Zig's incremental builds are DEFINITELY a killer feature. In the short term, I could see why you'd make a switch to get it. But, in the medium term, can we really not expect to see this in Rust in the somewhat near future?
I'm not sure it would ever make sense to be. That makes the assumption tons of allocations get made that don't live long, which was(maybe is still?) more common in some languages. Go is more aggressive about not heap allocating, and has tools to help you avoid them.
Instead of waiting for incremental builds and faster compiler in Rust (or LLVM, I guess), how about from the other direction, adding some kind of borrow checker to Zig? That sounds more within reach and practically achievable, possibly even in userland.
> how about from the other direction, adding some kind of borrow checker to Zig? That sounds more within reach and practically achievable, possibly even in userland.
It's doable, and as static analysis. see sibling comment.
It's impossible to add a borrow checker to any existing language.
The reason Rust has a working borrow checker is because every part of the language from structs, enum, traits, generics and all the way to the syntax itself has been designed to support lifetimes and borrow checking.
It's is not something you can just tack on to an existing language without fundamentally changing it.
> It's impossible to add a borrow checker to any existing language.
Why do you say that. Have you tried and failed? It seems to be possible to add a borrow checker to zig, just as you can add MIRI to rust to get extra safety in unsafe blocks.
> remember that for compilers which emit machine code, like roc and rustc, doing memory-unsafe things is a big part of the job
I don't really think that this is true, in the way that it's written.
I think that for the hot binary patching / code reloading features, yes, that is going to need unsafe. But for regular old "producing an executable" compilation? Emitting machine code isn't the part that requires unsafe. The language's runtime is a more likely site to find unsafe.
They are saying that running the compiled code is memory-unsafe when there is a compiler bug, and that’s what developers do next. The memory corruption happens in a different process.
In this respect, effectively all the compiler should be treated as an unsafe region that requires extra care to avoid memory corruption bugs.
The article is a bit confusing because they also write:
> Regardless of which process had the bug—the compiler or compiled program—in both cases the processor only did the bad thing because the compiler told it to. And in both cases the fix is the same: the compiler's code must change, since that code was what caused the memory corruption.
But yeah, I wonder what those 1,200 unsafe uses actually did?
Yeah that is definitely 1000% wrong. A compiler can do its job with totally abstract data structures. If anything would need to do unsafe stuff in memory, it would probably be a linker.
I think it's an understandable prior. Historically, "low level stuff" was near-exclusively (see my comment below about OCaml...) written in unsafe languages. Even if that wasn't always literally required, it sometimes was, and so thinking this is the case was a reasonable thing to think.
It is only relatively recently that we have gained more realistic options in these spaces, and so not fully understanding the implications, or preferring the historically normal choices, is understandable.
I'll play devil's advocate. I think emitting machine code intended to run is unsafe because you could emit unsafe machine code, which could run. It's the whole system that is either safe or not, not the individual components. If your system gets hacked by a buffer overflow in the end, nobody cares whether it was the linker that overflowed or the code emitted by the linker.
"Safe" has a very specific definition in Rust. It's not identical to the broader definition used in technical English. You can easily have safe rust code with behaviors any reasonable layperson would call unsafe, like crashing a plane. The original article, comment, and replies were using the word in the Rust sense from my reading, not the English meaning.
2. Has an objective definition, when some other forms of safety are either subjective or inter-subjective.
That said, I don't understand why your parent brought this up to you, you are talking about memory safety in your original comment here, so that's what Rust's safety is about.
This is impossible. General words like "safe" and "good" are subjective, and useless in a technical context unless you ground the discussion by giving them specific definitions. Otherwise everyone ends up talking past each other.
> It's the whole system that is either safe or not, not the individual components.
This is a core perspective disagreement. While this is true:
> If your system gets hacked by a buffer overflow in the end, nobody cares whether it was the linker that overflowed or the code emitted by the linker.
That does not mean that increasing the amount of safety in the individual components isn't helpful, because it helps minimize the above outcome, even if it will never be zero.
I think if you interpret it charitably it means that any bug in the emitted machine code is already a likely memory-unsafe miscompilation if it is ran.
The compiler itself might be perfectly "memory safe" but the generated binary fundamentally is always at risk.
I do think that is a good point, it's just not what the line actually says. But that's why I wasn't saying "zomg this is WRONG!!!!" but instead, trying to point out that there are subtleties here. For people who aren't as deep in the weeds in this subject, I think the details matter. But again, as I said, I like the post, this is just one thing.
I am also probably in a more pedantic mindset because, well, I'm writing a compiler in Rust, and the words as written do not resonate with me at all.
> a perfectly safe compiler that generates vulnerable binaries isn't that much better.
I do think it's much better. Eliminating classes of bugs in one component is a good thing, even if it's not every component. This is a core lesson of Rust! unsafe still exists, but going from "I don't know what is unsafe" to "only this part is unsafe" is a major improvement.
