More that I got confused by the C function returning bool, not as an error value, but as a result, which is my fault for skimming it quickly.

I have taken a closer look at the code, and it seems superficially a somewhat faithful rewrite, not quite idiomatic Rust, but closer than I anticipated at first. I know there are non-LLM rewriting tools for C to Rust, and with a test suite to help, a rewrite to Rust might be greatly helped. The new Rust code does have some drawbacks in some ways, and there are topics I am curious about.

Wow, I would love to read an interview series based on this!!

I guess there also were macro-assemblers before C, so it was a bit more natural.