Apple internals: Swift in the kernel

Apple's Swift has become the de-facto language for Apple's own developers for a while now, and it seems that with the new operating system releases from the company unveiled during WWDC, Switch is now also being used in the kernel.

Naturally I dropped what I was doing and went grepping through the iOS 27 kernelcache. Alas, nothing came of it. All is not lost though: I found the Embedded Swift runtime in macOS 27, sitting incom.apple.kec.pthreadof all places. Then I went poking around the root filesystem and it turns out Apple gave the whole effort a name: KernelKit.

Let's dissect it.

Josh Maine

It's still quite limited at this time, which makes sense - you don't want to be too crazy with the core of the operating system that runs on god knows how many PCs, smartphones, and other devices. It's also entirely contained within a few kexts as embedded runtimes, and the XNU kernel itself remains entirely C and C++.