In context that's clearly not what he's saying, the next sentence is this:
> Zig has more features than Rust for making memory-unsafe code work correctly, and that was the area where we wanted the most help.
Zig definitely does not have more features for successfully emitting memory-unsafe machine code than Rust does. I can emit memory-unsafe machine code from typescript if I really want to and nothing at all in the language will get in my way. So the sentence quoted above must refer to the idea that the compiler itself needs to be unsafe, which Steve is right is simply untrue.
> I think that for the hot binary patching / code reloading features, yes, that is going to need unsafe. But for regular old "producing an executable" compilation? Emitting machine code isn't the part that requires unsafe. The language's runtime is a more likely site to find unsafe.
Agreed! Emitting machine code is not unsafe, since it's just writing bytes down - it's only once you execute that machine code that there's potentially unsafety. The reason I said "a big part of the job" is that in practice a lot of compilers both emit machine code and execute it - but you're totally right that it's not a requirement that a compiler do both.
In addition to the examples you gave (hot binary patching/code reloading, language runtime, etc.), others would be things like evaluating userspace code at compile time (e.g. const fn in Rust, or in Roc any expression that could be hoisted to the top level), running tests and inspecting their output to decide what to display to the user, etc.
Those are the types of things I had in mind when I wrote that.
I am disappointed you're downvoted, Richard. This is a fine reply, and I hope you know that a minor quibble with a single line in the post doesn't mean that I think it's a bad one overall. (EDIT: a few minutes later, the parent comment is no longer grey.)
I also think it's a good thing that you wrote the post in general, when I saw it pop up I was like "oh, of course, this post should exist!" I'm surprised I didn't think about it earlier.
> evaluating userspace code at compile time
Usually this would be done via an interpreter, so I'm not sure that it really requires unsafe either. If you are literally executing machine code, sure, but const fn in Rust and constexpr in C++ and many other languages do not do that, as it causes a number of problems (for example, cross-compilation).
Also a good point! TIL that Rust and C++ use interpreters for const, although of course that wouldn't work for running tests. Then again, in the specific case of Rust I believe rustc only compiles the tests and then something else like Cargo executes them. Of course, as I noted elsewhere, if rustc emits machine code and then cargo immediately executes it, there's the same opportunity for end user memory being corrupted (due to miscompilation) as if rustc and cargo shared a code base.
By the way, I thought your question was totally reasonable - my first thought reading it was "Oh yeah I wasn't trying to say that writing bytes is unsafe, I definitely should have worded that differently."
> rustc emits machine code and then cargo immediately executes it, there's the same opportunity for end user memory being corrupted (due to miscompilation) as if rustc and cargo shared a code base.
Cause this hasn't been true for me or for anyone maybe your definition of memory being corrupted is the not same as mine.
I am not even sure what you are trying to prove with this.
I appreciate the time and effort in building stuff like Roc I don't use it but this comment and the article feel like...
Oh some guy said Zig not nice because memory safety so here, a post why memory safety doesn't exist because we have to do memory unsafe things sometimes and so everything is memory unsafe already, so maybe it doesn't matter.
I get the energy that we are going for seeing useless claims and wanting to push back but I think the article deserves a clearer part 2 where you elaborate on your thoughts about stuff maybe even get it peer reviewed a bit before posting or maybe don't I guess we could use more raw thoughts in the post AI age.
Either way I appreciate someone trying to put forward their own thoughts and explain problems with a different perspective.
Cool, I'm not sure that people know that we know each other and have some deeper mutual understanding. :)
> although of course that wouldn't work for running tests.
Why not? Unless you mean in the cross-compilation case, in which yeah, to run the compiled tests you'd need an emulator.
> in the specific case of Rust I believe rustc only compiles the tests and then something else like Cargo executes them.
It doesn't have to be Cargo, but yes, rustc produces executables for the tests, and you have to then run them.
> there's the same opportunity for end user memory being corrupted (due to miscompilation)
I agree for sure that the safety of the outputted binary is completely distinct from the safety of the compiler itself.
I think the reason that this framing specifically (in the post and in this comment) strikes me as odd is that "requires unsafe code" sort of implies that you need to use unsafe to fix the unsafety of the outputted binary. That just isn't the case. Of course, this is a serious bug that needs to be fixed, but there's just something about "doing memory unsafe things" in this area that like, I think can be a little mis-leading, even if that's not intentional. But I am going to sit with this and think about it, regardless, because I am not sure that my gut reaction here is completely accurate.
(And, hilariously, looking over some work my agents did on my compiler last night, they fixed some mis-compilations that occurred, entirely in safe code. I bet that's also part of why I'm in this headspace at the moment, it's not like those fixes required dropping down into unsafe to fix either!)
> if rustc emits machine code and then cargo immediately executes it, there's the same opportunity for end user memory being corrupted (due to miscompilation) as if rustc and cargo shared a code base
Your tests run in an entirely separate process from the compiler (and from cargo). This makes it very different from memory corruption in the compiler:
- The test process can only corrupt its own memory.
- You don't need "unsafe" to run tests. Just the ability to start another process.
