Philip Withnall
philip.withnall@collabora.co.uk 2015

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Versioning and releasing libraries and applications

# Versioning

#

        Sumar

          Module versioning differs for libraries and applications: libraries need a
          libtool version specified in addition to their package version.
          Applications just have a package version.

            Libraries and applications have a package version of the form
            major.minor.micro. ()

            Libraries additionally have a libtool version of the form
            current:revision:age. ()

            Version numbers should be updated for each release (using release and
            post-release increments). ()

            Package versions should be incremented for feature changes or additions.
            ()

            Libtool versions should be updated for API changes or additions.
            ()

            Even/odd minor package versions can be used respectively for
            stable/unstable releases. ()

# Package Versioning

Both libraries and applications have a package version of the form major.minor.micro.

The package version number is that passed to `AC_INIT()`, and the one which is typically known as the project’s version number. For example, the Debian package for a library will use the library’s package version (though may also include the major version number in the package name to allow for parallel installability). Package versions are updated by the following rules:

If breaking API compatibility in a library, or making a large change to an application which affects everything (such as a UI redesign), increment major and set minor and micro to 0.

Otherwise, if changing or adding a feature, or adding any API, increment minor and set micro to 0.

Otherwise (if making a release containing only bug fixes and translation updates), increment micro.

Note that the minor version number should be updated if any API is added.

# Libtool Versioning

Libraries have two version numbers: a libtool version which tracks ABI backwards compatibility (see ), and a package version which tracks feature changes. These are normally incremented in synchronization, but should be kept separate because ABI backwards compatibility is not necessarily related to feature changes or bug fixes. Furthermore, the two version numbers have different semantics, and cannot be automatically generated from each other.

A good overview of libtool versioning, and the differences from package versioning, is given in the Autotools Mythbuster; another is in the libtool manual.

To update the libtool version, follow the algorithm given in the comments below. This is a typical configure.ac snippet for setting up libtool versioning:

# Before making a release, the LT_VERSION string should be modified. The # string is of the form c:r:a. Follow these instructions sequentially: # 1. If the library source code has changed at all since the last update, then # increment revision (‘c:r:a’ becomes ‘c:r+1:a’). # 2. If any interfaces have been added, removed, or changed since the last # update, increment current, and set revision to 0. # 3. If any interfaces have been added since the last public release, then # increment age. # 4. If any interfaces have been removed or changed since the last public # release, then set age to 0. AC_SUBST([LT_VERSION],[0:0:0])

The following snippet can be used in a Makefile.am to pass that version info to libtool:

my_library_la_LDFLAGS = -version-info $(LT_VERSION)

# Stable and Unstable Package Versions

Most GNOME modules follow a convention for stable and unstable releases. The minor version is even for stable releases and is odd for unstable releases. For example, the 3.20.* versions are stable, but the 3.19.* versions are unstable. The 3.19.* versions can be seen as alpha and beta releases of the 3.20 version.

A new micro stable version (e.g. 3.20.0 → 3.20.1) doesn’t add new features, only translation updates and bug fixes. On the other hand, unstable micro releases (e.g. 3.19.1 → 3.19.2) can add API, or change or remove API which was added in a previous micro release in that minor series.

The libtool version should be updated only for stable package versions.

# Release Process

The standard process for making a release of a module increments the libtool version (if the module is a library) at the time of release, then increments the package version number immediately afterwards (this is called a post-release increment).

Updating the libtool versions at the time of release means that they are only incremented once for all ABI changes in a release. The use of post-release increment for package versions means the package version number is not outdated (still equal to the previous release) during the development cycle.

The release process (based on the GNOME release process):

Make sure code is up to date: git pull

Make sure you have no local changes: git status

If the release is for a stable package version, increment the libtool version number in configure.ac (if it exists)

Add an entry to the NEWS file

Run ./autogen.sh && make && make install && make distcheck and ensure it succeeds

Fix any issues which come up, commit those changes, and restart at step 3

If make distcheck finishes with “[archive] is ready for distribution”, run git commit -a -m "Release version x.y.z" (where ‘x.y.z’ is the package version number)

Run git push

If that fails due to other commits having been pushed in the meantime, run git pull to merge your commit on the branch followed by a second git push. This is an exception to the GNOME guideline to have a linear Git history (). If you prefer to have a linear history, you need to restart at step 1.

Tag the release: git tag -s x.y.z (where ‘x.y.z’ is the package version number)

Run git push origin x.y.z (where ‘x.y.z’ is the package version number)

The release is now complete, and the post-release version increment can be done:

Increment the package version number in configure.ac

Run git commit -a -m "Post-release version increment"

Run git push

The package archive generated by make distcheck can now be uploaded to download.gnome.org or distributed in other ways.