FIX: Unable to Set Binary Compatibility with Class Module

 Last reviewed: December 18, 1997
Article ID: Q171520
The information in this article applies to:
  • Microsoft Visual Basic Control Creation, Learning, Professional, and Enterprise Editions for Windows, version 5.0

SYMPTOMS

After compiling a .dll for the first time and setting the project to binary compatibility, further attempts to compile may result in the following error message: 

   "<Function Name> in the <Class Name> class module has arguments
   and/or a return type that is incompatible with a similar declaration
   in the version-compatible component.

   If you choose Accept, the <Class Name> class module will no longer
   support client applications compiled against the version-compatible
   component. To avoid this incompatibility, edit the declaration to be
   compatible, or clear the version compatibility setting in Project
   Options."

CAUSE

This problem occurs in large, complex applications that contain circular references. For example, a function in one class module references another class module as follows: 

   Public Function DoSomething(param1, param2, param3) as MyOtherClass
where MyOtherClass is another class in the same project, and MyOtherClass contains a UDT which references back to the first module.

A simple repro case is not available as this behavior tends to occur only in large, complex projects.

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
For a list of the Visual Basic 5.0 bugs that were fixed in the Visual Studio 97 Service Pack 2, please see the following article in the Microsoft Knowledge Base: 

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

MORE INFORMATION

This problem occurs when a function in one class module references another class module, and the second class module's Instancing property is set to "2 - PublicNotCreatable." For example, the function in the first class module could be: 

   Public Function DoSomething(param1, param2, param3) as MyOtherClass
If MyOtherClass is another class module with Instancing set to "2," the problem occurs. 
Keywords          : vb5all VS97FixlistSP3 VS97FixlistSP2 VB5FixlistSP2
Version           : 5.0
Platform          : WINDOWS
Issue type        : kbbug
Solution Type     : kbfix kbservicepack

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Last reviewed: December 18, 1997
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