How to build for Apple Silicon on GitHub Actions

[chriskilding]

I am working on a Node package which has Apple Silicon as one of its target architectures.

The auto-generated NAPI-RS GitHub Actions workflow makes sense to me when building for x64, but not for other architectures...

This is how it builds for Intel Macs:

- host: macos-latest
  target: x86_64-apple-darwin
  architecture: x64
  build: |
    yarn build
    strip -x *.node

While this is how it builds for Apple Silicon:

 - host: macos-latest
  target: aarch64-apple-darwin
  build: |
    sudo rm -Rf /Library/Developer/CommandLineTools/SDKs/*;
    export CC=$(xcrun -f clang);
    export CXX=$(xcrun -f clang++);
    SYSROOT=$(xcrun --sdk macosx --show-sdk-path);
    export CFLAGS="-isysroot $SYSROOT -isystem $SYSROOT";
    yarn build --target aarch64-apple-darwin
    strip -x *.node

Given that GitHub Actions only has Intel Mac runners at the moment, I don't see anything in the build instructions that would produce an Apple Silicon binary. It's compiling the npm/darwin-arm64 submodule, but I would expect the output to contain an Intel binary.

Could someone enlighten me as to how this works?

[Brooooooklyn]

It's compiling the npm/darwin-arm64 submodule, but I would expect the output to contain an Intel binary.

Intel macOS could compile Arm64 macOS binaries, the opposite is not possible. So while you are running cargo build --target aarch64-apple-darwin on Intel macOS, it will produce arm64 binary, not x86_64.

[chriskilding]

Thanks! I'd also overlooked the installation of the aarch64 target in actions-rs/toolchain (which enables Cargo to actually compile for that architecture).