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noalloc: Tooling and libraries to enforce zero heap allocations in Golang(github.com)

75 points by g0xA52A2A 1 day ago | 46 comments

Hey folks, this is my project. I really liked OxCaml's zero_alloc feature [0], something you don't get in Rust or Zig or Go*, and have been trying to get a handle on allocations in The Consensus's code search engine.

It's an extremely early project but it's been helping me out a bunch already. Would love to hear your bug reports or requests if you try running it on your codebase.

[0] https://theconsensus.dev/p/2026/06/27/the-feature-in-oxcaml-...

* I think you can get this in Clang and maybe GCC with `__attribute__((nonallocating))` though.

[–] MrBuddyCasino 6 hours ago

Rust has a mode where no allocator is available.

[–] eatonphil 6 hours ago

No allocator available isn't the same as being able to enforce no allocations.

[–] dlahoda 5 hours ago

that option in rust allows to set own allocator, which may be disabled after initial allocation, may be per thread.

[–] andrewla 10 hours ago

The end state of every garbage collected language is a suite of tools to prevent garbage collection at all costs.

I think we can learn something here.

[–] vatsachak 10 hours ago

I think that people hyperoptimize for no reason though. How many applications are there that require no GC? I feel like you can write the no-gc code in Rust and then just use it from the C ABI from any GC language.

[–] ted_dunning 9 hours ago

Embedded systems benefit substantially from decreased GC, especially in the context of non-relocating collectors (as with Go) in machines without memory management units. The problem is not the overhead, it is the effect of memory fragmentation.

The OP article here is nice because it allows selective enforcement of allocation free code. If you have code that has some discipline about heap allocation such as having all small allocations then you are OK on the fragmentation front.

[–] bootsmann 8 hours ago

Isn’t writing Go for embedded systems kinda like eating soup with a fork tho? This language was designed to write multithreaded asynchronous code to power microservice meshes.

[–] Groxx 6 hours ago

If it's within like 90% of your targets and it's a far easier development experience, but you need to optimize a small bit to fit in the budget, tools like this can be fantastically useful. Rewriting the whole thing in, like, C, complete with a coroutine stack, would be a hell of a lot more work than "avoid allocations here".

[–] pjmlp 8 hours ago

Real time Java is doing just fine with PTC and Aicas still in business.

[–] fpoling 6 hours ago

GC in Java is the best in world with a lot options and knobs that allows to tune to particular application requirements. Still some trading platforms using it disable GC and just ensure enough memory is available so memory leaks during the trading hours would not matter before the application will be restarted.

[–] pjmlp 4 hours ago

Just like plenty of C and C++ deployment scenarios have special purpose memory allocators, or forbid memory allocations other than at startup.

Yet one still needs to account with processes like MISRA to account for safety.

[–] fpoling 6 hours ago

I worked on a project with a network server written in Go with soft realtime requirements. In theory Go should be very good fit for it especially given GC tuning towards low latency, not throughoutput. In practice the latency spikes from GC were bad and there were no good options to resolve those given the deployment constrains and the amount of third-party libraries used.

[–] treyd 10 hours ago

This is a viable approach for many scenarios. Uniffi is a tool/library from Mozilla that makes this a lot easier across platforms.

After a few rounds of this though it might end up seeming like it's not worth the hassle and it's easier to build the whole application in Rust.

[–] vatsachak 9 hours ago

Lifetime and smart pointer hell is real though.

[–] treyd 9 hours ago

Once you internalize it it's really not a problem. That's why I said "after a few rounds of this".

[–] vatsachak 9 hours ago

I've been writing Rust for a year and change professionally, also as a hobby, and even though I love it, it's really annoying to choose the allocation model and lifetime model at every step.

For example,

- A field in a struct cannot borrow another field so now you'd have to create two structs. I guess you could write an impl to borrow that field instead of storing the borrow.

- In simulation software I wrote I found that mimalloc does just as good as bumpalo (within 5%) so carrying a bump everywhere was useless. Not really a rust issue but rather a loss of faith in manual memory management for me.

- Eventually over time you start adding Arc<Fn(Blah)->Foo> everywhere and Box, Arc and friends start coming in. But you can't have cyclical references there so you have to use Weak. And you have to use OnceCell or LazyCell or LazyLock for things that should run at start time.

