KB171520 - FIX: Unable to Set Binary Compatibility with Class Module

Article ID: 171520

Article Last Modified on 12/10/2003

Microsoft Visual Basic 5.0 Control Creation Edition
Microsoft Visual Basic 5.0 Learning Edition
Microsoft Visual Basic 5.0 Professional Edition
Microsoft Visual Basic 5.0 Enterprise Edition

This article was previously published under Q171520

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:

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 2, please see the following article in the Microsoft Knowledge Base:

171554 : 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: kbbug kbfix kbvbp500sp2fix kbvs97sp2fix KB171520