Rust compiler support works differently

Posted Dec 15, 2025 12:50 UTC (Mon) by farnz (subscriber, #17727)
In reply to: Rust compiler support works differently by taladar
Parent article: The state of the kernel Rust experiment

No: the reason stable distros do that is to minimize the chance that a new bug is added.

The goal is that for any x and y such that x < y, the bug list for RHEL M.y is equal to, or a subset of, the bug list for RHEL M.x, and thus that if I take your service that's running on RHEL M.x, at worst, I will find the same issues on RHEL M.y as you did on M.x, unless you depended on the OS underneath you being buggy.

This has nothing to do with backwards compatibility - your new release may be 100% compatible with the older version, and still fall foul of this policy unless it can guarantee that all bugs in the new release were also present in the older release.

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Rust compiler support works differently

Posted Dec 15, 2025 17:30 UTC (Mon) by khim (subscriber, #9252) [Link] (1 responses)

> No: the reason stable distros do that is to minimize the chance that a new bug is added.

But why that reasoning is not stopping them from bringing new code, that may need new version of compiler into the picture?

That is what driving people mad: old, stable, code is fine, I tinker with old hardware and software regularly… but then you use old tools to deal with it, too!

Why try to mix old compiler and new Linux kernel? This really makes no sense to me!

Rust compiler support works differently

Posted Dec 15, 2025 17:44 UTC (Mon) by farnz (subscriber, #17727) [Link]

The distro doesn't bring new code that needs new versions of the compiler into the picture - it locks down kernel version as well as everything else when it releases.

The kernel, however, wants people who find bugs in the distro kernel to be able to test the latest kernel, with possible fixes (and even patches on top of Linus's latest release), rather than forcing them to wait until the next distro release. And that's what drives keeping old compiler versions for the kernel - not the distros, but the kernel developers wanting to build on distros with older versions of compilers etc.

Rust compiler support works differently

Posted Dec 16, 2025 9:14 UTC (Tue) by taladar (subscriber, #68407) [Link] (6 responses)

The problem is that stable distros pretend that backports are not just new versions of the code done by people not very familiar with the code base and with a lot less testing than an upstream release though.

RHEL is one of the worst distros in terms of bugs, I have literally had multiple occasions where the core package management tools had severe bugs that made me end up with duplicate installed RPMs after a transaction segfaulted right in the middle of installing an update. I have had tools that work perfectly fine on my unstable Gentoo for years of continous updates to the latest upstream releases just break with repeated crashes.

This whole idea that the backporting process guarantees that no new bugs are introduced is just one of those lies people tell to management when they demand that something impossible has to be accomplished.

Rust compiler support works differently

Posted Dec 16, 2025 14:36 UTC (Tue) by pj (subscriber, #4506) [Link] (5 responses)

>This whole idea that the backporting process guarantees that no new bugs are introduced is just one of those lies people tell to management when they demand that something impossible has to be accomplished.

This. Why does management not understand that changing ('fixing') currently-broken code via a backported change ('fix') is at least as unstable as just upgrading? Except that by upgrading you get the benefits of all the other work that's gone into testing and fixing everything else as well, so you're much more likely to end up with a working system, and if you don't then at least it's a bug you can file against a standard version!

Rust compiler support works differently

Posted Dec 16, 2025 15:08 UTC (Tue) by pizza (subscriber, #46) [Link] (4 responses)

> This. Why does management not understand that changing ('fixing') currently-broken code via a backported change ('fix') is at least as unstable as just upgrading?

That assertion is trivially disproven by the vast difference in the size of the two diffs.

> Except that by upgrading you get the benefits of all the other work

You're conveniently discounting all of the downsides of all that other work.

Rust compiler support works differently

Posted Dec 17, 2025 9:04 UTC (Wed) by taladar (subscriber, #68407) [Link] (3 responses)

And you are conveniently discounting the opportunity cost of applying all that back porting work to something more long-term useful, e.g. adding more tests to the test-suite of the project.

Rust compiler support works differently

Posted Dec 17, 2025 13:13 UTC (Wed) by pizza (subscriber, #46) [Link] (2 responses)

> And you are conveniently discounting the opportunity cost of applying all that back porting work to something more long-term useful, e.g. adding more tests to the test-suite of the project.

Actually, I am not; I (and others here) are saying that different folks legitimately place different weights on the costs and benefits of each option, leading to different "optimal" outcomes given one's operational constraints (equipment/time/budget/regulations/etc)

...You act as if it is all costs for one option, but all benefit on the other.

Rust compiler support works differently

Posted Dec 18, 2025 9:09 UTC (Thu) by taladar (subscriber, #68407) [Link] (1 responses)

As a programmer and sysadmin of many years I am the one paying the costs for long term support distros existing at all, that is why I consider it all costs because I see how bad the LTS distros are at their stability guarantees and how many compromises we have to make by having to delay adoption of solutions for so many issues because the oldest LTS distro still doesn't have support for it.

Rust compiler support works differently

Posted Dec 18, 2025 13:48 UTC (Thu) by pizza (subscriber, #46) [Link]

> As a programmer and sysadmin of many years I am the one paying the costs for long term support distros existing at all, that is why I consider it all costs because I see how bad the LTS distros are at their stability guarantees and how many compromises we have to make by having to delay adoption of solutions for so many issues because the oldest LTS distro still doesn't have support for it.

Sure, that's fine.

Except pose this same question to *users* of LTS distros and you'll get a very different answer.

Again, different folks place different weights on the relative importance of each of the costs and benefits.

(Personally I just ignore 'em unless there's $$$ (or a patch) attached to the problem report)