Build with -std=gnu99 instead of -std=c99

[fweimer-rh]

The latter activates strict POSIX mode with glibc, which disables the declaration of usleep in <unistd.h>, leading to an implicit function declaration.

Related to:

• https://fedoraproject.org/wiki/Changes/PortingToModernC
• https://fedoraproject.org/wiki/Toolchain/PortingToModernC

[posva]

Thanks a lot for the links, I will try to review this and others during the holidays!

[Kreijstal]

that would create libc dependency :((((

[TimB87]

This seems to fix a build error I see that can be worked around with -Wno-implicit-function-declaration.

../catimg-2.8.0/src/catimg.c:181:21: error: implicit declaration of function 'usleep'; did you mean 'sleep'? [-Wimplicit-function-declaration]
  181 |                     usleep(img.delays[frame - 1] * 10000);
      |                     ^~~~~~
      |                     sleep
[..]
../catimg-2.8.0/src/sh_utils.c:60:14: error: implicit declaration of function 'fileno' [-Wimplicit-function-declaration]
   60 |     int fd = fileno(stdin);
      |              ^~~~~~