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

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This article was previously published under Q218829

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SYMPTOMS

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

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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.

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RESOLUTION

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

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STATUS

Microsoft has confirmed that this is a bug in the Microsoft products that are 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:

194022 (http://support.microsoft.com/kb/194022/EN-US/ ) INFO: Visual Studio 6.0 Service Packs, What, Where, Why

194295 (http://support.microsoft.com/kb/194295/EN-US/ ) HOWTO: Tell That Visual Studio 6.0 Service Packs Are Installed

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