主函数返回使用pthread_exit(NULL)的作用，和return 0有什么区别？

pthread_exit 表示线程结束，退出当前线程。
在main函数结尾时使用return 0 和使用pthread_exit有什么区别呢

1.使用return 0；

#include "windows.h"
#include <bits/stdc++.h>
using namespace std;

#define MAX_NUM 4

typedef struct thread_info
{
    int id;
    string name;
} thread_info;

//void*只是表示可以传入任意类型的指针,返回值也可以是任意类型的指针
void *print_hello(void *arg)
{
    Sleep(2000);
    thread_info *ifo = (thread_info *)arg;
    cout << "child thread" << endl;
    // int id = ifo->id;
    // string name = ifo->name;
    // cout << "ID: " << id << " NAME" << name << endl;
}
int main()
{
    thread_info info[MAX_NUM];
    pthread_t tids[MAX_NUM];
    for (int i = 0; i < MAX_NUM; i++)
    {
        info[i].id = i;
        info[i].name = "  PETER" + to_string(i);
        cout << "create thread " << i << endl;
        int ret = pthread_create(&tids[i], NULL, print_hello, (void *)&info[i]);
        if (ret){
            cout << "something wrong during create thread" << endl;
        }
    }
    //pthread_exit(NULL);
    return 0;
}

运行结果：

 

 可见子线程随着主线程的退出也销毁掉，没有打印输出

2.使用pthread_exit(NULL)

#include "windows.h"
#include <bits/stdc++.h>
using namespace std;

#define MAX_NUM 4

typedef struct thread_info
{
    int id;
    string name;
} thread_info;

//void*只是表示可以传入任意类型的指针,返回值也可以是任意类型的指针
void *print_hello(void *arg)
{
    Sleep(2000);
    thread_info *ifo = (thread_info *)arg;
    cout << "child thread" << endl;
    // int id = ifo->id;
    // string name = ifo->name;
    // cout << "ID: " << id << " NAME" << name << endl;
}
int main()
{
    thread_info info[MAX_NUM];
    pthread_t tids[MAX_NUM];
    for (int i = 0; i < MAX_NUM; i++)
    {
        info[i].id = i;
        info[i].name = "  PETER" + to_string(i);
        cout << "create thread " << i << endl;
        int ret = pthread_create(&tids[i], NULL, print_hello, (void *)&info[i]);
        if (ret){
            cout << "something wrong during create thread" << endl;
        }
    }
    pthread_exit(NULL);
    //return 0;
}

运行结果：

　　

 

由此可以知道pthread_exit退出主线程后其子线程依旧运行。

3.使用pthread_exit 是否会销毁进程资源

#include "windows.h"
#include <bits/stdc++.h>
using namespace std;
#define MAX_NUM 4

typedef struct thread_info
{
    int id;
    string name;
} thread_info;

void *print_hello(void *arg)    //void*只是表示可以传入任意类型的指针,返回值也可以是任意类型的指针
{
    Sleep(2000);
    thread_info *ifo = (thread_info *)arg;
    cout << "child thread" << endl;
     int id = ifo->id;
     string name = ifo->name;
     cout << "ID: " << id << " NAME" << name << endl;
}
int main()
{
    thread_info info[MAX_NUM];
    pthread_t tids[MAX_NUM];
    for (int i = 0; i < MAX_NUM; i++)
    {
        info[i].id = i;
        info[i].name = "  PETER" + to_string(i);
        cout << "create thread " << i << endl;
        int ret = pthread_create(&tids[i], NULL, print_hello, (void *)&info[i]);
        if (ret){
            cout << "something wrong during create thread" << endl;
        }
    }
    pthread_exit(NULL);
    //return 0;
}

 

如图可以看到主线程退出前，结构体数组info中存储着ID和name，

主线程通过pthread_exit(NULL) 退出后，主线程中的变量info将销毁不能访问。

 

 4.主线程退出前等待子线程

for (int i = 0; i < MAX_NUM; i++){
        int ret=pthread_join(tids[i], &status);
        //int ret=pthread_detach(tids[i]);
    }

 

 

以上为Windows11上的测试，如有问题欢迎批评指正。

 2022-03-24    16:39:02