Found the following significant warnings:
  2k.c:25:20: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  2k.c:25:33: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  2k.c:27:20: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  2k.c:27:43: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  2k.c:169:20: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  2k.c:230:27: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  2k.c:299:20: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  2k.c:314:15: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  gcontrol_c.c:341:13: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  gcontrol_c.c:343:23: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  gcontrol_c.c:345:21: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  gcontrol_c.c:366:35: warning: passing arguments to 'rgs_' without a prototype is deprecated in all versions of C and is not supported in C2x [-Wdeprecated-non-prototype]
  gcontrol_c.c:368:33: warning: passing arguments to 'rgkm3_' without a prototype is deprecated in all versions of C and is not supported in C2x [-Wdeprecated-non-prototype]
  gcontrol_c.c:345:17: warning: a function declaration without a prototype is deprecated in all versions of C and is treated as a zero-parameter prototype in C2x, conflicting with a subsequent definition [-Wdeprecated-non-prototype]
  gcontrol_c.c:385:13: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  gcontrol_c.c:385:10: warning: a function declaration without a prototype is deprecated in all versions of C and is treated as a zero-parameter prototype in C2x, conflicting with a previous declaration [-Wdeprecated-non-prototype]
  gcontrol_c.c:385:20: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  gcontrol_c.c:385:17: warning: a function declaration without a prototype is deprecated in all versions of C and is treated as a zero-parameter prototype in C2x, conflicting with a previous declaration [-Wdeprecated-non-prototype]
  gcontrol_c.c:387:22: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  gcontrol_c.c:387:17: warning: a function declaration without a prototype is deprecated in all versions of C and is treated as a zero-parameter prototype in C2x, conflicting with a previous declaration [-Wdeprecated-non-prototype]
  gcontrol_c.c:343:17: warning: a function declaration without a prototype is deprecated in all versions of C and is treated as a zero-parameter prototype in C2x, conflicting with a subsequent definition [-Wdeprecated-non-prototype]
  gcontrol_c.c:408:14: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  gcontrol_c.c:408:10: warning: a function declaration without a prototype is deprecated in all versions of C and is treated as a zero-parameter prototype in C2x, conflicting with a previous declaration [-Wdeprecated-non-prototype]
  gcontrol_c.c:408:21: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  gcontrol_c.c:408:18: warning: a function declaration without a prototype is deprecated in all versions of C and is treated as a zero-parameter prototype in C2x, conflicting with a previous declaration [-Wdeprecated-non-prototype]
  gcontrol_c.c:410:22: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  gcontrol_c.c:410:17: warning: a function declaration without a prototype is deprecated in all versions of C and is treated as a zero-parameter prototype in C2x, conflicting with a previous declaration [-Wdeprecated-non-prototype]
  gcontrol_c.c:757:53: warning: if statement has empty body [-Wempty-body]
  gif_c.c:39:28: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  gif_c.c:39:41: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  gif_c.c:40:26: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  gif_c.c:40:41: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  gif_c.c:41:29: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  gif_c.c:47:24: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  gif_c.c:56:33: warning: passing arguments to 'find_vertex' without a prototype is deprecated in all versions of C and is not supported in C2x [-Wdeprecated-non-prototype]
  gif_c.c:59:24: warning: passing arguments to 'find_vertex' without a prototype is deprecated in all versions of C and is not supported in C2x [-Wdeprecated-non-prototype]
  gif_c.c:60:21: warning: passing arguments to 'connected' without a prototype is deprecated in all versions of C and is not supported in C2x [-Wdeprecated-non-prototype]
  gif_c.c:60:41: warning: passing arguments to 'make_edge' without a prototype is deprecated in all versions of C and is not supported in C2x [-Wdeprecated-non-prototype]
  gif_c.c:64:24: warning: passing arguments to 'find_vertex' without a prototype is deprecated in all versions of C and is not supported in C2x [-Wdeprecated-non-prototype]
  gif_c.c:65:21: warning: passing arguments to 'connected' without a prototype is deprecated in all versions of C and is not supported in C2x [-Wdeprecated-non-prototype]
  gif_c.c:65:41: warning: passing arguments to 'make_edge' without a prototype is deprecated in all versions of C and is not supported in C2x [-Wdeprecated-non-prototype]
