reason of assertion failure: CWinThread::Pumpmessage() called when not permitted.

[deepak k jain]

hi all,
i just now posted a msg asking the reason of following assertion in
mfc debug:
CWinThread::Pumpmessage() called when not permitted.

i couldn't find any satisfactory answer in already posted threads.
meanwhile i figured it out myself, and am posting it, may be it could
help somebody...

i went through mfc source code. it showed that when ::GetMessage()
function call in CWinThread::PumpMessage() fails, then it increments
some variable which, in the next call to PumpMessage(), which itself
is repeteadly called from CWinThread::Run(). here is the very code of
CWinThread::PumpMessage() which causes this assertion error:

if (!::GetMessage(&m_msgCur, NULL, NULL, NULL))
{
#ifdef _DEBUG
if (afxTraceFlags & traceAppMsg)
TRACE0("CWinThread::PumpMessage - Received WM_QUIT.\n");
m_nDisablePumpCount++; // application must die
// Note: prevents calling message loop things in 'ExitInstance'
// will never be decremented
#endif
return FALSE;
}

on checking documentation for ::GetMessage(), it shows that it returns
NULL when there is WM_QUIT message in the message queue.
now, line that was causing error in my case: (your case may be
different, but somehow you too are causing the application to quit,
while still working on it, like i was still trying to show a dialog
box.)

(this is part of my CAsyncSocket-derived class code)
CMySocket::OnConnect( int nErrorCode)
{
...
case WSAECONNREFUSED:
AfxMessageBox("Please check whether the server is
running.\n",MB_ICONSTOP);
AfxPostQuitMessage(0); //this caused the assertion error
break;
...
}

bye,
deepak

[Joseph M. Newcomer]

Sounds right to me. Once WM_QUIT is received, the message pump is supposed to be dead, so
calling it again is clearly an error. You are probably using a UI thread to handle a
socket connection; note that WinSock might be trying still to handle messages. What is the
traceback when this occurs?
joe

Joseph M. Newcomer [MVP]
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