Make build system for MEX files compatible with future automake versions

In future versions of automake, the subdir-objects option will be activated by default. This option breaks the way we build the MEX files. We need to redesign the build system for MEX files, or find a workaround.

Note that we won't need to redesign the build system. We can simply include:

AUTOMAKE_OPTIONS = subdir-objects

at the top of matlab/mex.am, octave/mex.am or any in any .am files in SUBDIRS that don't include the previous two

It seems as though subdir-objects being active by default causes a bug to which we're susceptible: namely that the .Po dependency files needed to compile are not created in the right place. This is a known bug (see also this). Automake 2.0 will not be created until this bug is fixed as at that point subdir-objects will be on "unconditionally," so we will have to deal with the warnings until then.

@houtanb I don't understand: on the one hand you say that "we will have to deal with the warnings until then." and you reference a commit "fix automake warnings¨

@MichelJuillard yes this is my fault. e7b4bf5 is in my personal repository because I wanted to test it on karaba before pushing it to dynare.git. I forgot that in referencing this issue from the commit, even if I push it to my personal repository, it shows up on these issues. The fix does indeed remove the warnings, but then building the mex files fails.

We need to make clear that #466 (closed) is closed without e7b4bf5 and that warnings can't be eliminated for now and until automake 2.0 is released

But #466 (closed) is not closed

but is should be closed, no?

I don't think so because it's still an issue for the same reason we created it 2 years ago when we first discovered it. On OS X I had these warnings but they did not exist in Debian because the automake version was old. We created the issue regardless because it was an issue and would continue to be. In my opinion, we should only remove the issue if we don't plan to fix this.

So let's state very clearly that this issue can't be solved for now and that we wait for the release of Automake 2.0

assigned to @sebastien and unassigned @houtanb

Actually we will have to redesign the build system for MEX files once subdir-objects becomes the default (in Automake 2.0). Because with this option, object files are placed in the same directory as the source, which means that we cannot build MEX for MATLAB and MEX for Octave in parallel (of course one solution would be to give up that possibility, but this would be annoying).

Also note that the automake bug mentioned by @houtanb above has been fixed in Automake 1.16.

closed via commit bdc95f23