This is primarily an educational exercise to see how people find compromises that work for them, and languages in the same space as Rust using alternative strategies.
Is this something you experience when writing your code, or is this something you experience when reading other people's code?
If it's the former, I'd really love to hear more about those experiences.
If it's the latter, are there particular features that crop up that make code feel like too much?
(To be clear, Rust isn't perfect for everyone, despite our best efforts. And if you want to work with another language, you should! I'm not looking to defend it; your experiences are valid. We'd love to make Rust better, so I didn't want to miss the opportunity to ask, because we so rarely hear from people in the intersection of "I love Rust" and "Rust is too much".)
I feel like my biggest struggle is simply how hard (tedious?) it is to properly work with generics and some more complex applications of traits. Any time I am working with (especially writing, somehow reading is easier) these, I always take an ungodly amount of time to do anything productive.
I am almost certainly sure this is a skill issue -- I am simply not "Rusting" like I am supposed to. Maybe I overuse generics, maybe I rely on traits too much, maybe I am trying to abstract stuff away too much. But this is one of the reasons I want to also explore other languages in the space, especially ones which make it impossible for me to make this so complex.
Don't get me wrong -- all of this complexity is a joy to work with when I can use my brain. But sometimes, it's just too much effort to do stuff, and it feels like I could be getting away with less. Curiously, I never had a problem with the borrow checker, even though people often complaining about how much it forces them to "stop and think".
Another thing is that C, for some weird reason, always feels "lower level" than Rust, and seeing it gives me some sort of weird satisfaction that Rust does not. Maybe it's just a greener grass syndrome, but wanted to mention it nonetheless.
All this said, I want to just emphasise, that despite this shortcoming (if it even is one), if I were forced to choose a language to spend the rest of my life with, I would not be the least bit sad to only ever use Rust again. I absolutely love it.
> Maybe I overuse generics, maybe I rely on traits too much, maybe I am trying to abstract stuff away too much.
Is this related to the problem where, if you want to put a generic in a data structure (e.g. an implementation of `Write`), you find yourself propagating a generic bound up an entire hierarchy of data structures and functions using those structures?
Asking because one thing that's common amongst Rust developers is a bit of an aversion to using `dyn Trait` types, and using a `Box<dyn Write>` (for instance) in the right place can wildly simplify your program.
> But sometimes, it's just too much effort to do stuff, and it feels like I could be getting away with less.
The next times you find this feeling arising, please feel free to reach out, if you'd like; I would genuinely love to hear about it. You can reach me by DM on the Rust Zulip, or by the email in my profile.
> Another thing is that C, for some weird reason, always feels "lower level" than Rust, and seeing it gives me some sort of weird satisfaction that Rust does not. Maybe it's just a greener grass syndrome, but wanted to mention it nonetheless.
I was originally a C developer, and I can sympathize. I don't tend to crave that "lower level" feeling often, but for me, there was something satisfying about C in the old DOS days, where you could make a pointer to video memory and scribble on it.
> you find yourself propagating a generic bound up an entire hierarchy of data structures and functions using those structures
And I did exactly that. I did eventually get around to using dyn Write, but that still gave me headaches because of how I cannot use impl Write as a result type in closures, which I need to do if I want to use tracing_subscriber::fmt::with_writer() and pass in these trait objects.
Despite being this close to the solution, I somehow again wound up propagating generics back at least four functions.
I ended up not writing any generic-based stuff and resigned to just manually writing each type's implementation out, but I am going to tinker with this again today. Hopefully, I can use your advice.
Thank you so much for taking the time to write this. Means a lot!
> there was something satisfying about C in the old DOS days, where you could make a pointer to video memory and scribble on it
Exactly.
I hope we manage to fix that! We're working on making `impl Trait` usable everywhere a type works. I'll check where "return type of a closure" is on the `impl Trait` radar.
https://rust-lang.zulipchat.com/#narrow/channel/213817-t-lan...
> which I need to do if I want to use tracing_subscriber::fmt::with_writer() and pass in these trait objects.
Would https://docs.rs/tracing-subscriber/0.3.19/tracing_subscriber... help you?
> Thank you so much for taking the time to write this. Means a lot!
Thank you as well for taking the time to fill in more details!
