Bug 2336029

I'm experimentally rebuilding rawhide with the not-yet-released GCC 15 to see if anything breaks, and to help write the porting guide.  See https://fedoraproject.org/wiki/User:Dmalcolm/gcc-15

My test build with GCC 15 failed:
https://copr.fedorainfracloud.org/coprs/dmalcolm/gcc-15-smoketest-3.failed/build/8476061/

whereas my test build with GCC 14 succeeded:
https://copr.fedorainfracloud.org/coprs/dmalcolm/gcc-15-smoketest-3.failed.checker/build/8477620/

Looking at the failure logs e.g.
https://download.copr.fedorainfracloud.org/results/dmalcolm/gcc-15-smoketest-3.failed/fedora-rawhide-x86_64/08476061-abook/builder-live.log.gz

I see:

mbswidth.c:66:5: error: conflicting types for ‘wcwidth’; have ‘int(void)’
   66 | int wcwidth ();
      |     ^~~~~~~
In file included from mbswidth.c:42:
/usr/include/wchar.h:392:12: note: previous declaration of ‘wcwidth’ with type ‘int(wchar_t)’ {aka ‘int(int)’}
  392 | extern int wcwidth (wchar_t __c) __THROW;
      |            ^~~~~~~
mbswidth.c: In function ‘mbsnwidth’:
mbswidth.c:185:25: error: too many arguments to function ‘wcwidth’
  185 |                     w = wcwidth (wc);
      |                         ^~~~~~~
mbswidth.c:66:5: note: declared here
   66 | int wcwidth ();
      |     ^~~~~~~
mbswidth.c: In function ‘mbsnbytes’:
mbswidth.c:303:25: error: too many arguments to function ‘wcwidth’
  303 |                     w = wcwidth (wc);
      |                         ^~~~~~~
mbswidth.c:66:5: note: declared here
   66 | int wcwidth ();
      |     ^~~~~~~



This is probably due to GCC 15 now defaulting to -std=gnu23, whereas GCC 14 defaulted to -std=gnu17, and C23 is stricter about function prototypes than C17.  It's probably fixable by fixing the function prototypes (or by manually adding -std=gnu17 to the C build flags)


Reproducible: Always