Bug#1059917: guake: build race for /usr/share/glib-2.0/schemas/gschemas.compiled

[James Addison]

Source: guake
Version: 3.10-1
Severity: normal
User: reproducible-builds at lists.alioth.debian.org
X-Debbugs-Cc: reproducible-bugs at lists.alioth.debian.org

Dear Maintainer,

I'm an occasional volunteer for the Reproducible Builds[0] project,
and recently noticed that the quake package failed to build reproducibly
from source.

The difference between the builds was the presence-or-absence of a file at
the path /usr/share/glib-2.0/schemas/gschemas.compiled in the built package.

This file should not be shipped in the contents of distro packages[1][2] (but
can be regenerated by them after installation, as guake's postinst script
does).

So: why is the file _sometimes_ found when building the guake package from
source?  It think it's due to a race condition in the Makefile:

  install-system: install-schemas compile-shemas install-locale install-guake


The 'compile-shemas' (sic) target expects to compile source .xml files from a
parameterized $(DESTDIR)$(gsettingsschemadir) path that expands to the build
dir with an /glib-2.0/schemas suffix.  However: the .xml files are created in
that path by the 'install-schemas' target.

Even though 'compile-shemas' is listed _after_ 'install-schemas', it's possible
for 'make' to run them both in parallel when enabled[3].

If the files aren't there by the time 'compile-shemas' runs, we see a message:

  No schema files found: doing nothing.

...and no gschemas.compiled file is created (as is desired!  but by relying on
a race condition).


One fix here could be to update the Makefile so that it maps the dependency
between the two relevant build targets correctly, ensuring that
'install-schemas' runs before 'compile-shemas'.

However: I think a simpler fix for Debian's packaging could be to set the
COMPILE_SCHEMAS environment flag used by the Makefile to zero, to disable
creation of the glib-2.0 gschemas.compiled file -- avoiding the race condition
entirely.

Regards,
James

[0] - https://reproducible-builds.org/

[1] - https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=884142

[2] - https://github.com/Guake/guake/pull/1893#discussion_r707307822

[3] - https://www.gnu.org/software/make/manual/html_node/Parallel.html