Compiler Error C3121

 

The new home for Visual Studio documentation is Visual Studio 2017 Documentation on docs.microsoft.com.

The latest version of this topic can be found at Compiler Error C3121.

cannot change GUID for class 'class_name'

You attempted to change the class ID with __declspec(uuid).

For example, the following code generates C3121:

// C3121.cpp  
[emitidl];  
[module(name="MyLibrary")];  
  
[coclass, uuid="00000000-0000-0000-0000-111111111111"]  
class __declspec(uuid("00000000-0000-0000-0000-111111111112")) A   // C3121  
{  
};  
int main()  
{  
}  

Show: