__sigword
#define __sigaddset(s, n) ((s)->__bits[__sigword(n)] |= __sigmask(n))
#define __sigdelset(s, n) ((s)->__bits[__sigword(n)] &= ~__sigmask(n))
#define __sigismember(s, n) (((s)->__bits[__sigword(n)] & __sigmask(n)) != 0)