Later on you can drop the diagrams entirely and perhaps keep them as some onboarding documentation if they're still useful.

Better title: "Why are drivers killing more pedestrians?"

[1]: http://www.robertgamble.net/2012/01/c11-generic-selections.h...

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.

I think I've figured out roughly what the author intended, code below [0].

First, it looks like he's relying implicitly on data stored in std::vector. Namely vectors have both a capacity and a size. The capacity is total number of allocated elements. The size is the total number of elements stored actually stored.

Second, vector::resize won't reallocate until it runs out of capacity, but it will give you access to extra elements if you need them. So this is used to lazily re allocate while bumping up the size of the vector.

Both of these effectively make it "do the right thing" by leaning on the vector storing both size and capacity.

If you hand manage those values yourself you can get a pretty compact C implementation without a lot of code.

One last thing: Using a union here for the item_t is pretty much guaranteed to get you a segfault. The whole thing should really be a struct. This also allows for setting next to sentinel value if necessary.

[0]: C code for bulk_data_t example: https://pastebin.com/Tfcdt39h

For the bulk data with holes code:

First, there's an initialization step that has to happen the first time you allocate your bulk_data_t. Namely, you need to iterate through every item in the list and set its next_free item to the item following it, looping the last item back around to zero. You also need to do this for all the items between the new size and old size every time you resize your item list.

Second, safe iteration over all of the bulk data doesn't seem possible without adding some sort of flag to indicate whether or not an item is free.

Am I missing something here?

[1]: https://jacobitemag.com/2017/08/29/a-i-bias-doesnt-mean-what...

This reads largely like a recapitulation of Boehm's 2003 book "Balance Agility and Discipline" [1]. Have you read this and did this provide any inspiration for the article?

[1]: https://www.amazon.com/Balancing-Agility-Discipline-Guide-Pe...

See this wikipedia page for a list of all such authors: https://en.wikipedia.org/wiki/Aphorism