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.

This project formed the basis of my work at Posit (formerly RStudio) to provide macOS binaries for R packages through Posit Public Package Manager.

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.

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.

# Run the container
# Note: You'll probably want to bind-mount some files to compile.
# The `samples` directory has some Hello World programs.
$ docker run ghcr.io/shepherdjerred/macos-cross-compiler:latest /bin/bash

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

• Docker

# Start a Docker container using the Docker image.
# Replace `$PWD/samples` with the path to the source you want to compile.
$ docker run \
  -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-darwin22-gcc hello.c -o hello
$ aarch64-apple-darwin22-g++ hello.cpp -o hello
## targeting darwin x86_64
$ x86_64-apple-darwin22-gcc hello.c -o hello
$ x86_64-apple-darwin22-g++ hello.cpp -o hello

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

## C++ targeting darwin arm64(change aarch64 -> x86_64 to target amd64)
$ zig c++ \
    -target aarch64-macos \
    --sysroot=/sdk -I/sdk/usr/include \
    -I/sdk/usr/include/c++/v1/ \
    -L/sdk/usr/lib \
    -lc++ \
    -F/sdk/System/Library/Frameworks \
    -framework CoreFoundation \
    -o hello hello.cpp

## 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

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

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

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

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 (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.

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

This project supports the following languages:

• C (up to C 17)
• C++ (up to C++ 20)
• Fortran (up to Fortran 2018)
• Rust (any version)

This project supports the following versions of macOS:

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

Support for macOS 14 Sonoma has not been extensively tested. macOS 14-specific features can be added by updating the SDK version. The Docker image uses the 13.0 SDK by default.

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

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

The Zig and Rust portion were informed by these resources:

• https://andrewkelley.me/post/zig-cc-powerful-drop-in-replacement-gcc-clang.html
• https://actually.fyi/posts/zig-makes-rust-cross-compilation-just-work/

The Docker images for this repository are built with Earthly.

# 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

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