- If you're cross-compiling, you wouldn't even be able to run the tests on the same machine (without emulation/compatibility layers)
Does roc run tests in the same process as the compiler?
I agree that it’s not inherent to emitting machine code but I do think it reflects a different set of priorities.
In extremely high performance code you use different data structures and algorithms and change your approach to memory allocation. TigerBeetle famously does all memory allocation once on startup.
Roc is attempting to make a similar set of trade-offs in their compiler as Zig, so it makes sense that the author finds many shared patterns.
>ReleaseSafe catches use-after-free errors through runtime checks which panic if the program tries to use freed memory.
I don't know Zig so maybe they know something I don't, but I have seen no evidence that it catches any type of use-after-free including double-free?
While writing a blog post (below) I went through the documentation to figure out the possible runtime memory safety checks Zig can insert. The term "use-after-free" or "UaF" never occurs on that documentation page. Searching for "safety-checked" doesn't yield any related hits either.
Unless maybe they're using the DebugAllocator in release builds? Even that does not reliably surface UaF.
I as someone with writing Zig a bunch, can safely say if it does it hasn't even worked for me.
I am talking from experience from a pre-ai human mitts writing code perspective maybe Zig + LLMs do some magic.
The more I read the article the more I feel like this is just bad not sure if I should be giving it as much latitude as I have been in my prior comments.
There are other claims as well that are weirdly phrased at least.
Reads like an article written to justify some arguments they had rather than a genuine take at this point.
But I will give the benefit of doubt I enjoy weird articles, languages and share a dislike for aggressive AI-ness of all things.
Interesting that OCaml was flexible and expressive enough to be used as a prototype testbed but not chosen as the implementation language, especially given the maturity of both. I would be surprised if Zigs incremental builds could be meaningfully faster than dune's.
Cross compilation is great, but not mentioned in the "why Zig" section. Is memory control that crucial for a compiler?
Rust itself was originally written in OCaml, same with WASM. I'm curious about what milestone gets reached where the maintainers collectively decide to transition away.
Zig is a pre-1.0 language while Rust is post-1.0. This alone is settles which one to pick for may developers. The library support is probably favours Rust too. Rust build times are much slower than Zig, I get that, but I rarely optimize software for build times.
Zig is not pre-1.0 because it’s not ready for production (bugs or missing features), it’s pre-1.0 because they want to be able to make breaking language changes.
Nowadays when you can just point an agent at release notes and have it update everything, I actually prefer not having to wait through rare major releases to get new language features.
> Nowadays when you can just point an agent at release notes and have it update everything
Except that means that not only you lose compiler bugfixes, you also pretty much has no access to the ecosystem. For most production codebases, this is a deal breaker.
I invite you to read the release notes and see for yourself the types of breaking changes we’re talking about.
To me it is not much different from Lua, which despite being on 5.x for decades, makes breaking changes on minor releases (because it predates SemVer).
I also don’t see it being much different from any other language or language runtime that has a major release every year.
> Zig is not pre-1.0 because it’s not ready for production (bugs or missing features), it’s pre-1.0 because they want to be able to make breaking language changes.
This is a solved problem in other projects. Either use the version numbers as intended and bump the major version number on breaking changes, or use Rust-style editions to opt in to the newer versions of the changes.
Calling a project production-ready but keeping the version number below 1.0 and saying breaking changes are expected is a tired game. We've seen it backfire across a number of language projects like Elm, where the exact same claim was used to both encourage people to use it and then blame them when it backfired.
If it's production ready, go to 1.0 and then follow semver for breaking changes. I don't care if we get to Zig v73.2.0 as a result. At least we can see from a glance which versions need to be checked for breaking changes.
One thing I wish Rust would improve over time is the builds. Its one of the biggest sources of wasted storage space on all my computers, builds a ton of libraries can take tens of gigs, it adds up very quickly. Not sure what the best solution is, one I found is to set the global build folder so dependencies get reused across projects, but imho it should be an OOTB default behavior whatever the real solution should be.
Rust isn't great, and it shouldn't be a surprised since it's designed after npm. However one metric where nodes_modules is still worse for me is the sheer number of small files in it.
Having nearly one million files in nodes_modules isn't that unusual. The problem is that on most common file systems the minimum allocation is usually at least 4KB. So even if the actual data is less than 500MB, you end up with 4GB disk space used/wasted.
I wish ext4 had a feature to mark a file as "atomic" where it would allocate all atomic files in a long run, without room for expansion, and I suppose with very inefficient compaction upon deletion, but without any padding bytes.
We are trading away disk space for faster builds. We could make them faster in some cases by using even more...
On the other hand, it would be good to garbage collect those caches. We are wrapping up work on a new layout for intermediate build artifacts that will make it easier to GC them.
Sounds like what I was thinking, that or for third party deps to go into the same temp folder, and anything not accessed in over a week, or so just gets auto wiped by rustc / cargo build process?
