cc -O2 -pipe  -pthread  -Wall -Wextra -Werror -Wno-error=deprecated -Wno-error=deprecated-declarations unistd/_POSIX2_SYMLINKS.c -o unistd/_POSIX2_SYMLINKS -D_POSIX_C_SOURCE=202405L  -lm -lpthread 
unistd/_POSIX2_SYMLINKS.c:3:17: error: use of undeclared identifier '_POSIX2_SYMLINKS'
int const foo = _POSIX2_SYMLINKS;
                ^
1 error generated.