Compiler Warning (level 4) C4680


For the latest documentation on Visual Studio 2017, see Visual Studio 2017 Documentation.

'class' : coclass does not specify a default interface

A default interface was not specified for a class that was marked with the coclass attribute. In order for an object to be useful, it must implement an interface.

The following sample generates C4680:

// C4680.cpp  
// compile with: /W4  
#include <windows.h>  
[ object, uuid(373a1a4c-469b-11d3-a6b0-00c04f79ae8f) ]  
__interface IMyIface1  
   HRESULT f1();  
[ object, uuid(37331a4c-469b-11d3-a6b0-00c04f79ae8f) ]  
__interface IMyIface2  
   HRESULT f1();  
// to resolve C4680, specify a source interface also  
// for example, default(IMyIface1, IMyface2)  
[ coclass, uuid(373a1a4d-469b-11d3-a6b0-00c04f79ae8f), default(IMyIface1), source(IMyIface1) ]  
class CMyClass : public IMyIface1  
{   // C4680  
int main()