#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <sched.h>
#include <linux/sched.h>
#include <unistd.h>
#include <sys/syscall.h>

#include <sys/types.h>
#include <sys/wait.h>
#include <signal.h>
#include <string.h>

#if !defined(WITH_SIGCHLD)
#define WITH_SIGCHLD 1
#endif

#if WITH_SIGCHLD == 1
/*
 * vsftpd 
 * sysutil.c vsf_sysutil_wait_reap_one()
 * standalone.c handle_sigchld()
 * 
 */
int vsf_sysutil_wait_reap_one(void)
{
    int retval = waitpid(-1, NULL, WNOHANG);
    if (retval == 0 || (retval < 0 && errno == ECHILD)) {
        /* No more children */
        return 0;
    }
    if (retval < 0) {
        perror("waitpid");
        exit(EXIT_FAILURE);
    }
    /* Got one */
    return retval;
}

int received;
int reaped;

void handle_sigchld(int sig)
{
    unsigned int reap_one = 1;

    received++;
    while (reap_one) {
        reap_one = (unsigned int) vsf_sysutil_wait_reap_one();
	if (reap_one)
            reaped++;
    }
}
#endif

int zombies;

int main(int argc, char *argv[])
{
    int i, ret;

#if WITH_SIGCHLD == 1
    /*
     * vsftpd sysutil.c vsf_sysutil_set_sighandler()
     */
    struct sigaction sa;
    memset(&sa, 0, sizeof(sa));
    sa.sa_handler = handle_sigchld;
    if (-1 == sigfillset(&sa.sa_mask)) {
        perror("sigfillset");
        exit(EXIT_FAILURE);
    }
    if (-1 == sigaction(SIGCHLD, &sa, NULL)) {
        perror("sigaction");
        exit(EXIT_FAILURE);
    }
    fprintf(stderr, "SIGCHLD handler enabled\n");
#else
    fprintf(stderr, "SIGCHLD handler not enabled\n");
#endif

    for (i = 0; i < 100; i++) {

//        if (0 == (ret = syscall(__NR_clone, CLONE_NEWPID | CLONE_NEWIPC | CLONE_NEWNET | CLONE_NEWUSER | SIGCHLD, NULL)))
        if (0 == (ret = syscall(__NR_clone, CLONE_NEWPID | SIGCHLD, NULL)))
            return 0;

        if (-1 == ret) {
            perror("clone");
            exit(EXIT_FAILURE);
        }

    }
#if 1
    while (1) {
	int res = waitpid(-1, NULL, WNOHANG);
	if (res < 0)
		break;
	if (!res)
		continue;
        zombies++;
    }
//    printf("received %d signals, reaped %d - %d zombies left\n", received, reaped, zombies);
//    sleep(1);
#endif
    return 0;
}