An array can be variably-sized in C (C99, that is). And thank you, I know the difference between an array and a pointer. You just seem to have arbitrarily interpreted the question to limit it to C89 and a fixed-size array in order to make your solution work.
This has nothing to do with it being statically sized or variably sized. You have to know what size it is when you are going to reverse it. The solution presented works as long as the programmer knows what the size is.
If you want to posit any kind of sane question, then you can have a sane solution.
Well, suppose I have an array `A' of size `len'. How would you write an algorithm that reverses that array in place, without using any temporary variables, and that works for arbitrary values of A and len? I think the answer is "you can't". You can't claim to have a solution for the problem if it only works for a fixed input, and if the solution itself would be different for different inputs.
