For most people who program for a living, the hype over Rust means little. They need to use what is in the industry right now. Often, that is a tried and true language that is relatively easy to learn and use.
Having a complex programming language which limits you and controls how you use it does not sound appealing to those who need a feature done, fast.
This is so interesting to me. I'm a Rust programmer by trade (as in - I'm not a hobbyist, I actually write Rust for work). We've found that, while the feature work is a bit slower in Rust than in other languages the company used to use (mostly Python), they tend to require a lot less maintenance down the line (less bugs, easier refactoring), and so it ends up canceling out a bit.
I also never find that Rust limits or controls me in my day to day work. There are some things you cannot do easily, sure, but those things tend to not matter in application code. Linked lists are hard, graphs are hard, but when writing an app, I just use an existing dependency like petgraph or std::collections::LinkedList instead of reimplementing those datastructures. And if you need to write those things, it's not like it's impossible, you just need to drop down to unsafe rust, and ideally figure out some safe way to expose that API.
Really, the biggest disadvantage of Rust is that its learning curve makes onboarding newcomers much harder if they don't have experience in the language. For Python/Go/JS/Ruby you don't really have this problem, even if a potential recruit doesn't have experience in the language, they will probably be able to pick it up as they go without too much trouble. But in Rust, it can take a fairly significant amount of time to get up to speed and stop fighting the compiler, in the order of several months.
A lot of programs written in Rust would almost certainly be better off being written in Kotlin. The one in the article is a good example. Why are they writing a messenger bot in Rust? That doesn't seem like the sort of use case Rust was targeted at. It's also a modern language with a lightweight syntax and pretty good static typing, great refactoring tools etc, but it's way more user friendly. There's no borrow checker because it's GCd, compile times are much faster (at least for the JVM version) etc.
You can also use Kotlin/Native or GraalVM native-image to produce standalone executables that don't need a full JVM, if that's a requirement for your use cases. The native images are astounding. They can start faster than programs written in C and their memory usage is also way less than a typical JVM app. Downside is of course compilation time but you can avoid that by just developing on the normal JVM and then AOT compiling at the end when it's time to release.
AFAICT Rust is a general purpose programming language. People can use it how they want. How do you learn a recent programming language? "hey boss I'm going to write production code in a new language that I haven't learned. Lol YOLO"
Now if we were talking about some other "new languages" not naming names, you can memory leak kilobytes writing hello world... Yikes.
Dynamic languages and GC'd languages cover most of what our employers are paying us for: web apps, backend services. It is ironic to build super safe software, then deploying them on kubernetes, written in a GC'd language prone to nil dereference errors.
Rust has its place, but it's a very small place. These days computers are so fast there's companies worth billions built on Ruby and Python, if you go native with a GC language you'll cover 98% of your needs.
Rust IMHO has gone too far towards safety at the expense of developer ergonomics and pragmatism. We're so expensive that adopting a subpar language that is easier to grok is often a savvier business decision.
Indeed. I'm a Rust dev somewhere it actually matters (video dev - we have to process 60 frames a second, for hours/days on end, with completely predictable performance, without crashing once) and I'd never pick it if I just wanted to build a webapp where nothing really matters and if the whole thing falls over we can just put it in a retry loop.
There's plenty of code out there that /cannot/ be written in Ruby/Python/Go/C#. Rust solves some really hard problems for people working on that type of code. But it's not what most people on HN are working on.
I think the problem is that a lot of web developers do not really understand that this type of code exists, and that languages which do not target web development can be exciting.
But without even going as far as frontend web applications, stuff like backend services, system services, GUI applications, CLI applications, etc., don't actually need all that much memory safety and control over allocations.
My understanding is that Rust was designed to be a safe(er) language to write low-level system code than C/C++, not to compete with Python/Ruby/Java for web development applications.
I'm complaining about everybody on programming forums, including HN, seeing Rust as the replacement for most, if not all languages. My opinion is that Rust's ideal problem space is much narrower than people think.
>It is ironic to build super safe software, then deploying them on kubernetes, written in a GC'd language prone to nil dereference errors.
