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Perhaps that list should be updated on the Rust website then :P. Last I counted the Nomicon had like 10 different UB behaviors listed, and the C spec has what, 240?

Replying to

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Maybe? Compare doc.rust-lang.org/nomicon/what-u, ralfj.de/blog/2020/12/1 and the papers on clang. What I study is C++, not Rust, but the Rust list doesn't look too convincing, assuming Ralf is right (which seems the most likely thing).

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Rust doesn't do TBAA and doesn't really need it due to the &T and &mut T restrictions so that's a lot of complexity that's avoided. It doesn't have the pointer provenance rules but LLVM doesn't really document what they do and my generic wording was lost when they updated it.

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(generic wording? Do you have a link to the original, correct docs as you wrote them?)

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The list there is almost the same as my original list but someone declared it complete/exhaustive when it originally didn't claim that, and the part about aliasing was ruined. Whoever replaced that seemed to miss a lot of the point. Not my problem to resolve though.

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LLVM considers NoAlias to be about lack of memory dependencies between types. That means &T for types without interior mutability (which has to be declared) is NoAlias in the LLVM sense. Also, that list is clearly missing the rules about immutability, among various other things.

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Rust's rules for UB in unsafe code will definitely be a lot simpler than C and it doesn't have UB in safe code. I strongly dislike the style that the documentation was remade into and part of that is it deliberately eschews accuracy in favor of being amusing and comforting.

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It was originally worded like a specification and was called a language reference. It was supposed to be a serious document defining the language, not a tutorial. Okay, here, look at this instead: doc.rust-lang.org/stable/referen This is the proper documentation, not that thing.

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(FWIW, your link is the documentation I remember on what's considered UB. I've brought up before on here that I don't care for the whimsiness of the Rustnomicon. But outside of limited contexts like this one, criticizing the tone of that document leads to... issues.)

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I have serious issues with one of the main people originally responsible for it and they were the main reason that I became increasingly frustrated/disenchanted with the project and decided to resign from it and move on.

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Taking stuff I made (code, docs) and ruining it while taking full credit for it is part of that, but a pretty small part overall. Anyway, probably best not to think too much about it. I like Rust quite a lot as a language and that's why I contributed a ton to it... but...

11:12 PM · Jul 6, 2021Twitter Web App

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Yea, I uhhh... just learned in the past 15 minutes or so why you decided to stop contributing. I probably wouldn't have brought this topic up had I known, but I appreciate the answers anyway.

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Just be aware that when I stopped contributing and resigned + removed my own commit access, someone wrongly assumed that I was 'kicked out' and accidentally made a whole drama out of it. A few people who didn't like me rolled with it and to this day it's used to attack me.

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... I had quite major issues with how it was developed, how developers outside Mozilla were treated at the time (i.e. myself) and my criticism of design issues and approaches to docs/implementation/designs were taken very personally and were responded to in underhanded ways.