The standard doesn't even guarantee that pointer arithmetic works at all, outside the bounds of an object (or at least did in C89, which is the only standard I know well).

If you have an object which is ten bytes long, like:

    uint8_t o[10];

...then it's legal to construct pointers to o[0] through o[10] --- not o[9]; you can create a pointer to the byte immediately after the object --- and nowhere else. Like, it's not even legal to calculate one, let alone dereference it.

I used this to make a prototype compiler from C to Javascript/Perl/Lua, where each C pointer was represented as a tuple of (array, offset). Pointer arithmetic worked inside objects; pointer arithmetic between objects wasn't supported. Worked nicely.