This is g77.info, produced by makeinfo version 4.0 from g77.texi.

INFO-DIR-SECTION Programming
START-INFO-DIR-ENTRY
* g77: (g77).                  The GNU Fortran compiler.
END-INFO-DIR-ENTRY
   This file documents the use and the internals of the GNU Fortran
(`g77') compiler.  It corresponds to the GCC-3.0 version of `g77'.

   Published by the Free Software Foundation 59 Temple Place - Suite 330
Boston, MA 02111-1307 USA

   Copyright (C) 1995,1996,1997,1998,1999,2000,2001 Free Software
Foundation, Inc.

   Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.1 or
any later version published by the Free Software Foundation; with the
Invariant Sections being "GNU General Public License" and "Funding Free
Software", the Front-Cover texts being (a) (see below), and with the
Back-Cover Texts being (b) (see below).  A copy of the license is
included in the section entitled "GNU Free Documentation License".

   (a) The FSF's Front-Cover Text is:

   A GNU Manual

   (b) The FSF's Back-Cover Text is:

   You have freedom to copy and modify this GNU Manual, like GNU
software.  Copies published by the Free Software Foundation raise
funds for GNU development.

   Contributed by James Craig Burley (<craig@jcb-sc.com>).  Inspired by
a first pass at translating `g77-0.5.16/f/DOC' that was contributed to
Craig by David Ronis (<ronis@onsager.chem.mcgill.ca>).


File: g77.info,  Node: Getting Started,  Next: What is GNU Fortran?,  Prev: Funding GNU Fortran,  Up: Top

Getting Started
***************

   If you don't need help getting started reading the portions of this
manual that are most important to you, you should skip this portion of
the manual.

   If you are new to compilers, especially Fortran compilers, or new to
how compilers are structured under UNIX and UNIX-like systems, you'll
want to see *Note What is GNU Fortran?::.

   If you are new to GNU compilers, or have used only one GNU compiler
in the past and not had to delve into how it lets you manage various
versions and configurations of `gcc', you should see *Note G77 and
GCC::.

   Everyone except experienced `g77' users should see *Note Invoking
G77::.

   If you're acquainted with previous versions of `g77', you should see
*Note News About GNU Fortran: News.  Further, if you've actually used
previous versions of `g77', especially if you've written or modified
Fortran code to be compiled by previous versions of `g77', you should
see *Note Changes::.

   If you intend to write or otherwise compile code that is not already
strictly conforming ANSI FORTRAN 77--and this is probably everyone--you
should see *Note Language::.

   If you don't already have `g77' installed on your system, you must
see *Note Installation::.

   If you run into trouble getting Fortran code to compile, link, run,
or work properly, you might find answers if you see *Note Debugging and
Interfacing::, see *Note Collected Fortran Wisdom::, and see *Note
Trouble::.  You might also find that the problems you are encountering
are bugs in `g77'--see *Note Bugs::, for information on reporting them,
after reading the other material.

   If you need further help with `g77', or with freely redistributable
software in general, see *Note Service::.

   If you would like to help the `g77' project, see *Note Funding GNU
Fortran::, for information on helping financially, and see *Note
Projects::, for information on helping in other ways.

   If you're generally curious about the future of `g77', see *Note
Projects::.  If you're curious about its past, see *Note Contributors::,
and see *Note Funding GNU Fortran::.

   To see a few of the questions maintainers of `g77' have, and that
you might be able to answer, see *Note Open Questions::.


File: g77.info,  Node: What is GNU Fortran?,  Next: G77 and GCC,  Prev: Getting Started,  Up: Top

What is GNU Fortran?
********************

   GNU Fortran, or `g77', is designed initially as a free replacement
for, or alternative to, the UNIX `f77' command.  (Similarly, `gcc' is
designed as a replacement for the UNIX `cc' command.)

   `g77' also is designed to fit in well with the other fine GNU
compilers and tools.

   Sometimes these design goals conflict--in such cases, resolution
often is made in favor of fitting in well with Project GNU.  These
cases are usually identified in the appropriate sections of this manual.

   As compilers, `g77', `gcc', and `f77' share the following
characteristics:

   * They read a user's program, stored in a file and containing
     instructions written in the appropriate language (Fortran, C, and
     so on).  This file contains "source code".

   * They translate the user's program into instructions a computer can
     carry out more quickly than it takes to translate the instructions
     in the first place.  These instructions are called "machine
     code"--code designed to be efficiently translated and processed by
     a machine such as a computer.  Humans usually aren't as good
     writing machine code as they are at writing Fortran or C, because
     it is easy to make tiny mistakes writing machine code.  When
     writing Fortran or C, it is easy to make big mistakes.

   * They provide information in the generated machine code that can
     make it easier to find bugs in the program (using a debugging
     tool, called a "debugger", such as `gdb').

   * They locate and gather machine code already generated to perform
     actions requested by statements in the user's program.  This
     machine code is organized into "libraries" and is located and
     gathered during the "link" phase of the compilation process.
     (Linking often is thought of as a separate step, because it can be
     directly invoked via the `ld' command.  However, the `g77' and
     `gcc' commands, as with most compiler commands, automatically
     perform the linking step by calling on `ld' directly, unless asked
     to not do so by the user.)

   * They attempt to diagnose cases where the user's program contains
     incorrect usages of the language.  The "diagnostics" produced by
     the compiler indicate the problem and the location in the user's
     source file where the problem was first noticed.  The user can use
     this information to locate and fix the problem.  (Sometimes an
     incorrect usage of the language leads to a situation where the
     compiler can no longer make any sense of what follows--while a
     human might be able to--and thus ends up complaining about many
     "problems" it encounters that, in fact, stem from just one
     problem, usually the first one reported.)