I think even moreso I can understand the sense of Rust feeling too large not because the language itself is, but because there are SO many of these neat tricks and little utility functions that are necessary to express what you want, and it's quite impossible to remember each and every one and how to go back and find them later.
> Would https://docs.rs/tracing-subscriber/0.3.19/tracing_subscriber... help you?
Indeed. This is brilliant.
I never worked with low level languages except some university lession, but I think I have good general understanding how a CPU and memory works (just for some context)
But even for educational purposes, using a language with a poor selection of libraries is likely to lead to a bad experience if what you want to produce is working, non-trivial software. Every project includes some "boring" aspects -- such as parsing configuration and data files -- that you won't necessarily enjoy writing from scratch. The overall programming experience is shaped by much more than the design of the language alone.
One thing that's important to notice, I think, is that low-level languages' combined market share has fallen sharply since the 1970s, and it doesn't seem that the trend is about to sharply reverse direction. To me that suggests that if a low-level language wants to be more popular than C++, it should focus on low-level programming and shouldn't try to also be a good applications programming language (as C++ has tried to do that, but the overall market share of C and C++ is lower now than it was in, say, 1990), but I could be wrong about that.
UnsafeCell I find particularly useful to exponentially decrease the amount of boilerplate needed to convince the compiler that your code is safe.
Yeah, and this points at a deeper issue: the concept of a language being either (binary) memory safe or not does not really make sense. Memory safety is a spectrum and most GC'd languages are safer than Rust (but you won't see a lot of "memory safety" proponents acknowledge this).
Also, there are mitigations that can make "unsafe" languages as secure as something like Rust, but those are deliberately overlooked and hence languages like Zig are constantly bashed using security as the reason.
[Heavy citation needed]
Rust isn't memory safe if and only if:
- You messed up writing safe to unsafe interface (and forgot to sanitize your binary afterwards).
- You tripped one of the few unsound bugs in compiler, which either require washing pointers via allocators or triggering some tangle of traits that runs into compiler bugs
- Somewhere in dependecy tree someone did the one of other things.
That is the definition of a language not being memory-safe. Memory-safety in the language means a guarantee that the resulting program is memory safe, and that you could not mess it up even if you tried.
Taking that to the extreme, it's like saying that a C program isn't memory safe only if you mess up and have UB in your program, something that C program must not have. But C is not a memory safe language precisely because the language doesn't guarantee that. My point is that there's a spectrum here, the goal isn't memory-safety in the language but in the resulting program, and that is usually achieved by some combination of sound guarantees in the language and some care in the code. Of course, languages differ in that balance.
By your definition no language ever would be deemed safe. Even Java/C# has to interface with C. Or you have to write bindings for C libs/ kernel calls.
> But C is not a memory safe language precisely because the language doesn't guarantee that.
C isn't memory safe because it has 212 different ways to cause memory unsafety. And only offers externals runtime tools to deal with it.
I mean Rust will never be perfect due to Rice Theorem. It doesn't have to be either. It's at close to ideal as you can get, without mandating that programmers are perfect (no language errors) or that everything be written in safe Rust (no C bindings).
This is a well known Nirvana fallacy. E.g. If a cure doesn't cure fatal disease in 100% of cases why not let disease take its course?
That's correct. My point is that even if we talk about memory safety only, languages are on a spectrum (e.g. Java programs don't need to use unsafe code as much as Rust programs), and there's always some situations where we don't rely on sound guarantees. In practice, we call languages that easily demarcate their unsafe code "safe languages".
> I mean Rust will never be perfect due to Rice Theorem.
That's nothing to do with Rice's theorem. A language that's completely, 100% memory-safe is not hard to do, but it will need to sacrifice some things that we don't want to sacrifice even for a 100% guarantee of memory safety.
> If a cure doesn't cure fatal disease in 100% of cases why not let disease take its course?
That's not a good analogy for software correctness. A better one would be that every cure has some side-effects. There are languages that, at least in principle, "cure" far, far more than Rust or even Java do, such as ATS or Idris. Why don't we always use them? Because it's hard! What we've gradually learned since the 70s (when a prevailing thought was that we'll have to use proofs to scale software) is that the cost of soundness can be high, and unsound methods (such as tests) are surprisingly effective in practice, and so "more sound guarantees" is not always the best answer. We now believe that for the best correctness per unit of effort we don't want no guarantees at all as in C, and we also don't want to guarantee everything as in ATS, but we're looking for some sweet spots in between. We haven't yet figured out what "the best" sweet spot is or, indeed, if there even is only one.
