Q131376: FIX: C2974 Error When Calling Templated Base Class Functions

Article: Q131376
Product(s): Microsoft C Compiler
Version(s): 2.0,2.1
Operating System(s): 
Keyword(s): kbCompiler kbCPPonly kbVCkbbuglist kbfixlist
Last Modified: 29-JUL-2001

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The information in this article applies to:

- Microsoft C/C++ Compiler (CL.EXE), used with:
   - *EDITOR Please do not choose this product*Microsoft Visual C++ 32-bit Edition* use 241, 265, 225, versions 2.0, 2.1 
-------------------------------------------------------------------------------

SYMPTOMS
========

Calling a member function of a templated base class through the 'this' pointer
produces the following erroneous error:

  error C2974: '<base templated class name>' : invalid template actual
  argument '#1', type expected.

RESOLUTION
==========

Call the function without using the 'this' pointer.

STATUS
======

Microsoft has confirmed this to be a bug in the Microsoft products listed at the
beginning of this article. This problem was fixed in Microsoft Visual C++,
32-bit Edition, version 4.0.

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

The Visual C++ compiler generates the following errors when the following sample
program (TEST.CPP), is compiled with the /D"SHOW_TEMPLATE_ERROR" option:

  test.cpp(20) : error C2974: 'A' : invalid template actual argument '#1',
                 type expected
  test.cpp(20) : error C2231: '.B<int,int>::A<int>::Afunc' : left operand
                 points to 'class', use '->'
  test.cpp(20) : fatal error C1903: unable to recover from previous
                 error(s); stop ping compilation

Sample Code to Demonstrate Problem
----------------------------------

  /* Compile options needed: none
  */ 
  // #define SHOW_TEMPLATE_ERROR

  template <class Type>
  class A
  {
  public:
      Type a;
      void Afunc(void){};
  };

  template <class Type1, class Type2>
  class B: public A<Type1>
  {
  public:
      void Bfunc()
      {
  #ifdef SHOW_TEMPLATE_ERROR
          this->A<Type1>::Afunc();
  #else
          A<Type1>::Afunc();
  #endif
      }
  };

  void main()
  {
      B<int, int> b;
  }

Additional query words: 2.00 2.10

======================================================================
Keywords          : kbCompiler kbCPPonly kbVC kbbuglist kbfixlist
Technology        : kbVCsearch kbAudDeveloper kbCVCComp
Version           : :2.0,2.1
Issue type        : kbbug
Solution Type     : kbfix

=============================================================================

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