   * They attempt to diagnose cases where the user's program contains a
     correct usage of the language, but instructs the computer to do
     something questionable.  These diagnostics often are in the form
     of "warnings", instead of the "errors" that indicate incorrect
     usage of the language.

   How these actions are performed is generally under the control of
the user.  Using command-line options, the user can specify how
persnickety the compiler is to be regarding the program (whether to
diagnose questionable usage of the language), how much time to spend
making the generated machine code run faster, and so on.

   `g77' consists of several components:

   * A modified version of the `gcc' command, which also might be
     installed as the system's `cc' command.  (In many cases, `cc'
     refers to the system's "native" C compiler, which might be a
     non-GNU compiler, or an older version of `gcc' considered more
     stable or that is used to build the operating system kernel.)

   * The `g77' command itself, which also might be installed as the
     system's `f77' command.

   * The `libg2c' run-time library.  This library contains the machine
     code needed to support capabilities of the Fortran language that
     are not directly provided by the machine code generated by the
     `g77' compilation phase.

     `libg2c' is just the unique name `g77' gives to its version of
     `libf2c' to distinguish it from any copy of `libf2c' installed
     from `f2c' (or versions of `g77' that built `libf2c' under that
     same name) on the system.

     The maintainer of `libf2c' currently is <dmg@bell-labs.com>.

   * The compiler itself, internally named `f771'.

     Note that `f771' does not generate machine code directly--it
     generates "assembly code" that is a more readable form of machine
     code, leaving the conversion to actual machine code to an
     "assembler", usually named `as'.

   `gcc' is often thought of as "the C compiler" only, but it does more
than that.  Based on command-line options and the names given for files
on the command line, `gcc' determines which actions to perform,
including preprocessing, compiling (in a variety of possible
languages), assembling, and linking.

   For example, the command `gcc foo.c' "drives" the file `foo.c'
through the preprocessor `cpp', then the C compiler (internally named
`cc1'), then the assembler (usually `as'), then the linker (`ld'),
producing an executable program named `a.out' (on UNIX systems).

   As another example, the command `gcc foo.cc' would do much the same
as `gcc foo.c', but instead of using the C compiler named `cc1', `gcc'
would use the C++ compiler (named `cc1plus').

   In a GNU Fortran installation, `gcc' recognizes Fortran source files
by name just like it does C and C++ source files.  It knows to use the
Fortran compiler named `f771', instead of `cc1' or `cc1plus', to
compile Fortran files.

   Non-Fortran-related operation of `gcc' is generally unaffected by
installing the GNU Fortran version of `gcc'.  However, without the
installed version of `gcc' being the GNU Fortran version, `gcc' will
not be able to compile and link Fortran programs--and since `g77' uses
`gcc' to do most of the actual work, neither will `g77'!

   The `g77' command is essentially just a front-end for the `gcc'
command.  Fortran users will normally use `g77' instead of `gcc',
because `g77' knows how to specify the libraries needed to link with
Fortran programs (`libg2c' and `lm').  `g77' can still compile and link
programs and source files written in other languages, just like `gcc'.

   The command `g77 -v' is a quick way to display lots of version
information for the various programs used to compile a typical
preprocessed Fortran source file--this produces much more output than
`gcc -v' currently does.  (If it produces an error message near the end
of the output--diagnostics from the linker, usually `ld'--you might
have an out-of-date `libf2c' that improperly handles complex
arithmetic.)  In the output of this command, the line beginning `GNU
Fortran Front End' identifies the version number of GNU Fortran;
immediately preceding that line is a line identifying the version of
`gcc' with which that version of `g77' was built.

   The `libf2c' library is distributed with GNU Fortran for the
convenience of its users, but is not part of GNU Fortran.  It contains
the procedures needed by Fortran programs while they are running.

   For example, while code generated by `g77' is likely to do
additions, subtractions, and multiplications "in line"--in the actual
compiled code--it is not likely to do trigonometric functions this way.

   Instead, operations like trigonometric functions are compiled by the
`f771' compiler (invoked by `g77' when compiling Fortran code) into
machine code that, when run, calls on functions in `libg2c', so
`libg2c' must be linked with almost every useful program having any
component compiled by GNU Fortran.  (As mentioned above, the `g77'
command takes care of all this for you.)

   The `f771' program represents most of what is unique to GNU Fortran.
While much of the `libg2c' component comes from the `libf2c' component
of `f2c', a free Fortran-to-C converter distributed by Bellcore (AT&T),
plus `libU77', provided by Dave Love, and the `g77' command is just a
small front-end to `gcc', `f771' is a combination of two rather large
chunks of code.

   One chunk is the so-called "GNU Back End", or GBE, which knows how
to generate fast code for a wide variety of processors.  The same GBE
is used by the C, C++, and Fortran compiler programs `cc1', `cc1plus',
and `f771', plus others.  Often the GBE is referred to as the "gcc back
end" or even just "gcc"--in this manual, the term GBE is used whenever
the distinction is important.

   The other chunk of `f771' is the majority of what is unique about
GNU Fortran--the code that knows how to interpret Fortran programs to
determine what they are intending to do, and then communicate that
knowledge to the GBE for actual compilation of those programs.  This
chunk is called the "Fortran Front End" (FFE).  The `cc1' and `cc1plus'
programs have their own front ends, for the C and C++ languages,
respectively.  These fronts ends are responsible for diagnosing
incorrect usage of their respective languages by the programs the
process, and are responsible for most of the warnings about
questionable constructs as well.  (The GBE handles producing some
warnings, like those concerning possible references to undefined
variables.)

   Because so much is shared among the compilers for various languages,
much of the behavior and many of the user-selectable options for these
compilers are similar.  For example, diagnostics (error messages and
warnings) are similar in appearance; command-line options like `-Wall'
have generally similar effects; and the quality of generated code (in
terms of speed and size) is roughly similar (since that work is done by
the shared GBE).