So are cars, there are cars that are a deathtrap, that send the steering wheel through your guts, and there are cars with seatbelts and airbags that won't save you from others or your own errors, but will minimize it. By your logic, I assume you're driving a Ford Pinto (Zig - has seatbelts but will explode at slightest touch).
You still wouldn't remove the seatbelts because they "chafe", or breaks because it's too much useless mass.
> In practice, we call languages that easily demarcate their unsafe code "safe languages".
That's not true. See Java, it doesn't demarcate unsafe code, you use the unsafe package. Granted, JNI looks about as weird
What in practice most people call safe languages are languages that preserve or have a high likelihood (looking at Go's memory model during data races) to preserve the spatial and temporal memory safety invariant, in absence of implementation errors.
> That's nothing to do with Rice's theorem
Wdym? The presumption is, you don't have a runtime, and you want safety. That means static checks. That means proving properties of your code, implying Rice's theorem.
> A language that's completely, *100% memory-safe is not hard to do.*
> My point is that even if we talk about memory safety only, languages are on a spectrum (e.g. Java programs don't need to use unsafe code as much as Rust programs), and there's always some situations where we don't rely on sound guarantees.
Huh? These two claims are in opposition. If it's easy (doable) to go 100% memory safe, then there should be a trivial way to always rely on memory guarantees. No need for a spectrum.
The spectrum exist because rather than writing OS in Ada, programmers collectively decided to bury their heads into C.
> That's not a good analogy for software correctness
It's not supposed to be a good analogy for software correctness, it was an example of Nirvana fallacy.
> There are languages that, at least in principle, "cure" far, far more than Rust or even Java do, such as ATS or Idris. Why don't we always use them?
Another Nirvana fallacy. On face value, this is an argument to move more to Rust, ATS, Ada and Idris, than it is to abandon them. Or for Rust to get linear types.
That said, in practice I understand these are proof languages with no ecosystem, that might reduce the likeliness of being used in production. But Rust has no such issues. It has a minor proof requirement (make sure your lifetimes are in agreement with the borrow model).
> Because it's hard!
If you avoid things that are hard, you'll never grow. If a programming language you learned didn't cause headaches, it's not a programming language, it's a dialect.
The use of Unsafe in Java is demarcated, and besides, it is now being removed altogether, but we have more interesting things to talk about.
> That means static checks. That means proving properties of your code, implying Rice's theorem.
It doesn't. Rice's theorem talks about the undecidability of proving some arbitrary property of arbitrary programs, but given a property, one can construct a language in which it trivially holds for all programs in the language.
This is done by finding an inductive invariant -- one that is preserved by all program operations -- that implies the property. Let me give you an example. Due to Rice's theorem, it is undecidable whether or not the output of an arbitrary program that yields a number output is even. Nevertheless, it's easy to construct a language (even a Turing-complete one) where this property always holds. We find a stronger invariant -- all numbers in the program are even -- that can be easily made inductive. Indeed, even numbers are closed under addition, subtraction, and multiplication, while for every division operation we add a runtime check that panics if the result is odd (and, of course, the compiler rejects any literal that isn't even). And voila! Not every program that yields an even output can be written in this language, but every program in this language yields an even output.
To see that this is what Rust does with memory safety, note that while every program in safe Rust is memory-safe, not every memory-safe program can be written in safe Rust.
> If it's easy (doable) to go 100% memory safe, then there should be a trivial way to always rely on memory guarantees. No need for a spectrum.
The need for the spectrum arises because we want to sacrifice 100% memory-safety for other things, such as Java's ability to call C code.
> The spectrum exist because rather than writing OS in Ada, programmers collectively decided to bury their heads into C.
As someone who wrote safety-critical avionics software in Ada in the nineties, I can tell you that we had good reasons to largely abandon Ada.
> an example of Nirvana fallacy.
But it isn't because you assume that a language that makes more guarantees will always produce more correct programs per unit of effort, but we know that to be false.
