Q202128: FIX: ATL EXE Server on CComAutoThreadModule Hang on Registration

Article: Q202128
Product(s): Microsoft C Compiler
Version(s): 3.0,6.0
Operating System(s): 
Keyword(s): kbActiveX kbCOMt kbLocalSvr kbThread kbVC600bug kbATL300bug kbGrpDSMFCATLkbbuglist
Last Modified: 10-FEB-2002

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The information in this article applies to:

- The Microsoft Active Template Library (ATL) 3.0, used with:
   - Microsoft Visual C++, 32-bit Enterprise Edition, version 6.0 
   - Microsoft Visual C++, 32-bit Professional Edition, version 6.0 
   - Microsoft Visual C++, 32-bit Learning Edition, version 6.0 
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SYMPTOMS
========

An ATL EXE server based on CComAutoThreadModule<> can hang when being
registered or unregistered.

CAUSE
=====

CComAutoThreadModule<>::Init() called in WinMain() creates a thread pool
(by default 4 threads). The destructor of global CComAutoThreadModule makes
certain these threads terminate before the process terminates. This happens by
posting a WM_QUIT message to each of the threads in the thread pool and calling
WaitForSingleObject() on the thread handle. The threads are scheduled such that
the threads in the pool may not have called GetMessage() and so the message
queue is not created. This causes the PostThreadMessage() to fail. Hence, the
threads in the pool do not terminate and WaitForSingleObject() waits infinitely
for the threads to terminate.

RESOLUTION
==========

In the Altcom.h file, inside the vc98\atl\include directory of destructor in the
CComAutoThreadModule function replace the following code:

     ::PostThreadMessage(m_pApartments[i].m_dwThreadID, WM_QUIT, 0, 0);

with this code:

     while (::PostThreadMessage(m_pApartments[i].m_dwThreadID, WM_QUIT,
        0, 0) == 0) ::Sleep(100);

STATUS
======

Microsoft has confirmed this to be a bug in the Microsoft products listed at the
beginning of this article.

This problem was corrected in Microsoft Visual C++ .NET.

MORE INFORMATION
================

1. Use Appwizard to create an ATL EXE.

2. Insert any type of ATL object in the project.

3. In Stdafx.h, replace CComModule with
  CComAutoThreadModule<CComSimpleThreadAllocator>.

4. Build the project.

  NOTE: There is a chance that the server may hang at this point since the
  custom build step registers the server.

5. In the Project Settings menu under the Debug tab type "/RegServer" in the
  Program Arguments dialog box.

6. Run the server in the debugger.

  NOTE: If it does not hang the first time, repeat this step. Since this is
  timing related, the problem may not reproduce on certain machines.

Additional query words: kbDSupport

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Keywords          : kbActiveX kbCOMt kbLocalSvr kbThread kbVC600bug kbATL300bug kbGrpDSMFCATL kbbuglist
Technology        : kbVCsearch kbAudDeveloper kbATLsearch
Version           : :3.0,6.0
Issue type        : kbbug
Solution Type     : kbfix

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