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Q218829: FIX: CComEnumImpl<>::Skip() Doesn’t Handle Overflow Correctly

Article: Q218829
Product(s): Microsoft C Compiler
Version(s): WINDOWS:3.0
Operating System(s): 
Keyword(s): kbservicepack kbVC600bug kbATL300bug kbVS600sp2bug kbVS600sp3fix kbVS600SP1bug kbGrpDSM
Last Modified: 28-JUN-2001

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

- The Microsoft Active Template Library (ATL) 3.0, used 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 
-------------------------------------------------------------------------------

SYMPTOMS
========

If an argument passed into CComEnumImpl<>::Skip() is a negative number,
then the pointer to the current enumeration may not be set correctly.

CAUSE
=====

Following is the implementation of CComEnumImpl<>::Skip():

  template <class Base, const IID* piid, class T, class Copy>
  STDMETHODIMP CComEnumImpl<Base, piid, T, Copy>::Skip(ULONG celt)
  {
  	m_iter += celt;
  	if (m_iter <= m_end)
  		return S_OK;
  	m_iter = m_end;
  	return S_FALSE;
  }

M_iter points to the current enumeration. If celt is a negative number, Skip() is
supposed to set m_iter back "celt" items. If "m_iter + celt" results in a value
that is less than m_begin, then this case is not handled and m_iter is set to an
invalid pointer.

RESOLUTION
==========

This bug has been fixed in Visual Studio 6.0 Service Pack 3.

STATUS
======

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

This bug was corrected in Visual Studio 6.0 Service Pack 3. For more information
about Visual Studio service packs, please see the following articles in the
Microsoft Knowledge Base:

  Q194022 INFO: Visual Studio 6.0 Service Packs, What, Where, Why

  Q194295 HOWTO: Tell That Visual Studio 6.0 Service Packs Are Installed

Additional query words:

======================================================================
Keywords          : kbservicepack kbVC600bug kbATL300bug kbVS600sp2bug kbVS600sp3fix kbVS600SP1bug kbGrpDSMFCATL kbCollectionClass 
Technology        : kbVCsearch kbAudDeveloper kbATLsearch
Version           : WINDOWS:3.0
Issue type        : kbbug
Solution Type     : kbfix

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

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