Nil dereference errors don't demonstrate an absence of memory safety. If the runtime checks for a nil reference before dereferencing and then raises an exception, that's perfectly safe.
I don't think the null handling in rust is about memory safety so much as it is their choice in error handling. If you come across a null pointer dereference and your code doesn't handle it, that's a hidden bug. Triggering an exception and handling it is a valid approach, but there are trade-offs. If no code handles the nil exception for example then it's no better than crashing as you would in C. Wrapping things up in try catch can lead to missing recoverable errors or unexpected states. The choice to disallow null is one to avoid common bugs, not one for memory safety, as far as I understand it.
> One common example is modifying a vector element by reference. If you grab a reference to an item, push something else to the vector, then try to access through that reference, the vector may have re allocated during the push and you're either no longer looking at valid memory because it's been freed, or you're looking at a stale copy of the element.
There aren't that many languages which both use GC and allow you to take references to elements of a vector. Go would be one example. I can assure you that you cannot access undefined memory regions by doing this in Go. (What would happen is that the original allocation backing the vector would be retained in addition to the new allocation.)
>If no code handles the nil exception for example then it's no better than crashing as you would in C
C programs are not guaranteed to crash when a pointer has an invalid value. Dereferencing a NULL pointer will reliably cause a crash if you're running the code on top of a modern general purpose operating system with memory protection, but invalid pointers (which don't necessarily have to be NULL) have the potential to access arbitrary memory regions without raising any kind of error.
Current implementation of slices and interfaces in Go is not memory safe in presence of data races:
https://blog.stalkr.net/2022/01/universal-go-exploit-using-d...
Nope, unsafe isn't a way to do dependent typing in Rust.
This is something that escapes a lot of people nowadays.
Everyone uses a browser and they are inherently unsafe.
Meaning that Firefox's gains with Rust will eventually be lost given its market adoption is slowing reaching zero.
https://docs.google.com/document/d/e/2PACX-1vRZr-HJcYmf2Y76D...
https://www.chromium.org/Home/chromium-security/memory-safet...
But yes you are right, anytime you have two or more accesses to a data structure you do have to think a little harder about it. Usually you just want to use a reference to that object, sometimes it makes sense to clone it, sometimes you want to pass it by value and return it by value. In the case of doubly linked lists you probably want to drop into unsafe code.
I get it though, GC languages are more zen in that regard.
Libraries are typically optimized for generic use, so are often more complex, slow, and difficult to extend with new features (both coding wise or the features might not be suitable / have trade offs for other people).
Yes making data structures is important, and the reality of that is, there are people in the ecosystem creating fancy ones which can be leveraged for your use case.
If that doesn't exist then yea you have to write them. Sometimes that's difficult(you need to use unsafe), sometimes it's easyish and you can use all safe(I did this for a graph type). It can be done(lots of people are doing it), but I think what it shows is, data structures can be difficult to do correctly.
In a worst case scenario you could write it in asm inside rust if you really need a low level control, or write it in C/unsafe rust and ffi or just write it in.
Basically worst case scenario in rust is writing something closer to C.
That isn't to say a narrow ecosystem is necessarily bad, it can often be good if a particular language is used for a specific domain as all the libraries and data structures will likely be a better fit for your problems. Going outside of those constraints can often be very punishing in those languages though.
My advice would be not to judge any language on how easy it is to implement a doubly linked list. 99% of code you write will likely not be that, and that particular data structure exposes a lot of choices and trade offs at a time when youd be better served learning other parts of the language.
IMHO Rust's lifetime analysis should consider borrows only at the point of dereference, not just whenever you encounter an & symbol. They already do that with raw pointers - you can have as many pointers as you want but you only need to mark `unsafe` if you actually dereference one. So at least someone on the team knows how to make that work functionally.
I'm sure you know this already, but for the people reading this: first of all "unsafe" is a very rare, and it's only "less safe" more than fully "unsafe"; ie it's still safer than C++.
