5* Warning C4275: non - DLL-interface class 'class_1' used as base for DLL-interface class 'class_2'
6* Is ok, as long as no static data or CRT functionality are used under certain conditions (https://learn.microsoft.com/en-us/cpp/error-messages/compiler-warnings/compiler-warning-level-2-c4275?view=msvc-170&redirectedfrom=MSDN)
7* Neither is currently used in the base class so it should be alright.