If I remember correctly, he meant that only array accesses are used, because their length can be checked (as all arrays have a static length due to no dynamic memory).
Indeed, this is what many people do. But even if you use dynamic memory, if you replace pointer arithmetic by array indexing, you get bounds checking. And in C this also works for arrays of run-time length.
if "array" has a bound whatever expression evaluates to can be checked against the bound of array. If "array" is not a bounded array but a pointer or an unbounded array, then this does not work, but my point is that it is easy to avoid such code.
