BUG: C2555 with Virtual Function Returning Template Object

• Microsoft Visual C++, 32-bit Editions, versions 4.0, 4.0a, 4.1, 4.2, 5.0, 6.0

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.

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

Keywords : kbCompiler kbCPPonly kbLangCPP kbVC kbVC400bug kbVC410bug kbVC420bug kbVC500bug kbVC600bug
Version : winnt:4.0,4.0a,4.1,4.2,5.0,6.0
Platform : winnt
Issue type : kbbug