This is great, because Unreal is a C++ project that's not so easy to just Rewrite In Rust.
It's also nice it uses bevy's ECS. It's made to fit Rust's type system and borrow checking model, and is highly parallel. It's really awesome how easy it is to distribute work across cores with it, without risk of heisenbugs thanks to Rust's data-race-safety guarantees.
I know game development sees traditional software best practices as not applicable to them, but then games struggle with showstopping bugs and single-core performance bottlenecks. I hope someone will bet that Rust, despite being stricter and seemingly slower to iterate with, can be a net benefit from lower defect rates. Rust users outside of game dev praise the "if it compiles, it's usually correct", and that junior devs can be told not to write unsafe code, so they can't cause UB and memory corruption.
Why do specifically Rust programmers think that people in every domain are just misguided and waiting for someone to teach them the right development practices? The sheer hubris…
The kind of bugs that games mostly struggle with these days have nothing to do with the stuff Rust is targeting, like memory safety. They are “business logic” problems with many interacting systems resulting in unpredictable behavior, buggy level geometry, or poorly scripted missions not accounting for all player behavior. How exactly does Rust help with any of that?
Ex-gamedev here, I have no idea what you're on about.
Gamedev isn't some place of rainbows and unicorns that makes it a unique snowflake. I spent more than my fair share of time chasing down heap corruption, invalid iterators and all sorts of other fun issues.
If anything working on a console where the compile, cook, upload, play cycle can be long having something that removes a whole class of errors would have been great back then. I don't think anyone is saying Rust is a silver bullet but it certainly has aspects that are beneficial in certain contexts.
Oh I agree with you: memory bugs are annoying and I've had my share of them. My contention is that, while they waste time here and there, the biggest problems are 1 or 2 layers of abstraction up. I've probably spent 10x more time debugging random physics issues than I did dealing with invalid iterators or heap corruption.
But I mainly take issue with the cockiness of my parent post. Rust is a reasonable evolution which, as you point out, eliminates one class of bugs. But my parent post took it for granted that things should be rewritten in it whenever possible, and that the gamedev community is ignorant of best practices.
The tech industry's demographic pyramid has a really wide base, which is possibly why it seems to build cults around new programming languages so much. Last time it was Ruby, and if we all listened to the equally self-assured Ruby crowd, everything would now be message passing up the wazoo.
I really hope this sort of strawmanning doesn’t become common here. In response to any reasonable discussion about Rust the response seems to be “you’re fine, but the other enthusiasts are so unreasonable”. Where are these enthusiasts? Why bring them up when you can just respond to the person you’re talking to?
It’s super annoying because even on irrelevant threads such haters will call people’s attention to these imagined enthusiasts. Like this comment from 6 days ago calling people jihadis if they like a language - https://news.ycombinator.com/item?id=32640154. Note that the jihadis didn’t exist on the thread, only in the commenter’s mind.
> I will say that I've never written a line of Rust in my life and certainly can't be described as representing the Rust community in any way.
If this is the best example out there then it does feel like GP was arguing against a strawman.
But even otherwise, please let’s acknowledge that in any large community there’s going to be a minority who are loud and rude. It doesn’t advance the conversation much to point it out. They don’t represent the whole community any more than the comment I linked to represents the whole HN community.
All I can say is that whenever I’ve seen such rudeness it’s moderated out pretty quick, whether here or elsewhere.
> Well… Many Rust enthusiasts treat it either as a silver bullet or everything else as unholy (unsafe).
I don't think anyone here is saying that, at least in this thread the parent(and myself) were both careful to qualify there might be contexts that it could be useful in. If you see anyone saying that Rust solves every single problem then feel free to call them out for being full of shit :).
I'm not going to be giving my designers a Rust tutorial the same way we did with scripting Lua, you're still going to have a FFI somewhere which will require unsafe and a bit more care. However having had maintained pretty significant codebases in quite a few languages I will say that Rust code is more stable, crashes less and still runs in the same footprints as C++(C gets the codesize edge by having a much smaller stdlib and surface area). It's about knowing where your tools do well and where they have rough edges and a better tool is appropriate.
Having to switch between C, C++ and Rust codebases on a regular basis I think you're underselling the complexity of C++ and overselling how difficult Rust is. C++ has a huge surface area, you have to figure out what subset you want to use(exceptions: y/n?, RTTI: ditto, stdlib or custom containers, etc). Then you get into Rule-of-5, move semantics, template metaprogramming, undefined behaviors(don't use global constructors/destructors). I could easily list 20 years of various ways I've seen C++ explode in spectacular ways(volatile semantics anyone?).
