Question

Would it be a bad design, that a child class inherit a parent class that has no destructor (only the default generated by compiler) ? Some books claimed it’s not good, but didn’t mention under what situation it would.

Answer 1

Deleting an object of a derived type through a pointer to a base type with no virtual destructor is undefined behavior. If you expect to do this, and so in general if you expect your class to be extended, you should provide a virtual destructor.

 struct A
 {};
 struct B : A
 {}

 //...
 A* a = new B;
 delete a;       //undefined behaviour