leading options (first switches) when linking
     a shared library.

`Linker.Linker_Options':

     This attribute specifies additional switches to be given to the
     linker when linking an executable. It is ignored when defined in
     the main project and taken into account in all other projects that
     are imported directly or indirectly. These switches complement the
     `Linker.Switches' defined in the main project. This is useful when
     a particular subsystem depends on an external library: adding this
     dependency as a `Linker_Options' in the project of the subsystem
     is more convenient than adding it to all the `Linker.Switches' of
     the main projects that depend upon this subsystem.


File: gnat_ugn.info,  Node: Using Library Projects,  Next: Stand-alone Library Projects,  Prev: Building Libraries,  Up: Library Projects

5.5.2 Using Library Projects
----------------------------

When the builder detects that a project file is a library project file,
it recompiles all sources of the project that need recompilation and
rebuild the library if any of the sources have been recompiled. It then
groups all object files into a single file, which is a shared or a
static library. This library can later on be linked with multiple
executables. Note that the use of shard libraries reduces the size of
the final executable and can also reduce the memory footprint at
execution time when the library is shared among several executables.

`gprbuild also allows to build **multi-language libraries*' when
specifying sources from multiple languages.

A non-library project can import a library project. When the builder is
invoked on the former, the library of the latter is only rebuilt when
absolutely necessary. For instance, if a unit of the library is not
up-to-date but none of the executables need this unit, then the unit is
not recompiled and the library is not reassembled.  For instance, let's
assume in our example that logging has the following sources:
`log1.ads', `log1.adb', `log2.ads' and `log2.adb'. If `log1.adb' has
been modified, then the library `liblogging' will be rebuilt when
compiling all the sources of `Build' only if `proc.ads', `pack.ads' or
`pack.adb' include a `"with Log1"'.

To ensure that all the sources in the `Logging' library are up to date,
and that all the sources of `Build' are also up to date, the following
two commands need to be used:

    gprbuild -Plogging.gpr
    gprbuild -Pbuild.gpr

All `ALI' files will also be copied from the object directory to the
library directory. To build executables, `gprbuild' will use the
library rather than the individual object files.

Library projects can also be useful to describe a library that needs to
be used but, for some reason, cannot be rebuilt. For instance, it is
the case when some of the library sources are not available. Such
library projects need to use the `Externally_Built' attribute as in the
example below:

    library project Extern_Lib is
       for Languages    use ("Ada", "C");
       for Source_Dirs  use ("lib_src");
       for Library_Dir  use "lib2";
       for Library_Kind use "dynamic";
       for Library_Name use "l2";
       for Externally_Built use "true";  --  <<<<
    end Extern_Lib;

In the case of externally built libraries, the `Object_Dir' attribute
does not need to be specified because it will never be used.

The main effect of using such an externally built library project is
mostly to affect the linker command in order to reference the desired
library. It can also be achieved by using `Linker.Linker_Options' or
`Linker.Switches' in the project corresponding to the subsystem needing
this external library.  This latter method is more straightforward in
simple cases but when several subsystems depend upon the same external
library, finding the proper place for the `Linker.Linker_Options' might
not be easy and if it is not placed properly, the final link command is
likely to present ordering issues.  In such a situation, it is better
to use the externally built library project so that all other
subsystems depending on it can declare this dependency thanks to a
project `with' clause, which in turn will trigger the builder to find
the proper order of libraries in the final link command.


File: gnat_ugn.info,  Node: Stand-alone Library Projects,  Next: Installing a library with project files,  Prev: Using Library Projects,  Up: Library Projects

5.5.3 Stand-alone Library Projects
----------------------------------

A `stand-alone library' is a library that contains the necessary code to
elaborate the Ada units that are included in the library. A stand-alone
library is a convenient way to add an Ada subsystem to a more global
system whose main is not in Ada since it makes the elaboration of the
Ada part mostly transparent. However, stand-alone libraries are also
useful when the main is in Ada: they provide a means for minimizing
relinking & redeployment of complex systems when localized changes are
made.

The name of a stand-alone library, specified with attribute
`Library_Name', must have the syntax of an Ada identifier.

The most prominent characteristic of a stand-alone library is that it
offers a distinction between interface units and implementation units.
Only the former are visible to units outside the library. A stand-alone
library project is thus characterised by a third attribute, usually
`Library_Interface', in addition to the two attributes that make a
project a Library Project (`Library_Name' and `Library_Dir'). This
third attribute may also be `Interfaces'. `Library_Interface' only
works when the interface is in Ada and takes a list of units as
parameter. `Interfaces' works for any supported language and takes a
list of sources as parameter.

`Library_Interface':

     This attribute defines an explicit subset of the units of the
     project. Units from projects importing this library project may
     only "with" units whose sources are listed in the
     `Library_Interface'. Other sources are considered implementation
     units.

         for Library_Dir use "lib";
         for Library_Name use "logging";
         for Library_Interface use ("lib1", "lib2");  --  unit names

`Interfaces'

     This attribute defines an explicit subset of the source files of a
     project.  Sources from projects importing this project, can only
     depend on sources from this subset. This attribute can be used on
     non library projects. It can also be used as a replacement for
     attribute `Library_Interface', in which case, units have to be
     replaced by source files. For multi-language library projects, it
     is the only way to make the project a Stand-Alone Library project
     whose interface is not purely Ada.

`Library_Standalone':

     This attribute defines the kind of standalone library to build.
     Values are either `standard' (the default), `no' or
     `encapsulated'. When `standard' is used the code to elaborate and
     finalize the library is embedded, when `encapsulated' is used the
     library can furthermore depend only on static libraries (including
     the GNAT runtime). This attribute can be set to `no' to make it
     clear that the library should not be standalone in which case the
     `Library_Interface' should not defined. Note that this attribute
     only applies to shared libraries, so `Library_Kind' must be set to
     `dynamic'.

         for Library_Dir use "lib";
         for Library_Name use "logging";
         for Library_Kind use "dynamic";
         for Library_Interface use ("lib1", "lib2");  --  unit names
         for Library_Standalone use "encapsulated";

In order to include the elaboration code in the stand-alone library,
the binder is invoked on the closure of the library units creating a
package whose name depends on the library name (b~logging.ads/b in the
example).  This binder-generated package includes `initialization' and
`finalization' procedures whose names depend on the library name
(`logginginit' and `loggingfinal' in the example). The object
corresponding to this package is included in the library.

`Library_Auto_Init':

     A dynamic stand-alone Library is automatically initialized if
     automatic initialization of Stand-alone Libraries is supported on
     the platform and if attribute `Library_Auto_Init' is not specified
     or is specified with the value "true". A static Stand-alone
     Library is never automatically initialized. Specifying "false" for
     this attribute prevents automatic initialization.

     When a non-automatically initialized stand-alone library is used
     in an executable, its initialization procedure must be called
     before any service of the library is used. When the main
     subprogram is in Ada, it may mean that the initialization
     procedure has to be called during elaboration of another package.

`Library_Dir':

     For a stand-alone library, only the `ALI' files of the interface
     units (those that are listed in attribute `Library_Interface') are
     copied to the library directory. As a consequence, only the
     interface units may be imported from Ada units outside of the
     library. If other units are imported, the binding phase will fail.

`Binder.Default_Switches':

     When a stand-alone library is bound, the switches that are
     specified in the attribute `Binder.Default_Switches ("Ada")' are
     used in the call to `gnatbind'.

`Library_Src_Dir':

     This attribute defines the location (absolute or relative to the
     project directory) where the sources of the interface units are
     copied at installation time.  These sources includes the specs of
     the interface units along with the closure of sources necessary to
     compile them successfully. That may include bodies and subunits,
     when pragmas `Inline' are used, or when there are generic units in
     specs. This directory cannot point to the object directory or one
     of the source directories, but it can point to the library
     directory, which is the default value for this attribute.

`Library_Symbol_Policy':

     This attribute controls the export of symbols and, on some
     platforms (like VMS) that have the notions of major and minor IDs
     built in the library files, it controls the setting of these IDs.
     It is not supported on all platforms (where it will just have no
     effect). It may have one of the following values:

        * `"autonomous"' or `"default"': exported symbols are not
          controlled

        * `"compliant"': if attribute `Library_Reference_Symbol_File'
          is not defined, then it is equivalent to policy "autonomous".
          If there are exported symbols in the reference symbol file
          that are not in the object files of the interfaces, the major
          ID of the library is increased.  If there are symbols in the
          object files of the interfaces that are not in the reference
          symbol file, these symbols are put at the end of the list in
          the newly created symbol file and the minor ID is increased.

        * `"controlled"': the attribute `Library_Reference_Symbol_File'
          must be defined. The library will fail to build if the
          exported symbols in the object files of the interfaces do not
          match exactly the symbol in the symbol file.

        * `"restricted"': The attribute `Library_Symbol_File' must be
          defined.  The library will fail to build if there are symbols
          in the symbol file that are not in the exported symbols of
          the object files of the interfaces.  Additional symbols in
          the object files are not added to the symbol file.

        * `"direct"': The attribute `Library_Symbol_File' must be
          defined and must designate an existing file in the object
          directory. This symbol file is passed directly to the
          underlying linker without any symbol processing.

`Library_Reference_Symbol_File'

     This attribute may define the path name of a reference symbol file
     that is read when the symbol policy is either "compliant" or
     "controlled", on platforms that support symbol control, such as
     VMS, when building a stand-alone library. The path may be an
     absolute path or a path relative to the project directory.

`Library_Symbol_File'

     This attribute may define the name of the symbol file to be
     created when building a stand-alone library when the symbol policy
     is either "compliant", "controlled" or "restricted", on platforms
     that support symbol control, such as VMS. When symbol policy is
     "direct", then a file with this name must exist in the object
     directory.


File: gnat_ugn.info,  Node: Installing a library with project files,  Prev: Stand-alone Library Projects,  Up: Library Projects

5.5.4 Installing a library with project files
---------------------------------------------

When using project files, a usable version of the library is created in
the directory specified by the `Library_Dir' attribute of the library
project file. Thus no further action is needed in order to make use of
the libraries that are built as part of the general application build.

You may want to install a library in a context different from where the
library is built. This situation arises with third party suppliers, who
may want to distribute a library in binary form where the user is not
expected to be able to recompile the library. The simplest option in
this case is to provide a project file slightly different from the one
used to build the library, by using the `externally_built' attribute.
See *note Using Library Projects: 17e.

Another option is to use `gprinstall' to install the library in a
different context than the build location. `gprinstall' automatically
generates a project to use this library, and also copies the minimum
set of sources needed to use the library to the install location.
*note Installation: 16b.


File: gnat_ugn.info,  Node: Project Extension,  Next: Aggregate Projects,  Prev: Library Projects,  Up: GNAT Project Manager

5.6 Project Extension
=====================

During development of a large system, it is sometimes necessary to use
modified versions of some of the source files, without changing the
original sources. This can be achieved through the `project extension'
facility.

Suppose for instance that our example `Build' project is built every
night for the whole team, in some shared directory. A developer usually
needs to work on a small part of the system, and might not want to have
a copy of all the sources and all the object files (mostly because that
would require too much disk space, time to recompile everything). He
prefers to be able to override some of the source files in his
directory, while taking advantage of all the object files generated at
night.

Another example can be taken from large software systems, where it is
common to have multiple implementations of a common interface; in Ada
terms, multiple versions of a package body for the same spec.  For
example, one implementation might be safe for use in tasking programs,
while another might be used only in sequential applications.  This can
be modeled in GNAT using the concept of `project extension'.  If one
project (the 'child') `extends' another project (the 'parent') then by
default all source files of the parent project are inherited by the
child, but the child project can override any of the parent's source
files with new versions, and can also add new files or remove
unnecessary ones.  This facility is the project analog of a type
extension in object-oriented programming.  Project hierarchies are
permitted (an extending project may itself be extended), and a project
that extends a project can also import other projects.

A third example is that of using project extensions to provide different
versions of the same system. For instance, assume that a `Common'
project is used by two development branches. One of the branches has now
been frozen, and no further change can be done to it or to `Common'.
However, the other development branch still needs evolution of `Common'.
Project extensions provide a flexible solution to create a new version
of a subsystem while sharing and reusing as much as possible from the
original one.

A project extension implicitly inherits all the sources and objects
from the project it extends. It is possible to create a new version of
some of the sources in one of the additional source directories of the
extending project. Those new versions hide the original versions.
Adding new sources or removing existing ones is also possible. Here is
an example on how to extend the project `Build' from previous examples:

    project Work extends "../bld/build.gpr" is
    end Work;

The project after `extends' is the one being extended. As usual, it can
be specified using an absolute path, or a path relative to any of the
directories in the project path (see *note Project Dependencies: 16f.).
This project does not specify source or object directories, so the
default values for these attributes will be used that is to say the
current directory (where project `Work' is placed). We can compile that
project with

    gprbuild -Pwork

If no sources have been placed in the current directory, this command
won't do anything, since this project does not change the sources it
inherited from `Build', therefore all the object files in `Build' and
its dependencies are still valid and are reused automatically.

Suppose we now want to supply an alternate version of `pack.adb' but use
the existing versions of `pack.ads' and `proc.adb'.  We can create the
new file in Work's current directory (likely by copying the one from the
`Build' project and making changes to it. If new packages are needed at
the same time, we simply create new files in the source directory of the
extending project.

When we recompile, `gprbuild' will now automatically recompile this
file (thus creating `pack.o' in the current directory) and any file
that depends on it (thus creating `proc.o'). Finally, the executable is
also linked locally.

Note that we could have obtained the desired behavior using project
import rather than project inheritance. A `base' project would contain
the sources for `pack.ads' and `proc.adb', and `Work' would import
`base' and add `pack.adb'. In this scenario,  `base' cannot contain the
original version of `pack.adb' otherwise there would be 2 versions of
the same unit in the closure of the project and this is not allowed.
Generally speaking, it is not recommended to put the spec and the body
of a unit in different projects since this affects their autonomy and
reusability.

In a project file that extends another project, it is possible to
indicate that an inherited source is `not part' of the sources of the
extending project. This is necessary sometimes when a package spec has
been overridden and no longer requires a body: in this case, it is
necessary to indicate that the inherited body is not part of the sources
of the project, otherwise there will be a compilation error when
compiling the spec.

For that purpose, the attribute `Excluded_Source_Files' is used.  Its
value is a list of file names.  It is also possible to use attribute
`Excluded_Source_List_File'.  Its value is the path of a text file
containing one file name per line.

    project Work extends "../bld/build.gpr" is
       for Source_Files use ("pack.ads");
       --  New spec of Pkg does not need a completion
       for Excluded_Source_Files use ("pack.adb");
    end Work;

All packages that are not declared in the extending project are
inherited from the project being extended, with their attributes, with
the exception of `Linker'Linker_Options' which is never inherited. In
particular, an extending project retains all the switches specified in
the project being extended.

At the project level, if they are not declared in the extending
project, some attributes are inherited from the project being extended.
They are: `Languages', `Main' (for a root non library project) and
`Library_Name' (for a project extending a library project).

* Menu:

* Project Hierarchy Extension::


File: gnat_ugn.info,  Node: Project Hierarchy Extension,  Up: Project Extension

5.6.1 Project Hierarchy Extension
---------------------------------

One of the fundamental restrictions in project extension is the
following: `A project is not allowed to import directly or indirectly
at the same time an extending project and one of its ancestors'.

For example, consider the following hierarchy of projects.

    a.gpr  contains package A1
    b.gpr, imports a.gpr and contains B1, which depends on A1
    c.gpr, imports b.gpr and contains C1, which depends on B1

If we want to locally extend the packages `A1' and `C1', we need to
create several extending projects:

    a_ext.gpr which extends a.gpr, and overrides A1
    b_ext.gpr which extends b.gpr and imports a_ext.gpr
    c_ext.gpr which extends c.gpr, imports b_ext.gpr and overrides C1

    project A_Ext extends "a.gpr" is
       for Source_Files use ("a1.adb", "a1.ads");
    end A_Ext;

    with "a_ext.gpr";
    project B_Ext extends "b.gpr" is
    end B_Ext;

    with "b_ext.gpr";
    project C_Ext extends "c.gpr" is
       for Source_Files use ("c1.adb");
    end C_Ext;

The extension `b_ext.gpr' is required, even though we are not overriding
any of the sources of `b.gpr' because otherwise `c_expr.gpr' would
import `b.gpr' which itself knows nothing about `a_ext.gpr'.

When extending a large system spanning multiple projects, it is often
inconvenient to extend every project in the hierarchy that is impacted
by a small change introduced in a low layer. In such cases, it is
possible to create an `implicit extension' of an entire hierarchy using
`extends all' relationship.

When the project is extended using `extends all' inheritance, all
projects that are imported by it, both directly and indirectly, are
considered virtually extended. That is, the project manager creates
implicit projects that extend every project in the hierarchy; all these
implicit projects do not control sources on their own and use the
object directory of the "extending all" project.

It is possible to explicitly extend one or more projects in the
hierarchy in order to modify the sources. These extending projects must
be imported by the "extending all" project, which will replace the
corresponding virtual projects with the explicit ones.

When building such a project hierarchy extension, the project manager
will ensure that both modified sources and sources in implicit
extending projects that depend on them are recompiled.

Thus, in our example we could create the following projects instead:

    a_ext.gpr, extends a.gpr and overrides A1
    c_ext.gpr, "extends all" c.gpr, imports a_ext.gpr and overrides C1

    project A_Ext extends "a.gpr" is
       for Source_Files use ("a1.adb", "a1.ads");
    end A_Ext;

    with "a_ext.gpr";
    project C_Ext extends all "c.gpr" is
      for Source_Files use ("c1.adb");
    end C_Ext;

When building project `c_ext.gpr', the entire modified project space is
considered for recompilation, including the sources of `b.gpr' that are
impacted by the changes in `A1' and `C1'.


File: gnat_ugn.info,  Node: Aggregate Projects,  Next: Aggregate Library Projects,  Prev: Project Extension,  Up: GNAT Project Manager

5.7 Aggregate Projects
======================

Aggregate projects are an extension of the project paradigm, and are
meant to solve a few specific use cases that cannot be solved directly
using standard projects. This section will go over a few of these use
cases to try to explain what you can use aggregate projects for.

* Menu:

* Building all main programs from a single project tree::
* Building a set of projects with a single command::
* Define a build environment::
* Performance improvements in builder::
* Syntax of aggregate projects::
* package Builder in aggregate projects::


File: gnat_ugn.info,  Node: Building all main programs from a single project tree,  Next: Building a set of projects with a single command,  Up: Aggregate Projects

5.7.1 Building all main programs from a single project tree
-----------------------------------------------------------

Most often, an application is organized into modules and submodules,
which are very conveniently represented as a project tree or graph (the
root project A `with's the projects for each modules (say B and C),
which in turn `with' projects for submodules.

Very often, modules will build their own executables (for testing
purposes for instance), or libraries (for easier reuse in various
contexts).

However, if you build your project through `gprbuild', using a syntax
similar to

    gprbuild -PA.gpr

this will only rebuild the main programs of project A, not those of the
imported projects B and C. Therefore you have to spawn several
`gprbuild' commands, one per project, to build all executables.  This
is a little inconvenient, but more importantly is inefficient because
`gprbuild' needs to do duplicate work to ensure that sources are
up-to-date, and cannot easily compile things in parallel when using the
-j switch.

Also libraries are always rebuilt when building a project.

You could therefore define an aggregate project Agg that groups A, B
and C. Then, when you build with

    gprbuild -PAgg.gpr

this will build all mains from A, B and C.

    aggregate project Agg is
       for Project_Files use ("a.gpr", "b.gpr", "c.gpr");
    end Agg;

If B or C do not define any main program (through their Main
attribute), all their sources are built. When you do not group them in
the aggregate project, only those sources that are needed by A will be
built.

If you add a main to a project P not already explicitly referenced in
the aggregate project, you will need to add "p.gpr" in the list of
project files for the aggregate project, or the main will not be built
when building the aggregate project.


File: gnat_ugn.info,  Node: Building a set of projects with a single command,  Next: Define a build environment,  Prev: Building all main programs from a single project tree,  Up: Aggregate Projects

5.7.2 Building a set of projects with a single command
------------------------------------------------------

One other case is when you have multiple applications and libraries
that are built independently from each other (but can be built in
parallel). For instance, you have a project tree rooted at A, and
another one (which might share some subprojects) rooted at B.

Using only `gprbuild', you could do

    gprbuild -PA.gpr
    gprbuild -PB.gpr

to build both. But again, `gprbuild' has to do some duplicate work for
those files that are shared between the two, and cannot truly build
things in parallel efficiently.

If the two projects are really independent, share no sources other than
through a common subproject, and have no source files with a common
basename, you could create a project C that imports A and B. But these
restrictions are often too strong, and one has to build them
independently. An aggregate project does not have these limitations and
can aggregate two project trees that have common sources.

This scenario is particularly useful in environments like VxWorks 653
where the applications running in the multiple partitions can be built
in parallel through a single `gprbuild' command. This also works nicely
with Annex E.


File: gnat_ugn.info,  Node: Define a build environment,  Next: Performance improvements in builder,  Prev: Building a set of projects with a single command,  Up: Aggregate Projects

5.7.3 Define a build environment
--------------------------------

The environment variables at the time you launch `gprbuild' will
influence the view these tools have of the project (PATH to find the
compiler, ADA_PROJECT_PATH or GPR_PROJECT_PATH to find the projects,
environment variables that are referenced in project files through the
"external" built-in function, ...). Several command line switches can
be used to override those (-X or -aP), but on some systems and with
some projects, this might make the command line too long, and on all
systems often make it hard to read.

An aggregate project can be used to set the environment for all
projects built through that aggregate. One of the nice aspects is that
you can put the aggregate project under configuration management, and
make sure all your user have a consistent environment when building.
The syntax looks like

    aggregate project Agg is
       for Project_Files use ("A.gpr", "B.gpr");
       for Project_Path use ("../dir1", "../dir1/dir2");
       for External ("BUILD") use "PRODUCTION";

       package Builder is
          for Global_Compilation_Switches ("Ada") use ("-g");
       end Builder;
    end Agg;

One of the often requested features in projects is to be able to
reference external variables in `with' declarations, as in

    with external("SETUP") & "path/prj.gpr";   --  ILLEGAL
    project MyProject is
       ...
    end MyProject;

For various reasons, this is not allowed. But using aggregate projects
provide an elegant solution. For instance, you could use a project file
like:

    aggregate project Agg is
        for Project_Path use (external("SETUP") & "path");
        for Project_Files use ("myproject.gpr");
    end Agg;

    with "prj.gpr";  --  searched on Agg'Project_Path
    project MyProject is
       ...
    end MyProject;


File: gnat_ugn.info,  Node: Performance improvements in builder,  Next: Syntax of aggregate projects,  Prev: Define a build environment,  Up: Aggregate Projects

5.7.4 Performance improvements in builder
-----------------------------------------

The loading of aggregate projects is optimized in `gprbuild', so that
all files are searched for only once on the disk (thus reducing the
number of system calls and contributing to faster compilation times,
especially on systems with sources on remote servers). As part of the
loading, `gprbuild' computes how and where a source file should be
compiled, and even if it is found several times in the aggregated
projects it will be compiled only once.

Since there is no ambiguity as to which switches should be used, files
can be compiled in parallel (through the usual -j switch) and this can
be done while maximizing the use of CPUs (compared to launching
multiple `gprbuild' commands in parallel).


File: gnat_ugn.info,  Node: Syntax of aggregate projects,  Next: package Builder in aggregate projects,  Prev: Performance improvements in builder,  Up: Aggregate Projects

5.7.5 Syntax of aggregate projects
----------------------------------

An aggregate project follows the general syntax of project files. The
recommended extension is still `.gpr'. However, a special `aggregate'
qualifier must be put before the keyword `project'.

An aggregate project cannot `with' any other project (standard or
aggregate), except an abstract project which can be used to share
attribute values. Also, aggregate projects cannot be extended or
imported though a `with' clause by any other project. Building other
aggregate projects from an aggregate project is done through the
Project_Files attribute (see below).

An aggregate project does not have any source files directly (only
through other standard projects). Therefore a number of the standard
attributes and packages are forbidden in an aggregate project. Here is
the (non exhaustive) list:

   * Languages

   * Source_Files, Source_List_File and other attributes dealing with
     list of sources.

   * Source_Dirs, Exec_Dir and Object_Dir

   * Library_Dir, Library_Name and other library-related attributes

   * Main

   * Roots

   * Externally_Built

   * Inherit_Source_Path

   * Excluded_Source_Dirs

   * Locally_Removed_Files

   * Excluded_Source_Files

   * Excluded_Source_List_File

   * Interfaces

The only package that is authorized (albeit optional) is Builder. Other
packages (in particular Compiler, Binder and Linker) are forbidden.

The following three attributes can be used only in an aggregate project:

`Project_Files':

     This attribute is compulsory (or else we are not aggregating any
     project, and thus not doing anything). It specifies a list of
     `.gpr' files that are grouped in the aggregate. The list may be
     empty. The project files can be either other aggregate projects,
     or standard projects. When grouping standard projects, you can
     have both the root of a project tree (and you do not need to
     specify all its imported projects), and any project within the
     tree.

     Basically, the idea is to specify all those projects that have
     main programs you want to build and link, or libraries you want to
     build. You can even specify projects that do not use the Main
     attribute nor the `Library_*' attributes, and the result will be to
     build all their source files (not just the ones needed by other
     projects).

     The file can include paths (absolute or relative). Paths are
     relative to the location of the aggregate project file itself (if
     you use a base name, we expect to find the .gpr file in the same
     directory as the aggregate project file). The environment
     variables `ADA_PROJECT_PATH', `GPR_PROJECT_PATH' and
     `GPR_PROJECT_PATH_FILE' are not used to find the project files.
     The extension `.gpr' is mandatory, since this attribute contains
     file names, not project names.

     Paths can also include the `"*"' and `"**"' globbing patterns. The
     latter indicates that any subdirectory (recursively) will be
     searched for matching files. The latter (`"**"') can only occur at
     the last position in the directory part (ie `"a/**/*.gpr"' is
     supported, but not `"**/a/*.gpr"'). Starting the pattern with
     `"**"' is equivalent to starting with `"./**"'.

     For now, the pattern `"*"' is only allowed in the filename part,
     not in the directory part. This is mostly for efficiency reasons
     to limit the number of system calls that are needed.

     Here are a few valid examples:

         for Project_Files use ("a.gpr", "subdir/b.gpr");
         --  two specific projects relative to the directory of agg.gpr

         for Project_Files use ("/.gpr");
         --  all projects recursively

`Project_Path':

     This attribute can be used to specify a list of directories in
     which to look for project files in `with' declarations.

     When you specify a project in Project_Files (say `x/y/a.gpr'), and
     `a.gpr' imports a project `b.gpr', only `b.gpr' is searched in the
     project path. `a.gpr' must be exactly at `<dir of the
     aggregate>/x/y/a.gpr'.

     This attribute, however, does not affect the search for the
     aggregated project files specified with `Project_Files'.

     Each aggregate project has its own `Project_Path' (that is if
     `agg1.gpr' includes `agg2.gpr', they can potentially both have a
     different `Project_Path').

     This project path is defined as the concatenation, in that order,
     of:

        * the current directory;

        * followed by the command line -aP switches;

        * then the directories from the GPR_PROJECT_PATH and
          ADA_PROJECT_PATH environment variables;

        * then the directories from the Project_Path attribute;

        * and finally the predefined directories.

     In the example above, agg2.gpr's project path is not influenced by
     the attribute agg1'Project_Path, nor is agg1 influenced by
     agg2'Project_Path.

     This can potentially lead to errors. Consider the following
     example:

         --
         --  +---------------+                  +----------------+
         --  | Agg1.gpr      |-=--includes--=-->| Agg2.gpr       |
         --  |  'project_path|                  |  'project_path |
         --  |               |                  |                |
         --  +---------------+                  +----------------+
         --        :                                   :
         --        includes                        includes
         --        :                                   :
         --        v                                   v
         --    +-------+                          +---------+
         --    | P.gpr |<---------- withs --------|  Q.gpr  |
         --    +-------+---------\                +---------+
         --        |             |
         --        withs         |
         --        |             |
         --        v             v
         --    +-------+      +---------+
         --    | R.gpr |      | R'.gpr  |
         --    +-------+      +---------+

     When looking for p.gpr, both aggregates find the same physical
     file on the disk. However, it might happen that with their
     different project paths, both aggregate projects would in fact
     find a different r.gpr.  Since we have a common project (p.gpr)
     "with"ing two different r.gpr, this will be reported as an error
     by the builder.

     Directories are relative to the location of the aggregate project
     file.

     Example:

         for Project_Path use ("/usr/local/gpr", "gpr/");

`External':

     This attribute can be used to set the value of environment
     variables as retrieved through the `external' function in
     projects. It does not affect the environment variables themselves
     (so for instance you cannot use it to change the value of your
     PATH as seen from the spawned compiler).

     This attribute affects the external values as seen in the rest of
     the aggregate project, and in the aggregated projects.

     The exact value of external a variable comes from one of three
     sources (each level overrides the previous levels):

        * An External attribute in aggregate project, for instance `for
          External ("BUILD_MODE") use "DEBUG"';

        * Environment variables.  These override the value given by the
          attribute, so that users can override the value set in the
          (presumably shared with others team members) aggregate
          project.

        * The -X command line switch to `gprbuild'.  This always takes
          precedence.

     This attribute is only taken into account in the main aggregate
     project (i.e. the one specified on the command line to `gprbuild'),
     and ignored in other aggregate projects. It is invalid in standard
     projects.  The goal is to have a consistent value in all projects
     that are built through the aggregate, which would not be the case
     in the diamond case: A groups the aggregate projects B and C,
     which both (either directly or indirectly) build the project P. If
     B and C could set different values for the environment variables,
     we would have two different views of P, which in particular might
     impact the list of source files in P.


File: gnat_ugn.info,  Node: package Builder in aggregate projects,  Prev: Syntax of aggregate projects,  Up: Aggregate Projects

5.7.6 package Builder in aggregate projects
-------------------------------------------

As mentioned above, only the package Builder can be specified in an
aggregate project. In this package, only the following attributes are
valid:

`Switches':

     This attribute gives the list of switches to use for `gprbuild'.
     Because no mains can be specified for aggregate projects, the only
     possible index for attribute `Switches' is `others'. All other
     indexes will be ignored.

     Example:

         for Switches (others) use ("-v", "-k", "-j8");

     These switches are only read from the main aggregate project (the
     one passed on the command line), and ignored in all other aggregate
     projects or projects.

     It can only contain builder switches, not compiler switches.

`Global_Compilation_Switches'

     This attribute gives the list of compiler switches for the various
     languages. For instance,

         for Global_Compilation_Switches ("Ada") use ("O1", "-g");
         for Global_Compilation_Switches ("C")   use ("-O2");

     This attribute is only taken into account in the aggregate project
     specified on the command line, not in other aggregate projects.

     In the projects grouped by that aggregate, the attribute
     Builder.Global_Compilation_Switches is also ignored. However, the
     attribute Compiler.Default_Switches will be taken into account (but
     that of the aggregate have higher priority). The attribute
     Compiler.Switches is also taken into account and can be used to
     override the switches for a specific file. As a result, it always
     has priority.

     The rules are meant to avoid ambiguities when compiling. For
     instance, aggregate project Agg groups the projects A and B, that
     both depend on C. Here is an extra for all of these projects:

         aggregate project Agg is
             for Project_Files use ("a.gpr", "b.gpr");
             package Builder is
                for Global_Compilation_Switches ("Ada") use ("-O2");
             end Builder;
         end Agg;

         with "c.gpr";
         project A is
             package Builder is
                for Global_Compilation_Switches ("Ada") use ("-O1");
                --  ignored
             end Builder;

             package Compiler is
                for Default_Switches ("Ada")
                    use ("-O1", "-g");
                for Switches ("a_file1.adb")
                    use ("-O0");
             end Compiler;
         end A;

         with "c.gpr";
         project B is
             package Compiler is
                for Default_Switches ("Ada") use ("-O0");
             end Compiler;
         end B;

         project C is
             package Compiler is
                for Default_Switches ("Ada")
                    use ("-O3",
                         "-gnatn");
                for Switches ("c_file1.adb")
                    use ("-O0", "-g");
             end Compiler;
         end C;

     then the following switches are used:

        * all files from project A except a_file1.adb are compiled with
          "-O2 -g", since the aggregate project has priority.

        * the file a_file1.adb is compiled with "-O0", since the
          Compiler.Switches has priority

        * all files from project B are compiled with "-O2", since the
          aggregate project has priority

        * all files from C are compiled with "-O2 -gnatn", except for
          c_file1.adb which is compiled with "-O0 -g"

     Even though C is seen through two paths (through A and through B),
     the switches used by the compiler are unambiguous.

`Global_Configuration_Pragmas'

     This attribute can be used to specify a file containing
     configuration pragmas, to be passed to the Ada compiler.  Since we
     ignore the package Builder in other aggregate projects and
     projects, only those pragmas defined in the main aggregate project
     will be taken into account.

     Projects can locally add to those by using the
     `Compiler.Local_Configuration_Pragmas' attribute if they need.

`Global_Config_File'

     This attribute, indexed with a language name, can be used to
     specify a config when compiling sources of the language. For Ada,
     these files are configuration pragmas files.

For projects that are built through the aggregate, the package Builder
is ignored, except for the Executable attribute which specifies the
name of the executables resulting from the link of the main programs,
and for the Executable_Suffix.


File: gnat_ugn.info,  Node: Aggregate Library Projects,  Next: Project File Reference,  Prev: Aggregate Projects,  Up: GNAT Project Manager

5.8 Aggregate Library Projects
==============================

Aggregate library projects make it possible to build a single library
using object files built using other standard or library projects. This
gives the flexibility to describe an application as having multiple
modules (a GUI, database access, ...) using different project files (so
possibly built with different compiler options) and yet create a single
library (static or relocatable) out of the corresponding object files.

* Menu:

* Building aggregate library projects::
* Syntax of aggregate library projects::


File: gnat_ugn.info,  Node: Building aggregate library projects,  Next: Syntax of aggregate library projects,  Up: Aggregate Library Projects

5.8.1 Building aggregate library projects
-----------------------------------------

For example, we can define an aggregate project Agg that groups A, B
and C:

    aggregate library project Agg is
       for Project_Files use ("a.gpr", "b.gpr", "c.gpr");
       for Library_Name use ("agg");
       for Library_Dir use ("lagg");
    end Agg;

Then, when you build with:

    gprbuild agg.gpr

This will build all units from projects A, B and C and will create a
static library named `libagg.a' in the `lagg' directory. An aggregate
library project has the same set of restriction as a standard library
project.

Note that a shared aggregate library project cannot aggregate a static
library project. In platforms where a compiler option is required to
create relocatable object files, a Builder package in the aggregate
library project may be used:

    aggregate library project Agg is
       for Project_Files use ("a.gpr", "b.gpr", "c.gpr");
       for Library_Name use ("agg");
       for Library_Dir use ("lagg");
       for Library_Kind use "relocatable";

       package Builder is
          for Global_Compilation_Switches ("Ada") use ("-fPIC");
       end Builder;
    end Agg;

With the above aggregate library Builder package, the `-fPIC' option
will be passed to the compiler when building any source code from
projects `a.gpr', `b.gpr' and `c.gpr'.


File: gnat_ugn.info,  Node: Syntax of aggregate library projects,  Prev: Building aggregate library projects,  Up: Aggregate Library Projects

5.8.2 Syntax of aggregate library projects
------------------------------------------

An aggregate library project follows the general syntax of project
files. The recommended extension is still `.gpr'. However, a special
`aggregate library' qualifier must be put before the keyword `project'.

An aggregate library project cannot `with' any other project (standard
or aggregate), except an abstract project which can be used to share
attribute values.

An aggregate library project does not have any source files directly
(only through other standard projects). Therefore a number of the
standard attributes and packages are forbidden in an aggregate library
project. Here is the (non exhaustive) list:

   * Languages

   * Source_Files, Source_List_File and other attributes dealing with
     list of sources.

   * Source_Dirs, Exec_Dir and Object_Dir

   * Main

   * Roots

   * Externally_Built

   * Inherit_Source_Path

   * Excluded_Source_Dirs

   * Locally_Removed_Files

   * Excluded_Source_Files

   * Excluded_Source_List_File

   * Interfaces

The only package that is authorized (albeit optional) is Builder.

The Project_Files attribute (See *note Aggregate Projects: 171.) is
used to described the aggregated projects whose object files have to be
included into the aggregate library. The environment variables
`ADA_PROJECT_PATH', `GPR_PROJECT_PATH' and `GPR_PROJECT_PATH_FILE' are
not used to find the project files.


File: gnat_ugn.info,  Node: Project File Reference,  Prev: Aggregate Library Projects,  Up: GNAT Project Manager

5.9 Project File Reference
==========================

This section describes the syntactic structure of project files, the
various constructs that can be used. Finally, it ends with a summary of
all available attributes.

* Menu:

* Project Declaration::
* Qualified Projects::
* Declarations::
* Packages::
* Expressions::
* External Values::
* Typed String Declaration::
* Variables::
* Case Constructions::
* Attributes::


File: gnat_ugn.info,  Node: Project Declaration,  Next: Qualified Projects,  Up: Project File Reference

5.9.1 Project Declaration
-------------------------

Project files have an Ada-like syntax. The minimal project file is:

    project Empty is
    end Empty;

The identifier `Empty' is the name of the project.  This project name
must be present after the reserved word `end' at the end of the project
file, followed by a semi-colon.

`Identifiers' (i.e., the user-defined names such as project or variable
names) have the same syntax as Ada identifiers: they must start with a
letter, and be followed by zero or more letters, digits or underscore
characters; it is also illegal to have two underscores next to each
other. Identifiers are always case-insensitive ("Name" is the same as
"name").

    simple_name ::= identifier
    name        ::= simple_name { . simple_name }

`Strings' are used for values of attributes or as indexes for these
attributes. They are in general case sensitive, except when noted
otherwise (in particular, strings representing file names will be case
insensitive on some systems, so that "file.adb" and "File.adb" both
represent the same file).

`Reserved words' are the same as for standard Ada 95, and cannot be
used for identifiers. In particular, the following words are currently
used in project files, but others could be added later on. In bold are
the extra reserved words in project files: `all', `at', `case', `end',
`for', `is', `limited', `null', `others', `package', `renames', `type',
`use', `when', `with', `extends', `external', `project'.

`Comments' in project files have the same syntax as in Ada, two
consecutive hyphens through the end of the line.

A project may be an `independent project', entirely defined by a single
project file. Any source file in an independent project depends only on
the predefined library and other source files in the same project.  But
a project may also depend on other projects, either by importing them
through `with clauses', or by `extending' at most one other project.
Both types of dependency can be used in the same project.

A path name denotes a project file. It can be absolute or relative.  An
absolute path name includes a sequence of directories, in the syntax of
the host operating system, that identifies uniquely the project file in
the file system. A relative path name identifies the project file,
relative to the directory that contains the current project, or
relative to a directory listed in the environment variables
ADA_PROJECT_PATH and GPR_PROJECT_PATH. Path names are case sensitive if
file names in the host operating system are case sensitive. As a
special case, the directory separator can always be "/" even on Windows
systems, so that project files can be made portable across
architectures.  The syntax of the environment variables
ADA_PROJECT_PATH and GPR_PROJECT_PATH is a list of directory names
separated by colons on UNIX and semicolons on Windows.

A given project name can appear only once in a context clause.

It is illegal for a project imported by a context clause to refer,
directly or indirectly, to the project in which this context clause
appears (the dependency graph cannot contain cycles), except when one
of the with clauses in the cycle is a `limited with'.

    with "other_project.gpr";
    project My_Project extends "extended.gpr" is
    end My_Project;

These dependencies form a `directed graph', potentially cyclic when
using `limited with'. The subgraph reflecting the `extends' relations
is a tree.

A project's `immediate sources' are the source files directly defined by
that project, either implicitly by residing in the project source
directories, or explicitly through any of the source-related attributes.
More generally, a project's `sources' are the immediate sources of the
project together with the immediate sources (unless overridden) of any
project on which it depends directly or indirectly.

A `project hierarchy' can be created, where projects are children of
other projects. The name of such a child project must be `Parent.Child',
where `Parent' is the name of the parent project. In particular, this
makes all `with' clauses of the parent project automatically visible in
the child project.

    project        ::= context_clause project_declaration

    context_clause ::= {with_clause}
    with_clause    ::= *with* path_name { , path_name } ;
    path_name      ::= string_literal

    project_declaration ::= simple_project_declaration | project_extension
    simple_project_declaration ::=
      project <project_>name is
        {declarative_item}
      end <project_>simple_name;


File: gnat_ugn.info,  Node: Qualified Projects,  Next: Declarations,  Prev: Project Declaration,  Up: Project File Reference

5.9.2 Qualified Projects
------------------------

Before the reserved `project', there may be one or two `qualifiers',
that is identifiers or reserved words, to qualify the project.  The
current list of qualifiers is:

`abstract':
     Qualifies a project with no sources.  Such a   project must either
     have no declaration of attributes `Source_Dirs', `Source_Files',
     `Languages' or `Source_List_File', or one of `Source_Dirs',
     `Source_Files', or `Languages' must be declared as empty. If it
     extends another project, the project it extends must also be a
     qualified abstract project.

`standard':
     A standard project is a non library project with sources.  This is
     the default (implicit) qualifier.

`aggregate':
     A project whose sources are aggregated from other project files.

`aggregate library':
     A library whose sources are aggregated from other project or
     library project files.

`library':
     A library project must declare both attributes Library_Name` and
     `Library_Dir'.

`configuration':
     A configuration project cannot be in a project tree.  It describes
     compilers and other tools to `gprbuild'.


File: gnat_ugn.info,  Node: Declarations,  Next: Packages,  Prev: Qualified Projects,  Up: Project File Reference

5.9.3 Declarations
------------------

Declarations introduce new entities that denote types, variables,
attributes, and packages. Some declarations can only appear immediately
within a project declaration. Others can appear within a project or
within a package.

    declarative_item ::= simple_declarative_item
      | typed_string_declaration
      | package_declaration

    simple_declarative_item ::= variable_declaration
      | typed_variable_declaration
      | attribute_declaration
      | case_construction
      | empty_declaration

    empty_declaration ::= *null* ;

An empty declaration is allowed anywhere a declaration is allowed. It
has no effect.


File: gnat_ugn.info,  Node: Packages,  Next: Expressions,  Prev: Declarations,  Up: Project File Reference

5.9.4 Packages
--------------

A project file may contain `packages', that group attributes (typically
all the attributes that are used by one of the GNAT tools).

A package with a given name may only appear once in a project file.
The following packages are currently supported in project files (See
*note Attributes: 155. for the list of attributes that each can
contain).

`Binder'
     This package specifies characteristics useful when invoking the
     binder either directly via the `gnat' driver or when using
     `gprbuild'.  See *note Main Subprograms: 160.

`Builder'
     This package specifies the compilation options used when building
     an executable or a library for a project. Most of the options
     should be set in one of `Compiler', `Binder' or `Linker' packages,
     but there are some general options that should be defined in this
     package. See *note Main Subprograms: 160, and *note Executable
     File Names: 165. in particular.

`Clean'
     This package specifies the options used when cleaning a project or
     a project tree using the tools `gnatclean' or `gprclean'.

`Compiler'
     This package specifies the compilation options used by the
     compiler for each languages. See *note Tools Options in Project
     Files: 161.

`Cross_Reference'
     This package specifies the options used when calling the library
     tool `gnatxref' via the `gnat' driver. Its attributes
     `Default_Switches' and `Switches' have the same semantics as for
     the package `Builder'.

`Finder'
     This package specifies the options used when calling the search
     tool `gnatfind' via the `gnat' driver. Its attributes
     `Default_Switches' and `Switches' have the same semantics as for
     the package `Builder'.

`Gnatls'
     This package specifies the options to use when invoking `gnatls'
     via the `gnat' driver.

`IDE'
     This package specifies the options used when starting an integrated
     development environment, for instance `GPS' or `Gnatbench'.

`Install'
     This package specifies the options used when installing a project
     with `gprinstall'. See *note Installation: 16b.

`Linker'
     This package specifies the options used by the linker.  See *note
     Main Subprograms: 160.

`Naming'
          This package specifies the naming conventions that apply to
          the source files in a project. In particular, these
          conventions are used to automatically find all source files
          in the source directories, or given a file name to find out
          its language for proper processing.  See *note Naming
          Schemes: 14e.

`Remote'
     This package is used by `gprbuild' to describe how distributed
     compilation should be done.

`Stack'
     This package specifies the options used when calling the tool
     `gnatstack' via the `gnat' driver. Its attributes
     `Default_Switches' and `Switches' have the same semantics as for
     the package `Builder'.

`Synchronize'
     This package specifies the options used when calling the tool
     `gnatsync' via the `gnat' driver.

In its simplest form, a package may be empty:

    project Simple is
      package Builder is
      end Builder;
    end Simple;

A package may contain `attribute declarations', `variable declarations'
and `case constructions', as will be described below.

When there is ambiguity between a project name and a package name, the
name always designates the project. To avoid possible confusion, it is
always a good idea to avoid naming a project with one of the names
allowed for packages or any name that starts with `gnat'.

A package can also be defined by a `renaming declaration'. The new
package renames a package declared in a different project file, and has
the same attributes as the package it renames. The name of the renamed
package must be the same as the name of the renaming package. The
project must contain a package declaration with this name, and the
project must appear in the context clause of the current project, or be
its parent project. It is not possible to add or override attributes to
the renaming project. If you need to do so, you should use an
`extending declaration' (see below).

Packages that are renamed in other project files often come from
project files that have no sources: they are just used as templates.
Any modification in the template will be reflected automatically in all
the project files that rename a package from the template. This is a
very common way to share settings between projects.

Finally, a package can also be defined by an `extending declaration'.
This is similar to a `renaming declaration', except that it is possible
to add or override attributes.

    package_declaration ::= package_spec | package_renaming | package_extension
    package_spec ::=
      package <package_>simple_name is
        {simple_declarative_item}
      end package_identifier ;
    package_renaming ::==
      package <package_>simple_name renames <project_>simple_name.package_identifier ;
    package_extension ::==
      package <package_>simple_name extends <project_>simple_name.package_identifier is
        {simple_declarative_item}
      end package_identifier ;


File: gnat_ugn.info,  Node: Expressions,  Next: External Values,  Prev: Packages,  Up: Project File Reference

5.9.5 Expressions
-----------------

An expression is any value that can be assigned to an attribute or a
variable. It is either a literal value, or a construct requiring runtime
computation by the project manager. In a project file, the computed
value of an expression is either a string or a list of strings.

A string value is one of:

   * A literal string, for instance `"comm/my_proj.gpr"'

   * The name of a variable that evaluates to a string (see *note
     Variables: 158.)

   * The name of an attribute that evaluates to a string (see *note
     Attributes: 155.)

   * An external reference (see *note External Values: 157.)

   * A concatenation of the above, as in `"prefix_" & Var'.

A list of strings is one of the following:

   * A parenthesized comma-separated list of zero or more string
     expressions, for instance `(File_Name, "gnat.adc", File_Name &
     ".orig")' or `()'.

   * The name of a variable that evaluates to a list of strings

   * The name of an attribute that evaluates to a list of strings

   * A concatenation of a list of strings and a string (as defined
     above), for instance `("A", "B") & "C"'

   * A concatenation of two lists of strings

The following is the grammar for expressions

    string_literal ::= "{string_element}"  --  Same as Ada
    string_expression ::= string_literal
        | *variable_*name
        | external_value
        | attribute_reference
        | ( string_expression { & string_expression } )
    string_list  ::= ( string_expression { , string_expression } )
       | *string_variable*_name
       | *string_*attribute_reference
    term ::= string_expression | string_list
    expression ::= term { & term }     --  Concatenation

Concatenation involves strings and list of strings. As soon as a list of
strings is involved, the result of the concatenation is a list of
strings. The following Ada declarations show the existing operators:

    function "&" (X : String;      Y : String)      return String;
    function "&" (X : String_List; Y : String)      return String_List;
    function "&" (X : String_List; Y : String_List) return String_List;

Here are some specific examples:

    List := () & File_Name; --  One string in this list
    List2 := List & (File_Name & ".orig"); -- Two strings
    Big_List := List & Lists2;  --  Three strings
    Illegal := "gnat.adc" & List2;  --  Illegal, must start with list


File: gnat_ugn.info,  Node: External Values,  Next: Typed String Declaration,  Prev: Expressions,  Up: Project File Reference

5.9.6 External Values
---------------------

An external value is an expression whose value is obtained from the
command that invoked the processing of the current project file
(typically a `gprbuild' command).

There are two kinds of external values, one that returns a single
string, and one that returns a string list.

The syntax of a single string external value is:

    external_value ::= *external* ( string_literal [, string_literal] )

The first string_literal is the string to be used on the command line or
in the environment to specify the external value. The second
string_literal, if present, is the default to use if there is no
specification for this external value either on the command line or in
the environment.

Typically, the external value will either exist in the environment
variables or be specified on the command line through the
`-X`vbl'=`value'' switch. If both are specified, then the command line
value is used, so that a user can more easily override the value.

The function `external' always returns a string. It is an error if the
value was not found in the environment and no default was specified in
the call to `external'.

An external reference may be part of a string expression or of a string
list expression, and can therefore appear in a variable declaration or
an attribute declaration.

Most of the time, this construct is used to initialize typed variables,
which are then used in `case' constructions to control the value
assigned to attributes in various scenarios. Thus such variables are
often called `scenario variables'.

The syntax for a string list external value is:

    external_value ::= *external_as_list* ( string_literal , string_literal )

The first string_literal is the string to be used on the command line or
in the environment to specify the external value. The second
string_literal is the separator between each component of the string
list.

If the external value does not exist in the environment or on the
command line, the result is an empty list. This is also the case, if
the separator is an empty string or if the external value is only one
separator.

Any separator at the beginning or at the end of the external value is
discarded. Then, if there is no separator in the external value, the
result is a string list with only one string. Otherwise, any string
between the beginning and the first separator, between two consecutive
separators and between the last separator and the end are components of
the string list.

    *external_as_list* ("SWITCHES", ",")

If the external value is "-O2,-g", the result is ("-O2", "-g").

If the external value is ",-O2,-g,", the result is also ("-O2", "-g").

if the external value is "-gnatv", the result is ("-gnatv").

If the external value is ",,", the result is ("").

If the external value is ",", the result is (), the empty string list.


File: gnat_ugn.info,  Node: Typed String Declaration,  Next: Variables,  Prev: External Values,  Up: Project File Reference

5.9.7 Typed String Declaration
------------------------------

A `type declaration' introduces a discrete set of string literals.  If
a string variable is declared to have this type, its value is
restricted to the given set of literals. These are the only named types
in project files. A string type may only be declared at the project
level, not inside a package.

    typed_string_declaration ::=
      *type* *<typed_string_>*_simple_name *is* ( string_literal {, string_literal} );

The string literals in the list are case sensitive and must all be
different.  They may include any graphic characters allowed in Ada,
including spaces.  Here is an example of a string type declaration:

    type OS is ("NT", "nt", "Unix", "GNU/Linux", "other OS");

Variables of a string type are called `typed variables'; all other
variables are called `untyped variables'. Typed variables are
particularly useful in `case' constructions, to support conditional
attribute declarations. (See *note Case Constructions: 1a3.).

A string type may be referenced by its name if it has been declared in
the same project file, or by an expanded name whose prefix is the name
of the project in which it is declared.


File: gnat_ugn.info,  Node: Variables,  Next: Case Constructions,  Prev: Typed String Declaration,  Up: Project File Reference

5.9.8 Variables
---------------

`Variables' store values (strings or list of strings) and can appear as
part of an expression. The declaration of a variable creates the
variable and assigns the value of the expression to it. The name of the
variable is available immediately after the assignment symbol, if you
need to reuse its old value to compute the new value. Before the
completion of its first declaration, the value of a variable defaults
to the empty string ("").

A `typed' variable can be used as part of a `case' expression to
compute the value, but it can only be declared once in the project file,
so that all case constructions see the same value for the variable. This
provides more consistency and makes the project easier to understand.
The syntax for its declaration is identical to the Ada syntax for an
object declaration. In effect, a typed variable acts as a constant.

An `untyped' variable can be declared and overridden multiple times
within the same project. It is declared implicitly through an Ada
assignment. The first declaration establishes the kind of the variable
(string or list of strings) and successive declarations must respect
the initial kind. Assignments are executed in the order in which they
appear, so the new value replaces the old one and any subsequent
reference to the variable uses the new value.

A variable may be declared at the project file level, or within a
package.

    typed_variable_declaration ::=
      *<typed_variable_>*simple_name : *<typed_string_>*name := string_expression;

    variable_declaration ::= *<variable_>*simple_name := expression;

Here are some examples of variable declarations:

    This_OS : OS := external ("OS"); --  a typed variable declaration
    That_OS := "GNU/Linux";          --  an untyped variable declaration

    Name      := "readme.txt";
    Save_Name := Name & ".saved";

    Empty_List := ();
    List_With_One_Element := ("-gnaty");
    List_With_Two_Elements := List_With_One_Element & "-gnatg";
    Long_List := ("main.ada", "pack1_.ada", "pack1.ada", "pack2_.ada");

A `variable reference' may take several forms:

   * The simple variable name, for a variable in the current package
     (if any) or in the current project

   * An expanded name, whose prefix is a context name.

A `context' may be one of the following:

   * The name of an existing package in the current project

   * The name of an imported project of the current project

   * The name of an ancestor project (i.e., a project extended by the
     current project, either directly or indirectly)

   * An expanded name whose prefix is an imported/parent project name,
     and whose selector is a package name in that project.


File: gnat_ugn.info,  Node: Case Constructions,  Next: Attributes,  Prev: Variables,  Up: Project File Reference

5.9.9 Case Constructions
------------------------

A `case' construction is used in a project file to effect conditional
behavior. Through this construction, you can set the value of attributes
and variables depending on the value previously assigned to a typed
variable.

All choices in a choice list must be distinct. Unlike Ada, the choice
lists of all alternatives do not need to include all values of the type.
An `others' choice must appear last in the list of alternatives.

The syntax of a `case' construction is based on the Ada case
construction (although the `null' declaration for empty alternatives is
optional).

The case expression must be a string variable, either typed or not,
whose value is often given by an external reference (see *note External
Values: 157.).

Each alternative starts with the reserved word `when', either a list of
literal strings separated by the `"|"' character or the reserved word
`others', and the `"=>"' token.  When the case expression is a typed
string variable, each literal string must belong to the string type
that is the type of the case variable.  After each `=>', there are zero
or more declarations.  The only declarations allowed in a case
construction are other case constructions, attribute declarations and
variable declarations. String type declarations and package
declarations are not allowed. Variable declarations are restricted to
variables that have already been declared before the case construction.

    case_construction ::=
      *case* *<variable_>*name *is* {case_item} *end case* ;

    case_item ::=
      *when* discrete_choice_list =>
        {case_declaration
          | attribute_declaration
          | variable_declaration
          | empty_declaration}

    discrete_choice_list ::= string_literal {| string_literal} | *others*

Here is a typical example, with a typed string variable:

    project MyProj is
       type OS_Type is ("GNU/Linux", "Unix", "NT", "VMS");
       OS : OS_Type := external ("OS", "GNU/Linux");

       package Compiler is
         case OS is
           when "GNU/Linux" | "Unix" =>
             for Switches ("Ada")
                 use ("-gnath");
           when "NT" =>
             for Switches ("Ada")
                 use ("-gnatP");
           when others =>
             null;
         end case;
       end Compiler;
    end MyProj;


File: gnat_ugn.info,  Node: Attributes,  Prev: Case Constructions,  Up: Project File Reference

5.9.10 Attributes
-----------------

A project (and its packages) may have `attributes' that define the
project's properties.  Some attributes have values that are strings;
others have values that are string lists.

    attribute_declaration ::=
       simple_attribute_declaration | indexed_attribute_declaration

    simple_attribute_declaration ::= *for* attribute_designator *use* expression ;

    indexed_attribute_declaration ::=
      *for* *<indexed_attribute_>*simple_name ( string_literal) *use* expression ;

    attribute_designator ::=
      *<simple_attribute_>*simple_name
      | *<indexed_attribute_>*simple_name ( string_literal )

There are two categories of attributes: `simple attributes' and
`indexed attributes'.  Each simple attribute has a default value: the
empty string (for string attributes) and the empty list (for string
list attributes).  An attribute declaration defines a new value for an
attribute, and overrides the previous value. The syntax of a simple
attribute declaration is similar to that of an attribute definition
clause in Ada.

Some attributes are indexed. These attributes are mappings whose domain
is a set of strings. They are declared one association at a time, by
specifying a point in the domain and the corresponding image of the
attribute.  Like untyped variables and simple attributes, indexed
attributes may be declared several times. Each declaration supplies a
new value for the attribute, and replaces the previous setting.

Here are some examples of attribute declarations:

    --  simple attributes
    for Object_Dir use "objects";
    for Source_Dirs use ("units", "test/drivers");

    --  indexed attributes
    for Body ("main") use "Main.ada";
    for Switches ("main.ada")
        use ("-v", "-gnatv");
    for Switches ("main.ada") use Builder'Switches ("main.ada") & "-g";

    --  indexed attributes copy (from package Builder in project Default)
    --  The package name must always be specified, even if it is the current
    --  package.
    for Default_Switches use Default.Builder'Default_Switches;

Attributes references may appear anywhere in expressions, and are used
to retrieve the value previously assigned to the attribute. If an
attribute has not been set in a given package or project, its value
defaults to the empty string or the empty list, with some exceptions.

    attribute_reference ::=
      attribute_prefix ' *<simple_attribute>_*simple_name [ (string_literal) ]
    attribute_prefix ::= *project*
      | *<project_>*simple_name
      | package_identifier
      | *<project_>*simple_name . package_identifier

Examples are:

    <project>'Object_Dir
    Naming'Dot_Replacement
    Imported_Project'Source_Dirs
    Imported_Project.Naming'Casing
    Builder'Default_Switches ("Ada")

The exceptions to the empty defaults are:

   * Object_Dir: default is "."

   * Exec_Dir: default is 'Object_Dir, that is the value of attribute
     Object_Dir in the same project, declared or defaulted.

   * Source_Dirs: default is (".")

The prefix of an attribute may be:

   * `project' for an attribute of the current project

   * The name of an existing package of the current project

   * The name of an imported project

   * The name of a parent project that is extended by the current
     project

   * An expanded name whose prefix is imported/parent project name, and
     whose selector is a package name

In the following sections, all predefined attributes are succinctly
described, first the project level attributes, that is those attributes
that are not in a package, then the attributes in the different
packages.

It is possible for different tools to dynamically create new packages
with attributes, or new attributes in predefined packages. These
attributes are not documented here.

The attributes under Configuration headings are usually found only in
configuration project files.

The characteristics of each attribute are indicated as follows:

   * `Type of value'

     The value of an attribute may be a single string, indicated by the
     word "single", or a string list, indicated by the word "list".

   * `Read-only'

     When the attribute is read-only, that is when it is not allowed to
     declare the attribute, this is indicated by the words "read-only".

   * `Optional index'

     If it is allowed in the value of the attribute (both single and
     list) to have an optional index, this is indicated by the words
     "optional index".

   * `Indexed attribute'

     When it is an indexed attribute, this is indicated by the word
     "indexed".

   * `Case-sensitivity of the index'

     For an indexed attribute, if the index is case-insensitive, this
     is indicated by the words "case-insensitive index".

   * `File name index'

     For an indexed attribute, when the index is a file name, this is
     indicated by the words "file name index". The index may or may not
     be case-sensitive, depending on the platform.

   * `others allowed in index'

     For an indexed attribute, if it is allowed to use `others' as the
     index, this is indicated by the words "others allowed".

     When `others' is used as the index of an indexed attribute, the
     value of the attribute indexed by `others' is used when no other
     index would apply.

* Menu:

* Project Level Attributes::
* Package Binder Attributes::
* Package Builder Attributes::
* Package Clean Attributes::
* Package Compiler Attributes::
* Package Cross_Reference Attributes::
* Package Finder Attributes::
* Package gnatls Attributes::
* Package IDE Attributes::
* Package Install Attributes::
* Package Linker Attributes::
* Package Naming Attributes::
* Package Remote Attributes::
* Package Stack Attributes::
* Package Synchronize Attributes::


File: gnat_ugn.info,  Node: Project Level Attributes,  Next: Package Binder Attributes,  Up: Attributes

5.9.10.1 Project Level Attributes
.................................

   * `General'

        * `Name': single, read-only

          The name of the project.

        * `Project_Dir': single, read-only

          The path name of the project directory.

        * `Main': list, optional index

          The list of main sources for the executables.

        * `Languages': list

          The list of languages of the sources of the project.

        * `Roots': list, indexed, file name index

          The index is the file name of an executable source. Indicates
          the list of units from the main project that need to be bound
          and linked with their closures with the executable. The index
          is either a file name, a language name or "*".  The roots for
          an executable source are those in `Roots' with an index that
          is the executable source file name, if declared. Otherwise,
          they are those in `Roots' with an index that is the language
          name of the executable source, if present. Otherwise, they
          are those in `Roots ("*")', if declared. If none of these
          three possibilities are declared, then there are no roots for
          the executable source.

        * `Externally_Built': single

          Indicates if the project is externally built.  Only
          case-insensitive values allowed are "true" and "false", the
          default.

   * `Directories'

        * `Object_Dir': single

          Indicates the object directory for the project.

        * `Exec_Dir': single

          Indicates the exec directory for the project, that is the
          directory where the executables are.

        * `Source_Dirs': list

          The list of source directories of the project.

        * `Inherit_Source_Path': list, indexed, case-insensitive index

          Index is a language name. Value is a list of language names.
          Indicates that in the source search path of the index
          language the source directories of the languages in the list
          should be included.

          Example:

              for Inherit_Source_Path ("C++") use ("C");

        * `Exclude_Source_Dirs': list

          The list of directories that are included in Source_Dirs but
          are not source directories of the project.

        * `Ignore_Source_Sub_Dirs': list

          Value is a list of simple names for subdirectories that are
          removed from the list of source directories, including theur
          subdirectories.

   * `Source Files'

        * `Source_Files': list

          Value is a list of source file simple names.

        * `Locally_Removed_Files': list

          Obsolescent. Equivalent to Excluded_Source_Files.

        * `Excluded_Source_Files': list

          Value is a list of simple file names that are not sources of
          the project.  Allows to remove sources that are inherited or
          found in the source directories and that match the naming
          scheme.

        * `Source_List_File': single

          Value is a text file name that contains a list of source file
          simple names, one on each line.

        * `Excluded_Source_List_File': single

          Value is a text file name that contains a list of file simple
          names that are not sources of the project.

        * `Interfaces': list

          Value is a list of file names that constitutes the interfaces
          of the project.

   * `Aggregate Projects'

        * `Project_Files': list

          Value is the list of aggregated projects.

        * `Project_Path': list

          Value is a list of directories that are added to the project
          search path when looking for the aggregated projects.

        * `External': single, indexed

          Index is the name of an external reference. Value is the
          value of the external reference to be used when parsing the
          aggregated projects.

   * `Libraries'

        * `Library_Dir': single

          Value is the name of the library directory. This attribute
          needs to be declared for each library project.

        * `Library_Name': single

          Value is the name of the library. This attribute needs to be
          declared or inherited for each library project.

        * `Library_Kind': single

          Specifies the kind of library: static library (archive) or
          shared library.  Case-insensitive values must be one of
          "static" for archives (the default) or "dynamic" or
          "relocatable" for shared libraries.

        * `Library_Version': single

          Value is the name of the library file.

        * `Library_Interface': list

          Value is the list of unit names that constitutes the
          interfaces of a Stand-Alone Library project.

        * `Library_Standalone': single

          Specifies if a Stand-Alone Library (SAL) is encapsulated or
          not.  Only authorized case-insensitive values are "standard"
          for non encapsulated SALs, "encapsulated" for encapsulated
          SALs or "no" for non SAL library project.

        * `Library_Encapsulated_Options': list

          Value is a list of options that need to be used when linking
          an encapsulated Stand-Alone Library.

        * `Library_Encapsulated_Supported': single

          Indicates if encapsulated Stand-Alone Libraries are
          supported. Only authorized case-insensitive values are "true"
          and "false" (the default).

        * `Library_Auto_Init': single

          Indicates if a Stand-Alone Library is auto-initialized. Only
          authorized case-insentive values are "true" and "false".

        * `Leading_Library_Options': list

          Value is a list of options that are to be used at the
          beginning of the command line when linking a shared library.

        * `Library_Options': list

          Value is a list of options that are to be used when linking a
          shared library.

        * `Library_Rpath_Options': list, indexed, case-insensitive index

          Index is a language name. Value is a list of options for an
          invocation of the compiler of the language. This invocation
          is done for a shared library project with sources of the
          language. The output of the invocation is the path name of a
          shared library file. The directory name is to be put in the
          run path option switch when linking the shared library for
          the project.

        * `Library_Src_Dir': single

          Value is the name of the directory where copies of the
          sources of the interfaces of a Stand-Alone Library are to be
          copied.

        * `Library_ALI_Dir': single

          Value is the name of the directory where the ALI files of the
          interfaces of a Stand-Alone Library are to be copied. When
          this attribute is not declared, the directory is the library
          directory.

        * `Library_gcc': single

          Obsolescent attribute. Specify the linker driver used to link
          a shared library.  Use instead attribute Linker'Driver.

        * `Library_Symbol_File': single

          Value is the name of the library symbol file.

        * `Library_Symbol_Policy': single

          Indicates the symbol policy kind. Only authorized
          case-insensitive values are "autonomous", "default",
          "compliant", "controlled" or "direct".

        * `Library_Reference_Symbol_File': single

          Value is the name of the reference symbol file.

   * `Configuration - General'

        * `Default_Language': single

          Value is the case-insensitive name of the language of a
          project when attribute Languages is not specified.

        * `Run_Path_Option': list

          Value is the list of switches to be used when specifying the
          run path option in an executable.

        * `Run_Path_Origin': single

          Value is the the string that may replace the path name of the
          executable directory in the run path options.

        * `Separate_Run_Path_Options': single

          Indicates if there may be several run path options specified
          when linking an executable. Only authorized case-insensitive
          values are "true" or "false" (the default).

        * `Toolchain_Version': single, indexed, case-insensitive index

          Index is a language name. Specify the version of a toolchain
          for a language.

        * `Toolchain_Description': single, indexed, case-insensitive
          index

          Obsolescent. No longer used.

        * `Object_Generated': single, indexed, case-insensitive index

          Index is a language name. Indicates if invoking the compiler
          for a language produces an object file. Only authorized
          case-insensitive values are "false" and "true" (the default).

        * `Objects_Linked': single, indexed, case-insensitive index

          Index is a language name. Indicates if the object files
          created by the compiler for a language need to be linked in
          the executable. Only authorized case-insensitive values are
          "false" and "true" (the default).

        * `Target': single

          Value is the name of the target platform. Taken into account
          only in the main project.

          Note that when the target is specified on the command line
          (usually with a switch -target=), the value of attribute
          reference 'Target is the one specified on the command line.

        * `Runtime': single, indexed, case-insensitive index

          Index is a language name. Indicates the runtime directory
          that is to be used when using the compiler of the language.
          Taken into account only in the main project.

          Note that when the runtime is specified for a language on the
          command line (usually with a switch -RTS), the value of
          attribute reference 'Runtime for this language is the one
          specified on the command line.

   * `Configuration - Libraries'

        * `Library_Builder': single

          Value is the path name of the application that is to be used
          to build libraries. Usually the path name of "gprlib".

        * `Library_Support': single

          Indicates the level of support of libraries. Only authorized
          case-insensitive values are "static_only", "full" or "none"
          (the default).

   * `Configuration - Archives'

        * `Archive_Builder': list

          Value is the name of the application to be used to create a
          static library (archive), followed by the options to be used.

        * `Archive_Builder_Append_Option': list

          Value is the list of options to be used when invoking the
          archive builder to add project files into an archive.

        * `Archive_Indexer': list

          Value is the name of the archive indexer, followed by the
          required options.

        * `Archive_Suffix': single

          Value is the extension of archives. When not declared, the
          extension is ".a".

        * `Library_Partial_Linker': list

          Value is the name of the partial linker executable, followed
          by the required options.

   * `Configuration - Shared Libraries'

        * `Shared_Library_Prefix': single

          Value is the prefix in the name of shared library files. When
          not declared, the prefix is "lib".

        * `Shared_Library_Suffix': single

          Value is the the extension of the name of shared library
          files. When not declared, the extension is ".so".

        * `Symbolic_Link_Supported': single

          Indicates if symbolic links are supported on the platform.
          Only authorized case-insensitive values are "true" and
          "false" (the default).

        * `Library_Major_Minor_Id_Supported': single

          Indicates if major and minor ids for shared library names are
          supported on the platform. Only authorized case-insensitive
          values are "true" and "false" (the default).

        * `Library_Auto_Init_Supported': single

          Indicates if auto-initialization of Stand-Alone Libraries is
          supported. Only authorized case-insensitive values are "true"
          and "false" (the default).

        * `Shared_Library_Minimum_Switches': list

          Value is the list of required switches when linking a shared
          library.

        * `Library_Version_Switches': list

          Value is the list of switches to specify a internal name for
          a shared library.

        * `Library_Install_Name_Option': single

          Value is the name of the option that needs to be used,
          concatenated with the path name of the library file, when
          linking a shared library.

        * `Runtime_Library_Dir': single, indexed, case-insensitive index

          Index is a language name. Value is the path name of the
          directory where the runtime libraries are located.

        * `Runtime_Source_Dir': single, indexed, case-insensitive index

          Index is a language name. Value is the path name of the
          directory where the sources of runtime libraries are located.


File: gnat_ugn.info,  Node: Package Binder Attributes,  Next: Package Builder Attributes,  Prev: Project Level Attributes,  Up: Attributes

5.9.10.2 Package Binder Attributes
..................................

   * `General'

        * `Default_Switches': list, indexed, case-insensitive index

          Index is a language name. Value is the list of switches to be
          used when binding code of the language, if there is no
          applicable attribute Switches.

        * `Switches': list, optional index, indexed, case-insensitive
          index, others allowed

          Index is either a language name or a source file name. Value
          is the list of switches to be used when binding code. Index
          is either the source file name of the executable to be bound
          or the language name of the code to be bound.

   * `Configuration - Binding'

        * `Driver': single, indexed, case-insensitive index

          Index is a language name. Value is the name of the
          application to be used when binding code of the language.

        * `Required_Switches': list, indexed, case-insensitive index

          Index is a language name. Value is the list of the required
          switches to be used when binding code of the language.

        * `Prefix': single, indexed, case-insensitive index

          Index is a language name. Value is a prefix to be used for
          the binder exchange file name for the language. Used to have
          different binder exchange file names when binding different
          languages.

        * `Objects_Path': single,indexed, case-insensitive index

          Index is a language name. Value is the name of the
          environment variable that contains the path for the object
          directories.

        * `Object_Path_File': single,indexed, case-insensitive index

          Index is a language name. Value is the name of the
          environment variable. The value of the environment variable
          is the path name of a text file that contains the list of
          object directories.


File: gnat_ugn.info,  Node: Package Builder Attributes,  Next: Package Clean Attributes,  Prev: Package Binder Attributes,  Up: Attributes

5.9.10.3 Package Builder Attributes
...................................

   * `Default_Switches': list, indexed, case-insensitive index

     Index is a language name. Value is the list of builder switches to
     be used when building an executable of the language, if there is
     no applicable attribute Switches.

   * `Switches': list, optional index, indexed, case-insensitive index,
     others allowed

     Index is either a language name or a source file name. Value is
     the list of builder switches to be used when building an
     executable. Index is either the source file name of the executable
     to be built or its language name.

