Simple dynamic array question

[laserlight]

A related question: if the extent of a dynamic array is guaranteed to be knowable to the run-time, why isn't it accessible via an API call to the programmer?

But it is, via the capacity() member function.

EDIT:
Oh wait, you are talking about the dynamically allocated arrays managed manually, rather than dynamic array functionality provided by std::vector. In that case, perhaps a possible answer is that such knowledge is likely to be implementation dependent, and hence unsuitable for a standard library.