Q154320: BUG: AfxOleInit Returns TRUE Without Initializing OLE in a DLL

Article: Q154320
Product(s): Microsoft C Compiler
Version(s): winnt:4.2,5.0,6.0
Operating System(s): 
Keyword(s): kbole kbdocfix kbCOMt kbDLL kbMFC kbVC420bug kbDSupport kbGrpDSMFCATL
Last Modified: 03-MAY-2001

-------------------------------------------------------------------------------
The information in this article applies to:

- The Microsoft Foundation Classes (MFC), used with:
   - Microsoft Visual C++, 32-bit Enterprise Edition, version 4.2 
   - Microsoft Visual C++, 32-bit Professional Edition, version 4.2 
   - Microsoft Visual C++, 32-bit Enterprise Edition, version 5.0 
   - Microsoft Visual C++, 32-bit Professional Edition, version 5.0 
   - 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 
-------------------------------------------------------------------------------

SYMPTOMS
========

When you develop a Microsoft Foundation Classes (MFC) regular dynamic link
library (DLL), you may want to use object linking and embedding (OLE) without
exposing an OLE object, such as displaying a dialog box from within the DLL that
contains an OLE control. A failure may occur when you call the DoModal function
in the dialog box creation if you used the AfxOleInit or
AfxEnableControlContainer function to initialize OLE within the DLL. Typically,
this is done by calling the functions in the InitInstance method of the CWinApp
derived class.

CAUSE
=====

In a MFC regular DLL, AfxOleInit does not initialize OLE because MFC cannot
uninitialize OLE in the DLL_PROCESS_DETACH method of the ExitInstance function.
In this case, OLE may already have been unloaded. The decision to not initialize
OLE is by design. The bug is that AfxOleInit returns TRUE after setting
m_bNeedTerm to -1. According to the Visual C++ documentation, when AfxOleInit
returns TRUE this means that OLE was initialized, and that is not the case in a
DLL.

RESOLUTION
==========

In order to uninitialize OLE when it is initialized in the DLL, this requires
exported methods for initialization and uninitialization that the client has to
call because the uninitialization has to occur before the CWinApp::ExitInstance
function, which is a part of DLL_PROCESS_DETACH.

A better solution is to initialize and uninitialize OLE in the client
application. This can be done in MFC by calling AfxOleInit in the application's
InitInstance method of the CWinApp derived class. MFC then uninitializes OLE by
exiting the application.

STATUS
======

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

Additional query words: 0x800401f0 CreateDlgControls Dialog creation

======================================================================
Keywords          : kbole kbdocfix kbCOMt kbDLL kbMFC kbVC420bug kbDSupport kbGrpDSMFCATL 
Technology        : kbAudDeveloper kbMFC
Version           : winnt:4.2,5.0,6.0
Issue type        : kbbug
Solution Type     : kbnofix

=============================================================================

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.

Copyright Microsoft Corporation 1986-2002.