Question

I cannot understand why next code doesn’t work. It compile correct, but doesn’t output anything. Can you help me?

HANDLE hEvent;
unsigned int WINAPI MyThread(void *p)
{
    WaitForSingleObject(hEvent, INFINITE);
    _tprintf(TEXT("%s\n"),p);
    return 0;
}

int _tmain(int argc, TCHAR *argv[])
{
    hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
    unsigned int ThreadID;
    HANDLE hThread1 = (HANDLE)_beginthreadex(NULL, 0, MyThread, L"hello world", 0, &ThreadID);
    SetEvent(hEvent);
    return 0;
}

Answer 1

My guess is that the application is exiting before the print statement even fires. You set the event and then instantly exit. Try waiting for the thread to complete before exiting. You should be able to use the handle that is returned from _beginthreadex.

HANDLE hThread1 = (HANDLE)_beginthreadex(NULL, 0, MyThread, L"hello world", 0, &ThreadID);
SetEvent(hEvent);
WaitForSingleObject( hThread1, INFINITE );

Note: I just used INFINITE as the timeout for an example, in general you probably don’t want INFINITE which could lead to deadlocks, etc. Each case needs to be examined to determine the correct behavior. Here, since you are just writing to the console, if this hasn’t returned in a few seconds there is probably something wrong. You could modify the code to check the return value of WaitForSingleObject to see if it exited due to timeout and then make a decision based on that (like log an error, or something that would help to diagnose what went wrong)