gcc -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 -lxnet -lsocket -latomic
unistd/setresgid.c: In function ‘main’:
unistd/setresgid.c:11:14: error: implicit declaration of function ‘getresgid’; did you mean ‘setregid’? [-Wimplicit-function-declaration]
   11 |         if ( getresgid(&rgid, &egid, &sgid) < 0 )
      |              ^~~~~~~~~
      |              setregid
unistd/setresgid.c:13:14: error: implicit declaration of function ‘setresgid’; did you mean ‘setregid’? [-Wimplicit-function-declaration]
   13 |         if ( setresgid(rgid, egid, sgid) < 0 )
      |              ^~~~~~~~~
      |              setregid