Rust is really great for the crates, but ...

For applications which are not absolutely performance critical and cannot* be stated pretty easily in linear logic + clone + drop you can get away with Haskell

[–] Mawr 8 hours ago

Switching out the entire ecosystem, libraries, tooling; rewriting the entire codebase; learning the new language and its idioms; and then giving up the unknown benefits of the previous language that the new language lacks (for Go->Rust this could e.g. be compile times)—generally, trading known downsides of a language for unknown downsides of another—is a huge undertaking and therefore very unlikely to ever be worth the hassle.

[–] hoppp 10 hours ago

I agree. If the use-case requires no GC then Rust or Zig or C++ is a better fit.

I don't see much point in choosing a language just to bypass it's features.

[–] cpgxiii 9 hours ago

Coming from an environment in which we extensively use mixed codebases (C++ and Python) to combine performance and ease of prototyping, one of the pain points is that there is almost always some impedance mismatch between the lifetime/ownership models of the two languages. When something goes wrong here, it's usually a real pain to debug and resolve, and often the resolution involves imposing constraints from one language onto the other (e.g. C++ that would idiomatically use unique_ptr instead needs to use shared_ptr because unique_ptr is essentially impossible to completely capture in Python).

Given the issues involved in mixing languages, there can be cases where sticking with one "good enough" GC'd language and having to write a few performance-sensitive parts in very unidiomatic form to minimize/eliminate GC work is preferable.

[–] revengerwizard 9 hours ago

I feel like that may be more of an issue with how Python's C API is designed, leaking basically most of its internals, and then having to remember to manage (increment/decrement) Python objects correctly.

[–] cpgxiii 4 hours ago

I don't think that's the problem, at least not directly for us. The immediate interface between the languages is handled by a binding layer (e.g. pybind11 or nanobind), but that rarely lets you fully express object relationships (something that would be more possible without the binding layer) so it is very easy to either not capture ownership (and thus the C++ object is destroyed out from underneath you) or express a cycle that cpython can't understand (and thus the C++ objects are never destroyed and can leak a significant amount of memory). Explicit manual control would avoid that, but at a level of work that would be prohibitive of having extensive bindings in the first place.

[–] eptcyka 8 hours ago

Go really sucks at calling into C code.

[–] kvemkon 10 hours ago

Similar with malloc in C / new in C++, especially for short-living, repeating, in hot path. And then you hear: avoid allocations, use constant-size buffers or memory pools. Avoid spawning threads, use thread pools.

[–] iguessthislldo 9 hours ago

That observation checks out. About a decade ago, one of my former coworkers areas of interests was making Java applications and frameworks that didn't use the any additional heap beyond app initialization. This was apparently for embedded/low power devices. It was neat to hear about as a C++ dev, but I'm not sure how much of a business or technical advantage it had beyond that.

[–] pjmlp 8 hours ago

Job pool, memory safety and lower development costs versus C++ tooling.

"Why we chose Java for our High-Frequency Trading application"

https://medium.com/@jadsarmo/why-we-chose-java-for-our-high-...

[–] jcelerier 8 hours ago

i'm developing apps that do real-time audio and video and any allocation or anything that may end up in a system call directly or indirectly (for instance accessing swapped or mapped but not yet loaded memory) on the hot path is a complete no-go and will instantly cause very audible glitches for audio, and visual frame pacing issues

[–] prophet_margin 9 hours ago

The big one that comes to mind is MISRA.

[–] bayindirh 7 hours ago

I don't think so. People love to see how far they can go in some aspect sometimes. If I had the same amount of free time 5 years ago, I'd have tried the same thing with Go, because I like the language, and love the act of programming and seeing things.

Also, I also agree that people optimize without proper testing and profiling. If there's a real bottleneck here, trying to optimize it is the right call. OTOH, optimizing without profiling opens a lot of unnecessary cans.

Lastly, Go doesn't like constant allocation and deallocation of variables, that's true, but I believe knowing this and optimizing hot-loops for that goes a very long way as a start.

[–] legulere 7 hours ago

Zero allocation is also a thing in rust. What you can learn is to reduce allocations in your critical paths.

