macOS Cross toolchain for Linux and *BSD

WHAT IS THE GOAL OF OSXCROSS?

The goal of OSXCross is to provide a well working macOS cross toolchain for
Linux, FreeBSD, OpenBSD, and Android (Termux).

OSXCross works on x86, x86_64, arm and AArch64/arm64,
and is able to target arm64, arm64e, x86_64, x86_64h and i386.

arm64 requires macOS 11.0 SDK (or later).
arm64e requires a recent Apple clang compiler.

There is also a ppc test branch that has recently seen some daylight.

HOW DOES IT WORK?

For cross-compiling for macOS you need

• the Clang/LLVM compiler
• the cctools (lipo, otool, nm, ar, ...) and ld64
• the macOS SDK.

Clang/LLVM is a cross compiler by default and is now available on nearly every Linux distribution, so we just need a proper port of the cctools/ld64 and the macOS SDK.

OSXCross includes a collection of scripts for preparing the SDK and building the cctools/ld64.

It also includes scripts for optionally building

• Clang using gcc (for the case your distribution does not include it),
• an up-to-date vanilla GCC as a cross-compiler for target macOS,
• the "compiler-rt" runtime library, and
• the llvm-dsymutil tool required for debugging.

Note: The "compiler-rt" library can be needed to link code that uses the __builtin_available() runtime version check.

WHAT CAN BE BUILT WITH IT?

Basically everything you can build on macOS with clang/gcc should build with this cross toolchain as well.

PACKET MANAGERS

OSXCross comes with a minimalistic MacPorts Packet Manager. See README.MACPORTS for more.

INSTALLATION:

Move your packaged SDK to the tarballs/ directory.

Then ensure you have the following installed on your system:

Clang 3.9+, cmake, git, patch, Python, libssl-dev (openssl) lzma-dev, libxml2-dev, xz, bzip2, cpio, libbz2, zlib1g-dev and the bash shell.

You can run 'sudo tools/get_dependencies.sh' to get these (and the optional packages) automatically. (outdated)

Optional:

• llvm-devel: For Link Time Optimization support
• llvm-devel: For ld64 -bitcode_bundle support
• uuid-devel: For ld64 -random_uuid support

On Ubuntu trusty you must upgrade CMake to >= 3.2.3 first. Or do this:

    curl -sSL https://cmake.org/files/v3.14/cmake-3.14.5-Linux-x86_64.tar.gz | sudo tar -xzC /opt
    export PATH=/opt/cmake-3.14.5-Linux-x86_64/bin:$PATH

Building Clang

OSXCross uses clang as the default compiler for building its tools, and also as a cross-compiler to create macOS binaries.

In clang there is no difference between cross-compilation and native compilation, so OSXCross can use a normal clang install for both. You can use either a clang installation you already have, or build your own from source.

To build and install your own clang from a recent source tree, using gcc, run:

    ./build_clang.sh # Builds a mainline version of Clang
    ./build_apple_clang.sh # Builds Apple's version of Clang

This installs clang into /usr/local. If you want to install somewhere else, set the INSTALLPREFIX variable. For example:

    INSTALLPREFIX=/opt/clang ./build_clang.sh

Building OSXCross

To build the cross toolchain (using clang), run:

    ./build.sh

This installs the osxcross toolchain into <path>/target. If you want to install somewhere else, set the TARGET_DIR variable. For example:

    TARGET_DIR=/usr/local/osxcross ./build.sh

And/Or, set variable UNATTENDED to 1 to skip the prompt and proceed straight to the build:

    UNATTENDED=1 ./build.sh

(This will search 'tarballs' for your SDK and then build in its own directory.)

Once this is done: add <path>/target/bin to your PATH variable so that you can invoke the cross-compiler.

That's it. See usage examples below.

Building GCC:

If you also want to build GCC as a cross-compiler, you can do that by running:

    ./build_gcc.sh

The script lets you select a GCC version by setting the variable GCC_VERSION. By default you get C and C++ compilers, but you can tell the script to build a Fortran compiler as well:

    GCC_VERSION=5.2.0 ENABLE_FORTRAN=1 ./build_gcc.sh

[A gfortran usage example can be found here]

Before you do this, make sure you have the GCC build depedencies installed on your system.

On debian like systems you can install these using:

    sudo apt-get install gcc g++ zlib1g-dev libmpc-dev libmpfr-dev libgmp-dev

ATTENTION:

OSXCross does not enable -Werror=implicit-function-declaration by default.
You can emulate Xcode 12's behavior by setting the environmental variable
OSXCROSS_ENABLE_WERROR_IMPLICIT_FUNCTION_DECLARATION to 1.

OSXCross links libgcc and libstdc++ statically by default (this affects -foc-use-gcc-libstdc++ too). You can turn this behavior off with OSXCROSS_GCC_NO_STATIC_RUNTIME=1 (env).

The build also creates aliases *-g++-libc++ which link with the clang implementation of the C++ standard library instead of the GCC version. Don't use these variants unless you know what you're doing.

PACKAGING THE SDK:

Please ensure you have read and understood the Xcode license terms before continuing.

The SDKs can be extracted either from full Xcode or from Command Line Tools for Xcode.

