Q240866: BUG: C2989 and C2988 on Class Template Partial Specializations

Article: Q240866
Product(s): Microsoft C Compiler
Version(s): winnt:5.0,6.0
Operating System(s): 
Keyword(s): kbtemplate kbCompiler kbCPPonly kbVC500 kbVC500bug kbVC600 kbVC600bug
Last Modified: 03-MAY-2001

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The information in this article applies to:

- The C/C++ Compiler (CL.EXE), included with:
   - Microsoft Visual C++, 32-bit Enterprise Edition, version 5.0 
   - Microsoft Visual C++, 32-bit Professional Edition, version 5.0 
   - Microsoft Visual C++, 32-bit Enterprise Edition, version 6.0 
   - Microsoft Visual C++, 32-bit Professional Edition, version 6.0 
   - Microsoft Visual C++, 32-bit Learning Edition, version 6.0 
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SYMPTOMS
========

You may get the following error message if you try to use class template partial
specializations:

  error C2989: 'A<T,2>' : template class has already been defined as a
  non-template class error C2988: unrecognizable template
  declaration/definition

Please refer to the sample in the More Information section for details.

CAUSE
=====

The compiler does not support class template partial specializations as
specified in the C++ Standard (14.5.4.1) quoted here:

  1- A primary class template declaration is one in which the class template
  name is an identifier. A template declaration in which the class template
  name is a template-id, is a partial specialization of the class template
  named in the template-id. A partial specialization of a class template
  provides an alternative definition of the template that is used instead of
  the primary definition when the arguments in a specialization match those
  given in the partial specialization (temp.class.spec.match). The primary
  template shall be declared before any specializations of that template. If a
  template is partially specialized then that partial specialization shall be
  declared before the first use of that partial specialization that would cause
  an implicit instantiation to take place, in every translation unit in which
  such a use occurs; no diagnostic is required.

Please refer to the C++ Standard section 14.5.4 for more information on this.

STATUS
======

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

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

Steps to Reproduce Behavior
---------------------------

The following code sample demonstrates the error.

  //test.cpp
  // compiler option needed: none

  //  primary template
  template<class T, int I> struct A {
  	void f();
  };

  template<class T, int I> void A<T,I>::f() { }

  //  class template partial specialization
  template<class T> struct A<T,2> {
  	void f();
  	void g();
  	void h();
  };

Additional query words:

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Keywords          : kbtemplate kbCompiler kbCPPonly kbVC500 kbVC500bug kbVC600 kbVC600bug 
Technology        : kbVCsearch kbAudDeveloper kbCVCComp
Version           : winnt:5.0,6.0
Issue type        : kbbug

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