再谈线程等待函数WaitForSingleObject和CloseHandle

多线程中使用WaitForSingleObject结束线程，啥也不说，先上代码

#include <windows.h>#include <String.h>#include <stdio.h>int Fun1Proc( void ){int i;char *c = "thread one " ; for(i = 0; i < 100; i++){printf("%s number: %d \n",c ,i+1 );}return 0;}int main(  ){HANDLE hThread1;hThread1 = CreateThread(NULL, 0, Fun1Proc, NULL, 0, NULL);int i;char *c = "main thread " ; for(i = 0; i < 100; i++){printf("%s number: %d \n",c ,i+1 );}CloseHandle(hThread1);return 0;}

执行结果：

main thread 1
main thread 2
main thread 3
...

main thread 98
main thread 99
main thread 100

为什么线程函数没有执行呢？奇怪，多运行几遍，发现每次结果不一定相同，下面是另一次执行结果：

main thread 1
main thread 2
main thread 3

...

main thread 71

thread one 1
thread one 2

main thread 72

main thread 73

...

thread one 3
thread one 4

main thread 75

main thread 76

...

main thread 98
main thread 99
main thread 100

可见，主函数运行完了，整个程序就退出了，不会等到Fun1Proc（）运行完再退出。等2秒会不会好一点呢？下面是修改后的main程序

int main(  ){HANDLE hThread1;hThread1 = CreateThread(NULL, 0, Fun1Proc, NULL, 0, NULL);Sleep(2000);int i;char *c = "main thread " ; for(i = 0; i < 100; i++){printf("%s number: %d \n",c ,i+1 );}return 0;}

运行结果：
thread one 1
thread one 2
thread one 3

...

thread one 98
thread one 99
thread one 100

main thread 1
main thread 2
main thread 3
...

main thread 98
main thread 99
main thread 100

这下貌似可以，但这个2秒只是估算的一个时间，并不准确，有的线程执行时间很长的，代码还要再修改下：

int main(  ){HANDLE hThread1;hThread1 = CreateThread(NULL, 0, Fun1Proc, NULL, 0, NULL);WaitForSingleObject(hThread1, INFINITE);int i;char *c = "main thread " ; for(i = 0; i < 100; i++){printf("%s number: %d \n",c ,i+1 );}CloseHandle(hThread1);return 0;}

这下好了，每次运行结果都正确，WaitForSingleObject的作用就是等待线程自动结束，继续执行后面的程序。这个CloseHandle为什么这么靠后呢？把它放前面一点好不好？不是说每次创建线程以后直接CloseHandle更好吗？好，那就挪到上面试试

int main(  ){HANDLE hThread1;hThread1 = CreateThread(NULL, 0, Fun1Proc, NULL, 0, NULL);CloseHandle(hThread1);WaitForSingleObject(hThread1, INFINITE);int i;char *c = "main thread " ; for(i = 0; i < 100; i++){printf("%s number: %d \n",c ,i+1 );}return 0;}

运行后发现，又和一开始一样了，main thread 中穿插着 thread one。 原来是CloseHandle之后，WaitForSingleObject得不到thread的句柄，没法再等到这个thread结束，呵呵