[JuniperMesos]

> It's not memory safe like Rust is, but it comes with constructs that make it simple to build largely memory safe programs.

Right, this is the specific important thing that Rust does that Zig doesn't (with the caveat that Rust includes the `unsafe` mechanism - as a marked, non-default option - specifically to allow for necessary low-level memory manipulation that can't be checked for correctness by the compiler). Being able to guarantee that something can't happen is more valuable than making it simple to do something correctly most of the time.

[dns_snek]

It's not that simple though, Zig has equivalent spatial memory safety which prevents issues that are pretty consistently among (or at) the top of the list for most dangerous vulnerability classes.

And while I don't have enough experience with Rust to claim this first hand, my understanding is that writing correct unsafe Rust code is at least an order of magnitude harder than writing correct Zig code due to all of the properties/invariants that you have to preserve. So it comes with serious drawbacks, it's not just a quick "opt out of the safety for a bit" switch.

> Being able to guarantee that something can't happen is more valuable than making it simple to do something correctly most of the time.

Of course, all other things being equal, but they're not.

[goku12]

> And while I don't have enough experience with Rust to claim this first hand, my understanding is that writing correct unsafe Rust code is at least an order of magnitude harder than writing correct Zig code due to all of the properties/invariants that you have to preserve.

How do you make such boldly dismissive assertions if you don't have enough experience with Rust? You are talking as if these invariants are some sort of requirements/constraints that the language imposes on the programmer. They're not. It's a well-known guideline/paradigm meant to contain any memory safety bugs within the unsafe blocks. Most of the invariants are specific to the problem at hand, and not to the programming language. They are conditions that must be met in any language - C and Zig are no exceptions. Failure to adhere to them will land you in trouble, no matter what sort of safety your language guarantees. They are often talked about in the context of Rust because the ones related to memory-unsafe operations can be tackled and managed within the small unsafe blocks, instead of being sprawling it throughout the code base.

> So it comes with serious drawbacks, it's not just a quick "opt out of the safety for a bit" switch.

Rust is not the ultimate solution to every problem in the world. But this sort of exaggeration and hyperbole is misleading and doesn't help anyone choose any better.

[dns_snek]

> How do you make such boldly dismissive assertions

As I said that's my understanding from talking and listening to people who have a lot of experience with Rust, Zig, and C.

So generally speaking, are you saying that writing correct unsafe Rust is only as difficult as writing correct Zig code and not, as I understand it to be, significantly more difficult?

[NobodyNada]

If no references are involved, writing unsafe Rust is significantly easier than writing correct C, because the semantics are much clearer and easier to find in the documentation, and there's no insane things like type-based aliasing rules.

If references are involved, Rust becomes harder, because the precise semantics are not decided or documented. The semantics aren't complicated; they're along the lines of "while a reference is live, you can't perform a conflicting access from a pointer or reference not derived from that reference". But there aren't good resources for learning this or clarifying the precise details. This area is an active work-in-progress; there is a subteam of the Rust project led by Ralf Jung (https://www.ralfj.de/blog/) working on fully and clearly defining the language's operational semantics, and they are doing an excellent job of it.

When it comes to Zig, the precise rules and semantics of the memory model are much less clear than C. There's essentially no documentation, and if you search GitHub issues a lot of it is undecided and not actively being worked on. This is completely understandable given Zig's stage in development, but for me "how easy it is to write UB-free code" boils down to "how easy is it to understand the rules and apply them correctly", and so to me Zig is very hard to write correctly if you can't even figure out what "correct" is.

Once Zig and Rust both have their memory models fleshed out, I hope Zig lands somewhere comparable to where Rust-without-references is today, and I hope that Rust-with-references ends up being only a little bit harder (and still easier than C).

[goku12]

> So generally speaking, are you saying that writing correct unsafe Rust is only as difficult as writing correct Zig code and not, as I understand it to be, significantly more difficult?

Yes. That's correct. The point is, unsafe Rust is pretty unremarkable. Safe Rust doesn't just do borrow checking of references. It also forbids certain risky actions like raw pointer indirection or calling unsafe functions (across FFI, for example) [1]. Unsafe Rust just enables those features. That's it! Unsafe Rust doesn't disable anything or impose any additional restrictions. Contrary to a popular misconception, it doesn't even disable the borrow checker. Unsafe Rust actually gives you extra freedoms on top of what you already have (including the restrictions).

And now you have to be careful because Rust just gave you a footgun that you asked for. In a manually memory-managed language, you'd get fatigued by the constant worry about this footgun. In Rust, that worry is limited to those unsafe blocks, giving you the luxury to workout strategies to avoid shooting yourself in the foot. The 'invariants' are that strategy. You describe the conditions under which the code is valid. Then you enforce it there, so that you can breath freely in Safe Rust.

[1] https://doc.rust-lang.org/nomicon/what-unsafe-does.html#what...

