Running method while destroying the object

Question

A few days ago my friend told me about the situation, they had in their project. Someone decided, that it would be good to destroy the object of NotVerySafeClass

Answer 1

No, no and no. This is a fundamental design issue, and it shows a common misconception in thinking about multithreaded situations and race conditions in general.

There is one thing that can happen equally likely, and this is really showing that you need an ownership concept: The function calling thread could call the function just right after the object has been destroyed, so there is no object anymore and try to call a function on it is UB, and since the object does not exist anymore, it also has no chance to prevent any interaction between the dtor and a member function.