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Comment by awesan | Hacker News Reader

Zig (like C) is simply not a good language to use if you're going to do many small allocations with uncorrelated lifetimes. To write robust Zig (or C) code, you must manage lifetimes yourself, for example by grouping allocations on an arena or by having fixed buffers of "things".

You can just do that, and then Zig is really no less robust than Rust. But if you want to do "managed language" style allocation patterns (like what llms generally prefer), it doesn't make sense to use it.

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Grouped and arena allocations work really well in Zig. For awhile, we tried to use this pattern almost everywhere in Bun but it gets really tricky when there’s some GC-managed memory and you want to free things incrementally to reduce RSS. Also, using arenas for arrays that grow wastes memory a lot since it keeps every previous version around (mimalloc arenas are slightly better for this)

Grouped allocations works especially well in parsers & ASTs where the lifetime is very bounded. Since the Rust rewrite, we still use arenas for Bun’s parsers and the bundler but not a ton elsewhere.

> using arenas for arrays that grow wastes memory a lot since it keeps every previous version around

Not if you use segmented arrays

https://danielchasehooper.com/posts/segment_array/

> You can just do that, and then Zig is really no less robust than Rust.

If you just don't write bugs, then yes all languages are equally robust, including assembly.

Zig, like C, is simply not a robust language. I don't know why this feels like something contentious? It's clearly not intended to be robust?

Above poster is talking about thinking in terms of grouped lifetimes and bulk allocations/deallocations, which is better for performance, and makes Rust borrow checking and other RAII style features pointless as they don't add any safety benefits. This video completely changed the way I think, and I subsequently moved on from Rust: https://www.youtube.com/watch?v=xt1KNDmOYqA

Zig is intended to be as robust as it can be as long as it doesn’t implicitly add code (no destructors that run code you didn’t explicitly call), or increase compiler complexity and compilation time.

I don’t think it makes sense to say Zig is or isn’t intended to be robust in general. Like, we don’t say Rust isn’t robust since it doesn’t add dependent types and general purpose static verification that can do more general proofs. It’s focused on eliminating one class of memory bugs in particular, exactly the class of bugs that are the biggest challenge for software like Bun, and other software with complex lifetimes (it originated from Mozilla and Rust is perfect for browsers)

Zig is intended to be robust for software like TigerBeetle, or the Zig compiler itself, where memory lifetimes are simple.

I’d say the focus on built in tests, fuzzing, debug memory allocators and safe mode shows that Zig is absolutely intended to be robust, within the scope of what the language aims to be. Far more than C itself or most of its popular compilers ever did.

> Like, we don’t say Rust isn’t robust since it doesn’t add dependent types and general purpose static verification that can do more general proofs.

Give it a few years! I've noticed an explosion in interest in formal verification recently, especially since nowadays the bar to entry is so low: just ask your LLM agent to give it a go.

A casual read of TigerBeetle's practices makes it clear they're doing some very unusual things, both in their memory allocation strategy and in their testing/verification.

Despite TigerBeetle being one of the highest-profile remaining Zig projects, I actually don't think they're representative of the average Zig project at all.

Can you elaborate on the unusual part?

All necessary memory is allocated at initialization. The application is not allowed any allocations during it's normal runtime. This is how it avoid memory bugs.

Not a lot of people write programs this way.

A lot of people write software like this when predictable latency is a hard requirement.

Andrew Kelleys original motivation for creating Zig was language that allowed precise low-level control for real-time audio processing.

"Kelley describes why he created Zig, when other options including C, C++, Rust, and Go already exist. He said he set out to develop a digital audio workstation. He tried Go, but found interoperability with C libraries difficult, and said the garbage collector caused audio delays. He tried C++, or coding C-style using a C++ compiler, but found that small mistakes led to memory corruption bugs that took weeks to fix. He tried Rust but "really struggled to write code that would satisfy Rust's rules," and spent a month trying to make font rendering work."

https://www.theregister.com/software/2026/05/28/zig-creator-...

This is standard practice in the games industry.

I do this in Unity because allocations/GC cause hitches. it's pretty normal thing to do there's even the built in pooling libraries so you can pre-allocate 10,000 gameobjects when the game starts. I haven't played with ECS/DOTS yet but I assume it does something similar.

