Rust toolchain for Xcode-compatible iOS bitcode

In standard releases of Rust, the bitcode in ARM64 iOS targets is often incompatible with Xcode because they use different versions of LLVM. This is a known issue with no clear long-term solution yet.

This repository contains scripts for building and installing a custom Rust nightly toolchain where the Rust compiler's version of LLVM matches Xcode. Software built using this toolchain can be included in bitcode-enabled apps that will install on real iOS devices.

Binary releases of the toolchain will be created periodically and attached to this repository, at least until there is a better upstream solution.

This repository is maintained by Ditto. We use it ourselves and want to share it for the benefit of the Rust iOS community! Please create an issue if you notice any problems.

Pre-compiled releases

Visit the releases page and download a zip file. It will have a name of the form rust-ios-arm64-20xx-xx-xx.zip where the date is the Rust nightly that it is based on.

Unzip the file and open a terminal to the extracted directory. Run the installation script:

./install.sh

This will:

1. Install the toolchain in ~/.rust-ios-arm64/toolchain-YYYY-MM-DD
2. Configure rustup with a custom toolchain under the name ios-arm64.

You can also install and add the toolchain yourself if you don't like these defaults.

Build from source

1. Ensure required build tools are installed. If you are using homebrew: brew install ninja cmake
2. Clone this repository.
3. Review config.sh to make sure the the Rust and LLVM versions are suitable.
4. In a terminal, run ./build.sh. This will clone the Rust and LLVM repositories under build/ and compile them. The toolchain will end up at build/rust-build/build/x86_64-apple-darwin/stage2.
5. Run ./install.sh. This will install the toolchain in ~/.rust-ios-arm64/toolchain-YYYY-MM-DD and add it to rustup, the same as for pre-compiled releases.

Using the toolchain

Build your library like this:

RUSTFLAGS="-Z embed-bitcode" cargo +ios-arm64 build --target aarch64-apple-ios --release --lib

License

The shell scripts in this repository are made available under the permissive Apache 2.0 licence. Refer to the file LICENSE.

Binary releases contain LLVM and Rust. See LICENSE-LLVM and LICENSE-RUST for their respective licenses. These licenses are included in the binary releases.