If you want to use C, Zig, or C++ more power to ya. No one is forcing you to use Rust but for those of us who are interested in a language that isn't dragged along with decades of baggage Rust offers a compelling development story and largely delivers on the areas it aims to hit(accessible systems development, memory safety and first-class tooling in my experience).
The complexity of C++ really does come from the yes/no decisions that every project, library, and code path get to take. Do you know if a library call will throw? hopefully they commented their code well! even better if they maintained comments for all of their dependencies...
And since about half of all game codebase are compiled with -fnoexcept... that means we are left assuming that all library calls may randomly crash or corrupt the stack
Catch exceptions at a few select spots where you actually know something meaningful to do about them. Keep cleanup code in destructors, where it always runs reliably.
Avoid triggering exceptions too hard to recover from. That might involve work, but less work than fielding error codes would have been. There is no free lunch.
Have you written any Rust code by chance? I personally think Rust is easier than C++, possibly because it is a lot smaller language than C++ (at present). It isn't magic, but it kinda feels like it. To be able to do low level coding knowing you can't blow your foot off is pretty cool.
Some stuff that places Rust going into the same kind of complexity as C++.
Figuring out how to turn DAG algorithms into tree based ones, two macro systems, async infrastructure, Pin and PhantomData special fields, GAT (when they arrive).
Lets see how it looks like with 40 years of production code, on the other hand C++ is indeed reaching PL/I levels of complexity for those that care about ISO legalese.
I guess it depends what kind of code you are writing. I've written all of the above w/o too much trouble, but yes, those are the harder parts. However, most of my code is just basic logic, so has very little interaction with that stuff (with exception of async, which I use every day). My C++ is more rusty (pun not intended), but I'm sure there are powerful features that you might use occasionally, but generally don't use much. My point is that day to day coding in Rust is very easy and pleasant, and every once in a while needing an advanced feature that you have to lookup doesn't necessarily make the common case challenging. Like any language, it is hard to tell all this without writing a large project in it.
I've been using C++ on and off since the 90s (borland C++ 5 times) Tried rust at initial release. Read a csv file line by line, split each line read (because I couldn't find any streams), converted to numbers and calculated some stats. Never again. What rust feels like: you are riding a bike, but it has six safety wheels instead of any normal wheels.
I think it’s fair to say that Rust has changed massively since initial release. There are certainly safety aspects, but doing what you describe should be trivial and trigger none or almost none of them.
The compiler’s error messages are fantastically helpful these days. Might be worth a tinker some rainy day, but understand being completely turned off of something as well.
One major change since initial release was the introduction of a more permissive borrow checker. The newer one accepts many more valid programs thanks to the introduction of non-lexical lifetimes.
If that code ever gets more use than that you expect, you can trivially find all the uses of “unwrap()”, and add the proper error handling. And yes there are quite a few places where things can go wrong.
But this explicit “signing for technical debt” when it relates to error handling is a really convenient productivity feature in practice.
A simple throwaway CLI for your own use is absolutely fine to use unwrap(), and you can fix it later on if it becomes a problem.
Unwrap is good to use for things that are expected to work 100% of the time. If unwrap fails in such situations, it’s fine to have the program panic and shut down.
I'm no Rust expert, but I believe reading a file line by line, splitting them, converting to numbers and doing something with them is just a handful of lines using methods on iterators. I suppose it was much harder in the initial release.
I don’t have a dog in this fight, but I’m also surprised to see proverbial fight spring up here so abruptly and a proverbial dog so rapidly entered into the fray. I didn’t see anything in GP suggesting anyone else is misguided, I saw them state clearly why they appreciate the technical choices of a project and hope others will too. To the extent they made any mention of preferences to the contrary, I read it as conciliatory.
As an outsider to both game dev and the general Rust ecosystem, but with a more than passing interest in the ECS data model (entirely apart from games!) and the prospect of using it safely with parallelism (entirely apart from memory safety concerns!), I found GP’s comment insightful and interesting. I find yours unnecessarily defensive.
I get that “in Rust” is a HN lightning rod, but maybe sometimes it’s okay for people to just appreciate someone’s personal project for the reasons they appreciate it, without it being an instant conflict?
This toy project already gives a nice example of something Rust delivered that the author found to be a huge pain in C++: "C++ has one big flaw in Unreal. You can easily crash the editor, either by triggering an assert or accessing a nullptr." but "if you ever unwrap an Option::None or do out of bounds access, unreal-rust will simply catch the panic, exit play mode and log the error to the console. It will never crash the editor."
For a single player turn-based game, I'm not so sure the tradeoff is as obvious as everyone says, after coding one in C++ and another in Rust.
It's turn based, so I don't need AAA game multi-threaded performance. It's single-player, so cheating doesn't really hurt anyone.
I use sanitizers to catch memory problems, but there have only been a few of those over the years. Maybe ECS just isn't that vulnerable to memory-safety problems?
