Comment by ekr____

Author here. Quite so. See footnote 3:https://educatedguesswork.org/posts/memory-management-1/#fn3

"If you know you're going to be doing a lot of reallocation like this, many people will themselves overallocate, for instance by doubling the size of the buffer every time they are asked for more space than is available, thus reducing the number of times they need to actually reallocate. I've avoided this kind of trickery to keep this example simple."