Also worth noting that "translated from C++" Rust is totally fine as a starting point. You can incrementally make it more idiomatic later once the C++ side is retired. The Rust compiler will still catch whole classes of memory bugs even if the code reads a bit weird. That's the whole point.
> Way too many rewrites fail because people try to "improve" things during the port
I think the last one gets ignored easily but my favorite time to document code is when reading it (but the best time is when writing it). It forces you to think explicitly about what the code is doing and makes it harder for the little things to slip by. Given that Ladybird is a popular project I really do think good documentation is a way to accelerate its development. Good documentation means new people can come in and contribute faster and with fewer errors. It lowers the barrier to entry, substantially. It's also helpful for all the mere mortals who forget things
This is the way. Coding assistants are also really great at porting from one language to the other, especially if you have existing tests.
I had a broken, one-off Perl script, a relic from the days when everyone thought Drupal was the future (long time ago). It was originally designed to migrate a site from an unmaintained internal CMS to Drupal. The CMS was ancient and it only ran in a VM for "look what we built a million years ago" purposes (I even had written permission from my ex-employer to keep that thing).
Just for a laugh, I fed this mess of undeclared dependencies and missing logic into Claude and told it to port the whole thing to Rust. It spent 80 minutes researching Drupal and coding, then "one-shotted" a functional import tool. Not only did it mirror the original design and module structure, but it also implemented several custom plugins based on hints it found in my old code comments.
It burned through a mountain of tokens, but 10/10 - would generate tens of thousands of lines of useless code again.
The Epilogue: That site has since been ported to WordPress, then ProcessWire, then rebuilt as a Node.js app. Word on the street is that some poor souls are currently trying to port it to Next.js.
All of them are moving into the direction of "less human involved and agents do more", while what I really want is better tooling for me to work closer with AI and be better at reviewing/steering it, and be more involved. I don't want "Fire one prompt and get somewhat working code", I want a UX tailored for long sessions with back and forth, letting me leverage my skills, rather than agents trying to emulate what I already can do myself.
It was said a long time ago about computing in general, but more fitting than ever, "Augmenting the human intellect" is what we should aim for, not replacing the human intellect. IA ("Intelligence amplification") rather than AI.
But I'm guessing the target market for such tools would be much smaller, basically would require you to already understand software development, and know what you want, while all AI companies seem to target non-developers wanting to build software now. It's no-code all over again essentially.
I decided to create a Claude skill called "teach". When I enable it, Claude never writes any code. It just gives me hints - progressively more detailed if I am stuck. Then it reviews what I write.
I am finding it very satisfying to work this way - Rust in particular is a language where there's little space to "wing it". Most language features are interlaced with each other and having an LLM supporting me helps a lot. "Let's not declare a type for this right now, we would have to deal with several lifetime issues, let's add a note to the plan and revisit this later".
I used Claude to rewrite it in golang and extend its features. Now I have tests, automatic AIA chain walking, support for all the DER and JKS formats, and it’s fast. My bash script could spend a few minutes churning through a folder with certs and keys, my golang version does a few thousand in a second.
So I basically built a limited version of OpenSSL with better ergonomics and a lot of magic under the hood because you don’t have to specify input formats at all. I wasn’t constrained by things like backwards compatibility and interface stability, which let me make something much nicer to use.
I even was able to build a wasm version so it can run in the browser. All this from someone that is not a great coder. Don’t worry, I’m explicitly not rolling my own crypto.
> We’ve verified that every AST produced by the Rust parser is identical to the C++ one, and all bytecode generated by the Rust compiler is identical to the C++ compiler’s output.
Is this a conventional goal? It seems like quite an achievement.
No, they are quite terrible at doing that.
They may (I guess?) produce code that compiles, but they will, almost certainly not produce the appropriate combination of idioms and custom abstractions that may the code "at home" in the target language.
PS - Please fix your blockquote... HN ignores single linebreaks, so you have to either using pairs of them, or possibly go with italicization of the quoted text.
In my coding agent std::slop I've optimized for this workflow https://github.com/hsaliak/std_slop/blob/main/docs/mail_mode... basically the idea is that you are the 'maintainer' and you get bisect safe, git patches that you review (or ask a code reviewer skill or another agent to review). Any change re-rolls the whole stack. Git already supports such a flow and I added it to the agent. A simple markdown skill does not work because it 'forgets'. A 'github' based PR flow felt too externally dependent. This workflow is enforced by a 'patcher' skill, and once that's active, tools do not work unless they follow the enforced flow.
