signal_handler
signal_handler(SIGHUP);
if (set_signal(signals[i], signal_handler) < 0) {
extern RETSIGTYPE signal_handler(int);
signal(sig, signal_handler);
act.sa_handler = signal_handler;
if (signal(signals[i], signal_handler) == SIG_IGN) {
typedef void signal_handler(int);
typedef signal_handler(*sys_signal)(signal_handler);
signal_handler handler = ptr;
signal_handler fp)
typedef void(*signal_handler)(int);