Rust GCC backend: Why and how
Posted by ahlCVA 20 hours ago
Comments
Comment by mastax 18 hours ago
Is libgccjit not “a nice library to give access to its internals?”
Comment by compiler-guy 15 hours ago
The MIDI protocol is pretty good for what it is designed for, and you can make it work for actual real networking, but the connections will be clunky, unergonomic, and will be missing useful features that you really want in a networking protocol.
Comment by aargh_aargh 10 hours ago
Comment by jacquesm 11 hours ago
Comment by compiler-guy 11 hours ago
Googling “slip over midi” gives a lot of fashion blogging about mini dresses and slips that one wears under them, so I’m not quite sure what you mean.
But if you mean “midi over slip”, then that is the inverse case from what I am suggesting. Midi over slip (and slip could be any tcpip substrate, such as ethernet) has midi messages as the payload, carried via tcpip.
I’m talking about using midi messages to carry tcpip payloads. You can absolutely do it, but it isn’t really what the protocol is designed for.
Comment by jacquesm 7 hours ago
And what google turns up when you enter those exact three words in a row is really none of my business.
Comment by compiler-guy 5 hours ago
I suppose someone somewhere has done it (and I have always said that you can), but my best internet searches with a wide variety of terms don't show any old tutorials or products that explain how. Nor can I find anything else that uses MIDI to send tcpip packets over the MIDI connection. Not even a mention.
My Google-fu may be totally weak, but whatever.
I freshly, happily and totally concede that people have in the past used MIDI to send SLIP packets, and it is well understood how. Great. You are totally correct.
But all of this just proves the original point. It either precedes anything on the internet today, or is so obscure that no search engine can find it. Either way, if no one uses it or even bothers to explain how, I think it is pretty fair to conclude that it is rather unergonomic, and hacky, and doesn't provide all the features one really wants in a network connection.
Comment by jacquesm 3 hours ago
Comment by bigstrat2003 1 hour ago
Comment by saghm 18 hours ago
Comment by LukeShu 16 hours ago
Comment by keyle 19 hours ago
I'd be very interested if the author could provide a post with a more in depth view of the passes, as suggested!
Comment by petcat 19 hours ago
Yes, please!
Comment by grokx 17 hours ago
It seems that the terminology as evolved, as we speak more broadly of frontends and backends.
So, I'm wondering if Bison and Flex (or equivalent tools) are still in use by the modern compilers? Or are they built directly in GCC, LLVM, ...?
Comment by eslaught 16 hours ago
There was some research on parsing C++ with GLR but I don't think it ever made it into production compilers.
Other, more sane languages with unambiguous grammars may still choose to hand-write their parsers for all the reasons mentioned in the sibling comments. However, I would note that, even when using a parsing library, almost every compiler in existence will use its own AST, and not reuse the parse tree generated by the parser library. That's something you would only ever do in a compiler class.
Also I wouldn't say that frontend/backend is an evolution of previous terminology, it's just that parsing is not considered an "interesting" problem by most of the community so the focus has moved elsewhere (from the AST design through optimization and code generation).
Comment by nextaccountic 13 hours ago
Personally I love the (Rust) combo of logos for lexing, chumsky for parsing, and ariadne for error reporting. Chumsky has options for error recovery and good performance, ariadne is gorgeous (there is another alternative for Rust, miette, both are good).
The only thing chumsky is lacking is incremental parsing. There is a chumsky-inspired library for incremental parsing called incpa though
Comment by estebank 12 hours ago
Comment by ajb 13 hours ago
Comment by fithisux 16 hours ago
Comment by brooke2k 17 hours ago
Comment by afdbcreid 14 hours ago
AFAIK the reason is solely error messages: the customization available with handwritten parsers is just way better for the user.
Comment by muvlon 10 hours ago
https://github.com/NixOS/nix/blob/master/src/libexpr/parser....
https://github.com/NixOS/nix/blob/master/src/libexpr/lexer.l
Comment by nullpoint420 1 hour ago
Comment by sanxiyn 9 hours ago
Comment by gpderetta 17 hours ago
Comment by jojomodding 14 hours ago
The hard part about compiling Rust is not really parsing, it's the type system including parts like borrow checking, generics, trait solving (which is turing-complete itself), name resolution, drop checking, and of course all of these features interact in fun and often surprising ways. Also macros. Also all the "magic" types in the StdLib that require special compiler support.
This is why e.g. `rustc` has several different intermediate representations. You no longer have "the" AST, you have token trees, HIR, THIR, and MIR, and then that's lowered to LLVM or Cranelift or libgccjit. Each stage has important parts of the type system happen.