   * `Global_Compilation_Switches': list, optional index, indexed,
     case-insensitive index

     Index is either a language name or a source file name. Value is
     the list of compilation switches to be used when building an
     executable. Index is either the source file name of the executable
     to be built or its language name.

   * `Executable': single, indexed, case-insensitive index

     Index is an executable source file name. Value is the simple file
     name of the executable to be built.

   * `Executable_Suffix': single

     Value is the extension of the file names of executable. When not
     specified, the extension is the default extension of executables
     on the platform.

   * `Global_Configuration_Pragmas': single

     Value is the file name of a configuration pragmas file that is
     specified to the Ada compiler when compiling any Ada source in the
     project tree.

   * `Global_Config_File': single, indexed, case-insensitive index

     Index is a language name. Value is the file name of a
     configuration file that is specified to the compiler when
     compiling any source of the language in the project tree.


File: gnat_ugn.info,  Node: Package Clean Attributes,  Next: Package Compiler Attributes,  Prev: Package Builder Attributes,  Up: Attributes

5.9.10.4 Package Clean Attributes
.................................

   * `Switches': list

     Value is a list of switches to be used by the cleaning application.

   * `Source_Artifact_Extensions': list, indexed, case-insensitive index

     Index is a language names. Value is the list of extensions for
     file names derived from object file names that need to be cleaned
     in the object directory of the project.

   * `Object_Artifact_Extensions': list, indexed, case-insensitive index

     Index is a language names. Value is the list of extensions for
     file names derived from source file names that need to be cleaned
     in the object directory of the project.

   * `Artifacts_In_Object_Dir': single

     Value is a list of file names expressed as regular expressions
     that are to be deleted by gprclean in the object directory of the
     project.

   * `Artifacts_In_Exec_Dir': single

     Value is list of file names expressed as regular expressions that
     are to be deleted by gprclean in the exec directory of the main
     project.


File: gnat_ugn.info,  Node: Package Compiler Attributes,  Next: Package Cross_Reference Attributes,  Prev: Package Clean Attributes,  Up: Attributes

5.9.10.5 Package Compiler Attributes
....................................

   * `General'

        * `Default_Switches': list, indexed, case-insensitive index

          Index is a language name. Value is a list of switches to be
          used when invoking the compiler for the language for a source
          of the project, if there is no applicable attribute Switches.

        * `Switches': list, optional index, indexed, case-insensitive
          index, others allowed

          Index is a source file name or a language name. Value is the
          list of switches to be used when invoking the compiler for
          the source or for its language.

        * `Local_Configuration_Pragmas': single

          Value is the file name of a configuration pragmas file that
          is specified to the Ada compiler when compiling any Ada
          source in the project.

        * `Local_Config_File': single, indexed, case-insensitive index

          Index is a language name. Value is the file name of a
          configuration file that is specified to the compiler when
          compiling any source of the language in the project.

   * `Configuration - Compiling'

        * `Driver': single, indexed, case-insensitive index

          Index is a language name. Value is the name of the executable
          for the compiler of the language.

        * `Language_Kind': single, indexed, case-insensitive index

          Index is a language name. Indicates the kind of the language,
          either file based or unit based. Only authorized
          case-insensitive values are "unit_based" and "file_based"
          (the default).

        * `Dependency_Kind': single, indexed, case-insensitive index

          Index is a language name. Indicates how the dependencies are
          handled for the language. Only authorized case-insensitive
          values are "makefile", "ali_file", "ali_closure" or "none"
          (the default).

        * `Required_Switches': list, indexed, case-insensitive index

          Equivalent to attribute Leading_Required_Switches.

        * `Leading_Required_Switches': list, indexed, case-insensitive
          index

          Index is a language name. Value is the list of the minimum
          switches to be used at the beginning of the command line when
          invoking the compiler for the language.

        * `Trailing_Required_Switches': list, indexed, case-insensitive
          index

          Index is a language name. Value is the list of the minimum
          switches to be used at the end of the command line when
          invoking the compiler for the language.

        * `PIC_Option': list, indexed, case-insensitive index

          Index is a language name. Value is the list of switches to be
          used when compiling a source of the language when the project
          is a shared library project.

        * `Path_Syntax': single, indexed, case-insensitive index

          Index is a language name. Value is the kind of path syntax to
          be used when invoking the compiler for the language. Only
          authorized case-insensitive values are "canonical" and "host"
          (the default).

        * `Source_File_Switches': single, indexed, case-insensitive
          index

          Index is a language name. Value is a list of switches to be
          used just before the path name of the source to compile when
          invoking the compiler for a source of the language.

        * `Object_File_Suffix': single, indexed, case-insensitive index

          Index is a language name. Value is the extension of the
          object files created by the compiler of the language. When
          not specified, the extension is the default one for the
          platform.

        * `Object_File_Switches': list, indexed, case-insensitive index

          Index is a language name. Value is the list of switches to be
          used by the compiler of the language to specify the path name
          of the object file. When not specified, the switch used is
          "-o".

        * `Multi_Unit_Switches': list, indexed, case-insensitive index

          Index is a language name. Value is the list of switches to be
          used to compile a unit in a multi unit source of the
          language. The index of the unit in the source is concatenated
          with the last switches in the list.

        * `Multi_Unit_Object_Separator': single, indexed,
          case-insensitive index

          Index is a language name. Value is the string to be used in
          the object file name before the index of the unit, when
          compiling a unit in a multi unit source of the language.

   * `Configuration - Mapping Files'

        * `Mapping_File_Switches': list, indexed, case-insensitive index

          Index is a language name. Value is the list of switches to be
          used to specify a mapping file when invoking the compiler for
          a source of the language.

        * `Mapping_Spec_Suffix': single, indexed, case-insensitive index

          Index is a language name. Value is the suffix to be used in a
          mapping file to indicate that the source is a spec.

        * `Mapping_Body_Suffix': single, indexed, case-insensitive index

          Index is a language name. Value is the suffix to be used in a
          mapping file to indicate that the source is a body.

   * `Configuration - Config Files'

        * `Config_File_Switches': list: single, indexed,
          case-insensitive index

          Index is a language name. Value is the list of switches to
          specify to the compiler of the language a configuration file.

        * `Config_Body_File_Name': single, indexed, case-insensitive
          index

          Index is a language name. Value is the template to be used to
          indicate a configuration specific to a body of the language
          in a configuration file.

        * `Config_Body_File_Name_Index': single, indexed,
          case-insensitive index

          Index is a language name. Value is the template to be used to
          indicate a configuration specific to the body a unit in a
          multi unit source of the language in a configuration file.

        * `Config_Body_File_Name_Pattern': single, indexed,
          case-insensitive index

          Index is a language name. Value is the template to be used to
          indicate a configuration for all bodies of the languages in a
          configuration file.

        * `Config_Spec_File_Name': single, indexed, case-insensitive
          index

          Index is a language name. Value is the template to be used to
          indicate a configuration specific to a spec of the language
          in a configuration file.

        * `Config_Spec_File_Name_Index': single, indexed,
          case-insensitive index

          Index is a language name. Value is the template to be used to
          indicate a configuration specific to the spec a unit in a
          multi unit source of the language in a configuration file.

        * `Config_Spec_File_Name_Pattern': single, indexed,
          case-insensitive index

          Index is a language name. Value is the template to be used to
          indicate a configuration for all specs of the languages in a
          configuration file.

        * `Config_File_Unique': single, indexed, case-insensitive index

          Index is a language name. Indicates if there should be only
          one configuration file specified to the compiler of the
          language. Only authorized case-insensitive values are "true"
          and "false" (the default).

   * `Configuration - Dependencies'

        * `Dependency_Switches': list, indexed, case-insensitive index

          Index is a language name. Value is the list of switches to be
          used to specify to the compiler the dependency file when the
          dependency kind of the language is file based, and when
          Dependency_Driver is not specified for the language.

        * `Dependency_Driver': list, indexed, case-insensitive index

          Index is a language name. Value is the name of the executable
          to be used to create the dependency file for a source of the
          language, followed by the required switches.

   * `Configuration - Search Paths'

        * `Include_Switches': list, indexed, case-insensitive index

          Index is a language name. Value is the list of switches to
          specify to the compiler of the language to indicate a
          directory to look for sources.

        * `Include_Path': single, indexed, case-insensitive index

          Index is a language name. Value is the name of an environment
          variable that contains the path of all the directories that
          the compiler of the language may search for sources.

        * `Include_Path_File': single, indexed, case-insensitive index

          Index is a language name. Value is the name of an environment
          variable the value of which is the path name of a text file
          that contains the directories that the compiler of the
          language may search for sources.

        * `Object_Path_Switches': list, indexed, case-insensitive index

          Index is a language name. Value is the list of switches to
          specify to the compiler of the language the name of a text
          file that contains the list of object directories. When this
          attribute is not declared, the text file is not created.


File: gnat_ugn.info,  Node: Package Cross_Reference Attributes,  Next: Package Finder Attributes,  Prev: Package Compiler Attributes,  Up: Attributes

5.9.10.6 Package Cross_Reference Attributes
...........................................

   * `Default_Switches': list, indexed, case-insensitive index

     Index is a language name. Value is a list of switches to be used
     when invoking `gnatxref' for a source of the language, if there is
     no applicable attribute Switches.

   * `Switches': list, optional index, indexed, case-insensitive index,
     others allowed

     Index is a source file name. Value is the list of switches to be
     used when invoking `gnatxref' for the source.


File: gnat_ugn.info,  Node: Package Finder Attributes,  Next: Package gnatls Attributes,  Prev: Package Cross_Reference Attributes,  Up: Attributes

5.9.10.7 Package Finder Attributes
..................................

   * `Default_Switches': list, indexed, case-insensitive index

     Index is a language name. Value is a list of switches to be used
     when invoking `gnatfind' for a source of the language, if there is
     no applicable attribute Switches.

   * `Switches': list, optional index, indexed, case-insensitive index,
     others allowed

     Index is a source file name. Value is the list of switches to be
     used when invoking `gnatfind' for the source.


File: gnat_ugn.info,  Node: Package gnatls Attributes,  Next: Package IDE Attributes,  Prev: Package Finder Attributes,  Up: Attributes

5.9.10.8 Package gnatls Attributes
..................................

   * `Switches': list

     Value is a list of switches to be used when invoking `gnatls'.


File: gnat_ugn.info,  Node: Package IDE Attributes,  Next: Package Install Attributes,  Prev: Package gnatls Attributes,  Up: Attributes

5.9.10.9 Package IDE Attributes
...............................

   * `Default_Switches': list, indexed

     Index is the name of an external tool that the GNAT Programming
     System (GPS) is supporting. Value is a list of switches to use
     when invoking that tool.

   * `Remote_Host': single

     Value is a string that designates the remote host in a
     cross-compilation environment, to be used for remote compilation
     and debugging. This attribute should not be specified when running
     on the local machine.

   * `Program_Host': single

     Value is a string that specifies the name of IP address of the
     embedded target in a cross-compilation environment, on which the
     program should execute.

   * `Communication_Protocol': single

     Value is the name of the protocol to use to communicate with the
     target in a cross-compilation environment, for example `"wtx"' or
     `"vxworks"'.

   * `Compiler_Command': single, indexed, case-insensitive index

     Index is a language Name. Value is a string that denotes the
     command to be used to invoke the compiler. For historical reasons,
     the value of `Compiler_Command ("Ada")' is expected to be a
     reference to `gnatmake' or `cross-gnatmake'.

   * `Debugger_Command': single

     Value is a string that specifies the name of the debugger to be
     used, such as gdb, powerpc-wrs-vxworks-gdb or gdb-4.

   * `gnatlist': single

     Value is a string that specifies the name of the `gnatls' utility
     to be used to retrieve information about the predefined path; for
     example, `"gnatls"', `"powerpc-wrs-vxworks-gnatls"'.

   * `VCS_Kind': single

     Value is a string used to specify the Version Control System (VCS)
     to be used for this project, for example "Subversion",
     "ClearCase". If the value is set to "Auto", the IDE will try to
     detect the actual VCS used on the list of supported ones.

   * `VCS_File_Check': single

     Value is a string that specifies the command used by the VCS to
     check the validity of a file, either when the user explicitly asks
     for a check, or as a sanity check before doing the check-in.

   * `VCS_Log_Check': single

     Value is a string that specifies the command used by the VCS to
     check the validity of a log file.

   * `Documentation_Dir': single

     Value is the directory used to generate the documentation of
     source code.


File: gnat_ugn.info,  Node: Package Install Attributes,  Next: Package Linker Attributes,  Prev: Package IDE Attributes,  Up: Attributes

5.9.10.10 Package Install Attributes
....................................

   * `Artifacts': list, indexed

     An array attribute to declare a set of files not part of the
     sources to be installed. The array discriminant is the directory
     where the file is to be installed. If a relative directory then
     Prefix (see below) is prepended. Note also that if the same file
     name occurs multiple time in the attribute list, the last one will
     be the one installed.

   * `Prefix': single

     Value is the install destination directory.

   * `Sources_Subdir': single

     Value is the sources directory or subdirectory of Prefix.

   * `Exec_Subdir': single

     Value is the executables directory or subdirectory of Prefix.

   * `Lib_Subdir': single

     Value is library directory or subdirectory of Prefix.

   * `Project_Subdir': single

     Value is the project directory or subdirectory of Prefix.

   * `Active': single

     Indicates that the project is to be installed or not.
     Case-insensitive value "false" means that the project is not to be
     installed, all other values mean that the project is to be
     installed.

   * `Mode': single

     Value is the installation mode, it is either `dev' (default) or
     `usage'.

   * `Install_Name': single

     Specify the name to use for recording the installation. The
     default is the project name without the extension.


File: gnat_ugn.info,  Node: Package Linker Attributes,  Next: Package Naming Attributes,  Prev: Package Install Attributes,  Up: Attributes

5.9.10.11 Package Linker Attributes
...................................

   * `General'

        * `Required_Switches': list

          Value is a list of switches that are required when invoking
          the linker to link an executable.

        * `Default_Switches': list, indexed, case-insensitive index

          Index is a language name. Value is a list of switches for the
          linker when linking an executable for a main source of the
          language, when there is no applicable Switches.

        * `Leading_Switches': list, optional index, indexed,
          case-insensitive index, others allowed

          Index is a source file name or a language name. Value is the
          list of switches to be used at the beginning of the command
          line when invoking the linker to build an executable for the
          source or for its language.

        * `Switches': list, optional index, indexed, case-insensitive
          index, others allowed

          Index is a source file name or a language name. Value is the
          list of switches to be used when invoking the linker to build
          an executable for the source or for its language.

        * `Trailing_Switches': list, optional index, indexed,
          case-insensitive index, others allowed

          Index is a source file name or a language name. Value is the
          list of switches to be used at the end of the command line
          when invoking the linker to build an executable for the
          source or for its language. These switches may override the
          Required_Switches.

        * `Linker_Options': list

          Value is a list of switches/options that are to be added when
          linking an executable from a project importing the current
          project directly or indirectly.  Linker_Options are not used
          when linking an executable from the current project.

        * `Map_File_Option': single

          Value is the switch to specify the map file name that the
          linker needs to create.

   * `Configuration - Linking'

        * `Driver': single

          Value is the name of the linker executable.

   * `Configuration - Response Files'

        * `Max_Command_Line_Length': single

          Value is the maximum number of character in the command line
          when invoking the linker to link an executable.

        * `Response_File_Format': single

          Indicates the kind of response file to create when the length
          of the linking command line is too large. Only authorized
          case-insensitive values are "none", "gnu", "object_list",
          "gcc_gnu", "gcc_option_list" and "gcc_object_list".

        * `Response_File_Switches': list

          Value is the list of switches to specify a response file to
          the linker.


File: gnat_ugn.info,  Node: Package Naming Attributes,  Next: Package Remote Attributes,  Prev: Package Linker Attributes,  Up: Attributes

5.9.10.12 Package Naming Attributes
...................................

   * `Specification_Suffix': single, indexed, case-insensitive index

     Equivalent to attribute Spec_Suffix.

   * `Spec_Suffix': single, indexed, case-insensitive index

     Index is a language name. Value is the extension of file names for
     specs of the language.

   * `Implementation_Suffix': single, indexed, case-insensitive index

     Equivalent to attribute Body_Suffix.

   * `Body_Suffix': single, indexed, case-insensitive index

     Index is a language name. Value is the extension of file names for
     bodies of the language.

   * `Separate_Suffix': single

     Value is the extension of file names for subunits of Ada.

   * `Casing': single

     Indicates the casing of sources of the Ada language. Only
     authorized case-insensitive values are "lowercase", "uppercase"
     and "mixedcase".

   * `Dot_Replacement': single

     Value is the string that replace the dot of unit names in the
     source file names of the Ada language.

   * `Specification': single, optional index, indexed, case-insensitive
     index

     Equivalent to attribute Spec.

   * `Spec': single, optional index, indexed, case-insensitive index

     Index is a unit name. Value is the file name of the spec of the
     unit.

   * `Implementation': single, optional index, indexed,
     case-insensitive index

     Equivalent to attribute Body.

   * `Body': single, optional index, indexed, case-insensitive index

     Index is a unit name. Value is the file name of the body of the
     unit.

   * `Specification_Exceptions': list, indexed, case-insensitive index

     Index is a language name. Value is a list of specs for the
     language that do not necessarily follow the naming scheme for the
     language and that may or may not be found in the source
     directories of the project.

   * `Implementation_Exceptions': list, indexed, case-insensitive index

     Index is a language name. Value is a list of bodies for the
     language that do not necessarily follow the naming scheme for the
     language and that may or may not be found in the source
     directories of the project.


File: gnat_ugn.info,  Node: Package Remote Attributes,  Next: Package Stack Attributes,  Prev: Package Naming Attributes,  Up: Attributes

5.9.10.13 Package Remote Attributes
...................................

   * `Included_Patterns': list

     If this attribute is defined it sets the patterns to synchronized
     from the master to the slaves. It is exclusive with
     Excluded_Patterns, that is it is an error to define both.

   * `Included_Artifact_Patterns': list

     If this attribute is defined it sets the patterns of compilation
     artifacts to synchronized from the slaves to the build master.
     This attribute replace the default hard-coded patterns.

   * `Excluded_Patterns': list

     Set of patterns to ignore when synchronizing sources from the build
     master to the slaves. A set of predefined patterns are supported
     (e.g. *.o, *.ali, *.exe, etc.), this attributes make it possible to
     add some more patterns.

   * `Root_Dir': single

     Value is the root directory used by the slave machines.


File: gnat_ugn.info,  Node: Package Stack Attributes,  Next: Package Synchronize Attributes,  Prev: Package Remote Attributes,  Up: Attributes

5.9.10.14 Package Stack Attributes
..................................

   * `Switches': list

     Value is the list of switches to be used when invoking `gnatstack'.


File: gnat_ugn.info,  Node: Package Synchronize Attributes,  Prev: Package Stack Attributes,  Up: Attributes

5.9.10.15 Package Synchronize Attributes
........................................

   * `Default_Switches': list, indexed, case-insensitive index

     Index is a language name. Value is a list of switches to be used
     when invoking `gnatsync' for a source of the language, if there is
     no applicable attribute Switches.

   * `Switches': list, optional index, indexed, case-insensitive index,
     others allowed

     Index is a source file name. Value is the list of switches to be
     used when invoking `gnatsync' for the source.


File: gnat_ugn.info,  Node: Tools Supporting Project Files,  Next: GNAT Utility Programs,  Prev: GNAT Project Manager,  Up: Top

6 Tools Supporting Project Files
********************************

This section describes how project files can be used in conjunction
with a number of GNAT tools.

* Menu:

* gnatmake and Project Files::
* The GNAT Driver and Project Files::


File: gnat_ugn.info,  Node: gnatmake and Project Files,  Next: The GNAT Driver and Project Files,  Up: Tools Supporting Project Files

6.1 gnatmake and Project Files
==============================

This section covers several topics related to `gnatmake' and project
files: defining switches for `gnatmake' and for the tools that it
invokes; specifying configuration pragmas; the use of the `Main'
attribute; building and rebuilding library project files.

* Menu:

* Switches Related to Project Files::
* Switches and Project Files::
* Specifying Configuration Pragmas::
* Project Files and Main Subprograms::
* Library Project Files::


File: gnat_ugn.info,  Node: Switches Related to Project Files,  Next: Switches and Project Files,  Up: gnatmake and Project Files

6.1.1 Switches Related to Project Files
---------------------------------------

The following switches are used by GNAT tools that support project
files:

 
`-P`project''
     Indicates the name of a project file. This project file will be
     parsed with the verbosity indicated by `-vP*x*', if any, and using
     the external references indicated by `-X' switches, if any.  There
     may zero, one or more spaces between `-P' and `project'.

     There must be only one `-P' switch on the command line.

     Since the Project Manager parses the project file only after all
     the switches on the command line are checked, the order of the
     switches `-P', `-vP*x*' or `-X' is not significant.

`-X`name'=`value''
     Indicates that external variable `name' has the value `value'.
     The Project Manager will use this value for occurrences of
     `external(name)' when parsing the project file.

     If `name' or `value' includes a space, then `name=value' should be
     put between quotes.

         -XOS=NT
         -X"user=John Doe"

     Several `-X' switches can be used simultaneously.  If several `-X'
     switches specify the same `name', only the last one is used.

     An external variable specified with a `-X' switch takes precedence
     over the value of the same name in the environment.

`-vP`x''
     Indicates the verbosity of the parsing of GNAT project files.

     `-vP0' means Default; `-vP1' means Medium; `-vP2' means High.

     The default is Default: no output for syntactically correct
     project files.  If several `-vP*x*' switches are present, only the
     last one is used.

`-aP`dir''
     Add directory `dir' at the beginning of the project search path,
     in order, after the current working directory.

`-eL'
     Follow all symbolic links when processing project files.

`--subdirs=`subdir''
     This switch is recognized by `gnatmake' and `gnatclean'. It
     indicate that the real directories (except the source directories)
     are the subdirectories `subdir' of the directories specified in
     the project files.  This applies in particular to object
     directories, library directories and exec directories. If the
     subdirectories do not exist, they are created automatically.


File: gnat_ugn.info,  Node: Switches and Project Files,  Next: Specifying Configuration Pragmas,  Prev: Switches Related to Project Files,  Up: gnatmake and Project Files

6.1.2 Switches and Project Files
--------------------------------

For each of the packages `Builder', `Compiler', `Binder', and `Linker',
you can specify a `Default_Switches' attribute, a `Switches' attribute,
or both; as their names imply, these switch-related attributes affect
the switches that are used for each of these GNAT components when
`gnatmake' is invoked.  As will be explained below, these
component-specific switches precede the switches provided on the
`gnatmake' command line.

The `Default_Switches' attribute is an attribute indexed by language
name (case insensitive) whose value is a string list.  For example:

         package Compiler is
           for Default_Switches ("Ada")
               use ("-gnaty",
                    "-v");
         end Compiler;

The `Switches' attribute is indexed on a file name (which may or may
not be case sensitive, depending on the operating system) whose value
is a string list.  For example:

         package Builder is
            for Switches ("main1.adb")
                use ("-O2");
            for Switches ("main2.adb")
                use ("-g");
         end Builder;

For the `Builder' package, the file names must designate source files
for main subprograms.  For the `Binder' and `Linker' packages, the file
names must designate `ALI' or source files for main subprograms.  In
each case just the file name without an explicit extension is
acceptable.

For each tool used in a program build (`gnatmake', the compiler, the
binder, and the linker), the corresponding package @dfn{contributes} a
set of switches for each file on which the tool is invoked, based on the
switch-related attributes defined in the package.  In particular, the
switches that each of these packages contributes for a given file `f'
comprise:

   * the value of attribute `Switches (`f')`, if it is specified in the
     package for the given file,

   * otherwise, the value of `Default_Switches ("Ada")', if it is
     specified in the package.

If neither of these attributes is defined in the package, then the
package does not contribute any switches for the given file.

When `gnatmake' is invoked on a file, the switches comprise two sets,
in the following order: those contributed for the file by the `Builder'
package; and the switches passed on the command line.

When `gnatmake' invokes a tool (compiler, binder, linker) on a file,
the switches passed to the tool comprise three sets, in the following
order:

   * the applicable switches contributed for the file by the `Builder'
     package in the project file supplied on the command line;

   * those contributed for the file by the package (in the relevant
     project file - see below) corresponding to the tool; and

   * the applicable switches passed on the command line.

The term `applicable switches' reflects the fact that `gnatmake'
switches may or may not be passed to individual tools, depending on the
individual switch.

`gnatmake' may invoke the compiler on source files from different
projects. The Project Manager will use the appropriate project file to
determine the `Compiler' package for each source file being compiled.
Likewise for the `Binder' and `Linker' packages.

As an example, consider the following package in a project file:

         project Proj1 is
            package Compiler is
               for Default_Switches ("Ada")
                   use ("-g");
               for Switches ("a.adb")
                   use ("-O1");
               for Switches ("b.adb")
                   use ("-O2",
                        "-gnaty");
            end Compiler;
         end Proj1;

If `gnatmake' is invoked with this project file, and it needs to
compile, say, the files `a.adb', `b.adb', and `c.adb', then `a.adb'
will be compiled with the switch `-O1', `b.adb' with switches `-O2' and
`-gnaty', and `c.adb' with `-g'.

The following example illustrates the ordering of the switches
contributed by different packages:

         project Proj2 is
            package Builder is
               for Switches ("main.adb")
                   use ("-g",
                        "-O1",
                        "-f");
            end Builder;

            package Compiler is
               for Switches ("main.adb")
                   use ("-O2");
            end Compiler;
         end Proj2;

If you issue the command:

         $ gnatmake -Pproj2 -O0 main

then the compiler will be invoked on `main.adb' with the following
sequence of switches

         -g -O1 -O2 -O0

with the last `-O' switch having precedence over the earlier ones;
several other switches (such as `-c') are added implicitly.

The switches `-g' and `-O1' are contributed by package `Builder',
`-O2' is contributed by the package `Compiler' and `-O0' comes from the
command line.

The `-g' switch will also be passed in the invocation of `Gnatlink.'

A final example illustrates switch contributions from packages in
different project files:

         project Proj3 is
            for Source_Files use ("pack.ads", "pack.adb");
            package Compiler is
               for Default_Switches ("Ada")
                   use ("-gnata");
            end Compiler;
         end Proj3;

         with "Proj3";
         project Proj4 is
            for Source_Files use ("foo_main.adb", "bar_main.adb");
            package Builder is
               for Switches ("foo_main.adb")
                   use ("-s",
                        "-g");
            end Builder;
         end Proj4;

         -- Ada source file:
         with Pack;
         procedure Foo_Main is
            ...
         end Foo_Main;

If the command is

         $ gnatmake -PProj4 foo_main.adb -cargs -gnato

then the switches passed to the compiler for `foo_main.adb' are `-g'
(contributed by the package `Proj4.Builder') and `-gnato' (passed on
the command line).  When the imported package `Pack' is compiled, the
switches used are `-g' from `Proj4.Builder', `-gnata' (contributed from
package `Proj3.Compiler', and `-gnato' from the command line.

When using `gnatmake' with project files, some switches or arguments
may be expressed as relative paths. As the working directory where
compilation occurs may change, these relative paths are converted to
absolute paths. For the switches found in a project file, the relative
paths are relative to the project file directory, for the switches on
the command line, they are relative to the directory where `gnatmake'
is invoked.  The switches for which this occurs are: -I, -A, -L, -aO,
-aL, -aI, as well as all arguments that are not switches (arguments to
switch -o, object files specified in package `Linker' or after -largs
on the command line). The exception to this rule is the switch -RTS=
for which a relative path argument is never converted.


File: gnat_ugn.info,  Node: Specifying Configuration Pragmas,  Next: Project Files and Main Subprograms,  Prev: Switches and Project Files,  Up: gnatmake and Project Files

6.1.3 Specifying Configuration Pragmas
--------------------------------------

When using `gnatmake' with project files, if there exists a file
`gnat.adc' that contains configuration pragmas, this file will be
ignored.

Configuration pragmas can be defined by means of the following
attributes in project files: `Global_Configuration_Pragmas' in package
`Builder' and `Local_Configuration_Pragmas' in package `Compiler'.

Both these attributes are single string attributes. Their values is the
path name of a file containing configuration pragmas. If a path name is
relative, then it is relative to the project directory of the project
file where the attribute is defined.

When compiling a source, the configuration pragmas used are, in order,
those listed in the file designated by attribute
`Global_Configuration_Pragmas' in package `Builder' of the main project
file, if it is specified, and those listed in the file designated by
attribute `Local_Configuration_Pragmas' in package `Compiler' of the
project file of the source, if it exists.


File: gnat_ugn.info,  Node: Project Files and Main Subprograms,  Next: Library Project Files,  Prev: Specifying Configuration Pragmas,  Up: gnatmake and Project Files

6.1.4 Project Files and Main Subprograms
----------------------------------------

When using a project file, you can invoke `gnatmake' with one or
several main subprograms, by specifying their source files on the
command line.

         $ gnatmake -Pprj main1.adb main2.adb main3.adb

Each of these needs to be a source file of the same project, except
when the switch `-u' is used.

When `-u' is not used, all the mains need to be sources of the same
project, one of the project in the tree rooted at the project specified
on the command line. The package `Builder' of this common project, the
"main project" is the one that is considered by `gnatmake'.

When `-u' is used, the specified source files may be in projects
imported directly or indirectly by the project specified on the command
line.  Note that if such a source file is not part of the project
specified on the command line, the switches found in package `Builder'
of the project specified on the command line, if any, that are
transmitted to the compiler will still be used, not those found in the
project file of the source file.

When using a project file, you can also invoke `gnatmake' without
explicitly specifying any main, and the effect depends on whether you
have defined the `Main' attribute.  This attribute has a string list
value, where each element in the list is the name of a source file (the
file extension is optional) that contains a unit that can be a main
subprogram.

If the `Main' attribute is defined in a project file as a non-empty
string list and the switch `-u' is not used on the command line, then
invoking `gnatmake' with this project file but without any main on the
command line is equivalent to invoking `gnatmake' with all the file
names in the `Main' attribute on the command line.

Example:

         project Prj is
            for Main use ("main1.adb", "main2.adb", "main3.adb");
         end Prj;

With this project file, `"gnatmake -Pprj"' is equivalent to `"gnatmake
-Pprj main1.adb main2.adb main3.adb"'.

When the project attribute `Main' is not specified, or is specified as
an empty string list, or when the switch `-u' is used on the command
line, then invoking `gnatmake' with no main on the command line will
result in all immediate sources of the project file being checked, and
potentially recompiled. Depending on the presence of the switch `-u',
sources from other project files on which the immediate sources of the
main project file depend are also checked and potentially recompiled.
In other words, the `-u' switch is applied to all of the immediate
sources of the main project file.

When no main is specified on the command line and attribute `Main'
exists and includes several mains, or when several mains are specified
on the command line, the default switches in package `Builder' will be
used for all mains, even if there are specific switches specified for
one or several mains.

But the switches from package `Binder' or `Linker' will be the specific
switches for each main, if they are specified.


File: gnat_ugn.info,  Node: Library Project Files,  Prev: Project Files and Main Subprograms,  Up: gnatmake and Project Files

6.1.5 Library Project Files
---------------------------

When `gnatmake' is invoked with a main project file that is a library
project file, it is not allowed to specify one or more mains on the
command line.

When a library project file is specified, switches `-b' and `-l' have
special meanings.

   * `-b' is only allowed for stand-alone libraries. It indicates to
     `gnatmake' that `gnatbind' should be invoked for the library.

   * `-l' may be used for all library projects. It indicates to
     `gnatmake' that the binder generated file should be compiled (in
     the case of a stand-alone library) and that the library should be
     built.


File: gnat_ugn.info,  Node: The GNAT Driver and Project Files,  Prev: gnatmake and Project Files,  Up: Tools Supporting Project Files

6.2 The GNAT Driver and Project Files
=====================================

A number of GNAT tools beyond `gnatmake' can benefit from project files:

   * `gnatbind'

   * `gnatclean'

   * `gnatfind'

   * `gnatlink'

   * `gnatls'

   * `gnatxref'

However, none of these tools can be invoked directly with a project
file switch (`-P').  They must be invoked through the `gnat' driver.

The `gnat' driver is a wrapper that accepts a number of commands and
calls the corresponding tool. It was designed initially for VMS
platforms (to convert VMS qualifiers to Unix-style switches), but it is
now available on all GNAT platforms.

On non-VMS platforms, the `gnat' driver accepts the following commands
(case insensitive):

   * BIND to invoke `gnatbind'

   * CHOP to invoke `gnatchop'

   * CLEAN to invoke `gnatclean'

   * COMP or COMPILE to invoke the compiler

   * FIND to invoke `gnatfind'

   * KR or KRUNCH to invoke `gnatkr'

   * LINK to invoke `gnatlink'

   * LS or LIST to invoke `gnatls'

   * MAKE to invoke `gnatmake'

   * NAME to invoke `gnatname'

   * PREP or PREPROCESS to invoke `gnatprep'

   * XREF to invoke `gnatxref'

Note that the command `gnatmake -c -f -u' is used to invoke the
compiler.

On non-VMS platforms, between `gnat' and the command, two special
switches may be used:

   * `-v' to display the invocation of the tool.

   * `-dn' to prevent the `gnat' driver from removing the temporary
     files it has created. These temporary files are configuration
     files and temporary file list files.

The command may be followed by switches and arguments for the invoked
tool.

         $ gnat bind -C main.ali
         $ gnat ls -a main
         $ gnat chop foo.txt

Switches may also be put in text files, one switch per line, and the
text files may be specified with their path name preceded by '@'.

         $ gnat bind @args.txt main.ali

In addition, for the following commands the project file related
switches (`-P', `-X' and `-vPx') may be used in addition to the
switches of the invoking tool:

   * BIND

   * COMP or COMPILE

   * FIND

   * LS or LIST

   * LINK

   * XREF

For each of the following commands, there is optionally a corresponding
package in the main project.

   * package `Binder' for command BIND (invoking `gnatbind')

   * package `Compiler' for command COMP or COMPILE (invoking the
     compiler)

   * package `Cross_Reference' for command XREF (invoking `gnatxref')

   * package `Finder' for command FIND (invoking `gnatfind')

   * package `Gnatls' for command LS or LIST (invoking `gnatls')

   * package `Linker' for command LINK (invoking `gnatlink')

Package `Gnatls' has a unique attribute `Switches', a simple variable
with a string list value. It contains switches for the invocation of
`gnatls'.

         project Proj1 is
            package gnatls is
               for Switches
                   use ("-a",
                        "-v");
            end gnatls;
         end Proj1;

All other packages have two attribute `Switches' and `Default_Switches'.

`Switches' is an indexed attribute, indexed by the source file name,
that has a string list value: the switches to be used when the tool
corresponding to the package is invoked for the specific source file.

`Default_Switches' is an attribute, indexed by  the programming
language that has a string list value.  `Default_Switches ("Ada")'
contains the switches for the invocation of the tool corresponding to
the package, except if a specific `Switches' attribute is specified for
the source file.

         project Proj is

            for Source_Dirs use ("");

            package gnatls is
               for Switches use
                   ("-a",
                    "-v");
            end gnatls;

            package Compiler is
               for Default_Switches ("Ada")
                   use ("-gnatv",
                        "-gnatwa");
            end Binder;

            package Binder is
               for Default_Switches ("Ada")
                   use ("-C",
                        "-e");
            end Binder;

            package Linker is
               for Default_Switches ("Ada")
                   use ("-C");
               for Switches ("main.adb")
                   use ("-C",
                        "-v",
                        "-v");
            end Linker;

            package Finder is
               for Default_Switches ("Ada")
                    use ("-a",
                         "-f");
            end Finder;

            package Cross_Reference is
               for Default_Switches ("Ada")
                   use ("-a",
                        "-f",
                        "-d",
                        "-u");
            end Cross_Reference;
         end Proj;

With the above project file, commands such as

         $ gnat comp -Pproj main
         $ gnat ls -Pproj main
         $ gnat xref -Pproj main
         $ gnat bind -Pproj main.ali
         $ gnat link -Pproj main.ali

will set up the environment properly and invoke the tool with the
switches found in the package corresponding to the tool:
`Default_Switches ("Ada")' for all tools, except `Switches ("main.adb")'
for `gnatlink'.


File: gnat_ugn.info,  Node: GNAT Utility Programs,  Next: GNAT and Program Execution,  Prev: Tools Supporting Project Files,  Up: Top

7 GNAT Utility Programs
***********************

This chapter describes a number of utility programs:

   * *note The File Cleanup Utility gnatclean: 22.

   * *note The GNAT Library Browser gnatls: 23.

   * *note The Cross-Referencing Tools gnatxref and gnatfind: 24.

   * *note The Ada to HTML Converter gnathtml: 25.

Other GNAT utilities are described elsewhere in this manual:

   * *note Handling Arbitrary File Naming Conventions with gnatname: 5b.

   * *note File Name Krunching with gnatkr: 65.

   * *note Renaming Files with gnatchop: 38.

   * *note Preprocessing with gnatprep: 19.

* Menu:

* The File Cleanup Utility gnatclean::
* The GNAT Library Browser gnatls::
* The Cross-Referencing Tools gnatxref and gnatfind::
* The Ada to HTML Converter gnathtml::


File: gnat_ugn.info,  Node: The File Cleanup Utility gnatclean,  Next: The GNAT Library Browser gnatls,  Up: GNAT Utility Programs

7.1 The File Cleanup Utility `gnatclean'
========================================

`gnatclean' is a tool that allows the deletion of files produced by the
compiler, binder and linker, including ALI files, object files, tree
files, expanded source files, library files, interface copy source
files, binder generated files and executable files.

* Menu:

* Running gnatclean::
* Switches for gnatclean::


File: gnat_ugn.info,  Node: Running gnatclean,  Next: Switches for gnatclean,  Up: The File Cleanup Utility gnatclean

7.1.1 Running `gnatclean'
-------------------------

The `gnatclean' command has the form:

         $ gnatclean switches `names`

where `names' is a list of source file names. Suffixes `.ads' and `adb'
may be omitted. If a project file is specified using switch `-P', then
`names' may be completely omitted.

In normal mode, `gnatclean' delete the files produced by the compiler
and, if switch `-c' is not specified, by the binder and the linker. In
informative-only mode, specified by switch `-n', the list of files that
would have been deleted in normal mode is listed, but no file is
actually deleted.


File: gnat_ugn.info,  Node: Switches for gnatclean,  Prev: Running gnatclean,  Up: The File Cleanup Utility gnatclean

7.1.2 Switches for `gnatclean'
------------------------------

`gnatclean' recognizes the following switches:

`--version'
     Display Copyright and version, then exit disregarding all other
     options.

`--help'
     If `-version' was not used, display usage, then exit disregarding
     all other options.

`--subdirs=`subdir''
     Actual object directory of each project file is the subdirectory
     subdir of the object directory specified or defaulted in the
     project file.

`--unchecked-shared-lib-imports'
     By default, shared library projects are not allowed to import
     static library projects. When this switch is used on the command
     line, this restriction is relaxed.

`-c'
     Only attempt to delete the files produced by the compiler, not
     those produced by the binder or the linker. The files that are not
     to be deleted are library files, interface copy files, binder
     generated files and executable files.

`-D `dir''
     Indicate that ALI and object files should normally be found in
     directory `dir'.

`-F'
     When using project files, if some errors or warnings are detected
     during parsing and verbose mode is not in effect (no use of switch
     -v), then error lines start with the full path name of the project
     file, rather than its simple file name.

`-h'
     Output a message explaining the usage of `gnatclean'.

`-n'
     Informative-only mode. Do not delete any files. Output the list of
     the files that would have been deleted if this switch was not
     specified.

`-P`project''
     Use project file `project'. Only one such switch can be used.
     When cleaning a project file, the files produced by the
     compilation of the immediate sources or inherited sources of the
     project files are to be deleted. This is not depending on the
     presence or not of executable names on the command line.

`-q'
     Quiet output. If there are no errors, do not output anything,
     except in verbose mode (switch -v) or in informative-only mode
     (switch -n).

`-r'
     When a project file is specified (using switch -P), clean all
     imported and extended project files, recursively. If this switch
     is not specified, only the files related to the main project file
     are to be deleted. This switch has no effect if no project file is
     specified.

`-v'
     Verbose mode.

`-vP`x''
     Indicates the verbosity of the parsing of GNAT project files.
     *note Switches Related to Project Files: e6.

`-X`name'=`value''
     Indicates that external variable `name' has the value `value'.
     The Project Manager will use this value for occurrences of
     `external(name)' when parsing the project file.  *note Switches
     Related to Project Files: e6.

`-aO`dir''
     When searching for ALI and object files, look in directory `dir'.

`-I`dir''
     Equivalent to `-aO`dir''.

`-I-'
     Do not look for ALI or object files in the directory where
     `gnatclean' was invoked.


File: gnat_ugn.info,  Node: The GNAT Library Browser gnatls,  Next: The Cross-Referencing Tools gnatxref and gnatfind,  Prev: The File Cleanup Utility gnatclean,  Up: GNAT Utility Programs

7.2 The GNAT Library Browser `gnatls'
=====================================

`gnatls' is a tool that outputs information about compiled units. It
gives the relationship between objects, unit names and source files. It
can also be used to check the source dependencies of a unit as well as
various characteristics.

Note: to invoke `gnatls' with a project file, use the `gnat' driver
(see *note The GNAT Driver and Project Files: 122.).

* Menu:

* Running gnatls::
* Switches for gnatls::
* Example of gnatls Usage::


File: gnat_ugn.info,  Node: Running gnatls,  Next: Switches for gnatls,  Up: The GNAT Library Browser gnatls

7.2.1 Running `gnatls'
----------------------

The `gnatls' command has the form

         $ gnatls switches `object_or_ali_file`

The main argument is the list of object or `ali' files (see *note The
Ada Library Information Files: 44.)  for which information is requested.

In normal mode, without additional option, `gnatls' produces a
four-column listing. Each line represents information for a specific
object. The first column gives the full path of the object, the second
column gives the name of the principal unit in this object, the third
column gives the status of the source and the fourth column gives the
full path of the source representing this unit.  Here is a simple
example of use:

         $ gnatls *.o
         ./demo1.o            demo1            DIF demo1.adb
         ./demo2.o            demo2             OK demo2.adb
         ./hello.o            h1                OK hello.adb
         ./instr-child.o      instr.child      MOK instr-child.adb
         ./instr.o            instr             OK instr.adb
         ./tef.o              tef              DIF tef.adb
         ./text_io_example.o  text_io_example   OK text_io_example.adb
         ./tgef.o             tgef             DIF tgef.adb

The first line can be interpreted as follows: the main unit which is
contained in object file `demo1.o' is demo1, whose main source is in
`demo1.adb'. Furthermore, the version of the source used for the
compilation of demo1 has been modified (DIF). Each source file has a
status qualifier which can be:

`OK (unchanged)'
     The version of the source file used for the compilation of the
     specified unit corresponds exactly to the actual source file.

`MOK (slightly modified)'
     The version of the source file used for the compilation of the
     specified unit differs from the actual source file but not enough
     to require recompilation. If you use gnatmake with the qualifier
     `-m (minimal recompilation)', a file marked MOK will not be
     recompiled.

`DIF (modified)'
     No version of the source found on the path corresponds to the
     source used to build this object.

`??? (file not found)'
     No source file was found for this unit.

`HID (hidden,  unchanged version not first on PATH)'
     The version of the source that corresponds exactly to the source
     used for compilation has been found on the path but it is hidden
     by another version of the same source that has been modified.


File: gnat_ugn.info,  Node: Switches for gnatls,  Next: Example of gnatls Usage,  Prev: Running gnatls,  Up: The GNAT Library Browser gnatls

7.2.2 Switches for `gnatls'
---------------------------

`gnatls' recognizes the following switches:

`--version'
     Display Copyright and version, then exit disregarding all other
     options.

`*--help'
     If `-version' was not used, display usage, then exit disregarding
     all other options.

`-a'
     Consider all units, including those of the predefined Ada library.
     Especially useful with `-d'.

`-d'
     List sources from which specified units depend on.

`-h'
     Output the list of options.

`-o'
     Only output information about object files.

`-s'
     Only output information about source files.

`-u'
     Only output information about compilation units.

`-files=`file''
     Take as arguments the files listed in text file `file'.  Text file
     `file' may contain empty lines that are ignored.  Each nonempty
     line should contain the name of an existing file.  Several such
     switches may be specified simultaneously.

`-aO`dir'', `-aI`dir'', `-I`dir'', `-I-', `-nostdinc'
     Source path manipulation. Same meaning as the equivalent `gnatmake'
     flags (*note Switches for gnatmake: e2.).

`-aP`dir''
     Add `dir' at the beginning of the project search dir.

`--RTS=`rts-path'`'
     Specifies the default location of the runtime library. Same
     meaning as the equivalent `gnatmake' flag (*note Switches for
     gnatmake: e2.).

`-v'
     Verbose mode. Output the complete source, object and project
     paths. Do not use the default column layout but instead use long
     format giving as much as information possible on each requested
     units, including special characteristics such as:

        * `Preelaborable': The unit is preelaborable in the Ada sense.

        * `No_Elab_Code':  No elaboration code has been produced by the
          compiler for this unit.

        * `Pure': The unit is pure in the Ada sense.

        * `Elaborate_Body': The unit contains a pragma Elaborate_Body.

        * `Remote_Types': The unit contains a pragma Remote_Types.

        * `Shared_Passive': The unit contains a pragma Shared_Passive.

        * `Predefined': This unit is part of the predefined environment
          and cannot be modified by the user.

        * `Remote_Call_Interface': The unit contains a pragma
          Remote_Call_Interface.


File: gnat_ugn.info,  Node: Example of gnatls Usage,  Prev: Switches for gnatls,  Up: The GNAT Library Browser gnatls

7.2.3 Example of `gnatls' Usage
-------------------------------

Example of using the verbose switch. Note how the source and object
paths are affected by the -I switch.

         $ gnatls -v -I.. demo1.o

         GNATLS 5.03w (20041123-34)
         Copyright 1997-2004 Free Software Foundation, Inc.

         Source Search Path:
            <Current_Directory>
            ../
            /home/comar/local/adainclude/

         Object Search Path:
            <Current_Directory>
            ../
            /home/comar/local/lib/gcc-lib/x86-linux/3.4.3/adalib/

         Project Search Path:
            <Current_Directory>
            /home/comar/local/lib/gnat/

         ./demo1.o
            Unit =>
              Name   => demo1
              Kind   => subprogram body
              Flags  => No_Elab_Code
              Source => demo1.adb    modified

The following is an example of use of the dependency list.  Note the
use of the -s switch which gives a straight list of source files. This
can be useful for building specialized scripts.

         $ gnatls -d demo2.o
         ./demo2.o   demo2        OK demo2.adb
                                  OK gen_list.ads
                                  OK gen_list.adb
                                  OK instr.ads
                                  OK instr-child.ads

         $ gnatls -d -s -a demo1.o
         demo1.adb
         /home/comar/local/adainclude/ada.ads
         /home/comar/local/adainclude/a-finali.ads
         /home/comar/local/adainclude/a-filico.ads
         /home/comar/local/adainclude/a-stream.ads
         /home/comar/local/adainclude/a-tags.ads
         gen_list.ads
         gen_list.adb
         /home/comar/local/adainclude/gnat.ads
         /home/comar/local/adainclude/g-io.ads
         instr.ads
         /home/comar/local/adainclude/system.ads
         /home/comar/local/adainclude/s-exctab.ads
         /home/comar/local/adainclude/s-finimp.ads
         /home/comar/local/adainclude/s-finroo.ads
         /home/comar/local/adainclude/s-secsta.ads
         /home/comar/local/adainclude/s-stalib.ads
         /home/comar/local/adainclude/s-stoele.ads
         /home/comar/local/adainclude/s-stratt.ads
         /home/comar/local/adainclude/s-tasoli.ads
         /home/comar/local/adainclude/s-unstyp.ads
         /home/comar/local/adainclude/unchconv.ads


File: gnat_ugn.info,  Node: The Cross-Referencing Tools gnatxref and gnatfind,  Next: The Ada to HTML Converter gnathtml,  Prev: The GNAT Library Browser gnatls,  Up: GNAT Utility Programs

7.3 The Cross-Referencing Tools `gnatxref' and `gnatfind'
=========================================================

The compiler generates cross-referencing information (unless you set
the `-gnatx' switch), which are saved in the `.ali' files.  This
information indicates where in the source each entity is declared and
referenced. Note that entities in package Standard are not included, but
entities in all other predefined units are included in the output.

Before using any of these two tools, you need to compile successfully
your application, so that GNAT gets a chance to generate the
cross-referencing information.

The two tools `gnatxref' and `gnatfind' take advantage of this
information to provide the user with the capability to easily locate the
declaration and references to an entity. These tools are quite similar,
the difference being that `gnatfind' is intended for locating
definitions and/or references to a specified entity or entities, whereas
`gnatxref' is oriented to generating a full report of all
cross-references.

To use these tools, you must not compile your application using the
`-gnatx' switch on the `gnatmake' command line (see *note Building with
gnatmake: 1d.). Otherwise, cross-referencing information will not be
generated.

Note: to invoke `gnatxref' or `gnatfind' with a project file, use the
`gnat' driver (see *note The GNAT Driver and Project Files: 122.).

* Menu:

* gnatxref Switches::
* gnatfind Switches::
* Project Files for gnatxref and gnatfind::
* Regular Expressions in gnatfind and gnatxref::
* Examples of gnatxref Usage::
* Examples of gnatfind Usage::


File: gnat_ugn.info,  Node: gnatxref Switches,  Next: gnatfind Switches,  Up: The Cross-Referencing Tools gnatxref and gnatfind

7.3.1 `gnatxref' Switches
-------------------------

The command invocation for `gnatxref' is:

         $ gnatxref [`switches`] `sourcefile1` [`sourcefile2` ...]

where

`sourcefile1' [, `sourcefile2' ...]
     identify the source files for which a report is to be generated.
     The 'with'ed units will be processed too. You must provide at
     least one file.

     These file names are considered to be regular expressions, so for
     instance specifying `source*.adb' is the same as giving every file
     in the current directory whose name starts with `source' and whose
     extension is `adb'.

     You shouldn't specify any directory name, just base names.
     `gnatxref' and `gnatfind' will be able to locate these files by
     themselves using the source path. If you specify directories, no
     result is produced.

The following switches are available for `gnatxref':

`-version'
     Display Copyright and version, then exit disregarding all other
     options.

`-help'
     If `-version' was not used, display usage, then exit disregarding
     all other options.

`a'
     If this switch is present, `gnatfind' and `gnatxref' will parse
     the read-only files found in the library search path. Otherwise,
     these files will be ignored. This option can be used to protect
     Gnat sources or your own libraries from being parsed, thus making
     `gnatfind' and `gnatxref' much faster, and their output much
     smaller. Read-only here refers to access or permissions status in
     the file system for the current user.

`aI`DIR''
     When looking for source files also look in directory DIR. The
     order in which source file search is undertaken is the same as for
     `gnatmake'.

`aO`DIR''
     When searching for library and object files, look in directory
     DIR. The order in which library files are searched is the same as
     for `gnatmake'.

`nostdinc'
     Do not look for sources in the system default directory.

`nostdlib'
     Do not look for library files in the system default directory.

`-ext=`extension''
     Specify an alternate ali file extension. The default is `ali' and
     other extensions (e.g. `gli' for C/C++ sources when using
     `-fdump-xref') may be specified via this switch. Note that if this
     switch overrides the default, which means that only the new
     extension will be considered.

`-RTS=`rts-path''
     Specifies the default location of the runtime library. Same
     meaning as the equivalent `gnatmake' flag (*note Switches for
     gnatmake: e2.).

`d'
     If this switch is set `gnatxref' will output the parent type
     reference for each matching derived types.

`f'
     If this switch is set, the output file names will be preceded by
     their directory (if the file was found in the search path). If
     this switch is not set, the directory will not be printed.

`g'
     If this switch is set, information is output only for library-level
     entities, ignoring local entities. The use of this switch may
     accelerate `gnatfind' and `gnatxref'.

`I`DIR''
     Equivalent to `-aODIR -aIDIR'.

`p`FILE''
     Specify a project file to use *note GNAT Project Manager: b.  If
     you need to use the `.gpr' project files, you should use gnatxref
     through the GNAT driver (`gnat xref -Pproject').

     By default, `gnatxref' and `gnatfind' will try to locate a project
     file in the current directory.

     If a project file is either specified or found by the tools, then
     the content of the source directory and object directory lines are
     added as if they had been specified respectively by `-aI' and
     `-aO'.

`u'
     Output only unused symbols. This may be really useful if you give
     your main compilation unit on the command line, as `gnatxref' will
     then display every unused entity and 'with'ed package.

`v'
     Instead of producing the default output, `gnatxref' will generate a
     `tags' file that can be used by vi. For examples how to use this
     feature, see *note Examples of gnatxref Usage: 1e0. The tags file
     is output to the standard output, thus you will have to redirect
     it to a file.

All these switches may be in any order on the command line, and may even
appear after the file names. They need not be separated by spaces, thus
you can say `gnatxref -ag' instead of `gnatxref -a -g'.


File: gnat_ugn.info,  Node: gnatfind Switches,  Next: Project Files for gnatxref and gnatfind,  Prev: gnatxref Switches,  Up: The Cross-Referencing Tools gnatxref and gnatfind

7.3.2 `gnatfind' Switches
-------------------------

The command invocation for `gnatfind' is:

         $ gnatfind [`switches`] `pattern`[:`sourcefile`[:`line`[:`column`]]]
               [`file1` `file2` ...]

with the following iterpretation of the command arguments:

`pattern'
     An entity will be output only if it matches the regular expression
     found in `pattern', see *note Regular Expressions in gnatfind and
     gnatxref: 1e3.

     Omitting the pattern is equivalent to specifying `*', which will
     match any entity. Note that if you do not provide a pattern, you
     have to provide both a sourcefile and a line.

     Entity names are given in Latin-1, with uppercase/lowercase
     equivalence for matching purposes. At the current time there is no
     support for 8-bit codes other than Latin-1, or for wide characters
     in identifiers.

`sourcefile'
     `gnatfind' will look for references, bodies or declarations of
     symbols referenced in `sourcefile', at line `line' and column
     `column'. See *note Examples of gnatfind Usage: 1e4.  for syntax
     examples.

`line'
     A decimal integer identifying the line number containing the
     reference to the entity (or entities) to be located.

`column'
     A decimal integer identifying the exact location on the line of
     the first character of the identifier for the entity reference.
     Columns are numbered from 1.

`file1 file2 ...'
     The search will be restricted to these source files. If none are
     given, then the search will be conducted for every library file in
     the search path.  These files must appear only after the pattern
     or sourcefile.

     These file names are considered to be regular expressions, so for
     instance specifying `source*.adb' is the same as giving every file
     in the current directory whose name starts with `source' and whose
     extension is `adb'.

     The location of the spec of the entity will always be displayed,
     even if it isn't in one of `file1', `file2', ... The occurrences
     of the entity in the separate units of the ones given on the
     command line will also be displayed.

     Note that if you specify at least one file in this part,
     `gnatfind' may sometimes not be able to find the body of the
     subprograms.

At least one of 'sourcefile' or 'pattern' has to be present on the
command line.

The following switches are available:

`--version'
     Display Copyright and version, then exit disregarding all other
     options.

`-help'
     If `-version' was not used, display usage, then exit disregarding
     all other options.

`a'
     If this switch is present, `gnatfind' and `gnatxref' will parse
     the read-only files found in the library search path. Otherwise,
     these files will be ignored. This option can be used to protect
     Gnat sources or your own libraries from being parsed, thus making
     `gnatfind' and `gnatxref' much faster, and their output much
     smaller. Read-only here refers to access or permission status in
     the file system for the current user.

`aI`DIR''
     When looking for source files also look in directory DIR. The
     order in which source file search is undertaken is the same as for
     `gnatmake'.

`aO`DIR''
     When searching for library and object files, look in directory
     DIR. The order in which library files are searched is the same as
     for `gnatmake'.

`nostdinc'
     Do not look for sources in the system default directory.

`nostdlib'
     Do not look for library files in the system default directory.

`-ext=`extension''
     Specify an alternate ali file extension. The default is `ali' and
     other extensions (e.g. `gli' for C/C++ sources when using
     `-fdump-xref') may be specified via this switch. Note that if this
     switch overrides the default, which means that only the new
     extension will be considered.

`-RTS=`rts-path''
     Specifies the default location of the runtime library. Same
     meaning as the equivalent `gnatmake' flag (*note Switches for
     gnatmake: e2.).

`d'
     If this switch is set, then `gnatfind' will output the parent type
     reference for each matching derived types.

`e'
     By default, `gnatfind' accept the simple regular expression set for
     `pattern'. If this switch is set, then the pattern will be
     considered as full Unix-style regular expression.

`f'
     If this switch is set, the output file names will be preceded by
     their directory (if the file was found in the search path). If
     this switch is not set, the directory will not be printed.

`g'
     If this switch is set, information is output only for library-level
     entities, ignoring local entities. The use of this switch may
     accelerate `gnatfind' and `gnatxref'.

`I`DIR''
     Equivalent to `-aODIR -aIDIR'.

`p`FILE''
     Specify a project file (*note GNAT Project Manager: b.) to use.
     By default, `gnatxref' and `gnatfind' will try to locate a project
     file in the current directory.

     If a project file is either specified or found by the tools, then
     the content of the source directory and object directory lines are
     added as if they had been specified respectively by `-aI' and
     `-aO'.

`r'
     By default, `gnatfind' will output only the information about the
     declaration, body or type completion of the entities. If this
     switch is set, the `gnatfind' will locate every reference to the
     entities in the files specified on the command line (or in every
     file in the search path if no file is given on the command line).

`s'
     If this switch is set, then `gnatfind' will output the content of
     the Ada source file lines were the entity was found.

`t'
     If this switch is set, then `gnatfind' will output the type
     hierarchy for the specified type. It act like -d option but
     recursively from parent type to parent type. When this switch is
     set it is not possible to specify more than one file.

All these switches may be in any order on the command line, and may even
appear after the file names. They need not be separated by spaces, thus
you can say `gnatxref -ag' instead of `gnatxref -a -g'.

As stated previously, gnatfind will search in every directory in the
search path. You can force it to look only in the current directory if
you specify `*' at the end of the command line.


File: gnat_ugn.info,  Node: Project Files for gnatxref and gnatfind,  Next: Regular Expressions in gnatfind and gnatxref,  Prev: gnatfind Switches,  Up: The Cross-Referencing Tools gnatxref and gnatfind

7.3.3 Project Files for `gnatxref' and `gnatfind'
-------------------------------------------------

Project files allow a programmer to specify how to compile its
application, where to find sources, etc.  These files are used
primarily by GPS, but they can also be used by the two tools `gnatxref'
and `gnatfind'.

A project file name must end with `.gpr'. If a single one is present in
the current directory, then `gnatxref' and `gnatfind' will extract the
information from it. If multiple project files are found, none of them
is read, and you have to use the `-p' switch to specify the one you
want to use.

The following lines can be included, even though most of them have
default values which can be used in most cases.  The lines can be
entered in any order in the file.  Except for `src_dir' and `obj_dir',
you can only have one instance of each line. If you have multiple
instances, only the last one is taken into account.

   *
    `src_dir=DIR'
          [default: `"./"'].  Specifies a directory where to look for
          source files. Multiple `src_dir' lines can be specified and
          they will be searched in the order they are specified.

   *
    `obj_dir=DIR'
          [default: `"./"'].  Specifies a directory where to look for
          object and library files. Multiple `obj_dir' lines can be
          specified, and they will be searched in the order they are
          specified

   *
    `comp_opt=SWITCHES'
          [default: `""'].  Creates a variable which can be referred to
          subsequently by using the `${comp_opt}' notation. This is
          intended to store the default switches given to `gnatmake'
          and `gcc'.

   *
    `bind_opt=SWITCHES'
          [default: `""'].  Creates a variable which can be referred to
          subsequently by using the `$`bind_opt'' notation. This is
          intended to store the default switches given to `gnatbind'.

   *
    `link_opt=SWITCHES'
          [default: `""'].  Creates a variable which can be referred to
          subsequently by using the `$`link_opt'' notation. This is
          intended to store the default switches given to `gnatlink'.

   *
    `main=EXECUTABLE'
          [default: `""'].  Specifies the name of the executable for
          the application. This variable can be referred to in the
          following lines by using the ``${main'' notation.

   *
    `comp_cmd=COMMAND'
          [default: `"gcc -c -I${src_dir} -g -gnatq"'].  Specifies the
          command used to compile a single file in the application.

   *
    `make_cmd=COMMAND'
          [default: `"gnatmake ${main} -aI${src_dir} -aO${obj_dir} -g
          -gnatq -cargs ${comp_opt} -bargs ${bind_opt} -largs
          ${link_opt}"'].  Specifies the command used to recompile the
          whole application.

   *
    `run_cmd=COMMAND'
          [default: `"${main}"'].  Specifies the command used to run
          the application.

   *
    `debug_cmd=COMMAND'
          [default: `"gdb ${main}"'].  Specifies the command used to
          debug the application

`gnatxref' and `gnatfind' only take into account the `src_dir' and
`obj_dir' lines, and ignore the others.


File: gnat_ugn.info,  Node: Regular Expressions in gnatfind and gnatxref,  Next: Examples of gnatxref Usage,  Prev: Project Files for gnatxref and gnatfind,  Up: The Cross-Referencing Tools gnatxref and gnatfind

7.3.4 Regular Expressions in `gnatfind' and `gnatxref'
------------------------------------------------------

As specified in the section about `gnatfind', the pattern can be a
regular expression. Two kinds of regular expressions are recognized:

   *
    `Globbing pattern'
          These are the most common regular expression. They are the
          same as are generally used in a Unix shell command line, or
          in a DOS session.

          Here is a more formal grammar:

              regexp ::= term
              term   ::= elmt            -- matches elmt
              term   ::= elmt elmt       -- concatenation (elmt then elmt)
              term   ::= *               -- any string of 0 or more characters
              term   ::= ?               -- matches any character
              term   ::= [char {char}]   -- matches any character listed
              term   ::= [char - char]   -- matches any character in range

   *
    `Full regular expression'
          The second set of regular expressions is much more powerful.
          This is the type of regular expressions recognized by
          utilities such as `grep'.

          The following is the form of a regular expression, expressed
          in same BNF style as is found in the Ada Reference Manual:

              regexp ::= term {| term}   -- alternation (term or term ...)

              term ::= item {item}       -- concatenation (item then item)

              item ::= elmt              -- match elmt
              item ::= elmt *            -- zero or more elmt's
              item ::= elmt +            -- one or more elmt's
              item ::= elmt ?            -- matches elmt or nothing

              elmt ::= nschar            -- matches given character
              elmt ::= [nschar {nschar}]   -- matches any character listed
              elmt ::= [^ nschar {nschar}] -- matches any character not listed
              elmt ::= [char - char]     -- matches chars in given range
              elmt ::= \\ char            -- matches given character
              elmt ::= .                 -- matches any single character
              elmt ::= ( regexp )        -- parens used for grouping

              char ::= any character, including special characters
              nschar ::= any character except ()[].*+?^

          Here are a few examples:

              `abcde|fghi'
                    will match any of the two strings `abcde' and
                    `fghi',

              `abc*d'
                    will match any string like `abd', `abcd', `abccd',
                    `abcccd', and so on,

              `[a-z]+'
                    will match any string which has only lowercase
                    characters in it (and at least one character.


File: gnat_ugn.info,  Node: Examples of gnatxref Usage,  Next: Examples of gnatfind Usage,  Prev: Regular Expressions in gnatfind and gnatxref,  Up: The Cross-Referencing Tools gnatxref and gnatfind

7.3.5 Examples of `gnatxref' Usage
----------------------------------

* Menu:

* General Usage::
* Using gnatxref with vi::


File: gnat_ugn.info,  Node: General Usage,  Next: Using gnatxref with vi,  Up: Examples of gnatxref Usage

7.3.5.1 General Usage
.....................

For the following examples, we will consider the following units:

         main.ads:
         1: with Bar;
         2: package Main is
         3:     procedure Foo (B : in Integer);
         4:     C : Integer;
         5: private
         6:     D : Integer;
         7: end Main;

         main.adb:
         1: package body Main is
         2:     procedure Foo (B : in Integer) is
         3:     begin
         4:        C := B;
         5:        D := B;
         6:        Bar.Print (B);
         7:        Bar.Print (C);
         8:     end Foo;
         9: end Main;

         bar.ads:
         1: package Bar is
         2:     procedure Print (B : Integer);
         3: end bar;

The first thing to do is to recompile your application (for instance, in
that case just by doing a `gnatmake main', so that GNAT generates the
cross-referencing information.  You can then issue any of the following
commands:

        * `gnatxref main.adb' `gnatxref' generates cross-reference
          information for main.adb and every unit 'with'ed by main.adb.

          The output would be:

                   B                                                      Type: Integer
                     Decl: bar.ads           2:22
                   B                                                      Type: Integer
                     Decl: main.ads          3:20
                     Body: main.adb          2:20
                     Ref:  main.adb          4:13     5:13     6:19
                   Bar                                                    Type: Unit
                     Decl: bar.ads           1:9
                     Ref:  main.adb          6:8      7:8
                          main.ads           1:6
                   C                                                      Type: Integer
                     Decl: main.ads          4:5
                     Modi: main.adb          4:8
                     Ref:  main.adb          7:19
                   D                                                      Type: Integer
                     Decl: main.ads          6:5
                     Modi: main.adb          5:8
                   Foo                                                    Type: Unit
                     Decl: main.ads          3:15
                     Body: main.adb          2:15
                   Main                                                    Type: Unit
                     Decl: main.ads          2:9
                     Body: main.adb          1:14
                   Print                                                   Type: Unit
                     Decl: bar.ads           2:15
                     Ref:  main.adb          6:12     7:12

          This shows that the entity `Main' is declared in main.ads,
          line 2, column 9, its body is in main.adb, line 1, column 14
          and is not referenced any where.

          The entity `Print' is declared in bar.ads, line 2, column 15
          and it is referenced in main.adb, line 6 column 12 and line 7
          column 12.

        * `gnatxref package1.adb package2.ads' `gnatxref' will
          generates cross-reference information for package1.adb,
          package2.ads and any other package 'with'ed by any of these.


File: gnat_ugn.info,  Node: Using gnatxref with vi,  Prev: General Usage,  Up: Examples of gnatxref Usage

7.3.5.2 Using gnatxref with vi
..............................

`gnatxref' can generate a tags file output, which can be used directly
from `vi'. Note that the standard version of `vi' will not work
properly with overloaded symbols. Consider using another free
implementation of `vi', such as `vim'.

         $ gnatxref -v gnatfind.adb > tags

The following command will generate the tags file for `gnatfind' itself
(if the sources are in the search path!):

         $ gnatxref -v gnatfind.adb > tags

From `vi', you can then use the command `:tag `entity'' (replacing
`entity' by whatever you are looking for), and vi will display a new
file with the corresponding declaration of entity.


File: gnat_ugn.info,  Node: Examples of gnatfind Usage,  Prev: Examples of gnatxref Usage,  Up: The Cross-Referencing Tools gnatxref and gnatfind

7.3.6 Examples of `gnatfind' Usage
----------------------------------

   * `gnatfind -f xyz:main.adb' Find declarations for all entities xyz
     referenced at least once in main.adb. The references are search in
     every library file in the search path.

     The directories will be printed as well (as the `-f' switch is set)

     The output will look like:

              directory/main.ads:106:14: xyz <= declaration
              directory/main.adb:24:10: xyz <= body
              directory/foo.ads:45:23: xyz <= declaration

     I.e., one of the entities xyz found in main.adb is declared at
     line 12 of main.ads (and its body is in main.adb), and another one
     is declared at line 45 of foo.ads

   * `gnatfind -fs xyz:main.adb' This is the same command as the
     previous one, but `gnatfind' will display the content of the Ada
     source file lines.

     The output will look like:

         directory/main.ads:106:14: xyz <= declaration
            procedure xyz;
         directory/main.adb:24:10: xyz <= body
            procedure xyz is
         directory/foo.ads:45:23: xyz <= declaration
            xyz : Integer;

     This can make it easier to find exactly the location your are
     looking for.

   * `gnatfind -r "*x*":main.ads:123 foo.adb' Find references to all
     entities containing an x that are referenced on line 123 of
     main.ads.  The references will be searched only in main.ads and
     foo.adb.

   * `gnatfind main.ads:123' Find declarations and bodies for all
     entities that are referenced on line 123 of main.ads.

     This is the same as `gnatfind "*":main.adb:123`'

   * `gnatfind mydir/main.adb:123:45' Find the declaration for the
     entity referenced at column 45 in line 123 of file main.adb in
     directory mydir. Note that it is usual to omit the identifier name
     when the column is given, since the column position identifies a
     unique reference.

     The column has to be the beginning of the identifier, and should
     not point to any character in the middle of the identifier.


File: gnat_ugn.info,  Node: The Ada to HTML Converter gnathtml,  Prev: The Cross-Referencing Tools gnatxref and gnatfind,  Up: GNAT Utility Programs

7.4 The Ada to HTML Converter `gnathtml'
========================================

`gnathtml' is a Perl script that allows Ada source files to be browsed
using standard Web browsers. For installation information, see *note
Installing gnathtml: 1ed.

Ada reserved keywords are highlighted in a bold font and Ada comments in
a blue font. Unless your program was compiled with the gcc `-gnatx'
switch to suppress the generation of cross-referencing information, user
defined variables and types will appear in a different color; you will
be able to click on any identifier and go to its declaration.

* Menu:

* Invoking gnathtml::
* Installing gnathtml::


File: gnat_ugn.info,  Node: Invoking gnathtml,  Next: Installing gnathtml,  Up: The Ada to HTML Converter gnathtml

7.4.1 Invoking `gnathtml'
-------------------------

The command line is as follows:

         $ perl gnathtml.pl [`switches`] `ada-files`

You can specify as many Ada files as you want. `gnathtml' will generate
an html file for every ada file, and a global file called `index.htm'.
This file is an index of every identifier defined in the files.

The following switches are available:

`83'
     Only the Ada 83 subset of keywords will be highlighted.

`cc `color''
     This option allows you to change the color used for comments. The
     default value is green. The color argument can be any name
     accepted by html.

`d'
     If the Ada files depend on some other files (for instance through
     `with' clauses, the latter files will also be converted to html.
     Only the files in the user project will be converted to html, not
     the files in the run-time library itself.

`D'
     This command is the same as `-d' above, but `gnathtml' will also
     look for files in the run-time library, and generate html files
     for them.

`ext `extension''
     This option allows you to change the extension of the generated
     HTML files.  If you do not specify an extension, it will default
     to `htm'.

`f'
     By default, gnathtml will generate html links only for global
     entities ('with'ed units, global variables and types,...).  If you
     specify `-f' on the command line, then links will be generated for
     local entities too.

`l `number''
     If this switch is provided and `number' is not 0, then `gnathtml'
     will number the html files every `number' line.

`I `dir''
     Specify a directory to search for library files (`.ALI' files) and
     source files. You can provide several -I switches on the command
     line, and the directories will be parsed in the order of the
     command line.

`o `dir''
     Specify the output directory for html files. By default, gnathtml
     will saved the generated html files in a subdirectory named
     `html/'.

`p `file''
     If you are using Emacs and the most recent Emacs Ada mode, which
     provides a full Integrated Development Environment for compiling,
     checking, running and debugging applications, you may use `.gpr'
     files to give the directories where Emacs can find sources and
     object files.

     Using this switch, you can tell gnathtml to use these files.  This
     allows you to get an html version of your application, even if it
     is spread over multiple directories.

`sc `color''
     This switch allows you to change the color used for symbol
     definitions.  The default value is red. The color argument can be
     any name accepted by html.

`t `file''
     This switch provides the name of a file. This file contains a list
     of file names to be converted, and the effect is exactly as though
     they had appeared explicitly on the command line. This is the
     recommended way to work around the command line length limit on
     some systems.


