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Comment by f311a | Hacker News Reader

Unfortunately, Rust is not a good choice for this kind of tricks. This is where Zig shines. In Rust, you can’t even use proper arenas, which can help a ton with allocations.

Cloudflare started to pick Zig recently, for projects, that have memory constraints.

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> In Rust, you can’t even use proper arenas

You definitely can and this is done a lot. What you might mean is that you can't use standard library's collections with them (this is getting stabilized soon!) and have to use third-party, but that is a different thing than "can't use arenas".

> Rust is not a good choice for this kind of tricks.

Rust can do those tricks, but it's true that it is hard than in C or Zig. That said there are often crates to help.

Stabilized soon, really? They did not stabilize it after 10 years and were thinking about different approach. I thought it’s dead.

Yes, really. The design has been decided upon ( https://hackmd.io/nNHdKkp1TTK7jat0I-ABqA ) and the implementation has been updated to match ( https://github.com/rust-lang/rust/pull/157428 ). The stabilization PR is just waiting on final approval by the relevant team members, with no remaining concerns currently listed: https://github.com/rust-lang/rust/pull/156882#issuecomment-5...

I'd like to know why I can't use arenas in rust? Especially considering that I have used them before in rust.

You can’t allocate collections without nightly or without reimplementing them in the library. Every implementation uses it’s own set of trade offs to provide safety in unsafe implementation.

Rust supports arenas just fine ( https://crates.io/crates/bumpalo ), and if you mean the support for using custom allocators in the standard library collections, that's as stable as Zig is.

There are more than 10 crates for arenas with different tradeoffs, I'm well aware of them. They are still very limited compared to C/Zig.

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