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Article ID: 192561 - Last Review: December 10, 2003 - Revision: 2.0
PRB: Error C2787 When Building a Project Using ATL 3.0
This article was previously published under Q192561
When building a project with ATL 3.0 you may get a compiler error c2787 (no
GUID has been associated with this object).
The newer versions of MIDL use the compiler facility [__declspec(uuid())]
to tag a GUID to an interface in the header files it generates. ATL version
3.0 makes use of this fact in the implementation of COM_INTERFACE_ENRY
macro; it now uses the keyword __uuidof() to extract the interface ID from
the MIDL-generated header. ATL 2.1 uses the token pasting operator
(IID_##IFoo) to get the interface ID. This action requires including the
MIDL-generated header and also the "project_i.c", which MIDL generated.
If you use an older MIDL-generated header file [which does not use
__declspec(uuid())] with ATL 3.0, you will get this compiler error, because
__uudiof() can't extract the interface ID.
Define the preprocessor symbol _ATL_NO_UUIDOF in the C/C++ tab of the
Project Settings dialog box. This forces ATL to use the token pasting
operator (##) rather than __uuidof() when forming the interface ID.
This behavior is by design.
Sample Code
COM_INTERFACE_ENTRY in ATL 2.1
#define COM_INTERFACE_ENTRY(x)\
{&IID_##x), \
offsetofclass(x, _ComMapClass), \
_ATL_SIMPLEMAPENTRY},
COM_INTERFACE_ENTRY in ATL 3.0
#ifndef _ATL_NO_UUIDOF
#define _ATL_IIDOF(x) __uuidof(x)
#else
#define _ATL_IIDOF(x) IID_##x
#endif
#define COM_INTERFACE_ENTRY(x)\
{&_ATL_IIDOF(x), \
offsetofclass(x, _ComMapClass), \
_ATL_SIMPLEMAPENTRY},
Newer MIDL headers files use the macros DECLSPEC_UUID() or
MIDL_INTERFACE(), which expand to __declspec(uuid()). MIDL versions 3.01.75
and later use the __declspec directive.
"Porting from ATL 2.1" in the online help.
(c) Microsoft Corporation 1998, All Rights Reserved. Contributions by
Jaganathan Thangavelu, Microsoft Corporation.
APPLIES TO
- Microsoft ActiveX Template Library 3.0, when used with:
- Microsoft Visual C++ 6.0 Enterprise Edition
- Microsoft Visual C++ 6.0 Professional Edition
- Microsoft Visual C++, 32-bit Learning Edition 6.0
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