File: gnat_ugn.info,  Node: Installing gnathtml,  Prev: Invoking gnathtml,  Up: The Ada to HTML Converter gnathtml

7.4.2 Installing `gnathtml'
---------------------------

`Perl' needs to be installed on your machine to run this script.
`Perl' is freely available for almost every architecture and operating
system via the Internet.

On Unix systems, you  may want to modify  the  first line of  the script
`gnathtml',  to explicitly  specify  where Perl is located. The syntax
of this line is:

         #!full_path_name_to_perl

Alternatively, you may run the script using the following command line:

         $ perl gnathtml.pl [`switches`] `files`


File: gnat_ugn.info,  Node: GNAT and Program Execution,  Next: Platform-Specific Information,  Prev: GNAT Utility Programs,  Up: Top

8 GNAT and Program Execution
****************************

This chapter covers several topics:

   * *note Running and Debugging Ada Programs: 1f3.

   * *note Code Coverage and Profiling: 1f4.

   * *note Improving Performance: 1f5.

   * *note Overflow Check Handling in GNAT: 1f6.

   * *note Performing Dimensionality Analysis in GNAT: 1f7.

   * *note Stack Related Facilities: 1f8.

   * *note Memory Management Issues: 1f9.

* Menu:

* Running and Debugging Ada Programs::
* Code Coverage and Profiling::
* Improving Performance::
* Overflow Check Handling in GNAT::
* Performing Dimensionality Analysis in GNAT::
* Stack Related Facilities::
* Memory Management Issues::


File: gnat_ugn.info,  Node: Running and Debugging Ada Programs,  Next: Code Coverage and Profiling,  Up: GNAT and Program Execution

8.1 Running and Debugging Ada Programs
======================================

This section discusses how to debug Ada programs.

An incorrect Ada program may be handled in three ways by the GNAT
compiler:

   * The illegality may be a violation of the static semantics of Ada.
     In that case GNAT diagnoses the constructs in the program that are
     illegal.  It is then a straightforward matter for the user to
     modify those parts of the program.

   * The illegality may be a violation of the dynamic semantics of Ada.
     In that case the program compiles and executes, but may generate
     incorrect results, or may terminate abnormally with some exception.

   * When presented with a program that contains convoluted errors, GNAT
     itself may terminate abnormally without providing full diagnostics
     on the incorrect user program.

* Menu:

* The GNAT Debugger GDB::
* Running GDB::
* Introduction to GDB Commands::
* Using Ada Expressions::
* Calling User-Defined Subprograms::
* Using the next Command in a Function::
* Stopping When Ada Exceptions Are Raised::
* Ada Tasks::
* Debugging Generic Units::
* Remote Debugging with gdbserver::
* GNAT Abnormal Termination or Failure to Terminate::
* Naming Conventions for GNAT Source Files::
* Getting Internal Debugging Information::
* Stack Traceback::


File: gnat_ugn.info,  Node: The GNAT Debugger GDB,  Next: Running GDB,  Up: Running and Debugging Ada Programs

8.1.1 The GNAT Debugger GDB
---------------------------

`GDB' is a general purpose, platform-independent debugger that can be
used to debug mixed-language programs compiled with `gcc', and in
particular is capable of debugging Ada programs compiled with GNAT. The
latest versions of `GDB' are Ada-aware and can handle complex Ada data
structures.

See `Debugging with GDB', for full details on the usage of `GDB',
including a section on its usage on programs. This manual should be
consulted for full details. The section that follows is a brief
introduction to the philosophy and use of `GDB'.

When GNAT programs are compiled, the compiler optionally writes
debugging information into the generated object file, including
information on line numbers, and on declared types and variables. This
information is separate from the generated code. It makes the object
files considerably larger, but it does not add to the size of the
actual executable that will be loaded into memory, and has no impact on
run-time performance. The generation of debug information is triggered
by the use of the -g switch in the `gcc' or `gnatmake' command used to
carry out the compilations. It is important to emphasize that the use
of these options does not change the generated code.

The debugging information is written in standard system formats that
are used by many tools, including debuggers and profilers. The format
of the information is typically designed to describe C types and
semantics, but GNAT implements a translation scheme which allows full
details about Ada types and variables to be encoded into these standard
C formats. Details of this encoding scheme may be found in the file
exp_dbug.ads in the GNAT source distribution. However, the details of
this encoding are, in general, of no interest to a user, since `GDB'
automatically performs the necessary decoding.

When a program is bound and linked, the debugging information is
collected from the object files, and stored in the executable image of
the program. Again, this process significantly increases the size of
the generated executable file, but it does not increase the size of the
executable program itself. Furthermore, if this program is run in the
normal manner, it runs exactly as if the debug information were not
present, and takes no more actual memory.

However, if the program is run under control of `GDB', the debugger is
activated.  The image of the program is loaded, at which point it is
ready to run.  If a run command is given, then the program will run
exactly as it would have if `GDB' were not present. This is a crucial
part of the `GDB' design philosophy.  `GDB' is entirely non-intrusive
until a breakpoint is encountered.  If no breakpoint is ever hit, the
program will run exactly as it would if no debugger were present. When
a breakpoint is hit, `GDB' accesses the debugging information and can
respond to user commands to inspect variables, and more generally to
report on the state of execution.


File: gnat_ugn.info,  Node: Running GDB,  Next: Introduction to GDB Commands,  Prev: The GNAT Debugger GDB,  Up: Running and Debugging Ada Programs

8.1.2 Running GDB
-----------------

This section describes how to initiate the debugger.

The debugger can be launched from a `GPS' menu or directly from the
command line. The description below covers the latter use.  All the
commands shown can be used in the `GPS' debug console window, but there
are usually more GUI-based ways to achieve the same effect.

The command to run `GDB' is

         $ gdb program

where `program' is the name of the executable file. This activates the
debugger and results in a prompt for debugger commands.  The simplest
command is simply `run', which causes the program to run exactly as if
the debugger were not present. The following section describes some of
the additional commands that can be given to `GDB'.


File: gnat_ugn.info,  Node: Introduction to GDB Commands,  Next: Using Ada Expressions,  Prev: Running GDB,  Up: Running and Debugging Ada Programs

8.1.3 Introduction to GDB Commands
----------------------------------

`GDB' contains a large repertoire of commands.  See `Debugging with
GDB' for extensive documentation on the use of these commands, together
with examples of their use. Furthermore, the command `help' invoked
from within GDB activates a simple help facility which summarizes the
available commands and their options.  In this section we summarize a
few of the most commonly used commands to give an idea of what `GDB' is
about. You should create a simple program with debugging information
and experiment with the use of these `GDB' commands on the program as
you read through the following section.

   *
    `set args `arguments`'
          The `arguments' list above is a list of arguments to be
          passed to the program on a subsequent run command, just as
          though the arguments had been entered on a normal invocation
          of the program. The `set args' command is not needed if the
          program does not require arguments.

   *
    `run'
          The `run' command causes execution of the program to start
          from the beginning. If the program is already running, that
          is to say if you are currently positioned at a breakpoint,
          then a prompt will ask for confirmation that you want to
          abandon the current execution and restart.

   *
    `breakpoint `location`'
          The breakpoint command sets a breakpoint, that is to say a
          point at which execution will halt and `GDB' will await
          further commands. `location' is either a line number within a
          file, given in the format `file:linenumber', or it is the
          name of a subprogram. If you request that a breakpoint be set
          on a subprogram that is overloaded, a prompt will ask you to
          specify on which of those subprograms you want to breakpoint.
          You can also specify that all of them should be breakpointed.
          If the program is run and execution encounters the
          breakpoint, then the program stops and `GDB' signals that the
          breakpoint was encountered by printing the line of code
          before which the program is halted.

   *
    `catch exception `name`'
          This command causes the program execution to stop whenever
          exception `name' is raised.  If `name' is omitted, then the
          execution is suspended when any exception is raised.

   *
    `print `expression`'
          This will print the value of the given expression. Most simple
          Ada expression formats are properly handled by `GDB', so the
          expression can contain function calls, variables, operators,
          and attribute references.

   *
    `continue'
          Continues execution following a breakpoint, until the next
          breakpoint or the termination of the program.

   *
    `step'
          Executes a single line after a breakpoint. If the next
          statement is a subprogram call, execution continues into (the
          first statement of) the called subprogram.

   *
    `next'
          Executes a single line. If this line is a subprogram call,
          executes and returns from the call.

   *
    `list'
          Lists a few lines around the current source location. In
          practice, it is usually more convenient to have a separate
          edit window open with the relevant source file displayed.
          Successive applications of this command print subsequent
          lines. The command can be given an argument which is a line
          number, in which case it displays a few lines around the
          specified one.

   *
    `backtrace'
          Displays a backtrace of the call chain. This command is
          typically used after a breakpoint has occurred, to examine
          the sequence of calls that leads to the current breakpoint.
          The display includes one line for each activation record
          (frame) corresponding to an active subprogram.

   *
    `up'
          At a breakpoint, `GDB' can display the values of variables
          local to the current frame. The command `up' can be used to
          examine the contents of other active frames, by moving the
          focus up the stack, that is to say from callee to caller, one
          frame at a time.

   *
    `down'
          Moves the focus of `GDB' down from the frame currently being
          examined to the frame of its callee (the reverse of the
          previous command),

   *
    `frame `n`'
          Inspect the frame with the given number. The value 0 denotes
          the frame of the current breakpoint, that is to say the top
          of the call stack.

   *
    `kill'
          Kills the child process in which the program is running under
          GDB.  This may be useful for several purposes:

             * It allows you to recompile and relink your program,
               since on many systems you cannot regenerate an
               executable file while it is running in a process.

             * You can run your program outside the debugger, on
               systems that do not permit executing a program outside
               GDB while breakpoints are set within GDB.

             * It allows you to debug a core dump rather than a running
               process.

The above list is a very short introduction to the commands that `GDB'
provides. Important additional capabilities, including conditional
breakpoints, the ability to execute command sequences on a breakpoint,
the ability to debug at the machine instruction level and many other
features are described in detail in `Debugging with GDB'.  Note that
most commands can be abbreviated (for example, c for continue, bt for
backtrace).


File: gnat_ugn.info,  Node: Using Ada Expressions,  Next: Calling User-Defined Subprograms,  Prev: Introduction to GDB Commands,  Up: Running and Debugging Ada Programs

8.1.4 Using Ada Expressions
---------------------------

`GDB' supports a fairly large subset of Ada expression syntax, with some
extensions. The philosophy behind the design of this subset is

        * That `GDB' should provide basic literals and access to
          operations for arithmetic, dereferencing, field selection,
          indexing, and subprogram calls, leaving more sophisticated
          computations to subprograms written into the program (which
          therefore may be called from `GDB').

        * That type safety and strict adherence to Ada language
          restrictions are not particularly relevant in a debugging
          context.

        * That brevity is important to the `GDB' user.

Thus, for brevity, the debugger acts as if there were implicit `with'
and `use' clauses in effect for all user-written packages, thus making
it unnecessary to fully qualify most names with their packages,
regardless of context. Where this causes ambiguity, `GDB' asks the
user's intent.

For details on the supported Ada syntax, see `Debugging with GDB'.


File: gnat_ugn.info,  Node: Calling User-Defined Subprograms,  Next: Using the next Command in a Function,  Prev: Using Ada Expressions,  Up: Running and Debugging Ada Programs

8.1.5 Calling User-Defined Subprograms
--------------------------------------

An important capability of `GDB' is the ability to call user-defined
subprograms while debugging. This is achieved simply by entering a
subprogram call statement in the form:

         call subprogram-name (parameters)

The keyword `call' can be omitted in the normal case where the
`subprogram-name' does not coincide with any of the predefined `GDB'
commands.

The effect is to invoke the given subprogram, passing it the list of
parameters that is supplied. The parameters can be expressions and can
include variables from the program being debugged. The subprogram must
be defined at the library level within your program, and `GDB' will
call the subprogram within the environment of your program execution
(which means that the subprogram is free to access or even modify
variables within your program).

The most important use of this facility is in allowing the inclusion of
debugging routines that are tailored to particular data structures in
your program. Such debugging routines can be written to provide a
suitably high-level description of an abstract type, rather than a
low-level dump of its physical layout. After all, the standard `GDB
print' command only knows the physical layout of your types, not their
abstract meaning. Debugging routines can provide information at the
desired semantic level and are thus enormously useful.

For example, when debugging GNAT itself, it is crucial to have access to
the contents of the tree nodes used to represent the program internally.
But tree nodes are represented simply by an integer value (which in turn
is an index into a table of nodes).  Using the `print' command on a
tree node would simply print this integer value, which is not very
useful. But the PN routine (defined in file treepr.adb in the GNAT
sources) takes a tree node as input, and displays a useful high level
representation of the tree node, which includes the syntactic category
of the node, its position in the source, the integers that denote
descendant nodes and parent node, as well as varied semantic
information. To study this example in more detail, you might want to
look at the body of the PN procedure in the stated file.

Another useful application of this capability is to deal with
situations of complex data which are not handled suitably by GDB. For
example, if you specify Convention Fortran for a multi-dimensional
array, GDB does not know that the ordering of array elements has been
switched and will not properly address the array elements. In such a
case, instead of trying to print the elements directly from GDB, you
can write a callable procedure that prints the elements in the desired
format.


File: gnat_ugn.info,  Node: Using the next Command in a Function,  Next: Stopping When Ada Exceptions Are Raised,  Prev: Calling User-Defined Subprograms,  Up: Running and Debugging Ada Programs

8.1.6 Using the `next' Command in a Function
--------------------------------------------

When you use the `next' command in a function, the current source
location will advance to the next statement as usual. A special case
arises in the case of a `return' statement.

Part of the code for a return statement is the 'epilogue' of the
function.  This is the code that returns to the caller. There is only
one copy of this epilogue code, and it is typically associated with the
last return statement in the function if there is more than one return.
In some implementations, this epilogue is associated with the first
statement of the function.

The result is that if you use the `next' command from a return
statement that is not the last return statement of the function you may
see a strange apparent jump to the last return statement or to the
start of the function. You should simply ignore this odd jump.  The
value returned is always that from the first return statement that was
stepped through.


File: gnat_ugn.info,  Node: Stopping When Ada Exceptions Are Raised,  Next: Ada Tasks,  Prev: Using the next Command in a Function,  Up: Running and Debugging Ada Programs

8.1.7 Stopping When Ada Exceptions Are Raised
---------------------------------------------

You can set catchpoints that stop the program execution when your
program raises selected exceptions.

   *
    `catch exception'
          Set a catchpoint that stops execution whenever (any task in
          the) program raises any exception.

   *
    `catch exception `name`'
          Set a catchpoint that stops execution whenever (any task in
          the) program raises the exception `name'.

   *
    `catch exception unhandled'
          Set a catchpoint that stops executing whenever (any task in
          the) program raises an exception for which there is no
          handler.

   *
    `info exceptions', `info exceptions `regexp`'
          The `info exceptions' command permits the user to examine all
          defined exceptions within Ada programs. With a regular
          expression, `regexp', as argument, prints out only those
          exceptions whose name matches `regexp'.


File: gnat_ugn.info,  Node: Ada Tasks,  Next: Debugging Generic Units,  Prev: Stopping When Ada Exceptions Are Raised,  Up: Running and Debugging Ada Programs

8.1.8 Ada Tasks
---------------

`GDB' allows the following task-related commands:

   *
    `info tasks'
          This command shows a list of current Ada tasks, as in the
          following example:

              (gdb) info tasks
                ID       TID P-ID   Thread Pri State                 Name
                 1   8088000   0   807e000  15 Child Activation Wait main_task
                 2   80a4000   1   80ae000  15 Accept/Select Wait    b
                 3   809a800   1   80a4800  15 Child Activation Wait a
              *  4   80ae800   3   80b8000  15 Running               c

          In this listing, the asterisk before the first task indicates
          it to be the currently running task. The first column lists
          the task ID that is used to refer to tasks in the following
          commands.

   * `break `linespec` task `taskid`', `break `linespec` task `taskid`
     if ...'

          These commands are like the `break ... thread ...'.
          `linespec' specifies source lines.

          Use the qualifier `task `taskid'' with a breakpoint command
          to specify that you only want `GDB' to stop the program when a
          particular Ada task reaches this breakpoint. `taskid' is one
          of the numeric task identifiers assigned by `GDB', shown in
          the first column of the `info tasks' display.

          If you do not specify `task `taskid'' when you set a
          breakpoint, the breakpoint applies to `all' tasks of your
          program.

          You can use the `task' qualifier on conditional breakpoints as
          well; in this case, place `task `taskid'' before the
          breakpoint condition (before the `if').

   * `task `taskno`'

          This command allows switching to the task referred by
          `taskno'. In particular, this allows browsing of the
          backtrace of the specified task. It is advisable to switch
          back to the original task before continuing execution
          otherwise the scheduling of the program may be perturbed.

For more detailed information on the tasking support, see `Debugging
with GDB'.


File: gnat_ugn.info,  Node: Debugging Generic Units,  Next: Remote Debugging with gdbserver,  Prev: Ada Tasks,  Up: Running and Debugging Ada Programs

8.1.9 Debugging Generic Units
-----------------------------

GNAT always uses code expansion for generic instantiation. This means
that each time an instantiation occurs, a complete copy of the original
code is made, with appropriate substitutions of formals by actuals.

It is not possible to refer to the original generic entities in `GDB',
but it is always possible to debug a particular instance of a generic,
by using the appropriate expanded names. For example, if we have

         procedure g is

            generic package k is
               procedure kp (v1 : in out integer);
            end k;

            package body k is
               procedure kp (v1 : in out integer) is
               begin
                  v1 := v1 + 1;
               end kp;
            end k;

            package k1 is new k;
            package k2 is new k;

            var : integer := 1;

         begin
            k1.kp (var);
            k2.kp (var);
            k1.kp (var);
            k2.kp (var);
         end;

Then to break on a call to procedure kp in the k2 instance, simply use
the command:

         (gdb) break g.k2.kp

When the breakpoint occurs, you can step through the code of the
instance in the normal manner and examine the values of local
variables, as for other units.


File: gnat_ugn.info,  Node: Remote Debugging with gdbserver,  Next: GNAT Abnormal Termination or Failure to Terminate,  Prev: Debugging Generic Units,  Up: Running and Debugging Ada Programs

8.1.10 Remote Debugging with gdbserver
--------------------------------------

On platforms where gdbserver is supported, it is possible to use this
tool to debug your application remotely.  This can be useful in
situations where the program needs to be run on a target host that is
different from the host used for development, particularly when the
target has a limited amount of resources (either CPU and/or memory).

To do so, start your program using gdbserver on the target machine.
gdbserver then automatically suspends the execution of your program at
its entry point, waiting for a debugger to connect to it.  The
following commands starts an application and tells gdbserver to wait
for a connection with the debugger on localhost port 4444.

         $ gdbserver localhost:4444 program
         Process program created; pid = 5685
         Listening on port 4444

Once gdbserver has started listening, we can tell the debugger to
establish a connection with this gdbserver, and then start the same
debugging session as if the program was being debugged on the same
host, directly under the control of GDB.

         $ gdb program
         (gdb) target remote targethost:4444
         Remote debugging using targethost:4444
         0x00007f29936d0af0 in ?? () from /lib64/ld-linux-x86-64.so.
         (gdb) b foo.adb:3
         Breakpoint 1 at 0x401f0c: file foo.adb, line 3.
         (gdb) continue
         Continuing.

         Breakpoint 1, foo () at foo.adb:4
         4       end foo;

It is also possible to use gdbserver to attach to an already running
program, in which case the execution of that program is simply suspended
until the connection between the debugger and gdbserver is established.

For more information on how to use gdbserver, see the `Using the
gdbserver Program' section in `Debugging with GDB'.  GNAT provides
support for gdbserver on x86-linux, x86-windows and x86_64-linux.


File: gnat_ugn.info,  Node: GNAT Abnormal Termination or Failure to Terminate,  Next: Naming Conventions for GNAT Source Files,  Prev: Remote Debugging with gdbserver,  Up: Running and Debugging Ada Programs

8.1.11 GNAT Abnormal Termination or Failure to Terminate
--------------------------------------------------------

When presented with programs that contain serious errors in syntax or
semantics, GNAT may on rare occasions  experience problems in
operation, such as aborting with a segmentation fault or illegal memory
access, raising an internal exception, terminating abnormally, or
failing to terminate at all.  In such cases, you can activate various
features of GNAT that can help you pinpoint the construct in your
program that is the likely source of the problem.

The following strategies are presented in increasing order of
difficulty, corresponding to your experience in using GNAT and your
familiarity with compiler internals.

   * Run `gcc' with the `-gnatf'. This first switch causes all errors
     on a given line to be reported. In its absence, only the first
     error on a line is displayed.

     The `-gnatdO' switch causes errors to be displayed as soon as they
     are encountered, rather than after compilation is terminated. If
     GNAT terminates prematurely or goes into an infinite loop, the
     last error message displayed may help to pinpoint the culprit.

   * Run `gcc' with the `-v (verbose)' switch. In this mode, `gcc'
     produces ongoing information about the progress of the compilation
     and provides the name of each procedure as code is generated. This
     switch allows you to find which Ada procedure was being compiled
     when it encountered a code generation problem.

   * Run `gcc' with the `-gnatdc' switch. This is a GNAT specific
     switch that does for the front-end what `-v' does for the back
     end. The system prints the name of each unit, either a compilation
     unit or nested unit, as it is being analyzed.

   * Finally, you can start `gdb' directly on the `gnat1' executable.
     `gnat1' is the front-end of GNAT, and can be run independently
     (normally it is just called from `gcc'). You can use `gdb' on
     `gnat1' as you would on a C program (but *note The GNAT Debugger
     GDB: 1fa. for caveats). The `where' command is the first line of
     attack; the variable `lineno' (seen by `print lineno'), used by
     the second phase of `gnat1' and by the `gcc' backend, indicates
     the source line at which the execution stopped, and `input_file
     name' indicates the name of the source file.


File: gnat_ugn.info,  Node: Naming Conventions for GNAT Source Files,  Next: Getting Internal Debugging Information,  Prev: GNAT Abnormal Termination or Failure to Terminate,  Up: Running and Debugging Ada Programs

8.1.12 Naming Conventions for GNAT Source Files
-----------------------------------------------

In order to examine the workings of the GNAT system, the following
brief description of its organization may be helpful:

   * Files with prefix `sc' contain the lexical scanner.

   * All files prefixed with `par' are components of the parser. The
     numbers correspond to chapters of the Ada Reference Manual. For
     example, parsing of select statements can be found in
     `par-ch9.adb'.

   * All files prefixed with `sem' perform semantic analysis. The
     numbers correspond to chapters of the Ada standard. For example,
     all issues involving context clauses can be found in
     `sem_ch10.adb'. In addition, some features of the language require
     sufficient special processing to justify their own semantic files:
     sem_aggr for aggregates, sem_disp for dynamic dispatching, etc.

   * All files prefixed with `exp' perform normalization and expansion
     of the intermediate representation (abstract syntax tree, or AST).
     these files use the same numbering scheme as the parser and
     semantics files.  For example, the construction of record
     initialization procedures is done in `exp_ch3.adb'.

   * The files prefixed with `bind' implement the binder, which
     verifies the consistency of the compilation, determines an order of
     elaboration, and generates the bind file.

   * The files `atree.ads' and `atree.adb' detail the low-level data
     structures used by the front-end.

   * The files `sinfo.ads' and `sinfo.adb' detail the structure of the
     abstract syntax tree as produced by the parser.

   * The files `einfo.ads' and `einfo.adb' detail the attributes of all
     entities, computed during semantic analysis.

   * Library management issues are dealt with in files with prefix
     `lib'.

   * Ada files with the prefix `a-' are children of `Ada', as defined
     in Annex A.

   * Files with prefix `i-' are children of `Interfaces', as defined in
     Annex B.

   * Files with prefix `s-' are children of `System'. This includes
     both language-defined children and GNAT run-time routines.

   * Files with prefix `g-' are children of `GNAT'. These are useful
     general-purpose packages, fully documented in their specs. All the
     other `.c' files are modifications of common `gcc' files.


File: gnat_ugn.info,  Node: Getting Internal Debugging Information,  Next: Stack Traceback,  Prev: Naming Conventions for GNAT Source Files,  Up: Running and Debugging Ada Programs

8.1.13 Getting Internal Debugging Information
---------------------------------------------

Most compilers have internal debugging switches and modes. GNAT does
also, except GNAT internal debugging switches and modes are not secret.
A summary and full description of all the compiler and binder debug
flags are in the file `debug.adb'. You must obtain the sources of the
compiler to see the full detailed effects of these flags.

The switches that print the source of the program (reconstructed from
the internal tree) are of general interest for user programs, as are the
options to print the full internal tree, and the entity table (the
symbol table information). The reconstructed source provides a readable
version of the program after the front-end has completed analysis and
expansion, and is useful when studying the performance of specific
constructs.  For example, constraint checks are indicated, complex
aggregates are replaced with loops and assignments, and tasking
primitives are replaced with run-time calls.


File: gnat_ugn.info,  Node: Stack Traceback,  Prev: Getting Internal Debugging Information,  Up: Running and Debugging Ada Programs

8.1.14 Stack Traceback
----------------------

Traceback is a mechanism to display the sequence of subprogram calls
that leads to a specified execution point in a program. Often (but not
always) the execution point is an instruction at which an exception has
been raised.  This mechanism is also known as `stack unwinding' because
it obtains its information by scanning the run-time stack and
recovering the activation records of all active subprograms. Stack
unwinding is one of the most important tools for program debugging.

The first entry stored in traceback corresponds to the deepest calling
level, that is to say the subprogram currently executing the instruction
from which we want to obtain the traceback.

Note that there is no runtime performance penalty when stack traceback
is enabled, and no exception is raised during program execution.

* Menu:

* Non-Symbolic Traceback::
* Symbolic Traceback::


File: gnat_ugn.info,  Node: Non-Symbolic Traceback,  Next: Symbolic Traceback,  Up: Stack Traceback

8.1.14.1 Non-Symbolic Traceback
...............................

Note: this feature is not supported on all platforms. See
`GNAT.Traceback' spec in `g-traceb.ads' for a complete list of
supported platforms.

Tracebacks From an Unhandled Exception
......................................

A runtime non-symbolic traceback is a list of addresses of call
instructions.  To enable this feature you must use the `-E' `gnatbind's
option. With this option a stack traceback is stored as part of
exception information. You can retrieve this information using the
`addr2line' tool.

Here is a simple example:

         procedure STB is

            procedure P1 is
            begin
               raise Constraint_Error;
            end P1;

            procedure P2 is
            begin
               P1;
            end P2;

         begin
            P2;
         end STB;

         $ gnatmake stb -bargs -E
         $ stb

         Execution terminated by unhandled exception
         Exception name: CONSTRAINT_ERROR
         Message: stb.adb:5
         Call stack traceback locations:
         0x401373 0x40138b 0x40139c 0x401335 0x4011c4 0x4011f1 0x77e892a4

As we see the traceback lists a sequence of addresses for the unhandled
exception `CONSTRAINT_ERROR' raised in procedure P1. It is easy to
guess that this exception come from procedure P1. To translate these
addresses into the source lines where the calls appear, the `addr2line'
tool, described below, is invaluable. The use of this tool requires the
program to be compiled with debug information.

         $ gnatmake -g stb -bargs -E
         $ stb

         Execution terminated by unhandled exception
         Exception name: CONSTRAINT_ERROR
         Message: stb.adb:5
         Call stack traceback locations:
         0x401373 0x40138b 0x40139c 0x401335 0x4011c4 0x4011f1 0x77e892a4

         $ addr2line --exe=stb 0x401373 0x40138b 0x40139c 0x401335 0x4011c4
            0x4011f1 0x77e892a4

         00401373 at d:/stb/stb.adb:5
         0040138B at d:/stb/stb.adb:10
         0040139C at d:/stb/stb.adb:14
         00401335 at d:/stb/b~stb.adb:104
         004011C4 at /build/.../crt1.c:200
         004011F1 at /build/.../crt1.c:222
         77E892A4 in ?? at ??:0

The `addr2line' tool has several other useful options:

      `--functions'                to get the function name corresponding to any location
     `--demangle=gnat'            to use the gnat decoding mode for the function names.  Note
                                  that for binutils version 2.9.x the option is simply
                                  `--demangle'.

         $ addr2line --exe=stb --functions --demangle=gnat 0x401373 0x40138b
            0x40139c 0x401335 0x4011c4 0x4011f1

         00401373 in stb.p1 at d:/stb/stb.adb:5
         0040138B in stb.p2 at d:/stb/stb.adb:10
         0040139C in stb at d:/stb/stb.adb:14
         00401335 in main at d:/stb/b~stb.adb:104
         004011C4 in <__mingw_CRTStartup> at /build/.../crt1.c:200
         004011F1 in <mainCRTStartup> at /build/.../crt1.c:222

From this traceback we can see that the exception was raised in
`stb.adb' at line 5, which was reached from a procedure call in
`stb.adb' at line 10, and so on. The `b~std.adb' is the binder file,
which contains the call to the main program.  *note Running gnatbind:
123. The remaining entries are assorted runtime routines, and the
output will vary from platform to platform.

It is also possible to use `GDB' with these traceback addresses to debug
the program. For example, we can break at a given code location, as
reported in the stack traceback:

         $ gdb -nw stb

Furthermore, this feature is not implemented inside Windows DLL. Only
the non-symbolic traceback is reported in this case.

         (gdb) break *0x401373
         Breakpoint 1 at 0x401373: file stb.adb, line 5.

It is important to note that the stack traceback addresses do not
change when debug information is included. This is particularly useful
because it makes it possible to release software without debug
information (to minimize object size), get a field report that includes
a stack traceback whenever an internal bug occurs, and then be able to
retrieve the sequence of calls with the same program compiled with
debug information.

Tracebacks From Exception Occurrences
.....................................

Non-symbolic tracebacks are obtained by using the `-E' binder argument.
The stack traceback is attached to the exception information string,
and can be retrieved in an exception handler within the Ada program, by
means of the Ada facilities defined in `Ada.Exceptions'. Here is a
simple example:

         with Ada.Text_IO;
         with Ada.Exceptions;

         procedure STB is

            use Ada;
            use Ada.Exceptions;

            procedure P1 is
               K : Positive := 1;
            begin
               K := K - 1;
            exception
               when E : others =>
                  Text_IO.Put_Line (Exception_Information (E));
            end P1;

            procedure P2 is
            begin
               P1;
            end P2;

         begin
            P2;
         end STB;

This program will output:

         $ stb

         Exception name: CONSTRAINT_ERROR
         Message: stb.adb:12
         Call stack traceback locations:
         0x4015e4 0x401633 0x401644 0x401461 0x4011c4 0x4011f1 0x77e892a4

Tracebacks From Anywhere in a Program
.....................................

It is also possible to retrieve a stack traceback from anywhere in a
program. For this you need to use the `GNAT.Traceback' API. This
package includes a procedure called `Call_Chain' that computes a
complete stack traceback, as well as useful display procedures
described below. It is not necessary to use the `-E gnatbind' option in
this case, because the stack traceback mechanism is invoked explicitly.

In the following example we compute a traceback at a specific location
in the program, and we display it using `GNAT.Debug_Utilities.Image' to
convert addresses to strings:

         with Ada.Text_IO;
         with GNAT.Traceback;
         with GNAT.Debug_Utilities;

         procedure STB is

            use Ada;
            use GNAT;
            use GNAT.Traceback;

            procedure P1 is
               TB  : Tracebacks_Array (1 .. 10);
               --  We are asking for a maximum of 10 stack frames.
               Len : Natural;
               --  Len will receive the actual number of stack frames returned.
            begin
               Call_Chain (TB, Len);

               Text_IO.Put ("In STB.P1 : ");

               for K in 1 .. Len loop
                  Text_IO.Put (Debug_Utilities.Image (TB (K)));
                  Text_IO.Put (' ');
               end loop;

               Text_IO.New_Line;
            end P1;

            procedure P2 is
            begin
               P1;
            end P2;

         begin
            P2;
         end STB;

         $ gnatmake -g stb
         $ stb

         In STB.P1 : 16#0040_F1E4# 16#0040_14F2# 16#0040_170B# 16#0040_171C#
         16#0040_1461# 16#0040_11C4# 16#0040_11F1# 16#77E8_92A4#

You can then get further information by invoking the `addr2line' tool
as described earlier (note that the hexadecimal addresses need to be
specified in C format, with a leading '0x').


File: gnat_ugn.info,  Node: Symbolic Traceback,  Prev: Non-Symbolic Traceback,  Up: Stack Traceback

8.1.14.2 Symbolic Traceback
...........................

A symbolic traceback is a stack traceback in which procedure names are
associated with each code location.

Note that this feature is not supported on all platforms. See
`GNAT.Traceback.Symbolic' spec in `g-trasym.ads' for a complete list of
currently supported platforms.

Note that the symbolic traceback requires that the program be compiled
with debug information. If it is not compiled with debug information
only the non-symbolic information will be valid.

Tracebacks From Exception Occurrences
.....................................

Here is an example:

         with Ada.Text_IO;
         with GNAT.Traceback.Symbolic;

         procedure STB is

            procedure P1 is
            begin
               raise Constraint_Error;
            end P1;

            procedure P2 is
            begin
               P1;
            end P2;

            procedure P3 is
            begin
               P2;
            end P3;

         begin
            P3;
         exception
            when E : others =>
               Ada.Text_IO.Put_Line (GNAT.Traceback.Symbolic.Symbolic_Traceback (E));
         end STB;

         $ gnatmake -g .\stb -bargs -E
         $ stb

         0040149F in stb.p1 at stb.adb:8
         004014B7 in stb.p2 at stb.adb:13
         004014CF in stb.p3 at stb.adb:18
         004015DD in ada.stb at stb.adb:22
         00401461 in main at b~stb.adb:168
         004011C4 in __mingw_CRTStartup at crt1.c:200
         004011F1 in mainCRTStartup at crt1.c:222
         77E892A4 in ?? at ??:0

In the above example the `.\' syntax in the `gnatmake' command is
currently required by `addr2line' for files that are in the current
working directory.  Moreover, the exact sequence of linker options may
vary from platform to platform.  The above `-largs' section is for
Windows platforms. By contrast, under Unix there is no need for the
`-largs' section.  Differences across platforms are due to details of
linker implementation.

Tracebacks From Anywhere in a Program
.....................................

It is possible to get a symbolic stack traceback from anywhere in a
program, just as for non-symbolic tracebacks.  The first step is to
obtain a non-symbolic traceback, and then call `Symbolic_Traceback' to
compute the symbolic information. Here is an example:

         with Ada.Text_IO;
         with GNAT.Traceback;
         with GNAT.Traceback.Symbolic;

         procedure STB is

            use Ada;
            use GNAT.Traceback;
            use GNAT.Traceback.Symbolic;

            procedure P1 is
               TB  : Tracebacks_Array (1 .. 10);
               --  We are asking for a maximum of 10 stack frames.
               Len : Natural;
               --  Len will receive the actual number of stack frames returned.
            begin
               Call_Chain (TB, Len);
               Text_IO.Put_Line (Symbolic_Traceback (TB (1 .. Len)));
            end P1;

            procedure P2 is
            begin
               P1;
            end P2;

         begin
            P2;
         end STB;

Automatic Symbolic Tracebacks
.............................

Symbolic tracebacks may also be enabled by using the -Es switch to
gnatbind (as in `gprbuild -g ... -bargs -Es').  This will cause the
Exception_Information to contain a symbolic traceback, which will also
be printed if an unhandled exception terminates the program.


File: gnat_ugn.info,  Node: Code Coverage and Profiling,  Next: Improving Performance,  Prev: Running and Debugging Ada Programs,  Up: GNAT and Program Execution

8.2 Code Coverage and Profiling
===============================

This section describes how to use the `gcov' coverage testing tool and
the `gprof' profiler tool on Ada programs.

* Menu:

* Code Coverage of Ada Programs with gcov::
* Profiling an Ada Program with gprof::


File: gnat_ugn.info,  Node: Code Coverage of Ada Programs with gcov,  Next: Profiling an Ada Program with gprof,  Up: Code Coverage and Profiling

8.2.1 Code Coverage of Ada Programs with gcov
---------------------------------------------

`gcov' is a test coverage program: it analyzes the execution of a given
program on selected tests, to help you determine the portions of the
program that are still untested.

`gcov' is part of the GCC suite, and is described in detail in the GCC
User's Guide. You can refer to this documentation for a more complete
description.

This chapter provides a quick startup guide, and details some
GNAT-specific features.

* Menu:

* Quick startup guide::
* GNAT specifics::


File: gnat_ugn.info,  Node: Quick startup guide,  Next: GNAT specifics,  Up: Code Coverage of Ada Programs with gcov

8.2.1.1 Quick startup guide
...........................

In order to perform coverage analysis of a program using `gcov', several
steps are needed:

  1. Instrument the code during the compilation process,

  2. Execute the instrumented program, and

  3. Invoke the `gcov' tool to generate the coverage results.

The code instrumentation needed by gcov is created at the object level.
The source code is not modified in any way, because the instrumentation
code is inserted by gcc during the compilation process. To compile your
code with code coverage activated, you need to recompile your whole
project using the switches `-fprofile-arcs' and `-ftest-coverage', and
link it using `-fprofile-arcs'.

         $ gnatmake -P my_project.gpr -f -cargs -fprofile-arcs -ftest-coverage \\
            -largs -fprofile-arcs

This compilation process will create `.gcno' files together with the
usual object files.

Once the program is compiled with coverage instrumentation, you can run
it as many times as needed - on portions of a test suite for example.
The first execution will produce `.gcda' files at the same location as
the `.gcno' files.  Subsequent executions will update those files, so
that a cumulative result of the covered portions of the program is
generated.

Finally, you need to call the `gcov' tool. The different options of
`gcov' are described in the GCC User's Guide, section 'Invoking gcov'.

This will create annotated source files with a `.gcov' extension:
`my_main.adb' file will be analyzed in `my_main.adb.gcov'.


File: gnat_ugn.info,  Node: GNAT specifics,  Prev: Quick startup guide,  Up: Code Coverage of Ada Programs with gcov

8.2.1.2 GNAT specifics
......................

Because of Ada semantics, portions of the source code may be shared
among several object files. This is the case for example when generics
are involved, when inlining is active  or when declarations generate
initialisation calls. In order to take into account this shared code,
you need to call `gcov' on all source files of the tested program at
once.

The list of source files might exceed the system's maximum command line
length. In order to bypass this limitation, a new mechanism has been
implemented in `gcov': you can now list all your project's files into a
text file, and provide this file to gcov as a parameter,  preceded by a
`@' (e.g. `gcov @mysrclist.txt').

Note that on AIX compiling a static library with `-fprofile-arcs' is
not supported as there can be unresolved symbols during the final link.


File: gnat_ugn.info,  Node: Profiling an Ada Program with gprof,  Prev: Code Coverage of Ada Programs with gcov,  Up: Code Coverage and Profiling

8.2.2 Profiling an Ada Program with gprof
-----------------------------------------

This section is not meant to be an exhaustive documentation of `gprof'.
Full documentation for it can be found in the `GNU Profiler User's
Guide' documentation that is part of this GNAT distribution.

Profiling a program helps determine the parts of a program that are
executed most often, and are therefore the most time-consuming.

`gprof' is the standard GNU profiling tool; it has been enhanced to
better handle Ada programs and multitasking.  It is currently supported
on the following platforms

   * linux x86/x86_64

   * solaris sparc/sparc64/x86

   * windows x86

In order to profile a program using `gprof', several steps are needed:

  1. Instrument the code, which requires a full recompilation of the
     project with the proper switches.

  2. Execute the program under the analysis conditions, i.e. with the
     desired input.

  3. Analyze the results using the `gprof' tool.

The following sections detail the different steps, and indicate how to
interpret the results.

* Menu:

* Compilation for profiling::
* Program execution::
* Running gprof::
* Interpretation of profiling results::


File: gnat_ugn.info,  Node: Compilation for profiling,  Next: Program execution,  Up: Profiling an Ada Program with gprof

8.2.2.1 Compilation for profiling
.................................

In order to profile a program the first step is to tell the compiler to
generate the necessary profiling information. The compiler switch to be
used is `-pg', which must be added to other compilation switches. This
switch needs to be specified both during compilation and link stages,
and can be specified once when using gnatmake:

         $ gnatmake -f -pg -P my_project

Note that only the objects that were compiled with the `-pg' switch will
be profiled; if you need to profile your whole project, use the `-f'
gnatmake switch to force full recompilation.


File: gnat_ugn.info,  Node: Program execution,  Next: Running gprof,  Prev: Compilation for profiling,  Up: Profiling an Ada Program with gprof

8.2.2.2 Program execution
.........................

Once the program has been compiled for profiling, you can run it as
usual.

The only constraint imposed by profiling is that the program must
terminate normally. An interrupted program (via a Ctrl-C, kill, etc.)
will not be properly analyzed.

Once the program completes execution, a data file called `gmon.out' is
generated in the directory where the program was launched from. If this
file already exists, it will be overwritten.


File: gnat_ugn.info,  Node: Running gprof,  Next: Interpretation of profiling results,  Prev: Program execution,  Up: Profiling an Ada Program with gprof

8.2.2.3 Running gprof
.....................

The `gprof' tool is called as follow:

         $ gprof my_prog gmon.out

or simply:

         $  gprof my_prog

The complete form of the gprof command line is the following:

         $ gprof [switches] [executable [data-file]]

`gprof' supports numerous switches. The order of these switch does not
matter. The full list of options can be found in the GNU Profiler
User's Guide documentation that comes with this documentation.

The following is the subset of those switches that is most relevant:

`--demangle[=`style']', `--no-demangle'
     These options control whether symbol names should be demangled when
     printing output.  The default is to demangle C++ symbols.  The
     `--no-demangle' option may be used to turn off demangling.
     Different compilers have different mangling styles.  The optional
     demangling style argument can be used to choose an appropriate
     demangling style for your compiler, in particular Ada symbols
     generated by GNAT can be demangled using `--demangle=gnat'.

`-e `function_name''
     The `-e `function'' option tells `gprof' not to print information
     about the function `function_name' (and its children...) in the
     call graph.  The function will still be listed as a child of any
     functions that call it, but its index number will be shown as
     `[not printed]'.  More than one `-e' option may be given; only one
     `function_name' may be indicated with each `-e' option.

`-E `function_name''
     The `-E `function'' option works like the `-e' option, but
     execution time spent in the function (and children who were not
     called from anywhere else), will not be used to compute the
     percentages-of-time for the call graph.  More than one `-E' option
     may be given; only one `function_name' may be indicated with each
     `-E' option.

`-f `function_name''
     The `-f `function'' option causes `gprof' to limit the call graph
     to the function `function_name' and its children (and their
     children...).  More than one `-f' option may be given; only one
     `function_name' may be indicated with each `-f' option.

`-F `function_name''
     The `-F `function'' option works like the `-f' option, but only
     time spent in the function and its children (and their
     children...) will be used to determine total-time and
     percentages-of-time for the call graph.  More than one `-F' option
     may be given; only one `function_name' may be indicated with each
     `-F' option.  The `-F' option overrides the `-E' option.


File: gnat_ugn.info,  Node: Interpretation of profiling results,  Prev: Running gprof,  Up: Profiling an Ada Program with gprof

8.2.2.4 Interpretation of profiling results
...........................................

The results of the profiling analysis are represented by two arrays: the
'flat profile' and the 'call graph'. Full documentation of those outputs
can be found in the GNU Profiler User's Guide.

The flat profile shows the time spent in each function of the program,
and how many time it has been called. This allows you to locate easily
the most time-consuming functions.

The call graph shows, for each subprogram, the subprograms that call it,
and the subprograms that it calls. It also provides an estimate of the
time spent in each of those callers/called subprograms.


File: gnat_ugn.info,  Node: Improving Performance,  Next: Overflow Check Handling in GNAT,  Prev: Code Coverage and Profiling,  Up: GNAT and Program Execution

8.3 Improving Performance
=========================

This section presents several topics related to program performance.
It first describes some of the tradeoffs that need to be considered and
some of the techniques for making your program run faster.

It then documents the unused subprogram/data elimination feature, which
can reduce the size of program executables.

* Menu:

* Performance Considerations::
* Text_IO Suggestions::
* Reducing Size of Executables with Unused Subprogram/Data Elimination::


File: gnat_ugn.info,  Node: Performance Considerations,  Next: Text_IO Suggestions,  Up: Improving Performance

8.3.1 Performance Considerations
--------------------------------

The GNAT system provides a number of options that allow a trade-off
between

   * performance of the generated code

   * speed of compilation

   * minimization of dependences and recompilation

   * the degree of run-time checking.

The defaults (if no options are selected) aim at improving the speed of
compilation and minimizing dependences, at the expense of performance
of the generated code:

   * no optimization

   * no inlining of subprogram calls

   * all run-time checks enabled except overflow and elaboration checks

These options are suitable for most program development purposes. This
section describes how you can modify these choices, and also provides
some guidelines on debugging optimized code.

* Menu:

* Controlling Run-Time Checks::
* Use of Restrictions::
* Optimization Levels::
* Debugging Optimized Code::
* Inlining of Subprograms::
* Floating_Point_Operations::
* Vectorization of loops::
* Other Optimization Switches::
* Optimization and Strict Aliasing::
* Aliased Variables and Optimization::
* Atomic Variables and Optimization::
* Passive Task Optimization::


File: gnat_ugn.info,  Node: Controlling Run-Time Checks,  Next: Use of Restrictions,  Up: Performance Considerations

8.3.1.1 Controlling Run-Time Checks
...................................

By default, GNAT generates all run-time checks, except stack overflow
checks, and checks for access before elaboration on subprogram calls.
The latter are not required in default mode, because all necessary
checking is done at compile time.

The gnat switch, `-gnatp' allows this default to be modified. See *note
Run-Time Checks: 101.

Our experience is that the default is suitable for most development
purposes.

Elaboration checks are off by default, and also not needed by default,
since GNAT uses a static elaboration analysis approach that avoids the
need for run-time checking. This manual contains a full chapter
discussing the issue of elaboration checks, and if the default is not
satisfactory for your use, you should read this chapter.

For validity checks, the minimal checks required by the Ada Reference
Manual (for case statements and assignments to array elements) are on
by default. These can be suppressed by use of the `-gnatVn' switch.
Note that in Ada 83, there were no validity checks, so if the Ada 83
mode is acceptable (or when comparing GNAT performance with an Ada 83
compiler), it may be reasonable to routinely use `-gnatVn'. Validity
checks are also suppressed entirely if `-gnatp' is used.

Note that the setting of the switches controls the default setting of
the checks. They may be modified using either `pragma Suppress' (to
remove checks) or `pragma Unsuppress' (to add back suppressed checks)
in the program source.


File: gnat_ugn.info,  Node: Use of Restrictions,  Next: Optimization Levels,  Prev: Controlling Run-Time Checks,  Up: Performance Considerations

8.3.1.2 Use of Restrictions
...........................

The use of pragma Restrictions allows you to control which features are
permitted in your program. Apart from the obvious point that if you
avoid relatively expensive features like finalization (enforceable by
the use of pragma Restrictions (No_Finalization), the use of this
pragma does not affect the generated code in most cases.

One notable exception to this rule is that the possibility of task abort
results in some distributed overhead, particularly if finalization or
exception handlers are used. The reason is that certain sections of code
have to be marked as non-abortable.

If you use neither the `abort' statement, nor asynchronous transfer of
control (`select ... then abort'), then this distributed overhead is
removed, which may have a general positive effect in improving overall
performance.  Especially code involving frequent use of tasking
constructs and controlled types will show much improved performance.
The relevant restrictions pragmas are

         pragma Restrictions (No_Abort_Statements);
         pragma Restrictions (Max_Asynchronous_Select_Nesting => 0);

It is recommended that these restriction pragmas be used if possible.
Note that this also means that you can write code without worrying
about the possibility of an immediate abort at any point.


File: gnat_ugn.info,  Node: Optimization Levels,  Next: Debugging Optimized Code,  Prev: Use of Restrictions,  Up: Performance Considerations

8.3.1.3 Optimization Levels
...........................

Without any optimization option, the compiler's goal is to reduce the
cost of compilation and to make debugging produce the expected results.
Statements are independent: if you stop the program with a breakpoint
between statements, you can then assign a new value to any variable or
change the program counter to any other statement in the subprogram and
get exactly the results you would expect from the source code.

Turning on optimization makes the compiler attempt to improve the
performance and/or code size at the expense of compilation time and
possibly the ability to debug the program.

If you use multiple -O options, with or without level numbers, the last
such option is the one that is effective.

The default is optimization off. This results in the fastest compile
times, but GNAT makes absolutely no attempt to optimize, and the
generated programs are considerably larger and slower than when
optimization is enabled. You can use the `-O' switch (the permitted
forms are `-O0', `-O1' `-O2', `-O3', and `-Os') to `gcc' to control the
optimization level:

   *
    `-O0'
          No optimization (the default); generates unoptimized code but
          has the fastest compilation time.

          Note that many other compilers do fairly extensive
          optimization even if 'no optimization' is specified. With
          gcc, it is very unusual to use -O0 for production if
          execution time is of any concern, since -O0 really does mean
          no optimization at all. This difference between gcc and other
          compilers should be kept in mind when doing performance
          comparisons.

   *
    `-O1'
          Moderate optimization; optimizes reasonably well but does not
          degrade compilation time significantly.

   *
    `-O2'
          Full optimization; generates highly optimized code and has
          the slowest compilation time.

   *
    `-O3'
          Full optimization as in `-O2'; also uses more aggressive
          automatic inlining of subprograms within a unit (*note
          Inlining of Subprograms: 117.) and attempts to vectorize
          loops.

   *
    `-Os'
          Optimize space usage (code and data) of resulting program.

Higher optimization levels perform more global transformations on the
program and apply more expensive analysis algorithms in order to
generate faster and more compact code. The price in compilation time,
and the resulting improvement in execution time, both depend on the
particular application and the hardware environment.  You should
experiment to find the best level for your application.

Since the precise set of optimizations done at each level will vary from
release to release (and sometime from target to target), it is best to
think of the optimization settings in general terms.  See the `Options
That Control Optimization' section in `Using the GNU Compiler
Collection (GCC)' for details about the `-O' settings and a number of
`-f' options that individually enable or disable specific optimizations.

Unlike some other compilation systems, `gcc' has been tested
extensively at all optimization levels. There are some bugs which
appear only with optimization turned on, but there have also been bugs
which show up only in `unoptimized' code. Selecting a lower level of
optimization does not improve the reliability of the code generator,
which in practice is highly reliable at all optimization levels.

Note regarding the use of `-O3': The use of this optimization level is
generally discouraged with GNAT, since it often results in larger
executables which may run more slowly. See further discussion of this
point in *note Inlining of Subprograms: 117.


File: gnat_ugn.info,  Node: Debugging Optimized Code,  Next: Inlining of Subprograms,  Prev: Optimization Levels,  Up: Performance Considerations

8.3.1.4 Debugging Optimized Code
................................

Although it is possible to do a reasonable amount of debugging at
nonzero optimization levels, the higher the level the more likely that
source-level constructs will have been eliminated by optimization.  For
example, if a loop is strength-reduced, the loop control variable may
be completely eliminated and thus cannot be displayed in the debugger.
This can only happen at `-O2' or `-O3'.  Explicit temporary variables
that you code might be eliminated at level `-O1' or higher.

The use of the `-g' switch, which is needed for source-level debugging,
affects the size of the program executable on disk, and indeed the
debugging information can be quite large.  However, it has no effect on
the generated code (and thus does not degrade performance)

Since the compiler generates debugging tables for a compilation unit
before it performs optimizations, the optimizing transformations may
invalidate some of the debugging data.  You therefore need to
anticipate certain anomalous situations that may arise while debugging
optimized code.  These are the most common cases:

   * `The 'hopping Program Counter':'  Repeated `step' or `next'
     commands show the PC bouncing back and forth in the code.  This
     may result from any of the following optimizations:

        - `Common subexpression elimination:' using a single instance
          of code for a quantity that the source computes several
          times.  As a result you may not be able to stop on what looks
          like a statement.

        - `Invariant code motion:' moving an expression that does not
          change within a loop, to the beginning of the loop.

        - `Instruction scheduling:' moving instructions so as to
          overlap loads and stores (typically) with other code, or in
          general to move computations of values closer to their uses.
          Often this causes you to pass an assignment statement without
          the assignment happening and then later bounce back to the
          statement when the value is actually needed.  Placing a
          breakpoint on a line of code and then stepping over it may,
          therefore, not always cause all the expected side-effects.

   * `The 'big leap':' More commonly known as `cross-jumping', in which
     two identical pieces of code are merged and the program counter
     suddenly jumps to a statement that is not supposed to be executed,
     simply because it (and the code following) translates to the same
     thing as the code that `was' supposed to be executed.  This effect
     is typically seen in sequences that end in a jump, such as a
     `goto', a `return', or a `break' in a C `switch' statement.

   * `The 'roving variable':' The symptom is an unexpected value in a
     variable.  There are various reasons for this effect:

        - In a subprogram prologue, a parameter may not yet have been
          moved to its 'home'.

        - A variable may be dead, and its register re-used.  This is
          probably the most common cause.

        - As mentioned above, the assignment of a value to a variable
          may have been moved.

        - A variable may be eliminated entirely by value propagation or
          other means.  In this case, GCC may incorrectly generate
          debugging information for the variable

     In general, when an unexpected value appears for a local variable
     or parameter you should first ascertain if that value was actually
     computed by your program, as opposed to being incorrectly reported
     by the debugger.  Record fields or array elements in an object
     designated by an access value are generally less of a problem,
     once you have ascertained that the access value is sensible.
     Typically, this means checking variables in the preceding code and
     in the calling subprogram to verify that the value observed is
     explainable from other values (one must apply the procedure
     recursively to those other values); or re-running the code and
     stopping a little earlier (perhaps before the call) and stepping
     to better see how the variable obtained the value in question; or
     continuing to step `from' the point of the strange value to see if
     code motion had simply moved the variable's assignments later.

In light of such anomalies, a recommended technique is to use `-O0'
early in the software development cycle, when extensive debugging
capabilities are most needed, and then move to `-O1' and later `-O2' as
the debugger becomes less critical.  Whether to use the `-g' switch in
the release version is a release management issue.  Note that if you
use `-g' you can then use the `strip' program on the resulting
executable, which removes both debugging information and global symbols.


File: gnat_ugn.info,  Node: Inlining of Subprograms,  Next: Floating_Point_Operations,  Prev: Debugging Optimized Code,  Up: Performance Considerations

8.3.1.5 Inlining of Subprograms
...............................

A call to a subprogram in the current unit is inlined if all the
following conditions are met:

   * The optimization level is at least `-O1'.

   * The called subprogram is suitable for inlining: It must be small
     enough and not contain something that `gcc' cannot support in
     inlined subprograms.

   * Any one of the following applies: `pragma Inline' is applied to the
     subprogram and the `-gnatn' switch is specified; the subprogram is
     local to the unit and called once from within it; the subprogram
     is small and optimization level `-O2' is specified; optimization
     level `-O3' is specified.

Calls to subprograms in `with'ed units are normally not inlined.  To
achieve actual inlining (that is, replacement of the call by the code
in the body of the subprogram), the following conditions must all be
true:

   * The optimization level is at least `-O1'.

   * The called subprogram is suitable for inlining: It must be small
     enough and not contain something that `gcc' cannot support in
     inlined subprograms.

   * The call appears in a body (not in a package spec).

   * There is a `pragma Inline' for the subprogram.

   * The `-gnatn' switch is used on the command line.

Even if all these conditions are met, it may not be possible for the
compiler to inline the call, due to the length of the body, or features
in the body that make it impossible for the compiler to do the inlining.

Note that specifying the `-gnatn' switch causes additional compilation
dependencies. Consider the following:

         package R is
            procedure Q;
            pragma Inline (Q);
         end R;
         package body R is
            ...
         end R;

         with R;
         procedure Main is
         begin
            ...
            R.Q;
         end Main;

With the default behavior (no `-gnatn' switch specified), the
compilation of the `Main' procedure depends only on its own source,
`main.adb', and the spec of the package in file `r.ads'. This means
that editing the body of `R' does not require recompiling `Main'.

On the other hand, the call `R.Q' is not inlined under these
circumstances. If the `-gnatn' switch is present when `Main' is
compiled, the call will be inlined if the body of `Q' is small enough,
but now `Main' depends on the body of `R' in `r.adb' as well as on the
spec. This means that if this body is edited, the main program must be
recompiled. Note that this extra dependency occurs whether or not the
call is in fact inlined by `gcc'.

The use of front end inlining with `-gnatN' generates similar
additional dependencies.

Note: The `-fno-inline' switch overrides all other conditions and
ensures that no inlining occurs, unless requested with pragma
Inline_Always for gcc back-ends. The extra dependences resulting from
`-gnatn' will still be active, even if this switch is used to suppress
the resulting inlining actions.

Note: The `-fno-inline-functions' switch can be used to prevent
automatic inlining of subprograms if `-O3' is used.

Note: The `-fno-inline-small-functions' switch can be used to prevent
automatic inlining of small subprograms if `-O2' is used.

Note: The `-fno-inline-functions-called-once' switch can be used to
prevent inlining of subprograms local to the unit and called once from
within it if `-O1' is used.

Note regarding the use of `-O3': `-gnatn' is made up of two
sub-switches `-gnatn1' and `-gnatn2' that can be directly specified in
lieu of it, `-gnatn' being translated into one of them based on the
optimization level. With `-O2' or below, `-gnatn' is equivalent to
`-gnatn1' which activates pragma `Inline' with moderate inlining across
modules. With `-O3', `-gnatn' is equivalent to `-gnatn2' which
activates pragma `Inline' with full inlining across modules. If you
have used pragma `Inline' in appropriate cases, then it is usually much
better to use `-O2' and `-gnatn' and avoid the use of `-O3' which has
the additional effect of inlining subprograms you did not think should
be inlined. We have found that the use of `-O3' may slow down the
compilation and increase the code size by performing excessive
inlining, leading to increased instruction cache pressure from the
increased code size and thus minor performance improvements. So the
bottom line here is that you should not automatically assume that `-O3'
is better than `-O2', and indeed you should use `-O3' only if tests
show that it actually improves performance for your program.


File: gnat_ugn.info,  Node: Floating_Point_Operations,  Next: Vectorization of loops,  Prev: Inlining of Subprograms,  Up: Performance Considerations

8.3.1.6 Floating_Point_Operations
.................................

On almost all targets, GNAT maps Float and Long_Float to the 32-bit and
64-bit standard IEEE floating-point representations, and operations will
use standard IEEE arithmetic as provided by the processor. On most, but
not all, architectures, the attribute Machine_Overflows is False for
these types, meaning that the semantics of overflow is
implementation-defined.  In the case of GNAT, these semantics
correspond to the normal IEEE treatment of infinities and NaN (not a
number) values. For example, 1.0 / 0.0 yields plus infinitiy and 0.0 /
0.0 yields a NaN. By avoiding explicit overflow checks, the performance
is greatly improved on many targets. However, if required,
floating-point overflow can be enabled by the use of the pragma
Check_Float_Overflow.

Another consideration that applies specifically to x86 32-bit
architectures is which form of floating-point arithmetic is used.  By
default the operations use the old style x86 floating-point, which
implements an 80-bit extended precision form (on these architectures
the type Long_Long_Float corresponds to that form).  In addition,
generation of efficient code in this mode means that the extended
precision form will be used for intermediate results.  This may be
helpful in improving the final precision of a complex expression.
However it means that the results obtained on the x86 will be different
from those on other architectures, and for some algorithms, the extra
intermediate precision can be detrimental.

In addition to this old-style floating-point, all modern x86 chips
implement an alternative floating-point operation model referred to as
SSE2. In this model there is no extended form, and furthermore
execution performance is significantly enhanced. To force GNAT to use
this more modern form, use both of the switches:

     -msse2 -mfpmath=sse

A unit compiled with these switches will automatically use the more
efficient SSE2 instruction set for Float and Long_Float operations.
Note that the ABI has the same form for both floating-point models, so
it is permissible to mix units compiled with and without these switches.


File: gnat_ugn.info,  Node: Vectorization of loops,  Next: Other Optimization Switches,  Prev: Floating_Point_Operations,  Up: Performance Considerations

8.3.1.7 Vectorization of loops
..............................

You can take advantage of the auto-vectorizer present in the `gcc' back
end to vectorize loops with GNAT.  The corresponding command line switch
is `-ftree-vectorize' but, as it is enabled by default at `-O3' and
other aggressive optimizations helpful for vectorization also are
enabled by default at this level, using `-O3' directly is recommended.

You also need to make sure that the target architecture features a
supported SIMD instruction set.  For example, for the x86 architecture,
you should at least specify `-msse2' to get significant vectorization
(but you don't need to specify it for x86-64 as it is part of the base
64-bit architecture).  Similarly, for the PowerPC architecture, you
should specify `-maltivec'.

The preferred loop form for vectorization is the `for' iteration scheme.
Loops with a `while' iteration scheme can also be vectorized if they are
very simple, but the vectorizer will quickly give up otherwise.  With
either iteration scheme, the flow of control must be straight, in
particular no `exit' statement may appear in the loop body.  The loop
may however contain a single nested loop, if it can be vectorized when
considered alone:

         A : array (1..4, 1..4) of Long_Float;
         S : array (1..4) of Long_Float;

         procedure Sum is
         begin
            for I in A'Range(1) loop
               for J in A'Range(2) loop
                  S (I) := S (I) + A (I, J);
               end loop;
            end loop;
         end Sum;

The vectorizable operations depend on the targeted SIMD instruction
set, but the adding and some of the multiplying operators are generally
supported, as well as the logical operators for modular types. Note
that compiling with `-gnatp' might well reveal cases where some checks
do thwart vectorization.

Type conversions may also prevent vectorization if they involve
semantics that are not directly supported by the code generator or the
SIMD instruction set.  A typical example is direct conversion from
floating-point to integer types.  The solution in this case is to use
the following idiom:

         Integer (S'Truncation (F))

if `S' is the subtype of floating-point object `F'.

In most cases, the vectorizable loops are loops that iterate over
arrays.  All kinds of array types are supported, i.e. constrained array
types with static bounds:

         type Array_Type is array (1 .. 4) of Long_Float;

constrained array types with dynamic bounds:

         type Array_Type is array (1 .. Q.N) of Long_Float;

         type Array_Type is array (Q.K .. 4) of Long_Float;

         type Array_Type is array (Q.K .. Q.N) of Long_Float;

or unconstrained array types:

         type Array_Type is array (Positive range <>) of Long_Float;

The quality of the generated code decreases when the dynamic aspect of
the array type increases, the worst code being generated for
unconstrained array types.  This is so because, the less information
the compiler has about the bounds of the array, the more fallback code
it needs to generate in order to fix things up at run time.

It is possible to specify that a given loop should be subject to
vectorization preferably to other optimizations by means of pragma
`Loop_Optimize':

         pragma Loop_Optimize (Vector);

placed immediately within the loop will convey the appropriate hint to
the compiler for this loop.

It is also possible to help the compiler generate better vectorized code
for a given loop by asserting that there are no loop-carried
dependencies in the loop.  Consider for example the procedure:

         type Arr is array (1 .. 4) of Long_Float;

         procedure Add (X, Y : not null access Arr; R : not null access Arr) is
         begin
           for I in Arr'Range loop
             R(I) := X(I) + Y(I);
           end loop;
         end;

By default, the compiler cannot unconditionally vectorize the loop
because assigning to a component of the array designated by R in one
iteration could change the value read from the components of the array
designated by X or Y in a later iteration.  As a result, the compiler
will generate two versions of the loop in the object code, one
vectorized and the other not vectorized, as well as a test to select
the appropriate version at run time.  This can be overcome by another
hint:

         pragma Loop_Optimize (Ivdep);

placed immediately within the loop will tell the compiler that it can
safely omit the non-vectorized version of the loop as well as the
run-time test.


File: gnat_ugn.info,  Node: Other Optimization Switches,  Next: Optimization and Strict Aliasing,  Prev: Vectorization of loops,  Up: Performance Considerations

8.3.1.8 Other Optimization Switches
...................................

Since `GNAT' uses the `gcc' back end, all the specialized `gcc'
optimization switches are potentially usable. These switches have not
been extensively tested with GNAT but can generally be expected to
work. Examples of switches in this category are `-funroll-loops' and
the various target-specific `-m' options (in particular, it has been
observed that `-march=xxx' can significantly improve performance on
appropriate machines). For full details of these switches, see the
`Submodel Options' section in the `Hardware Models and Configurations'
chapter of `Using the GNU Compiler Collection (GCC)'.


File: gnat_ugn.info,  Node: Optimization and Strict Aliasing,  Next: Aliased Variables and Optimization,  Prev: Other Optimization Switches,  Up: Performance Considerations

8.3.1.9 Optimization and Strict Aliasing
........................................

The strong typing capabilities of Ada allow an optimizer to generate
efficient code in situations where other languages would be forced to
make worst case assumptions preventing such optimizations. Consider the
following example:

         procedure R is
            type Int1 is new Integer;
            type Int2 is new Integer;
            type Int1A is access Int1;
            type Int2A is access Int2;
            Int1V : Int1A;
            Int2V : Int2A;
            ...

         begin
            ...
            for J in Data'Range loop
               if Data (J) = Int1V.all then
                  Int2V.all := Int2V.all + 1;
               end if;
            end loop;
            ...
         end R;

In this example, since the variable `Int1V' can only access objects of
type `Int1', and `Int2V' can only access objects of type `Int2', there
is no possibility that the assignment to `Int2V.all' affects the value
of `Int1V.all'. This means that the compiler optimizer can "know" that
the value `Int1V.all' is constant for all iterations of the loop and
avoid the extra memory reference required to dereference it each time
through the loop.

This kind of optimization, called strict aliasing analysis, is
triggered by specifying an optimization level of `-O2' or higher or
`-Os' and allows `GNAT' to generate more efficient code when access
values are involved.

However, although this optimization is always correct in terms of the
formal semantics of the Ada Reference Manual, difficulties can arise if
features like `Unchecked_Conversion' are used to break the typing
system. Consider the following complete program example:

         package p1 is
            type int1 is new integer;
            type int2 is new integer;
            type a1 is access int1;
            type a2 is access int2;
         end p1;

         with p1; use p1;
         package p2 is
            function to_a2 (Input : a1) return a2;
         end p2;

         with Unchecked_Conversion;
         package body p2 is
            function to_a2 (Input : a1) return a2 is
               function to_a2u is
                 new Unchecked_Conversion (a1, a2);
            begin
               return to_a2u (Input);
            end to_a2;
         end p2;

         with p2; use p2;
         with p1; use p1;
         with Text_IO; use Text_IO;
         procedure m is
            v1 : a1 := new int1;
            v2 : a2 := to_a2 (v1);
         begin
            v1.all := 1;
            v2.all := 0;
            put_line (int1'image (v1.all));
         end;

This program prints out 0 in `-O0' or `-O1' mode, but it prints out 1
in `-O2' mode. That's because in strict aliasing mode, the compiler can
and does assume that the assignment to `v2.all' could not affect the
value of `v1.all', since different types are involved.

This behavior is not a case of non-conformance with the standard, since
the Ada RM specifies that an unchecked conversion where the resulting
bit pattern is not a correct value of the target type can result in an
abnormal value and attempting to reference an abnormal value makes the
execution of a program erroneous.  That's the case here since the result
does not point to an object of type `int2'.  This means that the effect
is entirely unpredictable.

However, although that explanation may satisfy a language lawyer, in
practice an applications programmer expects an unchecked conversion
involving pointers to create true aliases and the behavior of printing
1 seems plain wrong.  In this case, the strict aliasing optimization is
unwelcome.

Indeed the compiler recognizes this possibility, and the unchecked
conversion generates a warning:

         p2.adb:5:07: warning: possible aliasing problem with type "a2"
         p2.adb:5:07: warning: use -fno-strict-aliasing switch for references
         p2.adb:5:07: warning:  or use "pragma No_Strict_Aliasing (a2);"

Unfortunately the problem is recognized when compiling the body of
package `p2', but the actual "bad" code is generated while compiling
the body of `m' and this latter compilation does not see the suspicious
`Unchecked_Conversion'.

As implied by the warning message, there are approaches you can use to
avoid the unwanted strict aliasing optimization in a case like this.

One possibility is to simply avoid the use of `-O2', but that is a bit
drastic, since it throws away a number of useful optimizations that do
not involve strict aliasing assumptions.

A less drastic approach is to compile the program using the option
`-fno-strict-aliasing'. Actually it is only the unit containing the
dereferencing of the suspicious pointer that needs to be compiled. So
in this case, if we compile unit `m' with this switch, then we get the
expected value of zero printed. Analyzing which units might need the
switch can be painful, so a more reasonable approach is to compile the
entire program with options `-O2' and `-fno-strict-aliasing'. If the
performance is satisfactory with this combination of options, then the
advantage is that the entire issue of possible "wrong" optimization due
to strict aliasing is avoided.

To avoid the use of compiler switches, the configuration pragma
`No_Strict_Aliasing' with no parameters may be used to specify that for
all access types, the strict aliasing optimization should be suppressed.

However, these approaches are still overkill, in that they causes all
manipulations of all access values to be deoptimized. A more refined
approach is to concentrate attention on the specific access type
identified as problematic.

First, if a careful analysis of uses of the pointer shows that there
are no possible problematic references, then the warning can be
suppressed by bracketing the instantiation of `Unchecked_Conversion' to
turn the warning off:

         pragma Warnings (Off);
         function to_a2u is
           new Unchecked_Conversion (a1, a2);
         pragma Warnings (On);

Of course that approach is not appropriate for this particular example,
since indeed there is a problematic reference. In this case we can take
one of two other approaches.

The first possibility is to move the instantiation of unchecked
conversion to the unit in which the type is declared. In this example,
we would move the instantiation of `Unchecked_Conversion' from the body
of package `p2' to the spec of package `p1'. Now the warning
disappears. That's because any use of the access type knows there is a
suspicious unchecked conversion, and the strict aliasing optimization
is automatically suppressed for the type.

If it is not practical to move the unchecked conversion to the same unit
in which the destination access type is declared (perhaps because the
source type is not visible in that unit), you may use pragma
`No_Strict_Aliasing' for the type. This pragma must occur in the same
declarative sequence as the declaration of the access type:

         type a2 is access int2;
         pragma No_Strict_Aliasing (a2);

Here again, the compiler now knows that the strict aliasing optimization
should be suppressed for any reference to type `a2' and the expected
behavior is obtained.

Finally, note that although the compiler can generate warnings for
simple cases of unchecked conversions, there are tricker and more
indirect ways of creating type incorrect aliases which the compiler
cannot detect. Examples are the use of address overlays and unchecked
conversions involving composite types containing access types as
components. In such cases, no warnings are generated, but there can
still be aliasing problems. One safe coding practice is to forbid the
use of address clauses for type overlaying, and to allow unchecked
conversion only for primitive types. This is not really a significant
restriction since any possible desired effect can be achieved by
unchecked conversion of access values.

The aliasing analysis done in strict aliasing mode can certainly have
significant benefits. We have seen cases of large scale application
code where the time is increased by up to 5% by turning this
optimization off. If you have code that includes significant usage of
unchecked conversion, you might want to just stick with `-O1' and avoid
the entire issue. If you get adequate performance at this level of
optimization level, that's probably the safest approach. If tests show
that you really need higher levels of optimization, then you can
experiment with `-O2' and `-O2 -fno-strict-aliasing' to see how much
effect this has on size and speed of the code. If you really need to use
`-O2' with strict aliasing in effect, then you should review any uses
of unchecked conversion of access types, particularly if you are
getting the warnings described above.