From the vantage point of ATS and Idris, a language like Rust is almost indistinguishable from C. There are a few more properties it guarantees than C does, but ATS/Idris can be used to guarantee any program property. If what I said is a nirvana fallacy, then you must not use Rust and always use ATS, because it is much better on your definition of better. The reason we don't is that we know more sound guarantees are not always better, but we didn't always know that.
In the seventies, software correctness researchers (such as Tony Hoare) assumed that the only path to scaling software would be soundness (proofs, and even formal proofs). As time went on, we learnt that this belief was false from both sides: unsound methods proved surprisingly effective [1], and proofs proved costly to scale, to the point that they made achieving a required level of correctness more costly.
> If you avoid things that are hard, you'll never grow. If a programming language you learned didn't cause headaches, it's not a programming language, it's a dialect.
The problem is not in learning new languages. The problem is that more sound guarantees can sometimes reduce the cost of correctness and sometimes increase it.
Don't get me wrong: Soundness and proofs sometimes work very well, but we in the software correctness/formal methods world know that things are much more complicated than "more soundness more better".
You can read some of my writings on software correctness, after a couple of decades working with formal methods here: https://pron.github.io
If you call importing a package and using it demarcated, I have a bridge and some fog underneath to sell you.
> This is done by finding an inductive invariant -- one that is preserved by all program operations -- that implies the property.
This is a strawman fallacy, we're not talking purely theoreticals. Just because you can build a model of Empire state building from Legos doesn't mean that it will work for the real thing. Your Even Theorem Prover can't write 100 beers on the wall. Or even output Hello <name> for arbitrary name.
Rust, however, can maintain invariants and be expressive enough because it relies on outside the computer assistance (aka unsafe blocks).
> As someone who wrote safety-critical avionics software in Ada in the nineties, I can tell you that we had good reasons to largely abandon Ada.
As an outsider looking at commercial and military avionics failures (I can't be certain, but my guess is it seems cost-cutting on both hardware and software didn't quite pan out), I'm not sure that the right call was made.
> But it isn't because you assume that a language that makes more guarantees will always produce more correct programs per unit of effort, but we know that to be false.
Again, [citations needed]. Google mentioned they had little problem getting people to work with Rust. The onboarding time was around 3 months.
And statements that borrow checker is hard is no different, than saying, well, types are hard, generics are hard, covariance & contravariance are hard, indexes starting at 0 are hard, ones and zeroes are hard. To me, these are complaints of people that didn't run the gauntlet, and didn't build their "muscle memory" in programming.
> But it isn't because
The nirvana fallacy is the informal fallacy of comparing actual things with unrealistic, idealized alternatives.[1] It can also refer to the tendency to assume there is a perfect solution to a particular problem. A closely related concept is the "perfect solution fallacy".
What does Zig give you? No ecosystem, no stability guarantees, and worse memory safety.
No, this is the technique we use in practice in formal methods to prove program properties. When we write a program correctness proof in TLA+ or Lean, this is what we do. This is also how we build invariants into languages. When you learn how to write formal proofs and design type systems, this is what you learn.
> Rust, however, can maintain invariants and be expressive enough because it relies on outside the computer assistance (aka unsafe blocks).
Rust maintains its invariants by making a stronger invariant inductive in the language.
> Google mentioned they had little problem getting people to work with Rust.
I am not talking about Rust in particular. I'm talking about your general point that more soundness is always better, and your claim that my argument is an example of a nirvana fallacy because I compare an imperfect solution to a hypothetical perfect one. I am trying to explain that we know that more soundness is sometimes worse for correctness in practice. The problem is not that more soundness isn't perfect, but that there are currently better solutions than more soundness in some situations.
You seem to be unaware of the shift in software correctness since the seventies. The gap between the size of programs we can prove correct using deductive methods (currently ~10KLOC) and the size of programs produced in industry is only growing. That is why there's been a shift from deductive proofs to methods such as concolic testing (e.g. KLEE). You can see that by looking at the programs for any software verification / formal methods conference.
To be clear, I am not saying that more soundness is never better; I'm saying it is sometimes worse. You can say that we should use ATS more, but the effort of producing software that's proven correct with ATS is not justified by the additional correctness guarantees you gain. I.e., at some point you pay $1000 for improved confidence worth $100.