File: g77.info,  Node: G77 and GCC,  Next: Invoking G77,  Prev: What is GNU Fortran?,  Up: Top

Compile Fortran, C, or Other Programs
*************************************

   A GNU Fortran installation includes a modified version of the `gcc'
command.

   In a non-Fortran installation, `gcc' recognizes C, C++, and
Objective-C source files.

   In a GNU Fortran installation, `gcc' also recognizes Fortran source
files and accepts Fortran-specific command-line options, plus some
command-line options that are designed to cater to Fortran users but
apply to other languages as well.

   *Note Compile C; C++; or Objective-C: (gcc)G++ and GCC, for
information on the way different languages are handled by the GNU CC
compiler (`gcc').

   Also provided as part of GNU Fortran is the `g77' command.  The
`g77' command is designed to make compiling and linking Fortran
programs somewhat easier than when using the `gcc' command for these
tasks.  It does this by analyzing the command line somewhat and
changing it appropriately before submitting it to the `gcc' command.

   Use the `-v' option with `g77' to see what is going on--the first
line of output is the invocation of the `gcc' command.


File: g77.info,  Node: Invoking G77,  Next: News,  Prev: G77 and GCC,  Up: Top

GNU Fortran Command Options
***************************

   The `g77' command supports all the options supported by the `gcc'
command.  *Note GNU CC Command Options: (gcc)Invoking GCC, for
information on the non-Fortran-specific aspects of the `gcc' command
(and, therefore, the `g77' command).

   All `gcc' and `g77' options are accepted both by `g77' and by `gcc'
(as well as any other drivers built at the same time, such as `g++'),
since adding `g77' to the `gcc' distribution enables acceptance of
`g77'-specific options by all of the relevant drivers.

   In some cases, options have positive and negative forms; the
negative form of `-ffoo' would be `-fno-foo'.  This manual documents
only one of these two forms, whichever one is not the default.

* Menu:

* Option Summary::      Brief list of all `g77' options,
                        without explanations.
* Overall Options::     Controlling the kind of output:
                        an executable, object files, assembler files,
                        or preprocessed source.
* Shorthand Options::   Options that are shorthand for other options.
* Fortran Dialect Options::  Controlling the variant of Fortran language
                             compiled.
* Warning Options::     How picky should the compiler be?
* Debugging Options::   Symbol tables, measurements, and debugging dumps.
* Optimize Options::    How much optimization?
* Preprocessor Options:: Controlling header files and macro definitions.
                         Also, getting dependency information for Make.
* Directory Options::   Where to find header files and libraries.
                        Where to find the compiler executable files.
* Code Gen Options::    Specifying conventions for function calls, data layout
                        and register usage.
* Environment Variables:: Env vars that affect GNU Fortran.


File: g77.info,  Node: Option Summary,  Next: Overall Options,  Up: Invoking G77

Option Summary
==============

   Here is a summary of all the options specific to GNU Fortran, grouped
by type.  Explanations are in the following sections.

_Overall Options_
     *Note Options Controlling the Kind of Output: Overall Options.
          -fversion  -fset-g77-defaults  -fno-silent

_Shorthand Options_
     *Note Shorthand Options::.
          -ff66  -fno-f66  -ff77  -fno-f77  -fno-ugly

_Fortran Language Options_
     *Note Options Controlling Fortran Dialect: Fortran Dialect Options.
          -ffree-form  -fno-fixed-form  -ff90
          -fvxt  -fdollar-ok  -fno-backslash
          -fno-ugly-args  -fno-ugly-assign  -fno-ugly-assumed
          -fugly-comma  -fugly-complex  -fugly-init  -fugly-logint
          -fonetrip  -ftypeless-boz
          -fintrin-case-initcap  -fintrin-case-upper
          -fintrin-case-lower  -fintrin-case-any
          -fmatch-case-initcap  -fmatch-case-upper
          -fmatch-case-lower  -fmatch-case-any
          -fsource-case-upper  -fsource-case-lower
          -fsource-case-preserve
          -fsymbol-case-initcap  -fsymbol-case-upper
          -fsymbol-case-lower  -fsymbol-case-any
          -fcase-strict-upper  -fcase-strict-lower
          -fcase-initcap  -fcase-upper  -fcase-lower  -fcase-preserve
          -ff2c-intrinsics-delete  -ff2c-intrinsics-hide
          -ff2c-intrinsics-disable  -ff2c-intrinsics-enable
          -fbadu77-intrinsics-delete  -fbadu77-intrinsics-hide
          -fbadu77-intrinsics-disable  -fbadu77-intrinsics-enable
          -ff90-intrinsics-delete  -ff90-intrinsics-hide
          -ff90-intrinsics-disable  -ff90-intrinsics-enable
          -fgnu-intrinsics-delete  -fgnu-intrinsics-hide
          -fgnu-intrinsics-disable  -fgnu-intrinsics-enable
          -fmil-intrinsics-delete  -fmil-intrinsics-hide
          -fmil-intrinsics-disable  -fmil-intrinsics-enable
          -funix-intrinsics-delete  -funix-intrinsics-hide
          -funix-intrinsics-disable  -funix-intrinsics-enable
          -fvxt-intrinsics-delete  -fvxt-intrinsics-hide
          -fvxt-intrinsics-disable  -fvxt-intrinsics-enable
          -ffixed-line-length-N  -ffixed-line-length-none

_Warning Options_
     *Note Options to Request or Suppress Warnings: Warning Options.
          -fsyntax-only  -pedantic  -pedantic-errors  -fpedantic
          -w  -Wno-globals  -Wimplicit  -Wunused  -Wuninitialized
          -Wall  -Wsurprising
          -Werror  -W

_Debugging Options_
     *Note Options for Debugging Your Program or GCC: Debugging Options.
          -g