The compiler is one of the most significant trust boundaries we have. Its decisions can intentionally or unintentionally create vulnerabilities in programs compiled by the compiler, which means that if you can compromise a compiler you can compromise everything downstream.
Unsafe memory access in a compiler can be exploited in order to hijack the compiler itself (this is reported regularly in production compilers), allowing the attacker to then insert arbitrary code into compiled binaries. Not everything that a compiler absorbs from its environment is meant to be treated as source to be compiled, and in a memory unsafe compiler any of that input can silently turn into machine code in the compiled binary if an attacker is able to exploit the memory safety bug and hijack the compiler.
I don't even know what Zig is but I've seen this topic come up so many times on this site that I'm starting to think the people who are actually doing this are unsure themselves whether it's a good idea or not.
While I'm a rust enthusiast, I do agree that certain languages lend themselves well to particular domains. So a rewrite from Rust to something better suited is fine by me. In fact, while I do work on a rust project, I would not have and still would not recommend it as the choice for that particular project.
That being said, I had to do some double takes while reading this.
I feel that it's a bit weird to compare a rather well tested 7 (?) year old rust implementation with a brand new not yet released less than a year old Zig implementation. Without that context, this looks like a bad comparison for rust, when it is in fact the complete opposite.
The swiftness of the Zig compilere here is insane, and would would very much shift my recommendation of Rust if it got to similar speeds.
That being said, I do find it funny that currently, the compilation speed is actually worse on Zig than Rust, despite Zig (anonymous commenters at least tbd) claiming the opposite for years.
How did you eventually discover the 35 ms figure for Roc? Did you have to temporarily update the codebase to 0.17?
Nothing negative here. I did play around with implementing a scripting language in this DOD-ish, index-based paradigm and yeah, it is neat.
I was thinking that it might be possible to do resumable computation across the network like this (in the context of frontend frameworks "resuming" UIs), but ultimately I have no use for this so just the experience itself was enough.
One note here is that it does tend to break completely if non-pointer-free data is introduced. It seems like it's either all or nothing.
> In fact, while I do work on a rust project, I would not have and still would not recommend it as the choice for that particular project.
wondering what type of project is that? I think besides some very embedded projects with very little memory where you need C/assembly, rust is good enough for all kind of projects..
I work both on a pretty much bog-standard web (GraphQL) backend and the frontend that uses it. We switched over from Apollo on node to async-graphql on Rust.
The runtime performance is much better, but the compiler time performance is terrible. To be fair, this is mostly the fault of async-graphql, but that doesn't really matter all that much. For example, it's not uncommon for a single character SQL query change to trigger over a minute long incremental rebuild.
The rust compiler is just choking on the number of generics and codegenned functions.
I've personally looked at how to improve this, but short of breaking up the type graph using federation, nothing can help. Not even cranelift makes a noticeable dent.
Additionally, the team started off composed by a bunch of TypeScript/React/Node developers, so mistakes were made along the way.
Honestly, I would have recommended to just use C#.
That's not to say that I don't think Rust can work for web development. We have some (GraphQL-less) services where Rust is a great fit. Just maybe shouldn't have been the default. That or give up graphql ...
I am not sure, but there might be a bug in their pattern matching example.
What happens if 'verb' is "GET" and 'path' is "/users/1234/posts/1234/extra_path/and/more/"? Will 'post_id' become "extra_path/and/more/"?
I tried running it in the sandbox, and it does indeed seem to buggily result in:
"Post ID: 1234/extra_path/and/more"
I suspect that the reason it is behaving like it is, is due to how it handles characters in the string literal. The example program exploits that only the slashes present in the string literal pattern are matched, to enable matching on 'page' having slashes. But then in the nested 'match', it forgot to account for any possible extra slashes.
Nitpicking end.
I have not read the whole post yet, but the pattern matching not requiring any allocations, seems very nice. The string literal patterns also seem interesting, though I am not completely sold on them, also as per the above possible bug. It seems really clean in some ways, but the specific semantics, I am not fully sure about. Maybe it is excellent, and is so clean and concise that it is overall less bug-prone than alternatives in other programming languages. I do not know.
Irrespective to the technical merits of both language, moving from a stable language to a pre-1.0 one that just lost his most popular open source project is a wild move.
> that just lost his most popular open source project
As they state in the article, they started the migration a year and a half ago, something that happened a few weeks back would never come into the decision making process.
This piece would have been a lot more compelling if they had actually done science on selecting a language for compiler development. From what I can tell, they had an untested hypothesis that a low level systems language is necessary for a high performance compiler https://www.roc-lang.org/faq#self-hosted-compiler and from that concluded that their only
choice besides rust was zig.
