cc -O2 -pipe  -pthread  -Wall -Wextra -Werror -Wno-error=deprecated -Wno-error=deprecated-declarations semaphore/sem_clockwait.c -o semaphore/sem_clockwait -D_POSIX_C_SOURCE=202405L  -lm -lpthread 
semaphore/sem_clockwait.c:5:29: error: type specifier missing, defaults to 'int'; ISO C99 and later do not support implicit int [-Werror,-Wimplicit-int]
int (*foo)(sem_t *restrict, clockid_t, const struct timespec *restrict) = sem_clockwait;
                            ^
                            int
semaphore/sem_clockwait.c:5:75: error: use of undeclared identifier 'sem_clockwait'
int (*foo)(sem_t *restrict, clockid_t, const struct timespec *restrict) = sem_clockwait;
                                                                          ^
2 errors generated.