File: gnat_ugn.info,  Node: Aliased Variables and Optimization,  Next: Atomic Variables and Optimization,  Prev: Optimization and Strict Aliasing,  Up: Performance Considerations

8.3.1.10 Aliased Variables and Optimization
...........................................

There are scenarios in which programs may use low level techniques to
modify variables that otherwise might be considered to be unassigned.
For example, a variable can be passed to a procedure by reference,
which takes the address of the parameter and uses the address to modify
the variable's value, even though it is passed as an IN parameter.
Consider the following example:

         procedure P is
            Max_Length : constant Natural := 16;
            type Char_Ptr is access all Character;

            procedure Get_String(Buffer: Char_Ptr; Size : Integer);
            pragma Import (C, Get_String, "get_string");

            Name : aliased String (1 .. Max_Length) := (others => ' ');
            Temp : Char_Ptr;

            function Addr (S : String) return Char_Ptr is
               function To_Char_Ptr is
                 new Ada.Unchecked_Conversion (System.Address, Char_Ptr);
            begin
               return To_Char_Ptr (S (S'First)'Address);
            end;

         begin
            Temp := Addr (Name);
            Get_String (Temp, Max_Length);
         end;

where Get_String is a C function that uses the address in Temp to
modify the variable `Name'. This code is dubious, and arguably
erroneous, and the compiler would be entitled to assume that `Name' is
never modified, and generate code accordingly.

However, in practice, this would cause some existing code that seems to
work with no optimization to start failing at high levels of
optimzization.

What the compiler does for such cases is to assume that marking a
variable as aliased indicates that some "funny business" may be going
on. The optimizer recognizes the aliased keyword and inhibits
optimizations that assume the value cannot be assigned.  This means
that the above example will in fact "work" reliably, that is, it will
produce the expected results.


File: gnat_ugn.info,  Node: Atomic Variables and Optimization,  Next: Passive Task Optimization,  Prev: Aliased Variables and Optimization,  Up: Performance Considerations

8.3.1.11 Atomic Variables and Optimization
..........................................

There are two considerations with regard to performance when atomic
variables are used.

First, the RM only guarantees that access to atomic variables be
atomic, it has nothing to say about how this is achieved, though there
is a strong implication that this should not be achieved by explicit
locking code. Indeed GNAT will never generate any locking code for
atomic variable access (it will simply reject any attempt to make a
variable or type atomic if the atomic access cannot be achieved without
such locking code).

That being said, it is important to understand that you cannot assume
that the entire variable will always be accessed. Consider this example:

         type R is record
            A,B,C,D : Character;
         end record;
         for R'Size use 32;
         for R'Alignment use 4;

         RV : R;
         pragma Atomic (RV);
         X : Character;
         ...
         X := RV.B;

You cannot assume that the reference to `RV.B' will read the entire
32-bit variable with a single load instruction. It is perfectly
legitimate if the hardware allows it to do a byte read of just the B
field. This read is still atomic, which is all the RM requires. GNAT
can and does take advantage of this, depending on the architecture and
optimization level.  Any assumption to the contrary is non-portable and
risky. Even if you examine the assembly language and see a full 32-bit
load, this might change in a future version of the compiler.

If your application requires that all accesses to `RV' in this example
be full 32-bit loads, you need to make a copy for the access as in:

         declare
            RV_Copy : constant R := RV;
         begin
            X := RV_Copy.B;
         end;

Now the reference to RV must read the whole variable.  Actually one can
imagine some compiler which figures out that the whole copy is not
required (because only the B field is actually accessed), but GNAT
certainly won't do that, and we don't know of any compiler that would
not handle this right, and the above code will in practice work
portably across all architectures (that permit the Atomic declaration).

The second issue with atomic variables has to do with the possible
requirement of generating synchronization code. For more details on
this, consult the sections on the pragmas
Enable/Disable_Atomic_Synchronization in the GNAT Reference Manual. If
performance is critical, and such synchronization code is not required,
it may be useful to disable it.


File: gnat_ugn.info,  Node: Passive Task Optimization,  Prev: Atomic Variables and Optimization,  Up: Performance Considerations

8.3.1.12 Passive Task Optimization
..................................

A passive task is one which is sufficiently simple that in theory a
compiler could recognize it an implement it efficiently without
creating a new thread. The original design of Ada 83 had in mind this
kind of passive task optimization, but only a few Ada 83 compilers
attempted it. The problem was that it was difficult to determine the
exact conditions under which the optimization was possible. The result
is a very fragile optimization where a very minor change in the program
can suddenly silently make a task non-optimizable.

With the revisiting of this issue in Ada 95, there was general
agreement that this approach was fundamentally flawed, and the notion
of protected types was introduced. When using protected types, the
restrictions are well defined, and you KNOW that the operations will be
optimized, and furthermore this optimized performance is fully portable.

Although it would theoretically be possible for GNAT to attempt to do
this optimization, but it really doesn't make sense in the context of
Ada 95, and none of the Ada 95 compilers implement this optimization as
far as we know. In particular GNAT never attempts to perform this
optimization.

In any new Ada 95 code that is written, you should always use protected
types in place of tasks that might be able to be optimized in this
manner.  Of course this does not help if you have legacy Ada 83 code
that depends on this optimization, but it is unusual to encounter a
case where the performance gains from this optimization are significant.

Your program should work correctly without this optimization. If you
have performance problems, then the most practical approach is to
figure out exactly where these performance problems arise, and update
those particular tasks to be protected types. Note that typically
clients of the tasks who call entries, will not have to be modified,
only the task definition itself.


File: gnat_ugn.info,  Node: Text_IO Suggestions,  Next: Reducing Size of Executables with Unused Subprogram/Data Elimination,  Prev: Performance Considerations,  Up: Improving Performance

8.3.2 `Text_IO' Suggestions
---------------------------

The `Ada.Text_IO' package has fairly high overheads due in part to the
requirement of maintaining page and line counts. If performance is
critical, a recommendation is to use `Stream_IO' instead of `Text_IO'
for volume output, since this package has less overhead.

If `Text_IO' must be used, note that by default output to the standard
output and standard error files is unbuffered (this provides better
behavior when output statements are used for debugging, or if the
progress of a program is observed by tracking the output, e.g. by using
the Unix `tail -f' command to watch redirected output.

If you are generating large volumes of output with `Text_IO' and
performance is an important factor, use a designated file instead of
the standard output file, or change the standard output file to be
buffered using `Interfaces.C_Streams.setvbuf'.


File: gnat_ugn.info,  Node: Reducing Size of Executables with Unused Subprogram/Data Elimination,  Prev: Text_IO Suggestions,  Up: Improving Performance

8.3.3 Reducing Size of Executables with Unused Subprogram/Data Elimination
--------------------------------------------------------------------------

This section describes how you can eliminate unused subprograms and
data from your executable just by setting options at compilation time.

* Menu:

* About unused subprogram/data elimination::
* Compilation options::
* Example of unused subprogram/data elimination::


File: gnat_ugn.info,  Node: About unused subprogram/data elimination,  Next: Compilation options,  Up: Reducing Size of Executables with Unused Subprogram/Data Elimination

8.3.3.1 About unused subprogram/data elimination
................................................

By default, an executable contains all code and data of its composing
objects (directly linked or coming from statically linked libraries),
even data or code never used by this executable.

This feature will allow you to eliminate such unused code from your
executable, making it smaller (in disk and in memory).

This functionality is available on all Linux platforms except for the
IA-64 architecture and on all cross platforms using the ELF binary file
format.  In both cases GNU binutils version 2.16 or later are required
to enable it.


File: gnat_ugn.info,  Node: Compilation options,  Next: Example of unused subprogram/data elimination,  Prev: About unused subprogram/data elimination,  Up: Reducing Size of Executables with Unused Subprogram/Data Elimination

8.3.3.2 Compilation options
...........................

The operation of eliminating the unused code and data from the final
executable is directly performed by the linker.

In order to do this, it has to work with objects compiled with the
following options: `-ffunction-sections' `-fdata-sections'.

These options are usable with C and Ada files.  They will place
respectively each function or data in a separate section in the
resulting object file.

Once the objects and static libraries are created with these options,
the linker can perform the dead code elimination. You can do this by
setting the `-Wl,-gc-sections' option to gcc command or in the `-largs'
section of `gnatmake'. This will perform a garbage collection of code
and data never referenced.

If the linker performs a partial link (`-r' linker option), then you
will need to provide the entry point using the `-e' / `-entry' linker
option.

Note that objects compiled without the `-ffunction-sections' and
`-fdata-sections' options can still be linked with the executable.
However, no dead code elimination will be performed on those objects
(they will be linked as is).

The GNAT static library is now compiled with -ffunction-sections and
-fdata-sections on some platforms. This allows you to eliminate the
unused code and data of the GNAT library from your executable.


File: gnat_ugn.info,  Node: Example of unused subprogram/data elimination,  Prev: Compilation options,  Up: Reducing Size of Executables with Unused Subprogram/Data Elimination

8.3.3.3 Example of unused subprogram/data elimination
.....................................................

Here is a simple example:

         with Aux;

         procedure Test is
         begin
            Aux.Used (10);
         end Test;

         package Aux is
            Used_Data   : Integer;
            Unused_Data : Integer;

            procedure Used   (Data : Integer);
            procedure Unused (Data : Integer);
         end Aux;

         package body Aux is
            procedure Used (Data : Integer) is
            begin
               Used_Data := Data;
            end Used;

            procedure Unused (Data : Integer) is
            begin
               Unused_Data := Data;
            end Unused;
         end Aux;

`Unused' and `Unused_Data' are never referenced in this code excerpt,
and hence they may be safely removed from the final executable.

         $ gnatmake test

         $ nm test | grep used
         020015f0 T aux__unused
         02005d88 B aux__unused_data
         020015cc T aux__used
         02005d84 B aux__used_data

         $ gnatmake test -cargs -fdata-sections -ffunction-sections \\
              -largs -Wl,--gc-sections

         $ nm test | grep used
         02005350 T aux__used
         0201ffe0 B aux__used_data

It can be observed that the procedure `Unused' and the object
`Unused_Data' are removed by the linker when using the appropriate
options.


File: gnat_ugn.info,  Node: Overflow Check Handling in GNAT,  Next: Performing Dimensionality Analysis in GNAT,  Prev: Improving Performance,  Up: GNAT and Program Execution

8.4 Overflow Check Handling in GNAT
===================================

This section explains how to control the handling of overflow checks.

* Menu:

* Background::
* Management of Overflows in GNAT::
* Specifying the Desired Mode::
* Default Settings::
* Implementation Notes::


File: gnat_ugn.info,  Node: Background,  Next: Management of Overflows in GNAT,  Up: Overflow Check Handling in GNAT

8.4.1 Background
----------------

Overflow checks are checks that the compiler may make to ensure that
intermediate results are not out of range. For example:

         A : Integer;
         ...
         A := A + 1;

If `A' has the value `Integer'Last', then the addition may cause
overflow since the result is out of range of the type `Integer'.  In
this case `Constraint_Error' will be raised if checks are enabled.

A trickier situation arises in examples like the following:

         A, C : Integer;
         ...
         A := (A + 1) + C;

where `A' is `Integer'Last' and `C' is `-1'.  Now the final result of
the expression on the right hand side is `Integer'Last' which is in
range, but the question arises whether the intermediate addition of `(A
+ 1)' raises an overflow error.

The (perhaps surprising) answer is that the Ada language definition
does not answer this question. Instead it leaves it up to the
implementation to do one of two things if overflow checks are enabled.

   * raise an exception (`Constraint_Error'), or

   * yield the correct mathematical result which is then used in
     subsequent operations.

If the compiler chooses the first approach, then the assignment of this
example will indeed raise `Constraint_Error' if overflow checking is
enabled, or result in erroneous execution if overflow checks are
suppressed.

But if the compiler chooses the second approach, then it can perform
both additions yielding the correct mathematical result, which is in
range, so no exception will be raised, and the right result is
obtained, regardless of whether overflow checks are suppressed.

Note that in the first example an exception will be raised in either
case, since if the compiler gives the correct mathematical result for
the addition, it will be out of range of the target type of the
assignment, and thus fails the range check.

This lack of specified behavior in the handling of overflow for
intermediate results is a source of non-portability, and can thus be
problematic when programs are ported. Most typically this arises in a
situation where the original compiler did not raise an exception, and
then the application is moved to a compiler where the check is
performed on the intermediate result and an unexpected exception is
raised.

Furthermore, when using Ada 2012's preconditions and other assertion
forms, another issue arises. Consider:

         procedure P (A, B : Integer) with
           Pre => A + B <= Integer'Last;

One often wants to regard arithmetic in a context like this from a
mathematical point of view. So for example, if the two actual parameters
for a call to `P' are both `Integer'Last', then the precondition should
be regarded as False. If we are executing in a mode with run-time
checks enabled for preconditions, then we would like this precondition
to fail, rather than raising an exception because of the intermediate
overflow.

However, the language definition leaves the specification of whether
the above condition fails (raising `Assert_Error') or causes an
intermediate overflow (raising `Constraint_Error') up to the
implementation.

The situation is worse in a case such as the following:

         procedure Q (A, B, C : Integer) with
           Pre => A + B + C <= Integer'Last;

Consider the call

         Q (A => Integer'Last, B => 1, C => -1);

From a mathematical point of view the precondition is True, but at run
time we may (but are not guaranteed to) get an exception raised because
of the intermediate overflow (and we really would prefer this
precondition to be considered True at run time).


File: gnat_ugn.info,  Node: Management of Overflows in GNAT,  Next: Specifying the Desired Mode,  Prev: Background,  Up: Overflow Check Handling in GNAT

8.4.2 Management of Overflows in GNAT
-------------------------------------

To deal with the portability issue, and with the problem of
mathematical versus run-time interpretation of the expressions in
assertions, GNAT provides comprehensive control over the handling of
intermediate overflow. GNAT can operate in three modes, and furthemore,
permits separate selection of operating modes for the expressions
within assertions (here the term 'assertions' is used in the technical
sense, which includes preconditions and so forth) and for expressions
appearing outside assertions.

The three modes are:

   * `Use base type for intermediate operations' (`STRICT')

     In this mode, all intermediate results for predefined arithmetic
     operators are computed using the base type, and the result must be
     in range of the base type. If this is not the case then either an
     exception is raised (if overflow checks are enabled) or the
     execution is erroneous (if overflow checks are suppressed).  This
     is the normal default mode.

   * `Most intermediate overflows avoided' (`MINIMIZED')

     In this mode, the compiler attempts to avoid intermediate
     overflows by using a larger integer type, typically
     `Long_Long_Integer', as the type in which arithmetic is performed
     for predefined arithmetic operators. This may be slightly more
     expensive at run time (compared to suppressing intermediate
     overflow checks), though the cost is negligible on modern 64-bit
     machines. For the examples given earlier, no intermediate
     overflows would have resulted in exceptions, since the
     intermediate results are all in the range of `Long_Long_Integer'
     (typically 64-bits on nearly all implementations of GNAT). In
     addition, if checks are enabled, this reduces the number of checks
     that must be made, so this choice may actually result in an
     improvement in space and time behavior.

     However, there are cases where `Long_Long_Integer' is not large
     enough, consider the following example:

              procedure R (A, B, C, D : Integer) with
                Pre => (A**2 * B**2) / (C**2 * D**2) <= 10;

     where `A' = `B' = `C' = `D' = `Integer'Last'.  Now the
     intermediate results are out of the range of `Long_Long_Integer'
     even though the final result is in range and the precondition is
     True (from a mathematical point of view). In such a case,
     operating in this mode, an overflow occurs for the intermediate
     computation (which is why this mode says `most' intermediate
     overflows are avoided). In this case, an exception is raised if
     overflow checks are enabled, and the execution is erroneous if
     overflow checks are suppressed.

   * `All intermediate overflows avoided' (`ELIMINATED')

     In this mode, the compiler  avoids all intermediate overflows by
     using arbitrary precision arithmetic as required. In this mode,
     the above example with `A**2 * B**2' would not cause intermediate
     overflow, because the intermediate result would be evaluated using
     sufficient precision, and the result of evaluating the
     precondition would be True.

     This mode has the advantage of avoiding any intermediate
     overflows, but at the expense of significant run-time overhead,
     including the use of a library (included automatically in this
     mode) for multiple-precision arithmetic.

     This mode provides cleaner semantics for assertions, since now the
     run-time behavior emulates true arithmetic behavior for the
     predefined arithmetic operators, meaning that there is never a
     conflict between the mathematical view of the assertion, and its
     run-time behavior.

     Note that in this mode, the behavior is unaffected by whether or
     not overflow checks are suppressed, since overflow does not occur.
     It is possible for gigantic intermediate expressions to raise
     `Storage_Error' as a result of attempting to compute the results
     of such expressions (e.g. `Integer'Last ** Integer'Last') but
     overflow is impossible.

Note that these modes apply only to the evaluation of predefined
arithmetic, membership, and comparison operators for signed integer
aritmetic.

For fixed-point arithmetic, checks can be suppressed. But if checks are
enabled then fixed-point values are always checked for overflow against
the base type for intermediate expressions (that is such checks always
operate in the equivalent of `STRICT' mode).

For floating-point, on nearly all architectures, `Machine_Overflows' is
False, and IEEE infinities are generated, so overflow exceptions are
never raised. If you want to avoid infinities, and check that final
results of expressions are in range, then you can declare a constrained
floating-point type, and range checks will be carried out in the normal
manner (with infinite values always failing all range checks).


File: gnat_ugn.info,  Node: Specifying the Desired Mode,  Next: Default Settings,  Prev: Management of Overflows in GNAT,  Up: Overflow Check Handling in GNAT

8.4.3 Specifying the Desired Mode
---------------------------------

The desired mode of for handling intermediate overflow can be specified
using either the `Overflow_Mode' pragma or an equivalent compiler
switch.  The pragma has the form

         pragma Overflow_Mode ([General =>] MODE [, [Assertions =>] MODE]);

where `MODE' is one of

   * `STRICT':  intermediate overflows checked (using base type)

   * `MINIMIZED': minimize intermediate overflows

   * `ELIMINATED': eliminate intermediate overflows

The case is ignored, so `MINIMIZED', `Minimized' and `minimized' all
have the same effect.

If only the `General' parameter is present, then the given `MODE'
applies to expressions both within and outside assertions. If both
arguments are present, then `General' applies to expressions outside
assertions, and `Assertions' applies to expressions within assertions.
For example:

         pragma Overflow_Mode
           (General => Minimized, Assertions => Eliminated);

specifies that general expressions outside assertions be evaluated in
'minimize intermediate overflows' mode, and expressions within
assertions be evaluated in 'eliminate intermediate overflows' mode.
This is often a reasonable choice, avoiding excessive overhead outside
assertions, but assuring a high degree of portability when importing
code from another compiler, while incurring the extra overhead for
assertion expressions to ensure that the behavior at run time matches
the expected mathematical behavior.

The `Overflow_Mode' pragma has the same scoping and placement rules as
pragma `Suppress', so it can occur either as a configuration pragma,
specifying a default for the whole program, or in a declarative scope,
where it applies to the remaining declarations and statements in that
scope.

Note that pragma `Overflow_Mode' does not affect whether overflow
checks are enabled or suppressed. It only controls the method used to
compute intermediate values. To control whether overflow checking is
enabled or suppressed, use pragma `Suppress' or `Unsuppress' in the
usual manner

Additionally, a compiler switch `-gnato?' or `-gnato??'  can be used to
control the checking mode default (which can be subsequently overridden
using pragmas).

Here `?' is one of the digits `1' through `3':

      `1'        use base type for intermediate operations (`STRICT')
     `2'        minimize intermediate overflows (`MINIMIZED')
     `3'        eliminate intermediate overflows (`ELIMINATED')


As with the pragma, if only one digit appears then it applies to all
cases; if two digits are given, then the first applies outside
assertions, and the second within assertions. Thus the equivalent of
the example pragma above would be `-gnato23'.

If no digits follow the `-gnato', then it is equivalent to `-gnato11',
causing all intermediate operations to be computed using the base type
(`STRICT' mode).


File: gnat_ugn.info,  Node: Default Settings,  Next: Implementation Notes,  Prev: Specifying the Desired Mode,  Up: Overflow Check Handling in GNAT

8.4.4 Default Settings
----------------------

The default mode for overflow checks is

         General => Strict

which causes all computations both inside and outside assertions to use
the base type.

This retains compatibility with previous versions of GNAT which
suppressed overflow checks by default and always used the base type for
computation of intermediate results.

The switch `-gnato' (with no digits following) is equivalent to

         General => Strict

which causes overflow checking of all intermediate overflows both
inside and outside assertions against the base type.

The pragma `Suppress (Overflow_Check)' disables overflow checking, but
it has no effect on the method used for computing intermediate results.

The pragma `Unsuppress (Overflow_Check)' enables overflow checking, but
it has no effect on the method used for computing intermediate results.


File: gnat_ugn.info,  Node: Implementation Notes,  Prev: Default Settings,  Up: Overflow Check Handling in GNAT

8.4.5 Implementation Notes
--------------------------

In practice on typical 64-bit machines, the `MINIMIZED' mode is
reasonably efficient, and can be generally used. It also helps to
ensure compatibility with code imported from some other compiler to
GNAT.

Setting all intermediate overflows checking (`CHECKED' mode) makes
sense if you want to make sure that your code is compatible with any
other possible Ada implementation. This may be useful in ensuring
portability for code that is to be exported to some other compiler than
GNAT.

The Ada standard allows the reassociation of expressions at the same
precedence level if no parentheses are present. For example, `A+B+C'
parses as though it were `(A+B)+C', but the compiler can reintepret
this as `A+(B+C)', possibly introducing or eliminating an overflow
exception. The GNAT compiler never takes advantage of this freedom, and
the expression `A+B+C' will be evaluated as `(A+B)+C'.  If you need the
other order, you can write the parentheses explicitly `A+(B+C)' and
GNAT will respect this order.

The use of `ELIMINATED' mode will cause the compiler to automatically
include an appropriate arbitrary precision integer arithmetic package.
The compiler will make calls to this package, though only in cases
where it cannot be sure that `Long_Long_Integer' is sufficient to guard
against intermediate overflows. This package does not use dynamic
alllocation, but it does use the secondary stack, so an appropriate
secondary stack package must be present (this is always true for
standard full Ada, but may require specific steps for restricted run
times such as ZFP).

Although `ELIMINATED' mode causes expressions to use arbitrary
precision arithmetic, avoiding overflow, the final result must be in an
appropriate range. This is true even if the final result is of type
`[Long_[Long_]]Integer'Base', which still has the same bounds as its
associated constrained type at run-time.

Currently, the `ELIMINATED' mode is only available on target platforms
for which `Long_Long_Integer' is 64-bits (nearly all GNAT platforms).


File: gnat_ugn.info,  Node: Performing Dimensionality Analysis in GNAT,  Next: Stack Related Facilities,  Prev: Overflow Check Handling in GNAT,  Up: GNAT and Program Execution

8.5 Performing Dimensionality Analysis in GNAT
==============================================

The GNAT compiler supports dimensionality checking. The user can
specify physical units for objects, and the compiler will verify that
uses of these objects are compatible with their dimensions, in a
fashion that is familiar to engineering practice. The dimensions of
algebraic expressions (including powers with static exponents) are
computed from their constituents.

This feature depends on Ada 2012 aspect specifications, and is
available from version 7.0.1 of GNAT onwards.  The GNAT-specific aspect
`Dimension_System' allows you to define a system of units; the aspect
`Dimension' then allows the user to declare dimensioned quantities
within a given system.  (These aspects are described in the
`Implementation Defined Aspects' chapter of the `GNAT Reference
Manual').

The major advantage of this model is that it does not require the
declaration of multiple operators for all possible combinations of
types: it is only necessary to use the proper subtypes in object
declarations.

The simplest way to impose dimensionality checking on a computation is
to make use of the package `System.Dim.Mks', which is part of the GNAT
library. This package defines a floating-point type `MKS_Type', for
which a sequence of dimension names are specified, together with their
conventional abbreviations.  The following should be read together with
the full specification of the package, in file `s-dimmks.ads'.

         type Mks_Type is new Long_Long_Float
           with
            Dimension_System => (
              (Unit_Name => Meter,    Unit_Symbol => 'm',   Dim_Symbol => 'L'),
              (Unit_Name => Kilogram, Unit_Symbol => "kg",  Dim_Symbol => 'M'),
              (Unit_Name => Second,   Unit_Symbol => 's',   Dim_Symbol => 'T'),
              (Unit_Name => Ampere,   Unit_Symbol => 'A',   Dim_Symbol => 'I'),
              (Unit_Name => Kelvin,   Unit_Symbol => 'K',   Dim_Symbol => "Theta"),
              (Unit_Name => Mole,     Unit_Symbol => "mol", Dim_Symbol => 'N'),
              (Unit_Name => Candela,  Unit_Symbol => "cd",  Dim_Symbol => 'J'));

The package then defines a series of subtypes that correspond to these
conventional units. For example:

         subtype Length is Mks_Type
           with
            Dimension => (Symbol => 'm', Meter  => 1, others => 0);

and similarly for `Mass', `Time', `Electric_Current',
`Thermodynamic_Temperature', `Amount_Of_Substance', and
`Luminous_Intensity' (the standard set of units of the SI system).

The package also defines conventional names for values of each unit, for
example:


as well as useful multiples of these units:

          cm  : constant Length := 1.0E-02;
          g   : constant Mass   := 1.0E-03;
          min : constant Time   := 60.0;
          day : constant Time   := 60.0 * 24.0 * min;
         ...

Using this package, you can then define a derived unit by providing the
aspect that specifies its dimensions within the MKS system, as well as
the string to be used for output of a value of that unit:

         subtype Acceleration is Mks_Type
           with Dimension => ("m/sec^2",
                              Meter => 1,
                              Second => -2,
                              others => 0);

Here is a complete example of use:

         with System.Dim.MKS; use System.Dim.Mks;
         with System.Dim.Mks_IO; use System.Dim.Mks_IO;
         with Text_IO; use Text_IO;
         procedure Free_Fall is
           subtype Acceleration is Mks_Type
             with Dimension => ("m/sec^2", 1, 0, -2, others => 0);
           G : constant acceleration := 9.81 * m / (s ** 2);
           T : Time := 10.0*s;
           Distance : Length;

         begin
           Put ("Gravitational constant: ");
           Put (G, Aft => 2, Exp => 0); Put_Line ("");
           Distance := 0.5 * G * T ** 2;
           Put ("distance travelled in 10 seconds of free fall ");
           Put (Distance, Aft => 2, Exp => 0);
           Put_Line ("");
         end Free_Fall;

Execution of this program yields:

         Gravitational constant:  9.81 m/sec^2
         distance travelled in 10 seconds of free fall 490.50 m

However, incorrect assignments such as:

         Distance := 5.0;
         Distance := 5.0 * kg:

are rejected with the following diagnoses:

         Distance := 5.0;
            >>> dimensions mismatch in assignment
            >>> left-hand side has dimension [L]
            >>> right-hand side is dimensionless

         Distance := 5.0 * kg:
            >>> dimensions mismatch in assignment
            >>> left-hand side has dimension [L]
            >>> right-hand side has dimension [M]

The dimensions of an expression are properly displayed, even if there is
no explicit subtype for it. If we add to the program:

         Put ("Final velocity: ");
         Put (G * T, Aft =>2, Exp =>0);
         Put_Line ("");

then the output includes:

         Final velocity: 98.10 m.s**(-1)


File: gnat_ugn.info,  Node: Stack Related Facilities,  Next: Memory Management Issues,  Prev: Performing Dimensionality Analysis in GNAT,  Up: GNAT and Program Execution

8.6 Stack Related Facilities
============================

This section describes some useful tools associated with stack checking
and analysis. In particular, it deals with dynamic and static stack
usage measurements.

* Menu:

* Stack Overflow Checking::
* Static Stack Usage Analysis::
* Dynamic Stack Usage Analysis::


File: gnat_ugn.info,  Node: Stack Overflow Checking,  Next: Static Stack Usage Analysis,  Up: Stack Related Facilities

8.6.1 Stack Overflow Checking
-----------------------------

For most operating systems, `gcc' does not perform stack overflow
checking by default. This means that if the main environment task or
some other task exceeds the available stack space, then unpredictable
behavior will occur. Most native systems offer some level of protection
by adding a guard page at the end of each task stack. This mechanism is
usually not enough for dealing properly with stack overflow situations
because a large local variable could "jump" above the guard page.
Furthermore, when the guard page is hit, there may not be any space
left on the stack for executing the exception propagation code.
Enabling stack checking avoids such situations.

To activate stack checking, compile all units with the gcc option
`-fstack-check'. For example:

         $ gcc -c -fstack-check package1.adb

Units compiled with this option will generate extra instructions to
check that any use of the stack (for procedure calls or for declaring
local variables in declare blocks) does not exceed the available stack
space.  If the space is exceeded, then a `Storage_Error' exception is
raised.

For declared tasks, the stack size is controlled by the size given in
an applicable `Storage_Size' pragma or by the value specified at bind
time with `-d' (*note Switches for gnatbind: 126.) or is set to the
default size as defined in the GNAT runtime otherwise.

For the environment task, the stack size depends on system defaults and
is unknown to the compiler. Stack checking may still work correctly if
a fixed size stack is allocated, but this cannot be guaranteed.  To
ensure that a clean exception is signalled for stack overflow, set the
environment variable `GNAT_STACK_LIMIT' to indicate the maximum stack
area that can be used, as in:

         $ SET GNAT_STACK_LIMIT 1600

The limit is given in kilobytes, so the above declaration would set the
stack limit of the environment task to 1.6 megabytes.  Note that the
only purpose of this usage is to limit the amount of stack used by the
environment task. If it is necessary to increase the amount of stack
for the environment task, then this is an operating systems issue, and
must be addressed with the appropriate operating systems commands.


File: gnat_ugn.info,  Node: Static Stack Usage Analysis,  Next: Dynamic Stack Usage Analysis,  Prev: Stack Overflow Checking,  Up: Stack Related Facilities

8.6.2 Static Stack Usage Analysis
---------------------------------

A unit compiled with `-fstack-usage' will generate an extra file that
specifies the maximum amount of stack used, on a per-function basis.
The file has the same basename as the target object file with a `.su'
extension.  Each line of this file is made up of three fields:

   * The name of the function.

   * A number of bytes.

   * One or more qualifiers: `static', `dynamic', `bounded'.

The second field corresponds to the size of the known part of the
function frame.

The qualifier `static' means that the function frame size is purely
static.  It usually means that all local variables have a static size.
In this case, the second field is a reliable measure of the function
stack utilization.

The qualifier `dynamic' means that the function frame size is not
static.  It happens mainly when some local variables have a dynamic
size. When this qualifier appears alone, the second field is not a
reliable measure of the function stack analysis. When it is qualified
with  `bounded', it means that the second field is a reliable maximum
of the function stack utilization.

A unit compiled with `-Wstack-usage' will issue a warning for each
subprogram whose stack usage might be larger than the specified amount
of bytes.  The wording is in keeping with the qualifier documented
above.


File: gnat_ugn.info,  Node: Dynamic Stack Usage Analysis,  Prev: Static Stack Usage Analysis,  Up: Stack Related Facilities

8.6.3 Dynamic Stack Usage Analysis
----------------------------------

It is possible to measure the maximum amount of stack used by a task, by
adding a switch to `gnatbind', as:

         $ gnatbind -u0 file

With this option, at each task termination, its stack usage is  output
on `stderr'.  It is not always convenient to output the stack usage
when the program is still running. Hence, it is possible to delay this
output until program termination. for a given number of tasks specified
as the argument of the `-u' option. For instance:

         $ gnatbind -u100 file

will buffer the stack usage information of the first 100 tasks to
terminate and output this info at program termination. Results are
displayed in four columns:

         Index | Task Name | Stack Size | Stack Usage

where:

   * `Index' is a number associated with each task.

   * `Task Name' is the name of the task analyzed.

   * `Stack Size' is the maximum size for the stack.

   * `Stack Usage' is the measure done by the stack analyzer.  In order
     to prevent overflow, the stack is not entirely analyzed, and it's
     not possible to know exactly how much has actually been used.

The environment task stack, e.g., the stack that contains the main
unit, is only processed when the environment variable GNAT_STACK_LIMIT
is set.

The package `GNAT.Task_Stack_Usage' provides facilities to get stack
usage reports at run-time. See its body for the details.


File: gnat_ugn.info,  Node: Memory Management Issues,  Prev: Stack Related Facilities,  Up: GNAT and Program Execution

8.7 Memory Management Issues
============================

This section describes some useful memory pools provided in the GNAT
library and in particular the GNAT Debug Pool facility, which can be
used to detect incorrect uses of access values (including 'dangling
references').

* Menu:

* Some Useful Memory Pools::
* The GNAT Debug Pool Facility::


File: gnat_ugn.info,  Node: Some Useful Memory Pools,  Next: The GNAT Debug Pool Facility,  Up: Memory Management Issues

8.7.1 Some Useful Memory Pools
------------------------------

The `System.Pool_Global' package offers the Unbounded_No_Reclaim_Pool
storage pool. Allocations use the standard system call `malloc' while
deallocations use the standard system call `free'. No reclamation is
performed when the pool goes out of scope. For performance reasons, the
standard default Ada allocators/deallocators do not use any explicit
storage pools but if they did, they could use this storage pool without
any change in behavior. That is why this storage pool is used  when the
user manages to make the default implicit allocator explicit as in this
example:

         type T1 is access Something;
          -- no Storage pool is defined for T2

         type T2 is access Something_Else;
         for T2'Storage_Pool use T1'Storage_Pool;
         -- the above is equivalent to
         for T2'Storage_Pool use System.Pool_Global.Global_Pool_Object;

The `System.Pool_Local' package offers the Unbounded_Reclaim_Pool
storage pool. The allocation strategy is similar to `Pool_Local's
except that the all storage allocated with this pool is reclaimed when
the pool object goes out of scope. This pool provides a explicit
mechanism similar to the implicit one provided by several Ada 83
compilers for allocations performed through a local access type and
whose purpose was to reclaim memory when exiting the scope of a given
local access. As an example, the following program does not leak memory
even though it does not perform explicit deallocation:

         with System.Pool_Local;
         procedure Pooloc1 is
            procedure Internal is
               type A is access Integer;
               X : System.Pool_Local.Unbounded_Reclaim_Pool;
               for A'Storage_Pool use X;
               v : A;
            begin
               for I in  1 .. 50 loop
                  v := new Integer;
               end loop;
            end Internal;
         begin
            for I in  1 .. 100 loop
               Internal;
            end loop;
         end Pooloc1;

The `System.Pool_Size' package implements the Stack_Bounded_Pool used
when `Storage_Size' is specified for an access type.  The whole storage
for the pool is allocated at once, usually on the stack at the point
where the access type is elaborated. It is automatically reclaimed when
exiting the scope where the access type is defined. This package is not
intended to be used directly by the user and it is implicitly used for
each such declaration:

         type T1 is access Something;
         for T1'Storage_Size use 10_000;


File: gnat_ugn.info,  Node: The GNAT Debug Pool Facility,  Prev: Some Useful Memory Pools,  Up: Memory Management Issues

8.7.2 The GNAT Debug Pool Facility
----------------------------------

The use of unchecked deallocation and unchecked conversion can easily
lead to incorrect memory references. The problems generated by such
references are usually difficult to tackle because the symptoms can be
very remote from the origin of the problem. In such cases, it is very
helpful to detect the problem as early as possible. This is the purpose
of the Storage Pool provided by `GNAT.Debug_Pools'.

In order to use the GNAT specific debugging pool, the user must
associate a debug pool object with each of the access types that may be
related to suspected memory problems. See Ada Reference Manual 13.11.

         type Ptr is access Some_Type;
         Pool : GNAT.Debug_Pools.Debug_Pool;
         for Ptr'Storage_Pool use Pool;

`GNAT.Debug_Pools' is derived from a GNAT-specific kind of pool: the
`Checked_Pool'. Such pools, like standard Ada storage pools, allow the
user to redefine allocation and deallocation strategies. They also
provide a checkpoint for each dereference, through the use of the
primitive operation `Dereference' which is implicitly called at each
dereference of an access value.

Once an access type has been associated with a debug pool, operations on
values of the type may raise four distinct exceptions, which correspond
to four potential kinds of memory corruption:

   * `GNAT.Debug_Pools.Accessing_Not_Allocated_Storage'

   * `GNAT.Debug_Pools.Accessing_Deallocated_Storage'

   * `GNAT.Debug_Pools.Freeing_Not_Allocated_Storage'

   * `GNAT.Debug_Pools.Freeing_Deallocated_Storage'

For types associated with a Debug_Pool, dynamic allocation is performed
using the standard GNAT allocation routine. References to all allocated
chunks of memory are kept in an internal dictionary. Several
deallocation strategies are provided, whereupon the user can choose to
release the memory to the system, keep it allocated for further invalid
access checks, or fill it with an easily recognizable pattern for debug
sessions. The memory pattern is the old IBM hexadecimal convention:
`16#DEADBEEF#'.

See the documentation in the file g-debpoo.ads for more information on
the various strategies.

Upon each dereference, a check is made that the access value denotes a
properly allocated memory location. Here is a complete example of use of
`Debug_Pools', that includes typical instances of  memory corruption:

         with Gnat.Io; use Gnat.Io;
         with Unchecked_Deallocation;
         with Unchecked_Conversion;
         with GNAT.Debug_Pools;
         with System.Storage_Elements;
         with Ada.Exceptions; use Ada.Exceptions;
         procedure Debug_Pool_Test is

            type T is access Integer;
            type U is access all T;

            P : GNAT.Debug_Pools.Debug_Pool;
            for T'Storage_Pool use P;

            procedure Free is new Unchecked_Deallocation (Integer, T);
            function UC is new Unchecked_Conversion (U, T);
            A, B : aliased T;

            procedure Info is new GNAT.Debug_Pools.Print_Info(Put_Line);

         begin
            Info (P);
            A := new Integer;
            B := new Integer;
            B := A;
            Info (P);
            Free (A);
            begin
               Put_Line (Integer'Image(B.all));
            exception
               when E : others => Put_Line ("raised: " & Exception_Name (E));
            end;
            begin
               Free (B);
            exception
               when E : others => Put_Line ("raised: " & Exception_Name (E));
            end;
            B := UC(A'Access);
            begin
               Put_Line (Integer'Image(B.all));
            exception
               when E : others => Put_Line ("raised: " & Exception_Name (E));
            end;
            begin
               Free (B);
            exception
               when E : others => Put_Line ("raised: " & Exception_Name (E));
            end;
            Info (P);
         end Debug_Pool_Test;

The debug pool mechanism provides the following precise diagnostics on
the execution of this erroneous program:

         Debug Pool info:
           Total allocated bytes :  0
           Total deallocated bytes :  0
           Current Water Mark:  0
           High Water Mark:  0

         Debug Pool info:
           Total allocated bytes :  8
           Total deallocated bytes :  0
           Current Water Mark:  8
           High Water Mark:  8

         raised: GNAT.DEBUG_POOLS.ACCESSING_DEALLOCATED_STORAGE
         raised: GNAT.DEBUG_POOLS.FREEING_DEALLOCATED_STORAGE
         raised: GNAT.DEBUG_POOLS.ACCESSING_NOT_ALLOCATED_STORAGE
         raised: GNAT.DEBUG_POOLS.FREEING_NOT_ALLOCATED_STORAGE
         Debug Pool info:
           Total allocated bytes :  8
           Total deallocated bytes :  4
           Current Water Mark:  4
           High Water Mark:  8


File: gnat_ugn.info,  Node: Platform-Specific Information,  Next: Example of Binder Output File,  Prev: GNAT and Program Execution,  Up: Top

9 Platform-Specific Information
*******************************

This appendix contains information relating to the implementation of
run-time libraries on various platforms and also covers topics related
to the GNAT implementation on Windows and Mac OS.

* Menu:

* Run-Time Libraries::
* Specifying a Run-Time Library::
* Microsoft Windows Topics::
* Mac OS Topics::


File: gnat_ugn.info,  Node: Run-Time Libraries,  Next: Specifying a Run-Time Library,  Up: Platform-Specific Information

9.1 Run-Time Libraries
======================

The GNAT run-time implementation may vary with respect to both the
underlying threads library and the exception handling scheme.  For
threads support, one or more of the following are supplied:

   * `native threads library', a binding to the thread package from the
     underlying operating system

   * `pthreads library' (Sparc Solaris only), a binding to the Solaris
     POSIX thread package

For exception handling, either or both of two models are supplied:

 
   * `Zero-Cost Exceptions' ("ZCX"), which uses binder-generated tables
     that are interrogated at run time to locate a handler.

   * `setjmp / longjmp' ('SJLJ'), which uses dynamically-set data to
     establish the set of handlers

Most programs should experience a substantial speed improvement by
being compiled with a ZCX run-time.  This is especially true for
tasking applications or applications with many exception handlers.}

This section summarizes which combinations of threads and exception
support are supplied on various GNAT platforms.  It then shows how to
select a particular library either permanently or temporarily, explains
the properties of (and tradeoffs among) the various threads libraries,
and provides some additional information about several specific
platforms.

* Menu:

* Summary of Run-Time Configurations::


File: gnat_ugn.info,  Node: Summary of Run-Time Configurations,  Up: Run-Time Libraries

9.1.1 Summary of Run-Time Configurations
----------------------------------------

Platform              Run-Time           Tasking                       Exceptions
---------------------------------------------------------------------------------------- 
ppc-aix               rts-native         native AIX threads            ZCX
                      (default)                                        
rts-sjlj              native AIX threads SJLJ                          
sparc-solaris         rts-native         native Solaris threads        ZCX
                      (default)          library                       
rts-pthread           pthread library    ZCX                           
rts-sjlj              native Solaris     SJLJ                          
                      threads library                                  
sparc64-solaris       rts-native         native Solaris threads        ZCX
                      (default)          library                       
x86-linux             rts-native         pthread library               ZCX
                      (default)                                        
rts-sjlj              pthread library    SJLJ                          
x86-lynx              rts-native         native LynxOS threads         SJLJ
                      (default)                                        
x86-solaris           rts-native         native Solaris threads        ZCX
                      (default)          library                       
rts-sjlj              native Solaris     SJLJ                          
                      threads library                                  
x86-windows           rts-native         native Win32 threads          ZCX
                      (default)                                        
rts-sjlj              native Win32       SJLJ                          
                      threads                                          
x86_64-linux          rts-native         pthread library               ZCX
                      (default)                                        
rts-sjlj              pthread library    SJLJ                          


File: gnat_ugn.info,  Node: Specifying a Run-Time Library,  Next: Microsoft Windows Topics,  Prev: Run-Time Libraries,  Up: Platform-Specific Information

9.2 Specifying a Run-Time Library
=================================

The `adainclude' subdirectory containing the sources of the GNAT
run-time library, and the `adalib' subdirectory containing the `ALI'
files and the static and/or shared GNAT library, are located in the gcc
target-dependent area:

         target=$prefix/lib/gcc/gcc-*dumpmachine*/gcc-*dumpversion*/

As indicated above, on some platforms several run-time libraries are
supplied.  These libraries are installed in the target dependent area
and contain a complete source and binary subdirectory. The detailed
description below explains the differences between the different
libraries in terms of their thread support.

The default run-time library (when GNAT is installed) is `rts-native'.
This default run time is selected by the means of soft links.  For
example on x86-linux:

    --
    --  $(target-dir)
    --      |
    --      +--- adainclude----------+
    --      |                        |
    --      +--- adalib-----------+  |
    --      |                     |  |
    --      +--- rts-native       |  |
    --      |    |                |  |
    --      |    +--- adainclude <---+
    --      |    |                |
    --      |    +--- adalib <----+
    --      |
    --      +--- rts-sjlj
    --           |
    --           +--- adainclude
    --           |
    --           +--- adalib

If the `rts-sjlj' library is to be selected on a permanent basis, these
soft links can be modified with the following commands:

         $ cd $target
         $ rm -f adainclude adalib
         $ ln -s rts-sjlj/adainclude adainclude
         $ ln -s rts-sjlj/adalib adalib

Alternatively, you can specify `rts-sjlj/adainclude' in the file
`$target/ada_source_path' and `rts-sjlj/adalib' in
`$target/ada_object_path'.

Selecting another run-time library temporarily can be achieved by using
the `-RTS' switch, e.g., `-RTS=sjlj' 

* Menu:

* Choosing the Scheduling Policy::
* Solaris-Specific Considerations::
* Solaris Threads Issues::
* AIX-Specific Considerations::


File: gnat_ugn.info,  Node: Choosing the Scheduling Policy,  Next: Solaris-Specific Considerations,  Up: Specifying a Run-Time Library

9.2.1 Choosing the Scheduling Policy
------------------------------------

When using a POSIX threads implementation, you have a choice of several
scheduling policies: `SCHED_FIFO', `SCHED_RR' and `SCHED_OTHER'.

Typically, the default is `SCHED_OTHER', while using `SCHED_FIFO' or
`SCHED_RR' requires special (e.g., root) privileges.

By default, GNAT uses the `SCHED_OTHER' policy. To specify `SCHED_FIFO',
you can use one of the following:

   * `pragma Time_Slice (0.0)'

   * the corresponding binder option `-T0'

   * `pragma Task_Dispatching_Policy (FIFO_Within_Priorities)'

To specify `SCHED_RR', you should use `pragma Time_Slice' with a value
greater than 0.0, or else use the corresponding `-T' binder option.


File: gnat_ugn.info,  Node: Solaris-Specific Considerations,  Next: Solaris Threads Issues,  Prev: Choosing the Scheduling Policy,  Up: Specifying a Run-Time Library

9.2.2 Solaris-Specific Considerations
-------------------------------------

This section addresses some topics related to the various threads
libraries on Sparc Solaris.


File: gnat_ugn.info,  Node: Solaris Threads Issues,  Next: AIX-Specific Considerations,  Prev: Solaris-Specific Considerations,  Up: Specifying a Run-Time Library

9.2.3 Solaris Threads Issues
----------------------------

GNAT under Solaris/Sparc 32 bits comes with an alternate tasking
run-time library based on POSIX threads -- `rts-pthread'.

This run-time library has the advantage of being mostly shared across
all POSIX-compliant thread implementations, and it also provides under
Solaris 8 the `PTHREAD_PRIO_INHERIT' and `PTHREAD_PRIO_PROTECT'
semantics that can be selected using the predefined pragma
`Locking_Policy' with respectively `Inheritance_Locking' and
`Ceiling_Locking' as the policy.

As explained above, the native run-time library is based on the Solaris
thread library (`libthread') and is the default library.

When the Solaris threads library is used (this is the default), programs
compiled with GNAT can automatically take advantage of and can thus
execute on multiple processors.  The user can alternatively specify a
processor on which the program should run to emulate a single-processor
system. The multiprocessor / uniprocessor choice is made by setting the
environment variable `GNAT_PROCESSOR' to one of the following:

      `GNAT_PROCESSOR' Value        Effect
     ------------------------------------------------------------------------------------------------------ 
     `-2'                          Use the default configuration (run the program on all available
                                   processors) - this is the same as having `GNAT_PROCESSOR' unset
     `-1'                          Let the run-time implementation choose one processor and run the
                                   program on that processor
     `0 .. Last_Proc'              Run the program on the specified processor.  `Last_Proc' is equal to
                                   `_SC_NPROCESSORS_CONF - 1' (where `_SC_NPROCESSORS_CONF' is a system
                                   variable).



File: gnat_ugn.info,  Node: AIX-Specific Considerations,  Prev: Solaris Threads Issues,  Up: Specifying a Run-Time Library

9.2.4 AIX-Specific Considerations
---------------------------------

On AIX, the resolver library initializes some internal structure on the
first call to `get*by*' functions, which are used to implement
`GNAT.Sockets.Get_Host_By_Name' and `GNAT.Sockets.Get_Host_By_Address'.
If such initialization occurs within an Ada task, and the stack size for
the task is the default size, a stack overflow may occur.

To avoid this overflow, the user should either ensure that the first
call to `GNAT.Sockets.Get_Host_By_Name' or
`GNAT.Sockets.Get_Host_By_Addrss' occurs in the environment task, or
use `pragma Storage_Size' to specify a sufficiently large size for the
stack of the task that contains this call.


File: gnat_ugn.info,  Node: Microsoft Windows Topics,  Next: Mac OS Topics,  Prev: Specifying a Run-Time Library,  Up: Platform-Specific Information

9.3 Microsoft Windows Topics
============================

This section describes topics that are specific to the Microsoft Windows
platforms.

* Menu:

* Using GNAT on Windows::
* Using a network installation of GNAT::
* CONSOLE and WINDOWS subsystems::
* Temporary Files::
* Mixed-Language Programming on Windows::
* Windows Specific Add-Ons::


File: gnat_ugn.info,  Node: Using GNAT on Windows,  Next: Using a network installation of GNAT,  Up: Microsoft Windows Topics

9.3.1 Using GNAT on Windows
---------------------------

One of the strengths of the GNAT technology is that its tool set
(`gcc', `gnatbind', `gnatlink', `gnatmake', the `gdb' debugger, etc.)
is used in the same way regardless of the platform.

On Windows this tool set is complemented by a number of
Microsoft-specific tools that have been provided to facilitate
interoperability with Windows when this is required. With these tools:

   * You can build applications using the `CONSOLE' or `WINDOWS'
     subsystems.

   * You can use any Dynamically Linked Library (DLL) in your Ada code
     (both relocatable and non-relocatable DLLs are supported).

   * You can build Ada DLLs for use in other applications. These
     applications can be written in a language other than Ada (e.g., C,
     C++, etc). Again both relocatable and non-relocatable Ada DLLs are
     supported.

   * You can include Windows resources in your Ada application.

   * You can use or create COM/DCOM objects.

Immediately below are listed all known general GNAT-for-Windows
restrictions.  Other restrictions about specific features like Windows
Resources and DLLs are listed in separate sections below.

   * It is not possible to use `GetLastError' and `SetLastError' when
     tasking, protected records, or exceptions are used. In these
     cases, in order to implement Ada semantics, the GNAT run-time
     system calls certain Win32 routines that set the last error
     variable to 0 upon success. It should be possible to use
     `GetLastError' and `SetLastError' when tasking, protected record,
     and exception features are not used, but it is not guaranteed to
     work.

   * It is not possible to link against Microsoft C++ libraries except
     for import libraries. Interfacing must be done by the mean of DLLs.

   * It is possible to link against Microsoft C libraries. Yet the
     preferred solution is to use C/C++ compiler that comes with GNAT,
     since it doesn't require having two different development
     environments and makes the inter-language debugging experience
     smoother.

   * When the compilation environment is located on FAT32 drives, users
     may experience recompilations of the source files that have not
     changed if Daylight Saving Time (DST) state has changed since the
     last time files were compiled. NTFS drives do not have this
     problem.

   * No components of the GNAT toolset use any entries in the Windows
     registry. The only entries that can be created are file
     associations and PATH settings, provided the user has chosen to
     create them at installation time, as well as some minimal
     book-keeping information needed to correctly uninstall or
     integrate different GNAT products.


File: gnat_ugn.info,  Node: Using a network installation of GNAT,  Next: CONSOLE and WINDOWS subsystems,  Prev: Using GNAT on Windows,  Up: Microsoft Windows Topics

9.3.2 Using a network installation of GNAT
------------------------------------------

Make sure the system on which GNAT is installed is accessible from the
current machine, i.e., the install location is shared over the network.
Shared resources are accessed on Windows by means of UNC paths, which
have the format `\\server\sharename\path'

In order to use such a network installation, simply add the UNC path of
the `bin' directory of your GNAT installation in front of your PATH. For
example, if GNAT is installed in `\GNAT' directory of a share location
called `c-drive' on a machine `LOKI', the following command will make
it available:

         $ path \\loki\c-drive\gnat\bin;%path%`

Be aware that every compilation using the network installation results
in the transfer of large amounts of data across the network and will
likely cause serious performance penalty.


File: gnat_ugn.info,  Node: CONSOLE and WINDOWS subsystems,  Next: Temporary Files,  Prev: Using a network installation of GNAT,  Up: Microsoft Windows Topics

9.3.3 CONSOLE and WINDOWS subsystems
------------------------------------

There are two main subsystems under Windows. The `CONSOLE' subsystem
(which is the default subsystem) will always create a console when
launching the application. This is not something desirable when the
application has a Windows GUI. To get rid of this console the
application must be using the `WINDOWS' subsystem. To do so the
`-mwindows' linker option must be specified.

         $ gnatmake winprog -largs -mwindows


File: gnat_ugn.info,  Node: Temporary Files,  Next: Mixed-Language Programming on Windows,  Prev: CONSOLE and WINDOWS subsystems,  Up: Microsoft Windows Topics

9.3.4 Temporary Files
---------------------

It is possible to control where temporary files gets created by setting
the `TMP' environment variable. The file will be created:

   * Under the directory pointed to by the `TMP' environment variable if
     this directory exists.

   * Under `c:\temp', if the `TMP' environment variable is not set (or
     not pointing to a directory) and if this directory exists.

   * Under the current working directory otherwise.

This allows you to determine exactly where the temporary file will be
created. This is particularly useful in networked environments where
you may not have write access to some directories.


File: gnat_ugn.info,  Node: Mixed-Language Programming on Windows,  Next: Windows Specific Add-Ons,  Prev: Temporary Files,  Up: Microsoft Windows Topics

9.3.5 Mixed-Language Programming on Windows
-------------------------------------------

Developing pure Ada applications on Windows is no different than on
other GNAT-supported platforms. However, when developing or porting an
application that contains a mix of Ada and C/C++, the choice of your
Windows C/C++ development environment conditions your overall
interoperability strategy.

If you use `gcc' or Microsoft C to compile the non-Ada part of your
application, there are no Windows-specific restrictions that affect the
overall interoperability with your Ada code. If you do want to use the
Microsoft tools for your C++ code, you have two choices:

   * Encapsulate your C++ code in a DLL to be linked with your Ada
     application. In this case, use the Microsoft or whatever
     environment to build the DLL and use GNAT to build your executable
     (*note Using DLLs with GNAT: 275.).

   * Or you can encapsulate your Ada code in a DLL to be linked with the
     other part of your application. In this case, use GNAT to build
     the DLL (*note Building DLLs with GNAT Project files: 276.) and
     use the Microsoft or whatever environment to build your executable.

In addition to the description about C main in *note Mixed Language
Programming: 46. section, if the C main uses a stand-alone library it
is required on x86-windows to setup the SEH context. For this the C
main must looks like this:

         /* main.c */
         extern void adainit (void);
         extern void adafinal (void);
         extern void __gnat_initialize(void*);
         extern void call_to_ada (void);

         int main (int argc, char *argv[])
         {
           int SEH [2];

           /* Initialize the SEH context */
           __gnat_initialize (&SEH);

           adainit();

           /* Then call Ada services in the stand-alone library */

           call_to_ada();

           adafinal();
         }

Note that this is not needed on x86_64-windows where the Windows native
SEH support is used.

* Menu:

* Windows Calling Conventions::
* Introduction to Dynamic Link Libraries (DLLs): Introduction to Dynamic Link Libraries DLLs.
* Using DLLs with GNAT::
* Building DLLs with GNAT Project files::
* Building DLLs with GNAT::
* Building DLLs with gnatdll::
* Ada DLLs and Finalization::
* Creating a Spec for Ada DLLs::
* GNAT and Windows Resources::
* Using GNAT DLLs from Microsoft Visual Studio Applications::
* Debugging a DLL::
* Setting Stack Size from gnatlink::
* Setting Heap Size from gnatlink::


File: gnat_ugn.info,  Node: Windows Calling Conventions,  Next: Introduction to Dynamic Link Libraries DLLs,  Up: Mixed-Language Programming on Windows

9.3.5.1 Windows Calling Conventions
...................................

This section pertain only to Win32. On Win64 there is a single native
calling convention. All convention specifiers are ignored on this
platform.

When a subprogram `F' (caller) calls a subprogram `G' (callee), there
are several ways to push `G's parameters on the stack and there are
several possible scenarios to clean up the stack upon `G's return. A
calling convention is an agreed upon software protocol whereby the
responsibilities between the caller (`F') and the callee (`G') are
clearly defined. Several calling conventions are available for Windows:

   * `C' (Microsoft defined)

   * `Stdcall' (Microsoft defined)

   * `Win32' (GNAT specific)

   * `DLL' (GNAT specific)

* Menu:

* C Calling Convention::
* Stdcall Calling Convention::
* Win32 Calling Convention::
* DLL Calling Convention::


File: gnat_ugn.info,  Node: C Calling Convention,  Next: Stdcall Calling Convention,  Up: Windows Calling Conventions

9.3.5.2 `C' Calling Convention
..............................

This is the default calling convention used when interfacing to C/C++
routines compiled with either `gcc' or Microsoft Visual C++.

In the `C' calling convention subprogram parameters are pushed on the
stack by the caller from right to left. The caller itself is in charge
of cleaning up the stack after the call. In addition, the name of a
routine with `C' calling convention is mangled by adding a leading
underscore.

The name to use on the Ada side when importing (or exporting) a routine
with `C' calling convention is the name of the routine. For instance
the C function:

         int get_val (long);

should be imported from Ada as follows:

         function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
         pragma Import (C, Get_Val, External_Name => "get_val");

Note that in this particular case the `External_Name' parameter could
have been omitted since, when missing, this parameter is taken to be the
name of the Ada entity in lower case. When the `Link_Name' parameter is
missing, as in the above example, this parameter is set to be the
`External_Name' with a leading underscore.

When importing a variable defined in C, you should always use the `C'
calling convention unless the object containing the variable is part of
a DLL (in which case you should use the `Stdcall' calling convention,
*note Stdcall Calling Convention: 27b.).


File: gnat_ugn.info,  Node: Stdcall Calling Convention,  Next: Win32 Calling Convention,  Prev: C Calling Convention,  Up: Windows Calling Conventions

9.3.5.3 `Stdcall' Calling Convention
....................................

This convention, which was the calling convention used for Pascal
programs, is used by Microsoft for all the routines in the Win32 API for
efficiency reasons. It must be used to import any routine for which this
convention was specified.

In the `Stdcall' calling convention subprogram parameters are pushed on
the stack by the caller from right to left. The callee (and not the
caller) is in charge of cleaning the stack on routine exit. In addition,
the name of a routine with `Stdcall' calling convention is mangled by
adding a leading underscore (as for the `C' calling convention) and a
trailing `@`nn'', where `nn' is the overall size (in bytes) of the
parameters passed to the routine.

The name to use on the Ada side when importing a C routine with a
`Stdcall' calling convention is the name of the C routine. The leading
underscore and trailing `@`nn'' are added automatically by the
compiler. For instance the Win32 function:

         APIENTRY int get_val (long);

should be imported from Ada as follows:

         function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
         pragma Import (Stdcall, Get_Val);
         --  On the x86 a long is 4 bytes, so the Link_Name is "_get_val@4"

As for the `C' calling convention, when the `External_Name' parameter
is missing, it is taken to be the name of the Ada entity in lower case.
If instead of writing the above import pragma you write:

         function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
         pragma Import (Stdcall, Get_Val, External_Name => "retrieve_val");

then the imported routine is `_retrieve_val@4'. However, if instead of
specifying the `External_Name' parameter you specify the `Link_Name' as
in the following example:

         function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
         pragma Import (Stdcall, Get_Val, Link_Name => "retrieve_val");

then the imported routine is `retrieve_val', that is, there is no
decoration at all. No leading underscore and no Stdcall suffix `@`nn''.

This is especially important as in some special cases a DLL's entry
point name lacks a trailing `@`nn'' while the exported name generated
for a call has it.

It is also possible to import variables defined in a DLL by using an
import pragma for a variable. As an example, if a DLL contains a
variable defined as:

         int my_var;

then, to access this variable from Ada you should write:

         My_Var : Interfaces.C.int;
         pragma Import (Stdcall, My_Var);

Note that to ease building cross-platform bindings this convention will
be handled as a `C' calling convention on non-Windows platforms.


File: gnat_ugn.info,  Node: Win32 Calling Convention,  Next: DLL Calling Convention,  Prev: Stdcall Calling Convention,  Up: Windows Calling Conventions

9.3.5.4 `Win32' Calling Convention
..................................

This convention, which is GNAT-specific is fully equivalent to the
`Stdcall' calling convention described above.


File: gnat_ugn.info,  Node: DLL Calling Convention,  Prev: Win32 Calling Convention,  Up: Windows Calling Conventions

9.3.5.5 `DLL' Calling Convention
................................

This convention, which is GNAT-specific is fully equivalent to the
`Stdcall' calling convention described above.


File: gnat_ugn.info,  Node: Introduction to Dynamic Link Libraries DLLs,  Next: Using DLLs with GNAT,  Prev: Windows Calling Conventions,  Up: Mixed-Language Programming on Windows

9.3.5.6 Introduction to Dynamic Link Libraries (DLLs)
.....................................................

A Dynamically Linked Library (DLL) is a library that can be shared by
several applications running under Windows. A DLL can contain any
number of routines and variables.

One advantage of DLLs is that you can change and enhance them without
forcing all the applications that depend on them to be relinked or
recompiled. However, you should be aware than all calls to DLL routines
are slower since, as you will understand below, such calls are indirect.

To illustrate the remainder of this section, suppose that an application
wants to use the services of a DLL `API.dll'. To use the services
provided by `API.dll' you must statically link against the DLL or an
import library which contains a jump table with an entry for each
routine and variable exported by the DLL. In the Microsoft world this
import library is called `API.lib'. When using GNAT this import library
is called either `libAPI.dll.a', `libapi.dll.a', `libAPI.a' or
`libapi.a' (names are case insensitive).

After you have linked your application with the DLL or the import
library and you run your application, here is what happens:

   * Your application is loaded into memory.

   * The DLL `API.dll' is mapped into the address space of your
     application. This means that:

        - The DLL will use the stack of the calling thread.

        - The DLL will use the virtual address space of the calling
          process.

        - The DLL will allocate memory from the virtual address space
          of the calling process.

        - Handles (pointers) can be safely exchanged between routines
          in the DLL routines and routines in the application using the
          DLL.

   * The entries in the jump table (from the import library
     `libAPI.dll.a' or `API.lib' or automatically created when linking
     against a DLL) which is part of your application are initialized
     with the addresses of the routines and variables in `API.dll'.

   * If present in `API.dll', routines `DllMain' or `DllMainCRTStartup'
     are invoked. These routines typically contain the initialization
     code needed for the well-being of the routines and variables
     exported by the DLL.

There is an additional point which is worth mentioning. In the Windows
world there are two kind of DLLs: relocatable and non-relocatable DLLs.
Non-relocatable DLLs can only be loaded at a very specific address in
the target application address space. If the addresses of two
non-relocatable DLLs overlap and these happen to be used by the same
application, a conflict will occur and the application will run
incorrectly. Hence, when possible, it is always preferable to use and
build relocatable DLLs. Both relocatable and non-relocatable DLLs are
supported by GNAT. Note that the `-s' linker option (see GNU Linker
User's Guide) removes the debugging symbols from the DLL but the DLL can
still be relocated.

As a side note, an interesting difference between Microsoft DLLs and
Unix shared libraries, is the fact that on most Unix systems all public
routines are exported by default in a Unix shared library, while under
Windows it is possible (but not required) to list exported routines in
a definition file (see *note The Definition File: 283.).


File: gnat_ugn.info,  Node: Using DLLs with GNAT,  Next: Building DLLs with GNAT Project files,  Prev: Introduction to Dynamic Link Libraries DLLs,  Up: Mixed-Language Programming on Windows

9.3.5.7 Using DLLs with GNAT
............................

To use the services of a DLL, say `API.dll', in your Ada application
you must have:

   * The Ada spec for the routines and/or variables you want to access
     in `API.dll'. If not available this Ada spec must be built from
     the C/C++ header files provided with the DLL.

   * The import library (`libAPI.dll.a' or `API.lib'). As previously
     mentioned an import library is a statically linked library
     containing the import table which will be filled at load time to
     point to the actual `API.dll' routines. Sometimes you don't have
     an import library for the DLL you want to use. The following
     sections will explain how to build one. Note that this is optional.

   * The actual DLL, `API.dll'.

Once you have all the above, to compile an Ada application that uses the
services of `API.dll' and whose main subprogram is `My_Ada_App', you
simply issue the command

         $ gnatmake my_ada_app -largs -lAPI

The argument `-largs -lAPI' at the end of the `gnatmake' command tells
the GNAT linker to look for an import library. The linker will look for
a library name in this specific order:

   * `libAPI.dll.a'

   * `API.dll.a'

   * `libAPI.a'

   * `API.lib'

   * `libAPI.dll'

   * `API.dll'

The first three are the GNU style import libraries. The third is the
Microsoft style import libraries. The last two are the actual DLL names.

Note that if the Ada package spec for `API.dll' contains the following
pragma

         pragma Linker_Options ("-lAPI");

you do not have to add `-largs -lAPI' at the end of the `gnatmake'
command.

If any one of the items above is missing you will have to create it
yourself. The following sections explain how to do so using as an
example a fictitious DLL called `API.dll'.

* Menu:

* Creating an Ada Spec for the DLL Services::
* Creating an Import Library::


File: gnat_ugn.info,  Node: Creating an Ada Spec for the DLL Services,  Next: Creating an Import Library,  Up: Using DLLs with GNAT

9.3.5.8 Creating an Ada Spec for the DLL Services
.................................................

A DLL typically comes with a C/C++ header file which provides the
definitions of the routines and variables exported by the DLL. The Ada
equivalent of this header file is a package spec that contains
definitions for the imported entities. If the DLL you intend to use
does not come with an Ada spec you have to generate one such spec
yourself. For example if the header file of `API.dll' is a file `api.h'
containing the following two definitions:

         int some_var;
         int get (char *);

then the equivalent Ada spec could be:

         with Interfaces.C.Strings;
         package API is
            use Interfaces;

            Some_Var : C.int;
            function Get (Str : C.Strings.Chars_Ptr) return C.int;

         private
            pragma Import (C, Get);
            pragma Import (DLL, Some_Var);
         end API;


File: gnat_ugn.info,  Node: Creating an Import Library,  Prev: Creating an Ada Spec for the DLL Services,  Up: Using DLLs with GNAT

9.3.5.9 Creating an Import Library
..................................

If a Microsoft-style import library `API.lib' or a GNAT-style import
library `libAPI.dll.a' or `libAPI.a' is available with `API.dll' you
can skip this section. You can also skip this section if `API.dll' or
`libAPI.dll' is built with GNU tools as in this case it is possible to
link directly against the DLL. Otherwise read on.

The Definition File
...................

As previously mentioned, and unlike Unix systems, the list of symbols
that are exported from a DLL must be provided explicitly in Windows.
The main goal of a definition file is precisely that: list the symbols
exported by a DLL. A definition file (usually a file with a `.def'
suffix) has the following structure:

         [LIBRARY `name`]
         [DESCRIPTION `string`]
         EXPORTS
            `symbol1`
            `symbol2`
            ...

`LIBRARY `name`'
     This section, which is optional, gives the name of the DLL.

`DESCRIPTION `string`'
     This section, which is optional, gives a description string that
     will be embedded in the import library.

`EXPORTS'
     This section gives the list of exported symbols (procedures,
     functions or variables). For instance in the case of `API.dll' the
     `EXPORTS' section of `API.def' looks like:

         EXPORTS
            some_var
            get

Note that you must specify the correct suffix (`@`nn'') (see *note
Windows Calling Conventions: 277.) for a Stdcall calling convention
function in the exported symbols list.

There can actually be other sections in a definition file, but these
sections are not relevant to the discussion at hand.

Creating a Definition File Automatically
........................................

You can automatically create the definition file `API.def' (see *note
The Definition File: 283.) from a DLL.  For that use the `dlltool'
program as follows:

         $ dlltool API.dll -z API.def --export-all-symbols

     Note that if some routines in the DLL have the `Stdcall' convention
     (*note Windows Calling Conventions: 277.) with stripped `@`nn''
     suffix then you'll have to edit `api.def' to add it, and specify
     `-k' to `gnatdll' when creating the import library.

     Here are some hints to find the right `@`nn'' suffix.

        - If you have the Microsoft import library (.lib), it is
          possible to get the right symbols by using Microsoft
          `dumpbin' tool (see the corresponding Microsoft documentation
          for further details).

              $ dumpbin /exports api.lib

        - If you have a message about a missing symbol at link time the
          compiler tells you what symbol is expected. You just have to
          go back to the definition file and add the right suffix.

GNAT-Style Import Library
.........................

To create a static import library from `API.dll' with the GNAT tools
you should create the .def file, then use `gnatdll' tool (see *note
Using gnatdll: 28b.) as follows:

         $ gnatdll -e API.def -d API.dll

     `gnatdll' takes as input a definition file `API.def' and the name
     of the DLL containing the services listed in the definition file
     `API.dll'. The name of the static import library generated is
     computed from the name of the definition file as follows: if the
     definition file name is `xyz`'.def`, the import library name will
     be `lib``xyz`'.a`. Note that in the previous example option `-e'
     could have been removed because the name of the definition file
     (before the '`.def' suffix) is the same as the name of the DLL
     (*note Using gnatdll: 28b. for more information about `gnatdll').

Microsoft-Style Import Library
..............................

A Microsoft import library is needed only if you plan to make an Ada
DLL available to applications developed with Microsoft tools (*note
Mixed-Language Programming on Windows: 273.).

To create a Microsoft-style import library for `API.dll' you should
create the .def file, then build the actual import library using
Microsoft's `lib' utility:

         $ lib -machine:IX86 -def:API.def -out:API.lib

     If you use the above command the definition file `API.def' must
     contain a line giving the name of the DLL:

         LIBRARY      "API"

     See the Microsoft documentation for further details about the
     usage of `lib'.


File: gnat_ugn.info,  Node: Building DLLs with GNAT Project files,  Next: Building DLLs with GNAT,  Prev: Using DLLs with GNAT,  Up: Mixed-Language Programming on Windows

9.3.5.10 Building DLLs with GNAT Project files
..............................................

There is nothing specific to Windows in the build process.  *note
Library Projects: 8a.

Due to a system limitation, it is not possible under Windows to create
threads when inside the `DllMain' routine which is used for
auto-initialization of shared libraries, so it is not possible to have
library level tasks in SALs.


File: gnat_ugn.info,  Node: Building DLLs with GNAT,  Next: Building DLLs with gnatdll,  Prev: Building DLLs with GNAT Project files,  Up: Mixed-Language Programming on Windows

9.3.5.11 Building DLLs with GNAT
................................

This section explain how to build DLLs using the GNAT built-in DLL
support. With the following procedure it is straight forward to build
and use DLLs with GNAT.

   * Building object files.  The first step is to build all objects
     files that are to be included into the DLL. This is done by using
     the standard `gnatmake' tool.

   * Building the DLL.  To build the DLL you must use `gcc''s `-shared'
     and `-shared-libgcc' options. It is quite simple to use this
     method:

         $ gcc -shared -shared-libgcc -o api.dll obj1.o obj2.o ...

     It is important to note that in this case all symbols found in the
     object files are automatically exported. It is possible to restrict
     the set of symbols to export by passing to `gcc' a definition file
     (see *note The Definition File: 283.).  For example:

         $ gcc -shared -shared-libgcc -o api.dll api.def obj1.o obj2.o ...

     If you use a definition file you must export the elaboration
     procedures for every package that required one. Elaboration
     procedures are named using the package name followed by "_E".

   * Preparing DLL to be used.  For the DLL to be used by client
     programs the bodies must be hidden from it and the .ali set with
     read-only attribute. This is very important otherwise GNAT will
     recompile all packages and will not actually use the code in the
     DLL. For example:

         $ mkdir apilib
         $ copy *.ads *.ali api.dll apilib
         $ attrib +R apilib\\*.ali

At this point it is possible to use the DLL by directly linking against
it. Note that you must use the GNAT shared runtime when using GNAT
shared libraries. This is achieved by using `-shared' binder's option.

         $ gnatmake main -Iapilib -bargs -shared -largs -Lapilib -lAPI


File: gnat_ugn.info,  Node: Building DLLs with gnatdll,  Next: Ada DLLs and Finalization,  Prev: Building DLLs with GNAT,  Up: Mixed-Language Programming on Windows

9.3.5.12 Building DLLs with gnatdll
...................................

Note that it is preferred to use GNAT Project files (*note Building
DLLs with GNAT Project files: 276.) or the built-in GNAT DLL support
(*note Building DLLs with GNAT: 28e.) or to build DLLs.

