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 have a libtool version of the form current:revision:age. (Library Versioning)
Libraries have a package version of the form major.minor.micro. (Library Versioning)
Applications have a package version of the form major.minor. (Application Versioning)
Version numbers should be updated for each release (using pre- and post-release increments). (Release Process)
Package versions should be incremented for feature changes or additions. (Library Versioning)
Libtool versions should be updated for API changes or additions. (Library Versioning)
Libraries have two version numbers: a libtool version which tracks ABI backwards compatibility, 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)
The package version number for a library 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 have the form ‘major.minor.micro’, and are updated by the following rules:
If breaking API compatibility, increment major and set minor and micro to 0.
Otherwise, if adding a large feature or other big change, or adding any API, increment minor and set micro to 0.
Otherwise (for example, if making a release containing only bug fixes or translation updates), increment micro.
Note that the minor version number should be updated if any API is added.
Application versioning is simpler than library versioning: applications only have a package number, and it follows the scheme ‘major.minor’.
The application package number is updated similarly to the library package number, except the micro version is omitted:
If making a large change to the application which affects everything (such as a UI redesign), increment major and set minor to 0.
Otherwise, increment minor.
The standard process for making a release of a module increments the libtool version (if the module is a library) immediately before release, does the release, then increments the package version number immediately afterwards. This is called pre-release increment for libtool versioning and post-release increment for package versioning.
The use of pre-release increment for libtool versions 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
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, 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.
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