BUG: A "C2668: 'InlineIsEqualGUID'" error occurs when you try to build a default ATL project that contains a COM object in Visual C++ (243298)

The information in this article applies to:

The Microsoft Active Template Library (ATL) 3.0, when used with:
- Microsoft Visual C++, 32-bit Enterprise Edition 6.0
- Microsoft Visual C++, 32-bit Professional Edition 6.0
- Microsoft Visual C++, 32-bit Learning Edition 6.0

This article was previously published under Q243298

SYMPTOMS

Building a default ATL project containing a COM object supporting ISupportErrorInfo might result in the following error:

C2668: 'InlineIsEqualGUID' : ambiguous call to overloaded function

This error may also occur when calling the function InlineIsEqualGUID() in your ATL project.

CAUSE

The problem occurs because the function InlineIsEqualGUID() is defined both in the ATL header file, AtlBase.h, and the Platform SDK header file, Guiddef.h, in different name spaces. The include paths for the build point first to the Platform SDK include directory, and then to the ATL include directory. In the ATL header, InlineIsEqualGUID() is defined in a name space called "ATL", while in the Platform SDK header it is defined in the global name space. Because AtlBase.h includes the statement

using namespace ATL;

the compiler is unable to distinguish which definition to use.

WORKAROUND

To work around this problem, prefix the call to the InlineIsEqualGUID() function with ::ATL::. This explicitly qualifies the ATL namespace from where the implementation of InlineIsEqualGUID is pulled in. For example:

::ATL::InlineIsEqualGUID()

STATUS

Microsoft has confirmed that this is a bug in the Microsoft products that are listed in the "Applies to" section.

MORE INFORMATION

Steps to reproduce the behavior

The following steps are based on Visual C++ 6.0.

Create an ATL DLL project and insert a simple object into the project with ISupportErrorInfo support.
Make sure that the includes path for the Platform SDK include directory comes before the ATL include directory on the Directories tab of the Options dialog box, which is accessed from the Tools menu.
Build the project, and the error message appears.

Modification Type:	Major	Last Reviewed:	9/2/2005
Keywords:	kbfunctions kbtshoot kberrmsg kbBug kbDebug kbfix KB243298 kbAudDeveloper