I was just learning yesterday that's exactly what GTA did on PS2, which I thought was interesting. (Not to belittle your point, just giving an example)

This is how basically every console video game works.

Static memory allocation is widely used in quite a bit of embedded software, particularly safety critical stuff. There it's often latency related since you don't want hangs while memory is allocated.

I've even seen it on some simulation software's core that was written in the 80s originally; at the time memory was much more constrained so allocating upfront meant you could check upfront whether the simulation could actually run or not vs crashing out part way through.

I do. The only thing I need dynamic allocations for is queues of asynchronous events, and that's just because I'm too lazy to calculate an upper bound for how many there may be.

A number of commenters have pointed out static allocation, but none mentioned TigerBeetle's sophisticated testing suite, which is more relevant.

See here for a post on their deterministic simulation harness: https://tigerbeetle.com/blog/2023-07-06-simulation-testing-f...

It is quite representative of an embedded software project. TigerBeetle is not what we usually call embedded software, but it is built like it: static memory allocation, a self-contained executable, and a strong focus on determinism are typical in that field, especially for critical software.

And I think embedded software is a field where Zig will be at its best. The only thing it is missing is maturity. When project lifetimes are measured in decades and changing a single byte can cost millions, no one in his right mind will pick a language that is still in development. Things will become interesting when it reaches 1.0.

Static memory allocation is idiomatic in high-performance software. You do the same in C++ if you care about performance and reliability.

the buffer managemnt is just different pattern and style of code thats more low level. when you care about performance and cpu cache, you have to make sure that actual physical memory gets computed at same time as other memory near it so there is less latency.

the primary motivation isn't latency but complexity. People do in some applications free or allocate collectively because they have interrupt times in mind, but most of the time when you manually manage memory the issue is mental overhead, so people gravitate towards models they can keep in their head.

Allocating in large chunks is often not very performant which is why people came up with tools like the borrow checker, you often want to allocate and deallocate dynamically on a need-basis but that's exactly where bugs occur.

you only malloc only once at boot in that pattern, its not about performance at that point. after that you need a strict api and patterns to control and process the data that is where the performance matters...but its niche just like you couldn't want to code a ui from scratch in rust when u could just do a web ui w/ typescript,react tailwind or whatever

Realistically much of the most reliable software in the world was written in C. Robustness is more so a function of coding style and engineering practice than it is of the programming language chosen.

Of course you could argue that on average, most programmers are not going to have the right practices and skill, so on average you should prefer Rust. But that's unrelated to the argument I was making, and in any case not a very interesting point in my opinion.

Adding that with a principled approach, I don't even see much of an issue with doing manual creates and deletes in a object-graph type app, with many unstructured lifetimes. Sometimes that might just be required, and then the complexity is just there either way. Having to cleanups manually or not doesn't change anything about that. It's a bit more cumbersome to get everything right when doing it manually -- sure.

The problem is mostly people graduating from school thinking that somehow there is only stack and heap, and malloc/free is how you do heap. That view completely ignores that the essence of programming systems is mostly to understand the machine, and then doing conceptual and architectural work on a solution (and also on a problem). The act of writing actual code is then mostly just translating those concepts into the digital world verbatim.

Conversely, most of the high impact bugs are also written in C and C++, because they rely on "coding style and engineering practice" to be correct. Rust raises the floor on this by a lot.

> Zig, like C, is simply not a robust language

"Extraordinary claims require extraordinary evidence" -- Carl Sagan

> You can just do that, and then Zig is really no less robust than Rust.

That's just it, using Zig required more rigorous engineering than the Bun team were capable of.

People tried to "just do that" (write their programs in a memory safe way) in C and other languages with manual memory management for decades, and we have countless vulnerabilities that prove this simply doesn't work. That's why newer languages, with the notable exception of Zig, prefer more advanced memory management methods.

> People tried to "just do that" (write their programs in a memory safe way) in C and other languages with manual memory management for decades, and we have countless vulnerabilities that prove this simply doesn't work.

Who are these "people" you speak of? It's possible to write software in low level languages that don't have these problems. Not a "non-zero" it might be possible, it can be done thoughtfully, and the popular notion it can't be done is backed only by incomplete anecdotes.