This section explains how to build DLLs containing Ada code using
`gnatdll'. These DLLs will be referred to as Ada DLLs in the remainder
of this section.

The steps required to build an Ada DLL that is to be used by Ada as
well as non-Ada applications are as follows:

   * You need to mark each Ada `entity' exported by the DLL with a `C'
     or `Stdcall' calling convention to avoid any Ada name mangling for
     the entities exported by the DLL (see *note Exporting Ada
     Entities: 292.). You can skip this step if you plan to use the Ada
     DLL only from Ada applications.

   * Your Ada code must export an initialization routine which calls
     the routine `adainit' generated by `gnatbind' to perform the
     elaboration of the Ada code in the DLL (*note Ada DLLs and
     Elaboration: 293.). The initialization routine exported by the Ada
     DLL must be invoked by the clients of the DLL to initialize the
     DLL.

   * When useful, the DLL should also export a finalization routine
     which calls routine `adafinal' generated by `gnatbind' to perform
     the finalization of the Ada code in the DLL (*note Ada DLLs and
     Finalization: 294.).  The finalization routine exported by the Ada
     DLL must be invoked by the clients of the DLL when the DLL
     services are no further needed.

   * You must provide a spec for the services exported by the Ada DLL
     in each of the programming languages to which you plan to make the
     DLL available.

   * You must provide a definition file listing the exported entities
     (*note The Definition File: 283.).

   * Finally you must use `gnatdll' to produce the DLL and the import
     library (*note Using gnatdll: 28b.).

Note that a relocatable DLL stripped using the `strip' binutils tool
will not be relocatable anymore. To build a DLL without debug
information pass `-largs -s' to `gnatdll'. This restriction does not
apply to a DLL built using a Library Project.  See *note Library
Projects: 8a.

* Menu:

* Limitations When Using Ada DLLs from Ada::
* Exporting Ada Entities::
* Ada DLLs and Elaboration::


File: gnat_ugn.info,  Node: Limitations When Using Ada DLLs from Ada,  Next: Exporting Ada Entities,  Up: Building DLLs with gnatdll

9.3.5.13 Limitations When Using Ada DLLs from Ada
.................................................

When using Ada DLLs from Ada applications there is a limitation users
should be aware of. Because on Windows the GNAT run time is not in a
DLL of its own, each Ada DLL includes a part of the GNAT run time.
Specifically, each Ada DLL includes the services of the GNAT run time
that are necessary to the Ada code inside the DLL. As a result, when an
Ada program uses an Ada DLL there are two independent GNAT run times:
one in the Ada DLL and one in the main program.

It is therefore not possible to exchange GNAT run-time objects between
the Ada DLL and the main Ada program. Example of GNAT run-time objects
are file handles (e.g., `Text_IO.File_Type'), tasks types, protected
objects types, etc.

It is completely safe to exchange plain elementary, array or record
types, Windows object handles, etc.


File: gnat_ugn.info,  Node: Exporting Ada Entities,  Next: Ada DLLs and Elaboration,  Prev: Limitations When Using Ada DLLs from Ada,  Up: Building DLLs with gnatdll

9.3.5.14 Exporting Ada Entities
...............................

Building a DLL is a way to encapsulate a set of services usable from any
application. As a result, the Ada entities exported by a DLL should be
exported with the `C' or `Stdcall' calling conventions to avoid any Ada
name mangling. As an example here is an Ada package `API', spec and
body, exporting two procedures, a function, and a variable:

         with Interfaces.C; use Interfaces;
         package API is
            Count : C.int := 0;
            function Factorial (Val : C.int) return C.int;

            procedure Initialize_API;
            procedure Finalize_API;
            --  Initialization & Finalization routines. More in the next section.
         private
            pragma Export (C, Initialize_API);
            pragma Export (C, Finalize_API);
            pragma Export (C, Count);
            pragma Export (C, Factorial);
         end API;

         package body API is
            function Factorial (Val : C.int) return C.int is
               Fact : C.int := 1;
            begin
               Count := Count + 1;
               for K in 1 .. Val loop
                  Fact := Fact * K;
               end loop;
               return Fact;
            end Factorial;

            procedure Initialize_API is
               procedure Adainit;
               pragma Import (C, Adainit);
            begin
               Adainit;
            end Initialize_API;

            procedure Finalize_API is
               procedure Adafinal;
               pragma Import (C, Adafinal);
            begin
               Adafinal;
            end Finalize_API;
         end API;

If the Ada DLL you are building will only be used by Ada applications
you do not have to export Ada entities with a `C' or `Stdcall'
convention. As an example, the previous package could be written as
follows:

         package API is
            Count : Integer := 0;
            function Factorial (Val : Integer) return Integer;

            procedure Initialize_API;
            procedure Finalize_API;
            --  Initialization and Finalization routines.
         end API;

         package body API is
            function Factorial (Val : Integer) return Integer is
               Fact : Integer := 1;
            begin
               Count := Count + 1;
               for K in 1 .. Val loop
                  Fact := Fact * K;
               end loop;
               return Fact;
            end Factorial;

            ...
            --  The remainder of this package body is unchanged.
         end API;

Note that if you do not export the Ada entities with a `C' or `Stdcall'
convention you will have to provide the mangled Ada names in the
definition file of the Ada DLL (*note Creating the Definition File:
297.).


File: gnat_ugn.info,  Node: Ada DLLs and Elaboration,  Prev: Exporting Ada Entities,  Up: Building DLLs with gnatdll

9.3.5.15 Ada DLLs and Elaboration
.................................

The DLL that you are building contains your Ada code as well as all the
routines in the Ada library that are needed by it. The first thing a
user of your DLL must do is elaborate the Ada code (*note Elaboration
Order Handling in GNAT: 11.).

To achieve this you must export an initialization routine
(`Initialize_API' in the previous example), which must be invoked
before using any of the DLL services. This elaboration routine must call
the Ada elaboration routine `adainit' generated by the GNAT binder
(*note Binding with Non-Ada Main Programs: ba.). See the body of
`Initialize_Api' for an example. Note that the GNAT binder is
automatically invoked during the DLL build process by the `gnatdll'
tool (*note Using gnatdll: 28b.).

When a DLL is loaded, Windows systematically invokes a routine called
`DllMain'. It would therefore be possible to call `adainit' directly
from `DllMain' without having to provide an explicit initialization
routine. Unfortunately, it is not possible to call `adainit' from the
`DllMain' if your program has library level tasks because access to the
`DllMain' entry point is serialized by the system (that is, only a
single thread can execute 'through' it at a time), which means that the
GNAT run time will deadlock waiting for the newly created task to
complete its initialization.


File: gnat_ugn.info,  Node: Ada DLLs and Finalization,  Next: Creating a Spec for Ada DLLs,  Prev: Building DLLs with gnatdll,  Up: Mixed-Language Programming on Windows

9.3.5.16 Ada DLLs and Finalization
..................................

When the services of an Ada DLL are no longer needed, the client code
should invoke the DLL finalization routine, if available. The DLL
finalization routine is in charge of releasing all resources acquired
by the DLL. In the case of the Ada code contained in the DLL, this is
achieved by calling routine `adafinal' generated by the GNAT binder
(*note Binding with Non-Ada Main Programs: ba.).  See the body of
`Finalize_Api' for an example. As already pointed out the GNAT binder
is automatically invoked during the DLL build process by the `gnatdll'
tool (*note Using gnatdll: 28b.).


File: gnat_ugn.info,  Node: Creating a Spec for Ada DLLs,  Next: GNAT and Windows Resources,  Prev: Ada DLLs and Finalization,  Up: Mixed-Language Programming on Windows

9.3.5.17 Creating a Spec for Ada DLLs
.....................................

To use the services exported by the Ada DLL from another programming
language (e.g., C), you have to translate the specs of the exported Ada
entities in that language. For instance in the case of `API.dll', the
corresponding C header file could look like:

         extern int *_imp__count;
         #define count (*_imp__count)
         int factorial (int);

It is important to understand that when building an Ada DLL to be used
by other Ada applications, you need two different specs for the packages
contained in the DLL: one for building the DLL and the other for using
the DLL. This is because the `DLL' calling convention is needed to use
a variable defined in a DLL, but when building the DLL, the variable
must have either the `Ada' or `C' calling convention. As an example
consider a DLL comprising the following package `API':

         package API is
            Count : Integer := 0;
            ...
            --  Remainder of the package omitted.
         end API;

After producing a DLL containing package `API', the spec that must be
used to import `API.Count' from Ada code outside of the DLL is:

         package API is
            Count : Integer;
            pragma Import (DLL, Count);
         end API;

* Menu:

* Creating the Definition File::
* Using gnatdll::


File: gnat_ugn.info,  Node: Creating the Definition File,  Next: Using gnatdll,  Up: Creating a Spec for Ada DLLs

9.3.5.18 Creating the Definition File
.....................................

The definition file is the last file needed to build the DLL. It lists
the exported symbols. As an example, the definition file for a DLL
containing only package `API' (where all the entities are exported with
a `C' calling convention) is:

         EXPORTS
             count
             factorial
             finalize_api
             initialize_api

If the `C' calling convention is missing from package `API', then the
definition file contains the mangled Ada names of the above entities,
which in this case are:

         EXPORTS
             api__count
             api__factorial
             api__finalize_api
             api__initialize_api


File: gnat_ugn.info,  Node: Using gnatdll,  Prev: Creating the Definition File,  Up: Creating a Spec for Ada DLLs

9.3.5.19 Using `gnatdll'
........................

`gnatdll' is a tool to automate the DLL build process once all the Ada
and non-Ada sources that make up your DLL have been compiled.
`gnatdll' is actually in charge of two distinct tasks: build the static
import library for the DLL and the actual DLL. The form of the
`gnatdll' command is

         $ gnatdll [`switches`] `list-of-files` [-largs `opts`]

where `list-of-files' is a list of ALI and object files. The object
file list must be the exact list of objects corresponding to the non-Ada
sources whose services are to be included in the DLL. The ALI file list
must be the exact list of ALI files for the corresponding Ada sources
whose services are to be included in the DLL. If `list-of-files' is
missing, only the static import library is generated.

You may specify any of the following switches to `gnatdll':

 
`-a[`address']'
     Build a non-relocatable DLL at `address'. If `address' is not
     specified the default address `0x11000000' will be used. By
     default, when this switch is missing, `gnatdll' builds relocatable
     DLL. We advise the reader to build relocatable DLL.

`-b `address''
     Set the relocatable DLL base address. By default the address is
     `0x11000000'.

`-bargs `opts''
     Binder options. Pass `opts' to the binder.

`-d `dllfile''
     `dllfile' is the name of the DLL. This switch must be present for
     `gnatdll' to do anything. The name of the generated import library
     is obtained algorithmically from `dllfile' as shown in the
     following example: if `dllfile' is `xyz.dll', the import library
     name is `libxyz.dll.a'. The name of the definition file to use (if
     not specified by option `-e') is obtained algorithmically from
     `dllfile' as shown in the following example: if `dllfile' is
     `xyz.dll', the definition file used is `xyz.def'.

`-e `deffile''
     `deffile' is the name of the definition file.

`-g'
     Generate debugging information. This information is stored in the
     object file and copied from there to the final DLL file by the
     linker, where it can be read by the debugger. You must use the
     `-g' switch if you plan on using the debugger or the symbolic
     stack traceback.

`-h'
     Help mode. Displays `gnatdll' switch usage information.

`-I`dir''
     Direct `gnatdll' to search the `dir' directory for source and
     object files needed to build the DLL.  (*note Search Paths and the
     Run-Time Library (RTL): 8e.).

`-k'
     Removes the `@`nn'' suffix from the import library's exported
     names, but keeps them for the link names. You must specify this
     option if you want to use a `Stdcall' function in a DLL for which
     the `@`nn'' suffix has been removed. This is the case for most of
     the Windows NT DLL for example. This option has no effect when
     `-n' option is specified.

`-l `file''
     The list of ALI and object files used to build the DLL are listed
     in `file', instead of being given in the command line. Each line in
     `file' contains the name of an ALI or object file.

`-n'
     No Import. Do not create the import library.

`-q'
     Quiet mode. Do not display unnecessary messages.

`-v'
     Verbose mode. Display extra information.

`-largs `opts''
     Linker options. Pass `opts' to the linker.

`gnatdll' Example
.................

As an example the command to build a relocatable DLL from `api.adb'
once `api.adb' has been compiled and `api.def' created is

         $ gnatdll -d api.dll api.ali

The above command creates two files: `libapi.dll.a' (the import
library) and `api.dll' (the actual DLL). If you want to create only the
DLL, just type:

         $ gnatdll -d api.dll -n api.ali

Alternatively if you want to create just the import library, type:

         $ gnatdll -d api.dll

`gnatdll' behind the Scenes
...........................

This section details the steps involved in creating a DLL. `gnatdll'
does these steps for you. Unless you are interested in understanding
what goes on behind the scenes, you should skip this section.

We use the previous example of a DLL containing the Ada package `API',
to illustrate the steps necessary to build a DLL. The starting point is
a set of objects that will make up the DLL and the corresponding ALI
files. In the case of this example this means that `api.o' and
`api.ali' are available. To build a relocatable DLL, `gnatdll' does the
following:

   * `gnatdll' builds the base file (`api.base'). A base file gives the
     information necessary to generate relocation information for the
     DLL.

         $ gnatbind -n api
         $ gnatlink api -o api.jnk -mdll -Wl,--base-file,api.base

     In addition to the base file, the `gnatlink' command generates an
     output file `api.jnk' which can be discarded. The `-mdll' switch
     asks `gnatlink' to generate the routines `DllMain' and
     `DllMainCRTStartup' that are called by the Windows loader when the
     DLL is loaded into memory.

   * `gnatdll' uses `dlltool' (see *note Using dlltool: 29e.) to build
     the export table (`api.exp'). The export table contains the
     relocation information in a form which can be used during the
     final link to ensure that the Windows loader is able to place the
     DLL anywhere in memory.

         $ dlltool --dllname api.dll --def api.def --base-file api.base \\
                   --output-exp api.exp

   * `gnatdll' builds the base file using the new export table. Note
     that `gnatbind' must be called once again since the binder
     generated file has been deleted during the previous call to
     `gnatlink'.

         $ gnatbind -n api
         $ gnatlink api -o api.jnk api.exp -mdll
               -Wl,--base-file,api.base

   * `gnatdll' builds the new export table using the new base file and
     generates the DLL import library `libAPI.dll.a'.

         $ dlltool --dllname api.dll --def api.def --base-file api.base \\
                   --output-exp api.exp --output-lib libAPI.a

   * Finally `gnatdll' builds the relocatable DLL using the final export
     table.

         $ gnatbind -n api
         $ gnatlink api api.exp -o api.dll -mdll

Using `dlltool'
...............

`dlltool' is the low-level tool used by `gnatdll' to build DLLs and
static import libraries. This section summarizes the most common
`dlltool' switches. The form of the `dlltool' command is

         $ dlltool [`switches`]

`dlltool' switches include:

`--base-file `basefile''
     Read the base file `basefile' generated by the linker. This switch
     is used to create a relocatable DLL.

`--def `deffile''
     Read the definition file.

`--dllname `name''
     Gives the name of the DLL. This switch is used to embed the name
     of the DLL in the static import library generated by `dlltool'
     with switch `-output-lib'.

`-k'
     Kill `@`nn'' from exported names (*note Windows Calling
     Conventions: 277.  for a discussion about `Stdcall'-style symbols.

`--help'
     Prints the `dlltool' switches with a concise description.

`--output-exp `exportfile''
     Generate an export file `exportfile'. The export file contains the
     export table (list of symbols in the DLL) and is used to create
     the DLL.

`--output-lib `libfile''
     Generate a static import library `libfile'.

`-v'
     Verbose mode.

`--as `assembler-name''
     Use `assembler-name' as the assembler. The default is `as'.


File: gnat_ugn.info,  Node: GNAT and Windows Resources,  Next: Using GNAT DLLs from Microsoft Visual Studio Applications,  Prev: Creating a Spec for Ada DLLs,  Up: Mixed-Language Programming on Windows

9.3.5.20 GNAT and Windows Resources
...................................

Resources are an easy way to add Windows specific objects to your
application. The objects that can be added as resources include:

   * menus

   * accelerators

   * dialog boxes

   * string tables

   * bitmaps

   * cursors

   * icons

   * fonts

   * version information

For example, a version information resource can be defined as follow and
embedded into an executable or DLL:

A version information resource can be used to embed information into an
executable or a DLL. These information can be viewed using the file
properties from the Windows Explorer. Here is an example of a version
information resource:

         1 VERSIONINFO
         FILEVERSION     1,0,0,0
         PRODUCTVERSION  1,0,0,0
         BEGIN
           BLOCK "StringFileInfo"
           BEGIN
             BLOCK "080904E4"
             BEGIN
               VALUE "CompanyName", "My Company Name"
               VALUE "FileDescription", "My application"
               VALUE "FileVersion", "1.0"
               VALUE "InternalName", "my_app"
               VALUE "LegalCopyright", "My Name"
               VALUE "OriginalFilename", "my_app.exe"
               VALUE "ProductName", "My App"
               VALUE "ProductVersion", "1.0"
             END
           END

           BLOCK "VarFileInfo"
           BEGIN
             VALUE "Translation", 0x809, 1252
           END
         END

The value `0809' (langID) is for the U.K English language and `04E4'
(charsetID), which is equal to `1252' decimal, for multilingual.

This section explains how to build, compile and use resources. Note
that this section does not cover all resource objects, for a complete
description see the corresponding Microsoft documentation.

* Menu:

* Building Resources::
* Compiling Resources::
* Using Resources::


File: gnat_ugn.info,  Node: Building Resources,  Next: Compiling Resources,  Up: GNAT and Windows Resources

9.3.5.21 Building Resources
...........................

A resource file is an ASCII file. By convention resource files have an
`.rc' extension.  The easiest way to build a resource file is to use
Microsoft tools such as `imagedit.exe' to build bitmaps, icons and
cursors and `dlgedit.exe' to build dialogs.  It is always possible to
build an `.rc' file yourself by writing a resource script.

It is not our objective to explain how to write a resource file. A
complete description of the resource script language can be found in the
Microsoft documentation.


File: gnat_ugn.info,  Node: Compiling Resources,  Next: Using Resources,  Prev: Building Resources,  Up: GNAT and Windows Resources

9.3.5.22 Compiling Resources
............................

This section describes how to build a GNAT-compatible (COFF) object file
containing the resources. This is done using the Resource Compiler
`windres' as follows:

         $ windres -i myres.rc -o myres.o

By default `windres' will run `gcc' to preprocess the `.rc' file. You
can specify an alternate preprocessor (usually named `cpp.exe') using
the `windres' `-preprocessor' parameter. A list of all possible options
may be obtained by entering the command `windres' `-help'.

It is also possible to use the Microsoft resource compiler `rc.exe' to
produce a `.res' file (binary resource file). See the corresponding
Microsoft documentation for further details. In this case you need to
use `windres' to translate the `.res' file to a GNAT-compatible object
file as follows:

         $ windres -i myres.res -o myres.o


File: gnat_ugn.info,  Node: Using Resources,  Prev: Compiling Resources,  Up: GNAT and Windows Resources

9.3.5.23 Using Resources
........................

To include the resource file in your program just add the
GNAT-compatible object file for the resource(s) to the linker
arguments. With `gnatmake' this is done by using the `-largs' option:

         $ gnatmake myprog -largs myres.o


File: gnat_ugn.info,  Node: Using GNAT DLLs from Microsoft Visual Studio Applications,  Next: Debugging a DLL,  Prev: GNAT and Windows Resources,  Up: Mixed-Language Programming on Windows

9.3.5.24 Using GNAT DLLs from Microsoft Visual Studio Applications
..................................................................

This section describes a common case of mixed GNAT/Microsoft Visual
Studio application development, where the main program is developed
using MSVS, and is linked with a DLL developed using GNAT. Such a mixed
application should be developed following the general guidelines
outlined above; below is the cookbook-style sequence of steps to follow:

  1. First develop and build the GNAT shared library using a library
     project (let's assume the project is `mylib.gpr', producing the
     library `libmylib.dll'):

         $ gprbuild -p mylib.gpr

  2. Produce a .def file for the symbols you need to interface with,
     either by hand or automatically with possibly some manual
     adjustments (see *note Creating Definition File Automatically:
     289.):

         $ dlltool libmylib.dll -z libmylib.def --export-all-symbols

  3. Make sure that MSVS command-line tools are accessible on the path.

  4. Create the Microsoft-style import library (see *note MSVS-Style
     Import Library: 28c.):

         $ lib -machine:IX86 -def:libmylib.def -out:libmylib.lib

If you are using a 64-bit toolchain, the above becomes...

         $ lib -machine:X64 -def:libmylib.def -out:libmylib.lib

  5. Build the C main

         $ cl /O2 /MD main.c libmylib.lib

  6. Before running the executable, make sure you have set the PATH to
     the DLL, or copy the DLL into into the directory containing the
     .exe.


File: gnat_ugn.info,  Node: Debugging a DLL,  Next: Setting Stack Size from gnatlink,  Prev: Using GNAT DLLs from Microsoft Visual Studio Applications,  Up: Mixed-Language Programming on Windows

9.3.5.25 Debugging a DLL
........................

Debugging a DLL is similar to debugging a standard program. But we have
to deal with two different executable parts: the DLL and the program
that uses it. We have the following four possibilities:

   * The program and the DLL are built with `GCC/GNAT'.

   * The program is built with foreign tools and the DLL is built with
     `GCC/GNAT'.

   * The program is built with `GCC/GNAT' and the DLL is built with
     foreign tools.

In this section we address only cases one and two above.  There is no
point in trying to debug a DLL with `GNU/GDB', if there is no
GDB-compatible debugging information in it. To do so you must use a
debugger compatible with the tools suite used to build the DLL.

* Menu:

* Program and DLL Both Built with GCC/GNAT::
* Program Built with Foreign Tools and DLL Built with GCC/GNAT::


File: gnat_ugn.info,  Node: Program and DLL Both Built with GCC/GNAT,  Next: Program Built with Foreign Tools and DLL Built with GCC/GNAT,  Up: Debugging a DLL

9.3.5.26 Program and DLL Both Built with GCC/GNAT
.................................................

This is the simplest case. Both the DLL and the program have `GDB'
compatible debugging information. It is then possible to break anywhere
in the process. Let's suppose here that the main procedure is named
`ada_main' and that in the DLL there is an entry point named `ada_dll'.

The DLL (*note Introduction to Dynamic Link Libraries (DLLs): 282.) and
program must have been built with the debugging information (see GNAT -g
switch). Here are the step-by-step instructions for debugging it:

   * Launch `GDB' on the main program.

         $ gdb -nw ada_main

   * Start the program and stop at the beginning of the main procedure

         (gdb) start

     This step is required to be able to set a breakpoint inside the
     DLL. As long as the program is not run, the DLL is not loaded.
     This has the consequence that the DLL debugging information is
     also not loaded, so it is not possible to set a breakpoint in the
     DLL.

   * Set a breakpoint inside the DLL

         (gdb) break ada_dll
         (gdb) cont

At this stage a breakpoint is set inside the DLL. From there on you can
use the standard approach to debug the whole program (*note Running and
Debugging Ada Programs: 26.).


File: gnat_ugn.info,  Node: Program Built with Foreign Tools and DLL Built with GCC/GNAT,  Prev: Program and DLL Both Built with GCC/GNAT,  Up: Debugging a DLL

9.3.5.27 Program Built with Foreign Tools and DLL Built with GCC/GNAT
.....................................................................

In this case things are slightly more complex because it is not
possible to start the main program and then break at the beginning to
load the DLL and the associated DLL debugging information. It is not
possible to break at the beginning of the program because there is no
`GDB' debugging information, and therefore there is no direct way of
getting initial control. This section addresses this issue by
describing some methods that can be used to break somewhere in the DLL
to debug it.

First suppose that the main procedure is named `main' (this is for
example some C code built with Microsoft Visual C) and that there is a
DLL named `test.dll' containing an Ada entry point named `ada_dll'.

The DLL (see *note Introduction to Dynamic Link Libraries (DLLs): 282.)
must have been built with debugging information (see GNAT `-g' option).

Debugging the DLL Directly
..........................

   * Find out the executable starting address

         $ objdump --file-header main.exe

     The starting address is reported on the last line. For example:

         main.exe:     file format pei-i386
         architecture: i386, flags 0x0000010a:
         EXEC_P, HAS_DEBUG, D_PAGED
         start address 0x00401010

   * Launch the debugger on the executable.

         $ gdb main.exe

   * Set a breakpoint at the starting address, and launch the program.

         $ (gdb) break *0x00401010
         $ (gdb) run

     The program will stop at the given address.

   * Set a breakpoint on a DLL subroutine.

         (gdb) break ada_dll.adb:45

     Or if you want to break using a symbol on the DLL, you need first
     to select the Ada language (language used by the DLL).

         (gdb) set language ada
         (gdb) break ada_dll

   * Continue the program.

         (gdb) cont

     This will run the program until it reaches the breakpoint that has
     been set. From that point you can use the standard way to debug a
     program as described in (*note Running and Debugging Ada Programs:
     26.).

It is also possible to debug the DLL by attaching to a running process.

Attaching to a Running Process
..............................

With `GDB' it is always possible to debug a running process by
attaching to it. It is possible to debug a DLL this way. The limitation
of this approach is that the DLL must run long enough to perform the
attach operation. It may be useful for instance to insert a time wasting
loop in the code of the DLL to meet this criterion.

   * Launch the main program `main.exe'.

         $ main

   * Use the Windows `Task Manager' to find the process ID. Let's say
     that the process PID for `main.exe' is 208.

   * Launch gdb.

         $ gdb

   * Attach to the running process to be debugged.

         (gdb) attach 208

   * Load the process debugging information.

         (gdb) symbol-file main.exe

   * Break somewhere in the DLL.

         (gdb) break ada_dll

   * Continue process execution.

         (gdb) cont

This last step will resume the process execution, and stop at the
breakpoint we have set. From there you can use the standard approach to
debug a program as described in *note Running and Debugging Ada
Programs: 26.


File: gnat_ugn.info,  Node: Setting Stack Size from gnatlink,  Next: Setting Heap Size from gnatlink,  Prev: Debugging a DLL,  Up: Mixed-Language Programming on Windows

9.3.5.28 Setting Stack Size from `gnatlink'
...........................................

It is possible to specify the program stack size at link time. On modern
versions of Windows, starting with XP, this is mostly useful to set the
size of the main stack (environment task). The other task stacks are
set with pragma Storage_Size or with the `gnatbind -d' command.

Since older versions of Windows (2000, NT4, etc.) do not allow setting
the reserve size of individual tasks, the link-time stack size applies
to all tasks, and pragma Storage_Size has no effect.  In particular,
Stack Overflow checks are made against this link-time specified size.

This setting can be done with `gnatlink' using either of the following:

   * `-Xlinker' linker option

         $ gnatlink hello -Xlinker --stack=0x10000,0x1000

     This sets the stack reserve size to 0x10000 bytes and the stack
     commit size to 0x1000 bytes.

   * `-Wl' linker option

         $ gnatlink hello -Wl,--stack=0x1000000

     This sets the stack reserve size to 0x1000000 bytes. Note that with
     `-Wl' option it is not possible to set the stack commit size
     because the coma is a separator for this option.


File: gnat_ugn.info,  Node: Setting Heap Size from gnatlink,  Prev: Setting Stack Size from gnatlink,  Up: Mixed-Language Programming on Windows

9.3.5.29 Setting Heap Size from `gnatlink'
..........................................

Under Windows systems, it is possible to specify the program heap size
from `gnatlink' using either of the following:

   * `-Xlinker' linker option

         $ gnatlink hello -Xlinker --heap=0x10000,0x1000

     This sets the heap reserve size to 0x10000 bytes and the heap
     commit size to 0x1000 bytes.

   * `-Wl' linker option

         $ gnatlink hello -Wl,--heap=0x1000000

     This sets the heap reserve size to 0x1000000 bytes. Note that with
     `-Wl' option it is not possible to set the heap commit size
     because the coma is a separator for this option.


File: gnat_ugn.info,  Node: Windows Specific Add-Ons,  Prev: Mixed-Language Programming on Windows,  Up: Microsoft Windows Topics

9.3.6 Windows Specific Add-Ons
------------------------------

This section describes the Windows specific add-ons.

* Menu:

* Win32Ada::
* wPOSIX::


File: gnat_ugn.info,  Node: Win32Ada,  Next: wPOSIX,  Up: Windows Specific Add-Ons

9.3.6.1 Win32Ada
................

Win32Ada is a binding for the Microsoft Win32 API. This binding can be
easily installed from the provided installer. To use the Win32Ada
binding you need to use a project file, and adding a single with_clause
will give you full access to the Win32Ada binding sources and ensure
that the proper libraries are passed to the linker.

         with "win32ada";
         project P is
            for Sources use ...;
         end P;

To build the application you just need to call gprbuild for the
application's project, here p.gpr:

         gprbuild p.gpr


File: gnat_ugn.info,  Node: wPOSIX,  Prev: Win32Ada,  Up: Windows Specific Add-Ons

9.3.6.2 wPOSIX
..............

wPOSIX is a minimal POSIX binding whose goal is to help with building
cross-platforms applications. This binding is not complete though, as
the Win32 API does not provide the necessary support for all POSIX APIs.

To use the wPOSIX binding you need to use a project file, and adding a
single with_clause will give you full access to the wPOSIX binding
sources and ensure that the proper libraries are passed to the linker.

         with "wposix";
         project P is
            for Sources use ...;
         end P;

To build the application you just need to call gprbuild for the
application's project, here p.gpr:

         gprbuild p.gpr


File: gnat_ugn.info,  Node: Mac OS Topics,  Prev: Microsoft Windows Topics,  Up: Platform-Specific Information

9.4 Mac OS Topics
=================

This section describes topics that are specific to Apple's OS X
platform.

* Menu:

* Codesigning the Debugger::


File: gnat_ugn.info,  Node: Codesigning the Debugger,  Up: Mac OS Topics

9.4.1 Codesigning the Debugger
------------------------------

The Darwin Kernel requires the debugger to have special permissions
before it is allowed to control other processes. These permissions are
granted by codesigning the GDB executable. Without these permissions,
the debugger will report error messages such as:

    Starting program: /x/y/foo
    Unable to find Mach task port for process-id 28885: (os/kern) failure (0x5).
    (please check gdb is codesigned - see taskgated(8))

Codesigning requires a certificate.  The following procedure explains
how to create one:

   * Start the Keychain Access application (in
     /Applications/Utilities/Keychain Access.app)

   * Select the Keychain Access -> Certificate Assistant -> Create a
     Certificate... menu

   * Then:

        * Choose a name for the new certificate (this procedure will use
          "gdb-cert" as an example)

        * Set "Identity Type" to "Self Signed Root"

        * Set "Certificate Type" to "Code Signing"

        * Activate the "Let me override defaults" option

   * Click several times on "Continue" until the "Specify a Location
     For The Certificate" screen appears, then set "Keychain" to
     "System"

   * Click on "Continue" until the certificate is created

   * Finally, in the view, double-click on the new certificate, and set
     "When using this certificate" to "Always Trust"

   * Exit the Keychain Access application and restart the computer
     (this is unfortunately required)

Once a certificate has been created, the debugger can be codesigned as
follow. In a Terminal, run the following command:

         $ codesign -f -s  "gdb-cert"  <gnat_install_prefix>/bin/gdb

where "gdb-cert" should be replaced by the actual certificate name
chosen above, and <gnat_install_prefix> should be replaced by the
location where you installed GNAT.  Also, be sure that users are in the
Unix group `_developer'.


File: gnat_ugn.info,  Node: Example of Binder Output File,  Next: Elaboration Order Handling in GNAT,  Prev: Platform-Specific Information,  Up: Top

10 Example of Binder Output File
********************************

This Appendix displays the source code for the output file generated by
`gnatbind' for a simple 'Hello World' program.  Comments have been
added for clarification purposes.

    --  The package is called Ada_Main unless this name is actually used
    --  as a unit name in the partition, in which case some other unique
    --  name is used.

    pragma Ada_95;
    with System;
    package ada_main is
       pragma Warnings (Off);

       --  The main program saves the parameters (argument count,
       --  argument values, environment pointer) in global variables
       --  for later access by other units including
       --  Ada.Command_Line.

       gnat_argc : Integer;
       gnat_argv : System.Address;
       gnat_envp : System.Address;

       --  The actual variables are stored in a library routine. This
       --  is useful for some shared library situations, where there
       --  are problems if variables are not in the library.

       pragma Import (C, gnat_argc);
       pragma Import (C, gnat_argv);
       pragma Import (C, gnat_envp);

       --  The exit status is similarly an external location

       gnat_exit_status : Integer;
       pragma Import (C, gnat_exit_status);

       GNAT_Version : constant String :=
                        "GNAT Version: Pro 7.4.0w (20141119-49)" & ASCII.NUL;
       pragma Export (C, GNAT_Version, "__gnat_version");

       Ada_Main_Program_Name : constant String := "_ada_hello" & ASCII.NUL;
       pragma Export (C, Ada_Main_Program_Name, "__gnat_ada_main_program_name");

       --  This is the generated adainit routine that performs
       --  initialization at the start of execution. In the case
       --  where Ada is the main program, this main program makes
       --  a call to adainit at program startup.

       procedure adainit;
       pragma Export (C, adainit, "adainit");

       --  This is the generated adafinal routine that performs
       --  finalization at the end of execution. In the case where
       --  Ada is the main program, this main program makes a call
       --  to adafinal at program termination.

       procedure adafinal;
       pragma Export (C, adafinal, "adafinal");

       --  This routine is called at the start of execution. It is
       --  a dummy routine that is used by the debugger to breakpoint
       --  at the start of execution.

       --  This is the actual generated main program (it would be
       --  suppressed if the no main program switch were used). As
       --  required by standard system conventions, this program has
       --  the external name main.

       function main
         (argc : Integer;
          argv : System.Address;
          envp : System.Address)
          return Integer;
       pragma Export (C, main, "main");

       --  The following set of constants give the version
       --  identification values for every unit in the bound
       --  partition. This identification is computed from all
       --  dependent semantic units, and corresponds to the
       --  string that would be returned by use of the
       --  Body_Version or Version attributes.

       --  The following Export pragmas export the version numbers
       --  with symbolic names ending in B (for body) or S
       --  (for spec) so that they can be located in a link. The
       --  information provided here is sufficient to track down
       --  the exact versions of units used in a given build.

       type Version_32 is mod 2 ** 32;
       u00001 : constant Version_32 := 16#8ad6e54a#;
       pragma Export (C, u00001, "helloB");
       u00002 : constant Version_32 := 16#fbff4c67#;
       pragma Export (C, u00002, "system__standard_libraryB");
       u00003 : constant Version_32 := 16#1ec6fd90#;
       pragma Export (C, u00003, "system__standard_libraryS");
       u00004 : constant Version_32 := 16#3ffc8e18#;
       pragma Export (C, u00004, "adaS");
       u00005 : constant Version_32 := 16#28f088c2#;
       pragma Export (C, u00005, "ada__text_ioB");
       u00006 : constant Version_32 := 16#f372c8ac#;
       pragma Export (C, u00006, "ada__text_ioS");
       u00007 : constant Version_32 := 16#2c143749#;
       pragma Export (C, u00007, "ada__exceptionsB");
       u00008 : constant Version_32 := 16#f4f0cce8#;
       pragma Export (C, u00008, "ada__exceptionsS");
       u00009 : constant Version_32 := 16#a46739c0#;
       pragma Export (C, u00009, "ada__exceptions__last_chance_handlerB");
       u00010 : constant Version_32 := 16#3aac8c92#;
       pragma Export (C, u00010, "ada__exceptions__last_chance_handlerS");
       u00011 : constant Version_32 := 16#1d274481#;
       pragma Export (C, u00011, "systemS");
       u00012 : constant Version_32 := 16#a207fefe#;
       pragma Export (C, u00012, "system__soft_linksB");
       u00013 : constant Version_32 := 16#467d9556#;
       pragma Export (C, u00013, "system__soft_linksS");
       u00014 : constant Version_32 := 16#b01dad17#;
       pragma Export (C, u00014, "system__parametersB");
       u00015 : constant Version_32 := 16#630d49fe#;
       pragma Export (C, u00015, "system__parametersS");
       u00016 : constant Version_32 := 16#b19b6653#;
       pragma Export (C, u00016, "system__secondary_stackB");
       u00017 : constant Version_32 := 16#b6468be8#;
       pragma Export (C, u00017, "system__secondary_stackS");
       u00018 : constant Version_32 := 16#39a03df9#;
       pragma Export (C, u00018, "system__storage_elementsB");
       u00019 : constant Version_32 := 16#30e40e85#;
       pragma Export (C, u00019, "system__storage_elementsS");
       u00020 : constant Version_32 := 16#41837d1e#;
       pragma Export (C, u00020, "system__stack_checkingB");
       u00021 : constant Version_32 := 16#93982f69#;
       pragma Export (C, u00021, "system__stack_checkingS");
       u00022 : constant Version_32 := 16#393398c1#;
       pragma Export (C, u00022, "system__exception_tableB");
       u00023 : constant Version_32 := 16#b33e2294#;
       pragma Export (C, u00023, "system__exception_tableS");
       u00024 : constant Version_32 := 16#ce4af020#;
       pragma Export (C, u00024, "system__exceptionsB");
       u00025 : constant Version_32 := 16#75442977#;
       pragma Export (C, u00025, "system__exceptionsS");
       u00026 : constant Version_32 := 16#37d758f1#;
       pragma Export (C, u00026, "system__exceptions__machineS");
       u00027 : constant Version_32 := 16#b895431d#;
       pragma Export (C, u00027, "system__exceptions_debugB");
       u00028 : constant Version_32 := 16#aec55d3f#;
       pragma Export (C, u00028, "system__exceptions_debugS");
       u00029 : constant Version_32 := 16#570325c8#;
       pragma Export (C, u00029, "system__img_intB");
       u00030 : constant Version_32 := 16#1ffca443#;
       pragma Export (C, u00030, "system__img_intS");
       u00031 : constant Version_32 := 16#b98c3e16#;
       pragma Export (C, u00031, "system__tracebackB");
       u00032 : constant Version_32 := 16#831a9d5a#;
       pragma Export (C, u00032, "system__tracebackS");
       u00033 : constant Version_32 := 16#9ed49525#;
       pragma Export (C, u00033, "system__traceback_entriesB");
       u00034 : constant Version_32 := 16#1d7cb2f1#;
       pragma Export (C, u00034, "system__traceback_entriesS");
       u00035 : constant Version_32 := 16#8c33a517#;
       pragma Export (C, u00035, "system__wch_conB");
       u00036 : constant Version_32 := 16#065a6653#;
       pragma Export (C, u00036, "system__wch_conS");
       u00037 : constant Version_32 := 16#9721e840#;
       pragma Export (C, u00037, "system__wch_stwB");
       u00038 : constant Version_32 := 16#2b4b4a52#;
       pragma Export (C, u00038, "system__wch_stwS");
       u00039 : constant Version_32 := 16#92b797cb#;
       pragma Export (C, u00039, "system__wch_cnvB");
       u00040 : constant Version_32 := 16#09eddca0#;
       pragma Export (C, u00040, "system__wch_cnvS");
       u00041 : constant Version_32 := 16#6033a23f#;
       pragma Export (C, u00041, "interfacesS");
       u00042 : constant Version_32 := 16#ece6fdb6#;
       pragma Export (C, u00042, "system__wch_jisB");
       u00043 : constant Version_32 := 16#899dc581#;
       pragma Export (C, u00043, "system__wch_jisS");
       u00044 : constant Version_32 := 16#10558b11#;
       pragma Export (C, u00044, "ada__streamsB");
       u00045 : constant Version_32 := 16#2e6701ab#;
       pragma Export (C, u00045, "ada__streamsS");
       u00046 : constant Version_32 := 16#db5c917c#;
       pragma Export (C, u00046, "ada__io_exceptionsS");
       u00047 : constant Version_32 := 16#12c8cd7d#;
       pragma Export (C, u00047, "ada__tagsB");
       u00048 : constant Version_32 := 16#ce72c228#;
       pragma Export (C, u00048, "ada__tagsS");
       u00049 : constant Version_32 := 16#c3335bfd#;
       pragma Export (C, u00049, "system__htableB");
       u00050 : constant Version_32 := 16#99e5f76b#;
       pragma Export (C, u00050, "system__htableS");
       u00051 : constant Version_32 := 16#089f5cd0#;
       pragma Export (C, u00051, "system__string_hashB");
       u00052 : constant Version_32 := 16#3bbb9c15#;
       pragma Export (C, u00052, "system__string_hashS");
       u00053 : constant Version_32 := 16#807fe041#;
       pragma Export (C, u00053, "system__unsigned_typesS");
       u00054 : constant Version_32 := 16#d27be59e#;
       pragma Export (C, u00054, "system__val_lluB");
       u00055 : constant Version_32 := 16#fa8db733#;
       pragma Export (C, u00055, "system__val_lluS");
       u00056 : constant Version_32 := 16#27b600b2#;
       pragma Export (C, u00056, "system__val_utilB");
       u00057 : constant Version_32 := 16#b187f27f#;
       pragma Export (C, u00057, "system__val_utilS");
       u00058 : constant Version_32 := 16#d1060688#;
       pragma Export (C, u00058, "system__case_utilB");
       u00059 : constant Version_32 := 16#392e2d56#;
       pragma Export (C, u00059, "system__case_utilS");
       u00060 : constant Version_32 := 16#84a27f0d#;
       pragma Export (C, u00060, "interfaces__c_streamsB");
       u00061 : constant Version_32 := 16#8bb5f2c0#;
       pragma Export (C, u00061, "interfaces__c_streamsS");
       u00062 : constant Version_32 := 16#6db6928f#;
       pragma Export (C, u00062, "system__crtlS");
       u00063 : constant Version_32 := 16#4e6a342b#;
       pragma Export (C, u00063, "system__file_ioB");
       u00064 : constant Version_32 := 16#ba56a5e4#;
       pragma Export (C, u00064, "system__file_ioS");
       u00065 : constant Version_32 := 16#b7ab275c#;
       pragma Export (C, u00065, "ada__finalizationB");
       u00066 : constant Version_32 := 16#19f764ca#;
       pragma Export (C, u00066, "ada__finalizationS");
       u00067 : constant Version_32 := 16#95817ed8#;
       pragma Export (C, u00067, "system__finalization_rootB");
       u00068 : constant Version_32 := 16#52d53711#;
       pragma Export (C, u00068, "system__finalization_rootS");
       u00069 : constant Version_32 := 16#769e25e6#;
       pragma Export (C, u00069, "interfaces__cB");
       u00070 : constant Version_32 := 16#4a38bedb#;
       pragma Export (C, u00070, "interfaces__cS");
       u00071 : constant Version_32 := 16#07e6ee66#;
       pragma Export (C, u00071, "system__os_libB");
       u00072 : constant Version_32 := 16#d7b69782#;
       pragma Export (C, u00072, "system__os_libS");
       u00073 : constant Version_32 := 16#1a817b8e#;
       pragma Export (C, u00073, "system__stringsB");
       u00074 : constant Version_32 := 16#639855e7#;
       pragma Export (C, u00074, "system__stringsS");
       u00075 : constant Version_32 := 16#e0b8de29#;
       pragma Export (C, u00075, "system__file_control_blockS");
       u00076 : constant Version_32 := 16#b5b2aca1#;
       pragma Export (C, u00076, "system__finalization_mastersB");
       u00077 : constant Version_32 := 16#69316dc1#;
       pragma Export (C, u00077, "system__finalization_mastersS");
       u00078 : constant Version_32 := 16#57a37a42#;
       pragma Export (C, u00078, "system__address_imageB");
       u00079 : constant Version_32 := 16#bccbd9bb#;
       pragma Export (C, u00079, "system__address_imageS");
       u00080 : constant Version_32 := 16#7268f812#;
       pragma Export (C, u00080, "system__img_boolB");
       u00081 : constant Version_32 := 16#e8fe356a#;
       pragma Export (C, u00081, "system__img_boolS");
       u00082 : constant Version_32 := 16#d7aac20c#;
       pragma Export (C, u00082, "system__ioB");
       u00083 : constant Version_32 := 16#8365b3ce#;
       pragma Export (C, u00083, "system__ioS");
       u00084 : constant Version_32 := 16#6d4d969a#;
       pragma Export (C, u00084, "system__storage_poolsB");
       u00085 : constant Version_32 := 16#e87cc305#;
       pragma Export (C, u00085, "system__storage_poolsS");
       u00086 : constant Version_32 := 16#e34550ca#;
       pragma Export (C, u00086, "system__pool_globalB");
       u00087 : constant Version_32 := 16#c88d2d16#;
       pragma Export (C, u00087, "system__pool_globalS");
       u00088 : constant Version_32 := 16#9d39c675#;
       pragma Export (C, u00088, "system__memoryB");
       u00089 : constant Version_32 := 16#445a22b5#;
       pragma Export (C, u00089, "system__memoryS");
       u00090 : constant Version_32 := 16#6a859064#;
       pragma Export (C, u00090, "system__storage_pools__subpoolsB");
       u00091 : constant Version_32 := 16#e3b008dc#;
       pragma Export (C, u00091, "system__storage_pools__subpoolsS");
       u00092 : constant Version_32 := 16#63f11652#;
       pragma Export (C, u00092, "system__storage_pools__subpools__finalizationB");
       u00093 : constant Version_32 := 16#fe2f4b3a#;
       pragma Export (C, u00093, "system__storage_pools__subpools__finalizationS");

       --  BEGIN ELABORATION ORDER
       --  ada%s
       --  interfaces%s
       --  system%s
       --  system.case_util%s
       --  system.case_util%b
       --  system.htable%s
       --  system.img_bool%s
       --  system.img_bool%b
       --  system.img_int%s
       --  system.img_int%b
       --  system.io%s
       --  system.io%b
       --  system.parameters%s
       --  system.parameters%b
       --  system.crtl%s
       --  interfaces.c_streams%s
       --  interfaces.c_streams%b
       --  system.standard_library%s
       --  system.exceptions_debug%s
       --  system.exceptions_debug%b
       --  system.storage_elements%s
       --  system.storage_elements%b
       --  system.stack_checking%s
       --  system.stack_checking%b
       --  system.string_hash%s
       --  system.string_hash%b
       --  system.htable%b
       --  system.strings%s
       --  system.strings%b
       --  system.os_lib%s
       --  system.traceback_entries%s
       --  system.traceback_entries%b
       --  ada.exceptions%s
       --  system.soft_links%s
       --  system.unsigned_types%s
       --  system.val_llu%s
       --  system.val_util%s
       --  system.val_util%b
       --  system.val_llu%b
       --  system.wch_con%s
       --  system.wch_con%b
       --  system.wch_cnv%s
       --  system.wch_jis%s
       --  system.wch_jis%b
       --  system.wch_cnv%b
       --  system.wch_stw%s
       --  system.wch_stw%b
       --  ada.exceptions.last_chance_handler%s
       --  ada.exceptions.last_chance_handler%b
       --  system.address_image%s
       --  system.exception_table%s
       --  system.exception_table%b
       --  ada.io_exceptions%s
       --  ada.tags%s
       --  ada.streams%s
       --  ada.streams%b
       --  interfaces.c%s
       --  system.exceptions%s
       --  system.exceptions%b
       --  system.exceptions.machine%s
       --  system.finalization_root%s
       --  system.finalization_root%b
       --  ada.finalization%s
       --  ada.finalization%b
       --  system.storage_pools%s
       --  system.storage_pools%b
       --  system.finalization_masters%s
       --  system.storage_pools.subpools%s
       --  system.storage_pools.subpools.finalization%s
       --  system.storage_pools.subpools.finalization%b
       --  system.memory%s
       --  system.memory%b
       --  system.standard_library%b
       --  system.pool_global%s
       --  system.pool_global%b
       --  system.file_control_block%s
       --  system.file_io%s
       --  system.secondary_stack%s
       --  system.file_io%b
       --  system.storage_pools.subpools%b
       --  system.finalization_masters%b
       --  interfaces.c%b
       --  ada.tags%b
       --  system.soft_links%b
       --  system.os_lib%b
       --  system.secondary_stack%b
       --  system.address_image%b
       --  system.traceback%s
       --  ada.exceptions%b
       --  system.traceback%b
       --  ada.text_io%s
       --  ada.text_io%b
       --  hello%b
       --  END ELABORATION ORDER

    end ada_main;

    pragma Ada_95;
    --  The following source file name pragmas allow the generated file
    --  names to be unique for different main programs. They are needed
    --  since the package name will always be Ada_Main.

    pragma Source_File_Name (ada_main, Spec_File_Name => "b~hello.ads");
    pragma Source_File_Name (ada_main, Body_File_Name => "b~hello.adb");

    pragma Suppress (Overflow_Check);
    with Ada.Exceptions;

    --  Generated package body for Ada_Main starts here

    package body ada_main is
       pragma Warnings (Off);

       --  These values are reference counter associated to units which have
       --  been elaborated. It is also used to avoid elaborating the
       --  same unit twice.

       E72 : Short_Integer; pragma Import (Ada, E72, "system__os_lib_E");
       E13 : Short_Integer; pragma Import (Ada, E13, "system__soft_links_E");
       E23 : Short_Integer; pragma Import (Ada, E23, "system__exception_table_E");
       E46 : Short_Integer; pragma Import (Ada, E46, "ada__io_exceptions_E");
       E48 : Short_Integer; pragma Import (Ada, E48, "ada__tags_E");
       E45 : Short_Integer; pragma Import (Ada, E45, "ada__streams_E");
       E70 : Short_Integer; pragma Import (Ada, E70, "interfaces__c_E");
       E25 : Short_Integer; pragma Import (Ada, E25, "system__exceptions_E");
       E68 : Short_Integer; pragma Import (Ada, E68, "system__finalization_root_E");
       E66 : Short_Integer; pragma Import (Ada, E66, "ada__finalization_E");
       E85 : Short_Integer; pragma Import (Ada, E85, "system__storage_pools_E");
       E77 : Short_Integer; pragma Import (Ada, E77, "system__finalization_masters_E");
       E91 : Short_Integer; pragma Import (Ada, E91, "system__storage_pools__subpools_E");
       E87 : Short_Integer; pragma Import (Ada, E87, "system__pool_global_E");
       E75 : Short_Integer; pragma Import (Ada, E75, "system__file_control_block_E");
       E64 : Short_Integer; pragma Import (Ada, E64, "system__file_io_E");
       E17 : Short_Integer; pragma Import (Ada, E17, "system__secondary_stack_E");
       E06 : Short_Integer; pragma Import (Ada, E06, "ada__text_io_E");

       Local_Priority_Specific_Dispatching : constant String := "";
       Local_Interrupt_States : constant String := "";

       Is_Elaborated : Boolean := False;

       procedure finalize_library is
       begin
          E06 := E06 - 1;
          declare
             procedure F1;
             pragma Import (Ada, F1, "ada__text_io__finalize_spec");
          begin
             F1;
          end;
          E77 := E77 - 1;
          E91 := E91 - 1;
          declare
             procedure F2;
             pragma Import (Ada, F2, "system__file_io__finalize_body");
          begin
             E64 := E64 - 1;
             F2;
          end;
          declare
             procedure F3;
             pragma Import (Ada, F3, "system__file_control_block__finalize_spec");
          begin
             E75 := E75 - 1;
             F3;
          end;
          E87 := E87 - 1;
          declare
             procedure F4;
             pragma Import (Ada, F4, "system__pool_global__finalize_spec");
          begin
             F4;
          end;
          declare
             procedure F5;
             pragma Import (Ada, F5, "system__storage_pools__subpools__finalize_spec");
          begin
             F5;
          end;
          declare
             procedure F6;
             pragma Import (Ada, F6, "system__finalization_masters__finalize_spec");
          begin
             F6;
          end;
          declare
             procedure Reraise_Library_Exception_If_Any;
             pragma Import (Ada, Reraise_Library_Exception_If_Any, "__gnat_reraise_library_exception_if_any");
          begin
             Reraise_Library_Exception_If_Any;
          end;
       end finalize_library;

       -------------
       -- adainit --
       -------------

       procedure adainit is

          Main_Priority : Integer;
          pragma Import (C, Main_Priority, "__gl_main_priority");
          Time_Slice_Value : Integer;
          pragma Import (C, Time_Slice_Value, "__gl_time_slice_val");
          WC_Encoding : Character;
          pragma Import (C, WC_Encoding, "__gl_wc_encoding");
          Locking_Policy : Character;
          pragma Import (C, Locking_Policy, "__gl_locking_policy");
          Queuing_Policy : Character;
          pragma Import (C, Queuing_Policy, "__gl_queuing_policy");
          Task_Dispatching_Policy : Character;
          pragma Import (C, Task_Dispatching_Policy, "__gl_task_dispatching_policy");
          Priority_Specific_Dispatching : System.Address;
          pragma Import (C, Priority_Specific_Dispatching, "__gl_priority_specific_dispatching");
          Num_Specific_Dispatching : Integer;
          pragma Import (C, Num_Specific_Dispatching, "__gl_num_specific_dispatching");
          Main_CPU : Integer;
          pragma Import (C, Main_CPU, "__gl_main_cpu");
          Interrupt_States : System.Address;
          pragma Import (C, Interrupt_States, "__gl_interrupt_states");
          Num_Interrupt_States : Integer;
          pragma Import (C, Num_Interrupt_States, "__gl_num_interrupt_states");
          Unreserve_All_Interrupts : Integer;
          pragma Import (C, Unreserve_All_Interrupts, "__gl_unreserve_all_interrupts");
          Detect_Blocking : Integer;
          pragma Import (C, Detect_Blocking, "__gl_detect_blocking");
          Default_Stack_Size : Integer;
          pragma Import (C, Default_Stack_Size, "__gl_default_stack_size");
          Leap_Seconds_Support : Integer;
          pragma Import (C, Leap_Seconds_Support, "__gl_leap_seconds_support");

          procedure Runtime_Initialize;
          pragma Import (C, Runtime_Initialize, "__gnat_runtime_initialize");

          Finalize_Library_Objects : No_Param_Proc;
          pragma Import (C, Finalize_Library_Objects, "__gnat_finalize_library_objects");

       --  Start of processing for adainit

       begin

          --  Record various information for this partition.  The values
          --  are derived by the binder from information stored in the ali
          --  files by the compiler.

          if Is_Elaborated then
             return;
          end if;
          Is_Elaborated := True;
          Main_Priority := -1;
          Time_Slice_Value := -1;
          WC_Encoding := 'b';
          Locking_Policy := ' ';
          Queuing_Policy := ' ';
          Task_Dispatching_Policy := ' ';
          Priority_Specific_Dispatching :=
            Local_Priority_Specific_Dispatching'Address;
          Num_Specific_Dispatching := 0;
          Main_CPU := -1;
          Interrupt_States := Local_Interrupt_States'Address;
          Num_Interrupt_States := 0;
          Unreserve_All_Interrupts := 0;
          Detect_Blocking := 0;
          Default_Stack_Size := -1;
          Leap_Seconds_Support := 0;

          Runtime_Initialize;

          Finalize_Library_Objects := finalize_library'access;

          --  Now we have the elaboration calls for all units in the partition.
          --  The Elab_Spec and Elab_Body attributes generate references to the
          --  implicit elaboration procedures generated by the compiler for
          --  each unit that requires elaboration. Increment a counter of
          --  reference for each unit.

          System.Soft_Links'Elab_Spec;
          System.Exception_Table'Elab_Body;
          E23 := E23 + 1;
          Ada.Io_Exceptions'Elab_Spec;
          E46 := E46 + 1;
          Ada.Tags'Elab_Spec;
          Ada.Streams'Elab_Spec;
          E45 := E45 + 1;
          Interfaces.C'Elab_Spec;
          System.Exceptions'Elab_Spec;
          E25 := E25 + 1;
          System.Finalization_Root'Elab_Spec;
          E68 := E68 + 1;
          Ada.Finalization'Elab_Spec;
          E66 := E66 + 1;
          System.Storage_Pools'Elab_Spec;
          E85 := E85 + 1;
          System.Finalization_Masters'Elab_Spec;
          System.Storage_Pools.Subpools'Elab_Spec;
          System.Pool_Global'Elab_Spec;
          E87 := E87 + 1;
          System.File_Control_Block'Elab_Spec;
          E75 := E75 + 1;
          System.File_Io'Elab_Body;
          E64 := E64 + 1;
          E91 := E91 + 1;
          System.Finalization_Masters'Elab_Body;
          E77 := E77 + 1;
          E70 := E70 + 1;
          Ada.Tags'Elab_Body;
          E48 := E48 + 1;
          System.Soft_Links'Elab_Body;
          E13 := E13 + 1;
          System.Os_Lib'Elab_Body;
          E72 := E72 + 1;
          System.Secondary_Stack'Elab_Body;
          E17 := E17 + 1;
          Ada.Text_Io'Elab_Spec;
          Ada.Text_Io'Elab_Body;
          E06 := E06 + 1;
       end adainit;

       --------------
       -- adafinal --
       --------------

       procedure adafinal is
          procedure s_stalib_adafinal;
          pragma Import (C, s_stalib_adafinal, "system__standard_library__adafinal");

          procedure Runtime_Finalize;
          pragma Import (C, Runtime_Finalize, "__gnat_runtime_finalize");

       begin
          if not Is_Elaborated then
             return;
          end if;
          Is_Elaborated := False;
          Runtime_Finalize;
          s_stalib_adafinal;
       end adafinal;

       --  We get to the main program of the partition by using
       --  pragma Import because if we try to with the unit and
       --  call it Ada style, then not only do we waste time
       --  recompiling it, but also, we don't really know the right
       --  switches (e.g.@: identifier character set) to be used
       --  to compile it.

       procedure Ada_Main_Program;
       pragma Import (Ada, Ada_Main_Program, "_ada_hello");

       ----------
       -- main --
       ----------

       --  main is actually a function, as in the ANSI C standard,
       --  defined to return the exit status. The three parameters
       --  are the argument count, argument values and environment
       --  pointer.

       function main
         (argc : Integer;
          argv : System.Address;
          envp : System.Address)
          return Integer
       is
          --  The initialize routine performs low level system
          --  initialization using a standard library routine which
          --  sets up signal handling and performs any other
          --  required setup. The routine can be found in file
          --  a-init.c.

          procedure initialize;
          pragma Import (C, initialize, "__gnat_initialize");

          --  The finalize routine performs low level system
          --  finalization using a standard library routine. The
          --  routine is found in file a-final.c and in the standard
          --  distribution is a dummy routine that does nothing, so
          --  really this is a hook for special user finalization.

          procedure finalize;
          pragma Import (C, finalize, "__gnat_finalize");

          --  The following is to initialize the SEH exceptions

          SEH : aliased array (1 .. 2) of Integer;

          Ensure_Reference : aliased System.Address := Ada_Main_Program_Name'Address;
          pragma Volatile (Ensure_Reference);

       --  Start of processing for main

       begin
          --  Save global variables

          gnat_argc := argc;
          gnat_argv := argv;
          gnat_envp := envp;

          --  Call low level system initialization

          Initialize (SEH'Address);

          --  Call our generated Ada initialization routine

          adainit;

          --  Now we call the main program of the partition

          Ada_Main_Program;

          --  Perform Ada finalization

          adafinal;

          --  Perform low level system finalization

          Finalize;

          --  Return the proper exit status
          return (gnat_exit_status);
       end;

    --  This section is entirely comments, so it has no effect on the
    --  compilation of the Ada_Main package. It provides the list of
    --  object files and linker options, as well as some standard
    --  libraries needed for the link. The gnatlink utility parses
    --  this b~hello.adb file to read these comment lines to generate
    --  the appropriate command line arguments for the call to the
    --  system linker. The BEGIN/END lines are used for sentinels for
    --  this parsing operation.

    --  The exact file names will of course depend on the environment,
    --  host/target and location of files on the host system.

    -- BEGIN Object file/option list
       --   ./hello.o
       --   -L./
       --   -L/usr/local/gnat/lib/gcc-lib/i686-pc-linux-gnu/2.8.1/adalib/
       --   /usr/local/gnat/lib/gcc-lib/i686-pc-linux-gnu/2.8.1/adalib/libgnat.a
    -- END Object file/option list

    end ada_main;

The Ada code in the above example is exactly what is generated by the
binder. We have added comments to more clearly indicate the function of
each part of the generated `Ada_Main' package.

The code is standard Ada in all respects, and can be processed by any
tools that handle Ada. In particular, it is possible to use the debugger
in Ada mode to debug the generated `Ada_Main' package. For example,
suppose that for reasons that you do not understand, your program is
crashing during elaboration of the body of `Ada.Text_IO'. To locate
this bug, you can place a breakpoint on the call:

         Ada.Text_Io'Elab_Body;

and trace the elaboration routine for this package to find out where
the problem might be (more usually of course you would be debugging
elaboration code in your own application).


File: gnat_ugn.info,  Node: Elaboration Order Handling in GNAT,  Next: Inline Assembler,  Prev: Example of Binder Output File,  Up: Top

11 Elaboration Order Handling in GNAT
*************************************

This appendix describes the handling of elaboration code in Ada and in
GNAT, and discusses how the order of elaboration of program units can
be controlled in GNAT, either automatically or with explicit programming
features.

* Menu:

* Elaboration Code::
* Checking the Elaboration Order::
* Controlling the Elaboration Order::
* Controlling Elaboration in GNAT - Internal Calls::
* Controlling Elaboration in GNAT - External Calls::
* Default Behavior in GNAT - Ensuring Safety::
* Treatment of Pragma Elaborate::
* Elaboration Issues for Library Tasks::
* Mixing Elaboration Models::
* What to Do If the Default Elaboration Behavior Fails::
* Elaboration for Indirect Calls::
* Summary of Procedures for Elaboration Control::
* Other Elaboration Order Considerations::
* Determining the Chosen Elaboration Order::


File: gnat_ugn.info,  Node: Elaboration Code,  Next: Checking the Elaboration Order,  Up: Elaboration Order Handling in GNAT

11.1 Elaboration Code
=====================

Ada provides rather general mechanisms for executing code at elaboration
time, that is to say before the main program starts executing. Such
code arises in three contexts:

   * `Initializers for variables'

     Variables declared at the library level, in package specs or
     bodies, can require initialization that is performed at
     elaboration time, as in:

         Sqrt_Half : Float := Sqrt (0.5);

   * `Package initialization code'

     Code in a `BEGIN-END' section at the outer level of a package body
     is executed as part of the package body elaboration code.

   * `Library level task allocators'

     Tasks that are declared using task allocators at the library level
     start executing immediately and hence can execute at elaboration
     time.

Subprogram calls are possible in any of these contexts, which means that
any arbitrary part of the program may be executed as part of the
elaboration code. It is even possible to write a program which does all
its work at elaboration time, with a null main program, although
stylistically this would usually be considered an inappropriate way to
structure a program.

An important concern arises in the context of elaboration code: we have
to be sure that it is executed in an appropriate order. What we have is
a series of elaboration code sections, potentially one section for each
unit in the program. It is important that these execute in the correct
order. Correctness here means that, taking the above example of the
declaration of `Sqrt_Half', if some other piece of elaboration code
references `Sqrt_Half', then it must run after the section of
elaboration code that contains the declaration of `Sqrt_Half'.

There would never be any order of elaboration problem if we made a rule
that whenever you `with' a unit, you must elaborate both the spec and
body of that unit before elaborating the unit doing the `with'ing:

    with Unit_1;
    package Unit_2 is ...

would require that both the body and spec of `Unit_1' be elaborated
before the spec of `Unit_2'. However, a rule like that would be far too
restrictive. In particular, it would make it impossible to have routines
in separate packages that were mutually recursive.

You might think that a clever enough compiler could look at the actual
elaboration code and determine an appropriate correct order of
elaboration, but in the general case, this is not possible. Consider
the following example.

In the body of `Unit_1', we have a procedure `Func_1' that references
the variable `Sqrt_1', which is declared in the elaboration code of the
body of `Unit_1':

    Sqrt_1 : Float := Sqrt (0.1);

The elaboration code of the body of `Unit_1' also contains:

    if expression_1 = 1 then
       Q := Unit_2.Func_2;
    end if;

`Unit_2' is exactly parallel, it has a procedure `Func_2' that
references the variable `Sqrt_2', which is declared in the elaboration
code of the body `Unit_2':

    Sqrt_2 : Float := Sqrt (0.1);

The elaboration code of the body of `Unit_2' also contains:

    if expression_2 = 2 then
       Q := Unit_1.Func_1;
    end if;

Now the question is, which of the following orders of elaboration is
acceptable:

    Spec of Unit_1
    Spec of Unit_2
    Body of Unit_1
    Body of Unit_2

or

    Spec of Unit_2
    Spec of Unit_1
    Body of Unit_2
    Body of Unit_1

If you carefully analyze the flow here, you will see that you cannot
tell at compile time the answer to this question.  If `expression_1' is
not equal to 1, and `expression_2' is not equal to 2, then either order
is acceptable, because neither of the function calls is executed. If
both tests evaluate to true, then neither order is acceptable and in
fact there is no correct order.

If one of the two expressions is true, and the other is false, then one
of the above orders is correct, and the other is incorrect. For example,
if `expression_1' /= 1 and `expression_2' = 2, then the call to `Func_1'
will occur, but not the call to `Func_2.'  This means that it is
essential to elaborate the body of `Unit_1' before the body of
`Unit_2', so the first order of elaboration is correct and the second
is wrong.

By making `expression_1' and `expression_2' depend on input data, or
perhaps the time of day, we can make it impossible for the compiler or
binder to figure out which of these expressions will be true, and hence
it is impossible to guarantee a safe order of elaboration at run time.


File: gnat_ugn.info,  Node: Checking the Elaboration Order,  Next: Controlling the Elaboration Order,  Prev: Elaboration Code,  Up: Elaboration Order Handling in GNAT

11.2 Checking the Elaboration Order
===================================

In some languages that involve the same kind of elaboration problems,
e.g., Java and C++, the programmer needs to take these ordering
problems into account, and it is common to write a program in which an
incorrect elaboration order  gives surprising results, because it
references variables before they are initialized.  Ada is designed to
be a safe language, and a programmer-beware approach is clearly not
sufficient. Consequently, the language provides three lines of defense:

   * `Standard rules'

     Some standard rules restrict the possible choice of elaboration
     order. In particular, if you `with' a unit, then its spec is always
     elaborated before the unit doing the `with'. Similarly, a parent
     spec is always elaborated before the child spec, and finally a
     spec is always elaborated before its corresponding body.

   * `Dynamic elaboration checks'

     Dynamic checks are made at run time, so that if some entity is
     accessed before it is elaborated (typically  by means of a
     subprogram call) then the exception (`Program_Error') is raised.

   * `Elaboration control'

     Facilities are provided for the programmer to specify the desired
     order of elaboration.

Let's look at these facilities in more detail. First, the rules for
dynamic checking. One possible rule would be simply to say that the
exception is raised if you access a variable which has not yet been
elaborated. The trouble with this approach is that it could require
expensive checks on every variable reference. Instead Ada has two rules
which are a little more restrictive, but easier to check, and easier to
state:

   * `Restrictions on calls'

     A subprogram can only be called at elaboration time if its body
     has been elaborated. The rules for elaboration given above
     guarantee that the spec of the subprogram has been elaborated
     before the call, but not the body. If this rule is violated, then
     the exception `Program_Error' is raised.

   * `Restrictions on instantiations'

     A generic unit can only be instantiated if the body of the generic
     unit has been elaborated. Again, the rules for elaboration given
     above guarantee that the spec of the generic unit has been
     elaborated before the instantiation, but not the body. If this
     rule is violated, then the exception `Program_Error' is raised.

The idea is that if the body has been elaborated, then any variables it
references must have been elaborated; by checking for the body being
elaborated we guarantee that none of its references causes any trouble.
As we noted above, this is a little too restrictive, because a
subprogram that has no non-local references in its body may in fact be
safe to call. However, it really would be unsafe to rely on this,
because it would mean that the caller was aware of details of the
implementation in the body. This goes against the basic tenets of Ada.

A plausible implementation can be described as follows.  A Boolean
variable is associated with each subprogram and each generic unit. This
variable is initialized to False, and is set to True at the point body
is elaborated. Every call or instantiation checks the variable, and
raises `Program_Error' if the variable is False.

Note that one might think that it would be good enough to have one
Boolean variable for each package, but that would not deal with cases
of trying to call a body in the same package as the call that has not
been elaborated yet.  Of course a compiler may be able to do enough
analysis to optimize away some of the Boolean variables as unnecessary,
and `GNAT' indeed does such optimizations, but still the easiest
conceptual model is to think of there being one variable per subprogram.


File: gnat_ugn.info,  Node: Controlling the Elaboration Order,  Next: Controlling Elaboration in GNAT - Internal Calls,  Prev: Checking the Elaboration Order,  Up: Elaboration Order Handling in GNAT

11.3 Controlling the Elaboration Order
======================================

In the previous section we discussed the rules in Ada which ensure that
`Program_Error' is raised if an incorrect elaboration order is chosen.
This prevents erroneous executions, but we need mechanisms to specify a
correct execution and avoid the exception altogether.  To achieve this,
Ada provides a number of features for controlling the order of
elaboration. We discuss these features in this section.

First, there are several ways of indicating to the compiler that a given
unit has no elaboration problems:

   * `packages that do not require a body'

     A library package that does not require a body does not permit a
     body (this rule was introduced in Ada 95).  Thus if we have a such
     a package, as in:

         package Definitions is
            generic
               type m is new integer;
            package Subp is
               type a is array (1 .. 10) of m;
               type b is array (1 .. 20) of m;
            end Subp;
         end Definitions;

     A package that `with's `Definitions' may safely instantiate
     `Definitions.Subp' because the compiler can determine that there
     definitely is no package body to worry about in this case

   * `pragma Pure'

     This pragma places sufficient restrictions on a unit to guarantee
     that no call to any subprogram in the unit can result in an
     elaboration problem. This means that the compiler does not need to
     worry about the point of elaboration of such units, and in
     particular, does not need to check any calls to any subprograms in
     this unit.

   * `pragma Preelaborate'

     This pragma places slightly less stringent restrictions on a unit
     than does pragma Pure, but these restrictions are still sufficient
     to ensure that there are no elaboration problems with any calls to
     the unit.

   * `pragma Elaborate_Body'

     This pragma requires that the body of a unit be elaborated
     immediately after its spec. Suppose a unit `A' has such a pragma,
     and unit `B' does a `with' of unit `A'. Recall that the standard
     rules require the spec of unit `A' to be elaborated before the
     `with'ing unit; given the pragma in `A', we also know that the
     body of `A' will be elaborated before `B', so that calls to `A'
     are safe and do not need a check.

     Note that, unlike pragma `Pure' and pragma `Preelaborate', the use
     of `Elaborate_Body' does not guarantee that the program is free of
     elaboration problems, because it may not be possible to satisfy
     the requested elaboration order.  Let's go back to the example
     with `Unit_1' and `Unit_2'.  If a programmer marks `Unit_1' as
     `Elaborate_Body', and not `Unit_2,' then the order of elaboration
     will be:

         Spec of Unit_2
         Spec of Unit_1
         Body of Unit_1
         Body of Unit_2

     Now that means that the call to `Func_1' in `Unit_2' need not be
     checked, it must be safe. But the call to `Func_2' in `Unit_1' may
     still fail if `Expression_1' is equal to 1, and the programmer
     must still take responsibility for this not being the case.

     If all units carry a pragma `Elaborate_Body', then all problems are
     eliminated, except for calls entirely within a body, which are in
     any case fully under programmer control. However, using the pragma
     everywhere is not always possible.  In particular, for our
     `Unit_1'/`Unit_2' example, if we marked both of them as having
     pragma `Elaborate_Body', then clearly there would be no possible
     elaboration order.

