#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

void
pr_mask(const char *str)
{
	sigset_t	sigset;
	int		errno_save;

	errno_save = errno;
	if (sigprocmask(0, NULL, &sigset) < 0) {
		fprintf(stderr, "sigprocmask error\n");
		exit(1);
	}

	printf("%s", str);

	if (sigismember(&sigset, SIGINT))	printf("SIGINT ");
	if (sigismember(&sigset, SIGQUIT))	printf("SIGQUIT ");
	if (sigismember(&sigset, SIGUSR1))	printf("SIGUSR1 ");
	if (sigismember(&sigset, SIGALRM))	printf("SIGALRM ");

	printf("\n");
	errno = errno_save;
}

static void
sig_quit(int signo) {
	printf("caught SIGQUIT\n");
	if (signal(SIGQUIT, SIG_DFL) == SIG_ERR) {
		fprintf(stderr, "can't reset SIGQUIT\n");
		exit(1);
	}
}

int main() {
	sigset_t	newmask, oldmask, pendmask;

	if(signal(SIGQUIT, sig_quit) == SIG_ERR) {
		fprintf(stderr, "can't set signal handler\n");
		exit(1);
	}

	sigemptyset(&newmask);
	sigaddset(&newmask, SIGQUIT);

	if (sigprocmask(SIG_BLOCK, &newmask, &oldmask) < 0) {
		fprintf(stderr, "SIG_BLOCK error\n");
		exit(1);
	}

	sleep(5);

	if (sigpending(&pendmask) < 0) {
		fprintf(stderr, "sigpending error\n");
		exit(1);
	}

	if (sigismember(&pendmask, SIGQUIT) < 0) {
		fprintf(stderr, "sigismember error\n");
		exit(1);
	}

	if (sigprocmask(SIG_SETMASK, &oldmask, NULL) < 0) {
		fprintf(stderr, "SIG_SETMASK error\n");
		exit(1);
	}

	printf("SIGQUIT unblocked\n");

	sleep(5);
	exit(0);
}