DOCUMENT:Q140229  30-JUL-2001  [visualc]
TITLE   :PRB: C2027 When Using MFC Templated Collection Classes
PRODUCT :Microsoft C Compiler
PROD/VER:4.00
OPER/SYS:
KEYWORDS:kberrmsg kbprb

======================================================================
-------------------------------------------------------------------------------
The information in this article applies to:

 - The Microsoft Foundation Classes (MFC), included with:
    - Microsoft Visual C++, 32-bit Editions, version 4.0 
-------------------------------------------------------------------------------

SYMPTOMS
========

When you use MFC templated collection classes such as CArray, CList, and CMap to
store elements of type HTREEITEM or HIMAGELIST, the compiler generates the
following compiler error:

   afxtempl.h(73) : error C2027: use of undefined type '_TREEITEM'

   - or -

   afxtempl.h(73) : error C2027: use of undefined type '_TREEITEM'

CAUSE
=====

HTREEITEM is type-defined (typedef) as struct _TREEITEM, and HIMAGELIST is
type-defined (typedef) as struct _IMAGELIST in header file Commctrl.h located in
the \Msdev\Include directory. Structures _TREEITEM and IMAGELIST are not defined
in any header files or source files.

However, the template collection class helper function DestructElements in Visual
C++ version 4.0 calls the destructor of the stored elements. In this case, the
destructor of structure _TREEITEM or _IMAGELIST. Hence, the compiler error.

RESOLUTION
==========

Define a dummy structure for _TREEITEM or _IMAGELIST in global scope. For
example, the following code should compile cleanly:

   // Other includes.

   #include <afxtempl.h>

   struct _TREEITEM {};
   struct _IMAGELIST {};

   void TestFunction()
   {
     // will now not generate the compiler error
     CArray< HTREEITEM, HTREEITEM >  MyArray1;
     CArray< HIMAGELIST, HIMAGELIST > MyArray2;
   }

STATUS
======

This behavior is by design.

Additional query words: 4.00

======================================================================
Keywords          : kberrmsg kbprb 
Technology        : kbAudDeveloper kbMFC
Version           : 4.00
Issue type        : kbprb

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

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