_Optimization Options_
     *Note Options that Control Optimization: Optimize Options.
          -malign-double
          -ffloat-store  -fforce-mem  -fforce-addr  -fno-inline
          -ffast-math  -fstrength-reduce  -frerun-cse-after-loop
          -fexpensive-optimizations  -fdelayed-branch
          -fschedule-insns  -fschedule-insn2  -fcaller-saves
          -funroll-loops  -funroll-all-loops
          -fno-move-all-movables  -fno-reduce-all-givs
          -fno-rerun-loop-opt

_Directory Options_
     *Note Options for Directory Search: Directory Options.
          -IDIR  -I-

_Code Generation Options_
     *Note Options for Code Generation Conventions: Code Gen Options.
          -fno-automatic  -finit-local-zero  -fno-f2c
          -ff2c-library  -fno-underscoring  -fno-ident
          -fpcc-struct-return  -freg-struct-return
          -fshort-double  -fno-common  -fpack-struct
          -fzeros  -fno-second-underscore
          -fdebug-kludge  -femulate-complex
          -falias-check  -fargument-alias
          -fargument-noalias  -fno-argument-noalias-global
          -fno-globals  -fflatten-arrays
          -fbounds-check  -ffortran-bounds-check

* Menu:

* Overall Options::     Controlling the kind of output:
                        an executable, object files, assembler files,
                        or preprocessed source.
* Shorthand Options::   Options that are shorthand for other options.
* Fortran Dialect Options::  Controlling the variant of Fortran language
                             compiled.
* Warning Options::     How picky should the compiler be?
* Debugging Options::   Symbol tables, measurements, and debugging dumps.
* Optimize Options::    How much optimization?
* Preprocessor Options:: Controlling header files and macro definitions.
                         Also, getting dependency information for Make.
* Directory Options::   Where to find header files and libraries.
                        Where to find the compiler executable files.
* Code Gen Options::    Specifying conventions for function calls, data layout
                        and register usage.


File: g77.info,  Node: Overall Options,  Next: Shorthand Options,  Prev: Option Summary,  Up: Invoking G77

Options Controlling the Kind of Output
======================================

   Compilation can involve as many as four stages: preprocessing, code
generation (often what is really meant by the term "compilation"),
assembly, and linking, always in that order.  The first three stages
apply to an individual source file, and end by producing an object
file; linking combines all the object files (those newly compiled, and
those specified as input) into an executable file.

   For any given input file, the file name suffix determines what kind
of program is contained in the file--that is, the language in which the
program is written is generally indicated by the suffix.  Suffixes
specific to GNU Fortran are listed below.  *Note gcc: (Using and
Porting GNU CC)Overall Options, for information on suffixes recognized
by GNU CC.

`FILE.f'

`FILE.for'

`FILE.FOR'
     Fortran source code that should not be preprocessed.

     Such source code cannot contain any preprocessor directives, such
     as `#include', `#define', `#if', and so on.

     You can force `.f' files to be preprocessed by `cpp' by using `-x
     f77-cpp-input'.  *Note LEX::.

`FILE.F'

`FILE.fpp'

`FILE.FPP'
     Fortran source code that must be preprocessed (by the C
     preprocessor `cpp', which is part of GNU CC).

     Note that preprocessing is not extended to the contents of files
     included by the `INCLUDE' directive--the `#include' preprocessor
     directive must be used instead.

`FILE.r'
     Ratfor source code, which must be preprocessed by the `ratfor'
     command, which is available separately (as it is not yet part of
     the GNU Fortran distribution).  One version in Fortran, adapted
     for use with `g77', is at `ftp://members.aol.com/n8tm/rat7.uue'
     (of uncertain copyright status).  Another, public domain version
     in C is at `http://sepwww.stanford.edu/sep/prof/ratfor.shar.2'.

   UNIX users typically use the `FILE.f' and `FILE.F' nomenclature.
Users of other operating systems, especially those that cannot
distinguish upper-case letters from lower-case letters in their file
names, typically use the `FILE.for' and `FILE.fpp' nomenclature.

   Use of the preprocessor `cpp' allows use of C-like constructs such
as `#define' and `#include', but can lead to unexpected, even mistaken,
results due to Fortran's source file format.  It is recommended that
use of the C preprocessor be limited to `#include' and, in conjunction
with `#define', only `#if' and related directives, thus avoiding
in-line macro expansion entirely.  This recommendation applies
especially when using the traditional fixed source form.  With free
source form, fewer unexpected transformations are likely to happen, but
use of constructs such as Hollerith and character constants can
nevertheless present problems, especially when these are continued
across multiple source lines.  These problems result, primarily, from
differences between the way such constants are interpreted by the C
preprocessor and by a Fortran compiler.

   Another example of a problem that results from using the C
preprocessor is that a Fortran comment line that happens to contain any
characters "interesting" to the C preprocessor, such as a backslash at
the end of the line, is not recognized by the preprocessor as a comment
line, so instead of being passed through "raw", the line is edited
according to the rules for the preprocessor.  For example, the
backslash at the end of the line is removed, along with the subsequent
newline, resulting in the next line being effectively commented
out--unfortunate if that line is a non-comment line of important code!

   _Note:_ The `-traditional' and `-undef' flags are supplied to `cpp'
by default, to help avoid unpleasant surprises.  *Note Options
Controlling the Preprocessor: (gcc)Preprocessor Options.  This means
that ANSI C preprocessor features (such as the `#' operator) aren't
available, and only variables in the C reserved namespace (generally,
names with a leading underscore) are liable to substitution by C
predefines.  Thus, if you want to do system-specific tests, use, for
example, `#ifdef __linux__' rather than `#ifdef linux'.  Use the `-v'
option to see exactly how the preprocessor is invoked.

   Unfortunately, the `-traditional' flag will not avoid an error from
anything that `cpp' sees as an unterminated C comment, such as:
     C Some Fortran compilers accept /* as starting
     C an inline comment.
   *Note Trailing Comment::.

