Tag Archives: autoconf-archive

gnome-common deprecation, round 2

tl;dr: gnome-common is deprecated, but will be hanging around for a while. If you care about modernising your build system, migrate to autoconf-archive macros.

This GNOME release cycle (3.18), we plan to do the last ever release of gnome-common. A lot of its macros for deprecated technologies (scrollkeeper?!) have been removed, and the remainder of its macros have found better replacements in autoconf-archive, where they can be used by everyone, not just GNOME.

We plan to make one last release, and people are welcome to depend on it for as long as they like. However, if you want new hotness, port to the autoconf-archive versions of the macros; but please do it in your own time. There will be no flag day port away from gnome-common.

Note that, for example, porting to AX_COMPILER_FLAGS is valuable, but will probably require fixing a number of new compiler warnings in your code due to increased warning flags. We hope this will make your code better in the long run.

There’s a migration guide here: https://wiki.gnome.org/Projects/GnomeCommon/Migration.

We’ve tried to make the transition as easy and smooth as possible, but there will inevitably be hiccups. Please let me know about anything which breaks or doesn’t make sense, or discuss it on the desktop development list thread. First person to complain about -Wswitch-enum gets a prize.

For developers

When building from a tarball of a module which uses the new macros, you will no longer need gnome-common installed. (Although you may not have needed it before.)

When building from git, you will need m4-common or autoconf-archive installed.

JHBuild bootstrap installs m4-common automatically, as does gnome-continuous; so you don’t need to worry about that.

For packagers

In the 3.14.0 release, gnome-common installed some early versions of the autoconf-archive macros which conflicted with what autoconf-archive itself installs. It now has a --[with|without]-autoconf-archive configure option to control this. We suggest that all packagers pass --with-autoconf-archive if (and only if) autoconf-archive is packaged on the distribution. See bug #747920.

m4-common must not be packaged. See its README. m4-common is essentially a caching subset of autoconf-archive.

For continuous integrators

Modules which use the new AX_COMPILER_FLAGS macro gain a new standard --disable-Werror configure flag, which should be used in CI systems (and any other system where spurious compiler warnings should not cause total failure of a build) to disable -Werror. The idea here is that -Werror is enabled by default when building from git, and disabled by default when building from release tarballs and in buildbots.

For further discussion

See the thread on the desktop development mailing list.

Automatically Valgrinding code with AX_VALGRIND_CHECK

tl;dr: For `make check` with Valgrind support, add AX_VALGRIND_CHECK to configure.ac and @VALGRIND_CHECK_RULES@ to tests/Makefile.am. Use memcheck, helgrind, drd and sgcheck.

Once you’ve written a unit test suite with near-100% coverage, you can validate software with a lot more confidence than before, since any effort you put into validation is working across the whole code base.1 It’s quite common to check for memory leaks with Valgrind’s memcheck tool — but Valgrind has several additional tools which are useful in production: helgrind, drd and sgcheck.2 All of these can be run over unit tests.

How can you run a test suite under these tools? The normal method is some kind of hard-to-remember rune involving libtool, and either something about TESTS_ENVIRONMENT or some kind of LOG_COMPILER (but why would I want to compile my test logs?). For that reason, I’ve written an autoconf macro which abstracts it all a bit: AX_VALGRIND_CHECK. It adds a check-valgrind target to your makefile which handles running the `make check` tests under all four Valgrind tools of interest. Various ancillary variables (such as VALGRIND_SUPPRESSIONS_FILES or VALGRIND_FLAGS) allow the Valgrind options to be changed. `make check-valgrind` will return an error exit code if any problems are found, with the idea that the target can be used for automated testing and continuous integration.

To use it, either add a dependency on autoconf-archive to your project, or copy the ax_valgrind_check.m4 macro in-tree (and add it to EXTRA_DIST), then follow the instructions at the top of the file for adding it to configure.ac and tests/Makefile.am.