I know from experience that this initial assumption is wrong. Compiler performance is dominated by algorithms. The fastes managed languages tend to be at worst within a factor of two for wall time on any given algorithm. Algorithmic differences can be unbounded in their performance gaps. Zig itself is a perfect counterexample to the theory that writing a compiler in a low level systems language will lead to a fast compiler. Roc seems to compile at around 15k lines per second. That is not fast. There were evidently compilers written in ml that did 3k likes per second in 1998 https://flint.cs.yale.edu/cs421/case-for-ml.html
The zig rewrite of roc looks like the author's second compiler. Compiler and language design is a skill like any other and from my vantage point, they appear to have overcommitted to an initial design at the expense of developing their higher level design skills. In my opinion, the best thing they could do for the future of roc is stop working on their current compiler and use it to write a self hosting compiler for a much smaller subset of roc. They should be able to do that in less than 10k lines of code. They might even find that their self hosting compiler is faster than their zig based bootstrap compiler for the self hosted subset of roc. If the self hosting compiler is inadequate. Now they at least have identified a smaller useful subset of roc and can experiment with different compiler implementations in 10k likes of code rather than 300k lines of code. Then they could actually test the theory of whether or not a low level language is necessary to meet whatever arbitrary compiler performance goals they have.
By self hosting, they would also discover what roc features actually matter and they would spend much more time actually writing roc code. The features that are needed to write a self hosted compiler are all features that are generally useful. By improving the self hosted compiler, they also improve downstream programs.
Your comment is very assertive, but also doesn't offer much in the way of science.
Being able to compile ML quickly in the 90s tells you little about being able to compile Roc or some other language today because the language design enforces hard constraints on the algorithms necessary to compile it and the hardware today is much more complex. It's not hard to write a fast Pascal compiler that targets a 1980s chip with shallow pipelines. But that's not the problem being solved here.
I don't know much about Roc but it looks like it's got some amount of overloading and the linked article alludes to sophisticated algorithms to avoid heap allocating closures. Those can enforce algorithmic complexity in the compiler that is essential and can't be eliminated.
Once you're at the limits of algorithmic optimization, all that's left is reducing constant factors. I've written code in many languages in different performance regimes over the years and it's certainly the case that higher level languages, especially managed memory ones, put a hard floor in terms of how low you can go when optimizing to improve those constant factors.
I have seen in real-world code where explicit control over memory layout improved performance by more than an order of magnitude. I have friends in the game industry where much of their career is this kind of work. Those people would love to live in the luxurious world you describe where all they need to do is find a sufficiently clever algorithm and all of their performance problems will disappear.
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[ 1.8 ms ] story [ 320 ms ] threadI was fine with basic generics they complicated it quite a bit much for my liking.
It's doable, and as static analysis. see sibling comment.
The reason Rust has a working borrow checker is because every part of the language from structs, enum, traits, generics and all the way to the syntax itself has been designed to support lifetimes and borrow checking.
It's is not something you can just tack on to an existing language without fundamentally changing it.
Why do you say that. Have you tried and failed? It seems to be possible to add a borrow checker to zig, just as you can add MIRI to rust to get extra safety in unsafe blocks.
i periodically throw my unused codex tokens at this:
https://github.com/ityonemo/clr
Most of the goals on this page are targeted for this year.
> remember that for compilers which emit machine code, like roc and rustc, doing memory-unsafe things is a big part of the job
I don't really think that this is true, in the way that it's written.
I think that for the hot binary patching / code reloading features, yes, that is going to need unsafe. But for regular old "producing an executable" compilation? Emitting machine code isn't the part that requires unsafe. The language's runtime is a more likely site to find unsafe.
If anything, compilers are perfect models of trees and well formed programs.
In this respect, effectively all the compiler should be treated as an unsafe region that requires extra care to avoid memory corruption bugs.
> we ended up with about 1,200 uses of unsafe
> remember that for compilers which emit machine code, like roc and rustc, doing memory-unsafe things is a big part of the job
> Regardless of which process had the bug—the compiler or compiled program—in both cases the processor only did the bad thing because the compiler told it to. And in both cases the fix is the same: the compiler's code must change, since that code was what caused the memory corruption.
But yeah, I wonder what those 1,200 unsafe uses actually did?
I don't think that's any different either. The core job of linking isn't particularly unsafe.
(Unless, similarly, you're doing the hot reloading stuff)
It is only relatively recently that we have gained more realistic options in these spaces, and so not fully understanding the implications, or preferring the historically normal choices, is understandable.
1. Foundational for other forms of safety
2. Has an objective definition, when some other forms of safety are either subjective or inter-subjective.
That said, I don't understand why your parent brought this up to you, you are talking about memory safety in your original comment here, so that's what Rust's safety is about.
Because a “very specific form of safety” is a useful tool in achieving “safety in general”
Because a “very specific form of safety” is tractable for a compiler and language runtime to achieve, “safety in general” isn’t
This is impossible. General words like "safe" and "good" are subjective, and useless in a technical context unless you ground the discussion by giving them specific definitions. Otherwise everyone ends up talking past each other.
This is a core perspective disagreement. While this is true:
> If your system gets hacked by a buffer overflow in the end, nobody cares whether it was the linker that overflowed or the code emitted by the linker.
That does not mean that increasing the amount of safety in the individual components isn't helpful, because it helps minimize the above outcome, even if it will never be zero.
