Q192853: FIX: Wincore.cpp Line 879 Assert When Using MFC Classes

Article: Q192853
Product(s): Microsoft C Compiler
Version(s): 6.0
Operating System(s): 
Keyword(s): kbDatabase kbMFC kbVC600bug kbNoUpdate
Last Modified: 11-FEB-2002

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

- The Microsoft Foundation Classes (MFC), used with:
   - Microsoft Visual C++, 32-bit Enterprise Edition, version 6.0 
-------------------------------------------------------------------------------

SYMPTOMS
========

When you use MFC, the following assert can occur:

  Program: e:\test\app.exe File: wincore.cpp Line: 879

The following example calls CDatabase::OpenEx() from inside an MFC regular DLL
and shows the resulting assert. The problem is not limited to the MFC Database
classes.

If you expose an OLE automation method in an MFC regular DLL and have code like:

     STDMETHODIMP CTest::TestMethod()
     {
        AFX_MANAGE_STATE(afxGetStaticModuleState())
        CDatabase db;
        db.OpenEx("DSN=LocalServer;Database=pubs;UID=sa;PWD=;");
        db.Close();

        return S_OK;
     }

the assertion dialog appears.

This doesn't happen in an application built with Visual C++, version 5.0. Also
this problem only occurs in debug builds. The release build runs correctly.

CAUSE
=====

Code has been added to the GetSafeOwner_() call that calls GetRoutingFrame_().
In the GetRoutingFrame_() function, you can see the following code:

     if (pFrame != NULL)
        ASSERT_VALID(pFrame);

This assertion is not correct. This assertion assumes that there is a handle map
and that the pFrame CWnd * is in either the temporary or permanent CWnd handle
map. Neither of these situations is true in the scenario described in the
Symptoms section.

RESOLUTION
==========

To get rid of the failed asserts, you can add the following code to debug
builds:

     class CTempRoutingFrame
     {
        CFrameWnd* m_pFrame ;
        public:
          CTempRoutingFrame(CFrameWnd * pWnd= NULL)
          {
            // Save current value.
            m_pFrame = AfxGetThreadState()->m_pRoutingFrame;
            // Set to value passed in. NULL by default.
            AfxGetThreadState()->m_pRoutingFrame = pWnd;
          }
          ~CTempRoutingFrame()
          {
            // Restore m_pRoutingFrame to original value.
            AfxGetThreadState()->m_pRoutingFrame = m_pFrame;
          }
     };

     STDMETHODIMP CsrvTest2::Test()
     {
        AFX_MANAGE_STATE(AfxGetStaticModuleState())

        #ifdef _DEBUG
          CTempRoutingFrame tmp;
        #endif

        CDatabase db;
        db.OpenEx("DSN=LocalServer;Database=pubs;UID=sa;PWD=;");
        db.Close();

        return S_OK;
     }

If you need to add this code in many places, you may want to write a macro such
as the following:

     #ifdef _DEBUG
        #define ASSERT_FIX() CTempRoutingFrame tmp;
     #else
        #define ASSERT_FIX()
     #endif

So you can do the following:

     STDMETHODIMP CsrvTest2::Test()
     {
        AFX_MANAGE_STATE(AfxGetStaticModuleState())
        ASSERT_FIX()
        ...
     }


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.

Additional query words:

======================================================================
Keywords          : kbDatabase kbMFC kbVC600bug kbNoUpdate 
Technology        : kbAudDeveloper kbMFC
Version           : :6.0
Issue type        : kbbug
Solution Type     : kbfix

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

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