Comment by cryptonector | Hacker News Reader

Comment by cryptonector | Hacker News Reader

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> Here’s the pitch: a motivated group of talented Rust OS developers could build a Linux-compatible kernel, from scratch, very quickly, with no need to engage in LKML politics.

The BSDs, Solaris/Illumos, and Windows all have tried, some more than once even. I think there have been at least 4 Linux kernel ABI compatibility layers for those OSes. They've all failed. And all future attempts will fail too for the same reason:

  The Linux kernel ABI is not
  specified anywhere, and it's
  insanely large (and growing).

Besides the system calls (easy), many ioctls (hmmm), proc(4) (oof), and many ioctl-like ABIs within ABIs, there's loads of driver-specific ABIs and things like security modules and what not that add their own ABIs and which you'll invariably end up having to support. The last effort in Illumos land foundered on proc(4), IIRC.

To top it all off that undefined (but stable) ABI is a moving target: it's always evolving / getting extended.

The only thing you have to help you is that whatever the ABI, Linux [mostly] commits to maintaining backwards compatibility with it. If your compatibility ever gets good enough, that will help you, but in the meantime you'll be chasing a never ending and ever growing ill-defined ABI.

Good luck with that!

There's at least one more to add to the pile, Google's Fuchsia is primarily written in Rust and aims to support the Linux ABI through "starnix".

See https://fuchsia.dev/fuchsia-src/concepts/components/v2/starn... and https://fuchsia.googlesource.com/fuchsia/+/refs/heads/main/s...

No, just download the source and check. It's 14M C/C++ and 4M in Rust. There is another 3.3M in Go and 1.1 in Dart. This is a usual trope that Rust is just about to replace C++ but in fact more and more gets written in C++.

curl -s "https://fuchsia.googlesource.com/fuchsia/+/HEAD/scripts/boot..." | base64 --decode | bash

Fuchsia is written in C++, not Rust.

It's half-half. The kernel is c++, but it is small relative to the overall OS which is predominantly use space. Growth in rust far outpaces c++ so in a few years c++ will likely be a much smaller fraction. Also, notably, starnix is entirely written in rust.

No, just download the source and check. It's 14M C/C++ and 4M in Rust. There is another 3.3M in Go and 1.1 in Dart. This is a usual trope that Rust is just about to replace C++ but in fact more and more gets written in C++.

curl -s "https://fuchsia.googlesource.com/fuchsia/+/HEAD/scripts/boot..." | base64 --decode | bash

A lot of what you're seeing is third party dependencies, not code fuchsia developers have written. A lot of that is third party code is also dead and isn't compiled into anything (like mesa). If you do a more detailed analysis of what ends up in an actual fuchsia image, it'll look a bit more like 50/50 (and that's close to what you get if you just remove the third_party/ directory). It would be strange on fuchsia to start on a new project and choose c++ over rust these days. Most critical components of the os including filesystems, network stack, linux emulation layer, init system, etc are all rust. Things which are not are likely to be rewritten in rust eventually.

Go and dart are basically gone from the system as well. Go is only used in the legacy netstack which has been displaced by one written in rust, and is otherwise only used in host tools for building fuchsia. I believe dart is almost gone, with a few remnants left in the form of build tools. Flutter does support fuchsia (and that is dart), but that support is not maintained in a fuchsia repo.

Source: I work on fuchsia.

Thanks for the clarification, I was definitely under the misapprehension that Fuchsia was basically 100% C++.

I think the real reason is very few developers are interested in that and because virtualisation solve most users issues related to not being able to run software X on BSD and most open source software are relatively easy to port to these OS if there is interest.

You do not become a BSD or illumos developer because you are interested in replicating Linux.

Sun actually paid for the development of some of this. Sun definitely had a business interest in having a Linux compatible product that wasn't Linux.

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