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

/*线程清理函数*/
void *clean(void *arg)
{
printf("cleanup :%s\n",(char *)arg);
return (void *)0;
}

/*线程1的执行函数*/
void *thr_fn1(void *arg)
{
printf("thread 1 start \n");

/*将线程清理函数压入清除栈两次*/
pthread_cleanup_push( (void*)clean,"thread 1 first handler");
pthread_cleanup_push( (void*)clean,"thread 1 second hadler");
printf("thread 1 push complete \n");

if(arg)
{
return((void *)1); //线程运行到这里会结束，后面的代码不会被运行。由于是用return退出，所以不会执行线程清理函数。
}

pthread_cleanup_pop(0);
pthread_cleanup_pop(0);
return (void *)1;
}

/*线程2的执行函数*/
void *thr_fn2(void *arg)
{
printf("thread 2 start \n");

/*将线程清理函数压入清除栈两次*/
pthread_cleanup_push( (void*)clean,"thread 2 first handler");
pthread_cleanup_push( (void*)clean,"thread 2 second handler");
printf("thread 2 push complete \n");

if(arg)
{
pthread_exit((void *)2);//线程运行到这里会结束，后面的代码不会被运行。由于是用pthread_exit退出，所以会执行线程清理函数。执行的顺序是先压进栈的后执行，即后进先出。
}

pthread_cleanup_pop(0);
pthread_cleanup_pop(0);
pthread_exit((void *)2);
}

int main(void)
{
int err;
pthread_t tid1,tid2;
void *tret;

/*创建线程1并执行线程执行函数*/
err=pthread_create(&tid1,NULL,thr_fn1,(void *)1);
if(err!=0)
{
printf("error .... \n");
return -1;
}

/*创建线程2并执行线程执行函数*/
err=pthread_create(&tid2,NULL,thr_fn2,(void *)1);
if(err!=0)
{
printf("error .... \n");
return -1;
}

/*阻塞等待线程1退出，并获取线程1的返回值*/
err=pthread_join(tid1,&tret);
if(err!=0)
{
printf("error .... \n");
return -1;
}
printf("thread 1 exit code %d \n",(int)tret);

/*阻塞等待线程2退出，并获取线程2的返回值*/
err=pthread_join(tid2,&tret);
if(err!=0)
{
printf("error .... ");
return -1;
}
printf("thread 2 exit code %d \n",(int)tret);

return 1;
}

上边是程序，运行结果是：
thread 2 start
thread 2 push complete
cleanup :thread 2 second handler
cleanup :thread 2 first handler
thread 1 start
thread 1 push complete
thread 1 exit code 1
thread 2 exit code 2

可是我认为结果应该是：
thread 1 start
thread 1 push complete
thread 1 exit code 1
thread 2 start
thread 2 push complete
cleanup:thread 2 second handler
cleanup:thread 2 first handler
thread 2 exit code 2