And the second thing is that, often you don't have to drop into unsafe Rust, it's possible to achieve most stuff without it, but might incur a small performance cost (idk if some of those can be optimised away by compilers or not).
Python to Rust is a pretty radical swing from one approach to language design to another. I'd expect you could solve most of the maintenance problems with Python by switching to something statically typed but with garbage collection (e.g., C#, Java, or go), without incurring the costs of moving to Rust.
When a lot of what you're doing is interacting with low-level platform APIs, you end up having a lot of those unmanaged objects. After a certain point, the upsides of using a GC kind of disappear because you still have a lot of places you have to worry about those objects.
Of course, this can be worked around by providing managed wrappers around those unmanaged object, but at a certain point, it becomes easier to just drop down to an unmanaged but safe language (like Rust) that model the unmanaged resources more accurately. In my experience, it's somewhat easier to provide Safe Rust wrappers around your average Windows API than it is to provide a C# Managed Wrapper around the same.
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And yes, go is special because it has very smol stacks, so doing any kind of FFI on it is a bad idea.
I'm genuinely curious as to what would make FFI in Rust easier than in C#, assuming an apples-to-apples comparison (i.e. use of "unsafe" and associated features in both cases"). Most complexity in P/Invoke shows up when you try to use it to automatically map data to managed data types; but in modern C#, you might as well just use raw pointers, stackalloc, spans etc.
...so requiring `use of "unsafe"` is often akin to forbidding Cargo/pip/NPM/etc. and then calling the language un-productive or faulting a procedural/imperative language for performing badly when you code as if you're writing Haskell.
https://www.hobofan.com/rust-interop/
https://areweextendingyet.github.io/
Using the ecosystem rather than reinventing it is a core tenet of Rust's value proposition.
This sounds as insane to me as a carpenter who works with power tools saying. "Having safety measures which limits you and controls how you you have to do certain things does not sound appealing to those who need a house build, fast."
It's not good, and when a bridge falls over the results are a bit more... dramatic and undeniable - but it's not really my impression that other branches of engineering are particularly immune from corner-cutting and deliberate under-estimation.
Edit: though I'll say, just having someone "at random" say they expect better in their industry is an anecdotal evidence that it is at least a bit better. Also, you get to work outside. Truly, grass is greener on the other side of the road.
In case you haven't seen it, there's been some interesting progress on that front:
Believe it or not industry has and is continuing to adopt rust. Microsoft, AWS, government agencys in Europe, the Linux kernel itself (the only other language allowed there is C - think about it). It's really not all hype, people like it because it solves a class of problems from never happening while still performing very well.
I invite you to join the community and learn it. It's a lot of fun once you get proficient with it.
This is the ideal, but not always the reality. The Rust borrow checker isn't perfect, so sometimes it rejects code that should work perfectly fine. Hopefully as the language matures (Polonius, GATs, HRTBs…) these cases will become rarer.
Come to think of it, an even simpler example is a mutable iterator for a typical data structure. Such iterators usually require 'unsafe' code to implement, even though they are perfectly safe to use. https://stackoverflow.com/questions/63437935/in-rust-how-do-...
A lot of people don't seem to realize how easy it is to get UB in other languages. The C spec for example claimed not having a trailing newline at the end of a file was UB...
I also don't think this was an example of code that should compile but doesn't. Rusts' ownership rules make this task hard, but there are lots of people using doubly linked lists in rust... Yes they used unsafe code to do it, and yes it does compile .
The question was show us a case where the borrow checker was wrong.
I'm fully aware of this. That's why I put 'unsafe' in quotes.
However, it's surely fair to point out that you can't implement doubly linked lists or mutable iterators in Rust without giving up Rust's usual guarantee of memory safety. If this guarantee is not actually that big of a deal, as you appear to be suggesting, then why all the hype about it from Rust advocates?
>The question was show us a case where the borrow checker was wrong.
No, that was not the question. OP just asked for 'rejected code that should work perfectly fine'. There are of course loads of examples of such code. Perhaps the simplest is the case of mutable iterators that I mentioned. A correctly implemented mutable iterator is perfectly safe, but rejected by Rust's borrow checker unless certain parts of the implementation are marked unsafe.