A program that can't express H (72 in decimal) in Hello world is about as divorced from practicals as you can get, without mixing String theory, Meth and Math.
> Rust maintains its invariants by making a stronger invariant inductive in the language.
Yes, but it relies very little on human verification.
> I'm saying it is sometimes worse.
And I'm saying it as a programmer field we should monotonically approach the ideal by removing languages that don't support it. A language that has memory safety issues is worse than a language that doesn't. We had hundreds of example in practice where people just can't write/compose safe code.
C has a 50 year history and most of the active projects in it are mired in memory safety issues.
Also seatbelts are sometimes worse, doesn't mean we shoud abolish them for seatbelts-less Pintos.
Huh? I was giving an example of how we make undecidable properties trivial in languages. It can be any property. It's easy to see that Rust does the same with memory safety, i.e. through an inductive invariant, because every statement in Rust maintains the invariant.
> Yes, but it relies very little on human verification.
Of course. It shouldn't rely on human verification at all. That's how we design type systems. But because an inductive invariant is inherently conservative and must reject correct programs, there is additional human effort required -- not to verify the property, but to stay within the confines of the inductive invariant. In Rust terms, the compiler takes care of memory safety, but you need to put an effort into expressing memory-safe programs in Rust to fit within Rust's constraints, which are, necessarily more restrictive than memory safety (because they must use an inductive invariant).
> And I'm saying it as a programmer field we should monotonically approach the ideal by removing languages that don't support it.
And I'm saying that what we've learnt over the past five decades is that more soundness does not necessarily mean getting closer to the ideal. Sometimes more soundness gets us further away from the ideal.
> Also seatbelts are sometimes worse, doesn't mean we shoud abolish them for seatbelts-less Pintos.
No one is suggesting that, it's just that what you're referring to as seatbelts could sometimes do more harm than good even for safety. We have empirical evidence that real seatbelts increase safety; things are nowhere near as clear for language soundness.
Sure, C is so exceptionally weak that we can do better than that, and there's no doubt Rust is better on correctness than C, but that's not the same as saying Rust is better on correctness than any language that makes fewer guarantees than Rust. Why? Because, again, we've seen that the benefits of soundness are not linear -- they help until they start hurting. Knowing where that point is is not easy.
Yes, but insisting you have to be 100% machine verified, while the program is correct, it is impractical. While it might be Turing complete, it can't express equivalent behavior to a C program.
This is one of those quotes like "Don't let perfect be the enemy of good".
Look at your definition of memory safety, by it nothing other than ATS or some Lisp derivative running on a Lisp machine is actually memory safe.
Sure, it's theoretically sound, but it's not pragmatical.
> We have empirical evidence that real seatbelts increase safety; things are nowhere near as clear for language soundness.
We have empirical evidence that Rust has measurable impact on bugs, especially memory safety ones.
Neither can safe Rust! But this is easier to see in my example because parity is a very functional, as opposed to technical property.
> This is one of those quotes like "Don't let perfect be the enemy of good".
I am not calling for perfect. Quite the opposite. I am saying that software correctness is extremely complicated, and even the biggest researchers in the field have been surprised by outcomes that were counterintuitive to them. Yet you seem to have decided that Rust gives the best results of everything that's available, while I have my doubts, especially because I see how people are turning away from Rust and how much it struggles to capture a significant portion of the low-level programming market even at its quite advanced age. I don't think there's a single language in the top ten that's had such low adoption at Rust's current age, and that's not the kind of thing you expect to see with a technology whose excited but small fanbase claim to hit an excellent pragmatic sweet spot.
> We have empirical evidence that Rust has measurable impact on bugs, especially memory safety ones.
Compared to C, yes. That's exactly what you expect if more sound guarantees help and then hurt -- a language with some sound guarantees to be better than a language with virtually none. But that is not to say that other languages with either more or less sound guarantees aren't an even better sweet spot.
C++ would be great if people didn't use C style de-reference or arrays, used smart pointers, and avoided "turing complete" template bullshit. It ironically would be almost as memory safe as Rust.
On the contrary, you can also make C very memory safe by avoiding a few patterns.