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Microsoft KB Archive/172985

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Knowledge Base

Article ID: 172985

Article Last Modified on 7/5/2005


  • Microsoft Visual C++ 5.0 Enterprise Edition
  • Microsoft Visual C++ 5.0 Professional Edition

This article was previously published under Q172985


When using the #import directive, errors may be generated due to the order in which definitions appear in the idl file used to generate the type library. The sample below causes error C2504, base class undefined, due to the interfaces being defined globally instead of in the library block.


Move the interface definitions into the library block.

- or -

Create an extraneous reference to the class that the compiler is generating an error from within the library block.


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



   // t.cpp
      // Compile options: /c
      #import "t.tlb"

   // t.idl
      // command line: midl t.idl

      // move the definitions of A and B into the
      // library block for one workaround
      [ uuid( 10000000-0000-0000-0000-000000000000 ) ]
      interface A : IUnknown
      [ uuid( 20000000-0000-0000-0000-000000000000 ) ]
      interface B : A
      [ uuid( 30000000-0000-0000-0000-000000000000 ) ]
      library Test

         // uncomment this coclass for another workaround
         // [ hidden, uuid( 40000000-0000-0000-0000-000000000000 ) ]
         //coclass Dummy
         //   interface A;

         [ uuid( 50000000-0000-0000-0000-000000000000 ) ]
         coclass C
            interface B;

Additional query words: midl

Keywords: kbbug kbfix kbvs97sp2fix kbcpponly kbcompiler KB172985