With this macro, I’ve tried to bring together existing makefile snippets which exist in various projects to produce one macro which can be reused everywhere. Of course, I’ve probably missed something – some feature or specific use case which someone has – so if anyone has any suggestions for improvement, please let me know or submit a patch to the autoconf-archive! For example, at the moment the macro requires automake’s parallel test harness, and does not support older versions of automake.

Thanks to my employer, Collabora, for enabling me to work on (hopefully useful) stuff like this!


  1. Normal caveats about the combinatorial complexity of dynamic testing apply. 

  2. Although currently the threading tools may not work with GLib threads, due to its use of futexes rather than pthreads

A checklist for writing pkg-config files

tl;dr: Use AX_PKG_CHECK_MODULES to split public/private dependencies; use AC_CONFIG_FILES to magically include the API version in the .pc file name.

A few tips for creating a pkg-config file which you will never need to think about maintaining again — because one of the most common problems with pkg-config files is that their dependency lists are years out of date compared to the dependencies checked for in configure.ac. See lower down for some example automake snippets.

  • Include the project’s major API version1 in the pkg-config file name. e.g. libfoo-1.pc rather than libfoo.pc. This will allow parallel installation of two API-incompatible versions of the library if it becomes necessary in future.
  • Split private and public dependencies between Requires and Requires.private. This eliminates over-linking when dynamically linking against the project, since in that case the private dependencies are not needed. This is easily done using the AX_PKG_CHECK_MODULES macro (and perhaps using an upstream macro in future — see pkg-config bug #87154). A dependency is public when its symbols are exposed in public headers installed by your project; it is private otherwise.
  • Include useful ancillary variables, such as the paths to any utilities, directories or daemons which ship with the project. For example, glib-2.0.pc has variables giving the paths for its utilities: glib-genmarshal, gobject-query and glib-mkenums. libosinfo-1.0.pc has variables for its database directories. Ensure the variables use a variable form of ${prefix}, allowing it to be overridden when invoking pkg-config using pkg-config --define-variable=prefix=/some/other/prefix. This allows use of libraries installed in one (read only) prefix from binaries in another, while installing ancillary files (e.g. D-Bus service files) to the second prefix.
  • Substitute in the Name and Version using @PACKAGE_NAME@ and @PACKAGE_VERSION@ so they don’t fall out of sync.
  • Place the .pc.in template in the source code subdirectory for the library it’s for — so if your project produces multiple libraries (or might do in future), the .pc.in files don’t get mixed up at the top level.

Given all those suggestions, here’s a template libmy-project/my-project.pc.in file (updated to incorporate suggestions by Dan Nicholson):

prefix=@prefix@
exec_prefix=@exec_prefix@
libdir=@libdir@
includedir=@includedir@

my_project_utility=my-project-utility-binary-name
my_project_db_dir=@sysconfdir@/my-project/db

Name: @PACKAGE_NAME@
Description: Some brief but informative description
Version: @PACKAGE_VERSION@
Libs: -L${libdir} -lmy-project-@API_VERSION@
Cflags: -I${includedir}/my-project-@API_VERSION@
Requires: @AX_PACKAGE_REQUIRES@
Requires.private: @AX_PACKAGE_REQUIRES_PRIVATE@

And here’s a a few snippets from a template configure.ac:

# Release version
m4_define([package_version_major],[1])
m4_define([package_version_minor],[2])
m4_define([package_version_micro],[3])

# API version
m4_define([api_version],[1])

AC_INIT([my-project],
        [package_version_major.package_version_minor.package_version_micro],
        …)

# Dependencies
PKG_PROG_PKG_CONFIG
PKG_INSTALLDIR

glib_reqs=2.40
gio_reqs=2.42
gthread_reqs=2.40
nice_reqs=0.1.6

# The first list on each line is public; the second is private.
# The AX_PKG_CHECK_MODULES macro substitutes AX_PACKAGE_REQUIRES and
# AX_PACKAGE_REQUIRES_PRIVATE.
AX_PKG_CHECK_MODULES([GLIB],
                     [glib-2.0 >= $glib_reqs gio-2.0 >= $gio_reqs],
                     [gthread-2.0 >= $gthread_reqs])
AX_PKG_CHECK_MODULES([NICE],
                     [nice >= $nice_reqs],
                     [])

