Yes, you can stay on an old edition forever and not experience any of the breaking changes. But there are features that the kernel needs that rust does not support yet, such as a fallible allocation API. These features will trickle in over the next few years. In order to use them, all of the kernel's rust code will have to jump versions and deal with the breaking changes.
This happens rarely and is not considered especially burdensome.
Currently it is believed that Rust editions would be handled similarly and be no more burdensome.
The kernel absolutely does not do this "every few years".
Linux was written from day 1 in "ANSI C", which is C89 (Edit - it was actually C89 with GNU extensions. Thanks for the corrections). Only now, after 30 years of development, are they considering moving to C99, which is itself over 20 years old.
> Linux was written from day 1 in "ANSI C", which is C89.
Actually, Linux was written from day 1 in the GCC dialect of C (that is, "gnu89"), using GCC extensions without worry. Compiling the kernel with clang only became possible after clang implemented nearly all GCC extensions the kernel used.
This is laughably untrue. If it were so, ClangBuiltLinux project would have been trivial, but it was anything but. Linux was written from day 1 in GCC C, and it still is.
Sure, but bumping the minimum version of a compiler is a way different thing than taking in a new version of a language. Rust will involve a lot of the later, which is bad for the kernel IMO.
The list of backwards incompatibilities in the 2021 edition was pretty small.
I don't think that there will be a need to migrate language versions all that often, and, based on what I've seen of how Rust handles backwards compatibility, I don't think it will be an especially big leap.
I would normally agree with this, but Rust for Linux project in fact uses lots of unstable Rust features, and unstable Rust features in fact break a lot (as they should). Unstable Rust is in fact more painful than GCC C, so pain of upgrade is a genuine con against Rust. I just think benefit is larger.
Will changes to interfaces in nightly be handled similarly to how internal kernel API changes are handled? - i.e. if your code is in-tree then the mantainers of the Rust integration will update your code to ensure compatibility with the new nightly interface.
You don't need to switch editions, new language feature generally are available in old editions too. For example, generic associated types, which came out two weeks ago, work fine in edition 2015.
Incorrect. Library features like the fallible allocation API are available to all editions, for better or worse - it also means you can't make breaking changes to the standard library ever, not even with a new edition.
New language features may require a new edition, though the vast majority of them don't - here's the list of all the changes in Edition 2021 (a new one is released every 3 years): https://blog.rust-lang.org/2021/10/21/Rust-1.56.0.html
