Calling delete on std::stack of pointers

Question

I have a std::stack which has some pointers inside:

std::stack<State*> m_states;

When I initialize my program, I call new to push an item onto the stack (it must be a pointer because I will use polymorphic types).

Is this the correct way of deleting with all the stuff?

Here is where I call new (GameState and MenuStatesare classes inherited fromState`):

m_states.push(new GameState());
m_states.push(new MenuState());

And this is what I have in the destructor of the whole App class:

while (!m_states.empty())
{
    delete m_states.top(); // (*)
    m_states.pop();
}

Should I only call (*), or do I need to pop() as well?

Better to use a unique_ptr and not have to deal with cleanup at all. — super
– super, Commented Nov 20, 2021 at 22:15

Adrian Mole · Accepted Answer · 2021-11-20 22:04:34Z

4

Should I only call (*) or do I need to pop as well?

Well, if you don't call pop() in the while loop, then how will that loop ever end? In other words, how will the condition, !m_states.empty() ever become false?

There are other container types (like std::vector) where you could just run through each member, deleting the pointed-to object, and then clear the container, but you can't do that with the std::stack container. That is to say, there is no [] operator for a stack – you can only access the top element.

answered Nov 20, 2021 at 22:04

Adrian Mole

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