Rustaceans at the border [LWN.net]

Rustaceans at the border

Posted Apr 17, 2022 13:52 UTC (Sun) by tialaramex (subscriber, #21167)
In reply to: Rustaceans at the border by khim
Parent article: Rustaceans at the border

> Please think what you plan to do about that

We're not talking about a feature set here, just one number which goes up. If you have Rust 1.72 then by definition all the stable stuff from Rust 1.71, 1.70, 1.69, and so on is available. You may not care very much whether checked_div() is const (Rust 1.52), but if you want IntoIterator implemented for arrays (Rust 1.53), you'll get const checked_div into the bargain.

The feature switches I think could be more contentious because at the same time some people see value in enabling some feature switch, other people will have begun to depend on it not being present in some cases. But this is already something you see for C compiler flags.

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Rustaceans at the border

Posted Apr 17, 2022 14:12 UTC (Sun) by khim (subscriber, #9252) [Link] (1 responses)

The problem is not the “some number goes up”. The problem is that Rust is still getting major features like const generics or GATs.

And because these are significant, major features people often adopt in the matter of weeks and months. Some “conservative” crates only use features which are six months old, but not all crates which kernel may need or want would be “conservative”.

And even then six months is not much, kernel is accustomed for times measured in years. GCC 5.1 is still supported and that was released seven years ago!

That impedance mismatch would be much bigger problem than any hypothetical issue with Rust editions.

Yes, in theory Rust editions can wreak total chaos every three years. In practice that's a tempest in a teapot: they come rarely enough and changes are minor enough that this formal incompatibility rarely becomes a problem in practice.

But the requirement to use six months old compiler can be real PITA for may kernel users.

Rustaceans at the border

Posted Apr 17, 2022 23:13 UTC (Sun) by ssokolow (guest, #94568) [Link]

That said, if you'd like some concrete data, How often does Rust change? by Steve Klabnik is good.