1#include <errno.h>
2#include <signal.h>
3
4int sigaddset(sigset_t* set, int sig) {
5    unsigned s = sig - 1;
6    if (s >= _NSIG - 1 || sig - 32U < 3) {
7        errno = EINVAL;
8        return -1;
9    }
10    set->__bits[s / 8 / sizeof *set->__bits] |= 1UL << (s & (8 * sizeof *set->__bits - 1));
11    return 0;
12}
13