Question

Assuming I have a pointer ptr and I allocate some space for that pointer. Now, if I have another pointer ptr2 and do this:

ptr2 = ptr;

Does this mean I allocate space for ptr2 or do I need to allocate for ptr2 by myself?

Answer 1

Well, depends what you mean by “allocate space for a pointer”.

For example:

int* ptr;

allocates space for the pointer in automatic memory. The pointer doesn’t point to anything meaningful though. If you did:

int* ptr = new int;

you have space allocated in automatic memory for the pointer itself, and that pointer points to the memory allocated by new int, which is in dynamic memory.

If now you did:

int* ptr2 = ptr;

you have some memory in automatic memory for ptr2 itself, but it will point to the same location in dynamic memory as ptr.

So in the end, you have allocated memory for 2 int*s in automatic storage, and for one int in dynamic storage. The two pointers point to the same memory.

The automatic memory is cleaned up automatically (duuh). You have to delete the dynamically allocated memory yourself:

delete ptr;

Note that since the two point to the same location, so:

delete ptr;
delete ptr2;

would yiled undefined behavior (so is illegal).

(this is all subject to optimizations, but, in principle, it goes down like this)