Are non dereferenced iterators past the “one past-the-end” iterator of an array undefined behavior?

Question

Given int foo[] = {0, 1, 2, 3}; I want to know if iterators that point past the \"one past-the-end\" are invalid. For example: auto bar = cend(foo) + 1;

Answer 1

I'm not interested in that case unless it is called out in the standard as the reason we can't have an iterator past the "one past-the-end". I know that int* really just holds an integer value, and as such is subject to overflow.

The standard doesn't discuss reasons for making things undefined. You've got the logic backwards: The fact that it's undefined is the reason that an implementation may put an object in a location where doing such a thing would otherwise cause an overflow. If a "two-past-the-end" iterator were required to be valid, then implementations would be required not to put an object somewhere that might cause such an operation to overflow.