FIX: Marshaling ADO Recordset Out-of-Process Causes Small Memory Leak

When an ADO recordset is marshaled out-of-process from a COM server, a small leak in Private Bytes occurs in the COM server's process space.

This leak occurs when using either a disconnected ADO recordset or a recordset created with the RDS DataFactory if you are using versions of MDAC earlier than 2.1 sp2.

The leak is caused by ADO internally making an incorrect call to AddRef() on a Stream pointer within MarshalInterface.

This problem has been fixed in Microsoft Data Access Components 2.1 and later. You may download the latest version of Microsoft Data Access Components from the following site:

Steps to Reproduce Behavior

1. Create an Executable project in Visual Basic that will be the server application. Name the project LeakEXE, and within it, create a class module named LeakRS. Set a reference to the Microsoft ActiveX Data Objects Library. Use the following code within the LeakRS class:

   Option Explicit
   
   Function GetRS() As ADODB.Recordset
   Dim rs As ADODB.Recordset
       
       On Error Resume Next
       Set rs = New ADODB.Recordset
       rs.Fields.Append "x", adInteger
       rs.Open
       rs.AddNew
       rs.Fields(0).Value = 1
       rs.Update
       rs.MoveFirst
       Set GetRS = rs
       
   End Function
   					

2. Next, create a client project in Visual Basic, using the following code. Then, set a reference to the ActiveX EXE and to Microsoft ActiveX Data Objects Library.

   
   Sub OutofProcLeak()
   Dim x As New LeakEXE.LeakRS
   Dim rs As ADODB.Recordset
   
   For i = 0 To 200000
       Set rs = x.GetRS
       Debug.Print Str(i)
       DoEvents
   Next
   
   Set rs = Nothing
   					

3. Run the client application. Use the Windows NT Performance Monitor to watch Private Bytes counter for object Process using instance LeakEXE.exe.