compiler-team VS specification

> Also, why aren't we size-sorting fields already?

We are for struct/enum fields. https://camlorn.net/posts/April%202017/rust-struct-field-reo...

There's even an unstable flag to help catch incorrect assumptions about struct layout. https://github.com/rust-lang/compiler-team/issues/457

Are you talking about https://github.com/rust-lang/compiler-team/issues/688 ? I think that issue provides a lot of interesting context for this specific improvement.

And mips64, which rustc recently dumped support for after their attempt to extort funding/resources from Loongson failed:

https://github.com/rust-lang/compiler-team/issues/648

This is the biggest problem with the LLVM mentality: they use architecture support as a means to extract support (i.e. salaried dev positions) from hardware companies.

GNU may have annoyingly-higher standards for merging changes, but once it's in there and supported they will keep it for the long haul.

See https://github.com/rust-lang/compiler-team/issues/688

The work has been going on for some time now and it seems we are quite close to it being enabled as a default for nightly builds, I am super thrilled upwards of 20% faster clean builds and possibly more are on the horizon. Hope everything works out without triggering some unseen ICE. https://github.com/rust-lang/compiler-team/issues/681 Edit: If you want to discuss this feature reach out on Zulip

I'd recommend reading the MCP[1] they linked regarding the decision as well as their target tier policy [2].

They are dropping tier 1 support for Win 7 and Win 8. That means they are no longer going to guarantee that the project builds on those platforms and passes all tests via CI.

As long as it is feasible they will probably keep CI runs for those platforms and if interested parties step up and provide sufficient maintenance support, it will remain tier 2. i.e a guarantee that it builds on those platforms via CI but not necessarily that all features are supported and guaranteed via passing tests.

If interested parties can provide sufficient maintenance that all tests continue passing, it will be tier 1 in all but name. However the rest of the development community won't waste their time with issues like Win 7 and 8's partial support for UTF-8.

And once CI stops being feasible for the compiler team to host, it'll drop down to tier 3. If there's sufficient interest from the community towards maintaining these targets, in practice you should see comparable support to with tiers 1 or 2 however now any CI will be managed externally by the community and the compiler team will stop worrying about changes that could break compilation on those targets.

TLDR: They aren't saying "it'll no longer work" but rather "if you want it to stay maintained for these targets, you have to pitch in dev hours to maintain it and eventually support the infrastructure to do this because we don't see a reason to continue doing this". So if you care for these targets, you'll have to contribute to keep it maintained.

[1]: https://github.com/rust-lang/compiler-team/issues/651

(The already broken) XP support was removed almost 3 years ago: https://github.com/rust-lang/compiler-team/issues/378

Many people misunderstand how software is written in regulated industries, and assume that a standard is necessary. In practice, this is not the case. Note that Ferrocene[1] had to produce a specification[2] in order to qualify the compiler. But there isn't a requirement that it must be a standard in any way, only that it describes how the Ferrocene compiler works. Nor that it be accepted by upstream.

1: https://ferrous-systems.com/blog/officially-qualified-ferroc...

2: https://github.com/ferrocene/specification

If by "no standard" you mean that there is no language specification for rust, then there is no standard. However, a language specification is not sufficient to verify program correctness, nor is it required.

A standard may (and the C standard for example does) leave parts of the behavior as "implementation specific" and there's quite a few edge cases - and that's not even talking about "undefined behavior", of which there is plenty. An even in the behavior that is neither implementation specific nor undefined you'll find enough rope to hang yourself (all the beautiful pointers).

On the other hand, the rust language - while having no formal spec - is fairly well described, in the form of its RFCs and testsuite. We (the ferrocene team) were able to derive a descriptive specification from the existing description fairly easily. So while there is no ISO standard, and no spec that would be sufficient to write a competing implementation, there is a description of what the language behaves like. You can read up on it at https://spec.ferrocene.dev/

As for verification of correct behavior of such a program, you can employ a host of different techniques depending on what your requirements are - down to verification of the produced bytecode by means of blackbox testing or other.

They created a specification for Ferrocene because Rust does not yet have a language standard:

https://spec.ferrocene.dev/

>> But does the language need a standard?

Yes, Rust needs a standard.

>> And if so, then for what purpose?

For the same purpose that all standards have--to formally define it in writing.

Ferrocene's web site (https://ferrous-systems.com/ferrocene/) shows that it meets the ISO 26262 standard (https://en.wikipedia.org/wiki/ISO_26262).

Why does ISO 26262 matter? What purpose does it serve? Couldn't a vehicle manufacturer just say "our vehicles are safe"? Which would you trust more: a vehicle that is verified to meet ISO 26262 standards, or a vehicle whose manufacturer tells you "it's safe"?

https://github.com/ferrocene/specification

They do say any differences between it and upstream behavior or documentation is a defect in the spec, not upstream. So it isn't authoritative. Unless we all decide it is.

>> The spec does not define the software. The software is as the software does. Having or not having a spec doesn't protect from bugs - people do.

>> What you're taking about is covering one's ass, not specification.

They are related.

In safety-critical software, bugs can cause people to die. Without a spec, no one will use Rust for safety critical software. It would be too risky and no company would accept that level of risk.

For example if software that controls an airplane is written in Rust and an error occurs during flight, what happens? The software can't just panic and crash or the airplane might crash.

The Ferrocene project (https://ferrous-systems.com/ferrocene/) is working on producing a safety-critical Rust specification (https://github.com/ferrocene/specification) because having a language specification matters for safety-critical work.

I'd like to clarify a little here: There's an ISO certifiation in here - but it's not an ISO standard for the language.

Essentially, the ISO 26262 certification verifies that the compiler release process conforms to a certain standard. It does not create an ISO standard for rust, not does it aim to. At part of the certification process we had to write a spec for the rust language, but it is a descriptive spec of how certain aspects of the rust language behave for one specific release of the compiler.

The certification builds on this to ensure that tests catch deviations from the spec, known problems are documented etc. So rust as a language is unaffected, as is the rust project. The spec is open source and might be useful to others, you can find it at https://spec.ferrocene.dev/

The target sectors for ISO 26262 and related industrial certification are clearly sectors that require such certification: automotive, medical, etc.

Ferrocene itself however, is not only the ISO certified downstream of the rust compiler, it also offers for example long term support and tracking of known issues which the rust project does not provide. This is also important for certain applications that do not strictly require certifications.

>> Rust is defined by the implementation.

Hopefully not for long:

https://github.com/ferrocene/specification

https://ferrous-systems.com/blog/the-ferrocene-language-spec...

Hopefully Ferrocene can lead to Rust itself being standardized.

To me, it seems inevitable that there will be multiple implementations of Rust, especially if Rust continues to be more widely adopted and used in new domains.

I would also not be surprised if Rust were to adopt optional language extensions for specialized use cases, similar to Ada's language annexes:

http://www.ada-auth.org/standards/22rm/html/RM-1-1-2.html

Why? Because the Rust implementation you use for video game programming does not need all of the same features as the Rust implementation that you use for safety-critical embedded systems (for example: railroad control software).

That’s an easy enough problem to solve (though time consuming), and Ferrocene is working on it. Having >1 compiler implement the spec is just a human fuzz test that finds edge cases, and that’s a good thing.

I don't know what ISO-26262 requires, but for IEC-61508 only requires "The language should be fully and unambiguously defined." - which I think Ferrocene has taken a decent stab at with https://spec.ferrocene.dev , and an accompanying ISO standard is not a hard requirement.