The compiler itself might be perfectly "memory safe" but the generated binary fundamentally is always at risk.
I am also probably in a more pedantic mindset because, well, I'm writing a compiler in Rust, and the words as written do not resonate with me at all.
> a perfectly safe compiler that generates vulnerable binaries isn't that much better.
I do think it's much better. Eliminating classes of bugs in one component is a good thing, even if it's not every component. This is a core lesson of Rust! unsafe still exists, but going from "I don't know what is unsafe" to "only this part is unsafe" is a major improvement.
> Zig has more features than Rust for making memory-unsafe code work correctly, and that was the area where we wanted the most help.
Zig definitely does not have more features for successfully emitting memory-unsafe machine code than Rust does. I can emit memory-unsafe machine code from typescript if I really want to and nothing at all in the language will get in my way. So the sentence quoted above must refer to the idea that the compiler itself needs to be unsafe, which Steve is right is simply untrue.
It's not about the memory safety of the resulting binary.
Agreed! Emitting machine code is not unsafe, since it's just writing bytes down - it's only once you execute that machine code that there's potentially unsafety. The reason I said "a big part of the job" is that in practice a lot of compilers both emit machine code and execute it - but you're totally right that it's not a requirement that a compiler do both.
In addition to the examples you gave (hot binary patching/code reloading, language runtime, etc.), others would be things like evaluating userspace code at compile time (e.g. const fn in Rust, or in Roc any expression that could be hoisted to the top level), running tests and inspecting their output to decide what to display to the user, etc.
Those are the types of things I had in mind when I wrote that.
I also think it's a good thing that you wrote the post in general, when I saw it pop up I was like "oh, of course, this post should exist!" I'm surprised I didn't think about it earlier.
> evaluating userspace code at compile time
Usually this would be done via an interpreter, so I'm not sure that it really requires unsafe either. If you are literally executing machine code, sure, but const fn in Rust and constexpr in C++ and many other languages do not do that, as it causes a number of problems (for example, cross-compilation).
By the way, I thought your question was totally reasonable - my first thought reading it was "Oh yeah I wasn't trying to say that writing bytes is unsafe, I definitely should have worded that differently."
> rustc emits machine code and then cargo immediately executes it, there's the same opportunity for end user memory being corrupted (due to miscompilation) as if rustc and cargo shared a code base.
Cause this hasn't been true for me or for anyone maybe your definition of memory being corrupted is the not same as mine.
I am not even sure what you are trying to prove with this.
I appreciate the time and effort in building stuff like Roc I don't use it but this comment and the article feel like...
Oh some guy said Zig not nice because memory safety so here, a post why memory safety doesn't exist because we have to do memory unsafe things sometimes and so everything is memory unsafe already, so maybe it doesn't matter.
I get the energy that we are going for seeing useless claims and wanting to push back but I think the article deserves a clearer part 2 where you elaborate on your thoughts about stuff maybe even get it peer reviewed a bit before posting or maybe don't I guess we could use more raw thoughts in the post AI age.
Either way I appreciate someone trying to put forward their own thoughts and explain problems with a different perspective.
> although of course that wouldn't work for running tests.
Why not? Unless you mean in the cross-compilation case, in which yeah, to run the compiled tests you'd need an emulator.
> in the specific case of Rust I believe rustc only compiles the tests and then something else like Cargo executes them.
It doesn't have to be Cargo, but yes, rustc produces executables for the tests, and you have to then run them.
> there's the same opportunity for end user memory being corrupted (due to miscompilation)
I agree for sure that the safety of the outputted binary is completely distinct from the safety of the compiler itself.
I think the reason that this framing specifically (in the post and in this comment) strikes me as odd is that "requires unsafe code" sort of implies that you need to use unsafe to fix the unsafety of the outputted binary. That just isn't the case. Of course, this is a serious bug that needs to be fixed, but there's just something about "doing memory unsafe things" in this area that like, I think can be a little mis-leading, even if that's not intentional. But I am going to sit with this and think about it, regardless, because I am not sure that my gut reaction here is completely accurate.
(And, hilariously, looking over some work my agents did on my compiler last night, they fixed some mis-compilations that occurred, entirely in safe code. I bet that's also part of why I'm in this headspace at the moment, it's not like those fixes required dropping down into unsafe to fix either!)
Your tests run in an entirely separate process from the compiler (and from cargo). This makes it very different from memory corruption in the compiler:
- The test process can only corrupt its own memory.
- You don't need "unsafe" to run tests. Just the ability to start another process.
- If you're cross-compiling, you wouldn't even be able to run the tests on the same machine (without emulation/compatibility layers)
Does roc run tests in the same process as the compiler?
In extremely high performance code you use different data structures and algorithms and change your approach to memory allocation. TigerBeetle famously does all memory allocation once on startup.
Roc is attempting to make a similar set of trade-offs in their compiler as Zig, so it makes sense that the author finds many shared patterns.
