Q171064: FIX: C2512 Instantiating Template in Member Initializer

Article: Q171064
Product(s): Microsoft C Compiler
Version(s): winnt:5.0sp1,5.0sp3
Operating System(s): 
Keyword(s): kbVC600fix kbVS97sp3bug
Last Modified: 04-MAY-2001

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The information in this article applies to:

- The C/C++ Compiler (CL.EXE), used with:
   - Microsoft Visual C++, 32-bit Enterprise Edition, version 5.0sp1 
   - Microsoft Visual C++, 32-bit Professional Edition, version 5.0sp1 
   - Microsoft Visual C++, 32-bit Enterprise Edition, version 5.0sp3 
   - Microsoft Visual C++, 32-bit Professional Edition, version 5.0sp3 
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SYMPTOMS
========

When a member initializer instantiates a template class that takes a const
parameter in its constructor, you may receive the following error:

  error C2512: no appropriate default constructor available

RESOLUTION
==========

Declare a global object of the template class specialization that is used in the
member initializer. When optimizations are used, this unreferenced global should
be optimized away.

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 Visual C++ version 6.0
for Windows.

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

This is a regression from Visual C++ 5.0.

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

      // Compile options needed: none

      struct _Tree {
        _Tree(const int& _Parg) {}
      };

      template<class _Pr>
      struct set {
        _Tree _Tr;
        set(const _Pr& _Pred = _Pr()) : _Tr(_Pred) {}
      };

      struct Boo
      {
        Boo();
        set<int>& _xSet;
      };

      //set<int> x;  // uncomment for workaround

      Boo::Boo()
       : _xSet(*new set<int>)  //C2512 here
      {}

Additional query words: visual studio service pack

======================================================================
Keywords          : kbVC600fix kbVS97sp3bug 
Technology        : kbVCsearch kbAudDeveloper kbCVCComp
Version           : winnt:5.0sp1,5.0sp3
Issue type        : kbbug
Solution Type     : kbfix

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