pthreads在C - pthread_exit中

#include<stdio.h>
#include <stdlib.h>
#include <pthread.h>

void *my_thread(void *arg) {
    printf("Thread %ld: starting...\n", (long)arg);
    sleep(2);
    printf("Thread %ld: exiting...\n", (long)arg);
    pthread_exit(NULL);
}

int main() {
    pthread_t thread_id;
    int rc;
    long tnum = 1;

    rc = pthread_create(&thread_id, NULL, my_thread, (void *)tnum);
    if (rc != 0) {
        perror("Failed to create thread");
        exit(1);
    }

    pthread_join(thread_id, NULL);
    printf("Main: thread has joined\n");

    return 0;
}