Question

c++多线程中主线程运行机制

#include <Windows.h>
#include <iostream>
using namespace std;
DWORD WINAPI Fun1Proc(LPVOID IpParameter);
DWORD WINAPI Fun2Proc(LPVOID IpParameter);
HANDLE hMutex;
void main()
{
HANDLE hThread1;
HANDLE hThread2;
hMutex = CreateMutex(NULL, FALSE, NULL);
hThread1 = CreateThread(NULL,0,Fun1Proc,NULL,0,NULL);
hThread2 = CreateThread(NULL,0,Fun2Proc,NULL,0,NULL);
CloseHandle(hThread1);
CloseHandle(hThread2);
cout<<"main:running"<<endl;
Sleep(4000);
}
DWORD WINAPI Fun1Proc(LPVOID IpParameter)
{
WaitForSingleObject(hMutex,INFINITE);
cout<<"fun1:a"<<endl;
ReleaseMutex(hMutex);
return 0;
}
DWORD WINAPI Fun2Proc(LPVOID IpParameter)
{
WaitForSingleObject(hMutex,INFINITE);
cout<<"fun2:b"<<endl;
ReleaseMutex(hMutex);
return 0;
}
为何主线程有时会输出两次？主线程的运行机制是怎样的?

Answer 1

不是运行机制引起的，而是cout输出的缓存机制引起主线程输出两次。

所以你把主线程的cout<<也用WaitForSingleObject(hMutex,INFINITE);和ReleaseMutex(hMutex);抱起来应该就不会输出两次了。