And no, memory safety is a huge deal, it is just that the borrow checker cannot verify the soundness of certain code, meaning you have to provide the guarantees normally given to you outside 'unsafe' blocks.
Yes, this means that a few data structures require 'unsafe', but you should be creating safe wrappers around these structures; 'unsafe' won't propagate up your code and poison everything.
And I was just proving examples of such code for someone who asked. Honestly, some Rust folks get so defensive it makes them very prone to misinterpret simple factual statements about Rust as criticism.
Apparently you don’t disagree with any of the factual statements that I’m making. You just have some vague unsubstantiated feeling that I don’t ‘get’ Rust.
You're adding other claims and statements that make me question if you actually understand the thing you are criticising.
I will if the Rust community agrees on a lighter, less complex language core.
"Microsoft, AWS, government agencys in Europe, the Linux kernel itself (the only other language allowed there is C - think about it)."
Again, they are using only a subset of the language. Linus allowed it in the kernel once devs agreed only to use the Rust core features. They even had to make a new memory allocator, IIRC.
They also didn’t have to write a new allocator; they did extend the interface of the “alloc” library (which sits between core and std) which was then also accepted upstream.
It's also kind of normal to you know tweak a language so it integrates with an OS better... Even if they did change their allocator, who cares?
I think that a lot of complexity in Rust comes from many different ways to handle memory. You have your Arcs, Boxes, Cells, etc. Then you have a core "alloc" library.
Maybe if everyone agreed on a single reliable method to handle heap memory (since using stack is easy), Rust wouldn't be so hard to use.
The syntax also could be improved. Seeing <Box(T)> or whatever nested three or more levels deep hurts my eyes.
Boxes, cells, arcs, etc. exist for different purposes and if you'd take two hours to actually read about them and their uses, you'd understand why they exist.
Rust really does not limit you. Anything possible in C or C++ can be done in Rust if you're willing to use unsafe code.
Most of that difference is in things that happen at compile time, so this is not a question of Turing completeness.
Do you have any examples?
The heart of C++ is destructors: a bit of code that you can write and the compiler will ensure runs when code goes out of scope/is deleted. You can do this in C by remembering to manually call the right code when doing clean up, but it is easy to forget and thus error pron. (I think Rust has this too?)
C++ gives you the ability to do a virtual base class interface, which - as most people know - just means it writes a vtable behind the scene for you. Sometimes people write a vtable by hand in C: it is just a struct of function pointers, but the syntax to do it in C++ is a lot nicer. If you need an interface of some sort the win goes to C++ because the syntax is a lot nicer. (I'm not sure what Rust does about interfaces, I think it has something)
C++ gives you control over copying structs. In C structs are only copied member wise, if the struct has a pointer you need to keep track of both copies so you don't free it early. In C++ you write a copy function that will make a copy of the pointer. You can do this in C by remembering to call the right function when copying a struct, but the default is the wrong thing. (I'm not sure what rust has here, but at the very least the borrow checker will stop you from making a mistake)
C++ gives you move objects - a way to express that a struct is going out of scope, but only after a different one is taking over the contents. This is a variation of the previous, except that you know the original doesn't need valid data anymore and so you just copy pointers and null them in the original. C doesn't have this concept, you can get around it with use of pointers and manual copying of structs in the right places, but the code is ugly. (again, I'm not sure what rust does, if nothing else the borrow checker should allow the compiler to make some optimizations on this lines)
There are a lot more areas where C++ gives you syntax to write correct code that C does not. Rust intentionally doesn't have some of them (class inheritance has been abused often, but I still find it useful enough in a few cases that I think rust is wrong for throwing it out), and in other cases has come up with a better syntax. Overall I don't know enough about Rust to judge it, but I'll take C over C++ anyday.
Note, the above is about the advantages of C++ over C. C++ has a lot of warts that are out of scope for that discussion. I am not claiming C++ is perfect. If you are starting a new project you should seriously consider your language options - including some not mentioned here)
I'm somewhat confused about why it was downvoted - there is nothing there controversial at all.