Should everything be written in low-level languages? No, that would be absurd. Is it a simple fact of life that not every person/team/organisation is capable of meeting certain standards of rigour? Yes. That's not to say anyone in the Bun team could not become sufficiently competent in the future. For whatever reason, current experience, incentives, and personal motivations did not make for a conducive environment to make Bun watertight in Zig.

Yes, it's possible. It's also possible for experienced pilots to fly an airliner completely manually for the full duration of a transatlantic flight without crashing. Still, over the last decades, autopilots and other assistance systems with ever more sophisticated features have been developed, and I would argue that without this technology crashes would be much more frequent than they are today. Same goes for memory management: you can do it manually, and it might work out most of the time, but if the programming language is helping you with it, the likelihood of memory safety issues decreases drastically. And the problem with avoiding these issues only by "meeting certain standards of rigour" is that you might only find out that you have failed to meet them years later, when you learn that your software has a vulnerability.

> Same goes for memory management: you can do it manually, and it might work out most of the time, but if the programming language is helping you with it, the likelihood of memory safety issues decreases drastically. And the problem with avoiding these issues only by "meeting certain standards of rigour" is that you might only find out that you have failed to meet them years later, when you learn that your software has a vulnerability.

Zig does help you. Array slices, explicit nullability of pointers, defer errdefer, explicit allocators, built-in leak detection, bounds checks, overflow detection, the list goes on. If you need to play around on that side of the fence, Zig gives you a lot to make sure you don't mess it up. If we were talking about C I'd give you your flowers, but we're not. The most common issues and vulnerabilities that crop in C from manually managing memory are strongly mitigated by a quarter of that list.

Just people like the linux kernel, all major browsers, most of our popular webservers, etc and basically all non-trivial software projects written in C.

The good news here is that we have more than just anecdotes to support this, we have empirical evidence.

Is engineering capability the issue, or time pressure/constraint?

So it's reducible to a simple matter of inferiority vs superiority?

It matters what software you're writing. When it's a JavaScript runtime, it's not as if you can get away with preallocating all the memory you'll need like some games used to do.

That's like saying that they should have used assembler but they just weren't capable of it. It's personal insult dressed up as a nonsensical technical argument.

Similar in style to Zig's guy public insulting

I think the main issue is that Bun relies heavily on existing C++ libraries like JavascriptCore, and these require RAII and ref-counting semantics from C++ that are closer to Rust than Zig.

You could write a JS engine with Zig-like idioms (arena allocation, static initialization), but that would require re-writing the whole JS engine from the ground-up (though I would definitely be interested in it if someone actually tries to do it!)

Why not using Swift?

Swift is very weak outside Apple ecosystem, compared to Rust. Not sure nowadays, but Swift used to have breaking changes each major release, that's a non go for a big project.

But Swift has a stable ABI which neither Zig nor Rust could provide.

How important is stable ABI for projects like Bun? I think it only matters if you are building a shared library.

only on macOS. On other platforms ABI is not stable.

Andreas Kling talked about it. It boils down to C++ interop sucks (no surprise for lang made by Apple), ecosystem is tiny, Rust works well enough with LLMs.

https://youtu.be/DbHjKi_jASY

Swift is one of the few toolchains that actually has some kind of builtin C++ interop, alongside Objective-C++, D, .NET (via C++/CLI), Carbon (eventually).

He just wanted to use LLMs for coding, and not enough training data on Swift code exists for his use case. Admitting to that would be rather silly, so here we have this sentiment now exist rent free in people's brains.

The C++ interop of Swift is perfectly fine, to such a degree that FoundationDB is now using it effectively alongside its C++ origins.

> You could write a JS engine with Zig-like idioms (arena allocation, static initialization)

Arena allocators & static initializers are not novel. You'll find them in high performance C++ projects as well, such as LLVM or JavaScriptCore. But arena allocators have the quite significant limitation that they only help when everything being allocated in them have approximately the same lifetime. So they don't help when you need to allocate memory to provide the native implementation of a JavaScript object, for example (eg, FFI).