   The following options that affect overall processing are recognized
by the `g77' and `gcc' commands in a GNU Fortran installation:

`-fversion'
     Ensure that the `g77'-specific version of the compiler phase is
     reported, if run, and, starting in `egcs' version 1.1, that
     internal consistency checks in the `f771' program are run.

     This option is supplied automatically when `-v' or `--verbose' is
     specified as a command-line option for `g77' or `gcc' and when the
     resulting commands compile Fortran source files.

`-fset-g77-defaults'
     _Version info:_ This option was obsolete as of `egcs' version 1.1.
     The effect is instead achieved by the `lang_init_options' routine
     in `gcc/gcc/f/com.c'.

     Set up whatever `gcc' options are to apply to Fortran
     compilations, and avoid running internal consistency checks that
     might take some time.

     This option is supplied automatically when compiling Fortran code
     via the `g77' or `gcc' command.  The description of this option is
     provided so that users seeing it in the output of, say, `g77 -v'
     understand why it is there.

     Also, developers who run `f771' directly might want to specify it
     by hand to get the same defaults as they would running `f771' via
     `g77' or `gcc'.  However, such developers should, after linking a
     new `f771' executable, invoke it without this option once, e.g.
     via `./f771 -quiet < /dev/null', to ensure that they have not
     introduced any internal inconsistencies (such as in the table of
     intrinsics) before proceeding--`g77' will crash with a diagnostic
     if it detects an inconsistency.

`-fno-silent'
     Print (to `stderr') the names of the program units as they are
     compiled, in a form similar to that used by popular UNIX `f77'
     implementations and `f2c'.

   *Note Options Controlling the Kind of Output: (gcc)Overall Options,
for information on more options that control the overall operation of
the `gcc' command (and, by extension, the `g77' command).


File: g77.info,  Node: Shorthand Options,  Next: Fortran Dialect Options,  Prev: Overall Options,  Up: Invoking G77

Shorthand Options
=================

   The following options serve as "shorthand" for other options
accepted by the compiler:

`-fugly'
     _Note:_ This option is no longer supported.  The information,
     below, is provided to aid in the conversion of old scripts.

     Specify that certain "ugly" constructs are to be quietly accepted.
     Same as:

          -fugly-args -fugly-assign -fugly-assumed
          -fugly-comma -fugly-complex -fugly-init
          -fugly-logint

     These constructs are considered inappropriate to use in new or
     well-maintained portable Fortran code, but widely used in old code.
     *Note Distensions::, for more information.

`-fno-ugly'
     Specify that all "ugly" constructs are to be noisily rejected.
     Same as:

          -fno-ugly-args -fno-ugly-assign -fno-ugly-assumed
          -fno-ugly-comma -fno-ugly-complex -fno-ugly-init
          -fno-ugly-logint

     *Note Distensions::, for more information.

`-ff66'
     Specify that the program is written in idiomatic FORTRAN 66.  Same
     as `-fonetrip -fugly-assumed'.

     The `-fno-f66' option is the inverse of `-ff66'.  As such, it is
     the same as `-fno-onetrip -fno-ugly-assumed'.

     The meaning of this option is likely to be refined as future
     versions of `g77' provide more compatibility with other existing
     and obsolete Fortran implementations.

`-ff77'
     Specify that the program is written in idiomatic UNIX FORTRAN 77
     and/or the dialect accepted by the `f2c' product.  Same as
     `-fbackslash -fno-typeless-boz'.

     The meaning of this option is likely to be refined as future
     versions of `g77' provide more compatibility with other existing
     and obsolete Fortran implementations.

`-fno-f77'
     The `-fno-f77' option is _not_ the inverse of `-ff77'.  It
     specifies that the program is not written in idiomatic UNIX
     FORTRAN 77 or `f2c', but in a more widely portable dialect.
     `-fno-f77' is the same as `-fno-backslash'.

     The meaning of this option is likely to be refined as future
     versions of `g77' provide more compatibility with other existing
     and obsolete Fortran implementations.


File: g77.info,  Node: Fortran Dialect Options,  Next: Warning Options,  Prev: Shorthand Options,  Up: Invoking G77

Options Controlling Fortran Dialect
===================================

   The following options control the dialect of Fortran that the
compiler accepts:

`-ffree-form'

`-fno-fixed-form'
     Specify that the source file is written in free form (introduced
     in Fortran 90) instead of the more-traditional fixed form.

`-ff90'
     Allow certain Fortran-90 constructs.

     This option controls whether certain Fortran 90 constructs are
     recognized.  (Other Fortran 90 constructs might or might not be
     recognized depending on other options such as `-fvxt',
     `-ff90-intrinsics-enable', and the current level of support for
     Fortran 90.)

     *Note Fortran 90::, for more information.

`-fvxt'
     Specify the treatment of certain constructs that have different
     meanings depending on whether the code is written in GNU Fortran
     (based on FORTRAN 77 and akin to Fortran 90) or VXT Fortran (more
     like VAX FORTRAN).

     The default is `-fno-vxt'.  `-fvxt' specifies that the VXT Fortran
     interpretations for those constructs are to be chosen.

     *Note VXT Fortran::, for more information.

`-fdollar-ok'
     Allow `$' as a valid character in a symbol name.

`-fno-backslash'
     Specify that `\' is not to be specially interpreted in character
     and Hollerith constants a la C and many UNIX Fortran compilers.

     For example, with `-fbackslash' in effect, `A\nB' specifies three
     characters, with the second one being newline.  With
     `-fno-backslash', it specifies four characters, `A', `\', `n', and
     `B'.