I think a lot of people are going to feel comfortable using agents this way rather than going full blast. I do all my development this way.
All my vibe coded projects are human directed, unless explicitly stated otherwise
And you might say that this is a hypothetical problem, one that is not practically occurring. Well, we had a similar problem like this in the recent past, that LLMs are close to _making actual_. When it comes to software patents, they were considered a _hypothetical_ problem (i.e. nobody is going to bother suing you unless you were so big that violating a patent was a near certainty). We were instructed (at pretty much all jobs), to never read patents, so that we cannot incriminate ourselves in the discovery process.
That is going to change soon (within a year). I have friend, whom I won't name, who is working on a project, using LLMs, to discover whether software (open source and proprietary) is likely to be violating a software patent from a patent database. And it is designed to be used, not by programmers, but by law firms, patent attorneys, etc. Even though it is not marketed this way, it is essentially a target acquisition system for use by patent trolls. It is hard for me to tell if this means that we will have to keep ignoring patents for that plausible deniability, or if this means that we will have to become hyper informed about all patents. I suppose, we can just subscribe to the patent-agent, and hope that it guides the other coding agents into avoiding the insertion of potentially infringing code.
(I also have a friend who built a system in 2020 that could translate between C++ and Python, and guarantee equivalent results, and code that looks human-written. This was a very impressive achievement, especially because of how it guarantees the equivalence (it did not require machine-learning nor GPUs, just CPUs and some classic algorithms from the 80s). The friend informs me that they are very disheartened to see that now any toddler with a credit card can mindlessly do something similar, invalidating around a decade of unpublished research. They tell me that it will remain unpublished, and if they could go back in time, they would spend that decade extracting as much surplus from society as possible, by hook or by crook (apparently they had the means and the opportunity, but lacked the motive); we should all learn from my friend's mistake. The only people who succeed are, sadly, perversely, those who brazenly and shamelessly steal -- and make no mistake, the AI companies are built on theft. When millionaires do it, they become billionaires -- when Aaron Swartz does it, he is sentenced to federal prison. I'm not quite a pessimist yet, but it really is saddening to watch my friend go from a passionate optimist to a cold nihilist.).
I don't know if it's a good fit. Not because they're writing a browser engine in Rust (good), but because Ladybird praises CPP/Swift currently and have no idea what the contributor's stance is.
At least contributing will be a lot nicer from my end, because my PR's to Ladybird have been bad due to having no CPP experience. I had no idea what I was doing.
Yeah that is the thing I struggle with. I am really happy for people falling in love with Rust. It is a amazing language when used for the right use case.
The problem is that had my Rust adventures a few years ago and I am over the hype cycle and able to see both the advantages and disadvantages. Plus being generally older and hopefully wiser I don't tie my identity towards any specific programming language that much.
So sometimes when some Junior dev discovers Rust and they get really obnoxious with their evangelicalism it can be very off putting. Really not sure how to solve it. It is good when people get excited about a language. It just can be very annoying for everyone else sometimes.
Not anymore.
Doesn't sound like it's some Fish-style, full migration to Rust of everything. Seems like they are just moving a couple parts over for evaluation, and then, going forward, making it an official project language that folks are free to use. They note that basically every browser already does that, so this isn't a huge shakeup.
if it works it works i guess, but it seems mad to me on the surface
I mean, they seem mostly to be against anything that isn't C++'s peculiar brand of Object Oriented Programming?
(also against women and immigrants, but that's a different story)
The Jakt -> Swift -> Rust pivots look like the same thing on a different level. The initial change to Swift was surely motivated by potential industry support gain (i believe it was a dubious choice from purely engineering standpoint).
It's awe-inspiring to see how a person can carve a job for himself, leverage hobbyists'/hackers' interest and contributions, attract industry attention and sponsors all while doing the thing he likes (assuming, browsers are his thing) in a controlling position.
Can't fully rationalize the feeling, but all of this makes me slightly wary. Doesn't make it less cool to observe from a side, though.
The truth is more simple: he's a good engineer and leader, people recognised that and offered him sponsorships, and the project took off by itself.
We’re at the point where a solid test suite and a high-quality agent can achieve impressive results in the hands of a competent coder. Yes, it will still screw up, needs careful human review and steering, etc, but there is a tangible productivity improvement. I don’t think it makes sense putting numbers on it, but for many tasks, it looks like there’s a tangible benefit.
IIRC he used to work on the Safari browser engine at Apple.
