push 和 pop 函数的使用

#include <stdio.h>
#include <unistd.h>
#include <pthread.h>
void *clean(void *arg)
{
printf("cleanup: %s \n",(char *)arg);
return (void *)0;
}
void * thr_fn1(void * arg)
{
printf("chread 1 start \n");
pthread_cleanup_push((void *)clean,"thraed 1 first handler");
pthread_cleanup_push((void *)clean,"thread 1 second handler");
printf("thread 1 push complete \n");
if(arg)
{
return ((void *)1);
}
pthread_cleanup_pop(0);
pthread_cleanup_pop(0);
return (void *)1;
}
//输出结果： chread 1 start ->thread 1 push complte 
//push和pop框起来的代码，不管正常退出还是异常退出，都将执行清除函数，但是存在特例：不包括return 退出
void * thr_fn2(void * arg)
{
printf("chread 2 start \n");
pthread_cleanup_push((void *)clean,"thraed 2 first handler");//push函数的作用：把清除函数压入栈。
pthread_cleanup_push((void *)clean,"thread 2 second handler");
printf("thread 2 push complete \n");
if(arg)
{
pthread_exit((void *)2);//只有退出时，才会执行清除函数cleanup。(栈先进后出)
}
pthread_cleanup_pop(0);
pthread_cleanup_pop(0);
pthread_exit((void*)2);
}
//结果：chread 2 start ->thread 2 push complete -> thread 2 second handler -> thread 1 first handler.
int main(int argc, char *argv[])
{
int err;
pthread_t tid1,tid2;//创建两个线程
void *tret;

err=pthread_create(&tid1,NULL,thr_fn1,(void *)1);
if(err!=0)
{
printf("error \n");
return -1;
}

err=pthread_create(&tid2,NULL,thr_fn2,(void *)1);
if(err!=0)
{
printf("error\n");
return -1;
}
err=pthread_join(tid1,&tret);
if(err!=0)
{
printf("error\n");
return -1;
}
printf("thread 1 exit code %d \n",(int)tret);
return 0;
}