Variable length integers are used in many places (protobuf, utf, etc), so you could also have unbound length there as well.

My 100% perfect concept ( :D ) would be [length]<here's the pointer>[data]where length would be read high to low. Because of the functionally upper capped length (maximum address space) we can treat accessing that as O(1) vs. O(N) for null termination, etc.