     Note that `g77' implements a fairly general form of backslash
     processing that is incompatible with the narrower forms supported
     by some other compilers.  For example, `'A\003B'' is a
     three-character string in `g77', whereas other compilers that
     support backslash might not support the three-octal-digit form,
     and thus treat that string as longer than three characters.

     *Note Backslash in Constants::, for information on why
     `-fbackslash' is the default instead of `-fno-backslash'.

`-fno-ugly-args'
     Disallow passing Hollerith and typeless constants as actual
     arguments (for example, `CALL FOO(4HABCD)').

     *Note Ugly Implicit Argument Conversion::, for more information.

`-fugly-assign'
     Use the same storage for a given variable regardless of whether it
     is used to hold an assigned-statement label (as in `ASSIGN 10 TO
     I') or used to hold numeric data (as in `I = 3').

     *Note Ugly Assigned Labels::, for more information.

`-fugly-assumed'
     Assume any dummy array with a final dimension specified as `1' is
     really an assumed-size array, as if `*' had been specified for the
     final dimension instead of `1'.

     For example, `DIMENSION X(1)' is treated as if it had read
     `DIMENSION X(*)'.

     *Note Ugly Assumed-Size Arrays::, for more information.

`-fugly-comma'
     In an external-procedure invocation, treat a trailing comma in the
     argument list as specification of a trailing null argument, and
     treat an empty argument list as specification of a single null
     argument.

     For example, `CALL FOO(,)' is treated as `CALL FOO(%VAL(0),
     %VAL(0))'.  That is, _two_ null arguments are specified by the
     procedure call when `-fugly-comma' is in force.  And `F = FUNC()'
     is treated as `F = FUNC(%VAL(0))'.

     The default behavior, `-fno-ugly-comma', is to ignore a single
     trailing comma in an argument list.  So, by default, `CALL
     FOO(X,)' is treated exactly the same as `CALL FOO(X)'.

     *Note Ugly Null Arguments::, for more information.

`-fugly-complex'
     Do not complain about `REAL(EXPR)' or `AIMAG(EXPR)' when EXPR is a
     `COMPLEX' type other than `COMPLEX(KIND=1)'--usually this is used
     to permit `COMPLEX(KIND=2)' (`DOUBLE COMPLEX') operands.

     The `-ff90' option controls the interpretation of this construct.

     *Note Ugly Complex Part Extraction::, for more information.

`-fno-ugly-init'
     Disallow use of Hollerith and typeless constants as initial values
     (in `PARAMETER' and `DATA' statements), and use of character
     constants to initialize numeric types and vice versa.

     For example, `DATA I/'F'/, CHRVAR/65/, J/4HABCD/' is disallowed by
     `-fno-ugly-init'.

     *Note Ugly Conversion of Initializers::, for more information.

`-fugly-logint'
     Treat `INTEGER' and `LOGICAL' variables and expressions as
     potential stand-ins for each other.

     For example, automatic conversion between `INTEGER' and `LOGICAL'
     is enabled, for many contexts, via this option.

     *Note Ugly Integer Conversions::, for more information.

`-fonetrip'
     Executable iterative `DO' loops are to be executed at least once
     each time they are reached.

     ANSI FORTRAN 77 and more recent versions of the Fortran standard
     specify that the body of an iterative `DO' loop is not executed if
     the number of iterations calculated from the parameters of the
     loop is less than 1.  (For example, `DO 10 I = 1, 0'.)  Such a
     loop is called a "zero-trip loop".

     Prior to ANSI FORTRAN 77, many compilers implemented `DO' loops
     such that the body of a loop would be executed at least once, even
     if the iteration count was zero.  Fortran code written assuming
     this behavior is said to require "one-trip loops".  For example,
     some code written to the FORTRAN 66 standard expects this behavior
     from its `DO' loops, although that standard did not specify this
     behavior.

     The `-fonetrip' option specifies that the source file(s) being
     compiled require one-trip loops.

     This option affects only those loops specified by the (iterative)
     `DO' statement and by implied-`DO' lists in I/O statements.  Loops
     specified by implied-`DO' lists in `DATA' and specification
     (non-executable) statements are not affected.

`-ftypeless-boz'
     Specifies that prefix-radix non-decimal constants, such as
     `Z'ABCD'', are typeless instead of `INTEGER(KIND=1)'.

     You can test for yourself whether a particular compiler treats the
     prefix form as `INTEGER(KIND=1)' or typeless by running the
     following program:

          EQUIVALENCE (I, R)
          R = Z'ABCD1234'
          J = Z'ABCD1234'
          IF (J .EQ. I) PRINT *, 'Prefix form is TYPELESS'
          IF (J .NE. I) PRINT *, 'Prefix form is INTEGER'
          END

     Reports indicate that many compilers process this form as
     `INTEGER(KIND=1)', though a few as typeless, and at least one
     based on a command-line option specifying some kind of
     compatibility.

`-fintrin-case-initcap'

`-fintrin-case-upper'

`-fintrin-case-lower'

`-fintrin-case-any'
     Specify expected case for intrinsic names.  `-fintrin-case-lower'
     is the default.

`-fmatch-case-initcap'

`-fmatch-case-upper'

`-fmatch-case-lower'

`-fmatch-case-any'
     Specify expected case for keywords.  `-fmatch-case-lower' is the
     default.

`-fsource-case-upper'

`-fsource-case-lower'

`-fsource-case-preserve'
     Specify whether source text other than character and Hollerith
     constants is to be translated to uppercase, to lowercase, or
     preserved as is.  `-fsource-case-lower' is the default.

`-fsymbol-case-initcap'

`-fsymbol-case-upper'

`-fsymbol-case-lower'

`-fsymbol-case-any'
     Specify valid cases for user-defined symbol names.
     `-fsymbol-case-any' is the default.

`-fcase-strict-upper'
     Same as `-fintrin-case-upper -fmatch-case-upper
     -fsource-case-preserve -fsymbol-case-upper'.  (Requires all
     pertinent source to be in uppercase.)

