Hacker News

Any resources you'd recommend for learning about reasoning about the security of code?

I've always wondered if JS engines could rewrite those array functions at compile time, like this: https://github.com/SomeRanDev/Haxe-MagicArrayTools

Though, it probably wouldn't work if user code modified the Array prototype.

The work discussed in this post shipped in the OS last year (fall 2025), so nothing here is dependent on very recent changes.

Average swift experience

Alexandre Colucci has published a series of articles analysing the use of Swift in iOS and macOS by Apple here:

https://blog.timac.org/categories/reverse-engineering/

And frequently discussed on Hacker News:

https://hn.algolia.com/?dateRange=all&page=0&prefix=false&qu...

They’ve been doing it for years. I don’t remember how we first knew, but I know they’ve been using Swift in kernels for at least some of the other chips like the Secure Enclave or whatever.

I’m not sure exactly which. I assume it’s some of the code and not all. But it’s not new in the abstract.

That said I don’t think I’ve heard of it in the kernel of MacOS on the main processor. That may be new.

Either way this is certainly the most concrete announcement I remember them ever giving on this stuff.

Curious the direction of Webkit as there was a nebulous mention of select portions being rewritten from C++ to Swift. And yet, the new ECMAScript module (ESM) loader for Safari 27 is implemented in C++ (https://webkit.org/blog/17967/news-from-wwdc26-webkit-in-saf...).

What does RIS stand for?

I'm also here :)

Why is it interesting?

Its a set cover problem, and is NP-hard. 4100 of something probably runs nicely in your laptop in a reasonable amount of time.

Russinovitch (Azure's CTO/CISO) gave a speech at RustConf 2025 and mentions it(DirectWriteCore) took 2 engineers 6 months resulting in 154K LOC and 5-15 percent performance increase for font shaping. https://www.youtube.com/watch?v=uDtMuS7BExE&list=PL2b0df3jKK...

Rust doesn't have an ABI [1]. Swift needed one to be a useable application language:

https://faultlore.com/blah/swift-abi/ (written by a core Rust developer)

[1] apart from the basic/universal C one, which prevents exposing any useful Rust semantics over the interface

One of the genius things about Swift is its interop with Objective C. Made the switch over considerably easier for developers. I’m not sure what that looks like in a Rust world.

Rust is also just a more complex language. I’m not convinced the benefits would have been worth it.

Modern Swift borrows a lot from Rust! And it also has its own benefits, both ergonomic and also supporting eg generic in dynamic libraries

Swift takes the right approach in language ergonomics, many of its use cases would be much harder with explicit .clone() all over the place, lack of back references, no standard ABI for binary libraries, interop with Objective-C and C++, no standard concurrency runtime, or error handling types.

Rust 2026 roadmap has language ergonomics on it for a reason.

That said, outside Apple ecosystem you probably better with Rust, or if one has no GC issues, OCaml, Haskell, F#, Scala, C#.

Apple has a runtime system that looks a lot like smalltalk. Everything at that layer is dynamic. They needed a language that could seamlessly interact with that system.

There are dozens of us! Dozens!

Vello has been a big inspiration and source of knowledge for my own webgpu text renderer, thank you for that!

> high performance text

Just strings or rendering strings?

If the latter, who are the other members of the club?

While hinting is disabled for most fonts, there are some fonts that require hinting to render correctly. We have to support hinting for those fonts, and it was easier to make it secure by rewriting hinting in Swift than it would have been to comprehensively identify every font created by those foundries.

My last 1080p monitor was around 20 years ago. I have trouble comprehending people still use them regularly.

macOS has been drawing unhinted text for an eternity, and for those who can tolerate it on low-DPI screens, it's a great thing: the letter shapes look the same at all sizes, and the spacing between letters is consistent at all sizes.

Retina displays were introduced more than a decade ago. Why should Apple still support outdated technology after such a long time?

If you work with text and fine UI elements, do yourself a favour and get proper tools for the job. Get an ergonomic mouse and a good keyboard while you're at it. In every other field professionals use high quality tools to do their jobs, IT shouldn't be any different.

A plumber has equipment worth tens of thousands of dollars, while IT professionals think it's outrageous to pay a few hundred for equipment which is undeniably an improvement.

I had this problem on the first Apple Silicon Mac Mini in 2020 so it's at least a little older than 2023.

I assure you, every inch of the interpreter code has been stared at by humans, a lot. TBH even the assembly generated by it has.

From what I got Apple is using claude code A LOT internally

I mean they’re doing both

There's mention at the end. The models (and Swift itself!) have evolved a lot since this project started, so the early code is largely hand-rolled and the later changes were mostly authored by centaurs (to steal a term from chess).

But I personally reviewed every line that shipped and was absolutely insufferable about testing.