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

static void sig_quit(int);

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

  if (signal(SIGQUIT, sig_quit) == SIG_ERR) {
    printf("can't catch SIGQUIT\n");
    return -1;
  }

  sigemptyset(&newmask);
  sigaddset(&newmask, SIGQUIT);
  if (sigprocmask(SIG_BLOCK, &newmask, &oldmask) < 0) {
    printf("SIG_BLOCK error\n");
    return -1;
  }

  sleep(5);

  if (sigpending(&pendmask) < 0) {
    printf("sigpeding error\n");
    return -1;
  }
  if (sigismember(&pendmask, SIGQUIT)) {
    printf("\nSIGQUIT pending\n");
  }

  if (sigprocmask(SIG_SETMASK, &oldmask, NULL) < 0) {
    printf("SIG_SETMASK error\n");
    return -1;
  }

  printf("SIGQUIT unblocked\n");

  sleep(5);

  return 0;
}

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