Q140229: PRB: C2027 When Using MFC Templated Collection Classes

Article: Q140229
Product(s): Microsoft C Compiler
Version(s): 4.00
Operating System(s): 
Keyword(s): kberrmsg kbprb
Last Modified: 30-JUL-2001

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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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