KB157876 - FIX: SetFieldNull() Asserts in DBCORE.CPP Line 4055 or 4062

SYMPTOMS

void CRecordset::SetNullParamStatus(DWORD nParam) { ASSERT(nParam < m_nParams); // <= Line 4055 m_pbParamFlags[nParam] |= AFX_SQL_FIELD_FLAG_NULL; } void CRecordset::ClearNullParamStatus(DWORD nParam) { ASSERT(nParam < m_nParams); // <= Line 4062 m_pbParamFlags[nParam] &= ~AFX_SQL_FIELD_FLAG_NULL; }

CAUSE

During Update(), both the RFX_Date() and RFX_Text() functions incorrectly add the date or unicode text field to the parameter map:

   case CFieldExchange::NameValue:
     ...
     // Fall through

   case CFieldExchange::Value:
     ...
     // Add the member address to the param map
     pFX->m_prs->m_mapParamIndex.SetAt(&value, (void*)nField);

A subsequent call to SetFieldNull() will try to determine whether the field is a parameter by checking the index returned by GetBoundParamIndex(). An index >= 0 implies that the field is a parameter:

   void CRecordset::SetFieldNull(void* pv, BOOL bNull)
   {
     ...
    int nIndex = GetBoundParamIndex(pv);
     if (nIndex >= 0)
     {
      if (bNull)
         SetNullParamStatus(nIndex);
       else
         ClearNullParamStatus(nIndex);
       return;
     }
     ... // Handle the case where the field is not a parameter
   }

Because the RFX function incorrectly added the field to the parameter map, an index >= 0 is returned by GetBoundParamIndex(). Because of this, SetFieldNull() incorrectly calls the function to set or clear the Null parameter status rather than the Null field status. If the index returned by GetBoundParamIndex() is less the member variable CRecordset::m_nParams, then the assert will occur:

   ASSERT(nParam < m_nParams);

MORE INFORMATION

Copy the implementation of RFX_Date() or RFX_Text() (MSDEV\MFC\SRX\DBRFX.CPP) into a new .cpp file, and rename the function to something such as RFX_Date2() or RFX_Text2(). Create a header file for the .cpp file and include that in your recordset .cpp file. Be sure to type:

   #include"stdafx.h"

at the top of your new .cpp file, and include the .cpp file in your project.

Change all RFX_Date() calls in your recordset's DoFieldExchange() to calls to RFX_Date2(), or change all RFX_Text() to RFX_Text2().

In your new RFX_Date2() or RFX_Text2() implementation, comment out the following line, which appears under the CFieldExchange::Value case:

   //      pFX->m_prs->m_mapParamIndex.SetAt(&value, (void*)nField);

FIX: SetFieldNull() Asserts in DBCORE.CPP Line 4055 or 4062

SYMPTOMS

CAUSE

RESOLUTION

STATUS

MORE INFORMATION