FIX: Assertion Occurs When Calling BeginTrans()

The information in this article applies to:

   The Microsoft Foundation Classes (MFC), included with:
    - Microsoft Visual C++ for Windows, version 1.5

SYMPTOMS

If CDatabase::BeginTrans() is called a second time for a CDatabase object and the debug version of the Microsoft Foundation Class (MFC) Library is used, the following assertion will occur:

   File dbcore.cpp, Line 549, Assertion Failed!

This problem occurs even though CDatabase::CommitTrans() was called after the first CDatabase::BeginTrans() call.

CAUSE

The CDatabase class uses a variable called "m_bTransactionPending" for debug mode, which gets set to TRUE in CDatabase::BeginTrans() with the following code:

   #ifdef _DEBUG
       m_bTransactionPending = TRUE;
   #endif // _DEBUG

   #ifdef DEBUG
       m_bTransactionPending = FALSE;
   #endif // DEBUG

RESOLUTION

Modify the code in CommitTrans() by changing the DEBUG constant to _DEBUG, and rebuild the MFC library by following the directions in the README.TXT located in the \MSVC\MFC\SRC directory.

As an alternative, you could copy the code from CommitTrans() into a new member function of a CDatabase-derived class, fix the code, and call the new function instead of CommitTrans(). However, if you're letting CRecordset create the database object (that is, not passing a pointer to a CDatabase object into the constructor), CDatabase will be used instead of your CDatabase-derived class.

STATUS

Microsoft has confirmed this to be a bug in the Microsoft Foundation Class Library version 2.5. This bug was corrected in Visual C++ for Windows, version 1.51 (MFC 2.51).