`-fcase-strict-lower'
     Same as `-fintrin-case-lower -fmatch-case-lower
     -fsource-case-preserve -fsymbol-case-lower'.  (Requires all
     pertinent source to be in lowercase.)

`-fcase-initcap'
     Same as `-fintrin-case-initcap -fmatch-case-initcap
     -fsource-case-preserve -fsymbol-case-initcap'.  (Requires all
     pertinent source to be in initial capitals, as in `Print
     *,SqRt(Value)'.)

`-fcase-upper'
     Same as `-fintrin-case-any -fmatch-case-any -fsource-case-upper
     -fsymbol-case-any'.  (Maps all pertinent source to uppercase.)

`-fcase-lower'
     Same as `-fintrin-case-any -fmatch-case-any -fsource-case-lower
     -fsymbol-case-any'.  (Maps all pertinent source to lowercase.)

`-fcase-preserve'
     Same as `-fintrin-case-any -fmatch-case-any -fsource-case-preserve
     -fsymbol-case-any'.  (Preserves all case in user-defined symbols,
     while allowing any-case matching of intrinsics and keywords.  For
     example, `call Foo(i,I)' would pass two _different_ variables
     named `i' and `I' to a procedure named `Foo'.)

`-fbadu77-intrinsics-delete'

`-fbadu77-intrinsics-hide'

`-fbadu77-intrinsics-disable'

`-fbadu77-intrinsics-enable'
     Specify status of UNIX intrinsics having inappropriate forms.
     `-fbadu77-intrinsics-enable' is the default.  *Note Intrinsic
     Groups::.

`-ff2c-intrinsics-delete'

`-ff2c-intrinsics-hide'

`-ff2c-intrinsics-disable'

`-ff2c-intrinsics-enable'
     Specify status of f2c-specific intrinsics.
     `-ff2c-intrinsics-enable' is the default.  *Note Intrinsic
     Groups::.

`-ff90-intrinsics-delete'

`-ff90-intrinsics-hide'

`-ff90-intrinsics-disable'

`-ff90-intrinsics-enable'
     Specify status of F90-specific intrinsics.
     `-ff90-intrinsics-enable' is the default.  *Note Intrinsic
     Groups::.

`-fgnu-intrinsics-delete'

`-fgnu-intrinsics-hide'

`-fgnu-intrinsics-disable'

`-fgnu-intrinsics-enable'
     Specify status of Digital's COMPLEX-related intrinsics.
     `-fgnu-intrinsics-enable' is the default.  *Note Intrinsic
     Groups::.

`-fmil-intrinsics-delete'

`-fmil-intrinsics-hide'

`-fmil-intrinsics-disable'

`-fmil-intrinsics-enable'
     Specify status of MIL-STD-1753-specific intrinsics.
     `-fmil-intrinsics-enable' is the default.  *Note Intrinsic
     Groups::.

`-funix-intrinsics-delete'

`-funix-intrinsics-hide'

`-funix-intrinsics-disable'

`-funix-intrinsics-enable'
     Specify status of UNIX intrinsics.  `-funix-intrinsics-enable' is
     the default.  *Note Intrinsic Groups::.

`-fvxt-intrinsics-delete'

`-fvxt-intrinsics-hide'

`-fvxt-intrinsics-disable'

`-fvxt-intrinsics-enable'
     Specify status of VXT intrinsics.  `-fvxt-intrinsics-enable' is
     the default.  *Note Intrinsic Groups::.

`-ffixed-line-length-N'
     Set column after which characters are ignored in typical fixed-form
     lines in the source file, and through which spaces are assumed (as
     if padded to that length) after the ends of short fixed-form lines.

     Popular values for N include 72 (the standard and the default), 80
     (card image), and 132 (corresponds to "extended-source" options in
     some popular compilers).  N may be `none', meaning that the entire
     line is meaningful and that continued character constants never
     have implicit spaces appended to them to fill out the line.
     `-ffixed-line-length-0' means the same thing as
     `-ffixed-line-length-none'.

     *Note Source Form::, for more information.


File: g77.info,  Node: Warning Options,  Next: Debugging Options,  Prev: Fortran Dialect Options,  Up: Invoking G77

Options to Request or Suppress Warnings
=======================================

   Warnings are diagnostic messages that report constructions which are
not inherently erroneous but which are risky or suggest there might
have been an error.

   You can request many specific warnings with options beginning `-W',
for example `-Wimplicit' to request warnings on implicit declarations.
Each of these specific warning options also has a negative form
beginning `-Wno-' to turn off warnings; for example, `-Wno-implicit'.
This manual lists only one of the two forms, whichever is not the
default.

   These options control the amount and kinds of warnings produced by
GNU Fortran:

`-fsyntax-only'
     Check the code for syntax errors, but don't do anything beyond
     that.

`-pedantic'
     Issue warnings for uses of extensions to ANSI FORTRAN 77.
     `-pedantic' also applies to C-language constructs where they occur
     in GNU Fortran source files, such as use of `\e' in a character
     constant within a directive like `#include'.

     Valid ANSI FORTRAN 77 programs should compile properly with or
     without this option.  However, without this option, certain GNU
     extensions and traditional Fortran features are supported as well.
     With this option, many of them are rejected.

     Some users try to use `-pedantic' to check programs for strict ANSI
     conformance.  They soon find that it does not do quite what they
     want--it finds some non-ANSI practices, but not all.  However,
     improvements to `g77' in this area are welcome.

`-pedantic-errors'
     Like `-pedantic', except that errors are produced rather than
     warnings.

`-fpedantic'
     Like `-pedantic', but applies only to Fortran constructs.

`-w'
     Inhibit all warning messages.