The above pragmas allow a server to guarantee safe use by clients, and
clearly this is the preferable approach. Consequently a good rule is to
mark units as `Pure' or `Preelaborate' if possible, and if this is not
possible, mark them as `Elaborate_Body' if possible.  As we have seen,
there are situations where neither of these three pragmas can be used.
So we also provide methods for clients to control the order of
elaboration of the servers on which they depend:

   * `pragma Elaborate (unit)'

     This pragma is placed in the context clause, after a `with' clause,
     and it requires that the body of the named unit be elaborated
     before the unit in which the pragma occurs. The idea is to use
     this pragma if the current unit calls at elaboration time,
     directly or indirectly, some subprogram in the named unit.

   * `pragma Elaborate_All (unit)'

     This is a stronger version of the Elaborate pragma. Consider the
     following example:

         Unit A |withs| unit B and calls B.Func in elab code
         Unit B |withs| unit C, and B.Func calls C.Func

     Now if we put a pragma `Elaborate (B)' in unit `A', this ensures
     that the body of `B' is elaborated before the call, but not the
     body of `C', so the call to `C.Func' could still cause
     `Program_Error' to be raised.

     The effect of a pragma `Elaborate_All' is stronger, it requires
     not only that the body of the named unit be elaborated before the
     unit doing the `with', but also the bodies of all units that the
     named unit uses, following `with' links transitively. For example,
     if we put a pragma `Elaborate_All (B)' in unit `A', then it
     requires not only that the body of `B' be elaborated before `A',
     but also the body of `C', because `B' `with's `C'.

We are now in a position to give a usage rule in Ada for avoiding
elaboration problems, at least if dynamic dispatching and access to
subprogram values are not used. We will handle these cases separately
later.

The rule is simple:

`If a unit has elaboration code that can directly or indirectly make a
call to a subprogram in a |withed| unit, or instantiate a generic
package in a |withed| unit, then if the |withed| unit does not have
pragma `Pure` or `Preelaborate`, then the client should have a pragma
`Elaborate_All`for the |withed| unit.*'

By following this rule a client is assured that calls can be made
without risk of an exception.

For generic subprogram instantiations, the rule can be relaxed to
require only a pragma `Elaborate' since elaborating the body of a
subprogram cannot cause any transitive elaboration (we are not calling
the subprogram in this case, just elaborating its declaration).

If this rule is not followed, then a program may be in one of four
states:

   * `No order exists'

     No order of elaboration exists which follows the rules, taking into
     account any `Elaborate', `Elaborate_All', or `Elaborate_Body'
     pragmas. In this case, an Ada compiler must diagnose the situation
     at bind time, and refuse to build an executable program.

   * `One or more orders exist, all incorrect'

     One or more acceptable elaboration orders exist, and all of them
     generate an elaboration order problem. In this case, the binder
     can build an executable program, but `Program_Error' will be raised
     when the program is run.

   * `Several orders exist, some right, some incorrect'

     One or more acceptable elaboration orders exists, and some of them
     work, and some do not. The programmer has not controlled the order
     of elaboration, so the binder may or may not pick one of the
     correct orders, and the program may or may not raise an exception
     when it is run. This is the worst case, because it means that the
     program may fail when moved to another compiler, or even another
     version of the same compiler.

   * `One or more orders exists, all correct'

     One ore more acceptable elaboration orders exist, and all of them
     work. In this case the program runs successfully. This state of
     affairs can be guaranteed by following the rule we gave above, but
     may be true even if the rule is not followed.

Note that one additional advantage of following our rules on the use of
`Elaborate' and `Elaborate_All' is that the program continues to stay
in the ideal (all orders OK) state even if maintenance changes some
bodies of some units. Conversely, if a program that does not follow
this rule happens to be safe at some point, this state of affairs may
deteriorate silently as a result of maintenance changes.

You may have noticed that the above discussion did not mention the use
of `Elaborate_Body'. This was a deliberate omission. If you `with' an
`Elaborate_Body' unit, it still may be the case that code in the body
makes calls to some other unit, so it is still necessary to use
`Elaborate_All' on such units.


File: gnat_ugn.info,  Node: Controlling Elaboration in GNAT - Internal Calls,  Next: Controlling Elaboration in GNAT - External Calls,  Prev: Controlling the Elaboration Order,  Up: Elaboration Order Handling in GNAT

11.4 Controlling Elaboration in GNAT - Internal Calls
=====================================================

In the case of internal calls, i.e., calls within a single package, the
programmer has full control over the order of elaboration, and it is up
to the programmer to elaborate declarations in an appropriate order. For
example writing:

    function One return Float;

    Q : Float := One;

    function One return Float is
    begin
         return 1.0;
    end One;

will obviously raise `Program_Error' at run time, because function One
will be called before its body is elaborated. In this case GNAT will
generate a warning that the call will raise `Program_Error':

     1. procedure y is
     2.    function One return Float;
     3.
     4.    Q : Float := One;
                        |
        >>> warning: cannot call "One" before body is elaborated
        >>> warning: Program_Error will be raised at run time

     5.
     6.    function One return Float is
     7.    begin
     8.         return 1.0;
     9.    end One;
    10.
    11. begin
    12.    null;
    13. end;

Note that in this particular case, it is likely that the call is safe,
because the function `One' does not access any global variables.
Nevertheless in Ada, we do not want the validity of the check to depend
on the contents of the body (think about the separate compilation
case), so this is still wrong, as we discussed in the previous sections.

The error is easily corrected by rearranging the declarations so that
the body of `One' appears before the declaration containing the call
(note that in Ada 95 as well as later versions of the Ada standard,
declarations can appear in any order, so there is no restriction that
would prevent this reordering, and if we write:

    function One return Float;

    function One return Float is
    begin
         return 1.0;
    end One;

    Q : Float := One;

then all is well, no warning is generated, and no `Program_Error'
exception will be raised.  Things are more complicated when a chain of
subprograms is executed:

    function A return Integer;
    function B return Integer;
    function C return Integer;

    function B return Integer is begin return A; end;
    function C return Integer is begin return B; end;

    X : Integer := C;

    function A return Integer is begin return 1; end;

Now the call to `C' at elaboration time in the declaration of `X' is
correct, because the body of `C' is already elaborated, and the call to
`B' within the body of `C' is correct, but the call to `A' within the
body of `B' is incorrect, because the body of `A' has not been
elaborated, so `Program_Error' will be raised on the call to `A'.  In
this case GNAT will generate a warning that `Program_Error' may be
raised at the point of the call. Let's look at the warning:

     1. procedure x is
     2.    function A return Integer;
     3.    function B return Integer;
     4.    function C return Integer;
     5.
     6.    function B return Integer is begin return A; end;
                                                        |
        >>> warning: call to "A" before body is elaborated may
                     raise Program_Error
        >>> warning: "B" called at line 7
        >>> warning: "C" called at line 9

     7.    function C return Integer is begin return B; end;
     8.
     9.    X : Integer := C;
    10.
    11.    function A return Integer is begin return 1; end;
    12.
    13. begin
    14.    null;
    15. end;

Note that the message here says 'may raise', instead of the direct case,
where the message says 'will be raised'. That's because whether `A' is
actually called depends in general on run-time flow of control.  For
example, if the body of `B' said

    function B return Integer is
    begin
       if some-condition-depending-on-input-data then
          return A;
       else
          return 1;
       end if;
    end B;

then we could not know until run time whether the incorrect call to A
would actually occur, so `Program_Error' might or might not be raised.
It is possible for a compiler to do a better job of analyzing bodies, to
determine whether or not `Program_Error' might be raised, but it
certainly couldn't do a perfect job (that would require solving the
halting problem and is provably impossible), and because this is a
warning anyway, it does not seem worth the effort to do the analysis.
Cases in which it would be relevant are rare.

In practice, warnings of either of the forms given above will usually
correspond to real errors, and should be examined carefully and
eliminated.  In the rare case where a warning is bogus, it can be
suppressed by any of the following methods:

   * Compile with the `-gnatws' switch set

   * Suppress `Elaboration_Check' for the called subprogram

   * Use pragma `Warnings_Off' to turn warnings off for the call

For the internal elaboration check case, GNAT by default generates the
necessary run-time checks to ensure that `Program_Error' is raised if
any call fails an elaboration check. Of course this can only happen if a
warning has been issued as described above. The use of pragma `Suppress
(Elaboration_Check)' may (but is not guaranteed to) suppress some of
these checks, meaning that it may be possible (but is not guaranteed)
for a program to be able to call a subprogram whose body is not yet
elaborated, without raising a `Program_Error' exception.


File: gnat_ugn.info,  Node: Controlling Elaboration in GNAT - External Calls,  Next: Default Behavior in GNAT - Ensuring Safety,  Prev: Controlling Elaboration in GNAT - Internal Calls,  Up: Elaboration Order Handling in GNAT

11.5 Controlling Elaboration in GNAT - External Calls
=====================================================

The previous section discussed the case in which the execution of a
particular thread of elaboration code occurred entirely within a single
unit. This is the easy case to handle, because a programmer has direct
and total control over the order of elaboration, and furthermore,
checks need only be generated in cases which are rare and which the
compiler can easily detect.  The situation is more complex when
separate compilation is taken into account.  Consider the following:

    package Math is
       function Sqrt (Arg : Float) return Float;
    end Math;

    package body Math is
       function Sqrt (Arg : Float) return Float is
       begin
             ...
       end Sqrt;
    end Math;

    with Math;
    package Stuff is
       X : Float := Math.Sqrt (0.5);
    end Stuff;

    with Stuff;
    procedure Main is
    begin
       ...
    end Main;

where `Main' is the main program. When this program is executed, the
elaboration code must first be executed, and one of the jobs of the
binder is to determine the order in which the units of a program are to
be elaborated. In this case we have four units: the spec and body of
`Math', the spec of `Stuff' and the body of `Main').  In what order
should the four separate sections of elaboration code be executed?

There are some restrictions in the order of elaboration that the binder
can choose. In particular, if unit U has a `with' for a package `X',
then you are assured that the spec of `X' is elaborated before U , but
you are not assured that the body of `X' is elaborated before U.  This
means that in the above case, the binder is allowed to choose the order:

    spec of Math
    spec of Stuff
    body of Math
    body of Main

but that's not good, because now the call to `Math.Sqrt' that happens
during the elaboration of the `Stuff' spec happens before the body of
`Math.Sqrt' is elaborated, and hence causes `Program_Error' exception
to be raised.  At first glance, one might say that the binder is
misbehaving, because obviously you want to elaborate the body of
something you `with' first, but that is not a general rule that can be
followed in all cases. Consider

    package X is ...

    package Y is ...

    with X;
    package body Y is ...

    with Y;
    package body X is ...

This is a common arrangement, and, apart from the order of elaboration
problems that might arise in connection with elaboration code, this
works fine.  A rule that says that you must first elaborate the body of
anything you `with' cannot work in this case: the body of `X' `with's
`Y', which means you would have to elaborate the body of `Y' first, but
that `with's `X', which means you have to elaborate the body of `X'
first, but ... and we have a loop that cannot be broken.

It is true that the binder can in many cases guess an order of
elaboration that is unlikely to cause a `Program_Error' exception to be
raised, and it tries to do so (in the above example of
`Math/Stuff/Spec', the GNAT binder will by default elaborate the body
of `Math' right after its spec, so all will be well).

However, a program that blindly relies on the binder to be helpful can
get into trouble, as we discussed in the previous sections, so GNAT
provides a number of facilities for assisting the programmer in
developing programs that are robust with respect to elaboration order.


File: gnat_ugn.info,  Node: Default Behavior in GNAT - Ensuring Safety,  Next: Treatment of Pragma Elaborate,  Prev: Controlling Elaboration in GNAT - External Calls,  Up: Elaboration Order Handling in GNAT

11.6 Default Behavior in GNAT - Ensuring Safety
===============================================

The default behavior in GNAT ensures elaboration safety. In its default
mode GNAT implements the rule we previously described as the right
approach. Let's restate it:

`If a unit has elaboration code that can directly or indirectly make a
call to a subprogram in a |withed| unit, or instantiate a generic
package in a |withed| unit, then if the |withed| unit does not have
pragma `Pure` or `Preelaborate`, then the client should have an
`Elaborate_All` pragma for the |withed| unit.'

`In the case of instantiating a generic subprogram, it is always
sufficient to have only an `Elaborate` pragma for the |withed| unit.'

By following this rule a client is assured that calls and instantiations
can be made without risk of an exception.

In this mode GNAT traces all calls that are potentially made from
elaboration code, and puts in any missing implicit `Elaborate' and
`Elaborate_All' pragmas.  The advantage of this approach is that no
elaboration problems are possible if the binder can find an elaboration
order that is consistent with these implicit `Elaborate' and
`Elaborate_All' pragmas. The disadvantage of this approach is that no
such order may exist.

If the binder does not generate any diagnostics, then it means that it
has found an elaboration order that is guaranteed to be safe. However,
the binder may still be relying on implicitly generated `Elaborate' and
`Elaborate_All' pragmas so portability to other compilers than GNAT is
not guaranteed.

If it is important to guarantee portability, then the compilations
should use the `-gnatel' (info messages for elaboration pragmas)
switch. This will cause info messages to be generated indicating the
missing `Elaborate' and `Elaborate_All' pragmas.  Consider the
following source program:

    with k;
    package j is
      m : integer := k.r;
    end;

where it is clear that there should be a pragma `Elaborate_All' for
unit `k'. An implicit pragma will be generated, and it is likely that
the binder will be able to honor it. However, if you want to port this
program to some other Ada compiler than GNAT.  it is safer to include
the pragma explicitly in the source. If this unit is compiled with the
`-gnatel' switch, then the compiler outputs an information message:

    1. with k;
    2. package j is
    3.   m : integer := k.r;
                         |
       >>> info: call to "r" may raise Program_Error
       >>> info: missing pragma Elaborate_All for "k"

    4. end;

and these messages can be used as a guide for supplying manually the
missing pragmas. It is usually a bad idea to use this option during
development. That's because it will tell you when you need to put in a
pragma, but cannot tell you when it is time to take it out. So the use
of pragma `Elaborate_All' may lead to unnecessary dependencies and even
false circularities.

This default mode is more restrictive than the Ada Reference Manual,
and it is possible to construct programs which will compile using the
dynamic model described there, but will run into a circularity using
the safer static model we have described.

Of course any Ada compiler must be able to operate in a mode consistent
with the requirements of the Ada Reference Manual, and in particular
must have the capability of implementing the standard dynamic model of
elaboration with run-time checks.

In GNAT, this standard mode can be achieved either by the use of the
`-gnatE' switch on the compiler (`gcc' or `gnatmake') command, or by
the use of the configuration pragma:

    pragma Elaboration_Checks (DYNAMIC);

Either approach will cause the unit affected to be compiled using the
standard dynamic run-time elaboration checks described in the Ada
Reference Manual. The static model is generally preferable, since it is
clearly safer to rely on compile and link time checks rather than
run-time checks. However, in the case of legacy code, it may be
difficult to meet the requirements of the static model. This issue is
further discussed in *note What to Do If the Default Elaboration
Behavior Fails: 2c9.

Note that the static model provides a strict subset of the allowed
behavior and programs of the Ada Reference Manual, so if you do adhere
to the static model and no circularities exist, then you are assured
that your program will work using the dynamic model, providing that you
remove any pragma Elaborate statements from the source.


File: gnat_ugn.info,  Node: Treatment of Pragma Elaborate,  Next: Elaboration Issues for Library Tasks,  Prev: Default Behavior in GNAT - Ensuring Safety,  Up: Elaboration Order Handling in GNAT

11.7 Treatment of Pragma Elaborate
==================================

The use of `pragma Elaborate' should generally be avoided in Ada 95 and
Ada 2005 programs, since there is no guarantee that transitive calls
will be properly handled. Indeed at one point, this pragma was placed
in Annex J (Obsolescent Features), on the grounds that it is never
useful.

Now that's a bit restrictive. In practice, the case in which `pragma
Elaborate' is useful is when the caller knows that there are no
transitive calls, or that the called unit contains all necessary
transitive `pragma Elaborate' statements, and legacy code often
contains such uses.

Strictly speaking the static mode in GNAT should ignore such pragmas,
since there is no assurance at compile time that the necessary safety
conditions are met. In practice, this would cause GNAT to be
incompatible with correctly written Ada 83 code that had all necessary
`pragma Elaborate' statements in place. Consequently, we made the
decision that GNAT in its default mode will believe that if it
encounters a `pragma Elaborate' then the programmer knows what they are
doing, and it will trust that no elaboration errors can occur.

The result of this decision is two-fold. First to be safe using the
static mode, you should remove all `pragma Elaborate' statements.
Second, when fixing circularities in existing code, you can selectively
use `pragma Elaborate' statements to convince the static mode of GNAT
that it need not generate an implicit `pragma Elaborate_All' statement.

When using the static mode with `-gnatwl', any use of `pragma
Elaborate' will generate a warning about possible problems.


File: gnat_ugn.info,  Node: Elaboration Issues for Library Tasks,  Next: Mixing Elaboration Models,  Prev: Treatment of Pragma Elaborate,  Up: Elaboration Order Handling in GNAT

11.8 Elaboration Issues for Library Tasks
=========================================

In this section we examine special elaboration issues that arise for
programs that declare library level tasks.

Generally the model of execution of an Ada program is that all units are
elaborated, and then execution of the program starts. However, the
declaration of library tasks definitely does not fit this model. The
reason for this is that library tasks start as soon as they are declared
(more precisely, as soon as the statement part of the enclosing package
body is reached), that is to say before elaboration of the program is
complete. This means that if such a task calls a subprogram, or an
entry in another task, the callee may or may not be elaborated yet, and
in the standard Reference Manual model of dynamic elaboration checks,
you can even get timing dependent Program_Error exceptions, since there
can be a race between the elaboration code and the task code.

The static model of elaboration in GNAT seeks to avoid all such dynamic
behavior, by being conservative, and the conservative approach in this
particular case is to assume that all the code in a task body is
potentially executed at elaboration time if a task is declared at the
library level.

This can definitely result in unexpected circularities. Consider the
following example

    package Decls is
      task Lib_Task is
         entry Start;
      end Lib_Task;

      type My_Int is new Integer;

      function Ident (M : My_Int) return My_Int;
    end Decls;

    with Utils;
    package body Decls is
      task body Lib_Task is
      begin
         accept Start;
         Utils.Put_Val (2);
      end Lib_Task;

      function Ident (M : My_Int) return My_Int is
      begin
         return M;
      end Ident;
    end Decls;

    with Decls;
    package Utils is
      procedure Put_Val (Arg : Decls.My_Int);
    end Utils;

    with Text_IO;
    package body Utils is
      procedure Put_Val (Arg : Decls.My_Int) is
      begin
         Text_IO.Put_Line (Decls.My_Int'Image (Decls.Ident (Arg)));
      end Put_Val;
    end Utils;

    with Decls;
    procedure Main is
    begin
       Decls.Lib_Task.Start;
    end;

If the above example is compiled in the default static elaboration
mode, then a circularity occurs. The circularity comes from the call
`Utils.Put_Val' in the task body of `Decls.Lib_Task'. Since this call
occurs in elaboration code, we need an implicit pragma `Elaborate_All'
for `Utils'. This means that not only must the spec and body of `Utils'
be elaborated before the body of `Decls', but also the spec and body of
any unit that is `with'ed by the body of `Utils' must also be
elaborated before the body of `Decls'. This is the transitive
implication of pragma `Elaborate_All' and it makes sense, because in
general the body of `Put_Val' might have a call to something in a
`with'ed unit.

In this case, the body of Utils (actually its spec) `with's `Decls'.
Unfortunately this means that the body of `Decls' must be elaborated
before itself, in case there is a call from the body of `Utils'.

Here is the exact chain of events we are worrying about:

   * In the body of `Decls' a call is made from within the body of a
     library task to a subprogram in the package `Utils'. Since this
     call may occur at elaboration time (given that the task is
     activated at elaboration time), we have to assume the worst, i.e.,
     that the call does happen at elaboration time.

   * This means that the body and spec of `Util' must be elaborated
     before the body of `Decls' so that this call does not cause an
     access before elaboration.

   * Within the body of `Util', specifically within the body of
     `Util.Put_Val' there may be calls to any unit `with'ed by this
     package.

   * One such `with'ed package is package `Decls', so there might be a
     call to a subprogram in `Decls' in `Put_Val'.  In fact there is
     such a call in this example, but we would have to assume that
     there was such a call even if it were not there, since we are not
     supposed to write the body of `Decls' knowing what is in the body
     of `Utils'; certainly in the case of the static elaboration model,
     the compiler does not know what is in other bodies and must assume
     the worst.

   * This means that the spec and body of `Decls' must also be
     elaborated before we elaborate the unit containing the call, but
     that unit is `Decls'! This means that the body of `Decls' must be
     elaborated before itself, and that's a circularity.

Indeed, if you add an explicit pragma `Elaborate_All' for `Utils' in
the body of `Decls' you will get a true Ada Reference Manual
circularity that makes the program illegal.

In practice, we have found that problems with the static model of
elaboration in existing code often arise from library tasks, so we must
address this particular situation.

Note that if we compile and run the program above, using the dynamic
model of elaboration (that is to say use the `-gnatE' switch), then it
compiles, binds, links, and runs, printing the expected result of 2.
Therefore in some sense the circularity here is only apparent, and we
need to capture the properties of this program that  distinguish it
from other library-level tasks that have real elaboration problems.

We have four possible answers to this question:

   * Use the dynamic model of elaboration.

     If we use the `-gnatE' switch, then as noted above, the program
     works.  Why is this? If we examine the task body, it is apparent
     that the task cannot proceed past the `accept' statement until
     after elaboration has been completed, because the corresponding
     entry call comes from the main program, not earlier.  This is why
     the dynamic model works here. But that's really giving up on a
     precise analysis, and we prefer to take this approach only if we
     cannot solve the problem in any other manner. So let us examine
     two ways to reorganize the program to avoid the potential
     elaboration problem.

   * Split library tasks into separate packages.

     Write separate packages, so that library tasks are isolated from
     other declarations as much as possible. Let us look at a variation
     on the above program.

         package Decls1 is
           task Lib_Task is
              entry Start;
           end Lib_Task;
         end Decls1;

         with Utils;
         package body Decls1 is
           task body Lib_Task is
           begin
              accept Start;
              Utils.Put_Val (2);
           end Lib_Task;
         end Decls1;

         package Decls2 is
           type My_Int is new Integer;
           function Ident (M : My_Int) return My_Int;
         end Decls2;

         with Utils;
         package body Decls2 is
           function Ident (M : My_Int) return My_Int is
           begin
              return M;
           end Ident;
         end Decls2;

         with Decls2;
         package Utils is
           procedure Put_Val (Arg : Decls2.My_Int);
         end Utils;

         with Text_IO;
         package body Utils is
           procedure Put_Val (Arg : Decls2.My_Int) is
           begin
              Text_IO.Put_Line (Decls2.My_Int'Image (Decls2.Ident (Arg)));
           end Put_Val;
         end Utils;

         with Decls1;
         procedure Main is
         begin
            Decls1.Lib_Task.Start;
         end;

     All we have done is to split `Decls' into two packages, one
     containing the library task, and one containing everything else.
     Now there is no cycle, and the program compiles, binds, links and
     executes using the default static model of elaboration.

   * Declare separate task types.

     A significant part of the problem arises because of the use of the
     single task declaration form. This means that the elaboration of
     the task type, and the elaboration of the task itself (i.e., the
     creation of the task) happen at the same time. A good rule of
     style in Ada is to always create explicit task types. By following
     the additional step of placing task objects in separate packages
     from the task type declaration, many elaboration problems are
     avoided. Here is another modified example of the example program:

         package Decls is
           task type Lib_Task_Type is
              entry Start;
           end Lib_Task_Type;

           type My_Int is new Integer;

           function Ident (M : My_Int) return My_Int;
         end Decls;

         with Utils;
         package body Decls is
           task body Lib_Task_Type is
           begin
              accept Start;
              Utils.Put_Val (2);
           end Lib_Task_Type;

           function Ident (M : My_Int) return My_Int is
           begin
              return M;
           end Ident;
         end Decls;

         with Decls;
         package Utils is
           procedure Put_Val (Arg : Decls.My_Int);
         end Utils;

         with Text_IO;
         package body Utils is
           procedure Put_Val (Arg : Decls.My_Int) is
           begin
              Text_IO.Put_Line (Decls.My_Int'Image (Decls.Ident (Arg)));
           end Put_Val;
         end Utils;

         with Decls;
         package Declst is
            Lib_Task : Decls.Lib_Task_Type;
         end Declst;

         with Declst;
         procedure Main is
         begin
            Declst.Lib_Task.Start;
         end;

     What we have done here is to replace the `task' declaration in
     package `Decls' with a `task type' declaration. Then we introduce
     a separate package `Declst' to contain the actual task object.
     This separates the elaboration issues for the `task type'
     declaration, which causes no trouble, from the elaboration issues
     of the task object, which is also unproblematic, since it is now
     independent of the elaboration of  `Utils'.  This separation of
     concerns also corresponds to a generally sound engineering
     principle of separating declarations from instances. This version
     of the program also compiles, binds, links, and executes,
     generating the expected output.

   * Use No_Entry_Calls_In_Elaboration_Code restriction.

     The previous two approaches described how a program can be
     restructured to avoid the special problems caused by library task
     bodies. in practice, however, such restructuring may be difficult
     to apply to existing legacy code, so we must consider solutions
     that do not require massive rewriting.

     Let us consider more carefully why our original sample program
     works under the dynamic model of elaboration. The reason is that
     the code in the task body blocks immediately on the `accept'
     statement. Now of course there is nothing to prohibit elaboration
     code from making entry calls (for example from another library
     level task), so we cannot tell in isolation that the task will not
     execute the accept statement  during elaboration.

     However, in practice it is very unusual to see elaboration code
     make any entry calls, and the pattern of tasks starting at
     elaboration time and then immediately blocking on `accept' or
     `select' statements is very common. What this means is that the
     compiler is being too pessimistic when it analyzes the whole
     package body as though it might be executed at elaboration time.

     If we know that the elaboration code contains no entry calls, (a
     very safe assumption most of the time, that could almost be made
     the default behavior), then we can compile all units of the
     program under control of the following configuration pragma:

         pragma Restrictions (No_Entry_Calls_In_Elaboration_Code);

     This pragma can be placed in the `gnat.adc' file in the usual
     manner. If we take our original unmodified program and compile it
     in the presence of a `gnat.adc' containing the above pragma, then
     once again, we can compile, bind, link, and execute, obtaining the
     expected result. In the presence of this pragma, the compiler does
     not trace calls in a task body, that appear after the first
     `accept' or `select' statement, and therefore does not report a
     potential circularity in the original program.

     The compiler will check to the extent it can that the above
     restriction is not violated, but it is not always possible to do a
     complete check at compile time, so it is important to use this
     pragma only if the stated restriction is in fact met, that is to
     say no task receives an entry call before elaboration of all units
     is completed.


File: gnat_ugn.info,  Node: Mixing Elaboration Models,  Next: What to Do If the Default Elaboration Behavior Fails,  Prev: Elaboration Issues for Library Tasks,  Up: Elaboration Order Handling in GNAT

11.9 Mixing Elaboration Models
==============================

So far, we have assumed that the entire program is either compiled
using the dynamic model or static model, ensuring consistency. It is
possible to mix the two models, but rules have to be followed if this
mixing is done to ensure that elaboration checks are not omitted.

The basic rule is that `a unit compiled with the static model cannot be
|withed| by a unit compiled with the dynamic model'.  The reason for
this is that in the static model, a unit assumes that its clients
guarantee to use (the equivalent of) pragma `Elaborate_All' so that no
elaboration checks are required in inner subprograms, and this
assumption is violated if the client is compiled with dynamic checks.

The precise rule is as follows. A unit that is compiled with dynamic
checks can only `with' a unit that meets at least one of the following
criteria:

   * The `with'ed unit is itself compiled with dynamic elaboration
     checks (that is with the `-gnatE' switch.

   * The `with'ed unit is an internal GNAT implementation unit from the
     System, Interfaces, Ada, or GNAT hierarchies.

   * The `with'ed unit has pragma Preelaborate or pragma Pure.

   * The `with'ing unit (that is the client) has an explicit pragma
     `Elaborate_All' for the `with'ed unit.

If this rule is violated, that is if a unit with dynamic elaboration
checks `with's a unit that does not meet one of the above four
criteria, then the binder (`gnatbind') will issue a warning similar to
that in the following example:

    warning: "x.ads" has dynamic elaboration checks and with's
    warning:   "y.ads" which has static elaboration checks

These warnings indicate that the rule has been violated, and that as a
result elaboration checks may be missed in the resulting executable
file.  This warning may be suppressed using the `-ws' binder switch in
the usual manner.

One useful application of this mixing rule is in the case of a subsystem
which does not itself `with' units from the remainder of the
application. In this case, the entire subsystem can be compiled with
dynamic checks to resolve a circularity in the subsystem, while
allowing the main application that uses this subsystem to be compiled
using the more reliable default static model.


File: gnat_ugn.info,  Node: What to Do If the Default Elaboration Behavior Fails,  Next: Elaboration for Indirect Calls,  Prev: Mixing Elaboration Models,  Up: Elaboration Order Handling in GNAT

11.10 What to Do If the Default Elaboration Behavior Fails
==========================================================

If the binder cannot find an acceptable order, it outputs detailed
diagnostics. For example:

    error: elaboration circularity detected
    info:   "proc (body)" must be elaborated before "pack (body)"
    info:     reason: Elaborate_All probably needed in unit "pack (body)"
    info:     recompile "pack (body)" with -gnatel
    info:                             for full details
    info:       "proc (body)"
    info:         is needed by its spec:
    info:       "proc (spec)"
    info:         which is withed by:
    info:       "pack (body)"
    info:  "pack (body)" must be elaborated before "proc (body)"
    info:     reason: pragma Elaborate in unit "proc (body)"

In this case we have a cycle that the binder cannot break. On the one
hand, there is an explicit pragma Elaborate in `proc' for `pack'. This
means that the body of `pack' must be elaborated before the body of
`proc'. On the other hand, there is elaboration code in `pack' that
calls a subprogram in `proc'. This means that for maximum safety, there
should really be a pragma Elaborate_All in `pack' for `proc' which
would require that the body of `proc' be elaborated before the body of
`pack'. Clearly both requirements cannot be satisfied.  Faced with a
circularity of this kind, you have three different options.

   * `Fix the program'

     The most desirable option from the point of view of long-term
     maintenance is to rearrange the program so that the elaboration
     problems are avoided.  One useful technique is to place the
     elaboration code into separate child packages. Another is to move
     some of the initialization code to explicitly called subprograms,
     where the program controls the order of initialization explicitly.
     Although this is the most desirable option, it may be impractical
     and involve too much modification, especially in the case of
     complex legacy code.

   * `Perform dynamic checks'

     If the compilations are done using the `-gnatE' (dynamic
     elaboration check) switch, then GNAT behaves in a quite different
     manner. Dynamic checks are generated for all calls that could
     possibly result in raising an exception. With this switch, the
     compiler does not generate implicit `Elaborate' or `Elaborate_All'
     pragmas. The behavior then is exactly as specified in the `Ada
     Reference Manual'.  The binder will generate an executable program
     that may or may not raise `Program_Error', and then it is the
     programmer's job to ensure that it does not raise an exception.
     Note that it is important to compile all units with the switch, it
     cannot be used selectively.

   * `Suppress checks'

     The drawback of dynamic checks is that they generate a significant
     overhead at run time, both in space and time. If you are
     absolutely sure that your program cannot raise any elaboration
     exceptions, and you still want to use the dynamic elaboration
     model, then you can use the configuration pragma `Suppress
     (Elaboration_Check)' to suppress all such checks. For example this
     pragma could be placed in the `gnat.adc' file.

   * `Suppress checks selectively'

     When you know that certain calls or instantiations in elaboration
     code cannot possibly lead to an elaboration error, and the binder
     nevertheless complains about implicit `Elaborate' and
     `Elaborate_All' pragmas that lead to elaboration circularities, it
     is possible to remove those warnings locally and obtain a program
     that will bind. Clearly this can be unsafe, and it is the
     responsibility of the programmer to make sure that the resulting
     program has no elaboration anomalies. The pragma `Suppress
     (Elaboration_Check)' can be used with different granularity to
     suppress warnings and break elaboration circularities:

        * Place the pragma that names the called subprogram in the
          declarative part that contains the call.

        * Place the pragma in the declarative part, without naming an
          entity. This disables warnings on all calls in the
          corresponding  declarative region.

        * Place the pragma in the package spec that declares the called
          subprogram, and name the subprogram. This disables warnings
          on all elaboration calls to that subprogram.

        * Place the pragma in the package spec that declares the called
          subprogram, without naming any entity. This disables warnings
          on all elaboration calls to all subprograms declared in this
          spec.

        * Use Pragma Elaborate.

          As previously described in section *note Treatment of Pragma
          Elaborate: 2ca, GNAT in static mode assumes that a `pragma'
          Elaborate indicates correctly that no elaboration checks are
          required on calls to the designated unit.  There may be cases
          in which the caller knows that no transitive calls can occur,
          so that a `pragma Elaborate' will be sufficient in a case
          where `pragma Elaborate_All' would cause a circularity.

     These five cases are listed in order of decreasing safety, and
     therefore require increasing programmer care in their application.
     Consider the following program:

         package Pack1 is
           function F1 return Integer;
           X1 : Integer;
         end Pack1;

         package Pack2 is
           function F2 return Integer;
           function Pure (x : integer) return integer;
           --  pragma Suppress (Elaboration_Check, On => Pure);  -- (3)
           --  pragma Suppress (Elaboration_Check);              -- (4)
         end Pack2;

         with Pack2;
         package body Pack1 is
           function F1 return Integer is
           begin
             return 100;
           end F1;
           Val : integer := Pack2.Pure (11);    --  Elab. call (1)
         begin
           declare
             --  pragma Suppress(Elaboration_Check, Pack2.F2);   -- (1)
             --  pragma Suppress(Elaboration_Check);             -- (2)
           begin
             X1 := Pack2.F2 + 1;                --  Elab. call (2)
           end;
         end Pack1;

         with Pack1;
         package body Pack2 is
           function F2 return Integer is
           begin
              return Pack1.F1;
           end F2;
           function Pure (x : integer) return integer is
           begin
              return x ** 3 - 3 * x;
           end;
         end Pack2;

         with Pack1, Ada.Text_IO;
         procedure Proc3 is
         begin
           Ada.Text_IO.Put_Line(Pack1.X1'Img); -- 101
         end Proc3;

     In the absence of any pragmas, an attempt to bind this program
     produces the following diagnostics:

         error: elaboration circularity detected
         info:    "pack1 (body)" must be elaborated before "pack1 (body)"
         info:       reason: Elaborate_All probably needed in unit "pack1 (body)"
         info:       recompile "pack1 (body)" with -gnatel for full details
         info:          "pack1 (body)"
         info:             must be elaborated along with its spec:
         info:          "pack1 (spec)"
         info:             which is withed by:
         info:          "pack2 (body)"
         info:             which must be elaborated along with its spec:
         info:          "pack2 (spec)"
         info:             which is withed by:
         info:          "pack1 (body)"

     The sources of the circularity are the two calls to `Pack2.Pure'
     and `Pack2.F2' in the body of `Pack1'. We can see that the call to
     F2 is safe, even though F2 calls F1, because the call appears
     after the elaboration of the body of F1. Therefore the pragma (1)
     is safe, and will remove the warning on the call. It is also
     possible to use pragma (2) because there are no other potentially
     unsafe calls in the block.

     The call to `Pure' is safe because this function does not depend
     on the state of `Pack2'. Therefore any call to this function is
     safe, and it is correct to place pragma (3) in the corresponding
     package spec.

     Finally, we could place pragma (4) in the spec of `Pack2' to
     disable warnings on all calls to functions declared therein. Note
     that this is not necessarily safe, and requires more detailed
     examination of the subprogram bodies involved. In particular, a
     call to `F2' requires that `F1' be already elaborated.

It is hard to generalize on which of these four approaches should be
taken. Obviously if it is possible to fix the program so that the
default treatment works, this is preferable, but this may not always be
practical.  It is certainly simple enough to use `-gnatE' but the
danger in this case is that, even if the GNAT binder finds a correct
elaboration order, it may not always do so, and certainly a binder from
another Ada compiler might not. A combination of testing and analysis
(for which the information messages generated with the `-gnatel' switch
can be useful) must be used to ensure that the program is free of
errors. One switch that is useful in this testing is the `-p
(pessimistic elaboration order)' switch for `gnatbind'.  Normally the
binder tries to find an order that has the best chance of avoiding
elaboration problems. However, if this switch is used, the binder plays
a devil's advocate role, and tries to choose the order that has the
best chance of failing. If your program works even with this switch,
then it has a better chance of being error free, but this is still not
a guarantee.

For an example of this approach in action, consider the C-tests
(executable tests) from the ACATS suite. If these are compiled and run
with the default treatment, then all but one of them succeed without
generating any error diagnostics from the binder. However, there is one
test that fails, and this is not surprising, because the whole point of
this test is to ensure that the compiler can handle cases where it is
impossible to determine a correct order statically, and it checks that
an exception is indeed raised at run time.

This one test must be compiled and run using the `-gnatE' switch, and
then it passes. Alternatively, the entire suite can be run using this
switch. It is never wrong to run with the dynamic elaboration switch if
your code is correct, and we assume that the C-tests are indeed correct
(it is less efficient, but efficiency is not a factor in running the
ACATS tests.)


File: gnat_ugn.info,  Node: Elaboration for Indirect Calls,  Next: Summary of Procedures for Elaboration Control,  Prev: What to Do If the Default Elaboration Behavior Fails,  Up: Elaboration Order Handling in GNAT

11.11 Elaboration for Indirect Calls
====================================

In rare cases, the static elaboration model fails to prevent
dispatching calls to not-yet-elaborated subprograms. In such cases, we
fall back to run-time checks; premature calls to any primitive
operation of a tagged type before the body of the operation has been
elaborated will raise `Program_Error'.

Access-to-subprogram types, however, are handled conservatively, and do
not require run-time checks. This was not true in earlier versions of
the compiler; you can use the `-gnatd.U' debug switch to revert to the
old behavior if the new conservative behavior causes elaboration
cycles. Here, 'conservative' means that if you do `P'Access' during
elaboration, the compiler will assume that you might call `P'
indirectly during elaboration, so it adds an implicit `pragma
Elaborate_All' on the library unit containing `P'. The `-gnatd.U'
switch is safe if you know there are no such calls. If the program
worked before, it will continue to work with `-gnatd.U'. But beware
that code modifications such as adding an indirect call can cause
erroneous behavior in the presence of `-gnatd.U'.


File: gnat_ugn.info,  Node: Summary of Procedures for Elaboration Control,  Next: Other Elaboration Order Considerations,  Prev: Elaboration for Indirect Calls,  Up: Elaboration Order Handling in GNAT

11.12 Summary of Procedures for Elaboration Control
===================================================

First, compile your program with the default options, using none of the
special elaboration control switches. If the binder successfully binds
your program, then you can be confident that, apart from issues raised
by the use of access-to-subprogram types and dynamic dispatching, the
program is free of elaboration errors. If it is important that the
program be portable to other compilers than GNAT, then use the `-gnatel'
switch to generate messages about missing `Elaborate' or
`Elaborate_All' pragmas, and supply the missing pragmas.

If the program fails to bind using the default static elaboration
handling, then you can fix the program to eliminate the binder message,
or recompile the entire program with the `-gnatE' switch to generate
dynamic elaboration checks, and, if you are sure there really are no
elaboration problems, use a global pragma `Suppress
(Elaboration_Check)'.


File: gnat_ugn.info,  Node: Other Elaboration Order Considerations,  Next: Determining the Chosen Elaboration Order,  Prev: Summary of Procedures for Elaboration Control,  Up: Elaboration Order Handling in GNAT

11.13 Other Elaboration Order Considerations
============================================

This section has been entirely concerned with the issue of finding a
valid elaboration order, as defined by the Ada Reference Manual. In a
case where several elaboration orders are valid, the task is to find one
of the possible valid elaboration orders (and the static model in GNAT
will ensure that this is achieved).

The purpose of the elaboration rules in the Ada Reference Manual is to
make sure that no entity is accessed before it has been elaborated. For
a subprogram, this means that the spec and body must have been
elaborated before the subprogram is called. For an object, this means
that the object must have been elaborated before its value is read or
written. A violation of either of these two requirements is an access
before elaboration order, and this section has been all about avoiding
such errors.

In the case where more than one order of elaboration is possible, in the
sense that access before elaboration errors are avoided, then any one of
the orders is 'correct' in the sense that it meets the requirements of
the Ada Reference Manual, and no such error occurs.

However, it may be the case for a given program, that there are
constraints on the order of elaboration that come not from consideration
of avoiding elaboration errors, but rather from extra-lingual logic
requirements. Consider this example:

    with Init_Constants;
    package Constants is
       X : Integer := 0;
       Y : Integer := 0;
    end Constants;

    package Init_Constants is
       procedure P; --* require a body*
    end Init_Constants;

    with Constants;
    package body Init_Constants is
       procedure P is begin null; end;
    begin
       Constants.X := 3;
       Constants.Y := 4;
    end Init_Constants;

    with Constants;
    package Calc is
       Z : Integer := Constants.X + Constants.Y;
    end Calc;

    with Calc;
    with Text_IO; use Text_IO;
    procedure Main is
    begin
       Put_Line (Calc.Z'Img);
    end Main;

In this example, there is more than one valid order of elaboration. For
example both the following are correct orders:

    Init_Constants spec
    Constants spec
    Calc spec
    Init_Constants body
    Main body

and

    Init_Constants spec
    Init_Constants body
    Constants spec
    Calc spec
    Main body

There is no language rule to prefer one or the other, both are correct
from an order of elaboration point of view. But the programmatic effects
of the two orders are very different. In the first, the elaboration
routine of `Calc' initializes `Z' to zero, and then the main program
runs with this value of zero. But in the second order, the elaboration
routine of `Calc' runs after the body of Init_Constants has set `X' and
`Y' and thus `Z' is set to 7 before `Main' runs.

One could perhaps by applying pretty clever non-artificial intelligence
to the situation guess that it is more likely that the second order of
elaboration is the one desired, but there is no formal linguistic reason
to prefer one over the other. In fact in this particular case, GNAT will
prefer the second order, because of the rule that bodies are elaborated
as soon as possible, but it's just luck that this is what was wanted
(if indeed the second order was preferred).

If the program cares about the order of elaboration routines in a case
like this, it is important to specify the order required. In this
particular case, that could have been achieved by adding to the spec of
Calc:

    pragma Elaborate_All (Constants);

which requires that the body (if any) and spec of `Constants', as well
as the body and spec of any unit `with'ed by `Constants' be elaborated
before `Calc' is elaborated.

Clearly no automatic method can always guess which alternative you
require, and if you are working with legacy code that had constraints
of this kind which were not properly specified by adding `Elaborate' or
`Elaborate_All' pragmas, then indeed it is possible that two different
compilers can choose different orders.

However, GNAT does attempt to diagnose the common situation where there
are uninitialized variables in the visible part of a package spec, and
the corresponding package body has an elaboration block that directly or
indirectly initialized one or more of these variables. This is the
situation in which a pragma Elaborate_Body is usually desirable, and
GNAT will generate a warning that suggests this addition if it detects
this situation.

The `gnatbind' `-p' switch may be useful in smoking out problems. This
switch causes bodies to be elaborated as late as possible instead of as
early as possible. In the example above, it would have forced the
choice of the first elaboration order. If you get different results
when using this switch, and particularly if one set of results is right,
and one is wrong as far as you are concerned, it shows that you have
some missing `Elaborate' pragmas. For the example above, we have the
following output:

    $ gnatmake -f -q main
    $ main
     7
    $ gnatmake -f -q main -bargs -p
    $ main
     0

It is of course quite unlikely that both these results are correct, so
it is up to you in a case like this to investigate the source of the
difference, by looking at the two elaboration orders that are chosen,
and figuring out which is correct, and then adding the necessary
`Elaborate' or `Elaborate_All' pragmas to ensure the desired order.


File: gnat_ugn.info,  Node: Determining the Chosen Elaboration Order,  Prev: Other Elaboration Order Considerations,  Up: Elaboration Order Handling in GNAT

11.14 Determining the Chosen Elaboration Order
==============================================

To see the elaboration order that the binder chooses, you can look at
the last part of the file:`b~xxx.adb' binder output file. Here is an
example:

    System.Soft_Links'Elab_Body;
    E14 := True;
    System.Secondary_Stack'Elab_Body;
    E18 := True;
    System.Exception_Table'Elab_Body;
    E24 := True;
    Ada.Io_Exceptions'Elab_Spec;
    E67 := True;
    Ada.Tags'Elab_Spec;
    Ada.Streams'Elab_Spec;
    E43 := True;
    Interfaces.C'Elab_Spec;
    E69 := True;
    System.Finalization_Root'Elab_Spec;
    E60 := True;
    System.Os_Lib'Elab_Body;
    E71 := True;
    System.Finalization_Implementation'Elab_Spec;
    System.Finalization_Implementation'Elab_Body;
    E62 := True;
    Ada.Finalization'Elab_Spec;
    E58 := True;
    Ada.Finalization.List_Controller'Elab_Spec;
    E76 := True;
    System.File_Control_Block'Elab_Spec;
    E74 := True;
    System.File_Io'Elab_Body;
    E56 := True;
    Ada.Tags'Elab_Body;
    E45 := True;
    Ada.Text_Io'Elab_Spec;
    Ada.Text_Io'Elab_Body;
    E07 := True;

Here Elab_Spec elaborates the spec and Elab_Body elaborates the body.
The assignments to the `E`xx'' flags flag that the corresponding body
is now elaborated.

You can also ask the binder to generate a more readable list of the
elaboration order using the `-l' switch when invoking the binder. Here
is an example of the output generated by this switch:

    ada (spec)
    interfaces (spec)
    system (spec)
    system.case_util (spec)
    system.case_util (body)
    system.concat_2 (spec)
    system.concat_2 (body)
    system.concat_3 (spec)
    system.concat_3 (body)
    system.htable (spec)
    system.parameters (spec)
    system.parameters (body)
    system.crtl (spec)
    interfaces.c_streams (spec)
    interfaces.c_streams (body)
    system.restrictions (spec)
    system.restrictions (body)
    system.standard_library (spec)
    system.exceptions (spec)
    system.exceptions (body)
    system.storage_elements (spec)
    system.storage_elements (body)
    system.secondary_stack (spec)
    system.stack_checking (spec)
    system.stack_checking (body)
    system.string_hash (spec)
    system.string_hash (body)
    system.htable (body)
    system.strings (spec)
    system.strings (body)
    system.traceback (spec)
    system.traceback (body)
    system.traceback_entries (spec)
    system.traceback_entries (body)
    ada.exceptions (spec)
    ada.exceptions.last_chance_handler (spec)
    system.soft_links (spec)
    system.soft_links (body)
    ada.exceptions.last_chance_handler (body)
    system.secondary_stack (body)
    system.exception_table (spec)
    system.exception_table (body)
    ada.io_exceptions (spec)
    ada.tags (spec)
    ada.streams (spec)
    interfaces.c (spec)
    interfaces.c (body)
    system.finalization_root (spec)
    system.finalization_root (body)
    system.memory (spec)
    system.memory (body)
    system.standard_library (body)
    system.os_lib (spec)
    system.os_lib (body)
    system.unsigned_types (spec)
    system.stream_attributes (spec)
    system.stream_attributes (body)
    system.finalization_implementation (spec)
    system.finalization_implementation (body)
    ada.finalization (spec)
    ada.finalization (body)
    ada.finalization.list_controller (spec)
    ada.finalization.list_controller (body)
    system.file_control_block (spec)
    system.file_io (spec)
    system.file_io (body)
    system.val_uns (spec)
    system.val_util (spec)
    system.val_util (body)
    system.val_uns (body)
    system.wch_con (spec)
    system.wch_con (body)
    system.wch_cnv (spec)
    system.wch_jis (spec)
    system.wch_jis (body)
    system.wch_cnv (body)
    system.wch_stw (spec)
    system.wch_stw (body)
    ada.tags (body)
    ada.exceptions (body)
    ada.text_io (spec)
    ada.text_io (body)
    text_io (spec)
    gdbstr (body)


File: gnat_ugn.info,  Node: Inline Assembler,  Next: GNU Free Documentation License,  Prev: Elaboration Order Handling in GNAT,  Up: Top

12 Inline Assembler
*******************

If you need to write low-level software that interacts directly with
the hardware, Ada provides two ways to incorporate assembly language
code into your program.  First, you can import and invoke external
routines written in assembly language, an Ada feature fully supported
by GNAT.  However, for small sections of code it may be simpler or more
efficient to include assembly language statements directly in your Ada
source program, using the facilities of the implementation-defined
package `System.Machine_Code', which incorporates the gcc Inline
Assembler.  The Inline Assembler approach offers a number of advantages,
including the following:

   * No need to use non-Ada tools

   * Consistent interface over different targets

   * Automatic usage of the proper calling conventions

   * Access to Ada constants and variables

   * Definition of intrinsic routines

   * Possibility of inlining a subprogram comprising assembler code

   * Code optimizer can take Inline Assembler code into account

This appendix presents a series of examples to show you how to use the
Inline Assembler.  Although it focuses on the Intel x86, the general
approach applies also to other processors.  It is assumed that you are
familiar with Ada and with assembly language programming.

* Menu:

* Basic Assembler Syntax::
* A Simple Example of Inline Assembler::
* Output Variables in Inline Assembler::
* Input Variables in Inline Assembler::
* Inlining Inline Assembler Code::
* Other Asm Functionality::


File: gnat_ugn.info,  Node: Basic Assembler Syntax,  Next: A Simple Example of Inline Assembler,  Up: Inline Assembler

12.1 Basic Assembler Syntax
===========================

The assembler used by GNAT and gcc is based not on the Intel assembly
language, but rather on a language that descends from the AT&T Unix
assembler `as' (and which is often referred to as 'AT&T syntax').  The
following table summarizes the main features of `as' syntax and points
out the differences from the Intel conventions.  See the gcc `as' and
`gas' (an `as' macro pre-processor) documentation for further
information.

    `Register names' 
        gcc / `as': Prefix with '%'; for example `%eax' 
        Intel: No extra punctuation; for example `eax' 

    `Immediate operand' 
        gcc / `as': Prefix with '$'; for example `$4' 
        Intel: No extra punctuation; for example `4' 

    `Address' 
        gcc / `as': Prefix with '$'; for example `$loc' 
        Intel: No extra punctuation; for example `loc' 

    `Memory contents' 
        gcc / `as': No extra punctuation; for example `loc' 
        Intel: Square brackets; for example `[loc]' 

    `Register contents' 
        gcc / `as': Parentheses; for example `(%eax)' 
        Intel: Square brackets; for example `[eax]' 

    `Hexadecimal numbers' 
        gcc / `as': Leading '0x' (C language syntax); for example `0xA0' 
        Intel: Trailing 'h'; for example `A0h' 

    `Operand size' 
        gcc / `as': Explicit in op code; for example `movw' to move a 16-bit word 
        Intel: Implicit, deduced by assembler; for example `mov' 

    `Instruction repetition' 
        gcc / `as': Split into two lines; for example 
            `rep' 
            `stosl' 
        Intel: Keep on one line; for example `rep stosl' 

    `Order of operands' 
        gcc / `as': Source first; for example `movw $4, %eax' 
        Intel: Destination first; for example `mov eax, 4' 


File: gnat_ugn.info,  Node: A Simple Example of Inline Assembler,  Next: Output Variables in Inline Assembler,  Prev: Basic Assembler Syntax,  Up: Inline Assembler

12.2 A Simple Example of Inline Assembler
=========================================

The following example will generate a single assembly language
statement, `nop', which does nothing.  Despite its lack of run-time
effect, the example will be useful in illustrating the basics of the
Inline Assembler facility.

         with System.Machine_Code; use System.Machine_Code;
         procedure Nothing is
         begin
            Asm ("nop");
         end Nothing;

`Asm' is a procedure declared in package `System.Machine_Code'; here it
takes one parameter, a `template string' that must be a static
expression and that will form the generated instruction.  `Asm' may be
regarded as a compile-time procedure that parses the template string
and additional parameters (none here), from which it generates a
sequence of assembly language instructions.

The examples in this chapter will illustrate several of the forms for
invoking `Asm'; a complete specification of the syntax is found in the
`Machine_Code_Insertions' section of the `GNAT Reference Manual'.

Under the standard GNAT conventions, the `Nothing' procedure should be
in a file named `nothing.adb'.  You can build the executable in the
usual way:

         $ gnatmake nothing

However, the interesting aspect of this example is not its run-time
behavior but rather the generated assembly code.  To see this output,
invoke the compiler as follows:

         $  gcc -c -S -fomit-frame-pointer -gnatp nothing.adb

where the options are:

   *
    `-c'
          compile only (no bind or link)

   *
    `-S'
          generate assembler listing

   *
    `-fomit-frame-pointer'
          do not set up separate stack frames

   *
    `-gnatp'
          do not add runtime checks

This gives a human-readable assembler version of the code. The resulting
file will have the same name as the Ada source file, but with a `.s'
extension. In our example, the file `nothing.s' has the following
contents:

         .file "nothing.adb"
         gcc2_compiled.:
         ___gnu_compiled_ada:
         .text
            .align 4
         .globl __ada_nothing
         __ada_nothing:
         #APP
            nop
         #NO_APP
            jmp L1
            .align 2,0x90
         L1:
            ret

The assembly code you included is clearly indicated by the compiler,
between the `#APP' and `#NO_APP' delimiters. The character before the
'APP' and 'NOAPP' can differ on different targets. For example,
GNU/Linux uses '#APP' while on NT you will see '/APP'.

If you make a mistake in your assembler code (such as using the wrong
size modifier, or using a wrong operand for the instruction) GNAT will
report this error in a temporary file, which will be deleted when the
compilation is finished.  Generating an assembler file will help in
such cases, since you can assemble this file separately using the `as'
assembler that comes with gcc.

Assembling the file using the command

         $ as nothing.s

will give you error messages whose lines correspond to the assembler
input file, so you can easily find and correct any mistakes you made.
If there are no errors, `as' will generate an object file `nothing.out'.


File: gnat_ugn.info,  Node: Output Variables in Inline Assembler,  Next: Input Variables in Inline Assembler,  Prev: A Simple Example of Inline Assembler,  Up: Inline Assembler

12.3 Output Variables in Inline Assembler
=========================================

The examples in this section, showing how to access the processor flags,
illustrate how to specify the destination operands for assembly language
statements.

         with Interfaces; use Interfaces;
         with Ada.Text_IO; use Ada.Text_IO;
         with System.Machine_Code; use System.Machine_Code;
         procedure Get_Flags is
            Flags : Unsigned_32;
            use ASCII;
         begin
            Asm ("pushfl"          & LF & HT & -- push flags on stack
                 "popl %%eax"      & LF & HT & -- load eax with flags
                 "movl %%eax, %0",             -- store flags in variable
                 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
            Put_Line ("Flags register:" & Flags'Img);
         end Get_Flags;

In order to have a nicely aligned assembly listing, we have separated
multiple assembler statements in the Asm template string with linefeed
(ASCII.LF) and horizontal tab (ASCII.HT) characters.  The resulting
section of the assembly output file is:

         #APP
            pushfl
            popl %eax
            movl %eax, -40(%ebp)
         #NO_APP

It would have been legal to write the Asm invocation as:

         Asm ("pushfl popl %%eax movl %%eax, %0")

but in the generated assembler file, this would come out as:

         #APP
            pushfl popl %eax movl %eax, -40(%ebp)
         #NO_APP

which is not so convenient for the human reader.

We use Ada comments at the end of each line to explain what the
assembler instructions actually do.  This is a useful convention.

When writing Inline Assembler instructions, you need to precede each
register and variable name with a percent sign.  Since the assembler
already requires a percent sign at the beginning of a register name,
you need two consecutive percent signs for such names in the Asm
template string, thus `%%eax'.  In the generated assembly code, one of
the percent signs will be stripped off.

Names such as `%0', `%1', `%2', etc., denote input or output variables:
operands you later define using `Input' or `Output' parameters to `Asm'.
An output variable is illustrated in the third statement in the Asm
template string:

         movl %%eax, %0

The intent is to store the contents of the eax register in a variable
that can be accessed in Ada.  Simply writing `movl %%eax, Flags' would
not necessarily work, since the compiler might optimize by using a
register to hold Flags, and the expansion of the `movl' instruction
would not be aware of this optimization.  The solution is not to store
the result directly but rather to advise the compiler to choose the
correct operand form; that is the purpose of the `%0' output variable.

Information about the output variable is supplied in the `Outputs'
parameter to `Asm':

         Outputs => Unsigned_32'Asm_Output ("=g", Flags));

The output is defined by the `Asm_Output' attribute of the target type;
the general format is

         Type'Asm_Output (constraint_string, variable_name)

The constraint string directs the compiler how to store/access the
associated variable.  In the example

         Unsigned_32'Asm_Output ("=m", Flags);

the `"m"' (memory) constraint tells the compiler that the variable
`Flags' should be stored in a memory variable, thus preventing the
optimizer from keeping it in a register.  In contrast,

         Unsigned_32'Asm_Output ("=r", Flags);

uses the `"r"' (register) constraint, telling the compiler to store the
variable in a register.

If the constraint is preceded by the equal character '=', it tells the
compiler that the variable will be used to store data into it.

In the `Get_Flags' example, we used the `"g"' (global) constraint,
allowing the optimizer to choose whatever it deems best.

There are a fairly large number of constraints, but the ones that are
most useful (for the Intel x86 processor) are the following:

      `='        output constraint
     `g'        global (i.e., can be stored anywhere)
     `m'        in memory
     `I'        a constant
     `a'        use eax
     `b'        use ebx
     `c'        use ecx
     `d'        use edx
     `S'        use esi
     `D'        use edi
     `r'        use one of eax, ebx, ecx or edx
     `q'        use one of eax, ebx, ecx, edx, esi or edi


The full set of constraints is described in the gcc and `as'
documentation; note that it is possible to combine certain constraints
in one constraint string.

You specify the association of an output variable with an assembler
operand through the `%`n'' notation, where `n' is a non-negative
integer.  Thus in

         Asm ("pushfl"          & LF & HT & -- push flags on stack
              "popl %%eax"      & LF & HT & -- load eax with flags
              "movl %%eax, %0",             -- store flags in variable
              Outputs => Unsigned_32'Asm_Output ("=g", Flags));

`%0' will be replaced in the expanded code by the appropriate operand,
whatever the compiler decided for the `Flags' variable.

In general, you may have any number of output variables:

   * Count the operands starting at 0; thus `%0', `%1', etc.

   * Specify the `Outputs' parameter as a parenthesized comma-separated
     list of `Asm_Output' attributes

For example:

         Asm ("movl %%eax, %0" & LF & HT &
              "movl %%ebx, %1" & LF & HT &
              "movl %%ecx, %2",
              Outputs => (Unsigned_32'Asm_Output ("=g", Var_A),   --  %0 = Var_A
                          Unsigned_32'Asm_Output ("=g", Var_B),   --  %1 = Var_B
                          Unsigned_32'Asm_Output ("=g", Var_C))); --  %2 = Var_C

where `Var_A', `Var_B', and `Var_C' are variables in the Ada program.

As a variation on the `Get_Flags' example, we can use the constraints
string to direct the compiler to store the eax register into the `Flags'
variable, instead of including the store instruction explicitly in the
`Asm' template string:

         with Interfaces; use Interfaces;
         with Ada.Text_IO; use Ada.Text_IO;
         with System.Machine_Code; use System.Machine_Code;
         procedure Get_Flags_2 is
            Flags : Unsigned_32;
            use ASCII;
         begin
            Asm ("pushfl"      & LF & HT & -- push flags on stack
                 "popl %%eax",             -- save flags in eax
                 Outputs => Unsigned_32'Asm_Output ("=a", Flags));
            Put_Line ("Flags register:" & Flags'Img);
         end Get_Flags_2;

The `"a"' constraint tells the compiler that the `Flags' variable will
come from the eax register. Here is the resulting code:

         #APP
            pushfl
            popl %eax
         #NO_APP
            movl %eax,-40(%ebp)

The compiler generated the store of eax into Flags after expanding the
assembler code.

Actually, there was no need to pop the flags into the eax register;
more simply, we could just pop the flags directly into the program
variable:

         with Interfaces; use Interfaces;
         with Ada.Text_IO; use Ada.Text_IO;
         with System.Machine_Code; use System.Machine_Code;
         procedure Get_Flags_3 is
            Flags : Unsigned_32;
            use ASCII;
         begin
            Asm ("pushfl"  & LF & HT & -- push flags on stack
                 "pop %0",             -- save flags in Flags
                 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
            Put_Line ("Flags register:" & Flags'Img);
         end Get_Flags_3;


File: gnat_ugn.info,  Node: Input Variables in Inline Assembler,  Next: Inlining Inline Assembler Code,  Prev: Output Variables in Inline Assembler,  Up: Inline Assembler

12.4 Input Variables in Inline Assembler
========================================

The example in this section illustrates how to specify the source
operands for assembly language statements.  The program simply
increments its input value by 1:

         with Interfaces; use Interfaces;
         with Ada.Text_IO; use Ada.Text_IO;
         with System.Machine_Code; use System.Machine_Code;
         procedure Increment is

            function Incr (Value : Unsigned_32) return Unsigned_32 is
               Result : Unsigned_32;
            begin
               Asm ("incl %0",
                    Outputs => Unsigned_32'Asm_Output ("=a", Result),
                    Inputs  => Unsigned_32'Asm_Input ("a", Value));
               return Result;
            end Incr;

            Value : Unsigned_32;

         begin
            Value := 5;
            Put_Line ("Value before is" & Value'Img);
            Value := Incr (Value);
           Put_Line ("Value after is" & Value'Img);
         end Increment;

The `Outputs' parameter to `Asm' specifies that the result will be in
the eax register and that it is to be stored in the `Result' variable.

The `Inputs' parameter looks much like the `Outputs' parameter, but
with an `Asm_Input' attribute.  The `"="' constraint, indicating an
output value, is not present.

You can have multiple input variables, in the same way that you can
have more than one output variable.

The parameter count (%0, %1) etc, still starts at the first output
statement, and continues with the input statements.

Just as the `Outputs' parameter causes the register to be stored into
the target variable after execution of the assembler statements, so
does the `Inputs' parameter cause its variable to be loaded into the
register before execution of the assembler statements.

Thus the effect of the `Asm' invocation is:

   * load the 32-bit value of `Value' into eax

   * execute the `incl %eax' instruction

   * store the contents of eax into the `Result' variable

The resulting assembler file (with `-O2' optimization) contains:

         _increment__incr.1:
            subl $4,%esp
            movl 8(%esp),%eax
         #APP
            incl %eax
         #NO_APP
            movl %eax,%edx
            movl %ecx,(%esp)
            addl $4,%esp
            ret


File: gnat_ugn.info,  Node: Inlining Inline Assembler Code,  Next: Other Asm Functionality,  Prev: Input Variables in Inline Assembler,  Up: Inline Assembler

12.5 Inlining Inline Assembler Code
===================================

For a short subprogram such as the `Incr' function in the previous
section, the overhead of the call and return (creating / deleting the
stack frame) can be significant, compared to the amount of code in the
subprogram body.  A solution is to apply Ada's `Inline' pragma to the
subprogram, which directs the compiler to expand invocations of the
subprogram at the point(s) of call, instead of setting up a stack frame
for out-of-line calls.  Here is the resulting program:

         with Interfaces; use Interfaces;
         with Ada.Text_IO; use Ada.Text_IO;
         with System.Machine_Code; use System.Machine_Code;
         procedure Increment_2 is

            function Incr (Value : Unsigned_32) return Unsigned_32 is
               Result : Unsigned_32;
            begin
               Asm ("incl %0",
                    Outputs => Unsigned_32'Asm_Output ("=a", Result),
                    Inputs  => Unsigned_32'Asm_Input ("a", Value));
               return Result;
            end Incr;
            pragma Inline (Increment);

            Value : Unsigned_32;

         begin
            Value := 5;
            Put_Line ("Value before is" & Value'Img);
            Value := Increment (Value);
            Put_Line ("Value after is" & Value'Img);
         end Increment_2;

Compile the program with both optimization (`-O2') and inlining
(`-gnatn') enabled.

The `Incr' function is still compiled as usual, but at the point in
`Increment' where our function used to be called:

         pushl %edi
         call _increment__incr.1

the code for the function body directly appears:

         movl %esi,%eax
         #APP
            incl %eax
         #NO_APP
            movl %eax,%edx

thus saving the overhead of stack frame setup and an out-of-line call.


File: gnat_ugn.info,  Node: Other Asm Functionality,  Prev: Inlining Inline Assembler Code,  Up: Inline Assembler

12.6 Other `Asm' Functionality
==============================

This section describes two important parameters to the `Asm' procedure:
`Clobber', which identifies register usage; and `Volatile', which
inhibits unwanted optimizations.

* Menu:

* The Clobber Parameter::
* The Volatile Parameter::


File: gnat_ugn.info,  Node: The Clobber Parameter,  Next: The Volatile Parameter,  Up: Other Asm Functionality

12.6.1 The `Clobber' Parameter
------------------------------

One of the dangers of intermixing assembly language and a compiled
language such as Ada is that the compiler needs to be aware of which
registers are being used by the assembly code.  In some cases, such as
the earlier examples, the constraint string is sufficient to indicate
register usage (e.g., `"a"' for the eax register).  But more generally,
the compiler needs an explicit identification of the registers that are
used by the Inline Assembly statements.

Using a register that the compiler doesn't know about could be a side
effect of an instruction (like `mull' storing its result in both eax
and edx).  It can also arise from explicit register usage in your
assembly code; for example:

         Asm ("movl %0, %%ebx" & LF & HT &
              "movl %%ebx, %1",
              Outputs => Unsigned_32'Asm_Output ("=g", Var_Out),
              Inputs  => Unsigned_32'Asm_Input  ("g", Var_In));

where the compiler (since it does not analyze the `Asm' template string)
does not know you are using the ebx register.

In such cases you need to supply the `Clobber' parameter to `Asm', to
identify the registers that will be used by your assembly code:

         Asm ("movl %0, %%ebx" & LF & HT &
              "movl %%ebx, %1",
              Outputs => Unsigned_32'Asm_Output ("=g", Var_Out),
              Inputs  => Unsigned_32'Asm_Input  ("g", Var_In),
              Clobber => "ebx");

The Clobber parameter is a static string expression specifying the
register(s) you are using.  Note that register names are `not' prefixed
by a percent sign. Also, if more than one register is used then their
names are separated by commas; e.g., `"eax, ebx"'

The `Clobber' parameter has several additional uses:

   * Use 'register' name `cc' to indicate that flags might have changed

   * Use 'register' name `memory' if you changed a memory location


File: gnat_ugn.info,  Node: The Volatile Parameter,  Prev: The Clobber Parameter,  Up: Other Asm Functionality

12.6.2 The `Volatile' Parameter
-------------------------------

Compiler optimizations in the presence of Inline Assembler may
sometimes have unwanted effects.  For example, when an `Asm' invocation
with an input variable is inside a loop, the compiler might move the
loading of the input variable outside the loop, regarding it as a
one-time initialization.

If this effect is not desired, you can disable such optimizations by
setting the `Volatile' parameter to `True'; for example:

         Asm ("movl %0, %%ebx" & LF & HT &
              "movl %%ebx, %1",
              Outputs  => Unsigned_32'Asm_Output ("=g", Var_Out),
              Inputs   => Unsigned_32'Asm_Input  ("g", Var_In),
              Clobber  => "ebx",
              Volatile => True);

By default, `Volatile' is set to `False' unless there is no `Outputs'
parameter.

Although setting `Volatile' to `True' prevents unwanted optimizations,
it will also disable other optimizations that might be important for
efficiency. In general, you should set `Volatile' to `True' only if the
compiler's optimizations have created problems.


File: gnat_ugn.info,  Node: GNU Free Documentation License,  Next: Index,  Prev: Inline Assembler,  Up: Top

13 GNU Free Documentation License
*********************************

Version 1.3, 3 November 2008

Copyright  2000, 2001, 2002, 2007, 2008  Free Software Foundation, Inc
<http://fsf.org/>

Everyone is permitted to copy and distribute verbatim copies of this
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copying of the copies you make or distribute.  However, you may accept
compensation in exchange for copies.  If you distribute a large enough
number of copies you must also follow the conditions in section 3.

You may also lend copies, under the same conditions stated above, and
you may publicly display copies.

`3. COPYING IN QUANTITY'

If you publish printed copies (or copies in media that commonly have
printed covers) of the Document, numbering more than 100, and the
Document's license notice requires Cover Texts, you must enclose the
copies in covers that carry, clearly and legibly, all these Cover
Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on
the back cover.  Both covers must also clearly and legibly identify you
as the publisher of these copies.  The front cover must present the
full title with all words of the title equally prominent and visible.
You may add other material on the covers in addition.  Copying with
changes limited to the covers, as long as they preserve the title of
the Document and satisfy these conditions, can be treated as verbatim
copying in other respects.

If the required texts for either cover are too voluminous to fit
legibly, you should put the first ones listed (as many as fit
reasonably) on the actual cover, and continue the rest onto adjacent
pages.

If you publish or distribute Opaque copies of the Document numbering
more than 100, you must either include a machine-readable Transparent
copy along with each Opaque copy, or state in or with each Opaque copy
a computer-network location from which the general network-using public
has access to download using public-standard network protocols a
complete Transparent copy of the Document, free of added material.  If
you use the latter option, you must take reasonably prudent steps, when
you begin distribution of Opaque copies in quantity, to ensure that
this Transparent copy will remain thus accessible at the stated
location until at least one year after the last time you distribute an
Opaque copy (directly or through your agents or retailers) of that
edition to the public.

It is requested, but not required, that you contact the authors of the
Document well before redistributing any large number of copies, to give
them a chance to provide you with an updated version of the Document.

`4. MODIFICATIONS'

You may copy and distribute a Modified Version of the Document under
the conditions of sections 2 and 3 above, provided that you release the
Modified Version under precisely this License, with the Modified
Version filling the role of the Document, thus licensing distribution
and modification of the Modified Version to whoever possesses a copy of
it.  In addition, you must do these things in the Modified Version:

  A. Use in the Title Page (and on the covers, if any) a title distinct
     from that of the Document, and from those of previous versions
     (which should, if there were any, be listed in the History section
     of the Document).  You may use the same title as a previous version
     if the original publisher of that version gives permission.

  B. List on the Title Page, as authors, one or more persons or entities
     responsible for authorship of the modifications in the Modified
     Version, together with at least five of the principal authors of
     the Document (all of its principal authors, if it has fewer than
     five), unless they release you from this requirement.

  C. State on the Title page the name of the publisher of the Modified
     Version, as the publisher.

  D. Preserve all the copyright notices of the Document.

  E. Add an appropriate copyright notice for your modifications
     adjacent to the other copyright notices.

  F. Include, immediately after the copyright notices, a license notice
     giving the public permission to use the Modified Version under the
     terms of this License, in the form shown in the Addendum below.

  G. Preserve in that license notice the full lists of Invariant
     Sections and required Cover Texts given in the Document's license
     notice.

  H. Include an unaltered copy of this License.

  I. Preserve the section Entitled "History", Preserve its Title, and
     add to it an item stating at least the title, year, new authors,
     and publisher of the Modified Version as given on the Title Page.
     If there is no section Entitled "History" in the Document, create
     one stating the title, year, authors, and publisher of the
     Document as given on its Title Page, then add an item describing
     the Modified Version as stated in the previous sentence.