LLM and rust rewrite together. And it does work so hopefully they get more attention and build it so I have an alternative browser to use
Correct me if I’m wrong since I don’t know these two languages, but like some other languages, doing things the idiomatic way could be dramatically different. Is “cleanup” doing a lot of heavy lifting here? Could that also mean another complete rewrite from scratch?
A startup switching languages after years of development is usually a big red flag. “We are rewriting it in X” posts always preceded “We are shutting down”. I wish them luck though!
Startups are not a good comparison here. They have a different relationship with code than software projects.
Linux has rewriten entire stacks over and over again.
The PHP engine was rewritten completely at least twice.
The musl libc had entire components rewritten basically from scratch and later integrated.
If you do a rewrite you essentially put everything else on halt while rewriting.
If you keep doing feature dev on the old while another "tiger team" is doing the rewrite port then these two teams are essentially in a race against each other and the port will likely never catch up. (Depending on relative velocities)
Maybe they think that they can to this LLM assisted tools in a big bang approach quickly and then continue from there without spending too much time on it.
Testing has become 10x as important as ever.
I am already using low code tooling with agents for some projects, in iPaaS products.
I feel like you just know it’s doomed. What this is saying is “I didn’t want to and cannot review the code it generated” asking models to find mistakes never works for me. It’ll find obvious patterns, a tendency towards security mistakes, but not deep logical errors.
The part that concerns me is whether this part will actually come in time or not:
> The Rust code intentionally mimics things like the C++ register allocation patterns so that the two compilers produce identical bytecode. Correctness is a close second. We know the result isn’t idiomatic Rust, and there’s a lot that can be simplified once we’re comfortable retiring the C++ pipeline. That cleanup will come in time.
Of course, it wouldn't be the first time Andreas delivered more than I expected :).
No one wants to work with this generated, ugly, unidiomatic ball of Rust. Other than other people using AI. So you dependency AI grows and grows. It is a vicious trap.
I don't like this bit. Wouldn't it be better to decide on a memory-safe language, and then commit to it by writing all new code in Rust, or whatever. This looks like doing double the work.
I suspect that'll also be what happens here. And if the use of Rust is successful, then over time more components may switch over to Rust. But each component will only ever be in one language at a time.
it is totally possible to use some strict subset of C++, which will be memory safe.
Why was there ever any expectation for Swift having good platform support outside Apple? This should have been (and was to me) already obvious when they originally announced moving to Swift.
Apple puts zero resources into making that claim reality, however.
[1] Swift was first created in 2010, 16 years ago and officially launched in 2014, 12 years ago, by a huge multi-billion dollar corporation. The same corporation has launched hundreds of products and services in the same time period. If they really wanted Swift to be cross platform at a competitive level (Java, .Net, Python, JS, etc), they would have done it by now.
I wonder what kind of tech debt this brings and if the trade off will be worth whatever problems they were having with C++.
The problem was strictly how cpp is perceived as an unsafe language, and this problem rust does solve! Not being sarcastic, this truly looks like a mature take. Like, we don't know if moving to rust would improve quality or prevent vulnerabilities, here's our best effort to find out and ignore if the claim has merits for now. If the claim maintains, well, you're better prepared, if it doesn't, but the code holds similar qualities...what is the downside?
My general thoughts on Rust:
- Excellent for short-lived programs that transform input A to output B
- Clunky for long-lived programs that maintain large complex object graphs
- Really impressive ecosystem
- Toxic community
They're not porting the browser itself to Rust, for the record.
Don't forget that the Rust ecosystem around browsers is growing, Firefox already uses it for their CSS engine[0], AFAIK Chrome JPEG XL implementation is written in Rust.
So I don't see how this could be seen as a negative move, I don't think sharing libraries in C++ is as easy as in Rust.
Seems like a lot of language switches in a short time frame. That'd make me super nervous working on such a project. There will be rough parts for every language and deciding seemingly on whims that 1 isn't good enough will burn a lot of time and resources.
I use AI more and more. Goes like create me classes A,B,C with such and such descriptive names, take this state machine / flowchart description to understand the flow and use this particular sets of helpers declared in modules XYZ
I then test the code and then go over and look at any un-optimal and other patterns I prefer not to have and asking to change those.
After couple of iterations code usually shines. I also cross check final results against various LLMs just in case
Adding the "with help from AI" almost always devolves the discussion from that to "developers must adopt AI or else!" on the one hand and "society is being destroyed by slop!" on the other, so as long as that's not happening I'm not complaining about the editorialized title.
