学步园

        线程可以安排它退出时需要调用的函数，这与进程可以用atexit函数安排进程退出时需要调用的函数是类似的。这样的函数称为线程清理处理程序（thread cleanup handler）。线程可以建立多个清理处理程序。处理程序记录在栈中，也就是说他们的执行顺序与它们注册时的顺序相反。

         void  pthread_cleanup_push(void  (*rtn)(void *arg),  void *arg);

         void  pthread_cleanup_pop(int execute);

        当线程执行以下动作时调用清理函数，调用参数为arg，清理函数rtn的调用顺序是由pthread_cleanup_push函数来安排的。

        (1)  the  call  to  pthread_exit

        (2)  responds  to  cancellation request

        (3)  make  a  call  to pthread_cleanup_pop  with a  nonzero execute argument

        如果execute参数置为0，清理函数将不被调用。无论哪种情况，pthread_cleanup_pop都将删除上次pthread_cleanup_push调用建立的清理处理程序。

 #include <stdio.h><br /> #include <stdlib.h><br /> #include <pthread.h><br /> // thread cleanup handler<br /> void cleanup(void *arg)<br /> {<br /> printf("cleanup: %s/n", (char*)arg);<br /> }<br /> void *thr_fn1(void *arg)<br /> {<br /> printf("thread 1 start/n");<br /> pthread_cleanup_push(cleanup, "thread 1 first handler");<br /> pthread_cleanup_push(cleanup, "thread 1 second handler");<br /> printf("thread 1 push complete/n");<br /> /* if (arg != NULL)<br /> {<br /> return ((void*)1);<br /> } */<br /> pthread_cleanup_pop(0);<br /> pthread_cleanup_pop(1);<br /> return ((void*)1);<br /> }</p> <p>void *thr_fn2(void *arg)<br /> {<br /> printf("thread 2 start/n");<br /> pthread_cleanup_push(cleanup, "thread 2 first handler");<br /> pthread_cleanup_push(cleanup, "thread 2 second handler");<br /> printf("thread 2 push complete/n");<br /> if (arg != NULL)<br /> {<br /> pthread_exit((void*)2);<br /> }<br /> pthread_cleanup_pop(0);<br /> pthread_cleanup_pop(0);<br /> pthread_exit((void*)2);<br /> }<br /> int main()<br /> {<br /> void *tret;<br /> pthread_t tid1, tid2;<br /> pthread_create(&tid1, NULL, thr_fn1, (void*)1);<br /> pthread_create(&tid2, NULL, thr_fn2, (void*)1);<br /> pthread_join(tid1, &tret);<br /> printf("thread 1 exit code %d/n", (int)tret);<br /> pthread_join(tid2, &tret);<br /> printf("thread 2 exit code %d/n", (int)tret);<br /> exit(0);<br /> }