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/8476031/

whereas my test build with GCC 14 succeeded:
  https://copr.fedorainfracloud.org/coprs/dmalcolm/gcc-15-smoketest-3.failed.checker/build/8476693/

In the logs for the failed build I see:

main.c:564:33: error: assignment to ‘int (*)(void)’ from incompatible pointer type ‘int (*)(struct rECORD *, struct rECORD *)’ [-Wincompatible-pointer-types]
  564 |     { if (rsc_sort_reverse) fct = rec_lt_cased;    /*                        */
      |                                 ^
main.c:565:33: error: assignment to ‘int (*)(void)’ from incompatible pointer type ‘int (*)(struct rECORD *, struct rECORD *)’ [-Wincompatible-pointer-types]
  565 |       else                  fct = rec_gt_cased;    /*                        */
      |                                 ^
main.c:568:33: error: assignment to ‘int (*)(void)’ from incompatible pointer type ‘int (*)(struct rECORD *, struct rECORD *)’ [-Wincompatible-pointer-types]
  568 |     { if (rsc_sort_reverse) fct = rec_lt;          /*                        */
      |                                 ^
main.c:569:33: error: assignment to ‘int (*)(void)’ from incompatible pointer type ‘int (*)(struct rECORD *, struct rECORD *)’ [-Wincompatible-pointer-types]
  569 |       else                  fct = rec_gt;          /*                        */
      |                                 ^
main.c:571:21: error: passing argument 2 of ‘db_sort’ from incompatible pointer type [-Wincompatible-pointer-types]
  571 |     db_sort(the_db, fct);                          /*                        */
      |                     ^~~
      |                     |
      |                     int (*)(void)
In file included from include/bibtool/expand.h:32,
                 from include/bibtool/bibtool.h:46,
                 from main.c:64:
include/bibtool/database.h:173:33: note: expected ‘int (*)(struct rECORD *, struct rECORD *)’ but argument is of type ‘int (*)(void)’
  173 |  void db_sort _ARG((DB db,int (*less)_ARG((Record, Record))));/*             */
      |                                 ^
include/bibtool/database.h:158:17: note: in definition of macro ‘_ARG’
  158 | #define _ARG(A) A
      |                 ^


This may be 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 might be fixable by fixing the function prototypes (or by manually adding -std=gnu17 to the C build flags), but it looks like the function prototypes need fixing.


Reproducible: Always