Personally, I can’t get meaningful results unless I use the tool in a true pair-programming mode—watching it reason, plan, and execute step by step. The ability to clearly articulate exactly what you want, and how you want it done, is becoming a rare skill.
> Ralph Wiggum loop
But Rust doesn't have C++ interop at all?
Firefox is a mixed C++ / Rust codebase with a relatively close coupling between Rust and C++ components in places (layout/dom/script are in C++ while style is in Rust, and a mix of WebRender (Rust) and Skia (C++) are used for rendering with C++ glue code)
It also doesn't have the disadvantages of Swift. Once the promise of Swift/C++ interop is gone there isn't enough left to recommend it.
[1]: https://www.swift.org/documentation/cxx-interop/
[2]: https://www.swift.org/blog/improving-usability-of-c-librarie...
Attackers are surprisingly resilient to partial security.
While rust is nice on paper, writting complex software in it is mentally consuming. You can not do it for a long time.
Does this still get you most of the memory-safety benefits of using Rust vs C++?
The article fails to explain why. What problems (besides the obvious) have been found in which "memory-safe languages" can help. Do these problems actually explain the need of adding complexity to a project like this by adding another language?
I guess AI will be involved which, at this early point in the project would make ladybird a lot less interested (at least to me).
Why isn't that enough?
Well, what else is there besides the obvious? It's a browser.
So, even though they want the code base to be in Rust, they will continue writing new code in C++ and then translating it to Rust later to remove the C++ they just added.
There must be a really good reason for this, such as Rust doesn’t interop well with C++, otherwise this seems like a poor decision.
Yea, I'd bet it's that. Ideally, you'd want to stop writing C++ and continue with Rust on all new code, but Rust has stricter semantics, so the interop is somewhat "easy" in one direction, but very hairy in the other direction.
This means that in practice, you want to start porting from leaf components and slowly grow closer to the root, which stays in C++ for quite some time and just calls into Rust through C API (or something close to it).
If you're curious about the topic, there's a interop library called Zngur (https://hkalbasi.github.io/zngur/), which is built on this assumption. They have a pretty good explanation of the concrete problems on the homepage.
I am very interested to know if this time and energy spent actually improved memory safety.
Other engineers facing the same challenges want to know!
On the rust side, the question is how much `unsafe` they used (I would hope none at all, although they don't specify).
It could have been worse. C++ code naively converted line-by-line to Rust typically results in weird and unsafe Rust, but in this case it seems they've only been strict about the results being the same, not the structure of the implementation.
Rewrites have a very high risk of introducing regressions. Trying to fix bugs while rewriting will only make things harder, because instead of simply comparing outputs exactly, you'll have to judge which output is the right one. If you let the behavior significantly diverge during the rewrite, you'll just have two differently buggy codebases and no reference to follow.
It's much easier to make a bug-for-bug compatible copy, and fix bugs later.
This project, of all of them, throwing in the towel on AI makes me fear AI abstainers have no future.
they learn Rust
it takes a couple of years
it's not that hard.
I guess it's a long way off, since the LLM translation would need to be refactored into natural Rust first. But the value of it would be in that it's a real world project, and not a hypothetical "well, you could probably just...".
I'm confused about this part. What part of the browser did they want GC and inheritance for? I'd get it if they were writing the UI in this, but the rest of this post is about the JS engine. They weren't going to 1:1 map JS objects to Swift objects and rely on ARC to manage memory, were they?
You can model these with reference counting, but this turned out unfeasible in browsers. There's a great talk from when Blink (Chrome) transitioned from reference counting to GC, which provides a lot more details about these problems in practice: https://www.youtube.com/watch?v=_uxmEyd6uxo
> I'd get it if they were writing the UI in this, but the rest of this post is about the JS engine.
I think this might be the reason they started with the JS engine and not with some more fundamental browser structures. JS object model has these problems, too, but the engine has to solve them in more generic way. All JS objects can just be modeled as some JSObject class/struct where this is handled on the engine level.
DOM and other browser structures are different because the engine has to understand them, so the browser developers have to interact with the GC manually and if you watch the talk above, you'll see that it's quite involved to do even in C++, let alone in Rust, which puts a bunch of restrictions on top of that.
I watched some of his streams on the development of the JIT compiler (what this change set seems to replace) on one of his streams, and was blown away by the quality of Copilot generated suggestions/completions on an (under-represented) domain (x86 opcodes, etc). This was before Claude Code et al, and pretty early-on for LLM tooling.
