what is pointer past the end of an object means?

Question

In C++ Primer, Chapter 2, \"Variables and Basic Types\", it says:

it is possible for a pointer to an object and a pointer one past the end of a different

Answer 1

It means that after

int a[] = { 1, 2 };
float b;

it's possible that (void *) &a[2] == (void *) &b may compare as true.

&a[2] (or equivalently, a+2) is a pointer just past the end of a, because the array only contains elements with indices 0 and 1.

Normally, out-of-range array indices are completely invalid (accessing a[2] is not allowed, nor is even computing &a[3]), but there is a special exception for computing the address just past the end of an array, because as it turned out, that is quite useful, for example when iterating over an array and you need an end value to know when to stop the loop.