#include <assert.h>
#include <signal.h>
#include <stdlib.h>
#include <sys/wait.h>
#include <unistd.h>

#include "test_helpers.h"

static void wait_until_child_exits(pid_t pid) {
    siginfo_t info;
    for (int i = 0; i < 50; ++i) {
        info.si_pid = 0;
        int ret = waitid(P_PID, pid, &info, WEXITED | WNOHANG | WNOWAIT);
        ERROR_IF(waitid, ret, == -1);
        if (info.si_pid == pid) {
            assert(info.si_code == CLD_EXITED);
            assert(info.si_status == 42);
            return;
        }
        usleep(10000);
    }
    assert(!"waitid never observed child exit");
}

int main(void) {
    pid_t pid = fork();
    ERROR_IF(fork, pid, == -1);

    if (pid == 0) {
        usleep(50000);
        _Exit(42);
    }

    siginfo_t info;
    info.si_pid = 0;
    int ret = waitid(P_PID, pid, &info, WEXITED | WNOHANG | WNOWAIT);
    ERROR_IF(waitid, ret, == -1);
    assert(info.si_pid == 0);

    wait_until_child_exits(pid);

    int status = 0;
    pid_t waited = waitpid(pid, &status, 0);
    ERROR_IF(waitpid, waited, == -1);
    assert(waited == pid);
    assert(WIFEXITED(status));
    assert(WEXITSTATUS(status) == 42);

    return EXIT_SUCCESS;
}