> You could write a JS engine with Zig-like idioms (arena allocation, static initialization)

Could you actually? That seems like a bad fit for a JS engine to me. Predictable memory requirements are great when you can have them, perhaps you can avoid complexity then, but for a JS engine?

This reads like cope because you're re-inventing RAII from first principles.

I cannot take this seriously as tutorials on robust Zig Allocation Pools will store a deinit method for each item within the pool, so when the pool deinits, all internal objects can be deinit'd.

That is just RAII & dtors from first principles, except with extra overhead of manually storing fat pointers yourself (and the bugs that come with this). Instead of using a language with builtin guarantees & optimizations around handling this so your object pools don't need to carry around a bunch of function pointers. C++ has aggressive de-virtualization passes so at runtime a lot of the 'complex object hierarchies' can be flattened to purely static function calls.

I've argued elsewhere some things that are wrong with RAII and C++ objects in general.

Here I would just like to mention that if you have to rely on "de-virtualization" passes, you're in a miserable situation architecturally. If you have code where the overhead of virtual function calls might be too much to pay, don't do virtual functions then. End of story.

To deconstruct a pool of objects, I don't see what should ever be wrong with a function pointer. The overhead of loading the function pointer will get divided by the number of objects being deconstructed. Care to explain what's the issue here?

> I don't see what should ever be wrong with a function pointer. [...]Care to explain what's the issue here?

1. You're writing code you don't have to

2. That adds runtime overhead

3. That when you screw up has non-trivial security & resource management side effects

This is objectively indefeasible in nearly any vaguely professional context.

1. No, you're not writing code you don't have to. It's not different to implementing this as non-virtual methods, in fact I'd argue doing simple functions is more straightforward.

2. And the code being compiled is abstract & generic, it won't be instantiated for every type and bloat the executable or instruction cache.

3. Security concerns: With C++ virtual methods every object carries a mutable pointer too (to a vtable containing function pointers). What resource management side effects please?

Re #3: vtable pointers aren't mutable...?

Of course they are. The pointers to the vtable are part of the object. They aren't mutable fields as per the language, but for security concerns it doesn't matter what the language thinks. Being part of the object, the vtable pointer has to live in a writeable memory mapping (like stack / heap).

Clang pointer authentication makes any type of vtable attack impossible in C++.

Fair enough, this is an extension though and I suppose you could use it with manually constructed vtables as well?

Then I don't understand your argument. If you're just saying what could go wrong with heap corruption, then your vtable complaint also applies to storing function pointers in arena allocators in Zig? Zig doesn't have anything special here?

I asked you what's wrong with pool destructor function pointers. You gave a reason what's wrong and I refuted it. So no, I'm not saying that storing a function pointer is special, just that nothing's wrong with it. (And implying that since there's nothing wrong and it's probably the most straightforward thing to do, it's also probably the right thing).

I've argued elsewhere some things that are wrong with RAII and C++ objects in general.

You claimed there were problems many times for sure, I don't think you came up with any evidence of those problems.

You keep "asking" for evidence but the only evidence presented by yourself is that you have merely surface-level understanding of the subject matter, and are looking for arguments, not insight and critical examination.

It's your claim that destructors are harmful so the burden of proof is on you.

People use them because by default values have scope based lifetimes and destructors unify the handling of stack based values which require no explicit cleanup with data structures that heap allocate, which require no explicit cleanup once the destructor is implemented.

This is the opposite of C where even though the resource cleanup needs to happen on scope end, it is not automatic, and so becomes a source of bugs. This is exaggerated when there are multiple returns, gotos, macros and other sources of branching especially for error handling.

This automation also removes boilerplate so there is less management that needs to be done when using data structures.

What was your evidence or explanation?

> It's your claim that destructors are harmful so the burden of proof is on you.

I have given a variety of arguments why I think the C++ RAII specifically has downsides. You can accept them or ignore them, but don't act like I didn't give arguments.

> People use them because by default values have scope based lifetimes and destructors unify the handling of stack based values which require no explicit cleanup with data structures that heap allocate,

Once again you're explaining beginner C++ do me. Are you still doubting if I understand this argument? My response to this was and is, if you have primarily stack scoped lifetimes, you are writing beginner programs. This is scripting and plumbing. It's not interesting to me. Systems programming is not so much about stack scoped lifetimes.

