Why does GetExitCodeThread() return FALSE here? - c++

Question

I have a small test code. My assumption is in below code, since I didn't set flag to stop the thread, then in the line of GetExitCodeThread(). it should return TRUE and return code is STILL_ACTIVE.
While in actual test, the result is:
Every time, the return value of GetExitCodeThread() is FALSE, so in main(), the while loop never entered. Could somebody please tell me the reason? What's wrong in my code. Thanks.
// ConsoleApplication1.cpp : Defines the entry point for the console application.
//
#include "stdafx.h"
#include "afxwin.h"
bool bExit = false;
HANDLE hOriginalThread;
static UINT ThreadFunc(LPVOID pParam)
{
int iCount = 0;
printf("start thread--ThreadFunc\n");
printf("Thread loop start: --ThreadFunc");
while (!bExit)
{
iCount++;
if (iCount % 50 == 0)
printf(".");
}
printf("Thread loop end: %d--ThreadFunc\n", iCount++);
printf("end thread--ThreadFunc\n");
return 0;
}
int _tmain(int argc, _TCHAR* argv[])
{
hOriginalThread = AfxBeginThread(ThreadFunc, (LPVOID)0, THREAD_PRIORITY_NORMAL, 0, 0);
Sleep(500);
DWORD dwEC;
int iTry = 0;
BOOL bStatus;
bStatus = GetExitCodeThread(hOriginalThread, &dwEC);
if (!bStatus)
{
printf("error GetExitCodeThread: %d--Main\n", GetLastError());
}
while (bStatus && dwEC == STILL_ACTIVE)
{
printf("Check Thread in active: %d--Main\n", iTry);
Sleep(1);
iTry++;
if (iTry>5)
{
printf("Try to terminate Thread loop: %d--Main\n", iTry++);
TerminateThread(hOriginalThread, 0);// Force thread exit
}
bStatus = GetExitCodeThread(hOriginalThread, &dwEC);
}
hThread = NULL;
printf("End Main --Main\n");
return 0;
}

Answer 1

AfxBeginThread() returns a CWinThread* object pointer, not a Win32 HANDLE like CreateThread() does. So GetExitCodeThread() fails due to an invalid thread handle, which GetLastError() should have told you.
CWinThread has an operator HANDLE() to get the proper Win32 handle of the thread, eg:
CWinThread *pThread = AfxBeginThread(...);
if (!pThread) ... // error handling
hOriginalThread = *pThread;
The reason your code even compiles is because you are likely not compiling with STRICT Type Checking enabled, so HANDLE is just a simple void*, which any kind of pointer can be assigned to. If you enable STRICT, HANDLE will not be void* and assigning the return value of AfxBeginThread() directly to hOriginalThread will cause a compiler error due to a type incompatibility.