macOS Cross Compiler

This project allows you to compile C, C++, Fortran, and Rust code on Linux that will be executed on macOS. This project is focused on supporting newer versions of macOS and C, C++, Fortran, and Rust. Older versions are not well tested.

Rust is supported through the Zig subproject

Quick Start

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

Requirements

• Docker
• Earthly
  • Earthly is a combination of Docker and GNU Make. It builds everything in Docker containers, which makes it easy to automatically cache and parallelize builds.
  • Be sure to increase your cache size, otherwise you will see terrible performance building this project. Run the commands below:
    • earthly config global.cache_size_mb 1000000
    • earthly config global.cache_size_pct 70
• Optional: A copy of the macOS SDK in /sdks. See the osxcross documentation about this.

Usage

# Start a Docker container using the image we built earlier
# Replace this with the path to the source you want to compile
docker run -v $PWD/samples:/workspace \
  --rm \
  -it \
  ghcr.io/shepherdjerred/macos-cross-compiler \
  /bin/bash

# Inside of the Docker container
# Compile something using gcc
## for arm64
aarch64-apple-darwin22-gcc hello.c -o hello
aarch64-apple-darwin22-g++ hello.cpp -o hello
## for x86_64
x86_64-apple-darwin22-gcc hello.c -o hello
x86_64-apple-darwin22-g++ hello.cpp -o hello

# Compile using clang
## for arm64
aarch64-apple-darwin22-clang --target=aarch64-apple-darwin22 hello.c -o hello
aarch64-apple-darwin22-clang --target=aarch64-apple-darwin22 hello.cpp -o hello
## for x86_64
x86_64-apple-darwin22-clang --target==x86_64-apple-darwin22 hello.c -o hello
x86_64-apple-darwin22-clang --target==x86_64-apple-darwin22 hello.cpp -o hello

# Compile using gfortran
## for arm64
aarch64-apple-darwin22-gfortran hello.f90 -o hello
## for x86_64
x86_64-apple-darwin22-gfortran hello.f90 -o hello

Compiler Executables

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

Note: By default the target kernel version is darwin22. You'll need to change darwin22 if you choose to compile for another kernel version.

	x86_64	aarch64
clang	x86_64-apple-darwin22-clang	aarch64-apple-darwin22-clang
clang++	x86_64-apple-darwin22-clang++	aarch64-apple-darwin22-clang++
gcc	x86_64-apple-darwin22-gcc	aarch64-apple-darwin22-gcc
g++	x86_64-apple-darwin22-g++	aarch64-apple-darwin22-g++
gfortran	x86_64-apple-darwin22-gfortran	aarch64-apple-darwin22-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.

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

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 17)
• C++ (up to C++ 20)
• Fortran (up to Fortran 2018)

This project supports the following versions of macOS:

• ✅ macOS 11 Big Sur
• ✅ macOS 12 Monterey
• ✅ macOS 13 Ventura

Note: 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.

Technical Details

This repository is essentially a wrapper around the following projects:

• https://github.com/tpoechtrager/apple-libtapi
• https://github.com/tpoechtrager/cctools-port
• https://github.com/tpoechtrager/xar
• https://github.com/iains/gcc-darwin-arm64

These resources were helpful when working on this project:

• https://www.lurklurk.org/linkers/linkers.html
• http://www.yolinux.com/TUTORIALS/LibraryArchives-StaticAndDynamic.html
• https://gist.github.com/loderunner/b6846dd82967ac048439
• http://clarkkromenaker.com/post/library-dynamic-loading-mac/
• https://github.com/qyang-nj/llios

Development

# 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

Inspiration

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