specification VS JDK

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.

I felt out of the loop, thinking that Zero VM was some kind of new distro for OpenJDK but chasing <https://packages.debian.org/sid/openjdk-22-jre-zero#:~:text=...> to <https://sources.debian.org/src/openjdk-11/11.0.23%2B9-1/debi...> lead me to https://github.com/openjdk/jdk/tree/jdk-22-ga/src/hotspot/cp...

It seems that it's a specific CPU target for the Hotspot JIT for non-mainstream architectures (or for research purposes, as I saw mentioned once)

Completely gutted from the OpenJDK, last I checked. See here for the culprit PR: https://github.com/openjdk/jdk/pull/18688

> Yes, they're changing one aspect of signal handler use to work around this problem. They're not stopping the use of signal handlers in general. Hotspot continues to use signals for efficiency in general. See https://github.com/openjdk/jdk/blob/9059727df135dc90311bd476...

This whole thread is about SIGSEGV, and specifically their SIGSEGV handling. However, catching normal signals is not about efficiency.

Some of their exception handling is still odd: There is no reason for a program that receives SIGILL to ever attempt continuing. But others is fine, like catching SIGFPE to just forward an exception to the calling code.

(Sure, you could construct an argument to say that this is for efficiency if you considered the alternative to be implementing floating point in software so that all exceptions exist in user-space, but hardware floating point is the norm and such alternative would be wholly unreasonable.)

> The wonderful thing about choosing not to care about facts is having whatever opinions you want.

I appreciate the irony of you making such statement, proudly thinking that your opinion equals fact, and therefore any other opinion is not.

This discussion is nothing but subjective opinion vs. subjective opinion. Facts are (hopefully, as I can only speak for myself) inputs to both our opinions, but no opinion about "good" or "bad", "nasty" or not can ever be objective. Objective code quality does not exist.

I remember talking to Brendan about the PreserveFramePointer patch during my first months at Netflix in 2015. As of JDK 21, unfortunately it is no longer a general purpose solution for the JVM, because it prevents a fast path being taken for stack thawing for virtual threads: https://github.com/openjdk/jdk/blob/d32ce65781c1d7815a69ceac...

Map doesn't implement the Collection interface.

https://github.com/openjdk/jdk/blob/master/src/java.base/sha...