#include <errno.h>
#include <signal.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/wait.h>
#include <unistd.h>

static void
segv_handler (int sig, siginfo_t *si, void *unused)
{
    _exit (EXIT_SUCCESS);
}

static void
die (const char *msg, int err)
{
    if (err)
        perror (msg);
    else
        fprintf (stderr, "%s\n", msg);

    abort ();
}

static void
do_expect_signal (void (*fn)(void))
{
    struct sigaction sa;

    sa.sa_flags = SA_SIGINFO;
    sigemptyset (&sa.sa_mask);
    sa.sa_sigaction = segv_handler;
    if (sigaction (SIGSEGV, &sa, NULL) == -1)
        die ("sigaction failed", errno);

    (*fn)();

    _exit (EXIT_FAILURE);
}

static bool
expect_signal (void (*fn)(void))
{
    pid_t pid, wp;
    int status;

    pid = fork ();
    if (pid == -1)
        die ("fork failed", errno);

    if (pid == 0)
        do_expect_signal (fn); /* never returns */

    wp = waitpid (pid, &status, 0);
    if (wp != pid)
        die ("waitpid did not work", wp == -1 ? errno : 0);

    if (WIFEXITED (status) && WEXITSTATUS (status) == EXIT_SUCCESS)
        return true;

    return false;
}

static void
deref (void)
{
  *((char *)0) = 0;
}

static bool
fault (void)
{
  if (expect_signal(deref))
    {
      printf("Signal OK\n");
      return true;
    }
  return false;
}

int
main (int argc, char **argv)
{
  bool ok = true;
  ok = fault();
  if (ok)
    return EXIT_SUCCESS;
  return EXIT_FAILURE;
}