[1] In my own toy language, I'm kinda leaning towards objects with destructors. Definitely without the footguns in C++, but destructors nonetheless.
Did you mean the opposite?
Rust doesn't have class inheritance, no, but often combining traits and delegating to a "parent" field works. Although sometimes that can be considerably more cumbersome, yeah.
With the C++ approach I've found myself overthinking the problem many times. But with the insight that pointers are just data, and memory management can be independent, it turns out that programming with raw pointers need not be hard. There is no problem passing a pointer without "move semantics" shenanigans.
I'm not saying that it has to be this way, but there is a reason why something like unique_ptr (that can be quite tedious to use in my experience) has become so popular in many projects - IMO it is overused, often leading to more typing work instead of less.
If one is sufficiently used to this way of modelling, it can come as a surprise that memory management needn't be so hard, and doesn't require smart pointers or anything, if the program design (global flow of data etc.) is sufficiently clear.
There is no sense, in C++, in which a naked pointer implies or suggests ownership. It is the opposite: the continued validity of a pointer value depends on ownership maintained elsewhere. Nowadays libraries keep track of ownership. Most commonly the library delegates that responsibility to Standard std::unique_ptr, for familiarity. Not doing that indicates something different in play.
(It is, in fact, UB even in C to copy the value of a pointer to an object that does not exist anymore. This is the case regardless whether it had pointed to or into a stack or a heap object.)
In C, there is no way to express library ownership of a pointer. So, in C there is always potential for confusion about ownership.
I give you one advice: Think twice before writing this way again. You are not putting enough effort into understanding what I'm trying to say, and coming across as an arrogant prick.
https://news.ycombinator.com/item?id=31494099
Admittedly, I didn't make my point sufficiently clear, but this isn't even about being right or wrong. (And, once more, I understand what you say. Stop belittling me.)
> Having a complex programming language which limits you and controls how you use it does not sound appealing to those who need a feature done, fast.
See, I don't think Rust makes that _harder_ - I think it surfaces the real complexity, makes is undeniable. So far in my - by now 20 year old - career, when I've seen most teams faced with complexity that might either slow down a project, or be swept under the rug, the latter was always chosen.
There are _business reasons_ for that, software projects don't live in a vacuum - but those reasons are... _depressing_ at best - by far the biggest one I've seen is that a correctly estimated project would never be approved. Let's just say that figuring that out is a cognitive hazard that can easily increase risk of burning out - literally the sort of knowledge you're better off ignoring.
So ultimately my line of thinking is, Rust's problem in the business sense is basically the same as when you try to code in it: it _tells you that you're trying to sweep something under the carpet_. It tells you that your feature's cost is under-estimated. And to be fair: what can you do about it? The feature wasn't truly estimated by you. It was, almost certainly, estimated by your boss to be "one sprint at most," before he even asked you, and "please estimate this" has an expected answer, and giving any other one has a high social cost. And goddess protect you if your answer might call the entire business model into question.
I don't think any of us can change this, nor that the software engineering workforce is ready to push for changing this. Because even if we convince _our boss_ - the investors will just pick someone else, after all.
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Anyhow, now you'd be excused in expecting me to advocate some sort of gatekeeping - but no, what I like about Rust is that it attempts to make programming more accessible in a _very different way_ to how many high-level programming languages did. For example:
- it's not _just_ a systems programming language. It doesn't divide programming into "stuff for anyone" and "eldritch monstrosities for the Chosen Ones" - eldritch stuff is just around the corner, in the same language, - it doesn't try to hide the complexity - it tries to give you tools to _explore it_, - and, expanding on the latter, its community values documentation and teaching over restricting use cases.
I don't think Rust is entirely _successful_ at that - but I think that the different model for accessibility is, if anything, more interesting than the borrow checker. I don't think we really need a single language - a garbage collector can be performant and useful, for example, and does it really _have to_ actually result in sweeping complexity under the rug?