RAII systematicing object lifetimes and cleanup, thus enabling exceptions and implicit or uncontrolled control flow, may sound nice on paper, but turns out we shouldn't want them in the first place. What RAII leaves for me is a system that will automatically call nested object's destructors when I delete something. It's not something I want in general, I think it has more downsides than upsides for the code I'm writing. I've actually tried to use RAII many times and I've concluded it doesn't work for me.

> This is exaggerated when there are multiple returns, gotos, macros and other sources of branching especially for error handling.

If I were you, my response would be: The burden of proof is on you, show the evidence. But my answer is, yes that is right, but everything is a tradeoff, and the issues caused by manual cleanup are also somewhat exaggerated by C++ people, and the issues caused by blindly buying into the corset of C++ types are not well understood by C++ zealots (I've done my best at explaining them).

Issues caused by C approach are also a matter of design and approach to programming in general. It also depends on the actual problem you're solving. The linux kernel for example doesn't exactly have the easiest or most beautiful code to follow, but surely it's one of the most technical codebases out there, one that solves difficult problems (performant resource multiplexing for programs that it doesn't even know). On the other hand, the debugger code base I've referenced doesn't have any gotos for example, nor even early returns (or almost none, not sure).

Find me a single example of programs that run as fast and are as productively maintained as these two codebases in their respective areas? I believe there aren't any.

This should be plenty evidence to a reasonable mind, but that isn't you.

I have given a variety of arguments why I think the C++ RAII specifically has downsides.

I don't think you did, I think you just said it has downsides over and over.

Once again you're explaining beginner C++ do me.

Don't ask for basic knowledge then get upset when you get it.

My response to this was and is, if you have primarily stack scoped lifetimes, you are writing beginner programs.

This is what the vast majority of values have. Some escape one scope and get cleaned up in another one. This also includes values inside data structures.

It's not something I want in general, I think it has more downsides than upsides for the code I'm writing. I've actually tried to use RAII many times and I've concluded it doesn't work for me.

Again, this isn't an explanation, it's just you saying "I don't think it's good, I don't like it", but you aren't explaining why. This isn't evidence, it's just you restating "this is bad". Why is it bad? "I told you it's bad!!".

thus enabling exceptions and implicit or uncontrolled control flow

Exceptions aren't uncontrolled flow and you can also not use them. Something else being enabled doesn't mean the unrelated feature is bad. This also implies that every other language that isn't C is terrible because they have some sort of automatic cleanup. Now java and python are unstructured by your own definition?

If I were you, my response would be: The burden of proof is on you, show the evidence.

You don't have an explanation of why the burden of proof is on me. Everyone uses these techniques in system software now. You are the odd person out, that's why the burden of proof is on you.

I also gave you a very good explanation and you said "you're explaining basic C++ to me". I am, you asked for it and you didn't poke any hole in why it's wrong.

the issues caused by manual cleanup are also somewhat exaggerated by C++ people

It means memory leaks and crashes which everyone has been fighting for 50 years.

This should be plenty evidence to a reasonable mind, but that isn't you.

Someone running a marathon without shoes doesn't mean shoes are bad. Just because an old program is written in C, that has no bearing on if other tools are good or not. This is not a logical conclusion. Unix was written in C too, does that mean destructors are bad? No one said it's impossible to write a program in C now that C++ exists.

Why can't you give a single basic explanation instead of making the same claim over and over?

> I don't think you did, I think you just said it has downsides over and over.

Show evidence of your claim.

> Don't ask for basic knowledge then get upset when you get it.

Where did I ask for basic knowledge? You are hallucinating. I've repeatedly and explicitly told you to shut up explaining beginner things. You are trying to refute my criticisms of RAII with your silly explanations of how RAII works. That's not how an argument or "evidence" works.

> Exceptions aren't uncontrolled flow and you can also not use them.

I would rather call it _implicit_ flow but they also lead to losing control over control flow because of that. Yes, I can just not use exceptions, and also avoid gotos and use them in a principle way, and do cleanup in a principled way. And then I can also do without RAII and without all the baggage I'd have to buy into in order to use it.

