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FIX: Assertion Or Failure With CDaoDatabase::CreateRelation Method

This article was previously published under Q217216
This article has been archived. It is offered "as is" and will no longer be updated.
A GPF or assertion occurs when using CDaoDatabase::CreateRelation method against Access 2000 database with Visual C++ version 6.0.
Microsoft confirms that this behavior is due to a bug in the CDaoDatabase::CreateRelation() method in DAO 3.6. The implementation of this method can be found in Daocore.cpp.

In the CDaoDatabase::CreateRelation() method, a DAOFields pointer and a DAOField pointer is declared. In addition, the DAOFields collection is looped through, and the DAOField pointer is used to access a field in the DAOFields collection, and then release is called.At the end of the method, the following check is implemented:
if (pDAOField != NULL)	    pDAOField->Release();

Since pDAOField was used as a temporary it is not set to NULL. As a result, the Release() call draws an assertion in the DAO360.DLL implementation of Release() stating that Release() was called too many times. Consequently, Release() cannot set the pointer (pDAOField) that referenced it to NULL.
Microsoft has confirmed that this is a bug in the Microsoft products that are listed at the beginning of this article.

This bug was corrected in Visual Studio 6.0 Service Pack 3. For more information about Visual Studio service packs, please see the following articles in the Microsoft Knowledge Base:

194022 INFO: Visual Studio 6.0 Service Packs, What, Where, Why

194295 HOWTO: Tell That Visual Studio 6.0 Service Packs Are Installed

Visual Studio 6.0 Service Pack 3 included the DAO 3.60 bits as part of the MDAC 2.1 SP1 stack, which fixes this error.
To compile with the MFC run time version of 0x0601 and load DAO 3.60, reference the following article in the Microsoft Knowledge Base:
236991 PRB: Unrecognized Database Format Error with Access 2000 Database

Article ID: 217216 - Last Review: 10/14/2013 19:34:16 - Revision: 1.0

Microsoft Visual C++ 6.0 Enterprise Edition

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