Comment by burfog | Hacker News Reader

Comment by burfog | Hacker News Reader

Parent Full thread

Async/await appears to require runtime support, possibly even a modern OS. Wasn't rust supposed to be suitable for writing bare-metal code?

SIMD at least has hope of running on bare metal. I suppose the ideal is to have it adjustable: compiled to non-SIMD, using typical SIMD hardware, using implicit threads (and thus needing OS support), or using SIMD hardware with threads.

I fear the high-level web developers are in the driver's seat, which may doom rust as a systems language. I'm hesitating on rust because I would miss bitfields and various unsafe performance features. I like the opt-out safety of the "unsafe" keyword, but I want more things that I can opt out of. I want goto, computed goto, no-default switches, something like Microsoft's __assume keyword, and all the other low-level stuff you'd want for making boot loaders and high-performance kernels.

> Async/await appears to require runtime support, possibly even a modern OS. Wasn't rust supposed to be suitable for writing bare-metal code?

You're probably thinking of Tokio, the library for async network IO, which obviously depends on an OS. The async/await language feature compiles down to basically a state machine and has minimal runtime requirements. I'm looking forward to using it on bare-metal microcontrollers.

async/await in Rust produces a single value, a Future. Executing that future requires calling its poll method repeatedly. That can be extremely simple, or it can be more complex. We call "a thing that calls poll repeatedly" an executor, and they can be written without an OS or even the standard library, just fine.

The largest, most well known executor is Tokio, which is built on top of OS primitives. If you're writing your own OS, you'd use those primitives.

> I fear the high-level web developers are in the driver's seat

First, I pretty fundamentally reject this as an idea, but since you don't, please do a Google Scholar search for many of the core team members. They're very much not web developers.

Reply on news.ycombinator.com