> You don't have an explanation of why the burden of proof is on me.

Please p* off man. You're being ridiculous.

> It means memory leaks and crashes which everyone has been fighting for 50 years.

Like you have been on your Linux, Windows, or Mac machine? Maybe you are running a linux machine with an uptime of weeks, months, or even years?

> Someone running a marathon without shoes doesn't mean shoes are bad.

You claiming to run a marathon with a 25kg backpack doesn't mean you don't lie, and it also doesn't prove running without it isn't the better approach.

> Why can't you give a single basic explanation instead of making the same claim over and over?

The only person not giving explanation beyond basic boring introductory C++ RAII school, that's YOU my friend. I've been giving a lot of explanations what I think is problematic, somehow it seems you're mentally unable to acknowledge them.

> I don't think you did, I think you just said it has downsides over and over.

Show evidence of your claim.

That would be proving a negative, which is another logical fallacy.

Please p off man. You're being ridiculous.*

If that were true you could explain why.

I would rather call it _implicit_ flow but they also lead to losing control over control flow because of that

But it's just running something you need to run anyway and it's optional. Destructors don't need branching, they can just run a single function like free.

And then I can also do without RAII and without all the baggage I'd have to buy into in order to use it.

Again the "baggage" is the part you can't seem to explain.

Like you have been on your Linux, Windows, or Mac machine? Maybe you are running a linux machine with an uptime of weeks, months, or even years?

Are you trying to say people never write memory leaks or forget to clean up resources in C? Something being done with huge amounts of efforts doesn't mean a better way to do things is bad.

You claiming to run a marathon with a 25kg backpack doesn't mean you don't lie, and it also doesn't prove running without it isn't the better approach.

This doesn't mean anything. Now you're trying to say (without evidence) that someone is lying? Destructors don't add any size to a program.

Is this your only argument after dozens of messages? Running a function with no branching destroys control flow and running a tiny function that runs what you need to call anyway is bloat?

I've been giving a lot of explanations what I think is problematic,

No, you just said it's problematic over and over, that's not an explanation.

You are insufferable. Get lost.

You don't get to reply and tell me I'm lying about something then get upset when I reply back. You can always actually explain in depth why I'm wrong.

How about you do the following two Google (or AI) searches

"Please give me examples of great systems software written in plain C or C style procedural C++"

"Please give me examples of great systems software written in modern C++, as opposed to procedural C style C++ or plain C".

Why does it seem like the majority of core infrastructure, like Linux kernel (also vast parts of Windows/Mac OS), PostgresQL, Sqlite3, Git, OpenSSH, GCC, but also e.g. MS Office/Excel, are written in plain procedural code and not in modern C++? For the latter, I get stuff like "ScyllaDB NoSQL database" or "Envoy Proxy" or whatever, what is that even and why should I care or how do I know they're actually technically solid products and not just hype?

My claim: The arguments that I've given (but you keep insisting I didn't give them) play a huge rule in why that is so. You can use C++ RAII for plumbing and high-level stuff. But if you try to actually implement technically interesting things, it won't help you at all, it's just getting in the way.

How about you do the following two Google (or AI) searches

Why don't you do it so you can make your own argument.

Why does it seem like the majority of core infrastructure,

Why are projects started decades not using modern C++ that came decades after they were started?

This doesn't have anything to do with destructors.

The arguments that I've given (but you keep insisting I didn't give them)

You didn't give arguments, you made claims based on other people doing something different decades before modern C++ existed. Someone managing to dig a hole with their hands doesn't make a shovel a bad tool. Animals dig holes all the time, people are better at it.

But if you try to actually implement technically interesting things, it won't help you at all, it's just getting in the way.

This again is your claim which you haven't been able to explain in any way.

This is a general problem with destructors, you can't "batch delete" objects. To free a lot of stuff you're required to go pointer by pointer through the tree to clean up each object. To get real performance gains from pools you can't have per-object/subobject custom cleanup code.

Not necessarily. Drop semantics are just syntactic sugar, and can thus be aggressively inlined or auto vectorized by the compiler.

Zig is always _less_ robust than rust. Even if you have a single allocation you can always forget to free it.

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