  J. Preserve the network location, if any, given in the Document for
     public access to a Transparent copy of the Document, and likewise
     the network locations given in the Document for previous versions
     it was based on.  These may be placed in the "History" section.
     You may omit a network location for a work that was published at
     least four years before the Document itself, or if the original
     publisher of the version it refers to gives permission.

  K. For any section Entitled "Acknowledgements" or "Dedications",
     Preserve the Title of the section, and preserve in the section all
     the substance and tone of each of the contributor acknowledgements
     and/or dedications given therein.

  L. Preserve all the Invariant Sections of the Document, unaltered in
     their text and in their titles.  Section numbers or the equivalent
     are not considered part of the section titles.

  M. Delete any section Entitled "Endorsements".  Such a section may
     not be included in the Modified Version.

  N. Do not retitle any existing section to be Entitled "Endorsements"
     or to conflict in title with any Invariant Section.

  O. Preserve any Warranty Disclaimers.

If the Modified Version includes new front-matter sections or
appendices that qualify as Secondary Sections and contain no material
copied from the Document, you may at your option designate some or all
of these sections as invariant.  To do this, add their titles to the
list of Invariant Sections in the Modified Version's license notice.
These titles must be distinct from any other section titles.

You may add a section Entitled "Endorsements", provided it contains
nothing but endorsements of your Modified Version by various
parties--for example, statements of peer review or that the text has
been approved by an organization as the authoritative definition of a
standard.

You may add a passage of up to five words as a Front-Cover Text, and a
passage of up to 25 words as a Back-Cover Text, to the end of the list
of Cover Texts in the Modified Version.  Only one passage of
Front-Cover Text and one of Back-Cover Text may be added by (or through
arrangements made by) any one entity.  If the Document already includes
a cover text for the same cover, previously added by you or by
arrangement made by the same entity you are acting on behalf of, you
may not add another; but you may replace the old one, on explicit
permission from the previous publisher that added the old one.

The author(s) and publisher(s) of the Document do not by this License
give permission to use their names for publicity for or to assert or
imply endorsement of any Modified Version.

`5. COMBINING DOCUMENTS'

You may combine the Document with other documents released under this
License, under the terms defined in section 4 above for modified
versions, provided that you include in the combination all of the
Invariant Sections of all of the original documents, unmodified, and
list them all as Invariant Sections of your combined work in its
license notice, and that you preserve all their Warranty Disclaimers.

The combined work need only contain one copy of this License, and
multiple identical Invariant Sections may be replaced with a single
copy.  If there are multiple Invariant Sections with the same name but
different contents, make the title of each such section unique by
adding at the end of it, in parentheses, the name of the original
author or publisher of that section if known, or else a unique number.
Make the same adjustment to the section titles in the list of Invariant
Sections in the license notice of the combined work.

In the combination, you must combine any sections Entitled "History" in
the various original documents, forming one section Entitled "History";
likewise combine any sections Entitled "Acknowledgements", and any
sections Entitled "Dedications".  You must delete all sections Entitled
"Endorsements".

`6. COLLECTIONS OF DOCUMENTS'

You may make a collection consisting of the Document and other documents
released under this License, and replace the individual copies of this
License in the various documents with a single copy that is included in
the collection, provided that you follow the rules of this License for
verbatim copying of each of the documents in all other respects.

You may extract a single document from such a collection, and distribute
it individually under this License, provided you insert a copy of this
License into the extracted document, and follow this License in all
other respects regarding verbatim copying of that document.

`7. AGGREGATION WITH INDEPENDENT WORKS'

A compilation of the Document or its derivatives with other separate
and independent documents or works, in or on a volume of a storage or
distribution medium, is called an "aggregate" if the copyright
resulting from the compilation is not used to limit the legal rights of
the compilation's users beyond what the individual works permit.  When
the Document is included in an aggregate, this License does not apply
to the other works in the aggregate which are not themselves derivative
works of the Document.

If the Cover Text requirement of section 3 is applicable to these
copies of the Document, then if the Document is less than one half of
the entire aggregate, the Document's Cover Texts may be placed on
covers that bracket the Document within the aggregate, or the
electronic equivalent of covers if the Document is in electronic form.
Otherwise they must appear on printed covers that bracket the whole
aggregate.

`8. TRANSLATION'

Translation is considered a kind of modification, so you may distribute
translations of the Document under the terms of section 4.  Replacing
Invariant Sections with translations requires special permission from
their copyright holders, but you may include translations of some or
all Invariant Sections in addition to the original versions of these
Invariant Sections.  You may include a translation of this License, and
all the license notices in the Document, and any Warranty Disclaimers,
provided that you also include the original English version of this
License and the original versions of those notices and disclaimers.  In
case of a disagreement between the translation and the original version
of this License or a notice or disclaimer, the original version will
prevail.

If a section in the Document is Entitled "Acknowledgements",
"Dedications", or "History", the requirement (section 4) to Preserve
its Title (section 1) will typically require changing the actual title.

`9. TERMINATION'

You may not copy, modify, sublicense, or distribute the Document except
as expressly provided under this License.  Any attempt otherwise to
copy, modify, sublicense, or distribute it is void, and will
automatically terminate your rights under this License.

However, if you cease all violation of this License, then your license
from a particular copyright holder is reinstated (a) provisionally,
unless and until the copyright holder explicitly and finally terminates
your license, and (b) permanently, if the copyright holder fails to
notify you of the violation by some reasonable means prior to 60 days
after the cessation.

Moreover, your license from a particular copyright holder is reinstated
permanently if the copyright holder notifies you of the violation by
some reasonable means, this is the first time you have received notice
of violation of this License (for any work) from that copyright holder,
and you cure the violation prior to 30 days after your receipt of the
notice.

Termination of your rights under this section does not terminate the
licenses of parties who have received copies or rights from you under
this License.  If your rights have been terminated and not permanently
reinstated, receipt of a copy of some or all of the same material does
not give you any rights to use it.

`10. FUTURE REVISIONS OF THIS LICENSE'

The Free Software Foundation may publish new, revised versions of the
GNU Free Documentation License from time to time.  Such new versions
will be similar in spirit to the present version, but may differ in
detail to address new problems or concerns.  See
<http://www.gnu.org/copyleft/>.

Each version of the License is given a distinguishing version number.
If the Document specifies that a particular numbered version of this
License "or any later version" applies to it, you have the option of
following the terms and conditions either of that specified version or
of any later version that has been published (not as a draft) by the
Free Software Foundation.  If the Document does not specify a version
number of this License, you may choose any version ever published (not
as a draft) by the Free Software Foundation.  If the Document specifies
that a proxy can decide which future versions of this License can be
used, that proxy's public statement of acceptance of a version
permanently authorizes you to choose that version for the Document.

`11. RELICENSING'

"Massive Multiauthor Collaboration Site" (or "MMC Site") means any
World Wide Web server that publishes copyrightable works and also
provides prominent facilities for anybody to edit those works.  A
public wiki that anybody can edit is an example of such a server.  A
"Massive Multiauthor Collaboration" (or "MMC") contained in the site
means any set of copyrightable works thus published on the MMC site.

"CC-BY-SA" means the Creative Commons Attribution-Share Alike 3.0
license published by Creative Commons Corporation, a not-for-profit
corporation with a principal place of business in San Francisco,
California, as well as future copyleft versions of that license
published by that same organization.

"Incorporate" means to publish or republish a Document, in whole or in
part, as part of another Document.

An MMC is "eligible for relicensing" if it is licensed under this
License, and if all works that were first published under this License
somewhere other than this MMC, and subsequently incorporated in whole
or in part into the MMC, (1) had no cover texts or invariant sections,
and (2) were thus incorporated prior to November 1, 2008.

The operator of an MMC Site may republish an MMC contained in the site
under CC-BY-SA on the same site at any time before August 1, 2009,
provided the MMC is eligible for relicensing.

`ADDENDUM: How to use this License for your documents'

To use this License in a document you have written, include a copy of
the License in the document and put the following copyright and license
notices just after the title page:

     Copyright © YEAR  YOUR NAME.  Permission is granted to copy,
     distribute and/or modify this document under the terms of the GNU
     Free Documentation License, Version 1.3 or any later version
     published by the Free Software Foundation; with no Invariant
     Sections, no Front-Cover Texts, and no Back-Cover Texts.  A copy
     of the license is included in the section entitled "GNU Free
     Documentation License".

If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts,
replace the "with ... Texts." line with this:

     with the Invariant Sections being LIST THEIR TITLES, with the
     Front-Cover Texts being LIST, and with the Back-Cover Texts being
     LIST.

If you have Invariant Sections without Cover Texts, or some other
combination of the three, merge those two alternatives to suit the
situation.

If your document contains nontrivial examples of program code, we
recommend releasing these examples in parallel under your choice of
free software license, such as the GNU General Public License, to
permit their use in free software.


File: gnat_ugn.info,  Node: Index,  Prev: GNU Free Documentation License,  Up: Top

Index
*****

[index]
* Menu:

* -83 (gnathtml):                        Invoking gnathtml.  (line   16)
* -A (gnatbind):                         Switches for gnatbind.
                                                             (line   29)
* -a (gnatbind):                         Switches for gnatbind.
                                                             (line   17)
* -a (gnatdll):                          Using gnatdll.      (line   23)
* -a (gnatfind):                         gnatfind Switches.  (line   75)
* -a (gnatls):                           Switches for gnatls.
                                                             (line   16)
* -A (gnatmake):                         Switches for gnatmake.
                                                             (line  414)
* -a (gnatmake):                         Switches for gnatmake.
                                                             (line   98)
* -a (gnatxref):                         gnatxref Switches.  (line   37)
* -aI (gnatbind) <1>:                    Search Paths for gnatbind.
                                                             (line   37)
* -aI (gnatbind):                        Switches for gnatbind.
                                                             (line   26)
* -aI (gnatls):                          Switches for gnatls.
                                                             (line   41)
* -aI (gnatmake):                        Switches for gnatmake.
                                                             (line  392)
* -aIDIR (gnatfind):                     gnatfind Switches.  (line   84)
* -aIDIR (gnatxref):                     gnatxref Switches.  (line   46)
* -aL (gnatmake):                        Switches for gnatmake.
                                                             (line  397)
* -aO (gnatbind) <1>:                    Switches for gnatbind.
                                                             (line   23)
* -aO (gnatbind):                        Search Paths for gnatbind.
                                                             (line   37)
* -aO (gnatclean):                       Switches for gnatclean.
                                                             (line   82)
* -aO (gnatls):                          Switches for gnatls.
                                                             (line   41)
* -aO (gnatmake):                        Switches for gnatmake.
                                                             (line  409)
* -aODIR (gnatfind):                     gnatfind Switches.  (line   89)
* -aODIR (gnatxref):                     gnatxref Switches.  (line   51)
* -aP (any project-aware tool):          Switches Related to Project Files.
                                                             (line   48)
* -aP (gnatls):                          Switches for gnatls.
                                                             (line   45)
* -as (dlltool):                         Using gnatdll.      (line  206)
* -b (gcc):                              Alphabetical List of All Switches.
                                                             (line    6)
* -B (gcc):                              Alphabetical List of All Switches.
                                                             (line   11)
* -b (gnatbind) <1>:                     Binder Error Message Control.
                                                             (line   17)
* -b (gnatbind):                         Switches for gnatbind.
                                                             (line   32)
* -b (gnatdll):                          Using gnatdll.      (line   30)
* -B (gnatlink):                         Switches for gnatlink.
                                                             (line   58)
* -b (gnatlink):                         Switches for gnatlink.
                                                             (line   53)
* -b (gnatmake):                         Switches for gnatmake.
                                                             (line  117)
* -b (gnatprep):                         Switches for gnatprep.
                                                             (line    6)
* -bargs (gnatdll):                      Using gnatdll.      (line   34)
* -bargs (gnatmake):                     Mode Switches for gnatmake.
                                                             (line   18)
* -base-file (dlltool):                  Using gnatdll.      (line  176)
* -C (gcc):                              Switches.           (line   18)
* -c (gcc):                              Alphabetical List of All Switches.
                                                             (line   19)
* -c (gnatbind) <1>:                     Output Control.     (line    9)
* -c (gnatbind):                         Switches for gnatbind.
                                                             (line   35)
* -c (gnatchop):                         Switches for gnatchop.
                                                             (line   16)
* -c (gnatclean):                        Switches for gnatclean.
                                                             (line   26)
* -C (gnatmake):                         Switches for gnatmake.
                                                             (line  134)
* -c (gnatmake):                         Switches for gnatmake.
                                                             (line  126)
* -c (gnatname):                         Switches for gnatname.
                                                             (line   28)
* -c (gnatprep):                         Switches for gnatprep.
                                                             (line   11)
* -C (gnatprep):                         Switches for gnatprep.
                                                             (line   17)
* -C= (gnatmake):                        Switches for gnatmake.
                                                             (line  148)
* -cargs (gnatmake):                     Mode Switches for gnatmake.
                                                             (line   13)
* -cc (gnathtml):                        Invoking gnathtml.  (line   19)
* -create-missing-dirs (gnatmake):       Switches for gnatmake.
                                                             (line   59)
* -D (gnatbind):                         Switches for gnatbind.
                                                             (line   49)
* -D (gnatclean):                        Switches for gnatclean.
                                                             (line   32)
* -d (gnatdll):                          Using gnatdll.      (line   37)
* -d (gnatfind):                         gnatfind Switches.  (line  112)
* -D (gnathtml):                         Invoking gnathtml.  (line   30)
* -d (gnathtml):                         Invoking gnathtml.  (line   24)
* -d (gnatls):                           Switches for gnatls.
                                                             (line   20)
* -d (gnatmake):                         Switches for gnatmake.
                                                             (line  156)
* -D (gnatmake):                         Switches for gnatmake.
                                                             (line  166)
* -D (gnatname):                         Switches for gnatname.
                                                             (line   52)
* -d (gnatname):                         Switches for gnatname.
                                                             (line   36)
* -D (gnatprep):                         Switches for gnatprep.
                                                             (line   27)
* -d (gnatxref):                         gnatxref Switches.  (line   74)
* -def (dlltool):                        Using gnatdll.      (line  180)
* -demangle (gprof):                     Running gprof.      (line   24)
* -dllname (dlltool):                    Using gnatdll.      (line  183)
* -dnn[k|m] (gnatbind):                  Switches for gnatbind.
                                                             (line   38)
* -E (gnatbind):                         Switches for gnatbind.
                                                             (line   88)
* -e (gnatbind) <1>:                     Switches for gnatbind.
                                                             (line   72)
* -e (gnatbind):                         Output Control.     (line   15)
* -e (gnatdll):                          Using gnatdll.      (line   47)
* -e (gnatfind):                         gnatfind Switches.  (line  116)
* -e (gprof):                            Running gprof.      (line   33)
* -E (gprof):                            Running gprof.      (line   41)
* -Ea (gnatbind):                        Switches for gnatbind.
                                                             (line   75)
* -eI (gnatmake):                        Switches for gnatmake.
                                                             (line  173)
* -eL (any project-aware tool):          Switches Related to Project Files.
                                                             (line   52)
* -eL (gnatmake):                        Switches for gnatmake.
                                                             (line  179)
* -Es (gnatbind):                        Switches for gnatbind.
                                                             (line   84)
* -eS (gnatmake):                        Switches for gnatmake.
                                                             (line  194)
* -ext (gnatfind):                       gnatfind Switches.  (line  100)
* -ext (gnathtml):                       Invoking gnathtml.  (line   35)
* -ext (gnatxref):                       gnatxref Switches.  (line   62)
* -F (gnatbind):                         Switches for gnatbind.
                                                             (line   91)
* -F (gnatclean):                        Switches for gnatclean.
                                                             (line   36)
* -f (gnatfind):                         gnatfind Switches.  (line  121)
* -f (gnathtml):                         Invoking gnathtml.  (line   40)
* -f (gnatlink):                         Switches for gnatlink.
                                                             (line   16)
* -F (gnatmake):                         Switches for gnatmake.
                                                             (line  204)
* -f (gnatmake):                         Switches for gnatmake.
                                                             (line  198)
* -f (gnatname):                         Switches for gnatname.
                                                             (line   63)
* -f (gnatxref):                         gnatxref Switches.  (line   78)
* -F (gprof):                            Running gprof.      (line   55)
* -f (gprof):                            Running gprof.      (line   49)
* -fada-spec-parent (gcc):               Switches.           (line   14)
* -fcallgraph-info (gcc):                Alphabetical List of All Switches.
                                                             (line   28)
* -fdata-sections (gcc):                 Compilation options.
                                                             (line    9)
* -fdump-ada-spec (gcc):                 Switches.           (line    6)
* -fdump-ada-spec-slim (gcc):            Switches.           (line   10)
* -fdump-scos (gcc):                     Alphabetical List of All Switches.
                                                             (line   39)
* -fdump-xref (gcc):                     Alphabetical List of All Switches.
                                                             (line   45)
* -ffunction-sections (gcc):             Compilation options.
                                                             (line    9)
* -files (gnatls):                       Switches for gnatls.
                                                             (line   35)
* -flto (gcc):                           Alphabetical List of All Switches.
                                                             (line   51)
* -fno-inline (gcc) <1>:                 Alphabetical List of All Switches.
                                                             (line   70)
* -fno-inline (gcc):                     Inlining of Subprograms.
                                                             (line   76)
* -fno-inline-functions (gcc) <1>:       Inlining of Subprograms.
                                                             (line   82)
* -fno-inline-functions (gcc):           Alphabetical List of All Switches.
                                                             (line   76)
* -fno-inline-functions-called-once (gcc) <1>: Inlining of Subprograms.
                                                             (line   88)
* -fno-inline-functions-called-once (gcc): Alphabetical List of All Switches.
                                                             (line   84)
* -fno-inline-small-functions (gcc) <1>: Inlining of Subprograms.
                                                             (line   85)
* -fno-inline-small-functions (gcc):     Alphabetical List of All Switches.
                                                             (line   80)
* -fno-ivopts (gcc):                     Alphabetical List of All Switches.
                                                             (line   88)
* -fno-strict-aliasing (gcc):            Alphabetical List of All Switches.
                                                             (line   96)
* -fno-strict-overflow (gcc):            Alphabetical List of All Switches.
                                                             (line  101)
* -fprofile-arcs (gcc):                  Quick startup guide.
                                                             (line   15)
* -fprofile-arcs (gnatbind):             Quick startup guide.
                                                             (line   15)
* -fstack-check (gcc) <1>:               Alphabetical List of All Switches.
                                                             (line  110)
* -fstack-check (gcc) <2>:               Run-Time Checks.    (line  130)
* -fstack-check (gcc):                   Stack Overflow Checking.
                                                             (line    6)
* -fstack-usage:                         Static Stack Usage Analysis.
                                                             (line    6)
* -fstack-usage (gcc):                   Alphabetical List of All Switches.
                                                             (line  114)
* -ftest-coverage (gcc:                  Quick startup guide.
                                                             (line   15)
* -fverbose-asm (gcc):                   Alphabetical List of All Switches.
                                                             (line  716)
* -g (gcc) <1>:                          Debugging Optimized Code.
                                                             (line   14)
* -g (gcc):                              Alphabetical List of All Switches.
                                                             (line  119)
* -g (gnatdll):                          Using gnatdll.      (line   50)
* -g (gnatfind):                         gnatfind Switches.  (line  126)
* -g (gnatlink):                         Switches for gnatlink.
                                                             (line   24)
* -g (gnatmake):                         Switches for gnatmake.
                                                             (line  210)
* -g (gnatxref):                         gnatxref Switches.  (line   83)
* -GCC= (gnatchop):                      Switches for gnatchop.
                                                             (line   87)
* -GCC=compiler_name (gnatlink):         Switches for gnatlink.
                                                             (line   74)
* -GCC=compiler_name (gnatmake):         Switches for gnatmake.
                                                             (line   16)
* -gnat-p (gcc) <1>:                     Alphabetical List of All Switches.
                                                             (line  586)
* -gnat-p (gcc):                         Run-Time Checks.    (line   59)
* -gnat05 (gcc) <1>:                     Compiling Different Versions of Ada.
                                                             (line   47)
* -gnat05 (gcc):                         Alphabetical List of All Switches.
                                                             (line  125)
* -gnat12 (gcc) <1>:                     Alphabetical List of All Switches.
                                                             (line  128)
* -gnat12 (gcc):                         Compiling Different Versions of Ada.
                                                             (line   55)
* -gnat2005 (gcc) <1>:                   Alphabetical List of All Switches.
                                                             (line  131)
* -gnat2005 (gcc):                       Compiling Different Versions of Ada.
                                                             (line   47)
* -gnat2012 (gcc) <1>:                   Compiling Different Versions of Ada.
                                                             (line   55)
* -gnat2012 (gcc):                       Alphabetical List of All Switches.
                                                             (line  134)
* -gnat83 (gcc) <1>:                     Alphabetical List of All Switches.
                                                             (line  131)
* -gnat83 (gcc):                         Compiling Different Versions of Ada.
                                                             (line   11)
* -gnat95 (gcc) <1>:                     Alphabetical List of All Switches.
                                                             (line  140)
* -gnat95 (gcc):                         Compiling Different Versions of Ada.
                                                             (line   34)
* -gnata (gcc) <1>:                      Alphabetical List of All Switches.
                                                             (line  151)
* -gnata (gcc):                          Debugging and Assertion Control.
                                                             (line    6)
* -gnatA (gcc):                          Alphabetical List of All Switches.
                                                             (line  167)
* -gnata switch:                         Debugging - A Special Case.
                                                             (line   45)
* -gnatB (gcc):                          Alphabetical List of All Switches.
                                                             (line  174)
* -gnatb (gcc) <1>:                      Output and Error Message Control.
                                                             (line   97)
* -gnatb (gcc):                          Alphabetical List of All Switches.
                                                             (line  171)
* -GNATBIND=binder_name (gnatmake):      Switches for gnatmake.
                                                             (line   31)
* -gnatc (gcc) <1>:                      Using gcc for Semantic Checking.
                                                             (line    6)
* -gnatc (gcc):                          Alphabetical List of All Switches.
                                                             (line  178)
* -gnatC (gcc):                          Alphabetical List of All Switches.
                                                             (line  192)
* -gnatd (gcc):                          Debugging Control.  (line    7)
* -gnatD (gcc):                          Debugging Control.  (line  122)
* -gnatd (gcc):                          Alphabetical List of All Switches.
                                                             (line  200)
* -gnatD[nn] (gcc):                      Alphabetical List of All Switches.
                                                             (line  209)
* -gnatdc switch:                        GNAT Abnormal Termination or Failure to Terminate.
                                                             (line   33)
* -gnatE (gcc) <1>:                      Alphabetical List of All Switches.
                                                             (line  452)
* -gnatE (gcc):                          Run-Time Checks.    (line  123)
* -gnateA (gcc):                         Alphabetical List of All Switches.
                                                             (line  216)
* -gnatec (gcc):                         Alphabetical List of All Switches.
                                                             (line  248)
* -gnateC (gcc):                         Alphabetical List of All Switches.
                                                             (line  252)
* -gnateD (gcc):                         Integrated Preprocessing.
                                                             (line  112)
* -gnated (gcc):                         Alphabetical List of All Switches.
                                                             (line  257)
* -gnateD (gcc):                         Alphabetical List of All Switches.
                                                             (line  260)
* -gnateE (gcc):                         Alphabetical List of All Switches.
                                                             (line  264)
* -gnatef (gcc):                         Alphabetical List of All Switches.
                                                             (line  272)
* -gnateF (gcc):                         Alphabetical List of All Switches.
                                                             (line  275)
* -gnateg (gcc):                         Alphabetical List of All Switches.
                                                             (line  280)
* -gnateG (gcc):                         Alphabetical List of All Switches.
                                                             (line  287)
* -gnatei (gcc):                         Alphabetical List of All Switches.
                                                             (line  290)
* -gnateI (gcc):                         Alphabetical List of All Switches.
                                                             (line  296)
* -gnatel (gcc):                         Alphabetical List of All Switches.
                                                             (line  302)
* -gnatem (gcc) <1>:                     Alphabetical List of All Switches.
                                                             (line  316)
* -gnatem (gcc):                         Units to Sources Mapping Files.
                                                             (line    6)
* -gnateP (gcc):                         Alphabetical List of All Switches.
                                                             (line  324)
* -gnatep (gcc) <1>:                     Integrated Preprocessing.
                                                             (line   34)
* -gnatep (gcc):                         Alphabetical List of All Switches.
                                                             (line  320)
* -gnateS (gcc):                         Alphabetical List of All Switches.
                                                             (line  333)
* -gnateT (gcc):                         Alphabetical List of All Switches.
                                                             (line  340)
* -gnatet=file (gcc):                    Alphabetical List of All Switches.
                                                             (line  336)
* -gnateu (gcc):                         Alphabetical List of All Switches.
                                                             (line  434)
* -gnateV (gcc):                         Alphabetical List of All Switches.
                                                             (line  441)
* -gnateY (gcc):                         Alphabetical List of All Switches.
                                                             (line  446)
* -gnatf (gcc) <1>:                      Output and Error Message Control.
                                                             (line  123)
* -gnatf (gcc):                          Alphabetical List of All Switches.
                                                             (line  455)
* -gnatF (gcc):                          Alphabetical List of All Switches.
                                                             (line  459)
* -gnatG (gcc):                          Debugging Control.  (line   15)
* -gnatg (gcc):                          Alphabetical List of All Switches.
                                                             (line  462)
* -gnatG[nn] (gcc):                      Alphabetical List of All Switches.
                                                             (line  470)
* -gnath (gcc):                          Alphabetical List of All Switches.
                                                             (line  473)
* -gnatI (gcc):                          Alphabetical List of All Switches.
                                                             (line  481)
* -gnati (gcc) <1>:                      Character Set Control.
                                                             (line    6)
* -gnati (gcc):                          Alphabetical List of All Switches.
                                                             (line  476)
* -gnatjnn (gcc) <1>:                    Alphabetical List of All Switches.
                                                             (line  498)
* -gnatjnn (gcc):                        Output and Error Message Control.
                                                             (line  152)
* -gnatk (gcc) <1>:                      File Naming Control.
                                                             (line    6)
* -gnatk (gcc):                          Alphabetical List of All Switches.
                                                             (line  501)
* -gnatl (gcc):                          Alphabetical List of All Switches.
                                                             (line  504)
* -gnatL (gcc) <1>:                      Alphabetical List of All Switches.
                                                             (line  507)
* -gnatL (gcc):                          Debugging Control.  (line   43)
* -gnatl (gcc):                          Output and Error Message Control.
                                                             (line   35)
* -gnatL (gcc):                          Debugging Control.  (line  142)
* -gnatl=fname (gcc):                    Output and Error Message Control.
                                                             (line   82)
* -GNATLINK=linker_name (gnatmake):      Switches for gnatmake.
                                                             (line   41)
* -gnatm (gcc) <1>:                      Output and Error Message Control.
                                                             (line  103)
* -gnatm (gcc):                          Alphabetical List of All Switches.
                                                             (line  512)
* -gnatN (gcc) <1>:                      Alphabetical List of All Switches.
                                                             (line  530)
* -gnatN (gcc):                          Subprogram Inlining Control.
                                                             (line   30)
* -gnatn (gcc) <1>:                      Alphabetical List of All Switches.
                                                             (line  522)
* -gnatn (gcc):                          Subprogram Inlining Control.
                                                             (line    6)
* -gnatN switch:                         Source Dependencies.
                                                             (line   34)
* -gnatn switch:                         Source Dependencies.
                                                             (line   27)
* -gnato (gcc) <1>:                      Controlling Run-Time Checks.
                                                             (line   11)
* -gnato (gcc):                          Default Settings.   (line   17)
* -gnato0 (gcc):                         Alphabetical List of All Switches.
                                                             (line  541)
* -gnato? (gcc):                         Specifying the Desired Mode.
                                                             (line   53)
* -gnato?? (gcc) <1>:                    Specifying the Desired Mode.
                                                             (line   53)
* -gnato?? (gcc) <2>:                    Run-Time Checks.    (line   62)
* -gnato?? (gcc):                        Alphabetical List of All Switches.
                                                             (line  547)
* -gnatp (gcc):                          Alphabetical List of All Switches.
                                                             (line  581)
* -gnatP (gcc):                          Alphabetical List of All Switches.
                                                             (line  589)
* -gnatp (gcc) <1>:                      Run-Time Checks.    (line   12)
* -gnatp (gcc):                          Controlling Run-Time Checks.
                                                             (line   11)
* -gnatQ (gcc):                          Alphabetical List of All Switches.
                                                             (line  598)
* -gnatq (gcc) <1>:                      Output and Error Message Control.
                                                             (line  166)
* -gnatq (gcc):                          Alphabetical List of All Switches.
                                                             (line  595)
* -gnatQ (gcc):                          Output and Error Message Control.
                                                             (line  177)
* -gnatr (gcc) <1>:                      Debugging Control.  (line  151)
* -gnatr (gcc):                          Alphabetical List of All Switches.
                                                             (line  603)
* -gnatR (gcc) <1>:                      Alphabetical List of All Switches.
                                                             (line  606)
* -gnatR (gcc):                          Debugging Control.  (line  160)
* -gnats (gcc):                          Alphabetical List of All Switches.
                                                             (line  615)
* -gnatS (gcc):                          Debugging Control.  (line  198)
* -gnats (gcc):                          Using gcc for Syntax Checking.
                                                             (line    6)
* -gnatS (gcc):                          Alphabetical List of All Switches.
                                                             (line  618)
* -gnatT (gcc):                          Alphabetical List of All Switches.
                                                             (line  624)
* -gnatt (gcc) <1>:                      Auxiliary Output Control.
                                                             (line    6)
* -gnatt (gcc):                          Alphabetical List of All Switches.
                                                             (line  621)
* -gnatU (gcc):                          Alphabetical List of All Switches.
                                                             (line  630)
* -gnatu (gcc) <1>:                      Alphabetical List of All Switches.
                                                             (line  627)
* -gnatu (gcc):                          Auxiliary Output Control.
                                                             (line   15)
* -gnatU (gcc):                          Output and Error Message Control.
                                                             (line   91)
* -gnatv (gcc):                          Alphabetical List of All Switches.
                                                             (line  633)
* -gnatV (gcc):                          Alphabetical List of All Switches.
                                                             (line  636)
* -gnatv (gcc):                          Output and Error Message Control.
                                                             (line   18)
* -gnatVa (gcc):                         Validity Checking.  (line   50)
* -gnatVc (gcc):                         Validity Checking.  (line   56)
* -gnatVd (gcc):                         Validity Checking.  (line   62)
* -gnatVe (gcc):                         Validity Checking.  (line   79)
* -gnatVf (gcc):                         Validity Checking.  (line   92)
* -gnatVi (gcc):                         Validity Checking.  (line  106)
* -gnatVm (gcc):                         Validity Checking.  (line  112)
* -gnatVn (gcc):                         Validity Checking.  (line  123)
* -gnatVo (gcc):                         Validity Checking.  (line  133)
* -gnatVp (gcc):                         Validity Checking.  (line  145)
* -gnatVr (gcc):                         Validity Checking.  (line  158)
* -gnatVs (gcc):                         Validity Checking.  (line  164)
* -gnatVt (gcc):                         Validity Checking.  (line  171)
* -gnatw (gcc):                          Alphabetical List of All Switches.
                                                             (line  639)
* -gnatW (gcc) <1>:                      Alphabetical List of All Switches.
                                                             (line  644)
* -gnatW (gcc):                          Character Set Control.
                                                             (line   29)
* -gnatw.a (gcc):                        Warning Message Control.
                                                             (line  189)
* -gnatw.A (gcc):                        Warning Message Control.
                                                             (line  197)
* -gnatw.b (gcc):                        Warning Message Control.
                                                             (line  221)
* -gnatw.c (gcc):                        Warning Message Control.
                                                             (line  268)
* -gnatw.d (gcc):                        Warning Message Control.
                                                             (line  329)
* -gnatw.e (gcc):                        Warning Message Control.
                                                             (line  347)
* -gnatw.g (gcc):                        Warning Message Control.
                                                             (line  389)
* -gnatw.H (gcc):                        Warning Message Control.
                                                             (line  420)
* -gnatw.h (gcc):                        Warning Message Control.
                                                             (line  411)
* -gnatw.I (gcc):                        Warning Message Control.
                                                             (line  452)
* -gnatw.i (gcc):                        Warning Message Control.
                                                             (line  444)
* -gnatw.k (gcc):                        Warning Message Control.
                                                             (line  500)
* -gnatw.l (gcc):                        Warning Message Control.
                                                             (line  531)
* -gnatw.L (gcc):                        Warning Message Control.
                                                             (line  539)
* -gnatw.m (gcc):                        Warning Message Control.
                                                             (line  560)
* -gnatw.M (gcc):                        Warning Message Control.
                                                             (line  572)
* -gnatw.n (gcc):                        Warning Message Control.
                                                             (line  587)
* -gnatw.N (gcc):                        Warning Message Control.
                                                             (line  594)
* -gnatw.O (gcc):                        Warning Message Control.
                                                             (line  628)
* -gnatw.o (gcc):                        Warning Message Control.
                                                             (line  615)
* -gnatw.p (gcc):                        Warning Message Control.
                                                             (line  653)
* -gnatw.P (gcc):                        Warning Message Control.
                                                             (line  664)
* -gnatw.r (gcc):                        Warning Message Control.
                                                             (line  721)
* -gnatw.S (gcc):                        Warning Message Control.
                                                             (line  759)
* -gnatw.s (gcc):                        Warning Message Control.
                                                             (line  749)
* -gnatw.T (gcc):                        Warning Message Control.
                                                             (line  798)
* -gnatw.t (gcc):                        Warning Message Control.
                                                             (line  781)
* -gnatw.u (gcc):                        Warning Message Control.
                                                             (line  828)
* -gnatw.U (gcc):                        Warning Message Control.
                                                             (line  842)
* -gnatw.V (gcc):                        Warning Message Control.
                                                             (line  882)
* -gnatw.v (gcc):                        Warning Message Control.
                                                             (line  871)
* -gnatw.w (gcc):                        Warning Message Control.
                                                             (line  911)
* -gnatw.W (gcc):                        Warning Message Control.
                                                             (line  923)
* -gnatw.y (gcc):                        Warning Message Control.
                                                             (line  981)
* -gnatw.Y (gcc):                        Warning Message Control.
                                                             (line  992)
* -gnatw.z (gcc):                        Warning Message Control.
                                                             (line 1013)
* -gnatw.Z (gcc):                        Warning Message Control.
                                                             (line 1022)
* -gnatwa (gcc):                         Warning Message Control.
                                                             (line  134)
* -gnatwA (gcc):                         Warning Message Control.
                                                             (line  174)
* -gnatwB (gcc):                         Warning Message Control.
                                                             (line  215)
* -gnatwb (gcc):                         Warning Message Control.
                                                             (line  203)
* -gnatwc (gcc):                         Warning Message Control.
                                                             (line  236)
* -gnatwC (gcc):                         Warning Message Control.
                                                             (line  276)
* -gnatwd (gcc):                         Warning Message Control.
                                                             (line  282)
* -gnatwD (gcc):                         Warning Message Control.
                                                             (line  293)
* -gnatwe (gcc):                         Warning Message Control.
                                                             (line  336)
* -gnatwF (gcc):                         Warning Message Control.
                                                             (line  367)
* -gnatwf (gcc):                         Warning Message Control.
                                                             (line  359)
* -gnatwG (gcc):                         Warning Message Control.
                                                             (line  384)
* -gnatwg (gcc):                         Warning Message Control.
                                                             (line  375)
* -gnatwh (gcc):                         Warning Message Control.
                                                             (line  397)
* -gnatwH (gcc):                         Warning Message Control.
                                                             (line  406)
* -gnatwi (gcc):                         Warning Message Control.
                                                             (line  427)
* -gnatwI (gcc):                         Warning Message Control.
                                                             (line  438)
* -gnatwJ (gcc):                         Warning Message Control.
                                                             (line  482)
* -gnatwj (gcc):                         Warning Message Control.
                                                             (line  457)
* -gnatwk (gcc):                         Warning Message Control.
                                                             (line  487)
* -gnatwK (gcc):                         Warning Message Control.
                                                             (line  510)
* -gnatwL (gcc):                         Warning Message Control.
                                                             (line  526)
* -gnatwl (gcc):                         Warning Message Control.
                                                             (line  516)
* -gnatwm (gcc):                         Warning Message Control.
                                                             (line  947)
* -gnatwM (gcc):                         Warning Message Control.
                                                             (line  554)
* -gnatwm (gcc):                         Warning Message Control.
                                                             (line  544)
* -gnatwn (gcc):                         Warning Message Control.
                                                             (line  577)
* -gnatwO (gcc):                         Warning Message Control.
                                                             (line  608)
* -gnatwo (gcc):                         Warning Message Control.
                                                             (line  600)
* -gnatwP (gcc):                         Warning Message Control.
                                                             (line  646)
* -gnatwp (gcc):                         Warning Message Control.
                                                             (line  635)
* -gnatwq (gcc):                         Warning Message Control.
                                                             (line  670)
* -gnatwQ (gcc):                         Warning Message Control.
                                                             (line  683)
* -gnatwR (gcc):                         Warning Message Control.
                                                             (line  716)
* -gnatwr (gcc):                         Warning Message Control.
                                                             (line  689)
* -gnatws (gcc):                         Warning Message Control.
                                                             (line  734)
* -gnatwT (gcc):                         Warning Message Control.
                                                             (line  775)
* -gnatwt (gcc):                         Warning Message Control.
                                                             (line  766)
* -gnatwT (gcc):                         Warning Message Control.
                                                             (line  729)
* -gnatwu (gcc):                         Warning Message Control.
                                                             (line  803)
* -gnatwU (gcc):                         Warning Message Control.
                                                             (line  821)
* -gnatwv (gcc):                         Warning Message Control.
                                                             (line  849)
* -gnatwV (gcc):                         Warning Message Control.
                                                             (line  856)
* -gnatww (gcc):                         Warning Message Control.
                                                             (line  889)
* -gnatwW (gcc):                         Warning Message Control.
                                                             (line  898)
* -gnatwx (gcc):                         Warning Message Control.
                                                             (line  929)
* -gnatwX (gcc):                         Warning Message Control.
                                                             (line  939)
* -gnatwy (gcc):                         Warning Message Control.
                                                             (line  963)
* -gnatwY (gcc):                         Warning Message Control.
                                                             (line  975)
* -gnatwZ (gcc):                         Warning Message Control.
                                                             (line 1006)
* -gnatwz (gcc):                         Warning Message Control.
                                                             (line  998)
* -gnatx (gcc):                          Debugging Control.  (line  207)
* -gnatX (gcc) <1>:                      Compiling Different Versions of Ada.
                                                             (line   63)
* -gnatX (gcc):                          Alphabetical List of All Switches.
                                                             (line  650)
* -gnatx (gcc):                          Alphabetical List of All Switches.
                                                             (line  647)
* -gnaty (gcc) <1>:                      Alphabetical List of All Switches.
                                                             (line  653)
* -gnaty (gcc):                          Style Checking.     (line    6)
* -gnaty+ (gcc):                         Style Checking.     (line  409)
* -gnaty- (gcc):                         Style Checking.     (line  398)
* -gnaty[0-9] (gcc):                     Style Checking.     (line   25)
* -gnatya (gcc):                         Style Checking.     (line   39)
* -gnatyA (gcc):                         Style Checking.     (line   47)
* -gnatyb (gcc):                         Style Checking.     (line   54)
* -gnatyB (gcc):                         Style Checking.     (line   62)
* -gnatyC (gcc):                         Style Checking.     (line  113)
* -gnatyc (gcc):                         Style Checking.     (line   70)
* -gnatyd (gcc):                         Style Checking.     (line  119)
* -gnatye (gcc):                         Style Checking.     (line  125)
* -gnatyf (gcc):                         Style Checking.     (line  131)
* -gnatyg (gcc):                         Style Checking.     (line  137)
* -gnatyh (gcc):                         Style Checking.     (line  146)
* -gnatyI (gcc):                         Style Checking.     (line  161)
* -gnatyi (gcc):                         Style Checking.     (line  154)
* -gnatyk (gcc):                         Style Checking.     (line  167)
* -gnatyl (gcc):                         Style Checking.     (line  174)
* -gnatyLnnn (gcc):                      Style Checking.     (line  238)
* -gnatym (gcc):                         Style Checking.     (line  245)
* -gnatyMnnn (gcc):                      Style Checking.     (line  257)
* -gnatyn (gcc):                         Style Checking.     (line  266)
* -gnatyN (gcc):                         Style Checking.     (line  273)
* -gnatyO (gcc):                         Style Checking.     (line  287)
* -gnatyo (gcc):                         Style Checking.     (line  278)
* -gnatyp (gcc):                         Style Checking.     (line  298)
* -gnatyr (gcc):                         Style Checking.     (line  306)
* -gnatyS (gcc):                         Style Checking.     (line  323)
* -gnatys (gcc):                         Style Checking.     (line  314)
* -gnatyt (gcc):                         Style Checking.     (line  331)
* -gnatyu (gcc):                         Style Checking.     (line  376)
* -gnatyx (gcc):                         Style Checking.     (line  383)
* -gnatyy (gcc):                         Style Checking.     (line  390)
* -gnatz (gcc):                          Alphabetical List of All Switches.
                                                             (line  656)
* -h (gnatbind) <1>:                     Output Control.     (line   21)
* -h (gnatbind):                         Switches for gnatbind.
                                                             (line  101)
* -h (gnatclean):                        Switches for gnatclean.
                                                             (line   42)
* -h (gnatdll):                          Using gnatdll.      (line   57)
* -h (gnatls):                           Switches for gnatls.
                                                             (line   23)
* -h (gnatname):                         Switches for gnatname.
                                                             (line   74)
* -H32 (gnatbind):                       Switches for gnatbind.
                                                             (line  104)
* -H64 (gnatbind):                       Switches for gnatbind.
                                                             (line  109)
* -help (dlltool):                       Using gnatdll.      (line  192)
* -help (gnatbind):                      Switches for gnatbind.
                                                             (line   13)
* -help (gnatchop):                      Switches for gnatchop.
                                                             (line   12)
* -help (gnatclean):                     Switches for gnatclean.
                                                             (line   12)
* -help (gnatfind):                      gnatfind Switches.  (line   71)
* -help (gnatlink):                      Switches for gnatlink.
                                                             (line   12)
* -help (gnatls):                        Switches for gnatls.
                                                             (line   12)
* -help (gnatmake):                      Switches for gnatmake.
                                                             (line   12)
* -help (gnatname):                      Switches for gnatname.
                                                             (line   14)
* -help (gnatxref):                      gnatxref Switches.  (line   33)
* -I (gcc):                              Alphabetical List of All Switches.
                                                             (line  660)
* -I (gnatbind) <1>:                     Search Paths for gnatbind.
                                                             (line   37)
* -I (gnatbind):                         Switches for gnatbind.
                                                             (line  114)
* -I (gnatclean):                        Switches for gnatclean.
                                                             (line   85)
* -I (gnatdll):                          Using gnatdll.      (line   60)
* -I (gnathtml):                         Invoking gnathtml.  (line   50)
* -I (gnatls):                           Switches for gnatls.
                                                             (line   41)
* -i (gnatmake):                         Switches for gnatmake.
                                                             (line  214)
* -I (gnatmake):                         Switches for gnatmake.
                                                             (line  417)
* -I- (gcc):                             Alphabetical List of All Switches.
                                                             (line  665)
* -I- (gnatbind):                        Switches for gnatbind.
                                                             (line  117)
* -I- (gnatclean):                       Switches for gnatclean.
                                                             (line   88)
* -I- (gnatls):                          Switches for gnatls.
                                                             (line   41)
* -I- (gnatmake):                        Switches for gnatmake.
                                                             (line  420)
* -IDIR (gnatfind):                      gnatfind Switches.  (line  131)
* -IDIR (gnatxref):                      gnatxref Switches.  (line   88)
* -j (gnatmake):                         Switches for gnatmake.
                                                             (line  232)
* -k (dlltool):                          Using gnatdll.      (line  188)
* -K (gnatbind):                         Output Control.     (line   24)
* -k (gnatchop):                         Switches for gnatchop.
                                                             (line   31)
* -k (gnatdll):                          Using gnatdll.      (line   65)
* -k (gnatmake):                         Switches for gnatmake.
                                                             (line  242)
* -L (gnatbind):                         Switches for gnatbind.
                                                             (line  125)
* -l (gnatbind) <1>:                     Switches for gnatbind.
                                                             (line  122)
* -l (gnatbind):                         Output Control.     (line   29)
* -l (gnatdll):                          Using gnatdll.      (line   73)
* -l (gnathtml):                         Invoking gnathtml.  (line   46)
* -L (gnatmake):                         Switches for gnatmake.
                                                             (line  425)
* -l (gnatmake):                         Switches for gnatmake.
                                                             (line  253)
* -largs (gnatdll):                      Using gnatdll.      (line   87)
* -largs (gnatmake):                     Mode Switches for gnatmake.
                                                             (line   23)
* -LINK= (gnatlink):                     Switches for gnatlink.
                                                             (line   94)
* -m (gnatbind):                         Binder Error Message Control.
                                                             (line   21)
* -M (gnatbind) <1>:                     Binder Error Message Control.
                                                             (line   26)
* -M (gnatbind):                         Switches for gnatbind.
                                                             (line  131)
* -m (gnatbind):                         Switches for gnatbind.
                                                             (line  135)
* -M (gnatlink):                         Switches for gnatlink.
                                                             (line   66)
* -M (gnatmake):                         Switches for gnatmake.
                                                             (line  278)
* -m (gnatmake):                         Switches for gnatmake.
                                                             (line  263)
* -M= (gnatlink):                        Switches for gnatlink.
                                                             (line   70)
* -margs (gnatmake):                     Mode Switches for gnatmake.
                                                             (line   28)
* -mwindows:                             CONSOLE and WINDOWS subsystems.
                                                             (line    6)
* -n (gnatbind) <1>:                     Binding with Non-Ada Main Programs.
                                                             (line   14)
* -n (gnatbind) <2>:                     Switches for gnatbind.
                                                             (line  144)
* -n (gnatbind):                         Binding with Non-Ada Main Programs.
                                                             (line   43)
* -n (gnatclean):                        Switches for gnatclean.
                                                             (line   45)
* -n (gnatdll):                          Using gnatdll.      (line   78)
* -n (gnatlink):                         Switches for gnatlink.
                                                             (line   31)
* -n (gnatmake):                         Switches for gnatmake.
                                                             (line  293)
* -nostdinc (gcc):                       Alphabetical List of All Switches.
                                                             (line  678)
* -nostdinc (gnatbind):                  Switches for gnatbind.
                                                             (line  147)
* -nostdinc (gnatfind):                  gnatfind Switches.  (line   94)
* -nostdinc (gnatmake):                  Switches for gnatmake.
                                                             (line  431)
* -nostdinc (gnatxref):                  gnatxref Switches.  (line   56)
* -nostdlib (gcc):                       Alphabetical List of All Switches.
                                                             (line  682)
* -nostdlib (gnatbind):                  Switches for gnatbind.
                                                             (line  150)
* -nostdlib (gnatfind):                  gnatfind Switches.  (line   97)
* -nostdlib (gnatmake):                  Switches for gnatmake.
                                                             (line  434)
* -nostdlib (gnatxref):                  gnatxref Switches.  (line   59)
* -O (gcc) <1>:                          Alphabetical List of All Switches.
                                                             (line  686)
* -O (gcc):                              Optimization Levels.
                                                             (line    6)
* -o (gcc):                              Alphabetical List of All Switches.
                                                             (line  671)
* -O (gnatbind):                         Switches for gnatbind.
                                                             (line  163)
* -o (gnatbind) <1>:                     Binding with Non-Ada Main Programs.
                                                             (line   54)
* -o (gnatbind):                         Switches for gnatbind.
                                                             (line  158)
* -O (gnatbind):                         Output Control.     (line   32)
* -o (gnatbind):                         Output Control.     (line   41)
* -o (gnathtml):                         Invoking gnathtml.  (line   56)
* -o (gnatlink):                         Switches for gnatlink.
                                                             (line   47)
* -o (gnatls):                           Switches for gnatls.
                                                             (line   26)
* -o (gnatmake):                         Switches for gnatmake.
                                                             (line  300)
* -output-exp (dlltool):                 Using gnatdll.      (line  195)
* -output-lib (dlltool):                 Using gnatdll.      (line  200)
* -P (any project-aware tool):           Switches Related to Project Files.
                                                             (line    9)
* -p (gnatbind):                         Elaboration Control.
                                                             (line   10)
* -P (gnatbind):                         Switches for gnatbind.
                                                             (line  169)
* -p (gnatbind):                         Switches for gnatbind.
                                                             (line  166)
* -p (gnatchop):                         Switches for gnatchop.
                                                             (line   41)
* -P (gnatclean):                        Switches for gnatclean.
                                                             (line   50)
* -p (gnathtml):                         Invoking gnathtml.  (line   61)
* -p (gnatmake):                         Switches for gnatmake.
                                                             (line  309)
* -P (gnatmake):                         Switches for gnatmake.
                                                             (line  312)
* -P (gnatname):                         Switches for gnatname.
                                                             (line   77)
* -pass-exit-codes (gcc) <1>:            Auxiliary Output Control.
                                                             (line   20)
* -pass-exit-codes (gcc):                Alphabetical List of All Switches.
                                                             (line  701)
* -pFILE (gnatfind):                     gnatfind Switches.  (line  134)
* -pFILE (gnatxref):                     gnatxref Switches.  (line   91)
* -pg (gcc):                             Compilation for profiling.
                                                             (line    6)
* -pg (gnatlink):                        Compilation for profiling.
                                                             (line    6)
* -q (gnatchop):                         Switches for gnatchop.
                                                             (line   48)
* -q (gnatclean):                        Switches for gnatclean.
                                                             (line   57)
* -q (gnatdll):                          Using gnatdll.      (line   81)
* -q (gnatmake):                         Switches for gnatmake.
                                                             (line  316)
* -r (gnatbind):                         Output Control.     (line   48)
* -R (gnatbind):                         Switches for gnatbind.
                                                             (line  172)
* -r (gnatchop):                         Switches for gnatchop.
                                                             (line   53)
* -r (gnatclean):                        Switches for gnatclean.
                                                             (line   62)
* -r (gnatfind):                         gnatfind Switches.  (line  144)
* -r (gnatprep):                         Switches for gnatprep.
                                                             (line   32)
* -Ra (gnatbind):                        Switches for gnatbind.
                                                             (line  176)
* -RTS (gcc):                            Alphabetical List of All Switches.
                                                             (line  705)
* -RTS (gnatbind):                       Switches for gnatbind.
                                                             (line  153)
* -RTS (gnatfind):                       gnatfind Switches.  (line  107)
* -RTS (gnatls):                         Switches for gnatls.
                                                             (line   48)
* -RTS (gnatmake):                       Switches for gnatmake.
                                                             (line  437)
* -RTS (gnatxref):                       gnatxref Switches.  (line   69)
* -RTS option:                           Specifying a Run-Time Library.
                                                             (line   54)
* -RTS=sjlj (gnatmake):                  Exception Handling Control.
                                                             (line   29)
* -RTS=zcx (gnatmake):                   Exception Handling Control.
                                                             (line   39)
* -S (gcc):                              Alphabetical List of All Switches.
                                                             (line  710)
* -S (gnatbind):                         Switches for gnatbind.
                                                             (line  182)
* -s (gnatbind) <1>:                     Switches for gnatbind.
                                                             (line  179)
* -s (gnatbind):                         Consistency-Checking Modes.
                                                             (line   11)
* -s (gnatfind):                         gnatfind Switches.  (line  151)
* -s (gnatls):                           Switches for gnatls.
                                                             (line   29)
* -s (gnatmake):                         Switches for gnatmake.
                                                             (line  320)
* -s (gnatprep):                         Switches for gnatprep.
                                                             (line   46)
* -sc (gnathtml):                        Invoking gnathtml.  (line   72)
* -shared (gnatbind):                    Switches for gnatbind.
                                                             (line  236)
* -static (gnatbind):                    Switches for gnatbind.
                                                             (line  233)
* -subdirs= (gnatmake and gnatclean):    Switches Related to Project Files.
                                                             (line   55)
* -t (gnatbind):                         Switches for gnatbind.
                                                             (line  239)
* -T (gnatbind):                         Switches for gnatbind.
                                                             (line  242)
* -t (gnatbind):                         Binder Error Message Control.
                                                             (line   38)
* -t (gnatfind):                         gnatfind Switches.  (line  155)
* -t (gnathtml):                         Invoking gnathtml.  (line   77)
* -T0 option:                            Choosing the Scheduling Policy.
                                                             (line   12)
* -u (gnatbind):                         Switches for gnatbind.
                                                             (line  256)
* -u (gnatls):                           Switches for gnatls.
                                                             (line   32)
* -u (gnatmake):                         Switches for gnatmake.
                                                             (line  330)
* -U (gnatmake):                         Switches for gnatmake.
                                                             (line  336)
* -u (gnatprep):                         Switches for gnatprep.
                                                             (line   50)
* -v (dlltool):                          Using gnatdll.      (line  203)
* -V (gcc):                              Alphabetical List of All Switches.
                                                             (line  726)
* -v (gcc):                              Alphabetical List of All Switches.
                                                             (line  721)
* -V (gnatbind):                         Switches for gnatbind.
                                                             (line  268)
* -v (gnatbind) <1>:                     Switches for gnatbind.
                                                             (line  264)
* -v (gnatbind):                         Binder Error Message Control.
                                                             (line    9)
* -v (gnatchop):                         Switches for gnatchop.
                                                             (line   74)
* -v (gnatclean):                        Switches for gnatclean.
                                                             (line   69)
* -v (gnatdll):                          Using gnatdll.      (line   84)
* -v (gnatlink):                         Switches for gnatlink.
                                                             (line   36)
* -v (gnatls):                           Switches for gnatls.
                                                             (line   53)
* -v (gnatmake):                         Switches for gnatmake.
                                                             (line  343)
* -v (gnatname):                         Switches for gnatname.
                                                             (line   88)
* -v -v (gnatlink):                      Switches for gnatlink.
                                                             (line   42)
* -v -v (gnatname):                      Switches for gnatname.
                                                             (line   96)
* -v option (for GPRbuild):              Compiling with Project Files.
                                                             (line   46)
* -version (gnatbind):                   Switches for gnatbind.
                                                             (line    9)
* -version (gnatchop):                   Switches for gnatchop.
                                                             (line    8)
* -version (gnatclean):                  Switches for gnatclean.
                                                             (line    8)
* -version (gnatfind):                   gnatfind Switches.  (line   67)
* -version (gnatlink):                   Switches for gnatlink.
                                                             (line    8)
* -version (gnatls):                     Switches for gnatls.
                                                             (line    8)
* -version (gnatmake):                   Switches for gnatmake.
                                                             (line    8)
* -version (gnatname):                   Switches for gnatname.
                                                             (line   10)
* -version (gnatxref):                   gnatxref Switches.  (line   29)
* -vl (gnatmake):                        Switches for gnatmake.
                                                             (line  347)
* -vm (gnatmake):                        Switches for gnatmake.
                                                             (line  354)
* -vP (any project-aware tool):          Switches Related to Project Files.
                                                             (line   39)
* -vP (gnatclean):                       Switches for gnatclean.
                                                             (line   72)
* -w (gcc) <1>:                          Warning Message Control.
                                                             (line 1055)
* -w (gcc):                              Alphabetical List of All Switches.
                                                             (line  730)
* -w (gnatbind):                         Switches for gnatbind.
                                                             (line  273)
* -w (gnatchop):                         Switches for gnatchop.
                                                             (line   79)
* -Wall (gcc):                           Warning Message Control.
                                                             (line 1047)
* -we (gnatbind):                        Binder Error Message Control.
                                                             (line   35)
* -Werror (gcc):                         Warning Message Control.
                                                             (line 1061)
* -ws (gnatbind):                        Binder Error Message Control.
                                                             (line   32)
* -Wstack-usage (gcc):                   Warning Message Control.
                                                             (line 1043)
* -Wuninitialized (gcc):                 Warning Message Control.
                                                             (line 1038)
* -Wunused (gcc):                        Warning Message Control.
                                                             (line 1031)
* -Wx (gnatbind) <1>:                    Consistency-Checking Modes.
                                                             (line   19)
* -Wx (gnatbind):                        Switches for gnatbind.
                                                             (line  276)
* -X (any project-aware tool):           Switches Related to Project Files.
                                                             (line   22)
* -x (gnatbind) <1>:                     Consistency-Checking Modes.
                                                             (line   28)
* -x (gnatbind):                         Switches for gnatbind.
                                                             (line  280)
* -X (gnatclean):                        Switches for gnatclean.
                                                             (line   76)
* -x (gnatmake):                         Switches for gnatmake.
                                                             (line  361)
* -x (gnatname):                         Switches for gnatname.
                                                             (line  102)
* -X (usage with GNAT Project Manager):  Scenarios in Projects.
                                                             (line   32)
* -Xnnn (gnatbind):                      Switches for gnatbind.
                                                             (line  283)
* -y (gnatbind):                         Switches for gnatbind.
                                                             (line  286)
* -z (gnatbind) <1>:                     Binding Programs with No Main Subprogram.
                                                             (line   12)
* -z (gnatbind):                         Switches for gnatbind.
                                                             (line  289)
* -z (gnatmake):                         Switches for gnatmake.
                                                             (line  377)
* __gnat_malloc:                         Switches for gnatbind.
                                                             (line  109)
* Abnormal Termination or Failure to Terminate: Remote Debugging with gdbserver.
                                                             (line   47)
* Access before elaboration:             Run-Time Checks.    (line    6)
* access before elaboration:             Run-Time Checks.    (line    6)
* activate every optional warning:       Warning Message Control.
                                                             (line  350)
* Active (GNAT Project Manager):         Installation.       (line   15)
* ACVC:                                  Compiling Different Versions of Ada.
                                                             (line   11)
* Ada:                                   Search Paths for gnatbind.
                                                             (line   44)
* Ada 2005 Language Reference Manual:    What You Should Know before Reading This Guide.
                                                             (line    6)
* Ada 2005 mode:                         Compiling Different Versions of Ada.
                                                             (line   47)
* Ada 2012 mode:                         Compiling Different Versions of Ada.
                                                             (line   55)
* Ada 83 mode:                           Compiling Different Versions of Ada.
                                                             (line   11)
* Ada 83 tests:                          Compiling Different Versions of Ada.
                                                             (line   11)
* Ada 95 Language Reference Manual:      What You Should Know before Reading This Guide.
                                                             (line    6)
* Ada 95 mode:                           Compiling Different Versions of Ada.
                                                             (line   34)
* Ada compatibility issues warnings:     Warning Message Control.
                                                             (line  963)
* Ada expressions (in gdb):              Using Ada Expressions.
                                                             (line    6)
* Ada language extensions:               Compiling Different Versions of Ada.
                                                             (line   63)
* Ada Library Information files:         The Ada Library Information Files.
                                                             (line    6)
* Ada.Characters.Latin_1:                Latin-1.            (line   13)
* ADA_INCLUDE_PATH <1>:                  Search Paths and the Run-Time Library RTL.
                                                             (line   27)
* ADA_INCLUDE_PATH:                      Using a library.    (line   55)
* ADA_OBJECTS_PATH <1>:                  Search Paths for gnatbind.
                                                             (line   27)
* ADA_OBJECTS_PATH:                      Using a library.    (line   59)
* ADA_PRJ_INCLUDE_FILE:                  Search Paths and the Run-Time Library RTL.
                                                             (line   22)
* ADA_PRJ_OBJECTS_FILE:                  Search Paths for gnatbind.
                                                             (line   21)
* ADA_PROJECT_PATH:                      Installing a library.
                                                             (line    6)
* ADA_PROJECT_PATH (GNAT Project Manager): Project Dependencies.
                                                             (line   64)
* adafinal:                              Binding with Non-Ada Main Programs.
                                                             (line   37)
* adainit:                               Binding with Non-Ada Main Programs.
                                                             (line   22)
* Address Clauses:                       Warning Message Control.
                                                             (line  600)
* AIX resolver library:                  AIX-Specific Considerations.
                                                             (line    6)
* ALI files:                             The Ada Library Information Files.
                                                             (line    6)
* Aliasing <1>:                          Aliased Variables and Optimization.
                                                             (line    6)
* Aliasing:                              Optimization and Strict Aliasing.
                                                             (line    6)
* alternative:                           Alternative File Naming Schemes.
                                                             (line    6)
* Annex A (in Ada Reference Manual):     Naming Conventions for GNAT Source Files.
                                                             (line   45)
* Annex B (in Ada reference Manual):     Naming Conventions for GNAT Source Files.
                                                             (line   48)
* APIENTRY:                              Windows Calling Conventions.
                                                             (line    6)
* Artifacts (GNAT Project Manager):      Installation.       (line   19)
* Asm:                                   Calling Conventions.
                                                             (line   46)
* Assert:                                Debugging and Assertion Control.
                                                             (line    7)
* Assert failures:                       Warning Message Control.
                                                             (line  200)
* Assertions:                            Debugging and Assertion Control.
                                                             (line    7)
* Atomic:                                Atomic Variables and Optimization.
                                                             (line    6)
* Atomic Synchronization:                Warning Message Control.
                                                             (line  587)
* attach to process:                     Program Built with Foreign Tools and DLL Built with GCC/GNAT.
                                                             (line   71)
* Bad fixed values:                      Warning Message Control.
                                                             (line  206)
* Biased representation:                 Warning Message Control.
                                                             (line  224)
* Binder:                                Binding with Non-Ada Main Programs.
                                                             (line   43)
* Binder consistency checks:             Binder Error Message Control.
                                                             (line   38)
* Binder output (example):               Example of Binder Output File.
                                                             (line    6)
* Binder output file:                    Interfacing to C.   (line   83)
* Binding generation (for Ada specs):    Generating C Headers for Ada Specifications.
                                                             (line    6)
* Binding generation (for C and C++ headers): Generating Ada Bindings for C and C++ headers.
                                                             (line    6)
* BINUTILS_ROOT:                         Linking a Mixed C++ & Ada Program.
                                                             (line   28)
* bit order warnings:                    Warning Message Control.
                                                             (line  871)
* Body (GNAT Project Manager):           Naming Schemes.     (line  140)
* Body_Suffix (GNAT Project Manager):    Naming Schemes.     (line   76)
* Breakpoints and tasks:                 Ada Tasks.          (line   25)
* building <1>:                          Building DLLs with GNAT.
                                                             (line    6)
* building <2>:                          Building DLLs with GNAT Project files.
                                                             (line    6)
* building <3>:                          Building DLLs with gnatdll.
                                                             (line    6)
* building:                              Building Resources. (line    6)
* Building the GNAT Run-Time Library:    Rebuilding the GNAT Run-Time Library.
                                                             (line    6)
* C:                                     Calling Conventions.
                                                             (line   54)
* C headers (binding generation) <1>:    Generating C Headers for Ada Specifications.
                                                             (line    6)
* C headers (binding generation):        Generating Ada Bindings for C and C++ headers.
                                                             (line    6)
* C varargs function:                    Calling Conventions.
                                                             (line   60)
* C++:                                   Calling Conventions.
                                                             (line   83)
* C++ headers (binding generation):      Generating Ada Bindings for C and C++ headers.
                                                             (line    6)
* C_INCLUDE_PATH:                        Linking a Mixed C++ & Ada Program.
                                                             (line   28)
* Calling Conventions:                   Calling Conventions.
                                                             (line    6)
* cannot generate code:                  Compiling Programs. (line   29)
* case construction (GNAT Project Manager): Scenarios in Projects.
                                                             (line   65)
* Casing (GNAT Project Manager):         Naming Schemes.     (line   24)
* Ceiling_Locking (under rts-pthread):   Solaris Threads Issues.
                                                             (line    9)
* Check:                                 Run-Time Checks.    (line   62)
* Checks <1>:                            Run-Time Checks.    (line   13)
* Checks <2>:                            Checking the Elaboration Order.
                                                             (line   22)
* Checks <3>:                            Run-Time Checks.    (line    6)
* Checks <4>:                            Controlling Run-Time Checks.
                                                             (line   31)
* Checks:                                Run-Time Checks.    (line  130)
* Checks (overflow):                     Example of unused subprogram/data elimination.
                                                             (line   57)
* COBOL:                                 Calling Conventions.
                                                             (line   50)
* Code Coverage:                         Symbolic Traceback. (line  114)
* code page 437 (IBM PC):                Other 8-Bit Codes.  (line   28)
* code page 850 (IBM PC):                Other 8-Bit Codes.  (line   36)
* Combining GNAT switches:               Alphabetical List of All Switches.
                                                             (line  736)
* Command line length:                   Switches for gnatlink.
                                                             (line   16)
* command line length (GNAT Project Manager): Tools Options in Project Files.
                                                             (line   16)
* Compatibility with Ada 83:             Compiling Different Versions of Ada.
                                                             (line   11)
* compilation (definition):              Source Representation.
                                                             (line   33)
* Compilation model:                     The GNAT Compilation Model.
                                                             (line    6)
* compiling:                             Compiling Resources.
                                                             (line    6)
* Component clause:                      Warning Message Control.
                                                             (line  271)
* Conditional compilation <1>:           Conditional Compilation.
                                                             (line    9)
* Conditional compilation:               Rebuilding the GNAT Run-Time Library.
                                                             (line   20)
* Conditionals:                          Warning Message Control.
                                                             (line  239)
* configuration:                         Configuration Pragmas.
                                                             (line    6)
* Configuration pragmas:                 Configuration Pragmas.
                                                             (line    6)
* Consistency checks:                    Binder Error Message Control.
                                                             (line   38)
* CONSOLE Subsystem:                     CONSOLE and WINDOWS subsystems.
                                                             (line    6)
* constant:                              Warning Message Control.
                                                             (line  239)
* Convention Ada:                        Calling Conventions.
                                                             (line   10)
* Convention Asm:                        Calling Conventions.
                                                             (line   46)
* Convention Assembler:                  Calling Conventions.
                                                             (line   41)
* Convention C:                          Calling Conventions.
                                                             (line   54)
* Convention C++:                        Calling Conventions.
                                                             (line   83)
* Convention COBOL:                      Calling Conventions.
                                                             (line   49)
* Convention Default:                    Calling Conventions.
                                                             (line   77)
* Convention DLL:                        Calling Conventions.
                                                             (line  149)
* Convention External:                   Calling Conventions.
                                                             (line   80)
* Convention Fortran:                    Calling Conventions.
                                                             (line   88)
* Convention Stdcall:                    Calling Conventions.
                                                             (line  142)
* Convention Stubbed:                    Calling Conventions.
                                                             (line  155)
* Convention Win32:                      Calling Conventions.
                                                             (line  152)
* Conventions:                           Conventions.        (line    6)
* CR:                                    Source Representation.
                                                             (line    6)
* Cyrillic:                              Other 8-Bit Codes.  (line   20)
* Deactivated code:                      Warning Message Control.
                                                             (line  766)
* Debug:                                 Debugging and Assertion Control.
                                                             (line    7)
* Debug Pool:                            The GNAT Debug Pool Facility.
                                                             (line    6)
* Debugger:                              Running and Debugging Ada Programs.
                                                             (line   24)
* Debugging:                             Running and Debugging Ada Programs.
                                                             (line    6)
* Debugging Generic Units:               Ada Tasks.          (line   56)
* Debugging information:                 Switches for gnatlink.
                                                             (line   24)
* Debugging optimized code:              Debugging Optimized Code.
                                                             (line    6)
* Debugging options:                     Debugging Control.  (line    6)
* Default:                               Calling Conventions.
                                                             (line   77)
* Default_Switches (GNAT Project Manager): Tools Options in Project Files.
                                                             (line   74)
* Definition file:                       Creating an Import Library.
                                                             (line   12)
* Deleted code:                          Warning Message Control.
                                                             (line  766)
* Dependencies:                          Switches for gnatmake.
                                                             (line  278)
* Dependency rules (compilation):        Building with gnatmake.
                                                             (line   19)
* Dereferencing:                         Warning Message Control.
                                                             (line  296)
* Dimension aspect:                      Performing Dimensionality Analysis in GNAT.
                                                             (line   13)
* Dimension_System aspect:               Performing Dimensionality Analysis in GNAT.
                                                             (line   13)
* Dimensionality analysis:               Performing Dimensionality Analysis in GNAT.
                                                             (line    6)
* Dispatching calls:                     Elaboration for Indirect Calls.
                                                             (line    6)
* Division by zero:                      Run-Time Checks.    (line    6)
* division by zero:                      Run-Time Checks.    (line    6)
* DLL <1>:                               Introduction to Dynamic Link Libraries DLLs.
                                                             (line    6)
* DLL:                                   Calling Conventions.
                                                             (line  149)
* DLL debugging <1>:                     Program Built with Foreign Tools and DLL Built with GCC/GNAT.
                                                             (line   71)
* DLL debugging:                         Debugging a DLL.    (line    6)
* DLLs <1>:                              Building DLLs with GNAT.
                                                             (line    6)
* DLLs <2>:                              Building DLLs with gnatdll.
                                                             (line    6)
* DLLs:                                  Building DLLs with GNAT Project files.
                                                             (line    6)
* DLLs and elaboration:                  Ada DLLs and Elaboration.
                                                             (line    6)
* DLLs and finalization:                 Ada DLLs and Finalization.
                                                             (line    6)
* Dot_Replacement (GNAT Project Manager): Naming Schemes.    (line   34)
* elaboration <1>:                       Run-Time Checks.    (line  123)
* elaboration:                           Checking the Elaboration Order.
                                                             (line   22)
* Elaboration:                           Warning Message Control.
                                                             (line  519)
* Elaboration checks <1>:                Run-Time Checks.    (line  123)
* Elaboration checks:                    Checking the Elaboration Order.
                                                             (line   22)
* Elaboration control <1>:               Summary of Procedures for Elaboration Control.
                                                             (line    6)
* Elaboration control:                   Elaboration Order Handling in GNAT.
                                                             (line    6)
* elaboration issues:                    Elaboration Issues for Library Tasks.
                                                             (line    6)
* Elaboration of library tasks:          Elaboration Issues for Library Tasks.
                                                             (line    6)
* Elaboration order control:             Comparison between GNAT and C/C++ Compilation Models.
                                                             (line   24)
* End of source file; Source file, end:  Source Representation.
                                                             (line   27)
* environment variable; ADA_INCLUDE_PATH <1>: Using a library.
                                                             (line   55)
* environment variable; ADA_INCLUDE_PATH: Search Paths and the Run-Time Library RTL.
                                                             (line   27)
* environment variable; ADA_OBJECTS_PATH <1>: Using a library.
                                                             (line   59)
* environment variable; ADA_OBJECTS_PATH: Search Paths for gnatbind.
                                                             (line   27)
* environment variable; ADA_PRJ_INCLUDE_FILE: Search Paths and the Run-Time Library RTL.
                                                             (line   23)
* environment variable; ADA_PRJ_OBJECTS_FILE: Search Paths for gnatbind.
                                                             (line   21)
* environment variable; BINUTILS_ROOT:   Linking a Mixed C++ & Ada Program.
                                                             (line   28)
* environment variable; C_INCLUDE_PATH:  Linking a Mixed C++ & Ada Program.
                                                             (line   28)
* environment variable; GCC_EXEC_PREFIX: Linking a Mixed C++ & Ada Program.
                                                             (line   28)
* environment variable; GCC_ROOT:        Linking a Mixed C++ & Ada Program.
                                                             (line   29)
* environment variable; GNAT_PROCESSOR:  Solaris Threads Issues.
                                                             (line   24)
* environment variable; GNAT_STACK_LIMIT: Stack Overflow Checking.
                                                             (line   37)
* environment variable; PATH <1>:        Search Paths for gnatbind.
                                                             (line   28)
* environment variable; PATH:            Search Paths and the Run-Time Library RTL.
                                                             (line   28)
* environment variable; TMP:             Temporary Files.    (line    7)
* Error messages:                        Output and Error Message Control.
                                                             (line  124)
* EUC Coding:                            Wide_Character Encodings.
                                                             (line   39)
* Exceptions (in gdb):                   Stopping When Ada Exceptions Are Raised.
                                                             (line    6)
* Excluded_Source_Dirs (GNAT Project Manager): Source Files and Directories.
                                                             (line   47)
* Excluded_Source_Files (GNAT Project Manager) <1>: Project Extension.
                                                             (line   99)
* Excluded_Source_Files (GNAT Project Manager): Source Files and Directories.
                                                             (line  135)
* Excluded_Source_List_File (GNAT Project Manager) <1>: Source Files and Directories.
                                                             (line  135)
* Excluded_Source_List_File (GNAT Project Manager): Project Extension.
                                                             (line   99)
* Exec_Dir (GNAT Project Manager):       Object and Exec Directory.
                                                             (line   45)
* Executable (GNAT Project Manager):     Executable File Names.
                                                             (line    6)
* Executable_Suffix (GNAT Project Manager): Executable File Names.
                                                             (line   21)
* Export table:                          Exporting Ada Entities.
                                                             (line    6)
* Export/Import pragma warnings:         Warning Message Control.
                                                             (line  929)
* extends all (GNAT Project Manager):    Project Hierarchy Extension.
                                                             (line   40)
* External:                              Calling Conventions.
                                                             (line   80)
* external (GNAT Project Manager):       Scenarios in Projects.
                                                             (line   45)
* External (GNAT Project Manager):       Syntax of aggregate projects.
                                                             (line  173)
* Externally_Built (GNAT Project Manager): Project Dependencies.
                                                             (line   22)
* Features:                              Warning Message Control.
                                                             (line  460)
* FF:                                    Source Representation.
                                                             (line    6)
* File cleanup tool:                     The File Cleanup Utility gnatclean.
                                                             (line    6)
* File names <1>:                        Alternative File Naming Schemes.
                                                             (line    6)
* File names:                            Using Other File Names.
                                                             (line    6)
* File Naming Conventions:               Handling Arbitrary File Naming Conventions with gnatname.
                                                             (line    6)
* File naming schemes:                   Alternative File Naming Schemes.
                                                             (line    6)
* Fixed-point Small value:               Warning Message Control.
                                                             (line  206)
* Floating-Point Operations:             Floating_Point_Operations.
                                                             (line    6)
* for gnatmake:                          Switches for gnatmake.
                                                             (line  414)
* for profiling:                         Compilation for profiling.
                                                             (line    6)
* Foreign Languages:                     Calling Conventions.
                                                             (line    6)
* Formals:                               Warning Message Control.
                                                             (line  362)
* Fortran:                               Calling Conventions.
                                                             (line   88)
* GCC_EXEC_PREFIX:                       Linking a Mixed C++ & Ada Program.
                                                             (line   28)
* GCC_ROOT:                              Linking a Mixed C++ & Ada Program.
                                                             (line   29)
* gcov:                                  Code Coverage and Profiling.
                                                             (line    9)
* gdb:                                   Running and Debugging Ada Programs.
                                                             (line   24)
* Generic formal parameters:             Compiling Different Versions of Ada.
                                                             (line   24)
* Generics <1>:                          Ada Tasks.          (line   56)
* Generics:                              Generating Object Files.
                                                             (line   32)
* Global_Compilation_Switches (GNAT Project Manager) <1>: Global Attributes.
                                                             (line   27)
* Global_Compilation_Switches (GNAT Project Manager): package Builder in aggregate projects.
                                                             (line   27)
* Global_Config_File (GNAT Project Manager): package Builder in aggregate projects.
                                                             (line  117)
* Global_Configuration_Pragmas (GNAT Project Manager) <1>: package Builder in aggregate projects.
                                                             (line  106)
* Global_Configuration_Pragmas (GNAT Project Manager): Global Attributes.
                                                             (line   19)
* GNAT:                                  Search Paths for gnatbind.
                                                             (line   44)
* GNAT (package):                        Naming Conventions for GNAT Source Files.
                                                             (line   54)
* GNAT compilation model:                The GNAT Compilation Model.
                                                             (line    6)
* GNAT extensions:                       Compiling Different Versions of Ada.
                                                             (line   63)
* GNAT library:                          Comparison between GNAT and Conventional Ada Library Models.
                                                             (line   10)
* GNAT Run-Time Library:                 Rebuilding the GNAT Run-Time Library.
                                                             (line    6)
* gnat.adc <1>:                          Using Other File Names.
                                                             (line   35)
* gnat.adc:                              The Configuration Pragmas Files.
                                                             (line    6)
* gnat1:                                 Compiling Programs. (line   64)
* gnat_argc:                             Command-Line Access.
                                                             (line   13)
* gnat_argv:                             Command-Line Access.
                                                             (line   13)
* GNAT_INIT_SCALARS:                     Switches for gnatbind.
                                                             (line  226)
* GNAT_PROCESSOR:                        Solaris Threads Issues.
                                                             (line   24)
* GNAT_PROCESSOR environment variable (on Sparc Solaris): Solaris Threads Issues.
                                                             (line   19)
* GNAT_STACK_LIMIT:                      Stack Overflow Checking.
                                                             (line   33)
* gnatbind:                              Binding with gnatbind.
                                                             (line    6)
* gnatchop:                              Renaming Files with gnatchop.
                                                             (line    6)
* gnatclean:                             The File Cleanup Utility gnatclean.
                                                             (line    6)
* gnatdll:                               Using gnatdll.      (line    6)
* gnatfind:                              The Cross-Referencing Tools gnatxref and gnatfind.
                                                             (line    6)
* gnathtml:                              The Ada to HTML Converter gnathtml.
                                                             (line    6)
* gnatkr:                                File Name Krunching with gnatkr.
                                                             (line    6)
* gnatlink:                              Linking with gnatlink.
                                                             (line    6)
* gnatls:                                The GNAT Library Browser gnatls.
                                                             (line    6)
* gnatmake:                              Building with gnatmake.
                                                             (line    6)
* gnatname:                              Alternative File Naming Schemes.
                                                             (line  118)
* gnatprep <1>:                          Preprocessing.      (line   17)
* gnatprep:                              Preprocessing with gnatprep.
                                                             (line    6)
* gnatxref:                              The Cross-Referencing Tools gnatxref and gnatfind.
                                                             (line    6)
* GNU make:                              Using the GNU make Utility.
                                                             (line    6)
* GPR_PROJECT_PATH:                      Installing a library.
                                                             (line    6)
* GPR_PROJECT_PATH (GNAT Project Manager): Project Dependencies.
                                                             (line   64)
* GPR_PROJECT_PATH_FILE (GNAT Project Manager): Project Dependencies.
                                                             (line   64)
* gprof:                                 GNAT specifics.     (line   22)
* Hiding of Declarations:                Warning Message Control.
                                                             (line  400)
* HT:                                    Source Representation.
                                                             (line    6)
* Ignore_Source_Sub_Dirs (GNAT Project Manager): Source Files and Directories.
                                                             (line   53)
* Implementation (GNAT Project Manager): Naming Schemes.     (line  140)
* Implementation_Exceptions (GNAT Project Manager): Naming Schemes.
                                                             (line  144)
* Implementation_Suffix (GNAT Project Manager): Naming Schemes.
                                                             (line   76)
* implicit:                              Warning Message Control.
                                                             (line  296)
* Implicit dereferencing:                Warning Message Control.
                                                             (line  296)
* Import library:                        Creating an Import Library.
                                                             (line    6)
* Improving performance:                 Improving Performance.
                                                             (line    6)
* in binder:                             Binder Error Message Control.
                                                             (line   38)
* including:                             Switches for gnatlink.
                                                             (line   24)
* Indirect calls:                        Elaboration for Indirect Calls.
                                                             (line    6)
* Inheritance_Locking (under rts-pthread): Solaris Threads Issues.
                                                             (line    9)
* Inline <1>:                            Source Dependencies.
                                                             (line   27)
* Inline:                                Inlining of Subprograms.
                                                             (line   15)
* Inline Assembler:                      Inline Assembler.   (line    6)
* Inlining <1>:                          Warning Message Control.
                                                             (line  635)
* Inlining:                              Comparison between GNAT and Conventional Ada Library Models.
                                                             (line   35)
* Interfaces:                            Search Paths for gnatbind.
                                                             (line   44)
* Interfacing to Ada:                    Calling Conventions.
                                                             (line   10)
* Interfacing to Assembly:               Calling Conventions.
                                                             (line   41)
* Interfacing to C:                      Calling Conventions.
                                                             (line   54)
* Interfacing to C varargs function:     Calling Conventions.
                                                             (line   60)
* Interfacing to C++:                    Calling Conventions.
                                                             (line   83)
* Interfacing to COBOL:                  Calling Conventions.
                                                             (line   49)
* Interfacing to Fortran:                Calling Conventions.
                                                             (line   88)
* Internal trees:                        Auxiliary Output Control.
                                                             (line    6)
* ISO 8859-15:                           Other 8-Bit Codes.  (line   24)
* ISO 8859-2:                            Other 8-Bit Codes.  (line    8)
* ISO 8859-3:                            Other 8-Bit Codes.  (line   12)
* ISO 8859-4:                            Other 8-Bit Codes.  (line   16)
* ISO 8859-5:                            Other 8-Bit Codes.  (line   20)
* Languages (GNAT Project Manager):      Source Files and Directories.
                                                             (line   93)
* Latin-1 <1>:                           Latin-1.            (line    6)
* Latin-1:                               Source Representation.
                                                             (line    6)
* Latin-2:                               Other 8-Bit Codes.  (line    8)
* Latin-3:                               Other 8-Bit Codes.  (line   12)
* Latin-4:                               Other 8-Bit Codes.  (line   16)
* Latin-9:                               Other 8-Bit Codes.  (line   24)
* Leading_Library_Options (GNAT Project Manager): Building Libraries.
                                                             (line  121)
* LF:                                    Source Representation.
                                                             (line    6)
* Library browser:                       The GNAT Library Browser gnatls.
                                                             (line    6)
* Library building and using:            GNAT and Libraries. (line    6)
* Library tasks:                         Elaboration Issues for Library Tasks.
                                                             (line    6)
* Library_ALI_Dir (GNAT Project Manager): Building Libraries.
                                                             (line   71)
* Library_Auto_Init (GNAT Project Manager): Stand-alone Library Projects.
                                                             (line   79)
* Library_Dir (GNAT Project Manager) <1>: Building Libraries.
                                                             (line   24)
* Library_Dir (GNAT Project Manager):    Stand-alone Library Projects.
                                                             (line   94)
* Library_GCC (GNAT Project Manager):    Building Libraries. (line  104)
* Library_Interface (GNAT Project Manager): Stand-alone Library Projects.
                                                             (line   29)
* Library_Kind (GNAT Project Manager):   Building Libraries. (line   48)
* Library_Name (GNAT Project Manager):   Building Libraries. (line   14)
* Library_Options (GNAT Project Manager): Building Libraries.
                                                             (line  111)
* Library_Reference_Symbol_File (GNAT Project Manager): Stand-alone Library Projects.
                                                             (line  156)
* Library_Src_Dir (GNAT Project Manager): Stand-alone Library Projects.
                                                             (line  108)
* Library_Standalone (GNAT Project Manager): Stand-alone Library Projects.
                                                             (line   52)
* Library_Symbol_File (GNAT Project Manager): Stand-alone Library Projects.
                                                             (line  164)
* Library_Symbol_Policy (GNAT Project Manager): Stand-alone Library Projects.
                                                             (line  120)
* Library_Version (GNAT Project Manager): Building Libraries.
                                                             (line   81)
* Linker libraries:                      Switches for gnatmake.
                                                             (line  425)
* Linker_Options (GNAT Project Manager): Building Libraries. (line  127)
* Local_Configuration_Pragmas (GNAT Project Manager): Tools Options in Project Files.
                                                             (line  125)
* Locally_Removed_Files (GNAT Project Manager): Source Files and Directories.
                                                             (line  135)
* Machine_Overflows:                     Run-Time Checks.    (line  103)
* Main (GNAT Project Manager):           Main Subprograms.   (line   21)
* make (GNU):                            Using the GNU make Utility.
                                                             (line    6)
* memory corruption:                     The GNAT Debug Pool Facility.
                                                             (line    6)
* Memory Pool:                           Some Useful Memory Pools.
                                                             (line    6)
* Microsoft Visual Studio:               Using GNAT DLLs from Microsoft Visual Studio Applications.
                                                             (line    6)
* missing:                               Warning Message Control.
                                                             (line  271)
* Mixed Language Programming:            Mixed Language Programming.
                                                             (line    6)
* MKS_Type type:                         Performing Dimensionality Analysis in GNAT.
                                                             (line   26)
* multiple input files:                  Binding with Non-Ada Main Programs.
                                                             (line   43)
* Multiple units:                        Using gcc for Syntax Checking.
                                                             (line   36)
* naming scheme:                         Switches for gnatmake.
                                                             (line  184)
* Naming scheme (GNAT Project Manager):  Source Files and Directories.
                                                             (line   98)
* No information messages for why package spec needs body: Warning Message Control.
                                                             (line  992)
* No_Entry_Calls_In_Elaboration_Code restriction: Elaboration Issues for Library Tasks.
                                                             (line  278)
* No_Strict_Aliasing:                    Optimization and Strict Aliasing.
                                                             (line    6)
* non-symbolic:                          Stack Traceback.    (line   21)
* Object_Dir (GNAT Project Manager):     Object and Exec Directory.
                                                             (line   16)
* obsolescent:                           Warning Message Control.
                                                             (line  460)
* Obsolescent features:                  Warning Message Control.
                                                             (line  460)
* Optimization and debugging:            Debugging Optimized Code.
                                                             (line    6)
* Optimization Switches <1>:             Other Optimization Switches.
                                                             (line    6)
* Optimization Switches:                 Vectorization of loops.
                                                             (line    6)
* Order of elaboration:                  Elaboration Order Handling in GNAT.
                                                             (line    6)
* OS X:                                  Mac OS Topics.      (line    6)
* Other Ada compilers:                   Calling Conventions.
                                                             (line   10)
* overflow <1>:                          Run-Time Checks.    (line   62)
* overflow:                              Controlling Run-Time Checks.
                                                             (line   31)
* Overflow checks <1>:                   Example of unused subprogram/data elimination.
                                                             (line   57)
* Overflow checks <2>:                   Run-Time Checks.    (line   62)
* Overflow checks:                       Controlling Run-Time Checks.
                                                             (line   31)
* Overflow mode:                         Run-Time Checks.    (line   62)
* Package spec needing body:             Warning Message Control.
                                                             (line  981)
* Parallel make:                         Switches for gnatmake.
                                                             (line  232)
* Parameter order:                       Warning Message Control.
                                                             (line  653)
* Parentheses:                           Warning Message Control.
                                                             (line  670)
* Passive Task:                          Passive Task Optimization.
                                                             (line    6)
* PATH <1>:                              Search Paths and the Run-Time Library RTL.
                                                             (line   28)
* PATH:                                  Search Paths for gnatbind.
                                                             (line   28)
* pool <1>:                              Some Useful Memory Pools.
                                                             (line    6)
* pool:                                  The GNAT Debug Pool Facility.
                                                             (line    6)
* portability of path names (GNAT Project Manager): Source Files and Directories.
                                                             (line   32)
* Postcondition:                         Debugging and Assertion Control.
                                                             (line    7)
* pragma Assert:                         Debugging - A Special Case.
                                                             (line   22)
* pragma Assertion_Policy:               Debugging - A Special Case.
                                                             (line   42)
* pragma Debug:                          Debugging - A Special Case.
                                                             (line   49)
* pragma Debug_Policy:                   Debugging - A Special Case.
                                                             (line   65)
* pragma Elaborate:                      Controlling the Elaboration Order.
                                                             (line   95)
* Pragma Elaborate:                      Treatment of Pragma Elaborate.
                                                             (line    6)
* pragma Elaborate_All:                  Controlling the Elaboration Order.
                                                             (line  103)
* pragma Elaborate_Body:                 Controlling the Elaboration Order.
                                                             (line   51)
* pragma Export:                         The External Symbol Naming Scheme of GNAT.
                                                             (line   20)
* pragma Inline:                         Inlining of Subprograms.
                                                             (line   15)
* pragma Locking_Policy (under rts-pthread): Solaris Threads Issues.
                                                             (line    9)
* pragma Overflow_Mode:                  Specifying the Desired Mode.
                                                             (line    6)
* pragma Preelaborate:                   Controlling the Elaboration Order.
                                                             (line   44)
* pragma Pure:                           Controlling the Elaboration Order.
                                                             (line   35)
* pragma Restrictions:                   Debugging Control.  (line  151)
* pragma Suppress:                       Controlling Run-Time Checks.
                                                             (line   31)
* pragma Task_Dispatching_Policy:        Choosing the Scheduling Policy.
                                                             (line   12)
* pragma Time_Slice:                     Choosing the Scheduling Policy.
                                                             (line   12)
* pragma Unsuppress:                     Controlling Run-Time Checks.
                                                             (line   31)
* Pragmas <1>:                           Configuration Pragmas.
                                                             (line    6)
* Pragmas:                               Warning Message Control.
                                                             (line  378)
* Precondition:                          Debugging and Assertion Control.
                                                             (line    7)
* Prefix (GNAT Project Manager):         Installation.       (line   28)
* Preprocessing:                         Preprocessing.      (line    6)
* Preprocessing (gnatprep):              Preprocessing with gnatprep.
                                                             (line    6)
* Preprocessors (contrasted with conditional compilation): Use of Boolean Constants.
                                                             (line   24)
* producing list:                        Switches for gnatmake.
                                                             (line  278)
* Profiling <1>:                         GNAT specifics.     (line   22)
* Profiling:                             Symbolic Traceback. (line  114)
* project file packages (GNAT Project Manager): Tools Options in Project Files.
                                                             (line   34)
* project path (GNAT Project Manager):   Project Dependencies.
                                                             (line   56)
* project qualifier (GNAT Project Manager): Sharing Between Projects.
                                                             (line   91)
* Project_Files (GNAT Project Manager):  Syntax of aggregate projects.
                                                             (line   54)
* Project_Path (GNAT Project Manager):   Syntax of aggregate projects.
                                                             (line  100)
* PTHREAD_PRIO_INHERIT policy (under rts-pthread): Solaris Threads Issues.
                                                             (line    9)
* PTHREAD_PRIO_PROTECT policy (under rts-pthread): Solaris Threads Issues.
                                                             (line    9)
* rc:                                    Compiling Resources.
                                                             (line    6)
* rebuilding:                            Rebuilding the GNAT Run-Time Library.
                                                             (line    6)
* Rebuilding the GNAT Run-Time Library:  Rebuilding the GNAT Run-Time Library.
                                                             (line    6)
* Recompilation (by gnatmake):           Notes on the Command Line.
                                                             (line    9)
* Record Representation (component sizes): Warning Message Control.
                                                             (line  749)
* Record Representation (gaps):          Warning Message Control.
                                                             (line  414)
* Remote Debugging with gdbserver:       Debugging Generic Units.
                                                             (line   48)
* Resources <1>:                         Compiling Resources.
                                                             (line    6)
* Resources <2>:                         Building Resources. (line    6)
* Resources <3>:                         Using Resources.    (line    6)
* Resources:                             GNAT and Windows Resources.
                                                             (line    6)
* Root_Dir (GNAT Project Manager):       Distributed support.
                                                             (line   12)
* RTL:                                   Alphabetical List of All Switches.
                                                             (line  661)
* rts-pthread threads library:           Solaris-Specific Considerations.
                                                             (line    9)
* Run-time libraries (platform-specific information): Run-Time Libraries.
                                                             (line    6)
* Run-Time Library:                      Rebuilding the GNAT Run-Time Library.
                                                             (line    6)
* s-dimmks.ads file:                     Performing Dimensionality Analysis in GNAT.
                                                             (line   33)
* scenarios (GNAT Project Manager):      Scenarios in Projects.
                                                             (line   28)
* SCHED_FIFO scheduling policy:          Specifying a Run-Time Library.
                                                             (line   55)
* SCHED_OTHER scheduling policy:         Specifying a Run-Time Library.
                                                             (line   57)
* SCHED_RR scheduling policy:            Specifying a Run-Time Library.
                                                             (line   57)
* Search paths:                          Switches for gnatmake.
                                                             (line  414)
* Separate_Suffix (GNAT Project Manager): Naming Schemes.    (line  110)
* setjmp/longjmp Exception Model:        Run-Time Libraries. (line   22)
* Shift JIS Coding:                      Wide_Character Encodings.
                                                             (line   31)
* Size/Alignment warnings:               Warning Message Control.
                                                             (line 1013)
* SJLJ (setjmp/longjmp Exception Model): Run-Time Libraries. (line   22)
* Small value:                           Warning Message Control.
                                                             (line  206)
* Solaris Sparc threads libraries:       Choosing the Scheduling Policy.
                                                             (line   24)
* Source directories (GNAT Project Manager): Source Files and Directories.
                                                             (line   47)
* Source files <1>:                      Switches for gnatmake.
                                                             (line  420)
* Source files <2>:                      Switches for gnatclean.
                                                             (line   88)
* Source files:                          Running gnatbind.   (line   30)
* Source_Dirs (GNAT Project Manager):    Source Files and Directories.
                                                             (line   16)
* Source_File_Name pragma <1>:           Using Other File Names.
                                                             (line   12)
* Source_File_Name pragma:               Alternative File Naming Schemes.
                                                             (line   12)
* Source_Files (GNAT Project Manager):   Source Files and Directories.
                                                             (line  107)
* Source_List_File (GNAT Project Manager): Source Files and Directories.
                                                             (line  124)
* Source_Reference pragmas:              Switches for gnatchop.
                                                             (line   53)
* spec (definition):                     Source Representation.
                                                             (line   33)
* Spec (GNAT Project Manager):           Naming Schemes.     (line  123)
* Spec_Suffix (GNAT Project Manager):    Naming Schemes.     (line   53)
* Specification (GNAT Project Manager):  Naming Schemes.     (line  123)
* Specification_Exceptions (GNAT Project Manager): Naming Schemes.
                                                             (line  144)
* Specification_Suffix (GNAT Project Manager): Naming Schemes.
                                                             (line   53)
* Stack Overflow Checking <1>:           Stack Overflow Checking.
                                                             (line    6)
* Stack Overflow Checking:               Run-Time Checks.    (line  130)
* stack overflow checking:               Run-Time Checks.    (line    6)
* stack traceback:                       Getting Internal Debugging Information.
                                                             (line   22)
* stack unwinding:                       Getting Internal Debugging Information.
                                                             (line   22)
* Stand-alone libraries:                 Stand-alone Ada Libraries.
                                                             (line    6)
* standalone libraries (usage with GNAT Project Manager): Stand-alone Library Projects.
                                                             (line    6)
* Static Stack Usage Analysis:           Static Stack Usage Analysis.
                                                             (line    6)
* Stdcall <1>:                           Windows Calling Conventions.
                                                             (line    6)
* Stdcall:                               Calling Conventions.
                                                             (line  142)
* stderr:                                Output and Error Message Control.
                                                             (line    6)
* storage <1>:                           Some Useful Memory Pools.
                                                             (line    6)
* storage:                               The GNAT Debug Pool Facility.
                                                             (line    6)
* Strict Aliasing:                       Optimization and Strict Aliasing.
                                                             (line    6)
* String indexing warnings:              Warning Message Control.
                                                             (line  889)
* Stubbed:                               Calling Conventions.
                                                             (line  155)
* Style checking:                        Style Checking.     (line    6)
* SUB (control character):               Source Representation.
                                                             (line   27)
* Subtype predicates:                    Debugging and Assertion Control.
                                                             (line    7)
* Subunits:                              Generating Object Files.
                                                             (line   24)
* Subunits (and conditional compilation): Use of Alternative Implementations.
                                                             (line   20)
* Suppress <1>:                          Controlling Run-Time Checks.
                                                             (line   31)
* Suppress:                              Run-Time Checks.    (line   59)
* suppressing <1>:                       Run-Time Checks.    (line   59)
* suppressing:                           Output and Error Message Control.
                                                             (line  124)
* Suppressing checks:                    Run-Time Checks.    (line   59)
* suppressing search <1>:                Switches for gnatclean.
                                                             (line   88)
* suppressing search:                    Switches for gnatmake.
                                                             (line  420)
* Switches (GNAT Project Manager) <1>:   package Builder in aggregate projects.
                                                             (line   10)
* Switches (GNAT Project Manager):       Tools Options in Project Files.
                                                             (line   92)
* symbolic:                              Non-Symbolic Traceback.
                                                             (line  222)
* symbolic links:                        Switches for gnatmake.
                                                             (line  179)
* syntax checking:                       Using gcc for Syntax Checking.
                                                             (line   36)
* System:                                Search Paths for gnatbind.
                                                             (line   44)
* System (package in Ada Reference Manual): Naming Conventions for GNAT Source Files.
                                                             (line   51)
* System.Dim.Mks package (GNAT library): Performing Dimensionality Analysis in GNAT.
                                                             (line   26)
* System.IO:                             Search Paths and the Run-Time Library RTL.
                                                             (line   51)
* Task switching (in gdb):               Ada Tasks.          (line   45)
* Tasking and threads libraries:         Run-Time Libraries. (line    6)
* Tasks (in gdb):                        Stopping When Ada Exceptions Are Raised.
                                                             (line   32)
* Temporary files:                       Temporary Files.    (line    6)
* Text_IO and performance:               Text_IO Suggestions.
                                                             (line    6)
* Threads libraries and tasking:         Run-Time Libraries. (line    6)
* Time stamp checks:                     Binder Error Message Control.
                                                             (line   38)
* TMP:                                   Temporary Files.    (line    9)
* traceback <1>:                         Non-Symbolic Traceback.
                                                             (line  222)
* traceback <2>:                         Getting Internal Debugging Information.
                                                             (line   22)
* traceback:                             Stack Traceback.    (line   21)
* treat as error:                        Warning Message Control.
                                                             (line  336)
* Type invariants:                       Debugging and Assertion Control.
                                                             (line    7)
* typed variable (GNAT Project Manager): Scenarios in Projects.
                                                             (line   65)
* typographical:                         Conventions.        (line    6)
* Typographical conventions:             Conventions.        (line    6)
* Unassigned variable warnings:          Warning Message Control.
                                                             (line  849)
* Unchecked_Conversion warnings:         Warning Message Control.
                                                             (line  998)
* unrecognized:                          Warning Message Control.
                                                             (line  378)
* unreferenced:                          Warning Message Control.
                                                             (line  362)
* Unsuppress <1>:                        Run-Time Checks.    (line  134)
* Unsuppress:                            Controlling Run-Time Checks.
                                                             (line   31)
* Upper-Half Coding:                     Wide_Character Encodings.
                                                             (line   23)
* use by binder:                         Running gnatbind.   (line   30)
* use with GNAT DLLs:                    Using GNAT DLLs from Microsoft Visual Studio Applications.
                                                             (line    6)
* using:                                 Using Resources.    (line    6)
* Uunused subprogram/data elimination:   Reducing Size of Executables with Unused Subprogram/Data Elimination.
                                                             (line    6)
* Validity Checking:                     Validity Checking.  (line    6)
* varargs function interfaces:           Calling Conventions.
                                                             (line   60)
* Version skew (avoided by *gnatmake*):  Running a Simple Ada Program.
                                                             (line   67)
* Volatile parameter:                    The Volatile Parameter.
                                                             (line    6)
* VT:                                    Source Representation.
                                                             (line    6)
* Warning messages:                      Warning Message Control.
                                                             (line    6)
* warnings:                              Warning Message Control.
                                                             (line  597)
* Warnings <1>:                          Warning Message Control.
                                                             (line  350)
* Warnings:                              Binder Error Message Control.
                                                             (line   32)
* warnings:                              Warning Message Control.
                                                             (line  519)
* Warnings Off control:                  Warning Message Control.
                                                             (line  911)
* Win32:                                 Calling Conventions.
                                                             (line  152)
* windows:                               GNAT and Windows Resources.
                                                             (line    6)
* Windows 95:                            AIX-Specific Considerations.
                                                             (line   18)
* Windows 98:                            AIX-Specific Considerations.
                                                             (line   18)
* Windows NT:                            AIX-Specific Considerations.
                                                             (line   18)
* WINDOWS Subsystem:                     CONSOLE and WINDOWS subsystems.
                                                             (line    6)
* windres:                               Compiling Resources.
                                                             (line    6)
* Writing internal trees:                Auxiliary Output Control.
                                                             (line    6)
* writing to file:                       Auxiliary Output Control.
                                                             (line    6)
* ZCX (Zero-Cost Exceptions):            Run-Time Libraries. (line   18)
* Zero Cost Exceptions:                  Exception Handling Control.
                                                             (line   39)
* Zero-Cost Exceptions:                  Run-Time Libraries. (line   18)