`-Wno-globals'
     Inhibit warnings about use of a name as both a global name (a
     subroutine, function, or block data program unit, or a common
     block) and implicitly as the name of an intrinsic in a source file.

     Also inhibit warnings about inconsistent invocations and/or
     definitions of global procedures (function and subroutines).  Such
     inconsistencies include different numbers of arguments and
     different types of arguments.

`-Wimplicit'
     Warn whenever a variable, array, or function is implicitly
     declared.  Has an effect similar to using the `IMPLICIT NONE'
     statement in every program unit.  (Some Fortran compilers provide
     this feature by an option named `-u' or `/WARNINGS=DECLARATIONS'.)

`-Wunused'
     Warn whenever a variable is unused aside from its declaration.

`-Wuninitialized'
     Warn whenever an automatic variable is used without first being
     initialized.

     These warnings are possible only in optimizing compilation,
     because they require data-flow information that is computed only
     when optimizing.  If you don't specify `-O', you simply won't get
     these warnings.

     These warnings occur only for variables that are candidates for
     register allocation.  Therefore, they do not occur for a variable
     whose address is taken, or whose size is other than 1, 2, 4 or 8
     bytes.  Also, they do not occur for arrays, even when they are in
     registers.

     Note that there might be no warning about a variable that is used
     only to compute a value that itself is never used, because such
     computations may be deleted by data-flow analysis before the
     warnings are printed.

     These warnings are made optional because GNU Fortran is not smart
     enough to see all the reasons why the code might be correct
     despite appearing to have an error.  Here is one example of how
     this can happen:

          SUBROUTINE DISPAT(J)
          IF (J.EQ.1) I=1
          IF (J.EQ.2) I=4
          IF (J.EQ.3) I=5
          CALL FOO(I)
          END

     If the value of `J' is always 1, 2 or 3, then `I' is always
     initialized, but GNU Fortran doesn't know this.  Here is another
     common case:

          SUBROUTINE MAYBE(FLAG)
          LOGICAL FLAG
          IF (FLAG) VALUE = 9.4
          ...
          IF (FLAG) PRINT *, VALUE
          END

     This has no bug because `VALUE' is used only if it is set.

`-Wall'
     The `-Wunused' and `-Wuninitialized' options combined.  These are
     all the options which pertain to usage that we recommend avoiding
     and that we believe is easy to avoid.  (As more warnings are added
     to `g77', some might be added to the list enabled by `-Wall'.)

   The remaining `-W...' options are not implied by `-Wall' because
they warn about constructions that we consider reasonable to use, on
occasion, in clean programs.

`-Wsurprising'
     Warn about "suspicious" constructs that are interpreted by the
     compiler in a way that might well be surprising to someone reading
     the code.  These differences can result in subtle,
     compiler-dependent (even machine-dependent) behavioral differences.
     The constructs warned about include:

        * Expressions having two arithmetic operators in a row, such as
          `X*-Y'.  Such a construct is nonstandard, and can produce
          unexpected results in more complicated situations such as
          `X**-Y*Z'.  `g77', along with many other compilers, interprets
          this example differently than many programmers, and a few
          other compilers.  Specifically, `g77' interprets `X**-Y*Z' as
          `(X**(-Y))*Z', while others might think it should be
          interpreted as `X**(-(Y*Z))'.

          A revealing example is the constant expression `2**-2*1.',
          which `g77' evaluates to .25, while others might evaluate it
          to 0., the difference resulting from the way precedence
          affects type promotion.

          (The `-fpedantic' option also warns about expressions having
          two arithmetic operators in a row.)

        * Expressions with a unary minus followed by an operand and then
          a binary operator other than plus or minus.  For example,
          `-2**2' produces a warning, because the precedence is
          `-(2**2)', yielding -4, not `(-2)**2', which yields 4, and
          which might represent what a programmer expects.

          An example of an expression producing different results in a
          surprising way is `-I*S', where I holds the value
          `-2147483648' and S holds `0.5'.  On many systems, negating I
          results in the same value, not a positive number, because it
          is already the lower bound of what an `INTEGER(KIND=1)'
          variable can hold.  So, the expression evaluates to a
          positive number, while the "expected" interpretation,
          `(-I)*S', would evaluate to a negative number.

          Even cases such as `-I*J' produce warnings, even though, in
          most configurations and situations, there is no computational
          difference between the results of the two
          interpretations--the purpose of this warning is to warn about
          differing interpretations and encourage a better style of
          coding, not to identify only those places where bugs might
          exist in the user's code.

        * `DO' loops with `DO' variables that are not of integral
          type--that is, using `REAL' variables as loop control
          variables.  Although such loops can be written to work in the
          "obvious" way, the way `g77' is required by the Fortran
          standard to interpret such code is likely to be quite
          different from the way many programmers expect.  (This is
          true of all `DO' loops, but the differences are pronounced
          for non-integral loop control variables.)

          *Note Loops::, for more information.

`-Werror'
     Make all warnings into errors.

`-W'
     Turns on "extra warnings" and, if optimization is specified via
     `-O', the `-Wuninitialized' option.  (This might change in future
     versions of `g77'.)

     "Extra warnings" are issued for:

        * Unused parameters to a procedure (when `-Wunused' also is
          specified).

        * Overflows involving floating-point constants (not available
          for certain configurations).

   *Note Options to Request or Suppress Warnings: (gcc)Warning Options,
for information on more options offered by the GBE shared by `g77',
`gcc', and other GNU compilers.

   Some of these have no effect when compiling programs written in
Fortran:

`-Wcomment'

`-Wformat'

`-Wparentheses'

`-Wswitch'

`-Wtraditional'

`-Wshadow'

`-Wid-clash-LEN'

`-Wlarger-than-LEN'

`-Wconversion'

`-Waggregate-return'

`-Wredundant-decls'
     These options all could have some relevant meaning for GNU Fortran
     programs, but are not yet supported.