[JuniperMesos]

> And while I don't have enough experience with Rust to claim this first hand, my understanding is that writing correct unsafe Rust code is at least an order of magnitude harder than writing correct Zig code due to all of the properties/invariants that you have to preserve. So it comes with serious drawbacks, it's not just a quick "opt out of the safety for a bit" switch.

I think this is hard to generalize about. There are many instances where one might want to do unsafe memory operations in rust, with different correctness implications. I am suspicious that in Zig you do actually have to preserve all the same properties and invariants, and there's just nothing telling you if you did so or not or even what all of them are, so you don't know if your code is correct or not.

[ViewTrick1002]

I would compare the recent Rust Android post [1], where they have a 5000x lower memory vulnerability rate compared to traditional C/C++ with the number of segfaults found in Bun. [2]

In my opinion Zig does not move the needle on real safety when the codebase becomes sufficiently complex.

[1]: https://security.googleblog.com/2025/11/rust-in-android-move...

[2]: https://github.com/oven-sh/bun/issues?q=segfault%20OR%20segm...

[dns_snek]

Why are we comparing a number of exploitable vulnerabilities to the number of segfault reports? Where does the "5000x" figure come from?

[ViewTrick1002]

The number is memory vulnerabilities. Not if they are exploitable. The numbers comes from this part of the article:

    This near-miss inevitably raises the question: "If Rust can have memory safety vulnerabilities, then what’s the point?"

    The point is that the density is drastically lower. So much lower that it represents a major shift in security posture. Based on our near-miss, we can make a conservative estimate. With roughly 5 million lines of Rust in the Android platform and one potential memory safety vulnerability found (and fixed pre-release), our estimated vulnerability density for Rust is 0.2 vuln per 1 million lines (MLOC).

    Our historical data for C and C++ shows a density of closer to 1,000 memory safety vulnerabilities per MLOC. Our Rust code is currently tracking at a density orders of magnitude lower: a more than 1000x reduction. 

https://security.googleblog.com/2025/11/rust-in-android-move...

[dns_snek]

Then someone's playing with definitions here because a bug that can't be exploited and doesn't have a demonstrable impact on safety or security isn't a vulnerability under any definition that I subscribe to - it's just a bug.

What we ultimately care about is how many preventable, serious defects sneak into production code - particularly those concerning data security, integrity, and physical safety. The only statistics we should all care about is how many serious CVEs end up in the final product, everything else is just personal preference.

Eliminating a segfault when `--help` is provided twice is nice, but it didn't fix a security vulnerability so using it to bolster the security argument is dishonest.

[sgt]

Sure but there's this belief in the Rust community that it's not responsible anymore to write software that isn't memory safe on the same level as Rust.

So Zig would fail that, but then you could also consider C++ unsuitable for production software - and we know it clearly is still suitable.

I predict Zig will just become more and more popular (and with better, although not as complete- memory safety), and be applied to mission critical infra.

[pjmlp]

If we ignore recent movents in govermental cybersecurity agencies, and big tech to move away from unsafe programming languages, as much as technically possible.

Introducing a language with the same safety as Modula-2 or Object Pascal, would make sense in the 1990's, nowadays with improved type systems making the transition from academia into mainstream, we (the industry) know better.

It is not only Rust, it is Linear Haskell, OCaml effects, Swift 6 ownership model, Ada/SPARK, Chapel,....

[sgt]

Of those listed, I'd bet Swift (having had experience with it) is the most pleasant to work with. I just hope it takes off on the systems and backend side at some point.

[ModernMech]

Swift's main problem is that Apple is holding it back but also it'd be nothing without Apple's involvement.

[JuniperMesos]

> So Zig would fail that, but then you could also consider C++ unsuitable for production software - and we know it clearly is still suitable.

Speak for yourself, I never want to write C++ ever again in my life.

I'm not a huge fan of the language of responsibility. I don't think there should be a law banning the use of C or C++ or any other programming language on account of it being unsafe, I don't think that anyone who writes in C/C++ is inherently acting immorally, etc.

What I do think is that Rust is a better-designed language than C or C++ and offers a bunch of affordances, including but not limited to the borrow checker, unsafe mode, the type system, cargo, etc. that make it easier and more fun for programmers to use to write correct and performant software, most of the time in most cases. I think projects that are currently using C/C++ should seriously consider switching off of them to something else, and Rust is an excellent candidate but not the only candidate.

I think Zig is also almost certainly an better language than C/C++ in every respect (I hedge more here because I'm less familiar with Zig, and because it's still being developed). Not having as strong memory safety guarantees as Rust is disappointing and I expect that it will result in Zig-written software being somewhat buggier than Rust-written software over the long term. But I am not so confident that I am correct about this, or that Zig won't bring additional benefits Rust doesn't have, that I would argue that people shouldn't use Zig or work on languages like Zig.