What is the rationale for limitations on pointer arithmetic or comparison?

Question

In C/C++, addition or subtraction on pointer is defined only if the resulting pointer lies within the original pointed complete object. Moreover, comparison of two pointers

Answer 1

Since the C standard intends to cover the majority of processor architectures, it should also cover this one: Imagine an architecture (I know one, but wouldn't name it) where pointers are not just plain numbers, but are like structures or "descriptors". Such a structure contains information about the object it points into (its virtual address and size) and the offset within it. Adding or subtracting a pointer produces a new structure with only the offset field adjusted; producing a structure with the offset greater than the size of the object is hardware prohibited. There are other restrictions (such as how the initial descriptor is produced or what are the other ways to modify it), but they are not relevant to the topic.