Q190067: BUG: Object References Might Not Be Released Properly

Article: Q190067
Product(s): Microsoft Visual Basic for Windows
Version(s): WINDOWS:6.0;
Operating System(s): 
Keyword(s): kbnokeyword kbOSWinNT kbVBp600bug kbOSWin kbGrpDSVB
Last Modified: 11-JAN-2001

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The information in this article applies to:

- Microsoft Visual Basic Learning Edition for Windows, version 6.0 
- Microsoft Visual Basic Professional Edition for Windows, version 6.0 
- Microsoft Visual Basic Enterprise Edition for Windows, version 6.0 
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SYMPTOMS
========

If a function call to an object returns a Variant and the Variant is not
assigned to a local variable, Visual Basic might not dereference the object
correctly. As a result, a new thread is created in the object's process space
each time the function is called.

RESOLUTION
==========

Assign the function's return value to a local variable, regardless of whether or
not it is needed.

Example
-------

The class clsMyObject has a function called MyVariantFunction that returns a
Variant:

     Public Function MyVariantFunction() As Variant

If the return result of the function is not needed, calling the function without
assigning the return value might cause new threads to be created:

     Public Sub TestFunction()
        clsMyObject.MyVariantFunction
     End Sub

To avoid the unnecessary creation of threads, assign the function's return value
to a local variable, regardless of whether or not it is needed:

     Public Sub TestFunction()
        Dim vReturnValue As Variant

        ' Although this will not be used, it guarantees proper dereferencing.
        vReturnValue = clsMyObject.MyVariantFunction
     End Sub

STATUS
======

Microsoft has confirmed this to be a bug in the Microsoft products listed at the
beginning of this article. We are researching this bug and will post new
information here in the Microsoft Knowledge Base as it becomes available.

MORE INFORMATION
================

This type of behavior usually occurs when returning variant arrays that contain
user-defined types.

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Keywords          : kbnokeyword kbOSWinNT kbVBp600bug kbOSWin kbGrpDSVB 
Technology        : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB600Search kbVBA600 kbVB600
Version           : WINDOWS:6.0;
Issue type        : kbbug
Solution Type     : kbpending

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