signal_handler
signal(SIGCHLD, signal_handler);
signal(SIGIO, signal_handler);
signal(SIGURG, signal_handler);
ssh_signal(SIGHUP, signal_handler);
ssh_signal(SIGINT, signal_handler);
ssh_signal(SIGQUIT, signal_handler);
ssh_signal(SIGTERM, signal_handler);
static void signal_handler(int, short, void *);
signal_set(&ev_sigterm, SIGTERM, signal_handler, NULL);
signal_set(&ev_sighup, SIGHUP, signal_handler, NULL);
signal_set(&ev_sigint, SIGINT, signal_handler, NULL);
signal_set(&ev_siginfo, SIGINFO, signal_handler, NULL);
sa.sa_handler = signal_handler;