[求助]pthread_exit和pthread_join的用法

xd1198 · 发表于 2004-11-29 09:26:44

我在编一个小程序，想用pthread_exit结束一个线程，返回一个值，并用pthread_join接收这个值，打印出来。是不是pthrad_exit(*)只能返回一个整数值？帮助里也没有说啊。源程序如下：

/*example.c*/
#include <stdio.h>
#include <pthread.h>
void thread1(char s[])
{
/*b1[]="This is the thread1 return value!";返回值，原来放在这里，后来想到，还是应该放到主函数里。*/
printf("This is a pthread1.\n");
printf("%s\n",s);
pthread_exit(b1); //结束线程，返回一个值。
}
void thread2(char s[])
{
/*b2[]="This is the thread2 return value!";同上*/
printf("This is a pthread2.\n");
printf("%s\n",s);
pthread_exit(b2);
}
/**************main function ****************/
int main(void)
{
pthread_t id1,id2;
int i,ret1,ret2;
char b1[]="This is the thread1 return value!";//线程1结束时的返回值
char b2[]="This is the thread2 return value!";//线程2结束时的返回值
char a1[50],s1[]="This is first thread!";
char a2[50],s2[]="This is second thread!";
for(i=0;i<50;i++)
{
a1[i]='\0';
a2[i]='\0';
}
ret1=pthread_create(&id1,NULL,(void *) thread1,s1);
ret2=pthread_create(&id2,NULL,(void *) thread2,s2);
if(ret1!=0){
printf ("Create pthread1 error!\n");
exit (1);
}
pthread_join(id1,a1);
printf("%s\n",a1);
if(ret2!=0){
printf ("Create pthread2 error!\n");
exit (1);
}
printf("This is the main process.\n");
pthread_join(id2,a2);
printf("%s\n",a2);
return (0);
}

复制代码

运行如下：
  [*****@***** c]$ gcc -g -lpthread -o example example.c
example.c: In function `thread1':
example.c:13: `b1' undeclared (first use in this function)
example.c:13: (Each undeclared identifier is reported only once
example.c:13: for each function it appears in.)
example.c: In function `thread2':
example.c:21: `b2' undeclared (first use in this function)
example.c: In function `main':
example.c:50: warning: passing arg 2 of `pthread_join' from incompatible pointer
type
example.c:62: warning: passing arg 2 of `pthread_join' from incompatible pointer
type
我不明白的地方：b1[],b2[] 都是主函数里定义的的，；两个线程函数里不能用吗？而且b1[],b2[]放到各个线程函数里，后面两个警告也是会出现的，打印也不对。请教各位大虾了。

xd1198 · 发表于 2004-11-29 10:10:07

修改如下后运行正确：

/* example.c*/
#include <stdio.h>
#include <pthread.h>
void thread1(char s[])
{
printf("This is a pthread1.\n");
printf("%s\n",s);
pthread_exit("Hello first!"); //结束线程，返回一个值。
}
void thread2(char s[])
{
printf("This is a pthread2.\n");
printf("%s\n",s);
pthread_exit("Hello second!");
}
/**************main function ****************/
int main(void)
{
pthread_t id1,id2;
void *a1,*a2;
int i,ret1,ret2;
char s1[]="This is first thread!";
char s2[]="This is second thread!";
ret1=pthread_create(&id1,NULL,(void *) thread1,s1);
ret2=pthread_create(&id2,NULL,(void *) thread2,s2);
if(ret1!=0){
printf ("Create pthread1 error!\n");
exit (1);
}
pthread_join(id1,&a1);
printf("%s\n",(char*)a1);
if(ret2!=0){
printf ("Create pthread2 error!\n");
exit (1);
}
printf("This is the main process.\n");
pthread_join(id2,&a2);
printf("%s\n",(char*)a2);
return (0);
}

复制代码

运行结果：
[****@XD**** c]$ ./example
This is a pthread1.
This is first thread!
Hello first!
This is the main process.
This is a pthread2.
This is second thread!
Hello second!
看来，是我在线程函数里的变量设得有问题。

x11 · 发表于 2004-11-29 20:19:33

啊，不是编译吗，为什么说运行如下

xd1198 · 发表于 2004-11-30 14:21:25

最初由 x11 发表
啊，不是编译吗，为什么说运行如下

不好意思，说错了。

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