The borrow checker prevents iterator invalidation problems, but most of my functions are read-only so there's not really a chance for those anyway, or many other single-threaded race conditions for that matter.
After this long using Rust, I'm noticing more and more that the borrow checker is imposing a lot of artificial complexity, when I compare it to my C++ version. We're often told that Rust is hard because the underlying problem is hard, but I've encountered many cases where that's not true, it really is just the borrow checker. And unfortunately, most of them are problems that Polonius won't fix.
Rust has a lot of great features (enums and cargo!) but I think one should think carefully about their domain and architecture before choosing a language, lest they pay too much cost for too little benefit.
> It's turn based, so I don't need AAA game multi-threaded performance. It's single-player, so cheating doesn't really hurt anyone.
I don't understand this, just because it's turn based it doesn't mean you can't squeeze more juice out of your CPU if you want to have all kinds of good graphics, fancy animations, fancy complex environments (lots of moving pieces, etc), physics simulation, etc.
Turn based is just one style of play but there's plenty of turn (or pseudo-turn) based games (like JRPGs) which struggle with platform limitations. One could even argue that games like Final Fantasy XIV are turn based.
> I use sanitizers to catch memory problems, but there have only been a few of those over the years. Maybe ECS just isn't that vulnerable to memory-safety problems?
To expand on this a bit. In games, objects generally fit into two categories:
1. Short-lived temporary objects, usually stack-allocated or arena-allocated, etc. e.g. a point vector, or matrix.
2. Long-lived objects with indeterminate lifetime. e.g. a character or item.
In the case of long-lived objects, there are various strategies you could use to make it safe e.g. using object IDs or custom smart pointers to refer to other objects that potentially might go missing instead of pointers which are bound to be corrupted.
Generally you want to register all of your long-lived objects in one central location that will handle memory management. Manual, reference counting or GC are all viable strategies depending on requirements.
I like Rust and would use it for games but mainly because of the package management.
> We're often told that Rust is hard because the underlying problem is hard, but I've encountered many cases where that's not true, it really is just the borrow checker. And unfortunately, most of them are problems that Polonius won't fix.
Out of curiosity, what are your favorite examples?
I would be curious to know more about this case too, fwiw!
Personally, I've only struggled a bit with the borrow checker in a couples of cases: trying to have self/circular references when trying to model OOP, and when fiddling/interacting with some low level async code. Both were unnecessary in my case, and each situation was caused by a lack of understanding.
Previous post mentioned self/circular references. You can't do that with a `Box`. You can with `Rc<RefCell<List` or `*mut List`, but those options either have a runtime cost, or aren't borrow-checked.
Lack of self-referential types that are both safe and zero-cost is a legit limitation of Rust.
Hi! Thanks for taking the time to explain the concept! I'm familiar with these (and others) now, but I was curious to know what others issues the commenter alludes to
Do you use async closures? That's the only case where I felt the borrow checker is a bit behind. Also I haven't checked in a few months and I know there was some work ongoing.
That forced me to start organising the code in a different way which is less functional but easier to understand, so it's not crystal clear what's happening.
In which cases they are already mostly using Erlang, Java, .NET languages, or Go on their server stacks.
Rust is a great C and C++ replacement for low level stuff, I am still not convinced it is worthy versus those languages for distributed computing in terms of the productivity automatic memory management brings to the table.
People should probably stop saying that rust is about memory safety, its design has impact on a lot of others things (that I arguably, care much more about).
> many interacting systems resulting in unpredictable behavior[0], buggy level geometry[1], or poorly scripted missions not accounting for all player behavior[2].
[0]: Rust borrowing system (you know exactly who is allowed to touch each ressource at a given point in time) is great at pushing you away from architecture with too much mutable interaction. That is a side effect of the system rather than its design purpose but, for my point of view, it is one of the main draw to write large projects in rust rather than C++.
[1]: probably not something Rust will help you with.
[2]: Rust type system (and overall coding conventions) is really good at building things such that it will only compile if you check for all cases or, at the very least, leave some explicitly unchecked cases.
Sorry, I think "system" is an overloaded term. I'm not talking about "thread X changed my state", I'm talking about a scenario where the physics system wants to move the player collider, but you want to control its motion with hand-tuned code, so you set it to cinematic, which now causes everything in the scene to go flying when it touches it, because it has effectively infinite inertia. Or maybe you have a system that regenerates your health and an area where healing effects turn into damage and your health regen is now draining the health bar.
These types of interactions exist at a layer where Rust can't help you. Even outside of gamedev, I would claim that most software bugs we run into every day are in this category: too high-level for the borrow checker. (Button not connected to anything. Scrollbar hidden, but the page is too long. Microservices that upgrade independently without API stability.)
