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pthread_exit()用于线程退出,可以指定返回值,以便其他线程通过pthread_join()函数获取该线程的返回值
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return,是函数返回,不一定是线程函数,在主线程里return之后,主线程会结束并强制其子线程一起结束。
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exit()是进程退出,如果在线程函数中调用exit,那改线程的进程也就挂了,会导致该线程所在进程的其他线程也挂掉,比较严重
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用于等待其他线程结束:当调用 pthread_join() 时,当前线程会处于阻塞状态,直到被调用的线程结束后,当前线程才会重新开始执行。
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对线程的资源进行回收:如果一个线程是非分离的(默认情况下创建的线程都是非分离)并且没有对该线程使用 pthread_join() 的话,该线程结束后并不会释放其内存空间,这会导致该线程变成了“僵尸线程”。
#include <iostream>
#include <cstdlib>
#include <pthread.h>
#include <unistd.h>
using namespace std;
#define NUM_THREADS 5
void *wait(void *t)
{
int i;
long tid;
tid = (long)t;
sleep(1);
cout << "Sleeping in thread " << endl;
cout << "Thread with id : " << tid << " ...exiting " << endl;
pthread_exit(NULL);
}
int main ()
{
int rc;
int i;
pthread_t threads[NUM_THREADS];
pthread_attr_t attr;
void *status;
// 初始化并设置线程为可连接的(joinable)
pthread_attr_init(&attr);
pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_JOINABLE);
for( i=0; i < NUM_THREADS; i++ ){
cout << "main() : creating thread, " << i << endl;
rc = pthread_create(&threads[i], NULL, wait, (void *)&i );
if (rc){
cout << "Error:unable to create thread," << rc << endl;
exit(-1);
}
}
// 删除属性,并等待其他线程
pthread_attr_destroy(&attr);
for( i=0; i < NUM_THREADS; i++ ){
rc = pthread_join(threads[i], &status);
if (rc){
cout << "Error:unable to join," << rc << endl;
exit(-1);
}
cout << "Main: completed thread id :" << i ;
cout << " exiting with status :" << status << endl;
}
cout << "Main: program exiting." << endl;
pthread_exit(NULL);
}