Comment by pklausler 17 hours ago
Comment by astrange 10 hours ago
In particular, it makes parsing everything look like a huge difficult problem. This is my main problem with the Dragon Book.
In practice everyone uses hacky informal recursive-descent parsers because they're the only way to get good error messages.
Comment by quamserena 17 hours ago
Most roll their own for three reasons: performance, context, and error handling. Bison/Menhir et al. are easy to write a grammar and get started with, but in exchange you get less flexibility overall. It becomes difficult to handle context-sensitive parts, do error recovery, and give the user meaningful errors that describe exactly what’s wrong. Usually if there’s a small syntax error we want to try to tell the user how to fix it instead of just producing “Syntax error”, and that requires being able to fix the input and keep parsing.
Menhir has a new mode where the parser is driven externally; this allows your code to drive the entire thing, which requires a lot more machinery than fire-and-forget but also affords you more flexibility.
Comment by wrs 16 hours ago
Comment by peterfirefly 9 hours ago
The rest of the f*cking owl is the interesting part.
Comment by umanwizard 16 hours ago
In typical modern compilers "frontend" is basically everything involving analyzing the source language and producing a compiler-internal IR, so lexing, parsing, semantic analysis and type checking, etc. And "backend" means everything involving producing machine code from the IR, so optimization and instruction selection.
In the context of Rust, rustc is the frontend (and it is already a very big and complicated Rust program, much more complicated than just a Rust lexer/parser would be), and then LLVM (typically bundled with rustc though some distros package them separately) is the backend (and is another very big and complicated C++ program).
Comment by MerrimanInd 10 hours ago
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Comment by pjmlp 1 hour ago
As did all the UNIXes that used to rule before companies started sponsoring Linux kernel development, and were quite happily taking BSD code into them, alongside UNIX System V original code.
Comment by chuckadams 14 hours ago
Comment by pjmlp 19 hours ago
GCC approach is on purpose, plus even if they wanted to change, who would take the effort to make existing C, C++, Objective-C, Objective-C++, Fortran, Modula-2, Algol 68, Ada, D, and Go frontends adopt the new architecture?
Even clang with all the LLVM modularization is going to take a couple of years to move from plain LLVM IR into MLIR dialect for C based languages, https://github.com/llvm/clangir
Comment by ayende 19 hours ago
Comment by colejohnson66 19 hours ago
The idea is that you should link the front and back ends, to prevent out-of-process GPL runarounds. But because of that, the mingling of the front and back ends ended up winning out over attempts to stay modular.
[0]: https://lists.gnu.org/archive/html/emacs-devel/2015-02/msg00...
[1]: https://lists.gnu.org/archive/html/emacs-devel/2015-01/msg00...
Comment by phkahler 19 hours ago
Valid points, but also the reason people wanting to create a more modular compiler created LLVM under a different license - the ultimate GPL runaround. OTOH now we have two big and useful compilers!
Comment by Croak 18 hours ago
Comment by Y_Y 16 hours ago
If it's free software then I can modify and use it as I please. What's limited is redistributing the modified code (and offering a service to users over a network for Afferro).
https://www.gnu.org/philosophy/free-sw.en.html#fs-definition
Comment by giancarlostoro 19 hours ago
If you're going to make it hard for anyone anywhere to integrate with your open source tooling for fear of commercial projects abusing them and not ever sharing their changes, why even use the GPL license?
Comment by dhosek 17 hours ago
Comment by colechristensen 19 hours ago
--- From the post:
I let this drop back in March -- please forgive me.
> Maybe that's the issue for GCC, but for Emacs the issue is to get detailed
> info out of GCC, which is a different problem. My understanding is that
> you're opposed to GCC providing this useful info because that info would
> need to be complete enough to be usable as input to a proprietary
> compiler backend.
My hope is that we can work out a kind of "detailed output" that is
enough for what Emacs wants, but not enough for misuse of GCC front ends.I don't want to discuss the details on the list, because I think that would mean 50 messages of misunderstanding and tangents for each message that makes progress. Instead, is there anyone here who would like to work on this in detail?
Comment by bigfishrunning 18 hours ago
Comment by tovej 16 hours ago
Comment by colechristensen 6 hours ago
If the FSF is the sole copyright owner they're free to relicense it however they please, if no one else has any controlling interest of the copyright, the GPL doesn't restrict you from relicensing something you're the sole owner of (and it's doubtful there's a legal mechanism to give away rights to something you continue to own)
Again, the FSF under Stallman isn't about freedom it's about control.
Comment by wahern 19 hours ago
Comment by torginus 18 hours ago
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Comment by bigstrat2003 17 hours ago
Comment by LeFantome 11 hours ago
I happen to believe that barriers to collaboration results in less software for everybody. I look at Clang and GCC and come away thinking that Clang is the better model because it results in more innovation and more software that I can enjoy. Others wonder why I am so naive and say that collaborating on Clang is only for corporate shills and apologists.
You can have whatever opinion you want. I do not care about the politics. I just want more Open Source software. I mean, so do the others guys I imagine but they don’t always seem to fact check their theories. We disagree about which model results in more software I can use.
Comment by 1718627440 11 hours ago
I just think, that:
> I happen to believe that barriers to collaboration results in less software for everybody.
is not a bad thing. There is absolutely no lack of supply for software. The "market" is flooded with software and most of it is shit. https://en.wikipedia.org/wiki/Sturgeon%27s_law
Comment by LeFantome 11 hours ago
I am not as much on the bandwagon for “there is no lack of supply for software”.
I think more software is good and the more software there is, the more good software there will be. At least, big picture.
I am ok with there being a lot of bad software I do not use just like I am ok with companies building products with Open Source. I just want more software I can use. And, if I create Open Source myself, I just want it to get used.
Comment by Analemma_ 16 hours ago
Stallman's insistence that gcc needed to be deliberately made worse to keep evil things from happening ran completely counter to his own supposed raison d'etre. Which you could maybe defend if it had actually worked, but it didn't: it just made everyone pack up and leave for LLVM instead, which easily could've been predicted and reduced gcc's leverage over the software ecosystem. So it was user-hostile, anti-freedom behavior for no benefit.
Comment by kelnos 2 hours ago
It did work, though, for 15 years or so. Maybe that was or wasn't enough to be worth it, I don't know.
Comment by 1718627440 11 hours ago
Yes?
> completely counter to his own supposed raison d'etre
I can't follow your argument. You said yourself, that his point is the freedom of the *end user*, not the compiler vendor. He has no leverage on the random middle man between him and the end user other than adjusting his release conditions (aka. license).
Comment by Analemma_ 11 hours ago
Whatever his motivations were, I don't see a practical difference between "making the code deliberately bad to prevent a user from modifying it" and something like Tivoization enforced by code signing. Either way, I as a gcc user can't modify the code if I find it unfit for purpose.
Comment by pessimizer 15 hours ago
Comment by pessimizer 15 hours ago
Comment by demurgos 19 hours ago
I am not familiar enough with gcc to know how it impacts out-of-tree free projects or internal development.
The decision was taken a long time ago, it may be worth revisiting it.
Comment by janc_ 11 hours ago
Comment by bfjjejskdjd 18 hours ago
Comment by 1718627440 18 hours ago
Comment by lionkor 18 hours ago
Comment by throwaway17_17 17 hours ago
That said, if Rust is going to continue entrenching itself in the open source software that is widely in use, it should at least be able to be compiled with by the mainline GPL compiler used and utilized by the open source community. Permissive licenses are useful and appreciated in some context, but the GPL’d character of the Linux stack’s core is worth fighting to hold onto.
It’s not Rust in open source I have a problem with, it is Rust being added to existing software that I use that I don’t want. A piece of software, open source, written in Rust is equivalent to proprietary software from my perspective. I’ll use it, but I will always prefer software I can control/edit/hack on as the key portions of my stack.
Comment by danudey 16 hours ago
This is how I feel about C/C++; I find Rust a lot easier to reason about, modify, and test, so I'm always happy to see that something I'm interested in is written in Rust (or, to a far lesser extent, golang).
> So for me the less entrenched Rust remains the more ability I keep to work on the software I use.
For me, the more entrenched Rust becomes the more ability I gain to work on the software I use.
> if Rust is going to continue entrenching itself in the open source software that is widely in use, it should at least be able to be compiled with by the mainline GPL compiler used and utilized by the open source community
I don't see why this ideological point should have any impact on whether a language is used or not. Clang/LLVM are also open-source, and I see no reason why GCC is better for these purposes than those. Unless you somehow think that using Clang/LLVM could lead to Rust becoming closed-source (or requiring closed-source tools), which is almost impossible to imagine, the benefits of using LLVM outweigh the drawbacks dramatically.
> A piece of software, open source, written in Rust is equivalent to proprietary software from my perspective.
This just sounds like 'not invented here syndrome'. Your refusal to learn new things does not reflect badly on Rust as a technology or on projects adopting it, it reflects on you. If you don't want to learn new things then that's fine, but don't portray your refusal to learn it as being somehow a negative for Rust.
> I will always prefer software I can control/edit/hack on as the key portions of my stack
You can control/edit/hack on Rust code, you just don't want to.
To be blunt, you're coming across as an old fogey who's set in his ways and doesn't want to learn anything new and doesn't want anything to change. "Everything was fine in my day, why is there all this new fangled stuff?" That's all fine, of course, you don't need to change or learn new things, but I don't understand the mindset of someone who wouldn't want to.
Comment by pessimizer 15 hours ago
> This is how I feel about C/C++; I find Rust a lot easier to reason about, modify, and test, so I'm always happy to see that something I'm interested in is written in Rust (or, to a far lesser extent, golang).
You have to do better than "NO U" on this. The comparison to C/C++ is silly, because there is no way you're going to avoid C/C++ being woven throughout your entire existence for decades to come.
> I don't see why this ideological point should have any impact on whether a language is used or not. Clang/LLVM are also open-source, and I see no reason why GCC is better for these purposes than those.
I hope you don't expect people to debate about your sight and your imagination. You know why people choose the GPL, and you know why people are repulsed by the GPL. Playing dumb is disrespectful.
> don't portray your refusal to learn it as being somehow a negative for Rust.
But your sight, however, we should be discussing?
edit: I really, really like Rust, and I find it annoying that the clearest, most respectful arguments in this little subthread are from the people who just don't like Rust. The most annoying thing is that when they admit that they just don't like it, they're criticized for not making up reasons not to like it. They made it very clear that their main objection to its inclusion in Linux is licensing and integration issues, not taste. The response is name calling. I'm surprised they weren't flagkilled.
Comment by keybored 11 hours ago
Keywords right there. People who don’t-like-Rust are the most coddled anti-PL group. To the extent that they can just say: I really need to speak my mind here that I just don’t like it. End of story.
I don’t think anyone else feels entitled to complain about exactly nothing. I complain about languages. In the appropriate context. When it is relevant or germane to the topic.
A “genius” Rust program running on a supercomputer solving cancer would either get a golf-clap (“I don’t like Rust, but”) or cries that this means that the contagion is irreversibly spreading to their local supercomputer cluster.
One thing is people who work on projects where they would have to be burdened by at least (even if they don’t write it themselves) building Rust. That’s practical complaining, if that makes sense. Here people are whining about it entrenching itself in muh OSS.
Comment by throwaway17_17 10 hours ago
Comment by pdimitar 16 hours ago
You started your comment with "I don't like the language". I can't find any technical or even legal-like argumentation (there is zero legal encumbering for using Rust AFAIK).
Your entire comment is more or less "I dislike Rust".
Question to you: what is the ideal imagined outcome of your comment? Do you believe that the Rust community will collectively disband and apologize for rubbing you the wrong way? Do you expect the Linux kernel to undo their decision to stop flagging Rust as an experiment in its code base?
Genuine question: imagine you had all the power to change something here; what would you change right away? And, much more interestingly: why?
If you respond, can we stick to technical argumentation? "I don't like X" is not informative for any future reader. Maybe expand on your multiple levels of disagreement with Rust?
Comment by throwaway17_17 10 hours ago
1) I had no ideal imagined outcome to writing that comment. The parent asked what the GP meant by not liking Rust but that at least Rust could be compiled by gcc. I was just explaining why it may be preferable to someone that does not use (or in this case "like" Rust) to see it able to be compiled by a GPL piece of software that has been a part of the Linux core for almost all of Linux's existence. As to the rest of that question, of course, I don't think that anyone using/enjoying/designing/supporting Rust in any way would be convinced by anything I think or say (I'm just some guy on HN).
2) If I had the power to change what? The issue with Rust not being able to compile using gcc or more broadly concerning change things regarding Rust? I don't think a list of changes I'd make to Rust is what you wanted, so I'll assume you meant regarding compiling Rust via gcc. If I had the power to change Rust from being only compiled using rustc and moved to primarily gcc based I would. And the why is not particularly interesting, I will always prefer actions and decisions that take mind and market share away from anything that can be used to advance the interest of multi-national conglomerate corporations via permissive licensing of the core technologies of computing.
I know that is not a technical argument, but it is the reason I'd make the change. I will assert that such a reason is absolutely valid, but I don't take disagreement with my position to be a character flaw in someone.
Comment by pdimitar 10 hours ago
I too am just one guy on HN but when I go to certain threads, I do expect no emotional and preference comments because I want to fill up my blind spots and emerge better educated. Obviously that does not mandate anything from you but since we are expressing preferences, that's mine.
RE: the rest, I am trying to understand your POV but can't. Is your issue with the difference between GPL and whatever Rust is licensed under?
That I could somewhat understand. But your rather emotionally loaded language against Rust itself I simply cannot and will not take seriously. Apparently Rust has an unique talent to tick people off on HN would be my tongue-in-cheek conclusion here because it has been years since I saw what we might call a "zealot fiercely arguing in favor of Rust" here, so the reason should be somewhere else.
Feel free to elaborate on that, though I am fairly sure such a discussion would not go anywhere. Emotion resents reason; emotion just wants to express itself.
But I do get weirded out how many people treat Rust like it's coming to eat their kids and puppies.
Comment by throwaway17_17 9 hours ago
As to your, somewhat rhetorical seeming, question about my issue pertaining to GPL vs ‘whatever Rust is licensed under”. Yes I have an issue regarding licensing. But it pertains primarily to LLVM in this instance. LLVM is permissive licensed vs gcc being GPL. I am firmly opposed to the core executables/artifacts of computational technology (compilers, OS, drivers, ISAs, hardware interface standards) being anything other than copyleft. However, I would be willing to adapt to a more restrictive “open source” that allowed for limiting use of software for the betterment of the whole.
If I could immediately change anything, it would be to see LLVM stripped of its importance and dominance and put all those resources into copyleft software forcing profligate consumers of technical advancement to ‘pay it forward’ if they want the product of our collective minds and effort.
Comment by pdimitar 9 hours ago
What's your preference about copyleft about? Is it that you don't want corporations to keep leeching off of open source? But they do that already! And of course will do their best to hide it. What some license somewhere says bears nearly zero significance. Even if you catch them red-handed and can prove it in court (a very unlikely and rare combination) it would still take like 5 years for any conclusion to be reached... and it will likely end with financial settlement and no real negative outcome for the corporation. So that battle has IMO been lost already.
But if you have something else in mind, I am actually interested to hear it. I am rather cynical and not very well informed on licenses. To me they simply have no real teeth and that's why I lost interest in knowing more. Still, not taking an interest in something innately means that one is having a rather big blind spot. I recognize that about myself.
--
RE: Rust / Scala etc., thanks, that puts things into better context. But I still don't get why would you be against a language becoming more pervasive. Are you maybe convinced that the PL is only driven by hype and not merit? Or is it some other reservation / protest / consideration?
Comment by throwaway17_17 8 hours ago
To start, for Rust to a larger degree than Scala, I certainly don’t think the language lacks merit. I am convinced the hype around Rust and its momentum in conversation did it a tremendous favor as it was coming up to 1.0 and as it went through ~2021. I do have some serious technical issues with choices Rust as a programming language made, but while I believe a change in direction for Rust would be beneficial, the ecosystem advancement and entrenchment of Rust makes it basically a non-starter as of 2025.
From a philosophical perspective (and I know I am an extreme outlier) I think, in the large, society and industry would be better served by having no ‘large’ programming languages. If every company was use to and had to invent at a minimum their own dialect of a broadly defined language types and then train employees to function within their language environment I would be thrilled.
The above would do a considerable amount to stop corporations from treating programmer like replaceable/disposable cogs in a machine. It would also end the ability of conglomerates from stealing the work of others wholesale as there wouldn’t be a single JavaScript, but a fleet of JavaScript suited to developing different classes of frontends. And hopefully, if a language was never as widespread as C, then hardware manufacturers would not be catering ISAs to fit the mythical ‘C Programmer’s’ model of how a computer works, thereby allowing for actually useful low level languages to be developed to fit the evolving features of what hardware actually does. (This point is basically a rip off of Chisnall’s “C is not a low level Language” article)
The lack of widely popular languages would also prevent the situation I see with Rust, which is really a first to market and good enough problem. I could go on at length about Rust’s commitment to the ownership semantics and its coupling with single mut XOR multi immut, but where it really hurts for me is that Rust’s pervasiveness prevents moving to a better option in the space due to moneyed interest and cultural buyin.
However, neither of the above are meant to fault Rust’s use for software engineering. It seems to be a good tool for many and is seeing acceptance at a rate that seems miraculous. My dislike of the language may result from fundamental disagreements about programming, type theory, and language “culture” but I have never said people should not build new software using Rust (although without using Cargo, info had a say).
—-
As to licensing, I agree with your general thought that I am basically tilting at windmills with my stance toward non-copyleft licensing. I think you are accurately describing the current state of affairs as well. However, a more vicious form of licensing, source broadcasting, literal viral attestation code, alteration aware self destructs, etc. I routinely refuse to give legal advice on licensing because it is such an untested and nearly unenforceable area of contract law, but I can’t help but feel there is some way to legally (or at least dangerously) put some teeth into software that is being exploited.
Comment by lionkor 17 hours ago
Fair enough, but what are those disagreements? I was fully in the camp of not liking it, just because it was shoved down every projects throat. I used it, it turns out its fantastic once you get used to the syntax, and it replaced almost all other languages for me.
I just want to know if there are any actual pain points beyond syntax preference.
Edit: I partially agree with the compiler argument, but it's open source, and one of the main reasons the language is so fantastic IS the compiler, so I can stomach installing rustc and cargo.
Comment by coldpie 16 hours ago
Unlike a project's license, this situation is entirely in your control. Rust is just a programming language like any other. It's pretty trivial to pick up any programming language well enough to be productive in a couple hours. If you need to hack on a project, you go learn whatever environment it uses, accomplish what you need to do, and move on. I've done this with Python, Bash, CMake, C++, JavaScript, CSS, ASM, Perl, weird domain-specific languages, the list goes on. It's fine to like some languages more than others (I'd be thrilled if C++ vanished from the universe), but please drop the drama queen stuff. You look really silly.
Comment by IshKebab 15 hours ago
Comment by throwaway17_17 14 hours ago
But, that doesn’t have any bearing on my lack of desire to learn Rust. Several other comments basically demand I justify that dislike, and I may reply, but there is nothing wrong with not liking a language for personal or professional use. I have not taken any action to block Rust’s adoption in projects I use nor do I think I would succeed if I did try. I have occasionally bemoaned the inclusion of Rust in projects I use on forums, but even that isn’t taken well (my original comment as an example).
Comment by JoshTriplett 12 hours ago
Comment by throwaway17_17 10 hours ago
I have relatively strong opinions about quite a few areas that Rust, as a language and accompanying programming & tooling philosophy touch on, so I'll just do a few as examples:
1) I am strongly adverse to package managers (I didn't pick this example to get a rise out of you in particular) and their usage by programming languages. I am hostile toward the trend toward more and more dependencies in a given executable, which is only made worse by the industry adoption of languages that support and promote the "find a crate/get from NPM" attitude toward incorporation of dependencies. I don't know if there is evidence of a exponential explosion of transitive dependency in languages relying and building on a package manager ecosystem, but I wouldn't be surprised if it worked toward that point. I know that one does not have to use Cargo and the crate ecosystem, but it is a huge point of pride for the community and is THE idiomatic way to handle dependencies in Rust.
2) I have strong philosophical disagreements with ad-hoc polymorphism in general and with Rust's choice of pervasive reliance on its trait system all through the standard library and all examples of idiomatic code. At this point in development I don't even think there is a means to remove the ad-hoc polymorphism from Rust's implementation as a language. This point in particular I can not see any active Rust user being seen as an improvement of the language. Further, and although Rust does not have a definition of the language or a formalization of the type theory used by the language, I can not see a world where Rust adopts Haskell's position on the typeclass system being a convenient syntax sugar for a non-primitive and more explicit semantic form.
3) I am both practically and philosophically opposed to the usage/presence of 'ownership semantics' as a core part of the semantics of a programming language. Note, that I don't oppose the encoding of the commonly used meaning of 'ownership' at the type level via expressive types, as it can be an accurate description of the relationship between various data in a program. I do object to 'ownership' being the foundational semantic understanding of all programs and data used therein. There is a chance that Rust could incorporate a sophisticated type theory in a future release that relegates the current imposition of universal ownership semantics into a constrained area and allows for alternative semantics to be used in appropriate places, but I think it is nearly impossible to do and maintain validity for any prior programs.
So, do any of those three example look particularly appealing? I know you, only by reputation and seeing previous comments on HN, and know you are fairly involved in the development of Rust from several directions. Can you see Rust becoming a language with very limited ad-hoc polymorphism, a strong break away from the ownership semantics used today, and a language that does not place a package manager in a place of importance for idiomatic development?
Of those three examples the only one I can see anything being said that would alleviate my dislike is to just not use Cargo and build everything from scratch or find and download tarballs, which I would probably do and not complain if I had to use Rust. Thanks for your response being not particularly aggressive, I appreciate any time you gave to read this wall of text.
Comment by aw1621107 8 hours ago
What disagreements are those, if you don't mind typing more? PL design is something I'm interested in but not particularly experienced with so more perspectives are always nice to hear.
> I can not see a world where Rust adopts Haskell's position on the typeclass system being a convenient syntax sugar for a non-primitive and more explicit semantic form.
As someone who isn't familiar with Haskell, do you mind elaborating on Haskell's syntax sugar and what it reduces to?
Comment by throwaway17_17 7 hours ago
Additionally, and more relevant to Programming Language Theory, the entanglement between ad-hoc polymorphism implementations and the detention of a programming language are a huge mistake from my perspective. This is where Haskell becomes relevant, because although there are some differences (implicit self, orphan issues, etc) between Rust traits and Haskell’s typeclasses, they are an extremely similar mechanism for achieving ad-hoc polymorphism. At this point in its development, and due to the pervasiveness of usage throughout the stdlib, I see it as almost certain that Rust will attempt to kludge traits into a formal definition of its type theory and language definition making any attempts at coexisting with other language in a single application more difficult. Comparably, in Haskell, typeclasses are merely syntactic sugar allowing for a better developer experience using ad-hoc polymorphism. Specifically, Haskell, the language as defined, achieves ad-hoc polymorphism by passing a dictionary parameter to functions using overloaded function names. This is done using the standard terms in Haskell and has a clear denotaional semantics for such terms. Rust usage of traits is talked about and reasoned about as a more primitive part of the language, not just a pretty piece of sugar with a more basic existence in the formally defined core of a programming language.
If ad-hoc polymorphism is something a language designer wants to incorporate into the usage of a language, my position is that defining a typeclass style sugar over a clearly defined set of terms in the core, formally defined language would be at least a method of prohibiting issues with the resolution, definition, and various methods of implementation of ad-hoc polymorphism polluting the syntax and semantics of the language itself. But the above requires a firm definitional boundary between what is the language and what is syntactic sugar to be built into the definition of the language and built into the compiler infrastructure.
A more out of band way to achieve ad-hoc polymorphism would be to have a pre-processor that is a part of the language distribution and maintained by the language designer/org that does the resolution/solving of the ad-hoc polymorphism and then presents the compiler with source text with no overloading.
There are also type theoretic solutions to ad-hoc polymorphism l, but that’s a little outside the scope (even if it my personal solution to having and limiting ad-hoc polymorphism in a language).
Comment by aw1621107 4 hours ago
Just a few additional questions/comments:
> Specifically, Haskell, the language as defined, achieves ad-hoc polymorphism by passing a dictionary parameter to functions using overloaded function names. This is done using the standard terms in Haskell and has a clear denotaional semantics for such terms. Rust usage of traits is talked about and reasoned about as a more primitive part of the language, not just a pretty piece of sugar with a more basic existence in the formally defined core of a programming language.
Would it be accurate to say that Swift's non-monomorphized generics are more along the lines of the Haskell approach you prefer (i.e., single function implementation with a separate parameter for additional type info)?
And a bit more hand-wavey, but IIRC Rust's generics were defined in such a way that monomorphization is technically an implementation detail; in other words, I want to say a Haskell-like approach isn't strictly ruled out. I'd take that with a large grain of salt, though.
> If ad-hoc polymorphism is something a language designer wants to incorporate into the usage of a language, my position is that defining a typeclass style sugar over a clearly defined set of terms in the core, formally defined language would be at least a method of prohibiting issues with the resolution, definition, and various methods of implementation of ad-hoc polymorphism polluting the syntax and semantics of the language itself. But the above requires a firm definitional boundary between what is the language and what is syntactic sugar to be built into the definition of the language and built into the compiler infrastructure.
Might MiniRust [0] be something along the lines of what you would desire? It seems to fit the general idea of a smaller formally-specified "core" language. There's also this bit about traits specificlaly from the readme:
> That translation [from Rust to MiniRust] does a lot of work; for example, traits and pattern matching are basically gone on the level of MiniRust.
Comment by throwaway17_17 3 hours ago
Swift is also good touch point for considering what the compiler does with the actual implementation of ad-hoc polymorphism. Swift is optimizing to monomorphized instances of a generic function give some heuristics about expect performance gains by specializing the function for a given type (Haskell also does this in GHC, but still pays a performance price for using boxed values).
So to answer the question: the part of Haskell’s implementation of typeclasses that I think is the correct method is that it is merely a derived syntactic form that is expanded by the compiler into Haskell’s actual language (its abstract syntax as encoded as ghc-core in GHC in particular). From this perspective Swift doesn’t provide the derived form, it just provides the implementation directly for developers to use omitting the sugar that Haskell provides. I tend towards explicitness as a strong default in language design.
Rust doesn’t have a formal semantics currently, so they could certainly adopt a derived form approach to traits, but I don’t know enough Rust to be able to determine what issues existing thoughts, assumptions, and type theory ‘commitments’ would act as obstacles to such a semantic.
As to MiniRust, Ralf Jung (at ETH Zurich) has done some excellent work, along with some of his students (Max Vistrup’s recent paper on Logics a la Carte is very, very good). MiniRust does attempt to be comparable to Haskell’s GHC-core. So in the sense of being or approaching what I would view as the (excluding type theory based options) correct way to implement ad/hoc polymorphism, yes, to sum: MiniRust as the semantic definition of a derived syntactic form and a compilation phase for ‘expansion’ of the trait macro.
Those explanations aside, my issues with ad-hoc polymorphism do not go away under this implementation, I’m generally opposed to generic functions (especially function name overloading). But I think that if a language is pursuing ad-hoc polymorphism as a feature they should pursue it in a well founded and formal manner.
Comment by IshKebab 2 hours ago
I agree there are significant costs to generics (especially readability), but there are large classes of problems that are a right pain without them. Even Go added them eventually.
Comment by umanwizard 10 hours ago
> I am strongly adverse to package managers
This has nothing to do with Rust the language, other than the incidental fact that cargo happens to be bundled with Rust. There are no cargo-specific concepts whatsoever in the Rust language, just like there are no Cmake-specific concepts in C++. I know you alluded to this in your post; I just want to make sure it's crystal clear to everyone reading.
Consequently, people can, and do, use Rust without Cargo. That is obviously not what the majority does, because cargo is so easy to use with rust, but it is certainly possible both in theory and in practice.
If it's a "point of pride in the community" and "idiomatic" -- who cares? Rust is a general-purpose systems programming language. You can use it however you want, without listening to what people on Twitter think about it.
This particular complaint strikes me as social/cultural rather than technical -- "people who like Rust do something I find annoying, therefore I must conclude that they're not of my tribe, and reject rust". That is very understandable human nature, but not logically justified.
As for your other two complaints, you are correct that they are fundamental to the language and will never change for at least as long as the language is called "rust".
But since these complaints are totally subjective (a reasonable person might like or dislike them), it doesn't really seem fair to bitch about a language existing and becoming popular that has these properties.
For example, I complain about Go because I think it has actual defects that make it harder to use for almost any competent programmer. I also don't like Python, but I think the tradeoffs it chose to make are at least intelligible and some people prefer the Python style, so it would make no sense for me to complain that other people use it in their projects.
Comment by lionkor 57 minutes ago
Generate a random number.
Comment by throwaway17_17 9 hours ago
Regarding that it might not be fair to ‘bitch’ about a language ‘existing and becoming popular’ over subjective disagreements: as I’ve said in other comments, and other places, I do not have any issue with developers using or enjoying Rust in their work, I’m all for people making software that is more economical in its usage of hardware and associated/entailed resources. I just don’t want Rust to be imported into existing codebases in other languages (and certainly not into software where it adds a non-copyleft dependency to a GPL’d core).
Comment by JoshTriplett 12 hours ago
Comment by keybored 11 hours ago
This is an irrelevant and disingenious hacker jab (oh look, they’re not a “real hacker”).
Comment by umanwizard 17 hours ago
Comment by pessimizer 15 hours ago
The language itself I find wonderful, and I suspect that it will get significantly better. Being GPL-hostile, centralized without proper namespacing, and having a Microsoft dependency through Github registration is aggravating. When it all goes bad, all the people silencing everyone complaining about it will play dumb.
If there's anything I would want rewritten in something like Rust, it would be an OS kernel.
Comment by JoshTriplett 12 hours ago
Never attribute to malice that which can be adequately explained by apathy. We have, unfortunately, reached a point where most people writing new software default to permissive and don't sufficiently care about copyleft. I wish we hadn't, but we have. This is not unique to Rust.
Ironically, we're better off when existing projects migrate to Rust, because they'll keep their licenses, while rewrites do what most new software does, and default to permissive.
Personally, I'm happy every time I see a new crate using the GPL.
> GPL-hostile
Rust is not GPL-hostile. LLVM was the available tool that spawned a renaissance of new languages; GCC wasn't. The compiler uses a permissive license; I personally wish it were GPL, but it isn't. But there's nothing at all wrong with writing GPLed software in Rust, and people do.
> having a Microsoft dependency through Github registration is aggravating
This one bugs a lot of us, and it is being worked on.
Comment by pjmlp 1 hour ago
Many forget that Microsoft went from "FOSS is bad", to now having their fingers across many key FOSS projects.
They are naturally not the only ones, a developer got to eat, and big tech gladly pays the bills when it fits their purposes.
Comment by timeon 13 hours ago
Not sure if it is particularly hostile. There are several GPL crates like Slint.
> Microsoft dependency through Github registration is aggravating
This one is concerning.
Comment by notepad0x90 12 hours ago