From the C11 spec quoted in the article > If both the pointer operand and the result point to elements of the same array object, or one past the last element o

From the C11 spec quoted in the article > If both the pointer operand and the result point to elements of the same array object, or one past the last element of the array object, the evaluation shall not produce an overflow; otherwise, the behavior is undefined. So although most implementations might produce an address that's relative to b, that's not actually guaranteed by the spec unless it's `&b + 1`.