Q315922: MSScript.ocx Leaks Event Handles in Certain Applications

Article: Q315922
Product(s): Microsoft Visual Basic for Windows
Version(s): 5.0,6.0
Operating System(s): 
Keyword(s): 
Last Modified: 10-JUN-2002

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The information in this article applies to:

- Microsoft Visual Basic Enterprise Edition for Windows, versions 5.0, 6.0 
- Microsoft Visual Basic Professional Edition for Windows, versions 5.0, 6.0 
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SYMPTOMS
========

When you use the Microsoft Script control (MSScript.ocx) in an environment that
repeatedly creates and destroys threads, MSScript.ocx leaks event handles. For
each thread that is created and destroyed, an event handle is leaked if one or
more objects of the Script control are created on that thread.

WORKAROUND
==========

Do not repeatedly create and destroy threads; use a thread pool instead.

STATUS
======

Microsoft has confirmed this to be a bug in the Microsoft products listed at the
beginning of this article. Microsoft is researching this problem and will post
more information here in the Microsoft Knowledge Base when it becomes
available.


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

Steps to Reproduce Behavior
---------------------------

1. In Visual Basic, create an ActiveX EXE project named Repro. A default class
  named Class1 is created by default.

2. Add a form to the project. Keep the default name Form1.

3. Add Microsoft Script Control 1.0 to the toolbox, and then add an instance of
  the control to Form1.

4. Add the following code to Class1:

  Dim f As New Form1
  Private Sub Class_Initialize()
      f.Visible = True
  End Sub
  Private Sub Class_Terminate()
      Unload f
  End Sub

5. Change the threading model of the project to "Thread per Object", and then
  build the project.

6. In Visual Basic, create a Standard EXE project. Keep the default name
  Project1. Form1 is created by default.

7. Add a command button to Form1, and then add the following code to Form1:

  Dim server As Object
  Private Sub Command1_Click()
      Dim o As Object
      Set o = CreateObject("repro.class1")
      Set o = Nothing
  End Sub

  Private Sub Form_Load()
      Set server = CreateObject("repro.class1")
  End Sub

  Private Sub Form_QueryUnload(Cancel As Integer, UnloadMode As Integer)
      Set server = Nothing
  End Sub

8. Build and run Project1. Notice that two processes, Project1.exe and
  Repro.exe, are started.

9. Use Performance Monitor or Task Manager to monitor the handle count for
  Repro.exe.

10. Repeatedly click the command button on Form1 of Project1, and then observe
  the handle count for the Repro.exe process. Notice that each time you click
  the button, an instance of the control is created and destroyed, and the
  handle count for Repro.exe increases by 1.

Additional query words: msscript

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Keywords          :  
Technology        : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB500Search kbVB600Search kbVB500 kbVB600
Version           : :5.0,6.0
Issue type        : kbbug
Solution Type     : kbpending

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