cc -O2 -pthread  -Wall -Wextra -Werror=implicit-function-declaration unistd/setresgid.c -o unistd/setresgid -D_GNU_SOURCE -D_BSD_SOURCE -D_ALL_SOURCE -D_DEFAULT_SOURCE  -lm -lpthread -lrt  -lintl -lcrypt
unistd/setresgid.c: In function 'main':
unistd/setresgid.c:11:7: error: implicit declaration of function 'getresgid'; did you mean 'setregid'? [-Werror=implicit-function-declaration]
   11 |  if ( getresgid(&rgid, &egid, &sgid) < 0 )
      |       ^~~~~~~~~
      |       setregid
unistd/setresgid.c:13:7: error: implicit declaration of function 'setresgid'; did you mean 'setregid'? [-Werror=implicit-function-declaration]
   13 |  if ( setresgid(rgid, egid, sgid) < 0 )
      |       ^~~~~~~~~
      |       setregid
cc1: some warnings being treated as errors