A failure may occur when you attempt to use object linking and embedding (OLE) within a Microsoft Foundation Classes (MFC) regular dynamic link library (DLL) (154320)
The information in this article applies to:
- The Microsoft Foundation Classes (MFC), when used with:
- Microsoft Visual C++, 32-bit Enterprise Edition 4.2
- Microsoft Visual C++, 32-bit Professional Edition 4.2
- Microsoft Visual C++, 32-bit Enterprise Edition 5.0
- Microsoft Visual C++, 32-bit Professional Edition 5.0
- Microsoft Visual C++, 32-bit Enterprise Edition 6.0
- Microsoft Visual C++, 32-bit Professional Edition 6.0
- Microsoft Visual C++, 32-bit Learning Edition 6.0
This article was previously published under Q154320 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. STATUSMicrosoft has confirmed that this is a bug in the Microsoft products that are listed in the "Applies to" section.
| Modification Type: | Major | Last Reviewed: | 9/2/2005 |
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| Keywords: | kbOLEApp kbtshoot kbBug kbDLL kbdocfix kbnofix KB154320 kbAudDeveloper |
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