cc -pthread  -Wall -Wextra -Werror=implicit-function-declaration unistd/getresuid.c -o unistd/getresuid -D_GNU_SOURCE -D_BSD_SOURCE -D_ALL_SOURCE -D_DEFAULT_SOURCE  -lm -lpthread  -liconv
unistd/getresuid.c:11:7: error: call to undeclared function 'getresuid'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
   11 |         if ( getresuid(&ruid, &euid, &suid) < 0 )
      |              ^
1 error generated.