#include <signal.h>

int sigismember(const sigset_t* set, int sig) {
  unsigned s = sig - 1;
  if (s >= _NSIG - 1)
    return 0;
  return !!(set->__bits[s / 8 / sizeof *set->__bits] &
            1UL << (s & 8 * sizeof *set->__bits - 1));
}