Q128789: BUG: LNK2001 on Member Function When Use Nested Class Template

Article: Q128789
Product(s): Microsoft C Compiler
Version(s): winnt:2.0,2.1,4.0,4.1,4.2,5.0,6.0
Operating System(s): 
Keyword(s): kbCompiler kbCPPonly kbVC kbVC500bug
Last Modified: 06-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 Editions, versions 2.0, 2.1, 4.0, 4.1 
   - Microsoft Visual C++, 32-bit Enterprise Edition, version 4.2 
   - Microsoft Visual C++, 32-bit Professional Edition, version 4.2 
   - 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
========

When you build a program that uses nested class templates, the following link
error is generated:

  test.obj: error LNK2001: unresolved external symbol
  "?Funtion@BB@?$AA@HH@@QAEHXZ
  ( public: int __thiscall AA<int,int>::BB::Funtion(void) )"

CAUSE
=====

The compiler does not generate code for the member function in the nested class
template.

RESOLUTION
==========

To work around the problem, use one of the following suggestions:

- Define the function in the class declaration as an inline function. Be sure
  to define the function body in the class declaration. Defining the function
  as an inline function outside the class declaration will not eliminate the
  problem.

  -or-

- Use the member function specialization technique to work around the problem.
  This technique is demonstrated in the "Sample Code" section of this article.

STATUS
======

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

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

The following code can be used to reproduce or work around the problem.

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

     /* Compile options needed: None.
     */ 

     #include <stdio.h>

     template <class T1, class T2>
     class AA
     {
       public:
         class BB
         {
           public:
             int Function();

     // Work around #1, replace the previous line with
     //        int Function() { return 0; }
         };
     };

     // Work around #2, uncomment the following function
     // AA<int,int>::BB::Function()
     // {
     //   return 0;
     // }

     template <class T1, class T2>
     int AA<T1,T2>::BB::Function()
     {
        return 0;
     }

     void main()
     {
       AA<int,int>::BB b;
       printf( "%d\n", b.Function() );
     }

Additional query words: 9.0 9.00 9.1 9.10 10.00 10.10 10.20

======================================================================
Keywords          : kbCompiler kbCPPonly kbVC kbVC500bug 
Technology        : kbVCsearch kbAudDeveloper kbCVCComp
Version           : winnt:2.0,2.1,4.0,4.1,4.2,5.0,6.0
Issue type        : kbbug
Solution Type     : kbpending

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