Question

Would the following properly destroy everything (all appropriate destructors called and all memory freed)?

Class* var[50];
var[0] = new SubClass();

delete[] *var;

Similar to

Class** var = new Class*[50];
var[0] = new SubClass();

delete[] var;

Or should I be iterating over the array and delete each individual object (which is what I thought delete[] did).

Answer 1

Class* var[50];
var[0] = new SubClass();

delete[] *var;

This is undefined behavior. The proper way is

delete var[0]; //equivalent to delete *var;

If you allocate memory for all 50 elements of the array, then you have to iterate and delete each one of them. Think of it this way:

• for every new, you should have an associated delete
• for every new[], you should have an associate delete[]
• don’t mix up new with delete[] and new[] with delete as it leads to undefined behavior

Your second snippet is illegal C++.

EDIT As you’re clearly a beginner, let’s break this down a bit. Since the second snippet doesn’t even compile, I’m going to focus on the first one:

Class* var[50];

This declares an array of 50 pointers to Class. The pointers are dangling – they are not initialized and Class objects aren’t created.

var[0] = new SubClass();

This allocates memory for a SubClass object and assigns the first pointer in the array. All other pointers remain uninitialized.

*var;

returns the first element, which is a Class*. It’s equivalent to var[0].

delete[] *var;

attempts to call delete[] on a Class*, which was allocated with new, so it results in undefined behavior.