pthread中PTHREAD_CREATE_JOINABLE的用法是什么？

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

void *thread_func(void *arg)
{
    int *num = (int *)arg;
    printf("thread %d start\n", *num);
    sleep(1);
    printf("thread %d end\n", *num);
    pthread_exit((void *)(*num));
}

int main(void)
{
    pthread_t thread_id[5];
    int thread_num[5] = {1, 2, 3, 4, 5};
    int i, ret;

    // 设置线程属性
    pthread_attr_t attr;
    pthread_attr_init(&attr);
    pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_JOINABLE);

    // 创建线程
    for (i = 0; i < 5; i++) {
        ret = pthread_create(&thread_id[i], &attr, thread_func, (void *)&thread_num[i]);
        if (ret != 0) {
            printf("create thread %d failed\n", i);
            exit(1);
        }
    }

    // 等待线程结束并获取返回值
    for (i = 0; i < 5; i++) {
        void *thread_result;
        ret = pthread_join(thread_id[i], &thread_result);
        if (ret != 0) {
            printf("join thread %d failed\n", i);
            exit(1);
        }
        printf("thread %d result: %d\n", i, (int)thread_result);
    }

    // 销毁线程属性
    pthread_attr_destroy(&attr);

    return 0;
}