AC_SUBST([PACKAGE_VERSION_MAJOR],package_version_major)
AC_SUBST([PACKAGE_VERSION_MINOR],package_version_minor)
AC_SUBST([PACKAGE_VERSION_MICRO],package_version_micro)
AC_SUBST([API_VERSION],api_version)

# Output files
# Rename the template .pc file to include the API version on configure
AC_CONFIG_FILES([
libmy-project/my-project-$API_VERSION.pc:libmy-project/my-project.pc.in
…
],[],
[API_VERSION='$API_VERSION'])
AC_OUTPUT

And finally, the top-level Makefile.am:

# Install the pkg-config file; the directory is set using
# PKG_INSTALLDIR in configure.ac.
pkgconfig_DATA = libmy-project/my-project-$(API_VERSION).pc

Once that’s all built, you’ll end up with an installed my-project-1.pc file containing the following (assuming a prefix of /usr; note that by default autoconf substitutes in references to variables rather than the values themselves, so pkg-config can continue to be used with --define-variable to override the prefix):

prefix=/usr
exec_prefix=${prefix}
libdir=${exec_prefix}/lib
includedir=${prefix}/include

my_project_utility=my-project-utility-binary-name
my_project_db_dir=${prefix}/etc/my-project/db

Name: my-project
Description: Some brief but informative description
Version: 1.2.3
Libs: -L${libdir} -lmy-project-1
Cflags: -I${includedir}/my-project-1
Requires: glib-2.0 >= 2.40 gio-2.0 >= 2.42 nice >= 0.1.6
Requires.private: gthread-2.0 >= 2.40

All code samples in this post are released into the public domain.


  1. Assuming this is the number which will change if backwards-incompatible API/ABI changes are made. 

Long live gnome-common? Macro deprecation

We’ve worked out the details, and have new recommendations for porting to autoconf-archive, including justifications and a migration guide. The information below is outdated.

gnome-common is shrinking, as we’ve decided to push as much of it as possible upstream. We have too many layers in our build systems, and adding an arbitrary dependency on gnome-common to pull in some macros once at configure time is not helpful — there are many cases where someone new has tried to build a module and failed with some weird autotools error about an undefined macro, purely because they didn’t have gnome-common installed.

So, for starters:

What does this mean for you, a module maintainer? Nothing, if you don’t want it to. gnome-common now contains copies of the autoconf-archive macros, and has compatibility wrappers for them.

In the long term, you should consider porting your build system to use the new, upstreamed macros. That means, for each macro:

  1. Downloading the macro to the m4/ directory in your project and adding it to git.
  2. Adding the macro to EXTRA_DIST in Makefile.am.
  3. Ensuring you have ACLOCAL_AMFLAGS = -I m4 ${ACLOCAL_FLAGS} in your top-level Makefile.am.
  4. Updating the macro invocation in configure.ac; just copy out the shim from gnome-common.m4 and tidy everything up.

Here’s an example change for GNOME_CODE_COVERAGE ? AX_CODE_COVERAGE in libgdata.

It seems from the comments that there’s more discussion to be had about the best way to implement this. So hold off on these changes for the moment!

This is the beginning of a (probably) long road to deprecating a lot of gnome-common. Macros like GNOME_COMPILE_WARNINGS and GNOME_COMMON_INIT are next in the firing line — they do nothing GNOME-specific, and should be part of a wider set of reusable free software build macros, like the autoconf-archive. gnome-common’s support for legacy documentation systems (DocBook, anyone?) is also getting deprecated next cycle.

Comments? Get in touch with me or David King (amigadave). This work is the (long overdue) result of a bit of discussion we had at the Berlin DX hackfest in May.