Brimstone: ES2025 JavaScript engine written in Rust

Memory safety is one of Rust’s biggest selling points. It’s a bit baffling that this engine would choose to implement unsafe garbage collection.

The obvious use-case for unsafe is to implement alternative memory regimes that don’t exist in rust already, so you can write safe abstractions over them.

Rust doesn’t have the kind of high performance garbage collection you’d want for this, so starting with unsafe makes perfect sense to me. Hopefully they keep the unsafe layer small to minimise mistakes, but it seems reasonable to me.

I'm curious if it can be done in Rust entirely though. Maybe some assembly instructions are required e.g. for trapping or setting memory fences.

If it comes to it then Rust has excellent support for inline assembly

But how well does it play with memory fences?