Tag Table:
Node: Top372
Ref: gnat_ugn doc658
Ref: 0658
Node: About This Guide15257
Ref: gnat_ugn/about_this_guide about-this-guide15361
Ref: 215361
Ref: gnat_ugn/about_this_guide doc15361
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Ref: gnat_ugn/about_this_guide gnat-user-s-guide-for-native-platforms15361
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Ref: 515361
Node: What This Guide Contains16220
Ref: gnat_ugn/about_this_guide what-this-guide-contains16354
Ref: 716354
Node: What You Should Know before Reading This Guide18031
Ref: gnat_ugn/about_this_guide what-you-should-know-before-reading-this-guide18193
Ref: 1318193
Node: Related Information18628
Ref: gnat_ugn/about_this_guide related-information18818
Ref: 1418818
Node: A Note to Readers of Previous Versions of the Manual19684
Ref: gnat_ugn/about_this_guide a-note-to-readers-of-previous-versions-of-the-manual19839
Ref: 1519839
Node: Conventions22466
Ref: gnat_ugn/about_this_guide conventions22593
Ref: 3022593
Node: Getting Started with GNAT23368
Ref: gnat_ugn/getting_started_with_gnat getting-started-with-gnat23495
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Ref: gnat_ugn/getting_started_with_gnat doc23495
Ref: 3123495
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Node: Running GNAT24148
Ref: gnat_ugn/getting_started_with_gnat running-gnat24261
Ref: 3324261
Ref: gnat_ugn/getting_started_with_gnat id224261
Ref: 3424261
Node: Running a Simple Ada Program24755
Ref: gnat_ugn/getting_started_with_gnat running-a-simple-ada-program24914
Ref: 3524914
Ref: gnat_ugn/getting_started_with_gnat id324914
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Node: Running a Program with Multiple Units28137
Ref: gnat_ugn/getting_started_with_gnat id428310
Ref: 3928310
Ref: gnat_ugn/getting_started_with_gnat running-a-program-with-multiple-units28310
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Node: Using the gnatmake Utility30333
Ref: gnat_ugn/getting_started_with_gnat using-the-gnatmake-utility30469
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Ref: gnat_ugn/getting_started_with_gnat id530469
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Node: The GNAT Compilation Model32686
Ref: gnat_ugn/the_gnat_compilation_model doc32835
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Node: Foreign Language Representation36214
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Ref: 4036381
Ref: gnat_ugn/the_gnat_compilation_model id336381
Ref: 4936381
Node: Latin-136754
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Ref: 4c36857
Node: Other 8-Bit Codes37625
Ref: gnat_ugn/the_gnat_compilation_model other-8-bit-codes37761
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Ref: gnat_ugn/the_gnat_compilation_model id537761
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Node: Wide_Character Encodings39929
Ref: gnat_ugn/the_gnat_compilation_model id640087
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Ref: gnat_ugn/the_gnat_compilation_model wide-character-encodings40087
Ref: 5040087
Node: Wide_Wide_Character Encodings43810
Ref: gnat_ugn/the_gnat_compilation_model id743942
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Ref: gnat_ugn/the_gnat_compilation_model wide-wide-character-encodings43942
Ref: 5243942
Node: File Naming Topics and Utilities45634
Ref: gnat_ugn/the_gnat_compilation_model id845801
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Ref: gnat_ugn/the_gnat_compilation_model file-naming-topics-and-utilities45801
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Node: File Naming Rules46310
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Ref: gnat_ugn/the_gnat_compilation_model id946429
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Node: Using Other File Names49207
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Ref: gnat_ugn/the_gnat_compilation_model using-other-file-names49366
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Node: Alternative File Naming Schemes51570
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Ref: gnat_ugn/the_gnat_compilation_model alternative-file-naming-schemes51768
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Node: Handling Arbitrary File Naming Conventions with gnatname56784
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Node: Arbitrary File Naming Conventions57248
Ref: gnat_ugn/the_gnat_compilation_model arbitrary-file-naming-conventions57401
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Node: Running gnatname58520
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Node: Switches for gnatname60490
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Ref: gnat_ugn/the_gnat_compilation_model switches-for-gnatname60666
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Node: Examples of gnatname Usage65153
Ref: gnat_ugn/the_gnat_compilation_model examples-of-gnatname-usage65304
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Ref: gnat_ugn/the_gnat_compilation_model id1665304
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Node: File Name Krunching with gnatkr65962
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Node: About gnatkr66618
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Node: Using gnatkr67649
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Ref: gnat_ugn/the_gnat_compilation_model krunching-method69399
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Node: Examples of gnatkr Usage72499
Ref: gnat_ugn/the_gnat_compilation_model id2172618
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Ref: gnat_ugn/the_gnat_compilation_model examples-of-gnatkr-usage72618
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Node: Renaming Files with gnatchop73055
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Ref: gnat_ugn/the_gnat_compilation_model renaming-files-with-gnatchop73194
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Node: Handling Files with Multiple Units73650
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Ref: gnat_ugn/the_gnat_compilation_model handling-files-with-multiple-units73798
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Node: Operating gnatchop in Compilation Mode75276
Ref: gnat_ugn/the_gnat_compilation_model operating-gnatchop-in-compilation-mode75458
Ref: 7175458
Ref: gnat_ugn/the_gnat_compilation_model id2475458
Ref: 7275458
Node: Command Line for gnatchop78549
Ref: gnat_ugn/the_gnat_compilation_model id2578718
Ref: 7378718
Ref: gnat_ugn/the_gnat_compilation_model command-line-for-gnatchop78718
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Node: Switches for gnatchop80488
Ref: gnat_ugn/the_gnat_compilation_model switches-for-gnatchop80645
Ref: 7580645
Ref: gnat_ugn/the_gnat_compilation_model id2680645
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Node: Examples of gnatchop Usage84491
Ref: gnat_ugn/the_gnat_compilation_model id2784614
Ref: 7784614
Ref: gnat_ugn/the_gnat_compilation_model examples-of-gnatchop-usage84614
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Node: Configuration Pragmas85798
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Ref: gnat_ugn/the_gnat_compilation_model configuration-pragmas85957
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Node: Handling of Configuration Pragmas87918
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Ref: gnat_ugn/the_gnat_compilation_model handling-of-configuration-pragmas88051
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Node: The Configuration Pragmas Files89995
Ref: gnat_ugn/the_gnat_compilation_model the-configuration-pragmas-files90128
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Ref: gnat_ugn/the_gnat_compilation_model id3090128
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Node: Generating Object Files92112
Ref: gnat_ugn/the_gnat_compilation_model generating-object-files92258
Ref: 4292258
Ref: gnat_ugn/the_gnat_compilation_model id3192258
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Node: Source Dependencies94815
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Ref: gnat_ugn/the_gnat_compilation_model source-dependencies94973
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Node: The Ada Library Information Files98672
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Node: Binding an Ada Program100808
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Node: GNAT and Libraries102645
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Node: Introduction to Libraries in GNAT103227
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Node: General Ada Libraries105463
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Node: Building a library105752
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Node: Installing a library109561
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Node: Using a library112033
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Node: Stand-alone Ada Libraries114626
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Node: Introduction to Stand-alone Libraries115044
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Node: Building a Stand-alone Library116776
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Node: Creating a Stand-alone Library to be used in a non-Ada context121536
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Node: Restrictions in Stand-alone Libraries124472
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Ref: gnat_ugn/the_gnat_compilation_model restrictions-in-stand-alone-libraries124644
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Node: Rebuilding the GNAT Run-Time Library125926
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Node: Conditional Compilation126814
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Ref: gnat_ugn/the_gnat_compilation_model id48127407
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Node: Use of Boolean Constants128962
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Node: Debugging - A Special Case130374
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Node: Conditionalizing Declarations133951
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Node: A Simple Example177964
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Node: Generating Ada Bindings for C and C++ headers196225
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Node: Running the Binding Generator197631
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Node: Generating Bindings for C++ Headers200752
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Node: Switches203777
Ref: gnat_ugn/the_gnat_compilation_model switches203913
Ref: ce203913
Ref: gnat_ugn/the_gnat_compilation_model switches-for-ada-binding-generation203913
Ref: cf203913
Node: Generating C Headers for Ada Specifications204461
Ref: gnat_ugn/the_gnat_compilation_model generating-c-headers-for-ada-specifications204623
Ref: d0204623
Ref: gnat_ugn/the_gnat_compilation_model id73204623
Ref: d1204623
Node: Running the C Header Generator205125
Ref: gnat_ugn/the_gnat_compilation_model running-the-c-header-generator205237
Ref: d2205237
Node: GNAT and Other Compilation Models206954
Ref: gnat_ugn/the_gnat_compilation_model id74207132
Ref: d3207132
Ref: gnat_ugn/the_gnat_compilation_model gnat-and-other-compilation-models207132
Ref: 47207132
Node: Comparison between GNAT and C/C++ Compilation Models207565
Ref: gnat_ugn/the_gnat_compilation_model comparison-between-gnat-and-c-c-compilation-models207757
Ref: d4207757
Ref: gnat_ugn/the_gnat_compilation_model id75207757
Ref: d5207757
Node: Comparison between GNAT and Conventional Ada Library Models209260
Ref: gnat_ugn/the_gnat_compilation_model comparison-between-gnat-and-conventional-ada-library-models209452
Ref: d6209452
Ref: gnat_ugn/the_gnat_compilation_model id76209452
Ref: d7209452
Node: Using GNAT Files with External Tools211818
Ref: gnat_ugn/the_gnat_compilation_model using-gnat-files-with-external-tools211961
Ref: 1c211961
Ref: gnat_ugn/the_gnat_compilation_model id77211961
Ref: d8211961
Node: Using Other Utility Programs with GNAT212257
Ref: gnat_ugn/the_gnat_compilation_model using-other-utility-programs-with-gnat212420
Ref: d9212420
Ref: gnat_ugn/the_gnat_compilation_model id78212420
Ref: da212420
Node: The External Symbol Naming Scheme of GNAT212978
Ref: gnat_ugn/the_gnat_compilation_model the-external-symbol-naming-scheme-of-gnat213141
Ref: db213141
Ref: gnat_ugn/the_gnat_compilation_model id79213141
Ref: dc213141
Node: Building Executable Programs with GNAT214979
Ref: gnat_ugn/building_executable_programs_with_gnat building-executable-programs-with-gnat215123
Ref: a215123
Ref: gnat_ugn/building_executable_programs_with_gnat doc215123
Ref: dd215123
Ref: gnat_ugn/building_executable_programs_with_gnat id1215123
Ref: de215123
Node: Building with gnatmake216019
Ref: gnat_ugn/building_executable_programs_with_gnat the-gnat-make-program-gnatmake216145
Ref: 1d216145
Ref: gnat_ugn/building_executable_programs_with_gnat building-with-gnatmake216145
Ref: df216145
Node: Running gnatmake217704
Ref: gnat_ugn/building_executable_programs_with_gnat running-gnatmake217811
Ref: e0217811
Ref: gnat_ugn/building_executable_programs_with_gnat id2217811
Ref: e1217811
Node: Switches for gnatmake219195
Ref: gnat_ugn/building_executable_programs_with_gnat switches-for-gnatmake219337
Ref: e2219337
Ref: gnat_ugn/building_executable_programs_with_gnat id3219337
Ref: e3219337
Node: Mode Switches for gnatmake239727
Ref: gnat_ugn/building_executable_programs_with_gnat id4239878
Ref: e7239878
Ref: gnat_ugn/building_executable_programs_with_gnat mode-switches-for-gnatmake239878
Ref: e8239878
Node: Notes on the Command Line241085
Ref: gnat_ugn/building_executable_programs_with_gnat id5241233
Ref: e9241233
Ref: gnat_ugn/building_executable_programs_with_gnat notes-on-the-command-line241233
Ref: ea241233
Node: How gnatmake Works243630
Ref: gnat_ugn/building_executable_programs_with_gnat id6243778
Ref: eb243778
Ref: gnat_ugn/building_executable_programs_with_gnat how-gnatmake-works243778
Ref: ec243778
Node: Examples of gnatmake Usage246068
Ref: gnat_ugn/building_executable_programs_with_gnat examples-of-gnatmake-usage246182
Ref: ed246182
Ref: gnat_ugn/building_executable_programs_with_gnat id7246182
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Node: Compiling with gcc247197
Ref: gnat_ugn/building_executable_programs_with_gnat compiling-with-gcc247349
Ref: 1e247349
Ref: gnat_ugn/building_executable_programs_with_gnat id8247349
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Node: Compiling Programs247741
Ref: gnat_ugn/building_executable_programs_with_gnat compiling-programs247866
Ref: f0247866
Ref: gnat_ugn/building_executable_programs_with_gnat id9247866
Ref: f1247866
Node: Search Paths and the Run-Time Library RTL251137
Ref: gnat_ugn/building_executable_programs_with_gnat id10251298
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Ref: gnat_ugn/building_executable_programs_with_gnat search-paths-and-the-run-time-library-rtl251298
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Node: Order of Compilation Issues254610
Ref: gnat_ugn/building_executable_programs_with_gnat id11254761
Ref: f4254761
Ref: gnat_ugn/building_executable_programs_with_gnat order-of-compilation-issues254761
Ref: f5254761
Node: Examples256318
Ref: gnat_ugn/building_executable_programs_with_gnat id12256419
Ref: f6256419
Ref: gnat_ugn/building_executable_programs_with_gnat examples256419
Ref: f7256419
Node: Compiler Switches256878
Ref: gnat_ugn/building_executable_programs_with_gnat compiler-switches257029
Ref: f8257029
Ref: gnat_ugn/building_executable_programs_with_gnat switches-for-gcc257029
Ref: f2257029
Node: Alphabetical List of All Switches258178
Ref: gnat_ugn/building_executable_programs_with_gnat id13258308
Ref: f9258308
Ref: gnat_ugn/building_executable_programs_with_gnat alphabetical-list-of-all-switches258308
Ref: fa258308
Node: Output and Error Message Control290148
Ref: gnat_ugn/building_executable_programs_with_gnat id14290310
Ref: 105290310
Ref: gnat_ugn/building_executable_programs_with_gnat output-and-error-message-control290310
Ref: 106290310
Node: Warning Message Control298542
Ref: gnat_ugn/building_executable_programs_with_gnat warning-message-control298702
Ref: 102298702
Ref: gnat_ugn/building_executable_programs_with_gnat id15298702
Ref: 107298702
Node: Debugging and Assertion Control341768
Ref: gnat_ugn/building_executable_programs_with_gnat debugging-and-assertion-control341913
Ref: 108341913
Ref: gnat_ugn/building_executable_programs_with_gnat id16341913
Ref: 109341913
Node: Validity Checking344424
Ref: gnat_ugn/building_executable_programs_with_gnat validity-checking344560
Ref: fe344560
Ref: gnat_ugn/building_executable_programs_with_gnat id17344560
Ref: 10a344560
Node: Style Checking353731
Ref: gnat_ugn/building_executable_programs_with_gnat id18353851
Ref: 10b353851
Ref: gnat_ugn/building_executable_programs_with_gnat style-checking353851
Ref: 103353851
Node: Run-Time Checks370160
Ref: gnat_ugn/building_executable_programs_with_gnat run-time-checks370292
Ref: 101370292
Ref: gnat_ugn/building_executable_programs_with_gnat id19370292
Ref: 10c370292
Node: Using gcc for Syntax Checking376813
Ref: gnat_ugn/building_executable_programs_with_gnat id20376962
Ref: 10d376962
Ref: gnat_ugn/building_executable_programs_with_gnat using-gcc-for-syntax-checking376962
Ref: 10e376962
Node: Using gcc for Semantic Checking378578
Ref: gnat_ugn/building_executable_programs_with_gnat id21378747
Ref: 10f378747
Ref: gnat_ugn/building_executable_programs_with_gnat using-gcc-for-semantic-checking378747
Ref: 110378747
Node: Compiling Different Versions of Ada380082
Ref: gnat_ugn/building_executable_programs_with_gnat compiling-different-versions-of-ada380243
Ref: 6380243
Ref: gnat_ugn/building_executable_programs_with_gnat id22380243
Ref: 111380243
Node: Character Set Control383866
Ref: gnat_ugn/building_executable_programs_with_gnat id23384015
Ref: 112384015
Ref: gnat_ugn/building_executable_programs_with_gnat character-set-control384015
Ref: 4a384015
Node: File Naming Control388621
Ref: gnat_ugn/building_executable_programs_with_gnat file-naming-control388762
Ref: 113388762
Ref: gnat_ugn/building_executable_programs_with_gnat id24388762
Ref: 114388762
Node: Subprogram Inlining Control389147
Ref: gnat_ugn/building_executable_programs_with_gnat subprogram-inlining-control389291
Ref: 115389291
Ref: gnat_ugn/building_executable_programs_with_gnat id25389291
Ref: 116389291
Node: Auxiliary Output Control391106
Ref: gnat_ugn/building_executable_programs_with_gnat auxiliary-output-control391248
Ref: 118391248
Ref: gnat_ugn/building_executable_programs_with_gnat id26391248
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Node: Debugging Control392682
Ref: gnat_ugn/building_executable_programs_with_gnat debugging-control392823
Ref: 11a392823
Ref: gnat_ugn/building_executable_programs_with_gnat id27392823
Ref: 11b392823
Node: Exception Handling Control402595
Ref: gnat_ugn/building_executable_programs_with_gnat id28402742
Ref: 11c402742
Ref: gnat_ugn/building_executable_programs_with_gnat exception-handling-control402742
Ref: 11d402742
Node: Units to Sources Mapping Files405367
Ref: gnat_ugn/building_executable_programs_with_gnat id29405520
Ref: 11e405520
Ref: gnat_ugn/building_executable_programs_with_gnat units-to-sources-mapping-files405520
Ref: ff405520
Node: Code Generation Control407418
Ref: gnat_ugn/building_executable_programs_with_gnat code-generation-control407536
Ref: 11f407536
Ref: gnat_ugn/building_executable_programs_with_gnat id30407536
Ref: 120407536
Node: Binding with gnatbind408680
Ref: gnat_ugn/building_executable_programs_with_gnat binding-with-gnatbind408834
Ref: 1f408834
Ref: gnat_ugn/building_executable_programs_with_gnat id31408834
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Node: Running gnatbind410460
Ref: gnat_ugn/building_executable_programs_with_gnat running-gnatbind410566
Ref: 123410566
Ref: gnat_ugn/building_executable_programs_with_gnat id32410566
Ref: 124410566
Node: Switches for gnatbind413462
Ref: gnat_ugn/building_executable_programs_with_gnat id33413596
Ref: 125413596
Ref: gnat_ugn/building_executable_programs_with_gnat switches-for-gnatbind413596
Ref: 126413596
Node: Consistency-Checking Modes424592
Ref: gnat_ugn/building_executable_programs_with_gnat consistency-checking-modes424715
Ref: 129424715
Ref: gnat_ugn/building_executable_programs_with_gnat id34424715
Ref: 12a424715
Node: Binder Error Message Control426497
Ref: gnat_ugn/building_executable_programs_with_gnat id35426648
Ref: 12b426648
Ref: gnat_ugn/building_executable_programs_with_gnat binder-error-message-control426648
Ref: 12c426648
Node: Elaboration Control428802
Ref: gnat_ugn/building_executable_programs_with_gnat id36428941
Ref: 12d428941
Ref: gnat_ugn/building_executable_programs_with_gnat elaboration-control428941
Ref: 12e428941
Node: Output Control430165
Ref: gnat_ugn/building_executable_programs_with_gnat output-control430302
Ref: 12f430302
Ref: gnat_ugn/building_executable_programs_with_gnat id37430302
Ref: 130430302
Node: Dynamic Allocation Control432203
Ref: gnat_ugn/building_executable_programs_with_gnat dynamic-allocation-control432355
Ref: 127432355
Ref: gnat_ugn/building_executable_programs_with_gnat id38432355
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Node: Binding with Non-Ada Main Programs432942
Ref: gnat_ugn/building_executable_programs_with_gnat binding-with-non-ada-main-programs433120
Ref: ba433120
Ref: gnat_ugn/building_executable_programs_with_gnat id39433120
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Node: Binding Programs with No Main Subprogram436072
Ref: gnat_ugn/building_executable_programs_with_gnat binding-programs-with-no-main-subprogram436215
Ref: 133436215
Ref: gnat_ugn/building_executable_programs_with_gnat id40436215
Ref: 134436215
Node: Command-Line Access437078
Ref: gnat_ugn/building_executable_programs_with_gnat id41437221
Ref: 135437221
Ref: gnat_ugn/building_executable_programs_with_gnat command-line-access437221
Ref: 136437221
Node: Search Paths for gnatbind438084
Ref: gnat_ugn/building_executable_programs_with_gnat search-paths-for-gnatbind438232
Ref: 91438232
Ref: gnat_ugn/building_executable_programs_with_gnat id42438232
Ref: 137438232
Node: Examples of gnatbind Usage440955
Ref: gnat_ugn/building_executable_programs_with_gnat examples-of-gnatbind-usage441075
Ref: 138441075
Ref: gnat_ugn/building_executable_programs_with_gnat id43441075
Ref: 139441075
Node: Linking with gnatlink441880
Ref: gnat_ugn/building_executable_programs_with_gnat id44442043
Ref: 13a442043
Ref: gnat_ugn/building_executable_programs_with_gnat linking-with-gnatlink442043
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Node: Running gnatlink442681
Ref: gnat_ugn/building_executable_programs_with_gnat id45442787
Ref: 13b442787
Ref: gnat_ugn/building_executable_programs_with_gnat running-gnatlink442787
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Node: Switches for gnatlink445136
Ref: gnat_ugn/building_executable_programs_with_gnat id46445242
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Ref: gnat_ugn/building_executable_programs_with_gnat switches-for-gnatlink445242
Ref: 140445242
Node: Using the GNU make Utility449907
Ref: gnat_ugn/building_executable_programs_with_gnat id47450040
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Ref: gnat_ugn/building_executable_programs_with_gnat using-the-gnu-make-utility450040
Ref: 21450040
Node: Using gnatmake in a Makefile450710
Ref: gnat_ugn/building_executable_programs_with_gnat using-gnatmake-in-a-makefile450856
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Ref: gnat_ugn/building_executable_programs_with_gnat id48450856
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Node: Automatically Creating a List of Directories454814
Ref: gnat_ugn/building_executable_programs_with_gnat automatically-creating-a-list-of-directories455005
Ref: 144455005
Ref: gnat_ugn/building_executable_programs_with_gnat id49455005
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Node: Generating the Command Line Switches457906
Ref: gnat_ugn/building_executable_programs_with_gnat id50458106
Ref: 146458106
Ref: gnat_ugn/building_executable_programs_with_gnat generating-the-command-line-switches458106
Ref: 147458106
Node: Overcoming Command Line Length Limits458876
Ref: gnat_ugn/building_executable_programs_with_gnat overcoming-command-line-length-limits459023
Ref: 148459023
Ref: gnat_ugn/building_executable_programs_with_gnat id51459023
Ref: 149459023
Node: GNAT Project Manager461295
Ref: gnat_ugn/gnat_project_manager doc461443
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Ref: gnat_ugn/gnat_project_manager gnat-project-manager461443
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Ref: gnat_ugn/gnat_project_manager id1461443
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Node: Introduction461734
Ref: gnat_ugn/gnat_project_manager introduction461836
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Ref: gnat_ugn/gnat_project_manager gnat-project-manager-introduction461836
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Node: Building With Projects465557
Ref: gnat_ugn/gnat_project_manager building-with-projects465703
Ref: 153465703
Ref: gnat_ugn/gnat_project_manager id2465703
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Node: Source Files and Directories470549
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Ref: gnat_ugn/gnat_project_manager source-files-and-directories470676
Ref: 15a470676
Node: Duplicate Sources in Projects478494
Ref: gnat_ugn/gnat_project_manager duplicate-sources-in-projects478655
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Ref: gnat_ugn/gnat_project_manager id4478655
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Node: Object and Exec Directory479681
Ref: gnat_ugn/gnat_project_manager object-and-exec-directory479830
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Ref: gnat_ugn/gnat_project_manager id5479830
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Node: Main Subprograms482523
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Ref: gnat_ugn/gnat_project_manager main-subprograms482673
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Node: Tools Options in Project Files484400
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Node: Compiling with Project Files490212
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Node: Executable File Names492287
Ref: gnat_ugn/gnat_project_manager executable-file-names492447
Ref: 165492447
Ref: gnat_ugn/gnat_project_manager id9492447
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Node: Avoid Duplication With Variables493606
Ref: gnat_ugn/gnat_project_manager id10493752
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Ref: gnat_ugn/gnat_project_manager avoid-duplication-with-variables493752
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Node: Naming Schemes495842
Ref: gnat_ugn/gnat_project_manager id11495979
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Ref: gnat_ugn/gnat_project_manager naming-schemes495979
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Node: Installation502475
Ref: gnat_ugn/gnat_project_manager id12502599
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Node: Distributed support504396
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Ref: gnat_ugn/gnat_project_manager organizing-projects-into-subsystems505033
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Ref: gnat_ugn/gnat_project_manager id16511976
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Ref: gnat_ugn/gnat_project_manager cyclic-project-dependencies511976
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Node: Sharing Between Projects513157
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Node: Scenarios in Projects518785
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Ref: gnat_ugn/gnat_project_manager library-projects523489
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Ref: gnat_ugn/gnat_project_manager id20523489
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Ref: gnat_ugn/gnat_project_manager id21525124
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Node: Using Library Projects531508
Ref: gnat_ugn/gnat_project_manager id22531649
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Node: Installing a library with project files543509
Ref: gnat_ugn/gnat_project_manager installing-a-library-with-project-files543640
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Ref: gnat_ugn/gnat_project_manager aggregate-projects554242
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Ref: gnat_ugn/gnat_project_manager id30558480
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Ref: gnat_ugn/gnat_project_manager performance-improvements-in-builder560483
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Ref: gnat_ugn/gnat_project_manager id31560483
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Ref: gnat_ugn/gnat_project_manager id32561444
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Node: package Builder in aggregate projects569746
Ref: gnat_ugn/gnat_project_manager package-builder-in-aggregate-projects569877
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Ref: gnat_ugn/gnat_project_manager id33569877
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Node: Aggregate Library Projects574428
Ref: gnat_ugn/gnat_project_manager id34574571
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Node: Building aggregate library projects575151
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Ref: gnat_ugn/gnat_project_manager id35575296
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Node: Syntax of aggregate library projects576661
Ref: gnat_ugn/gnat_project_manager syntax-of-aggregate-library-projects576806
Ref: 195576806
Ref: gnat_ugn/gnat_project_manager id36576806
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Node: Project File Reference578246
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Ref: gnat_ugn/gnat_project_manager project-file-reference578362
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Node: Project Declaration578789
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Ref: gnat_ugn/gnat_and_program_execution id59829966
Ref: 253829966
Node: Performing Dimensionality Analysis in GNAT832048
Ref: gnat_ugn/gnat_and_program_execution performing-dimensionality-analysis-in-gnat832228
Ref: 2a832228
Ref: gnat_ugn/gnat_and_program_execution id60832228
Ref: 1f7832228
Node: Stack Related Facilities837246
Ref: gnat_ugn/gnat_and_program_execution id61837419
Ref: 1f8837419
Ref: gnat_ugn/gnat_and_program_execution stack-related-facilities837419
Ref: 2b837419
Node: Stack Overflow Checking837742
Ref: gnat_ugn/gnat_and_program_execution id62837864
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Ref: gnat_ugn/gnat_and_program_execution stack-overflow-checking837864
Ref: fc837864
Node: Static Stack Usage Analysis840128
Ref: gnat_ugn/gnat_and_program_execution static-stack-usage-analysis840287
Ref: fd840287
Ref: gnat_ugn/gnat_and_program_execution id63840287
Ref: 255840287
Node: Dynamic Stack Usage Analysis841649
Ref: gnat_ugn/gnat_and_program_execution id64841776
Ref: 256841776
Ref: gnat_ugn/gnat_and_program_execution dynamic-stack-usage-analysis841776
Ref: 128841776
Node: Memory Management Issues843219
Ref: gnat_ugn/gnat_and_program_execution id65843341
Ref: 1f9843341
Ref: gnat_ugn/gnat_and_program_execution memory-management-issues843341
Ref: 2c843341
Node: Some Useful Memory Pools843693
Ref: gnat_ugn/gnat_and_program_execution id66843817
Ref: 257843817
Ref: gnat_ugn/gnat_and_program_execution some-useful-memory-pools843817
Ref: 258843817
Node: The GNAT Debug Pool Facility846402
Ref: gnat_ugn/gnat_and_program_execution id67846526
Ref: 259846526
Ref: gnat_ugn/gnat_and_program_execution the-gnat-debug-pool-facility846526
Ref: 25a846526
Node: Platform-Specific Information851411
Ref: gnat_ugn/platform_specific_information platform-specific-information851555
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Ref: gnat_ugn/platform_specific_information doc851555
Ref: 25b851555
Ref: gnat_ugn/platform_specific_information id1851555
Ref: 25c851555
Node: Run-Time Libraries851925
Ref: gnat_ugn/platform_specific_information id2852049
Ref: 25d852049
Ref: gnat_ugn/platform_specific_information run-time-libraries852049
Ref: 2d852049
Node: Summary of Run-Time Configurations853410
Ref: gnat_ugn/platform_specific_information summary-of-run-time-configurations853501
Ref: 25e853501
Ref: gnat_ugn/platform_specific_information id3853501
Ref: 25f853501
Node: Specifying a Run-Time Library855654
Ref: gnat_ugn/platform_specific_information specifying-a-run-time-library855811
Ref: 260855811
Ref: gnat_ugn/platform_specific_information id4855811
Ref: 261855811
Ref: gnat_ugn/platform_specific_information choosing-the-scheduling-policy857715
Ref: 262857715
Node: Choosing the Scheduling Policy857857
Ref: gnat_ugn/platform_specific_information id5857995
Ref: 263857995
Node: Solaris-Specific Considerations858719
Ref: gnat_ugn/platform_specific_information id6858888
Ref: 264858888
Ref: gnat_ugn/platform_specific_information solaris-specific-considerations858888
Ref: 265858888
Node: Solaris Threads Issues859060
Ref: gnat_ugn/platform_specific_information id7859226
Ref: 266859226
Ref: gnat_ugn/platform_specific_information solaris-threads-issues859226
Ref: 267859226
Node: AIX-Specific Considerations861085
Ref: gnat_ugn/platform_specific_information aix-specific-considerations861211
Ref: 268861211
Ref: gnat_ugn/platform_specific_information id8861211
Ref: 269861211
Node: Microsoft Windows Topics861915
Ref: gnat_ugn/platform_specific_information microsoft-windows-topics862067
Ref: 2e862067
Ref: gnat_ugn/platform_specific_information id9862067
Ref: 26a862067
Node: Using GNAT on Windows862414
Ref: gnat_ugn/platform_specific_information using-gnat-on-windows862543
Ref: 26b862543
Ref: gnat_ugn/platform_specific_information id10862543
Ref: 26c862543
Node: Using a network installation of GNAT865301
Ref: gnat_ugn/platform_specific_information id11865469
Ref: 26d865469
Ref: gnat_ugn/platform_specific_information using-a-network-installation-of-gnat865469
Ref: 26e865469
Node: CONSOLE and WINDOWS subsystems866345
Ref: gnat_ugn/platform_specific_information id12866507
Ref: 26f866507
Ref: gnat_ugn/platform_specific_information console-and-windows-subsystems866507
Ref: 270866507
Node: Temporary Files867004
Ref: gnat_ugn/platform_specific_information id13867167
Ref: 271867167
Ref: gnat_ugn/platform_specific_information temporary-files867167
Ref: 272867167
Node: Mixed-Language Programming on Windows867825
Ref: gnat_ugn/platform_specific_information mixed-language-programming-on-windows867982
Ref: 273867982
Ref: gnat_ugn/platform_specific_information id14867982
Ref: 274867982
Node: Windows Calling Conventions870505
Ref: gnat_ugn/platform_specific_information windows-calling-conventions870660
Ref: 277870660
Ref: gnat_ugn/platform_specific_information id15870660
Ref: 278870660
Node: C Calling Convention871540
Ref: gnat_ugn/platform_specific_information c-calling-convention871661
Ref: 279871661
Ref: gnat_ugn/platform_specific_information id16871661
Ref: 27a871661
Node: Stdcall Calling Convention873094
Ref: gnat_ugn/platform_specific_information stdcall-calling-convention873248
Ref: 27b873248
Ref: gnat_ugn/platform_specific_information id17873248
Ref: 27c873248
Node: Win32 Calling Convention875956
Ref: gnat_ugn/platform_specific_information id18876112
Ref: 27d876112
Ref: gnat_ugn/platform_specific_information win32-calling-convention876112
Ref: 27e876112
Node: DLL Calling Convention876297
Ref: gnat_ugn/platform_specific_information id19876418
Ref: 27f876418
Ref: gnat_ugn/platform_specific_information dll-calling-convention876418
Ref: 280876418
Node: Introduction to Dynamic Link Libraries DLLs876599
Ref: gnat_ugn/platform_specific_information id20876783
Ref: 281876783
Ref: gnat_ugn/platform_specific_information introduction-to-dynamic-link-libraries-dlls876783
Ref: 282876783
Node: Using DLLs with GNAT880108
Ref: gnat_ugn/platform_specific_information id21880302
Ref: 284880302
Ref: gnat_ugn/platform_specific_information using-dlls-with-gnat880302
Ref: 275880302
Node: Creating an Ada Spec for the DLL Services882194
Ref: gnat_ugn/platform_specific_information creating-an-ada-spec-for-the-dll-services882329
Ref: 285882329
Ref: gnat_ugn/platform_specific_information id22882329
Ref: 286882329
Node: Creating an Import Library883272
Ref: gnat_ugn/platform_specific_information id23883407
Ref: 287883407
Ref: gnat_ugn/platform_specific_information creating-an-import-library883407
Ref: 288883407
Ref: gnat_ugn/platform_specific_information the-definition-file883808
Ref: 283883808
Ref: gnat_ugn/platform_specific_information create-def-file-automatically885072
Ref: 289885072
Ref: gnat_ugn/platform_specific_information gnat-style-import-library886188
Ref: 28a886188
Ref: gnat_ugn/platform_specific_information msvs-style-import-library887082
Ref: 28c887082
Node: Building DLLs with GNAT Project files887783
Ref: gnat_ugn/platform_specific_information id24887957
Ref: 28d887957
Ref: gnat_ugn/platform_specific_information building-dlls-with-gnat-project-files887957
Ref: 276887957
Node: Building DLLs with GNAT888373
Ref: gnat_ugn/platform_specific_information building-dlls-with-gnat888553
Ref: 28e888553
Ref: gnat_ugn/platform_specific_information id25888553
Ref: 28f888553
Node: Building DLLs with gnatdll890412
Ref: gnat_ugn/platform_specific_information building-dlls-with-gnatdll890580
Ref: 290890580
Ref: gnat_ugn/platform_specific_information id26890580
Ref: 291890580
Node: Limitations When Using Ada DLLs from Ada892943
Ref: gnat_ugn/platform_specific_information limitations-when-using-ada-dlls-from-ada893079
Ref: 295893079
Node: Exporting Ada Entities893984
Ref: gnat_ugn/platform_specific_information exporting-ada-entities894153
Ref: 292894153
Ref: gnat_ugn/platform_specific_information id27894153
Ref: 296894153
Node: Ada DLLs and Elaboration896955
Ref: gnat_ugn/platform_specific_information ada-dlls-and-elaboration897075
Ref: 293897075
Ref: gnat_ugn/platform_specific_information id28897075
Ref: 298897075
Node: Ada DLLs and Finalization898464
Ref: gnat_ugn/platform_specific_information id29898637
Ref: 299898637
Ref: gnat_ugn/platform_specific_information ada-dlls-and-finalization898637
Ref: 294898637
Node: Creating a Spec for Ada DLLs899294
Ref: gnat_ugn/platform_specific_information id30899467
Ref: 29a899467
Ref: gnat_ugn/platform_specific_information creating-a-spec-for-ada-dlls899467
Ref: 29b899467
Node: Creating the Definition File900834
Ref: gnat_ugn/platform_specific_information creating-the-definition-file900951
Ref: 297900951
Ref: gnat_ugn/platform_specific_information id31900951
Ref: 29c900951
Node: Using gnatdll901682
Ref: gnat_ugn/platform_specific_information using-gnatdll901799
Ref: 28b901799
Ref: gnat_ugn/platform_specific_information id32901799
Ref: 29d901799
Ref: gnat_ugn/platform_specific_information using-dlltool907971
Ref: 29e907971
Node: GNAT and Windows Resources909224
Ref: gnat_ugn/platform_specific_information gnat-and-windows-resources909429
Ref: 29f909429
Ref: gnat_ugn/platform_specific_information id33909429
Ref: 2a0909429
Node: Building Resources911287
Ref: gnat_ugn/platform_specific_information building-resources911398
Ref: 2a1911398
Ref: gnat_ugn/platform_specific_information id34911398
Ref: 2a2911398
Node: Compiling Resources911958
Ref: gnat_ugn/platform_specific_information compiling-resources912093
Ref: 2a3912093
Ref: gnat_ugn/platform_specific_information id35912093
Ref: 2a4912093
Node: Using Resources912972
Ref: gnat_ugn/platform_specific_information id36913080
Ref: 2a5913080
Ref: gnat_ugn/platform_specific_information using-resources913080
Ref: 2a6913080
Node: Using GNAT DLLs from Microsoft Visual Studio Applications913365
Ref: gnat_ugn/platform_specific_information using-gnat-dll-from-msvs913557
Ref: 2a7913557
Ref: gnat_ugn/platform_specific_information using-gnat-dlls-from-microsoft-visual-studio-applications913557
Ref: 2a8913557
Node: Debugging a DLL915104
Ref: gnat_ugn/platform_specific_information id37915302
Ref: 2a9915302
Ref: gnat_ugn/platform_specific_information debugging-a-dll915302
Ref: 2aa915302
Node: Program and DLL Both Built with GCC/GNAT916171
Ref: gnat_ugn/platform_specific_information program-and-dll-both-built-with-gcc-gnat916334
Ref: 2ab916334
Ref: gnat_ugn/platform_specific_information id38916334
Ref: 2ac916334
Node: Program Built with Foreign Tools and DLL Built with GCC/GNAT917640
Ref: gnat_ugn/platform_specific_information program-built-with-foreign-tools-and-dll-built-with-gcc-gnat917803
Ref: 2ad917803
Ref: gnat_ugn/platform_specific_information id39917803
Ref: 2ae917803
Node: Setting Stack Size from gnatlink921139
Ref: gnat_ugn/platform_specific_information setting-stack-size-from-gnatlink921311
Ref: 13d921311
Ref: gnat_ugn/platform_specific_information id40921311
Ref: 2af921311
Node: Setting Heap Size from gnatlink922497
Ref: gnat_ugn/platform_specific_information setting-heap-size-from-gnatlink922645
Ref: 13e922645
Ref: gnat_ugn/platform_specific_information id41922645
Ref: 2b0922645
Node: Windows Specific Add-Ons923308
Ref: gnat_ugn/platform_specific_information windows-specific-add-ons923441
Ref: 2b1923441
Ref: gnat_ugn/platform_specific_information win32-specific-addons923441
Ref: 2b2923441
Node: Win32Ada923592
Ref: gnat_ugn/platform_specific_information win32ada923678
Ref: 2b3923678
Ref: gnat_ugn/platform_specific_information id42923678
Ref: 2b4923678
Node: wPOSIX924267
Ref: gnat_ugn/platform_specific_information id43924353
Ref: 2b5924353
Ref: gnat_ugn/platform_specific_information wposix924353
Ref: 2b6924353
Node: Mac OS Topics925029
Ref: gnat_ugn/platform_specific_information mac-os-topics925143
Ref: 2f925143
Ref: gnat_ugn/platform_specific_information id44925143
Ref: 2b7925143
Node: Codesigning the Debugger925294
Ref: gnat_ugn/platform_specific_information codesigning-the-debugger925370
Ref: 2b8925370
Node: Example of Binder Output File927292
Ref: gnat_ugn/example_of_binder_output example-of-binder-output-file927444
Ref: 10927444
Ref: gnat_ugn/example_of_binder_output doc927444
Ref: 2b9927444
Ref: gnat_ugn/example_of_binder_output id1927444
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Node: Elaboration Order Handling in GNAT957873
Ref: gnat_ugn/elaboration_order_handling_in_gnat elaboration-order-handling-in-gnat958012
Ref: 11958012
Ref: gnat_ugn/elaboration_order_handling_in_gnat doc958012
Ref: 2bb958012
Ref: gnat_ugn/elaboration_order_handling_in_gnat id1958012
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Node: Elaboration Code958906
Ref: gnat_ugn/elaboration_order_handling_in_gnat elaboration-code959034
Ref: 2bd959034
Ref: gnat_ugn/elaboration_order_handling_in_gnat id2959034
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Node: Checking the Elaboration Order963503
Ref: gnat_ugn/elaboration_order_handling_in_gnat checking-the-elaboration-order963673
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Ref: gnat_ugn/elaboration_order_handling_in_gnat id3963673
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Node: Controlling the Elaboration Order967479
Ref: gnat_ugn/elaboration_order_handling_in_gnat id4967681
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Ref: gnat_ugn/elaboration_order_handling_in_gnat id6982094
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Node: Default Behavior in GNAT - Ensuring Safety985543
Ref: gnat_ugn/elaboration_order_handling_in_gnat id7985753
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Node: Treatment of Pragma Elaborate990223
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Ref: gnat_ugn/elaboration_order_handling_in_gnat id8990421
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Node: Elaboration Issues for Library Tasks992071
Ref: gnat_ugn/elaboration_order_handling_in_gnat elaboration-issues-for-library-tasks992252
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Ref: gnat_ugn/elaboration_order_handling_in_gnat id9992252
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Node: Mixing Elaboration Models1004946
Ref: gnat_ugn/elaboration_order_handling_in_gnat id101005150
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Ref: gnat_ugn/elaboration_order_handling_in_gnat mixing-elaboration-models1005150
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Node: What to Do If the Default Elaboration Behavior Fails1007436
Ref: gnat_ugn/elaboration_order_handling_in_gnat id111007634
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Ref: gnat_ugn/elaboration_order_handling_in_gnat what-to-do-if-the-default-elaboration-behavior-fails1007634
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Ref: gnat_ugn/elaboration_order_handling_in_gnat id141021045
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Node: Determining the Chosen Elaboration Order1026494
Ref: gnat_ugn/elaboration_order_handling_in_gnat determining-the-chosen-elaboration-order1026654
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Node: Inline Assembler1030585
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Ref: gnat_ugn/inline_assembler basic-assembler-syntax1032387
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Ref: gnat_ugn/inline_assembler other-asm-functionality1049806
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Ref: gnat_ugn/inline_assembler id81050218
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Ref: gnat_ugn/inline_assembler the-volatile-parameter1052243
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Ref: gnat_ugn/inline_assembler id91052243
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Node: GNU Free Documentation License1053346
Ref: share/gnu_free_documentation_license gnu-fdl1053457
Ref: 11053457
Ref: share/gnu_free_documentation_license doc1053457
Ref: 2eb1053457
Ref: share/gnu_free_documentation_license gnu-free-documentation-license1053457
Ref: 2ec1053457
Node: Index1076579

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