[rafaelmn]

Why ? If it's shared reads and scoped writes (read-only look up, output to a thread owned buffer span) concurrency seems pretty straightforward.

Rust can only prove a limited subset of correct programs to be safe, when you're doing bare metal stuff you've often not in that subsystem and drop down to unsafe. I'm guessing there's always stuff that's not perf critical and can live in Rust sandbox - so not saying no wins - but it doesn't sound like Rust is a no-brainer.

[alkonaut]

I mean all else being equal, I'd just take the ergonomics (dependency management, build-system/multi-targeting, modern language features, no h-files, ...) and run. I can always just write at the level I want (safe rust, unsafe rust, C, inline asm...).

I still think no one should in 2026 be writing a nontrivial codec or anything parsing untrusted data, in C. There's just no excuse.

The gains are re-use of skill and code. And I hope that's the reason this is continuing with C, this is basically a v2 of an existing project, not a greenfield codec, even if it's much larger.