Q172980: FIX: Compiler Incorrectly Causes Default Constructor Reference

Article: Q172980
Product(s): Microsoft C Compiler
Version(s): WINNT:5.0
Operating System(s): 
Keyword(s): kbCompiler kbCPPonly kbVC500bug kbVS97sp2fix
Last Modified: 17-JUL-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 
-------------------------------------------------------------------------------

SYMPTOMS
========

When instantiating a class template with a member function that has a default
parameter, error C2512 may be generated.

CAUSE
=====

This behavior can occur when the default parameter is an explicitly-created
temporary of the parameterized type of the template. The sample code below
demonstrates this.

RESOLUTION
==========

Do not use an explicitly-generated temporary as a default argument.

-or-

Ensure that the template argument has a default constructor available.

STATUS
======

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:

  Q170365 INFO: Visual Studio 97 Service Packs - What, Where, and Why

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

Sample
------

     // compile options : /c
     template<typename T>
     class C
     {
     public:
         void fn(const T & t = T());
     };
     class X
     {
     public:
         X(int);
         ~X();
     };
     C<X> l;

Additional query words:

======================================================================
Keywords          : kbCompiler kbCPPonly kbVC500bug kbVS97sp2fix 
Technology        : kbVCsearch kbAudDeveloper kbCVCComp
Version           : WINNT:5.0
Issue type        : kbbug
Solution Type     : kbfix

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

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