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Microsoft KB Archive/171549

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Knowledge Base

Article ID: 171549

Article Last Modified on 2/24/2005


  • Microsoft Visual Basic 5.0 Professional Edition
  • Microsoft Visual Basic 5.0 Enterprise Edition

This article was previously published under Q171549


Cached Class Factorys can get released by illegal thread.


The repository maintains a cache of class factorys. If a class factory has not been accessed for a short period of time, the reference to the class factory will get released. However, the reference is released from a different thread than the one that initially obtained the reference.


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 3.

For more information, please see the following article in the Microsoft Knowledge Base:

170365 INFO: Visual Studio 97 Service Packs - What, Where, and Why

For a list of the Visual Basic 5.0 bugs that were fixed in the Visual Studio 97 Service Pack 3, please see the following article in the Microsoft Knowledge Base:

175450 INFO: Visual Basic 5.0 Fixes in Visual Studio 97 Service Pack 3


The behavior above violates the apartment-threading model, and can cause a crash.

This behavior is evident when a repository object is implemented in Visual Basic. This only occurs in Visual Basic where a class is defined as the class that is the implementation of the generic repository class. This behavior occurs when the ClassID for the Visual Basic class matches the repository classdef's ClassID. It crashes when the client creates an instance before the cache is released. When the engine releases the class factory cache, the crash occurs.

Keywords: kbbug kbfix kbvs97sp2fix kbvbp500sp3fix KB171549