Q114536: PRB: C2129 Generated With Forward Reference Used in Prototype

Article: Q114536
Product(s): Microsoft C Compiler
Version(s): 1.0,1.5,2.0,4.0,7.0
Operating System(s): 
Keyword(s): kbCompiler
Last Modified: 11-FEB-2002

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The information in this article applies to:

- The C/C++ Compiler (CL.EXE), included with:
   - Microsoft C/C++ for MS-DOS, version 7.0 
   - Microsoft Visual C++, versions 1.0, 1.5 
   - *EDITOR Please do not choose this product*Microsoft Visual C++ 32-bit Edition* use 241, 265, 225, versions 1.0, 2.0, 4.0 
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SYMPTOMS
========

Compiling a C++ source file which uses a forward reference to a struct in a
function prototype will cause the compiler to generate the following error:

  error C2129: static function 'Function' declared but not defined

The sample code shown below can be used to illustrate this problem. Note: the
error does not occur if the same file is compiled as a C source file.

CAUSE
=====

This is by design. In C++, a tag not previously seen is entered in the current
scope. In the sample code, the ForwardRef appearing in the parameter list is a
different struct than the one defined afterwards.

RESOLUTION
==========

To resolve this problem, move the declaration of the struct so that it is
located before the function prototype.

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

     /* Compile options needed: /Tp to force this to be compiled as a C++
     *                          source file.
     */ 

     static void Function( int i, struct ForwardRef * frPtr );

     // To work around this problem place the following declaration before
     // the Function prototype.

     struct ForwardRef
     {
         int data;
     };

     void main( void )
     {
         struct ForwardRef *frPtr;
         int j;
         Function( j, frPtr );
     }

     static void Function( int i, struct ForwardRef *frPtr ){}


Additional query words: 8.00 8.00c 9.00

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Keywords          : kbCompiler 
Technology        : kbVCsearch kbAudDeveloper kbCVCComp
Version           : :1.0,1.5,2.0,4.0,7.0
Issue type        : kbprb

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