14.4 Checking the Distribution

Automake also generates a distcheck rule that can be of help to ensure that a given distribution will actually work. Simplifying a bit, we can say this rule first makes a distribution, and then, operating from it, takes the following steps:

• tries to do a VPATH build (see Parallel Build Trees (a.k.a. VPATH Builds)), with the srcdir and all its content made read-only;
• runs the test suite (with make check) on this fresh build;
• installs the package in a temporary directory (with make install), and tries runs the test suite on the resulting installation (with make installcheck);
• checks that the package can be correctly uninstalled (by make uninstall) and cleaned (by make distclean);
• finally, makes another tarball to ensure the distribution is self-contained.

All of these actions are performed in a temporary directory. Please note that the exact location and the exact structure of such a directory (where the read-only sources are placed, how the temporary build and install directories are named and how deeply they are nested, etc.) is to be considered an implementation detail, which can change at any time; so do not reply on it.

DISTCHECK_CONFIGURE_FLAGS

Building the package involves running ‘./configure’. If you need to supply additional flags to configure, define them in the AM_DISTCHECK_CONFIGURE_FLAGS variable in your top-level Makefile.am. The user can still extend or override the flags provided there by defining the DISTCHECK_CONFIGURE_FLAGS variable, on the command line when invoking make. It’s worth noting that make distcheck needs complete control over the configure options --srcdir and --prefix, so those options cannot be overridden by AM_DISTCHECK_CONFIGURE_FLAGS nor by DISTCHECK_CONFIGURE_FLAGS.

Also note that developers are encouraged to strive to make their code buildable without requiring any special configure option; thus, in general, you shouldn’t define AM_DISTCHECK_CONFIGURE_FLAGS. However, there might be few scenarios in which the use of this variable is justified. GNU m4 offers an example. GNU m4 configures by default with its experimental and seldom used "changeword" feature disabled; so in its case it is useful to have make distcheck run configure with the --with-changeword option, to ensure that the code for changeword support still compiles correctly. GNU m4 also employs the AM_DISTCHECK_CONFIGURE_FLAGS variable to stress-test the use of --program-prefix=g, since at one point the m4 build system had a bug where make installcheck was wrongly assuming it could blindly test "m4", rather than the just-installed "gm4".

distcheck-hook

If the distcheck-hook rule is defined in your top-level Makefile.am, then it will be invoked by distcheck after the new distribution has been unpacked, but before the unpacked copy is configured and built. Your distcheck-hook can do almost anything, though as always caution is advised. Generally this hook is used to check for potential distribution errors not caught by the standard mechanism. Note that distcheck-hook as well as AM_DISTCHECK_CONFIGURE_FLAGS and DISTCHECK_CONFIGURE_FLAGS are not honored in a subpackage Makefile.am, but the flags from AM_DISTCHECK_CONFIGURE_FLAGS and DISTCHECK_CONFIGURE_FLAGS are passed down to the configure script of the subpackage.

distcleancheck

Speaking of potential distribution errors, distcheck also ensures that the distclean rule actually removes all built files. This is done by running ‘make distcleancheck’ at the end of the VPATH build. By default, distcleancheck will run distclean and then make sure the build tree has been emptied by running ‘$(distcleancheck_listfiles)’. Usually this check will find generated files that you forgot to add to the DISTCLEANFILES variable (see What Gets Cleaned).

The distcleancheck behavior should be OK for most packages, otherwise you have the possibility to override the definition of either the distcleancheck rule, or the ‘$(distcleancheck_listfiles)’ variable. For instance, to disable distcleancheck completely, add the following rule to your top-level Makefile.am:

distcleancheck:
        @:

If you want distcleancheck to ignore built files that have not been cleaned because they are also part of the distribution, add the following definition instead:

distcleancheck_listfiles = \
  find . -type f -exec sh -c 'test -f $(srcdir)/$$1 || echo $$1' \
       sh '{}' ';'

The above definition is not the default because it’s usually an error if your Makefiles cause some distributed files to be rebuilt when the user build the package. (Think about the user missing the tool required to build the file; or if the required tool is built by your package, consider the cross-compilation case where it can’t be run.) There is an entry in the FAQ about this (see Errors with distclean), make sure you read it before playing with distcleancheck_listfiles.

distuninstallcheck

distcheck also checks that the uninstall rule works properly, both for ordinary and DESTDIR builds. It does this by invoking ‘make uninstall’, and then it checks the install tree to see if any files are left over. This check will make sure that you correctly coded your uninstall-related rules.

By default, the checking is done by the distuninstallcheck rule, and the list of files in the install tree is generated by ‘$(distuninstallcheck_listfiles)’ (this is a variable whose value is a shell command to run that prints the list of files to stdout).

Either of these can be overridden to modify the behavior of distcheck. For instance, to disable this check completely, you would write:

distuninstallcheck:
        @: