Google's Rust Style Guide

Not trying to rain on someone's parade but, the only reason why would care about style guides nowadays is to feed them to our model of choice and let it do what it's supposed to be doing. So it's not like I am willing to read through this and think to myself "I cannot wait to pick up some new ways of doing things". I'm the general to my agentic army now. I guess you would code manually every now and then for your own enjoyment but at that point do you care about style guides written for scale?

• gatlin · 2 hours ago

  Seems very much like your goal was to rain on a parade.

• u1hcw9nx · 2 hours ago

  Not trying to rain on someone's parade, but the only reason I would care about HN comments nowadays is to feed them to my model of choice and let it generate the contrarian hot takes it's supposed to be generating. So it's not like I am willing to read through this thread and think to myself "I cannot wait to pick up some new ways of complaining about documentation." I'm the Editor-in-Chief to my synthetic pundit army now. I guess you would type out a comment manually every now and then for your own enjoyment, but at that point do you really care about comments at scale? --- EDIT (above is a joke) It's very important that every time you find something that is of no use to you, you write a comment explaining that this link is of no interest to you, discouraging people from things you have no interest in. Monoculture for all!

• anonymous908213 · 2 hours ago

  > I'm the general to my agentic army now. What have you produced with your agentic army? Would you like to share with the class?

  • bigfishrunning · 2 hours ago

    my guess is a lot of heat, some water vapor....

  • solyin · 1 hour ago

    Why would they when the class is full of dropouts who, generously, have a 0 percent chance of going "hey, y'know what, that's actually kinda cool! I'm going to change my mind about LLMs being useless" and a 100% chance of going "ur project is total shit and you should feel bad".

    • nvme0n1p1 · 1 hour ago

      The people you call "dropouts" have written 100% of the software that people actually use and actually keeps the real world running, so maybe you shouldn't write them off.

• monocasa · 2 hours ago

  The point of style guides is to optimize for readability despite a cognitively diverse workforce coding in the same repos. I would think they're probably even more meaningful in an agentic world. Shitty generals can't review meaningfully review the work of their troops. On top of that all, I just enjoy programming itself. It's less and less of the meat of a software job over time, but I was coding before I got paid for it, and I'll probably keep coding well after I can get paid for it.

  • mkagenius · 1 hour ago

    > Shitty generals can't review meaningfully review the work of their troops. Except that reviewing has become just asking your agent what that piece of code does in english. Reading code has a bit of cognitive load, that we will probably drop it in coming years

• smoe · 2 hours ago

  First paragraph: “includes guidance on API and implementation design” It seems to me that if the intent is not just to produce code but also to operate it, having the different pieces behave in a similar, predictable way is kind of nice. Whether the software is written by AI or humans.

• nimih · 2 hours ago

  I'm not sure I really agree with your main point (I think it's probably still important for LLM-generated code to be generally human-understandable, at least if you care about long-term maintainability), but setting that aside to answer this question: > I guess you would code manually every now and then for your own enjoyment but at that point do you care about style guides written for scale? I think they're still quite valuable in that case, for a couple reasons: - When learning a new language (which happens much more frequently when writing code "for pleasure," as it were), "written for scale" guidelines still translate pretty well to "written for oneself" IME. At the very least, they tell you what to expect in code you read, and give you a reasonable starting point as you develop your own taste and stylistic preferences. - I've noticed some open source projects beginning to institute anti-AI contribution guidelines, and such projects still benefit from codified style guides. Google obviously doesn't fall under this category themselves, but in other language ecosystems, their style guides tend to find use in OSS projects.

• petersellers · 2 hours ago

  Are you saying that you don't ever look at the code once it's been generated?

  • bigstrat2003 · 1 hour ago

    AI bros think you can never look at code and make good software. They're wrong, of course, but they refuse to listen and will probably never listen until the shoddy quality of their work becomes too great to paper over.

• yodsanklai · 2 hours ago

  This is what we do in my company, give the guidelines to the model. Unfortunately, the model isn't always following them and it's impossible to enforce them manually. There's too much code to review, the code is generally low quality, and is more often than not auto-approved by AI. Unless you're working on your own project on which you have full control, or you have a strong authority figure in your company who cares about that, it's a lost battle. It's sad for anyone who love their craft, but tbh I'm not even sure it matters anymore for most projects.

The enum-over-bool rule is the one I'd keep even solo, saved me a reversed flag in a cert validator once.

• sebastianconcpt · 2 hours ago

  This is a sub-case of the general one that is narrowing the interpretation of things. A big infinite amount of things can be true or false, only one can be a Rust variant.

At this point, is anybody writing new C or C++? It seems like they are sunset languages even at the big corps.

• icase · 2 hours ago

  grownups with important jobs write C

  • thomashabets2 · 2 hours ago

    Are you just being snarky, or do you have something more specific to say about something that's choosing C? Considering that it's been 54 years, and we've yet to find any human being, any at all[1], who can write C without UB, I'd say that writing C in 2026 when there's any other option is basically misconduct and a good case could be made that if the code touches money in any way, then it could be a SOX violation too. Writing C today is like still writing Cobol. Yes, if you are adding a new type of savings account to your bank, and the rest is in Cobol, then sure write it in Cobol. Some microcontroller projects may have an ecosystem in C that makes other options harder in practice, but it's still a worthy investment to not use C. There's a reason phone baseband firmwares are moving away from C. [1] No, not even djb, who people like to bring up.

    • dnautics · 1 hour ago

      > who can write C without UB Sel4?

    • anonymous908213 · 1 hour ago

      > Are you just being snarky, They aren't being snarky, they're stating a fact. Rust, rounding to the nearest percent, does not exist. It's a trendy language among the Silicon Valley types that HN draws, but 99.9% of the world runs on C/++, OSes written in C/++, and language VMs implemented in C/++. Maybe some day it will change, but hanging around here too much will give you a very skewed idea of how widely adopted it is.

      • thomashabets2 · 1 hour ago

        Well, "grownups with important jobs write C" can be taken in two ways. Non-snarky, sure. There are MANY people who write C professionally. Not as many as there are Python, Java, JS, or C++ programmers. Depending on the survey, C seems to be neck and neck with PHP. I read the comment the other way, though. The way that says that those other more popular languages are not serious, and NOT for grownups with important jobs. Edit: actually, Jetbrains 2025 survey has C neck and neck with Rust : https://www.jetbrains.com/lp/devecosystem-data-playground/ . Both "below the fold" and less than 10% of Java.

        • anonymous908213 · 1 hour ago

          Python, Java, and JS are all implemented in C/++. C++ is an extension of C. Taken strictly, sure, not everyone is literally writing C. But C powers everything. It is still the systems language of the world, that is the foundation of all of our systems, including both embedded and phone/PC OSes. Then there's a bit of COBOL and Fortran for mainframes, Ada for military hardware, and a whole notta Rust anywhere. Think about what Rust software people actually use. Codex CLI, uv, ripgrep, and what else? That's three pieces of software, all development tools for development nerds. Normal people aren't engaging with any of this stuff. Your metaphorical grandma has never used software written with Rust in her life.

          • thomashabets2 · 1 hour ago

            Cobol powers the world's money and international travel. Not sure how that matters. > Think about what Rust software people actually use More and more Chrome, Google, Android, Cloudflare, Prime Video, and phone basebands, parts of Linux kernel, and many other things. Normal users literally use those all day every day. Are they 100% Rust? Of course not (well, I don't actually know if some phone basebands are, by now. Naturally very closed source). But they're not 100% another-language either. If C disappeared from the world, the world would stop, yes. Same with Cobol. Same with Java. Same with C++. Same with assembly. If I were to guess (completely without basis for my guess) about the number of lines of code that normal users exercise in a normal day (counting each line just once), my bet would be on Java or JS. Would the Java be able to run without the C code? No. But normal users would not be able to do anything if only C was left. And all banks would be gone. And in any case C would not be able to do anything without transistors.

          • dwattttt · 1 hour ago

            Rust is in use in more places than you may expect. Does the hypothetical grandma use Windows' kernel? Android? Firefox? Chrome?

            • anonymous908213 · 1 hour ago

              1% of code in some obscure module that's barely used being written in Rust does not give one claim to those things being written in Rust. Even Firefox is only 10% Rust despite the language being designed by Mozilla, and they abandoned their project to write a new browser engine in Rust.

              • thomashabets2 · 54 minutes ago

                What is your point? I pointed to a jetbrains study, and then there's a stackoverflow survey[1] showing C neck and neck with PHP at 11th place among professional developers. We all know there's lots of important C code out there. I don't see anyone going "RIIR!!!" in this thread. But obviously yes, the 11th place language will have MANY programmers working on it. Not as many as JS by far. But many. In that survey Go is just after PHP. There are also many many Go programmers. We are not yet at risk of running out of C programmers, like the Cobol situation. Nor do I want us to.[2] But what point are you trying to make by so strongly defending C and the comment "grownups with important jobs write C"? [1] https://survey.stackoverflow.co/2025/technology#most-popular... [2] relevant comment: https://news.ycombinator.com/item?id=50187384

                • anonymous908213 · 38 minutes ago

                  The point I am trying to make is that C is a production language and Rust is not a production language, so the original comment is pretty much correct if you take adults with jobs to mean writing software used in production. People use JS, your JS engine is written in C++, running in a browser written in C++, running on an OS written in C/++. Whatever higher-level language you use, it's powered by C/++. Your game engines are written in C/++. Your fucking car is written in C. It's not even an argument about what is better or what people should use or anything like that. It's just acknowledging reality. You're talking about how "writing new C in 2026 is misconduct" like it's a relic of a bygone era when in actuality the world around you is a world written entirely in C with, rounded to a whole percent, literally 0% of the software anyone uses being written in Rust.

              • aero_code · 50 minutes ago

                It's not "some obscure module" that is written in Rust. Just some examples I know of: - Chrome currently uses https://github.com/googlefonts/fontations to implement its font handling, and text is the main thing on most web pages. - Windows' DirectWriteCore for font handling is also now written in Rust. - Firefox's whole CSS engine and GPU 2D rendering engine are written in Rust.

    • clifflocked · 1 hour ago

      > Considering that it's been 54 years, and we've yet to find any human being, any at all[1], who can write C without UB Undefined behavior does not mean that a language is useless. C is quite nice to write as an abstraction over assembly, and I highly recommend writing C code and thinking about (and checking) what assembly it compiles into. Also, it is possible to verify that the types of UB that you are referring to do not occur: see the seL4 project, which provides machine-checked proofs for an OS kernel that no execution can reach a state that is undefined by the language specification.

      • thomashabets2 · 1 hour ago

        > Undefined behavior does not mean that a language is useless. Never said it was useless. But it's pretty damning that literally nobody can write correct code in the language. And my point is that it's been enough time that it can't be seen as a skill issue. > C is quite nice to write as an abstraction over assembly, and I highly recommend writing C code and thinking about (and checking) what assembly it compiles into. Absolutely. I think in order to understand programming you need to be able to write C, and be able to read assembly. C isn't "high level assembly", with the whole discussion about the spec talking about the abstract machine, but one does not need to be a C language lawyer to be a good programmer. But to your point about checking the output: That goes for Rust too, and godbolt.org supports Rust too, for this workflow. So I'm not saying C is useless. But I am saying that if someone were to decide to write their greenfield project in C, then if it plans to have actual users (as opposed to a fun project), then it's basically misconduct. Cf. Steve Gibson writes his software in assembly, still. Because he enjoys it, and his enjoyment is the primary user. I respect that. But I would NEVER hire someone to write whole applications like that in assembly. Or C.

  • mahboi · 10 minutes ago

    Grownups with important jobs use at least a few different languages

• tkz1312 · 2 hours ago

  I've been extracting a lot of verified C from theorem provers recently.

• neutronicus · 2 hours ago

  C++ seems alive and well in the defense space. The big contractors near me have tons of C++ job postings and I don't think I've seen a single one looking for Rust.

  • thomashabets2 · 1 hour ago

    Do you know if the code bases are of the kind where dynamic memory (among many other features) is disallowed?

    • neutronicus · 1 hour ago

      Some of them, probably. From the job postings, many of them seem to be physics simulations of various kinds where (in my experience) memory is allocated on the heap without a second thought. Well, there are second thoughts, but those second thoughts are about performance.

• loeg · 2 hours ago

  Plenty of new C++ going on at my BigCorp employer.

• fasterik · 2 hours ago

  I'm pretty sure most big software projects (Windows, Linux, Chrome, gcc, LLVM, AAA game engines, ...) are still writing a lot of new C and C++. Pretty much everyone in the embedded world is as well. As a solo programmer, I still prefer C and C++. In fact, as I've incorporated LLMs in to my workflow, I've been increasingly drawn toward C and its simplicity. A lot of the QoL features of C++ simply aren't needed when you're writing less code manually.

• skohan · 1 hour ago

  C/C++ is still relevant for HPC, where you want to carefully optimize memory management.

  • vlovich123 · 1 hour ago

    Hate to break it to you but Rust is equally capable of doing all the same memory management optimizations.

    • skohan · 49 minutes ago

      I mean you can, but C/C++ is way more ergonomic for dealing with memory layouts.

      • Philpax · 37 minutes ago

        Is it? How so?

• IshKebab · 1 hour ago

  Yes mine is, because they have a huge amount of C++ already and none of it is publicly accessible so security isn't a concern. (Obviously there are many other reasons to prefer Rust, but that is a big one.)

• npalli · 1 hour ago

  Far from it. Until Rust can read C++ code seamlessly, there will be more code written in C++ than Rust for the foreseeable future. HPC, Finance, AI, Games, Databases, Hardware all continue to be written in C++.

• j1elo · 1 hour ago

  Today I went over a TODO comment from 2007 in a C++ codebase that is still evolving very vividly, year after year. Trust me, for well established projects C++ is there to stay.

• pjmlp · 1 hour ago

  Games, anything that depends on LLVM, GCC, CUDA, SYSCL,.... Ah and Rust's compiler backend dependency on LLVM and in the future GCC as well.

• xedrac · 1 hour ago

  Unfortunately for me, yes. Some companies are very risk adverse and would rather stick with the devil they know. They have no idea what they are sacrificing.

• pornel · 49 minutes ago

  Cloudflare is all in on Rust, it's used everywhere by default, and C++ leftovers are being actively torn down.

no amount of stylistic heterogeneity can make this awful language pleasant

• sebastianconcpt · 2 hours ago

  The good emotions come with the confidence in the engineering quality that it gives you as output (once you overcome the friction, which AI can help you big time to achieve).

Can anyone expand on the chromium specifc guidelines on super tiny crates, particularly no nesting of modules/source files? That feels like the ~2010 era of people saying that functions should be as small as possible. That lead me to reviewing a lot of code where every function was one or two lines and you couldn't actually see what was going on anymore through the layers of unneeded abstraction. I want to give chrome the benefit of the doubt, but that seems really goofy.

• loeg · 2 hours ago

  Maybe one or two line functions are a totally different scale than "all source code files in a crate"? So like, one is problematic in a way the other is not. And the guidance is " prefer small," not " always super tiny." See: "Larger crates are allowed" later on. And also see: "Rationale: Fine-grained library targets are recommended in Chromium due to the massive size of our codebase, non-local effects of adding dependencies in the build graph, and to improve performance of parallel compilation and build caching."

• dnautics · 1 hour ago

  Compilation speed?

• skohan · 1 hour ago

  It might have to do with optimizing compile times. A crate is the unit of compilation, so small crates increase the likelihood that you won't end up recompiling a lot of unrelated code. I guess smaller crates and avoiding nested modules could also help optimize for making the code greppable by coding agents without blowing up context windows.

• evmar · 1 hour ago

  In Cargo-built Rust, a crate is costly in terms of abstraction because it needs its own directory, Cargo.toml, src/ subdir, etc. In the Google build systems I've worked with in the past (and it looks like Chromium follows) they instead put source files in the same directory mixing languages and with finer-grained libraries as they see fit. Given that a crate is the unit of build parallelization in Rust, there's a benefit to more crates especially when they don't cost much cognitive overhead. You could imagine using crates in the way you'd typically use separate mods in a normal Rust project. I dug around in their code search to find some examples but didn't see much Rust in there, seems still early. I think https://source.chromium.org/chromium/chromium/src/+/main:tes... has ~4 Rust files that end up separate crates though. (One of them defines a proc macro so even in a Cargo built Rust project it would need to be in its own separate crate, I think!)

  • evmar · 1 hour ago

    It looks like there's some macro-based import that does import by path, so crate names are generated: https://source.chromium.org/chromium/chromium/src/+/main:tes...

• i2talics · 1 hour ago

  The granularity of crates shouldn't really impact what kinds of abstractions you build. You can still have as many modules and types as you need, and as big of functions as you need, but its saying you should organize the modules into separate crates instead of one large crate. They even call out the trait coherence rules, saying that you can just make your library bigger instead of forcing a more awkward design in the pursuit of a smaller crate. I think one benefit of small crates is that it gives you more granularity in linking and dependency graphs, which is especially relevant for rebuilds. At a previous job we had a monolithic "utilities" crate, and this caused problems when you tried to depend on it for the IP address utilities but this brought in the radio frequency utilities. When one of these submodules got an update the versioning would excessively propagate downstream to every consumer. If this was organized as small "net-utils" and "rf-utils" crates then maybe it would not have been as much of an issue.

• vvillena · 58 minutes ago

  This being Google, I assume everything goes into a single gigantic monorepo that gets thrown at Blaze. If the unit of compilation is the crate, it makes sense for them to prefer that crates are as small as possible.

• pornel · 34 minutes ago

  You get stricter enforcement of public APIs and dependencies. You can't import anything you haven't declared as a dep, and cycles are impossible. Rustdoc by default shows only your intended public API. OTOH if you have one crate with lots of modules, it's tempting to import anything anywhere and use pub(crate). Rustdoc needs to be configured to show private items if you want to see internal APIs.

  • tcdent · 19 minutes ago

    Exactly. Being able to organize your code in a way that provides distinct responsibilities per crate is just good practice. And then the ability to enforce a formalized layer between crates and the way that they assemble into your application (i.e. the public API) is powerful for comprehension and maintainability. I go as far as documenting each crate with its own README that presents it as a standalone component with usage instructions, much like an open source library, even if it's only ever used in a single system.

This is nice, I have been lurking on google and meta rust projects, mimicking and picking style by prompting LLMs to distill it, taking a look at fmt & clippy configs helps too. But it wasn't as coherent and reliable from project to project like this guide. Kudos to google on this one !

Much of this is very standard across the Rust ecosystem but it's very helpful to have it all in one place.

Getters and setters is the one I'm most at disagreement with. // Mine let label = Label.text("Hello Wold"); let label_text = label.get_text(); // Theirs let label = Label.set_text("Hello Wold"); let label_text = label.text(); A method is a way to accomplish a specific task. Emphasis on specific not generic. The getter task is to always return. The setter task is specific. So the method should be the setter - `text`, `color`, `fill`. In Rust the getter can't have same name, so prefix it. Not the other way around.

• i2talics · 1 hour ago

  Their style is pervasive in Rust, such as in the standard library, so I would personally apply a when-in-rome philosophy. FWIW something like `.text("hello")` I would expect to see in a builder-pattern but not in a setter for an object that's already built. That being said I don't particularly understand your conception of a method. They are both methods. The getter ought to have a shorter name since it is probably called more frequently and because it inherently has less of an impact -- this goes along with the principle that names that demand attention should be larger and easier to notice.

  • incrediblers · 1 hour ago

    My use case is a TUI framework ( https://www.incredible.rs/ ). The setters configure elements in a chain-able manner. I grappled with the rust convention and decided to go the other way. Rational as mentioned. But this made me think... > "The getter ought to have a shorter name since it is probably called more frequently" So i checked. Rough agent driven counts: https://github.com/ronilan/incredible-flappy 407 setters and 183 getters. https://github.com/ronilan/rusticon 546 setters and 5 getters https://github.com/ronilan/shape-sorting 688 setters and 33 getters. And in a code editor with a lot of ui configurations based on reusable elements 2865 setters and 206 getters. In reactive apps on state handlers call on setters with state values. No getters involved...

    • afdbcreid · 55 minutes ago

      That means those are probably builders and not setters. Do they change an existing object or a newly-constructed or to-be-constructed object?

      • incrediblers · 46 minutes ago

        They are setters. They modify an element after instantiation. Mostly as part of the initial build, but then also in the event closure. Under the hood, a struct with interiorly mutable fields.

• trimbo · 1 hour ago

  This style is aligned with protocol buffers, which is aligned with the style of protos in C++. https://protobuf.dev/reference/rust/rust-generated/

• epage · 48 minutes ago

  I think which to use in general Rust code depends on the purpose of your type. A builder type like `Command` will have unqualified setters and `get_` qualified getters. For record-like-structs, I think unqualified getters becomes preferred and `set_` qualified setters.

I have a huge disagreement here. You should absolutely be using Arc and Rc for any references *that live outside of the call stack.* Don't do weird crap with lifetimes to try and convince the compiler that what you're doing is ok, just throw Rc/Arc on it and be done with it. The Rc/Arc advice also applies to C++ IMO, though you use different constructs, std::shared obviously, but there is a strong argument to be made for a std::shared_st or something which is single threaded. It would not surprise me if this advice comes from experience with C++ where there is no Rc so reference counting is very expensive. Even so, you can greatly reduce the expense by passing things by ref where lifetimes are simple which is the vast majority of the time.

• i2talics · 1 hour ago

  I think using refcounting can allow you to get lazy with your object graphs, throwing referencing to objects around everywhere and then losing the ability to conceptualize who owns what and who is responsible for who (so to speak). Sticking to a stricter ownership graph forces you to be more deliberate with how your types are designed and this can lead to better architecture in the long run.

• wtetzner · 17 minutes ago

  I find using lifetimes to be simpler and easier to follow than reference counting, unless you're in a situation where you actually need a shared lifetime. Adding Rc/Arc is just another layer of indirection and noise that makes the code hard to read.

ctrl+c > ctrl+v > into my AGENTS.md for my next rust project /s

I really appreciate that they distinguish between library code and application code. Rust gets too much of a bad rap for its complicated generic code, but in most application scenarios you are not writing code nearly that complex or generic.

Things like this make me appreciate Gofmt so much

> Type names should be imported and used unqualified This just pushes people to have redundant information in types (`IoError` instead of `io::Error`). Unless a type is widely recognized (like `HashMap`), I prefer to have them fully qualified so I have the contextual meaning for it. If I am working with a generic name like `Source`, what does that mean? I shouldn't have to look up in the imports to understand the code (or only understand it through an LSP). Reducing imports also reduces unnecessary merge conflicts.

• Blikkentrekker · 35 minutes ago

  It says below that that in cases of things like `io::Error` it should be used as that though, as in “cases of ambiguities”. It specifically speaks of not using `regex::Regex` but just `Regex` which seems more reasonable to me.

• wtetzner · 26 minutes ago

  Honestly I think having blanket rules in either direction is a bad idea. Sometimes it makes sense to qualify things, sometimes it's clearer if you don't.

> Usage of lowercase alphabets in hex literals (0xab123cdef as opposed to 0xAB123CDEF): hex_literal_case = Lower Anytime numbers and letters are mixed, the letters should be lowercase. It's easier to read the variable heights - numbers are usually capital letter height, sometimes with descenders - and avoids confusing 0O, I1, even 8B and 5S (think of a degraded printed serial number, poor lighting, etc.). There's only l problem that persists.

Google has lost a lot of it's sheen for me. It's not really the 2010s anymore where their brand really used to mean something as a step above all the other tech companies. Nowadays, I care about their recommendations as much as the ones from microsoft, or ibm. Still big companies, lots of smart people, but nothing above norm.