Question

Say I have two items on the heap:

Foo *f = new Foo;
Foo *g = new Foo[42];

And say I have a function that receives a Foo pointer and within the function it needs to perform a delete:

void bar(Foo *p) {
    // some stuff
    delete p;
}

This function might be called like so:

bar(f); // passing a pointer to a Foo object on the heap
bar(g); // passing a pointer to an array on the heap

I recognize that delete[] and delete should be used to free memory allocated with new[] and new respectively; However since the function doesn’t know if its parameter p was allocated with new or new[], how can this function properly delete or delete[]?

Answer 1

You can’t (portably) detect that and do the right thing in the function.

A “workaround” would be to use std::vector<Foo> instead of the array, and just always use delete.