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Q153897: FIX: MFC DAO or ODBC App Crashes on Exit

Article: Q153897
Product(s): Microsoft C Compiler
Version(s): WINDOWS:2.5; winnt:4.0,4.1,4.2
Operating System(s): 
Keyword(s): kbinterop kbProgramming kbDAOsearch kbDatabase kbMDAC kbMFC kbVC kbVC500fix kbDSupport
Last Modified: 07-MAY-2001

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The information in this article applies to:

- Microsoft Visual C++, versions 4.0, 4.1 
- Microsoft Visual C++, 32-bit Enterprise Edition, version 4.2 
- Microsoft Visual C++, 32-bit Professional Edition, version 4.2 
- Microsoft Data Access Components version 2.5 
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SYMPTOMS
========

An application intermittently crashes on exit and an error similar to the
following appears:

  <application> caused an invalid page fault in
  module KERNEL32.DLL at 0137:bff9a07c.

This behavior occurs when the application is using the MFC DAO classes, the MFC
ODBC classes, or the ODBC API to access a database using the Jet Database
Engine.

RESOLUTION
==========

Call the LoadLibrary() function on the Jet Engine as shown in the sample code
below. This call needs to be done only once during execution of the program. To
minimize any adverse affect on performance, call LoadLibrary() only after the
database has been opened. Do not call FreeLibrary() for this DLL. The DLL will
be automatically unloaded when the application exits.

This bug has been fixed in Jet 3.5 that is included with Visual C++ 5.0. If you
are using the ODBC, you can simply use the newer ODBC driver that is available
with Visual C++ 5.0. If you are using DAO, you need to build your application
using Visual C++ 5.0 to use DAO 3.5. The earlier MFC classes use DAO/Jet 3.0 and
do not recognize DAO 3.5.

STATUS
======

This bug has been fixed in Jet 3.5 that is included with Visual C++ 5.0.

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

This problem occurs only if a dialog resource is loaded. This includes
applications that use CFormView-derived classes, such as CRecordView and
CDaoRecordView, as well as dialog-based applications.

The following sample code shows the workaround for a default MFC AppWizard
application using the MFC DAO classes. The call to LoadLibrary() is added to the
Open() function of the CDaoRecordset-derived class named CMySet. Similar logic
can be used for the MFC ODBC classes.

To fix the DAOEnrol sample, add the LoadLibrary() call in the sample code below
to the CDaoEnrolDoc::OnNewDocument() function, before the call to the base class
CDocument::OnNewDocument() function.

To fix the Enroll tutorial, add the LoadLibrary() call in the sample code below
to the CEnrollDoc::GetDatabase() function, after the call to m_database.Open().

Sample Code
-----------

     void CMySet::Open(int nOpenType, LPCTSTR lpszSql, int nOptions)
     {
         CDaoRecordset::Open(nOpenType, lpszSql, nOptions);

         // Load the Jet Engine to ensure that it remains in memory
         // during the shutdown process.
         LoadLibrary( "MSJT3032.DLL" );
     }

Additional query words:

======================================================================
Keywords          : kbinterop kbProgramming kbDAOsearch kbDatabase kbMDAC kbMFC kbVC kbVC500fix kbDSupport kbMDAC250 kbGrpDSODBC kbfixlist
Technology        : kbVCsearch kbVC400 kbAudDeveloper kbMDACSearch kbVC410 kbMDAC250 kbVC420 kbVC32bitSearch
Version           : WINDOWS:2.5; winnt:4.0,4.1,4.2
Issue type        : kbbug kbprb
Solution Type     : kbfix

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