I think it is actually really cool that RoG did not specify that part of the problem because in real life that is exactly how stuff gets specified, and plenty of times that's where the trouble comes from. Asking to revise a spec so that it is explicit is usually a very good course of action.

Not all hardware will segfault when writing to NULL, the immutable should segfault and strings that are not null terminated are indeed hard to impossible to check for (pointer wrap..., after a lot of swapping, or a stack overwrite).