FIX: Storing an ADO Recordset in GIT Might Cause An Access Violation

• Do not use a client-side cursor.
  
  -or-
  
  
• Store the recordset into GIT before you open the recordset.

1. Persist the recordset object into a file or IPersistStream memory object. To persist an ADO recordset into a file, use the Recordset.Save() method. To persist an ADO recordset to IPersistStream, see the following article in the Microsoft Knowledge Base:
   242249  (http://support.microsoft.com/kb/242249/EN-US/ ) Saving an ADO Recordset to an IStream
2. Instantiate a new ADO Recordset object.
3. Store the new recordset in GIT by using the RegisterInterfaceInGlobal() method.
4. Load the new recordset object from the persisted data in step 1.

Back to the top

Steps to Reproduce Behavior

1. Create a new project in Microsoft Visual C++ and add the following code to the project:
   
   

   #import "C:\Program Files\Common Files\System\ado\msado15.dll" no_namespace
   //you may need to add proper code to make this complete
   //Open a Connection
   hr = pConn->Open("DSN=Datasource1", "UserID1", "PWD1", -1);
   if (SUCCEEDED(hr)) 
   {
   	//Use client side cursor
   	pConn->PutCursorLocation(adUseClient);
   
   	// Now Open an ADO Recordset
   	pRecordSet = pConn->Execute("jobs", &recs, -1);
   
   	// Store the recordset in GIT 
   	hr =  gGlobalIntTable->RegisterInterfaceInGlobal(pRecordSet, IID_IDispatch, &cookie);
   
   	// Now revoke from GIT (to see the crash!)
   	if (hr == S_OK)
   		hr = gGlobalIntTable->RevokeInterfaceFromGlobal(cookie); //Crash!!!
   
   	// Close the ADO Recordset 
   	pRecordSet->Close();
   }

2. If you run the above code, you get a fatal error in the RevokeInterfaceFromGlobal() call. The following code fixes that problem:
   

   	// Open a Connection
   	hr = pConn->Open("DSN=Datasource1", "UserID1", "PWD1", -1);
   	if (SUCCEEDED(hr)) 
   	{
   		// Now Open an ADO Recordset
   		pConn->PutCursorLocation(adUseClient);
   		pRecordSet = pConn->Execute("jobs", &recs, -1);
   
   		//Save this Recordset in a file
   		remove("c:\\mytemp.tmp");<BR/>
   
   		hr= pRecordSet->Save("c:\\mytemp.tmp",adPersistADTG);
                     //Close the ADO Recordset we don't use this anymore
   		pRecordSet->Close();
   		
   		//Now Create a new recordset
   		_RecordsetPtr pRECORDSET2(__uuidof(Recordset));
   
   		// Store the SECOND recordset in GIT 
   		hr =  gGlobalIntTable->RegisterInterfaceInGlobal(pRECORDSET2, IID_IDispatch, &cookie);
   
   		// Load the SECOND recordset from the persisted 
   		hr =  pRECORDSET2->Open("c:\\mytemp.tmp", vtMissing, adOpenStatic, adLockUnspecified, -1);
   
   		// Now revoke from GIT
   		if (hr == S_OK)
   			hr = gGlobalIntTable->RevokeInterfaceFromGlobal(cookie); 
   
   	}
   

   
   Note that the second recordset that was created without using client-side cursor works fine.

Back to the top

• CLSID_StdGlobalInterfaceTable
• Global Interface Table
• Unhandled Exception
• R6025
• Pure Virtual Function Call

Back to the top