CODEWITHSUNDEEP
c++memorydestructor
Slow Trout
Slow Trout

Reputation: 492

C++ Destructor - Explicit calls in an Inheritance context

I am not sure how pertinent my question is, but here it goes.

I know that we should only call the destructor explicitly when we allocated memory on the heap.

So let's say we have two classes: Animal and Dog which is a subclass on Animal.

    Animal a* = new Dog();
    //-------Do something here-----//
    a -> ~Animal();

Again, let us say that Animal contains several fields that are dynamically allocated and that the Dog class adds a couple more dynamically allocated fields.

Because Dog has more fields, calling the Animal destructor will result in memory leakage. Is this simply bad programming style or we can get a workaround?

I suppose we need to cast the pointer to the Dog type and then call the destructor, but I am unable to find any reference on how to do this correctly.

Upvotes: 0

Views: 52

Answers (2)

rlbond
rlbond

Reputation: 67789

Because Dog has more fields, calling the Animal destructor will result in memory leakage.

That doesn't happen if Animal's destructor is virtual.

Furthermore, you do not need to call ~Animal(). The one exception is if you are writing your own allocator. Normally you call delete a instead.

Upvotes: 7

Quentin
Quentin

Reputation: 63124

I know that we should only call the destructor explicitly when we allocated memory on the heap.

Nope, nope, nope, nope, nope. You never, ever call a destructor explicitly except in very specific cases (placement new and unions are the two that I know of).

What you need to do here is call delete on your pointer. And as rlbond already stated, deleting through a base pointer is fine as long as the destructor of the base class is virtual.

Upvotes: 3

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