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macOS Cross Compiler

Caution

If you're using this for a production use-case you should fork this project and build the image yourself

This project allows you to cross-compile code on Linux that will be executed on macOS. This can be very useful for CI environments where you want to build for macOS, but you don't want to go through the trouble (and cost) of setting up a macOS environment.

It supports:

  • ✅ C
  • ✅ C++
  • ✅ Fortran
  • ✅ Rust (through Zig)

Support for Objective C and Objective C++ may work out-of-the-box, but this is not tested.

Note

This project is focused on supporting newer versions of macOS and C, C++, Fortran, and Rust. Versions older than macOS 13 (Ventura) are not well tested, though they should work fine.

macOS system libraries and headers are provided with the Docker image. This should be suitable for compiling standalone macOS programs and possibly native macOS applications.

The cross-compilers are available as a Docker image. This is easiest way to distribute the project since there are so many host dependencies. If you are interested in using this without Docker, you should take a look at osxcross which forms the base of this project.

The Docker image is available at ghcr.io/shepherdjerred/macos-cross-compiler.

Quick Start

Install the requirements below, then follow the instructions in the usage section.

Host Requirements

  • Docker

Usage

Important

The Docker image is quite large. It includes several compilers and the macOS SDK.

# Start a Docker container using the Docker image.
# Replace `$PWD/samples` with the path to the source you want to compile.
$ docker run --platform=linux/amd64 \
  -v $PWD/samples:/workspace \
  --rm \
  -it \
  ghcr.io/shepherdjerred/macos-cross-compiler:latest \
  /bin/bash

# Now that you're inside of the Docker container, you can run the compilers.

# Compile using gcc
## targeting darwin arm64
$ aarch64-apple-darwin24-gcc hello.c -o hello
$ aarch64-apple-darwin24-g++ hello.cpp -o hello
## targeting darwin x86_64
$ x86_64-apple-darwin24-gcc hello.c -o hello
$ x86_64-apple-darwin24-g++ hello.cpp -o hello

# Compile using clang
## for darwin arm64
$ aarch64-apple-darwin24-clang --target=aarch64-apple-darwin24 hello.c -o hello
$ aarch64-apple-darwin24-clang++ --target=aarch64-apple-darwin24 hello.cpp -o hello
## for darwin x86_64
$ x86_64-apple-darwin24-clang --target=x86_64-apple-darwin24 hello.c -o hello
$ x86_64-apple-darwin24-clang++ --target=x86_64-apple-darwin24 hello.cpp -o hello

# Compile using gfortran
## for darwin arm64
$ aarch64-apple-darwin24-gfortran hello.f90 -o hello
## for darwin x86_64
$ x86_64-apple-darwin24-gfortran hello.f90 -o hello

# Compile using Zig
## C targeting darwin arm64 (change aarch64 -> x86_64 to target amd64)
$ zig cc \
    -target aarch64-macos \
    --sysroot=/sdk \
    -I/sdk/usr/include \
    -L/sdk/usr/lib \
    -F/sdk/System/Library/Frameworks \
    -framework CoreFoundation \
    -o hello hello.c

## Rust targeting darwin arm64 (change aarch64 -> x86_64 to target amd64)
$ export CC=zig-cc-aarch64-macos
$ cd rust && cargo build --target aarch64-apple-darwin

Rust

Support for Rust requires a bit of project configuration.

# .cargo/config.toml
[build]
[target.aarch64-apple-darwin]
linker = "zig-cc-aarch64-macos"

[target.x86_64-apple-darwin]
linker = "zig-cc-x86_64-macos"

Once configured, you can run cargo after setting the CC variable:

export CC="zig-cc-x86_64-macos"
cargo build --target x86_64-apple-darwin

export CC="zig-cc-aarch64-macos"
cargo build --target aarch64-apple-darwin

C, C++ and Fortran Compiler Executables

The table below shows the name of the executable for each architecture/compiler pair.

Note

The target kernel version is darwin24. You'll need to build a new Docker image if you want to support a different kernel version.

aarch64
clang aarch64-apple-darwin24-clang
clang++ aarch64-apple-darwin24-clang++
gcc aarch64-apple-darwin24-gcc
g++ aarch64-apple-darwin24-g++
gfortran aarch64-apple-darwin24-gfortran

The relevant compilers are located at /osxcross/bin and /gcc/bin. Both these directories are already on the PATH in the Docker container.

cctools

This project compiles cctools, which is Apple's version of binutils. These programs are low-level utilities that are used by compilers, such as the archiver ar, the loader ld, and the assembler as.

You probably don't need to run these programs directly, but if you do they are located at /cctools/bin, and they are also on the PATH.

Complete tool list:

  • ObjectDump
  • ar
  • as
  • bitcode_strip
  • check_dylib
  • checksyms
  • cmpdylib
  • codesign_allocate
  • ctf_insert
  • dyldinfo
  • install_name_tool
  • ld
  • libtool
  • lipo
  • machocheck
  • makerelocs
  • mtoc
  • mtor
  • nm
  • nmedit
  • otool
  • pagestuff
  • ranlib
  • redo_prebinding
  • seg_addr_table
  • seg_hack
  • segedit
  • size
  • strings
  • strip
  • unwinddump
  • vtool

Code Signing, Notarizing, and Universal Binaries

Code signing (but not notarizing) should be possible with this project, but it is untested. Building universal binaries should also be possible, but again, this is not tested.

The rcodesign has been recommended as a way to sign and notarize binaries for macOS.

Target Compatibility

This project can build for macOS on both x86_64 and aarch64 archtictures, regardless of the host architecture.

Linux x86_64 Linux arm64
macOS x86_64 ✅ ✅
macOS aarch64 ✅ ✅

Note

aarch64 is Apple's internal name for arm64. They're used interchangably, but aarch64 is more correct when referring to macOS on arm64.

This project supports the following languages:

  • C (up to C 23)
  • C++ (up to C++ 23)
  • Fortran (up to Fortran 2023)
  • Rust (any version)

This project supports the following versions of macOS:

  • ✅ macOS 11 Big Sur
  • ✅ macOS 12 Monterey
  • ✅ macOS 13 Ventura
  • ✅ macOS 14 Sonoma
  • ✅ macOS 15 Seqouia

Support for macOS 15 Seqouia has not been extensively tested. The Docker image uses the 15.0 SDK by default.

Important

This project is tested on modern verisons of macOS, Clang, and GCC. It has not been tested with older versions of these softwares. If you need compatabiltiy with older versions, check out the osxcross project.

Xcode SDK

This Docker image bundles the Xcode SDK from joseluisq/macosx-sdks. Please familiarize yourself with the SDK's terms of service.

Technical Details

This repository is essentially a wrapper around the following projects:

These resources were helpful when working on this project:

The Zig and Rust portion were informed by these resources:

Development

The Docker images for this repository are built with Earthly.

Tip

Building GCC is compute and memory intense. You can adjust the number of parallel tasks by passing a --cores=<number> argument to any command, e.g. earthly +image --cores=4. In my experience you'll need a lot of memory if you want to use all of your cores. I've had success by setting this value to about half as many cores as my CPU. You should lower the value if your machine stalls.

# Create a Docker image tagged as `shepherdjerred/macos-cross-compiler`
# The first run will take ~20 minutes on an M1 MacBook.
# Subsequent runs are faster.
earthly +image

# Verify that the compilers work correctly
earthly +test

# If you're on macOS, try actually running the binaries
earthly +validate

Inspiration

This project would not have been possible without the osxcross project.