[–] pjmlp 8 hours ago

Anti GC folks forget that these workarounds are only required in GC languages that don't offer explicit language features for stack and native heap allocations, like Cedar, Modula-3, all Oberon variants, C#, F#, D, Swift,..

Like everything else in Go, its designers have decided to ignore learnings in GC systems languages.

[–] raggi 9 hours ago

The end state of inappropriate use of garbage collected languages.

Go/GC are mostly fine for medium frequency medium scale mid stack problems.

It’s bad for high frequency computing. It’s bad for very small targets, for very large targets, and by association software that lives at the very bottom of the stack.

Go is a high efficiency framework for writing mid sized servers, not a systems language. The runtimes hard opinions and closed interface are the reason for this enclosing definition and the GC is one part of that.

[–] kristianp 4 hours ago

That some people think in black and white?

[–] Gys 10 hours ago

Maybe. Go code is designed to be readable and stable. My guess is that most Go code is running fine with garbage collection. There are always edge cases and then just choose another language.

[–] gritzko 9 hours ago

If you don't allocate, why do you even need Go or Rust? LLMs handle less elegant syntax just as well. I use a zero-malloc C dialect with slices and bounds-checking.

Just recently I was sketching a smallish database in zero-malloc C. https://replicated.live/blog/db That was partly because most LSM data structures are read-only, so mmap was good enough and concurrent access was safe for the bulk of the data.

The "hot zone" (memtable) then requires some intricate engineering, but that is the case either way.

You can go quite far with zero-malloc C.

[–] steveklabnik 9 hours ago

Rust doesn't have heap allocation in the language at all. It still has useful features regardless.

[–] gritzko 8 hours ago

Technically, malloc() is a library function, not core C. My point is this: guarantees cost complexity, and you always have to keep in mind the assumptions and how much of it is theater. So, neither way is strictly better. It depends. For immutable data, lifetimes don't buy much, for example.

[–] kristianp 4 hours ago

Interesting difference between Go and Python, `c.counts[name] += n` can allocate if name isn't already present, whereas in Python you get a key error.

[–] kvemkon 10 hours ago

Go compiler has an advanced escaping analyzer. Wouldn't it be easier and better to add this noalloc-analyzer feature to golang directly?

[–] eatonphil 9 hours ago

I agree this isn't the absolute ideal form. I'd rather it be built in as a language directive or something. noalloc does parse compiler escapes emitted by the Go compiler with `-gcflags=-m -S`. One problem is that these are not really a standard format. But I hope that with testing across versions (over time anyway, I only run this on Go 1.27) it'll be stable enough.

[–] kvemkon 8 hours ago

Thanks for clarification! I'm glad, that you're using the golang compiler capabilities. And now I see:

https://github.com/theconsensuslabs/noalloc#the-compilers-ou...

[–] raggi 9 hours ago

Historically that was rejected.

Tides have shifted somewhat, but I suspect this may still be rejected.

Unfortunately a lot of people’s experience with such proposals was also historically getting gaslit by a brigade, so a lot of folks moved on and won’t bother trying again.

[–] ted_dunning 9 hours ago

The Go community has not been very welcoming for embedded applications, for sure.

That might be changing (slightly) because of the Tamago work on NOOS.

[–] wahern 8 hours ago

Goroutines and lexical closures create a dilemma for embedded targets. Go was designed around the notion that using goroutines (threading, basically) should be effortless and employed without hesititation. Lexical closures is a critical aspect of that, and by extension GC. Both goroutines and lexical closures require dynamic allocation, at least when combined with some other Go design decisions (e.g. seamless recursion, dynamic method invocation, etc).

Go does a great job of making these impose minimal cost, both technically and cognitively, on typical platforms, from server (including many "embedded" server environments) to desktop to smartphone. That's why it has such a sophisticated yet largely transparent user space threading layer. But it's very difficult and usually impractical for Go to target extremely resource constrained environments without exposing and crippling it's core abstractions. Some people are willing to contort Go to fit that space, but perhaps that's because their vision of what makes Go, Go, differs from the creators' and core maintainers' understanding of Go.

[–] Gibbon1 7 hours ago

Maybe having a way to enforce that on the compiler. So you can force the compiler to tell you it couldn't eliminate heap allocations.

[–] zinodaur 11 hours ago

I love it. Any thoughts on allowing (value type) Pointers into a Region?