wait(2) with timeout using a timer

wait-with-timeout.c

#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
#include <time.h>
#include <sys/types.h>
#include <unistd.h>
#include <sys/syscall.h>
#include <stdbool.h>
#include <limits.h>
#include <sys/wait.h>
#include <errno.h>

void handler() {}

int main() {
  pid_t tid = (pid_t) syscall(SYS_gettid);

  int signum = SIGRTMIN + 4;

  timer_t timerid;
  struct sigevent event = {
    .sigev_notify = SIGEV_THREAD_ID,
    .sigev_signo = signum,
    ._sigev_un._tid = tid
  };
  if (timer_create(CLOCK_MONOTONIC, &event, &timerid) == -1) {
    perror("timer_create");
    exit(EXIT_FAILURE);
  }

  struct sigaction act = {
    .sa_handler = handler
  };
  if (sigaction(signum, &act, NULL) == -1) {
    perror("rt_sigaction");
    exit(EXIT_FAILURE);
  }

  pid_t child_pid = fork();
  if (child_pid == -1) {
    perror("fork");
    exit(EXIT_FAILURE);
  } else if (child_pid == 0) {
    // child
    while (true) sleep(UINT_MAX);
  }
  // parent

  struct itimerspec timerspec = {
    .it_value = {
      .tv_sec = 3
    }
  };
  if (timer_settime(timerid, 0, &timerspec, NULL) == -1) {
    perror("timer_settime");
    exit(EXIT_FAILURE);
  }

  int wstatus;
  pid_t dead_child = wait(&wstatus);
  if (dead_child == -1) {
    if (errno != EINTR) {
      perror("wait");
      exit(EXIT_FAILURE);
    }
  } else {
    fprintf(stderr, "wait exited successfully, returning %d\n", dead_child);
    return EXIT_FAILURE;
  }
  return EXIT_SUCCESS;
}