Worth pointing out again: the size of the chunk allocated for a particular data structure does not give you the precise bounds of the data structure; odds are, the chunk is slightly larger than the structure.
I wrote a response explaining why, if you know x then you must know y, but then I realized you were talking about knowing y and learning x. Yes, I agree. I'm not sure which context (knowing the actual size of the memory chunk, which is easy, or knowing the used size of the memory chunk, which is not easy) Zed was talking about.
