'class' : coclass does not specify a default interface that is an event source
A source interface was not specified for a class.
The following sample generates C4681 and shows one way to resolve it:
// compile with /W4 #include <windows.h> [module(name="MyModule")]; [ object, uuid(373a1a4c-469b-11d3-a6b0-00c04f79ae8f) ] __interface IMyIface1 { HRESULT f1(); }; [ object, uuid(37331a4c-469b-11d3-a6b0-00c04f79ae8f) ] __interface IMyIface2 { HRESULT f1(); }; // uncomment out the source attribute to resolve this C4681 [ coclass, uuid(373a1a4d-469b-11d3-a6b0-00c04f79ae8f), default(IMyIface1)/*, source(IMyface1)*/] class CMyClass { }; void main() { }