cc -O2 -pipe  -pthread  -Wall -Wextra -Werror -Wno-error=deprecated -Wno-error=deprecated-declarations fcntl/S_ISGID.c -o fcntl/S_ISGID -D_POSIX_C_SOURCE=202405L  -lm -lpthread 
fcntl/S_ISGID.c:3:2: error: "S_ISGID is not defined"
#error "S_ISGID is not defined"
 ^
1 error generated.