MFC CRecordset heap corruption detected at Close() - visual-c++

Question

I recently upgraded my operating system from Windows XP to Windows 7 SP1 64 bit. We are using Visual Studio 2008 Professional Edition and Oracle Database 11g Enterprise Edition Release 11.2.0.2.0 - 64bit Production.
When I try to execute this code I am getting the below exceptions
try
{
CDatabase *pDatabase = CDatabaseConnection::getDatabaseConnectionProcessLog();
ORSProcessLog rsProcessLog(pDatabase);
CString strFilter = _T("SELECT PROCESS_ID, MESSAGE FROM OP_PROCESS_LOG");
rsProcessLog.SetRowsetSize(1);
if( !rsProcessLog.Open(CRecordset::dynaset, strFilter, CRecordset::appendOnly) )
return;
if( !rsProcessLog.CanAppend() )
return;
rsProcessLog.AddNew();
rsProcessLog.m_PROCESS_ID = gcsProcessID;
rsProcessLog.m_MESSAGE = csMessageA;
rsProcessLog.Update();
rsProcessLog.Close();
}
catch ( CDBException* pEx )
{
bException = true;
pEx->GetErrorMessage(szCause, 255);
}
catch( CException* pEx )
{
bException = true;
pEx->GetErrorMessage(szCause, 255);
}
where rsProcessLog is the CRecordset object using a successfully connected database pointer pDatabase
In 32- bit Debug version I get a message box at rsProcessLog.Close(); with the below text
Debug Error
Program: ......\Test.exe
HEAP CORRUPTION DETECTED: after Normal block (#506) at 0x0087F628. CRT detected that the application wrote to memory after end of heap buffer.
Memory allocated at f:\dd\vctools\vc7libs\ship\atlmfc\src\mfc\dbcore.cpp(2626)
(Please Retry to debug the application)
In 32- bit Release version I get a message box at rsProcessLog.Close(); with the below text
Windows has triggered a breakpoint in Test.exe
This may be due to a corruption of the heap, which indicates a bug in Test.exe or any of the DLLS it has loaded.
This may also be due to the user pressing F12 while Test.exe has focus.
The output window may have more diagnostic information.
The above code was a working code in Windows XP with the rest of the env remaining the same and it continues to run in Windows XP but not in Windows 7. Any help will be greatly appreciated.

Answer 1

After some analysis of MFC CRecordest class I noticed that the problem appears after call to ::SqlSetPos where m_rgRowStatus array allocated on the heap become damaged (one byte more is written on the heap).
First and clean approach to problem is to force CRecordset class to use update/delete SQL statements instead of ::SqlSetPos function. To achive this you need to open your database using OpenEx method with CDatabase::userCursorLib option.
CDatabase db;
db.OpenEx(ConnectionString, CDatabase:useCursorLib);
This will change some CRecordset functionalities. See more at: http://msdn.microsoft.com/en-us/library/c689y99f.aspx
Second approach (dirty) is to reallocate m_rgRowStatus field, to use more memory on the heap, so call to ::SqlSetPos will not write to unallocated memory.
One way to do that is to override CRecordset::PreBindFields function:
void CMyDerivedRecordset::PreBindFields()
{
if ( ! (m_dwOptions & useMultiRowFetch) )
{
delete [] m_rgRowStatus;
m_rgRowStatus = new WORD[2];
}
CRecordset::PreBindFields();
}
You can do that in all of your CRecordset derived classes, or you can make one new CRecordset derived class which will become base class for all of your existing CRecordsetderived classes.