DOCUMENT:Q241852  13-JUN-2002  [visualc]
TITLE   :PRB: ERR C2535 When Compiling ATL Project with VC++ 6.0
PRODUCT :Microsoft C Compiler
PROD/VER::3.0,6.0
OPER/SYS:
KEYWORDS:kbCOMt kbVC600 kbATL300 kbDSupport kbGrpDSMFCATL

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

 - The Microsoft Active Template Library (ATL) 3.0, included with:
    - 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 
    - Microsoft Visual C++.NET (2002) 
-------------------------------------------------------------------------------

SYMPTOMS
========

You may get compiler error C2535 on a class developed in Active Template Library
(ATL) when compiled in ATL version 3.0. In previous versions of ATL, a compiler
error was not generated for the same class. For example, if your class looks
like the following, you will get the error with Visual C++ version 6.0.

   //CCOMTest
   class CCOMTest : public CComObjectRootEx<CComMultiThreadModel>
   {
   public:
       // Constructor, Destructor
       CCOMTest() {};
       ~CCOMTest() {};
       
       // Interface Map
       BEGIN_COM_MAP(CCOMTest)
       END_COM_MAP()

       DECLARE_NO_REGISTRY()
           
       // IUnknown methods
       STDMETHODIMP QueryInterface(REFIID piid, void **ppv);
       STDMETHODIMP_(ULONG) AddRef(void);
       STDMETHODIMP_(ULONG) Release(void);

    private:
       LONG   mlRef;         //Reference count
   };

CAUSE
=====

The implementation of END_COM_MAP between Visual C++ version 5.0 and Visual C++
version 6.0 has changed. In Visual C++ 5.0, END_COM_MAP was defined as the
following:

   #ifdef _ATL_DEBUG_QI
   #define END_COM_MAP()   {NULL, 0, 0}};	return &_entries[1];}
   #else
   #define END_COM_MAP()   {NULL, 0, 0}};	return _entries;}
   #endif // _ATL_DEBUG_QI

In Visual C++ 6.0, it is defined as this:

   #define END_COM_MAP() {NULL, 0, 0}}; 
   return _entries;} 	
   virtual ULONG STDMETHODCALLTYPE AddRef( void) = 0; 	
   virtual ULONG STDMETHODCALLTYPE Release( void) = 0; 	
   STDMETHOD(QueryInterface)(REFIID, void**) = 0;
   #endif // _ATL_DEBUG

RESOLUTION
==========

In Visual C++ version 6.0, you can comment out the IUnknown methods that were
implemented or add something like the following code sample:

   #ifdef _ATL_DEBUG
   #define END_MY_COM_MAP() {NULL, 0, 0}}; return &_entries[1];} 
   #else
   #define END_MY_COM_MAP() {NULL, 0, 0}}; return _entries;} 
   #endif // _ATL_DEBUG

   // CCOMTest
   class CCOMTest: public CComObjectRootEx<CComMultiThreadModel>
   {
   public:

       // Constructor, Destructor
       CCOMTest() {};
       ~CCOMTest() {};

       // Interface Map
       BEGIN_COM_MAP(CCOMTest)
       END_MY_COM_MAP()

       DECLARE_NO_REGISTRY()
           
       // IUnknown methods
       STDMETHODIMP QueryInterface(REFIID piid, void **ppv);
       STDMETHODIMP_(ULONG) AddRef(void);
       STDMETHODIMP_(ULONG) Release(void);

   private:
       LONG   mlRef;     //Reference count
   };

STATUS
======

This behavior is by design.

Additional query words: C4661

======================================================================
Keywords          : kbCOMt kbVC600 kbATL300 kbDSupport kbGrpDSMFCATL 
Technology        : kbVCsearch kbAudDeveloper kbATLsearch kbVCNET
Version           : :3.0,6.0
Issue type        : kbprb

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

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