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Comment by simonask | Hacker News Reader

What they mean is that the Linux kernel has a long-standing policy to keep the whole kernel compilable on every commit, so any commit that changes an internal API must also fix up _all_ the places where that internal API is used.

While Rust in the kernel was experimental, this rule was relaxed somewhat to avoid introducing a barrier for programmers who didn't know Rust, so their work could proceed unimpeded while the experiment ran. In other words, the Rust code was allowed to be temporarily broken while the Rust maintainers fixed up uses of APIs that were changed in C code.

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So does this mean that the C developers might need to learn Rust or cooperate more with the rust developer team basically?

That's exactly the original question.

I guess in practice you'd want to have Rust installed as part of your local build and test environment. But I don't think you have to learn Rust any more (or any less) than you have to learn Perl or how the config script works.

As long as you can detect if/when you break it, you can then either quickly pick up enough to get by (if it's trivial), or you ask around.

The proof of the pudding will be in the eating, the rust community better step up in terms of long term commitment to the code they produce because that is the thing that will keep this code in the kernel. This is just first base.

No matter how hard you try to paint it as such, Rust is not a tribe. This is such a weird characterization.

Rust contributions to the Linux kernel were made by individuals, and are very obviously subject to the exact same expectations as other kernel contributions. Maintainers have responsibilities, not “communities”.

Not only that, those individuals were already Linux kernel contributors. This is not an amorphous external group forcing their will on Linux, it's Linux itself choosing to use Rust.

Depends on the change being made.

If they completely replace an API then sure, probably.

But for most changes, like adding a param to a function or a struct, they basically have to learn nothing.

Rust isn't unlike C either. You can write a lot of it in a pretty C like fashion.

>"Rust isn't unlike C either. You can write a lot of it in a pretty C like fashion."

I think that with all of the Rust's borrowing rules the statement is very iffy.

C has a lot of the same borrowing rules, though, with some differences around strict aliasing versus the shared/exclusive difference in Rust.

Most of the things people stub their toe on in Rust coming from C are already UB in C.

Rust's borrowing rules might force you to make different architecture choices than you would with C. But that's not what I was thinking about.

For a given rust function, where you might expect a C programmer to need to interact due to a change in the the C code, most of the lifetime rules will have already been hammered out before the needed updates to the rust code. It's possible, but unlikely, that the C programmer is going to need to significantly change what is being allocated and how.

Not talking allocations, more like actual borrowing, aliasing, passing as parameters.

Learn rust to a level where all cross language implications are understood, which includes all `unsafe` behaviour (...because you're interfacing with C).

Yes it does.

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