FIX: Crash When Assigning Uninitialized Object to Tag

• Microsoft Visual Basic, Learning, Professional, and Enterprise Editions for Windows, version 5.0

SYMPTOMS

Attempting to set the Tag property of one of the Windows Common Controls (COMCTL32.OCX) at run-time may result in the following error and cause the application to terminate:

   “VB5 caused an invalid page fault in module COMCTL32.OCX
   at 0137:202cb2a8.”

CAUSE

This problem occurs when the object variable that you are trying to assign to the Tag property is uninitialized or is null.

RESOLUTION

In Visual Basic 5.0, you can work around the problem by checking the value of the variable before assigning it to the Tag property:

   Dim x As Object
   '...
   If x Is Nothing Then
      '
   Else
      StatusBar1.Panels(1).Tag = x
   End If

STATUS

Microsoft has confirmed this to be a bug in the Microsoft products listed at the beginning of this article. This bug has been fixed in Visual Studio 97 Service Pack 2.

For more information on the Visual Studio 97 Service Pack 2, please see the following article in the Microsoft Knowledge Base:

   ARTICLE-ID: Q170365
   TITLE     : INFO: Visual Studio 97 Service Packs - What, Where, and Why

   ARTICLE-ID: Q171554
   TITLE     : INFO: Visual Basic 5.0 Fixes in Visual Studio 97
               Service Pack 2

MORE INFORMATION

With Visual Studio 97 Service Pack 2 installed, the above scenario correctly yields with the following trappable run-time error.

   Run-time error '91':
   Object variable or With block not set.