Pointers and collection of pointers in C++. How to properly delete

Question

This is a newbe question but I have alwasy doubts with pointers in C++. This is the situation.

I have a class A which as a collection (a vector actually) of pointers of class B. This same class A has another collection of pointers to class C. Finally the objects of class B have also a collection to pointers to class C which point to the same instances the class A points to.

My question is, if I delete a member of class-C-type pointer in class B, what happens to the pointer in class A that points to the deleted instance of class C? How this situation has to be treated?

Thanks a lot in advance!

Julen.

Answer 1

My understanding:

A
 - vector<B*>
 - vector<C*>

B
 - vector<C*>

From within B you are deleting all of the C*.

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You need to delete each memory address separately, but only at most once.

Any pointer to a deleted address is still holding the same address, it just produces undefined behavior if you use it.

So be sure not to re-delete the B* from A that you already deleted, and be sure not to use them after they are deleted.

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You may want to re-consider your hierarchy/design though.

Or consider using boost::shared_ptr if you need to store things in this way. Actually anytime you're storing a collection of pointers you should probably be using boost::shared_ptr. If you are using boost::shared_ptr you don't delete and you don't need to worry about invalidating the other pointers.