Q184089: FIX: C2555 with Virtual Function Returning Template Object

Article: Q184089
Product(s): Microsoft C Compiler
Version(s): 4.0,4.0a,4.1,4.2,5.0,6.0
Operating System(s): 
Keyword(s): kbCompiler kbCPPonly kbLangCPP kbVC kbVC400bug kbVC410bug kbVC420bug kbVC500bug kbVC600
Last Modified: 11-FEB-2002

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The information in this article applies to:

- Microsoft Visual C++, versions 4.0, 4.0a, 4.1 
- Microsoft Visual C++, 32-bit Enterprise Edition, versions 4.2, 5.0, 6.0 
- Microsoft Visual C++, 32-bit Professional Edition, versions 4.2, 5.0, 6.0 
- Microsoft Visual C++, 32-bit Learning Edition, version 6.0 
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SYMPTOMS
========

A virtual function returning a templated class object and a derived class
defining the virtual function, causes the following compiler error:

  error C2555: 'MyDerived::TestFunc' : overriding virtual function differs from
  'MyBase::TestFunc' only by return type or calling convention

RESOLUTION
==========

Define the base class function to be nonvirtual.

STATUS
======

Microsoft has confirmed this to be a bug in the Microsoft products listed at the
beginning of this article.

This problem was corrected in Microsoft Visual C++ .NET.

MORE INFORMATION
================

Sample Code
-----------

  template <class T>
     class TestClass
     {
        public:
           T val;
           TestClass(T num){val=num;}

     };

     class MyBase
     {
       public:
         int value;
         virtual TestClass<float> TestFunc(void) ;
         /* Make this function nonvirtual to fix C2555 error. */ 
         /* A pure virtual function also has the same problem. */ 
     };
     template <class T>
     class MyDerived : public MyBase
     {
       public:
         virtual TestClass<float> TestFunc(void)
         {
           return TestClass<float>(3.14f);
         }
     };
     MyDerived<int> x;
     void main(void)
     {
       x.TestFunc();
     }

REFERENCES
==========

(c) Microsoft Corporation 1998, All Rights Reserved. Contributions by Mark
Hagen, Microsoft Corporation.


Additional query words: CL C2555 CPP CXX

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Keywords          : kbCompiler kbCPPonly kbLangCPP kbVC kbVC400bug kbVC410bug kbVC420bug kbVC500bug kbVC600bug kbNoUpdate 
Technology        : kbVCsearch kbVC400 kbAudDeveloper kbVC410 kbVC420 kbVC500 kbVC600 kbVC32bitSearch kbVC400a kbVC500Search
Version           : :4.0,4.0a,4.1,4.2,5.0,6.0
Issue type        : kbbug
Solution Type     : kbfix

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