/*
 * Copyright (c) 2021 Alexey Dobriyan <adobriyan@gmail.com>
 *
 * Permission to use, copy, modify, and 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.
 */
// Test that /proc/*/task never contains "0".
#include <sys/types.h>
#include <dirent.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <pthread.h>

static pid_t pid = -1;

static void atexit_hook(void)
{
        if (pid > 0) {
                kill(pid, SIGKILL);
        }
}

static void *f(void *_)
{
        return NULL;
}

static void sigalrm(int _)
{
        exit(0);
}

int main(void)
{
        pid = fork();
        if (pid == 0) {
                /* child */
                while (1) {
                        pthread_t pth;
                        pthread_create(&pth, NULL, f, NULL);
                        pthread_join(pth, NULL);
                }
        } else if (pid > 0) {
                /* parent */
                atexit(atexit_hook);

                char buf[64];
                snprintf(buf, sizeof(buf), "/proc/%u/task", pid);

                signal(SIGALRM, sigalrm);
                alarm(1);

                while (1) {
                        DIR *d = opendir(buf);
                        struct dirent *de;
                        while ((de = readdir(d))) {
                                if (strcmp(de->d_name, "0") == 0) {
                                        exit(1);
                                }
                        }
                        closedir(d);
                }

                return 0;
        } else {
                perror("fork");
                return 1;
        }
}