Deprecated function prototypes in CHOLMOD

[orlitzky]

If I compile cholmod with -Werror=strict-prototypes in my CFLAGS, I get a few errors like...

/var/lib/portage/tmp/portage/sci-libs/cholmod-4.0.3/work/SuiteSparse-7.0.0/CHOLMOD/SuiteSparse_metis/GKlib/gk_proto.h:91:1: error: function declaration isn't a prototype [-Werror=strict-prototypes]
   91 | int    gk_malloc_init();
      | ^~~

The reason for the error is that the latest C standard draft requires (void) instead of () for prototypes of functions that take no arguments. Why am I shooting myself in the foot, you're thinking? We're trying to avoid compilation errors in the future, when C23 is ratified and people upgrade their compilers:

• https://wiki.gentoo.org/wiki/Modern_C_porting
• https://fedoraproject.org/wiki/Changes/PortingToModernC

The fix is trivial and harmless so we're trying to get a head start.

[DrTimothyAldenDavis]

Thanks for the feedback. Those errors are coming from another library (METIS) that I've included in SuiteSparse. I can't use an external -lmetis because of various issues in the default METIS library. I've tried to keep my fixes as minimal as possible but didn't check for this issue. I turned on -Wstrict-prototypes for all of SuiteSparse and it looks like this issue is only in METIS (correct me if I'm wrong).

I've fixed the non-standard prototypes in METIS, and just pushed the fix to the dev2 branch. Can you give it a try? If this looks OK, I'll add it to the SuiteSparse v7.1.0.beta2 pre-release, once all the CI passes.

[DrTimothyAldenDavis]

See #338

[orlitzky]

Thanks, METIS (in cholmod) was the only component that gave me problems. I tracked down the upstream project and reported the same issue (KarypisLab/GKlib#27) so that maybe you don't have to be responsible for the fix indefinitely.

[DrTimothyAldenDavis]

Thanks -- that's helpful. I would need to manually upgrade to the next release of METIS, since METIS is embedded into SuiteSparse because of some other changes I've had to make (mainly because I have to redefine the integer sizes and memory managers used, which would conflict with a default -lmetis so I move this copy of METIS to a different namespace). The fewer changes I have, the better, however.

This is now fixed in the dev2 branch and will appear in SuiteSparse v7.1.0.beta2, so I'll close this issue now.

Thanks again for the helpful feedback.