pthread_cleanup_push的作用和atexit()的作用是一样的。
在线程执行下列操作时，注册的函数将会执行。
-
Makes a call to pthread_exit
-
Responds to a cancellation request
-
Makes a call to pthread_cleanup_pop
with a nonzero
execute
argument
值得注意的是，线程执行return时，是不会调用注册的函数的。
下面就是一个简单的例子。
#include <pthread.h>
#include <syslog.h>
#include <fcntl.h>
#include <sys/resource.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <signal.h>
#include <stdlib.h>
#include <stdio.h>
#include <termios.h>
#include <unistd.h>
void
cleanup(void *arg)
{
printf("cleanup: %s/n", (char *)arg);
}
void *
thr_fn1(void *arg)
{
printf("thread 1 start/n");
pthread_cleanup_push(cleanup, "thread 1 first handler");
pthread_cleanup_push(cleanup, "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);
}
void *
thr_fn2(void *arg)
{
printf("thread 2 start/n");
pthread_cleanup_push(cleanup, "thread 2 first handler");
pthread_cleanup_push(cleanup, "thread 2 second handler");
printf("thread 2 push complete/n");
if (arg)
pthread_exit((void *)2);
pthread_cleanup_pop(0);
pthread_cleanup_pop(0);
pthread_exit((void *)2);
}
int
main(void)
{
int err;
pthread_t tid1, tid2;
void *tret;
err = pthread_create(&tid1, NULL, thr_fn1, (void *)1);
if (err != 0)
printf("can't create thread 1: %s/n", strerror(err));
err = pthread_create(&tid2, NULL, thr_fn2, (void *)1);
if (err != 0)
printf("can't create thread 2: %s/n", strerror(err));
err = pthread_join(tid1, &tret);
if (err != 0)
printf("can't join with thread 1: %s/n", strerror(err));
printf("thread 1 exit code %d/n", (int)tret);
err = pthread_join(tid2, &tret);
if (err != 0)
printf("can't join with thread 2: %s/n", strerror(err));
printf("thread 2 exit code %d/n", (int)tret);
exit(0);
}
运行的结果如下：
$./thread
thread 1 start
thread 1 push complete
thread 2 start
thread 2 push complete
cleanup: thread 2 second handler
cleanup: thread 2 first handler
thread 1 exit code 1
thread 2 exit code 2
这说明了thread 1调用return返回没有触发注册的cleanup函数。