// Copyright 2024 Justine Alexandra Roberts Tunney
//
// Permission to use, copy, modify, and/or distribute this software for
// any purpose with or without fee is hereby granted, provided that the
// above copyright notice and this permission notice appear in all copies.
//
// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL
// WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED
// WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE
// AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
// DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
// PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
// TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
// PERFORMANCE OF THIS SOFTWARE.

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

volatile int handler_invoked;

void signal_handler(int signum) {
  handler_invoked = 1;
}

int main() {
  sigset_t mask, oldmask;
  struct sigaction sa, current_sa;

  sa.sa_handler = signal_handler;
  sa.sa_flags = SA_RESETHAND;
  sigemptyset(&sa.sa_mask);

  if (sigaction(SIGINT, &sa, 0) == -1)
    return 1;

  sigemptyset(&mask);
  sigaddset(&mask, SIGINT);
  if (sigprocmask(SIG_BLOCK, &mask, &oldmask) == -1)
    return 2;

  int pid = fork();
  if (pid == -1) {
    return 3;
  } else if (pid == 0) {
    kill(getppid(), SIGINT);
    return 0;
  } else {
    sigsuspend(&oldmask);
    if (!handler_invoked)
      return 4;
    if (sigaction(SIGINT, 0, &current_sa) == -1)
      return 5;
    if (current_sa.sa_handler != SIG_DFL)
      return 6;
    return 0;
  }
}