It is like someone arguing that since they always bump the head somehow while wearing seatbelts, then they are only a nuisance and should not be used.
I don't know Zig so maybe they know something I don't, but I have seen no evidence that it catches any type of use-after-free including double-free?
While writing a blog post (below) I went through the documentation to figure out the possible runtime memory safety checks Zig can insert. The term "use-after-free" or "UaF" never occurs on that documentation page. Searching for "safety-checked" doesn't yield any related hits either.
Unless maybe they're using the DebugAllocator in release builds? Even that does not reliably surface UaF.
https://landaire.net/memory-safety-by-default-is-non-negotia...
I think ReleaseSafe just adds bound checking and panics on unreachable code.
I don't think Zig offers any temporal memory safety.
I am talking from experience from a pre-ai human mitts writing code perspective maybe Zig + LLMs do some magic.
The more I read the article the more I feel like this is just bad not sure if I should be giving it as much latitude as I have been in my prior comments.
There are other claims as well that are weirdly phrased at least.
Reads like an article written to justify some arguments they had rather than a genuine take at this point.
But I will give the benefit of doubt I enjoy weird articles, languages and share a dislike for aggressive AI-ness of all things.
Cross compilation is great, but not mentioned in the "why Zig" section. Is memory control that crucial for a compiler?
Rust itself was originally written in OCaml, same with WASM. I'm curious about what milestone gets reached where the maintainers collectively decide to transition away.
Rust is also one of the best languages to use with AI.
Nowadays when you can just point an agent at release notes and have it update everything, I actually prefer not having to wait through rare major releases to get new language features.
Except that means that not only you lose compiler bugfixes, you also pretty much has no access to the ecosystem. For most production codebases, this is a deal breaker.
That sounds like it's not ready for production to me.
To me it is not much different from Lua, which despite being on 5.x for decades, makes breaking changes on minor releases (because it predates SemVer).
I also don’t see it being much different from any other language or language runtime that has a major release every year.
It’s fine to update at your own pace.
This is a solved problem in other projects. Either use the version numbers as intended and bump the major version number on breaking changes, or use Rust-style editions to opt in to the newer versions of the changes.
Calling a project production-ready but keeping the version number below 1.0 and saying breaking changes are expected is a tired game. We've seen it backfire across a number of language projects like Elm, where the exact same claim was used to both encourage people to use it and then blame them when it backfired.
If it's production ready, go to 1.0 and then follow semver for breaking changes. I don't care if we get to Zig v73.2.0 as a result. At least we can see from a glance which versions need to be checked for breaking changes.
My Tauri project, where the backend is much smaller code-wise than the frontend, has 9gb of rust artifacts (node_modules is 550mb for comparison)
Having nearly one million files in nodes_modules isn't that unusual. The problem is that on most common file systems the minimum allocation is usually at least 4KB. So even if the actual data is less than 500MB, you end up with 4GB disk space used/wasted.
On the other hand, it would be good to garbage collect those caches. We are wrapping up work on a new layout for intermediate build artifacts that will make it easier to GC them.
If I want to use allocator debuggers I already have the production ready tools that exist for C and C++ for at least 30 years.
And as mentioned, if what Zig offers is already in Purify, there is hardly any added value over C and C++, without the headaches of a niche language.
The compiler is one of the most significant trust boundaries we have. Its decisions can intentionally or unintentionally create vulnerabilities in programs compiled by the compiler, which means that if you can compromise a compiler you can compromise everything downstream.
Unsafe memory access in a compiler can be exploited in order to hijack the compiler itself (this is reported regularly in production compilers), allowing the attacker to then insert arbitrary code into compiled binaries. Not everything that a compiler absorbs from its environment is meant to be treated as source to be compiled, and in a memory unsafe compiler any of that input can silently turn into machine code in the compiled binary if an attacker is able to exploit the memory safety bug and hijack the compiler.
Some folks embrace it as some kind of novelty.
That being said, I had to do some double takes while reading this.
> https://rtfeldman.com/rust-to-zig#memory-safety-post-rewrite
I feel that it's a bit weird to compare a rather well tested 7 (?) year old rust implementation with a brand new not yet released less than a year old Zig implementation. Without that context, this looks like a bad comparison for rust, when it is in fact the complete opposite.
> https://rtfeldman.com/rust-to-zig#build-times
The swiftness of the Zig compilere here is insane, and would would very much shift my recommendation of Rust if it got to similar speeds.
That being said, I do find it funny that currently, the compilation speed is actually worse on Zig than Rust, despite Zig (anonymous commenters at least tbd) claiming the opposite for years.
How did you eventually discover the 35 ms figure for Roc? Did you have to temporarily update the codebase to 0.17?
> https://rtfeldman.com/rust-to-zig#memory-control-zero-parse-...
Nothing negative here. I did play around with implementing a scripting language in this DOD-ish, index-based paradigm and yeah, it is neat.
I was thinking that it might be possible to do resumable computation across the network like this (in the context of frontend frameworks "resuming" UIs), but ultimately I have no use for this so just the experience itself was enough.