  gif_c.c:75:22: warning: passing arguments to 'find_vertex' without a prototype is deprecated in all versions of C and is not supported in C2x [-Wdeprecated-non-prototype]
  gif_c.c:76:22: warning: passing arguments to 'new_proband' without a prototype is deprecated in all versions of C and is not supported in C2x [-Wdeprecated-non-prototype]
  gif_c.c:111:22: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  gif_c.c:137:20: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  gif_c.c:41:18: warning: a function declaration without a prototype is deprecated in all versions of C and is treated as a zero-parameter prototype in C2x, conflicting with a subsequent definition [-Wdeprecated-non-prototype]
  gif_c.c:163:33: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  gif_c.c:40:30: warning: a function declaration without a prototype is deprecated in all versions of C and is treated as a zero-parameter prototype in C2x, conflicting with a subsequent definition [-Wdeprecated-non-prototype]
  gif_c.c:187:18: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  gif_c.c:39:32: warning: a function declaration without a prototype is deprecated in all versions of C and is treated as a zero-parameter prototype in C2x, conflicting with a subsequent definition [-Wdeprecated-non-prototype]
  gif_c.c:40:17: warning: a function declaration without a prototype is deprecated in all versions of C and is treated as a zero-parameter prototype in C2x, conflicting with a subsequent definition [-Wdeprecated-non-prototype]
  gif_c.c:249:20: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  gif_c.c:279:17: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  hap_c.c:1348:11: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  ./gdef.h:31:24: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  makeped_c.c:161:6: warning: a function definition without a prototype is deprecated in all versions of C and is not supported in C2x [-Wdeprecated-non-prototype]
  makeped_c.c:175:6: warning: a function definition without a prototype is deprecated in all versions of C and is not supported in C2x [-Wdeprecated-non-prototype]
  makeped_c.c:187:8: warning: a function definition without a prototype is deprecated in all versions of C and is not supported in C2x [-Wdeprecated-non-prototype]
  makeped_c.c:217:8: warning: a function definition without a prototype is deprecated in all versions of C and is not supported in C2x [-Wdeprecated-non-prototype]
  makeped_c.c:250:6: warning: a function definition without a prototype is deprecated in all versions of C and is not supported in C2x [-Wdeprecated-non-prototype]
  makeped_c.c:330:6: warning: a function definition without a prototype is deprecated in all versions of C and is not supported in C2x [-Wdeprecated-non-prototype]
  makeped_c.c:407:6: warning: a function definition without a prototype is deprecated in all versions of C and is not supported in C2x [-Wdeprecated-non-prototype]
  makeped_c.c:436:13: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  makeped_c.c:520:14: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  makeped_c.c:600:6: warning: a function definition without a prototype is deprecated in all versions of C and is not supported in C2x [-Wdeprecated-non-prototype]
  makeped_c.c:640:8: warning: a function definition without a prototype is deprecated in all versions of C and is not supported in C2x [-Wdeprecated-non-prototype]
  makeped_c.c:672:6: warning: a function definition without a prototype is deprecated in all versions of C and is not supported in C2x [-Wdeprecated-non-prototype]
  makeped_c.c:852:16: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  makeped_c.c:971:8: warning: a function definition without a prototype is deprecated in all versions of C and is not supported in C2x [-Wdeprecated-non-prototype]
  makeped_c.c:998:6: warning: a function definition without a prototype is deprecated in all versions of C and is not supported in C2x [-Wdeprecated-non-prototype]
  makeped_c.c:1038:6: warning: a function definition without a prototype is deprecated in all versions of C and is not supported in C2x [-Wdeprecated-non-prototype]
  makeped_c.c:1076:19: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  makeped_c.c:1220:18: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  makeped_c.c:1289:19: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  makeped_c.c:1424:14: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  makeped_c.c:1539:8: warning: a function definition without a prototype is deprecated in all versions of C and is not supported in C2x [-Wdeprecated-non-prototype]
  makeped_c.c:1560:15: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  makeped_c.c:1584:15: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  makeped_c.c:1626:19: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  makeped_c.c:1649:21: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
See '/home/hornik/tmp/R.check/r-devel-clang/Work/PKGS/gap.Rcheck/00install.out' for details.