> [2]: Rust type system (and overall coding conventions) is really good at building things such that it will only compile if you check for all cases or, at the very least, leave some explicitly unchecked cases.
I invite you to try to teach Rust's type system to level designers.
I mean, dude, I’ve seen the C++ written by organizations with supposedly highly-competent programmers. I think maybe we should let programmers get a little help from language designers.
Sorry, that was a poor phrasing. I mean gamedev has distinct approaches/methodologies/culture/priorities from the rest of the software industry. If you move from gamedev to other application development, you'll find a lot of things taken for granted in one are not that common in the other (an example great GDC talk: https://www.youtube.com/watch?v=t9HRzE7_2Xc)
Other types of software projects also have their own complexity, budgets, changing requirements, and deadlines (admittedly not as major as a game release), but these things are managed differently.
Without telling all of gamedev that they're doing it all wrong, I'd like to say that perhaps there's another methodology that would also work. Especially that some games nowadays aren't just one-offs with a big-bang launch, but are maintained for years after initial release, which makes them look more like other software projects.
Why would you think that? All of the game developers I've met don't really view themselves as separate from traditional software best practices, just that there's a lot more involved in making a game than people are ever really aware of. They're also among some of the most talented programmers, the stuff they have to come up with is insanity sometimes, so it's certainly not about them not caring about best practices.
Games aren't struggling because they're written in Unreal's flavor of C++ (or whatever other currently existing engines and their respective languages), there are insane deadlines always being pushed. There is never enough time and never enough money. Neither of these problems are solved with Rust, at least not to a substantial degree.
> Rust users outside of game dev praise the "if it compiles, it's usually correct",
Why do people keep echoing this sentiment? I don't find this to be particularly true, in my sense of "correct". Yes, it does what the code says it'll do, but rarely the problem I actually get stuck at are language/syntax/semantic errors, it's usually domain/logic errors.
Same can be said for PHP, JavaScript and a bunch of languages, as every program that is possible to run without error, is correct, at least in the eyes of the interpreter. But again, the difficult errors are not syntax/language errors.
I think the phrase is a misquote. I think the original quote is "if it compiles, it runs." Secifically for canonical, safe Rust. As in: "if it compiles it runs and does not explode in your face in a place you didn't expect."
After four years of Rust (and 25+ of C++) I find this very true for the former and rarely for the latter except in extremely simple programs.
And yes, this says nothing about correctness as far as what the code is intended to in the first place.
But you are wrong when saying this, too, applies to e.g. PHP or JS in this context. For the simple reason that they are dynamically typed alone. The class of errors/side effects that this enables is a whole different league.
>"but rarely the problem I actually get stuck at are language/syntax/semantic errors, it's usually domain/logic errors."
Exactly my case. I've forgotten last time I've had memory
alloc / free/ overrun /free after use etc. related bug in my C++ projects. I am using modern C++ which in combination with STL containers makes me forget about all this C++ is scary FUD. I am however not being "turn everything into template" maniac and in general trying for code not to be fancy but rather readable.
I first heard this phrase applied to Haskell. Both Haskell and Rust have sophisticated type systems, Haskell more-so than Rust. With a sophisticated type system, you can accurately encode the rules of your domain in the types and thus, when the program compiles you can be confident it will do the right thing.
Having written a fair amount in both languages as well as many others I find this to hold true. The phrase isn't, primarily anyway, about Rust's memory safety guarantees in my mind.
Yeah, it's such as silly sentiment, which honestly makes me wonder about the skill of the programmers repeating it. Exactly none of the bugs I've fixed in the last month had anything to do with memory corruption or data races or other undefined behavior.
It feels like something was misquoted at some point.
The main benefit of Rust towards safety is not memory safety or data race safety or undefined behavior. The main benefit of Rust towards safety is a strong type system with affine typing. When used properly, this eliminates huge classes of bugs. Most of the bugs that I need to fight when I'm writing in Python or JS, for instance, are simply impossible in Rust.
Of course, when I'm writing C++ (which I don't do a lot these days), I really miss all the features that you mentioned.
It's also nice it uses bevy's ECS. It's made to fit Rust's type system and borrow checking model, and is highly parallel. It's really awesome how easy it is to distribute work across cores with it, without risk of heisenbugs thanks to Rust's data-race-safety guarantees.
I know game development sees traditional software best practices as not applicable to them, but then games struggle with showstopping bugs and single-core performance bottlenecks. I hope someone will bet that Rust, despite being stricter and seemingly slower to iterate with, can be a net benefit from lower defect rates. Rust users outside of game dev praise the "if it compiles, it's usually correct", and that junior devs can be told not to write unsafe code, so they can't cause UB and memory corruption.