One note here is that it does tend to break completely if non-pointer-free data is introduced. It seems like it's either all or nothing.
> https://rtfeldman.com/rust-to-zig#ecosystem-relevance
This is more of an LLM thing, which is fair, but I find it funny that "LLVM unstable bad" and "Zig unstable whatever".
Overall though, this was an interesting read. And if the folks contributing to roc like zig then more power to them.
Last thing, the link here is broken (points to a TODO):
> Zig's compiler itself is another
wondering what type of project is that? I think besides some very embedded projects with very little memory where you need C/assembly, rust is good enough for all kind of projects..
The runtime performance is much better, but the compiler time performance is terrible. To be fair, this is mostly the fault of async-graphql, but that doesn't really matter all that much. For example, it's not uncommon for a single character SQL query change to trigger over a minute long incremental rebuild.
The rust compiler is just choking on the number of generics and codegenned functions.
I've personally looked at how to improve this, but short of breaking up the type graph using federation, nothing can help. Not even cranelift makes a noticeable dent.
Additionally, the team started off composed by a bunch of TypeScript/React/Node developers, so mistakes were made along the way.
Honestly, I would have recommended to just use C#.
That's not to say that I don't think Rust can work for web development. We have some (GraphQL-less) services where Rust is a great fit. Just maybe shouldn't have been the default. That or give up graphql ...
I am not sure, but there might be a bug in their pattern matching example.
What happens if 'verb' is "GET" and 'path' is "/users/1234/posts/1234/extra_path/and/more/"? Will 'post_id' become "extra_path/and/more/"?
I tried running it in the sandbox, and it does indeed seem to buggily result in:
"Post ID: 1234/extra_path/and/more"
I suspect that the reason it is behaving like it is, is due to how it handles characters in the string literal. The example program exploits that only the slashes present in the string literal pattern are matched, to enable matching on 'page' having slashes. But then in the nested 'match', it forgot to account for any possible extra slashes.
Nitpicking end.
I have not read the whole post yet, but the pattern matching not requiring any allocations, seems very nice. The string literal patterns also seem interesting, though I am not completely sold on them, also as per the above possible bug. It seems really clean in some ways, but the specific semantics, I am not fully sure about. Maybe it is excellent, and is so clean and concise that it is overall less bug-prone than alternatives in other programming languages. I do not know.
As they state in the article, they started the migration a year and a half ago, something that happened a few weeks back would never come into the decision making process.
I know from experience that this initial assumption is wrong. Compiler performance is dominated by algorithms. The fastes managed languages tend to be at worst within a factor of two for wall time on any given algorithm. Algorithmic differences can be unbounded in their performance gaps. Zig itself is a perfect counterexample to the theory that writing a compiler in a low level systems language will lead to a fast compiler. Roc seems to compile at around 15k lines per second. That is not fast. There were evidently compilers written in ml that did 3k likes per second in 1998 https://flint.cs.yale.edu/cs421/case-for-ml.html
The zig rewrite of roc looks like the author's second compiler. Compiler and language design is a skill like any other and from my vantage point, they appear to have overcommitted to an initial design at the expense of developing their higher level design skills. In my opinion, the best thing they could do for the future of roc is stop working on their current compiler and use it to write a self hosting compiler for a much smaller subset of roc. They should be able to do that in less than 10k lines of code. They might even find that their self hosting compiler is faster than their zig based bootstrap compiler for the self hosted subset of roc. If the self hosting compiler is inadequate. Now they at least have identified a smaller useful subset of roc and can experiment with different compiler implementations in 10k likes of code rather than 300k lines of code. Then they could actually test the theory of whether or not a low level language is necessary to meet whatever arbitrary compiler performance goals they have.
By self hosting, they would also discover what roc features actually matter and they would spend much more time actually writing roc code. The features that are needed to write a self hosted compiler are all features that are generally useful. By improving the self hosted compiler, they also improve downstream programs.
Being able to compile ML quickly in the 90s tells you little about being able to compile Roc or some other language today because the language design enforces hard constraints on the algorithms necessary to compile it and the hardware today is much more complex. It's not hard to write a fast Pascal compiler that targets a 1980s chip with shallow pipelines. But that's not the problem being solved here.
I don't know much about Roc but it looks like it's got some amount of overloading and the linked article alludes to sophisticated algorithms to avoid heap allocating closures. Those can enforce algorithmic complexity in the compiler that is essential and can't be eliminated.
Once you're at the limits of algorithmic optimization, all that's left is reducing constant factors. I've written code in many languages in different performance regimes over the years and it's certainly the case that higher level languages, especially managed memory ones, put a hard floor in terms of how low you can go when optimizing to improve those constant factors.
I have seen in real-world code where explicit control over memory layout improved performance by more than an order of magnitude. I have friends in the game industry where much of their career is this kind of work. Those people would love to live in the luxurious world you describe where all they need to do is find a sufficiently clever algorithm and all of their performance problems will disappear.