[zenogais]

> This way you don't need to worry about keeping track of size and capacity either.

The only reason you don't have to worry about this is because std::vector handles it for you, at least in the code examples provided by the author. If you choose to go with a pure C implementation (which is what I'm trying out) then you will have to keep track of these.

> The reason I suggested -1 is because when we iterate through bd->items, we need a way to know if it's a valid value or just "holed".

Yep, I was able to get an example using -1 as a sentinel working and passing fuzz testing.