The inevitable cleanup that will follow this could be done the same way. Refactoring like that can be done in more bite sized chunks, which makes it easier to review what is happening and control how it is done.
this entire project starts to look like "how am i feeling today?" rather than a serious project.
So far this is the first and only shift
EDIT: bramhaag pointed out the error of my ways. Thanks bramhaag!
i had high hopes for ladybird to become an alternative browser anyone with a working C++ compiler could build on whatever platform.
Given it's not launched and it's donor driven, I guess conserving developer time is a key priority? Dual track sucks lots of time?
I've translated it from Rust to V in 45 minutes. Works great:
https://github.com/medvednikov/libjs_v
Compiles in 0.2 seconds on my M5 (compared to Rust's 3.3 seconds).
Rust syntax is a PITA and investing a lot of effort in the language doesn’t seem worth the trouble for an experienced C++ developer, but with AI learning, porting and maintenance all become more accessible. It’s possible to integrate Rust in an existing codebase or write subparts of larger C++ projects in Rust where it makes sense.
I was recently involved in an AI porting effort, but using different languages and the results were fine. Validating and reviewing the code took longer than writing it.
> Porting LibJS
> Our first target was LibJS , Ladybird’s JavaScript engine. The lexer, parser, AST, and bytecode generator are relatively self-contained and have extensive test coverage through test262, which made them a natural starting point.
> Results
> The requirement from the start was byte-for-byte identical output from both pipelines. The result was about 25,000 lines of Rust, and the entire port took about two weeks. The same work would have taken me multiple months to do by hand.
How long until Ladybird begins to impact market dominance for Chrome and Firefox? My guess: Two years.
That's a lot of people contributing.
How many of them will be less willing to contribute in the future, and less productive when they do if a sizable portion is in Rust? Maybe there'll be more contributions and maybe there'll be less. I don't know. If you've managed to develop a community of 1200 developers who are willing to advance the project why upset the applecart?
Ah, but I see they actually haven't done that to most of their code, so maybe it's just a bit of pandering to the hype and fashion.
Naturally this will be somewhat critical, but I need to first put things into context. I do believe that we really need an alternative to Google dominating our digital life. So I don't object that we need alternatives; whether Ladybird will be an alternative, or not, will be shown in the future. Most assuredly we need competition as otherwise the Google empire moves forward like Darth Vader and the empire (but nowhere near as cool as that; I find Google boring and lame. Even skynet in Terminator was more fun than Google. Google just annoys the heck out of me, but back to the topic of browsers).
So with that out of the way ... Ladybird is kind of ... erratic.
Some time ago, perhaps two months or three, Andreas suddenly announced "Swift WILL BE THE FOREVER FUTURE! C++ sucks!!!". People back then were scratching heads. It was not clear why Swift is suddenly our saviour.
Ok, now we learn - "wait ... swift is NOT the future, but RUST is!!!". Ok ... more head-scratching. We are having a deja-vu moment here... but it gets stranger:
"We previously explored Swift, but the C++ interop never quite got there, and platform support outside the Apple ecosystem was limited. Rust is a different story."
and then:
"I used Claude Code and Codex for the translation. This was human-directed, not autonomous code generation"
So ... the expertise will be with regards to ... relying on AI to autogenerate code in ... Rust.
I am not saying this is a 100% fail strategy, mind you. AI can generate useful code, we could see that. But I am beginning to have more and more doubts about the Ladybird project. Add to this the breakage of URLs that are used by thousands or million people world-wide (see the issues reported on the github tracker); or also the fact that, once you scale-up and more and more people use ladybird, will you be able to keep up with issue trackers? Will you ban more people?
In a way it is actually good that I am no longer allowed to make comments on their repository because I can now be a lot more critical and ask questions that the ladybird team will have to evaluate. Will ladybird blend? Will it succeed? Will it fail? Yes, it is way too early to make an evaluation, so we should evaluate in some months or so, perhaps end of this year. But I am pretty certain the criticism will increase, at the least the moment they decide to leave beta (or alpha or whatever model they use; they claimd they want a first working version in this year for Linux users, let's see whether that works).
I'm not sure how I'd feel if I woke up and found a system I worked on had been translated into an another language I'm not neccessarily familiar with. And I'm not sure I'd want to fix an non-idiomatic "mess" just because it's been translated into a language I'm familiar with either (although I suspect they'll have no problem attracting rust developers).