Show HN: Rust Toolchain for iOS Bitcode

Apple requires bitcode submissions for tvOS and watchOS, this has effectively meant that you needed Apple’s toolchain to build and distribute binaries for those platforms.

Bitcode is an intermediate format produced by LLVM, which allows for optimization passes to be applied to it across different languages. For example, C, C++, Swift, ObjC, and Rust can all benefit from some of the same bitcode optimization passes.

In theory Apple wanted this so they could improve the performance of applications when distributed on some of their platforms, though the benefits and potential of this has been a bit dubious. It did mean that Rust (until this) couldn’t easily target those Apple products.

anonova• 7 years ago

I was under the impression that it wasn't for performance but for distribution, i.e., to optimize for app size. Instead of having a fat binary crosscompiled for different architectures, Apple uses the bitcode to compile and distribute per architecture. It's part of the "app thinning" process.

saagarjha3• 7 years ago

Bitcode also enables your old app to run on new Apple Watch hardware with no recompilation required.

rhodysurf2• 7 years ago

Awesome. I tried tinkering with this a hwile back and failed.

dep_b• 7 years ago

Great work! Is it easy to interact between Swift and Rust or UIKit libraries?

pornel• 7 years ago

Unfortunately, you have to use C or ObjC (or at least the ObjC runtime) as the middleman.

Now that there is a stable Swift ABI, at least it's theoretically possible to add a first-class Swift interoperability support to Rust, but it's a quite a chunk of work that nobody has attempted yet.

Currently the practical approach is to write the UI in Swift and Rust on the back-end, e.g. gif.ski app does it this way: https://github.com/sindresorhus/Gifski

woodrowbarlow• 7 years ago

does apple still require that you submit source code as objective C with your app? i recall google creating a transpiler from java to objective C some years ago so they could use their existing java codebases and still meet apple's requirement for submitting objective C source code.

vardump• 7 years ago

I wasn't aware Apple ever required source code submission? Not at least in iOS projects I was involved with or know about.

Show HN: Rust Toolchain for iOS Bitcode

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