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Compiler Warning (level 1) C4581

deprecated behavior: '"string1"' replaced with 'string2' to process attribute

This error can be generated as a result of compiler conformance work that was done for Visual C++ 2005: parameter checking for Visual C++ attributes.

In previous versions, attribute values were accepted whether or not they were enclosed in quotation marks. If the value is an enumeration, it must not be enclosed in quotation marks.

The following sample generates C4581.

// C4581.cpp
// compile with: /c /W1
#include "unknwn.h"
[object, uuid("00000000-0000-0000-0000-000000000001")]
__interface IMyI : IUnknown {};

[coclass, uuid(12345678-1111-2222-3333-123456789012), threading("free")]   // C4581
// try the following line instead
// [coclass, uuid(12345678-1111-2222-3333-123456789012), threading(free)]
class CSample : public IMyI {};
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