Simon Mourier's Blog - C++ Implementation code in an interface declaration

c/c++
delphi
direct2D

C++ Implementation code in an interface declaration

Aug 13, 2020 See the question and my original answer on StackOverflow

Only the method marked with the PURE (defined as =0) attribute really exists in the final COM vtable.

The other methods are utility methods/wrappers that contain C/C++ code that can only be used in C/C++ (they will be compiled), so you must not declare them when using another language (delphi, .NET, etc.)