C++ is Virtual destructor still needed if there are no data members in derived?

Question

Suppose I have this code

class Base{
  public:
        int getVal();
  private:
         int a, b;
};

class Derived::public Base{
    public:
         void printVal();
};

int main(){
    Base *b = new Derived();
    delete b;    
}

I know a virtual destructor would delete things properly, but is it bad to delete with base pointer (when there is no virtual destructor) even if there are no virtual functions and no data members in the derived class? What will happen if this is done?

Answer 1

For primitive-type data, your example will most likely work in practice. As a matter of fact, incurring a vtable could actually hinder performance (so there may be some legitimate use here), but it is technically undefined, per 5.3-5.4:

If the static type of the operand [of the delete operator] is different from its dynamic type, the static type shall be a base class of the operand's dynamic type and the static type shall have a virtual destructor or the behaviour is undefined.

It really all depends on the "heapness" of the data in your class, and as there are no heap-allocated members (in your case), you should be fine, but it's definitely a code smell.