Packaging the SDK on recent macOS (Xcode):

1. [Download Xcode: https://developer.apple.com/download/all/?q=xcode] **
2. [Mount Xcode.dmg (Open With -> DiskImageMounter) ***]
3. Run: ./tools/gen_sdk_package.sh (from the OSXCross package)
4. Copy the packaged SDK (*.tar.* or *.pkg) on a USB Stick
5. (On Linux/BSD) Copy or move the SDK into the tarballs/ directory of OSXCross.

**
-- Xcode up to 15 Beta 6 is known to work.
-- Use Firefox if you have problems signing in.

***
-- If you get a dialog with a crossed circle, ignore it.
-- You don't need to install Xcode.

Step 1. and 2. can be skipped if you have Xcode installed.

Packaging the Xcode 4.2 SDK on Snow Leopard:

1. Install a recent version of Bash from MacPorts or Tigerbrew
2. Download Xcode 4.2 for Snow Leopard
3. Mount the disk image with DiskImageMounter or by running hdiutil attach <xcode>.dmg
4. Run: XCODEDIR=/Volumes/Xcode ./tools/gen_sdk_package.sh
5. (On Linux/BSD) Copy or move the SDK into the tarballs/ directory of OSXCross.

Packing the SDK on Linux - Method 1 (Xcode > 8.0):

This method may require up to 45 GB of free disk space.
An SSD is recommended for this method.

1. Download Xcode like described in 'Packaging the SDK on macOS'
2. Install clang, make, libssl-devel, lzma-devel and libxml2-devel
3. Run ./tools/gen_sdk_package_pbzx.sh <xcode>.xip
4. Copy or move the SDK into the tarballs/ directory

Packing the SDK on Linux - Method 2 (works up to Xcode 7.3):

1. Download Xcode like described in 'Packaging the SDK on macOS'
2. Install cmake, libxml2-dev and fuse
3. Run ./tools/gen_sdk_package_darling_dmg.sh <xcode>.dmg
4. Copy or move the SDK into the tarballs/ directory

Packing the SDK on Linux (and others) - Method 3 (works up to Xcode 7.2):

1. Download Xcode like described in 'Packaging the SDK on macOS'
2. Ensure you have clang and make installed
3. Run ./tools/gen_sdk_package_p7zip.sh <xcode>.dmg
4. Copy or move the SDK into the tarballs/ directory

Packing the SDK on Linux - Method 4 (works up to Xcode 4.2):

1. Download Xcode 4.2 for Snow Leopard
2. Ensure you are downloading the "Snow Leopard" version
3. Install dmg2img
4. Run (as root): ./tools/mount_xcode_image.sh /path/to/xcode.dmg
5. Follow the instructions printed by ./tools/mount_xcode_image.sh
6. Copy or move the SDK into the tarballs/ directory

Packaging the SDK from Xcode Command Line Tools on macOS:

1. [Download Xcode Command Line Tools: https://developer.apple.com/download/more] ****
2. [Mount Command_Line_Tools_for_Xcode.dmg (Open With -> DiskImageMounter)]
3. [Install "Command Line Tools.pkg" (Open With -> Installer)]
4. Run: ./tools/gen_sdk_package_tools.sh (from the OSXCross package)
5. Copy the packaged SDK (*.tar.* or *.pkg) on a USB Stick
6. (On Linux/BSD) Copy or move the SDK into the tarballs/ directory of OSXCross.

**** -- Xcode command line tools 12.x are known to work.

Steps 1. to 3. can be skipped if you have Xcode Command line tools already installed (e.g., auto-installed by running git or gcc command from command-line).

Packing the SDK from from Xcode Command Line Tools on Linux:

This method may require up to 45 GB of free disk space. An SSD is recommended for this method.

1. Download Xcode Command Line Tools like described in 'Packaging the SDK from Xcode Command Line Tools on macOS'
2. Install clang, make, libssl-devel, lzma-devel and libxml2-devel
3. Run ./tools/gen_sdk_package_tools_dmg.sh <command_line_tools_for_xcode>.dmg
4. Copy or move the SDK into the tarballs/ directory

USAGE EXAMPLES:

Example. To compile a file called test.cpp, you can run:

x86

• Clang:

  • 32 bit: o32-clang++ test.cpp -O3 -o test OR i386-apple-darwinXX-clang++ test.cpp -O3 -o test
  • 64 bit: o64-clang++ test.cpp -O3 -o test OR x86_64-apple-darwinXX-clang++ test.cpp -O3 -o test

• GCC:

  • 32 bit: o32-g++ test.cpp -O3 -o test OR i386-apple-darwinXX-g++ test.cpp -O3 -o test
  • 64 bit: o64-g++ test.cpp -O3 -o test OR x86_64-apple-darwinXX-g++ test.cpp -O3 -o test

ARM

• Clang:

  • arm64: oa64-clang++ test.cpp -O3 -o test OR arm64-apple-darwinXX-clang++ test.cpp -O3 -o test
  • arm64e: oa64e-clang++ test.cpp -O3 -o test OR arm64e-apple-darwinXX-clang++ test.cpp -O3 -o test

XX= the target version, you can find it out by running osxcross-conf and then see TARGET.

You can use the shortcuts o32-... for i386-apple-darwin..., depending on which you prefer.

I'll continue from here on with o32-clang, but remember, you can simply replace it with o32-gcc or i386-apple-darwin....

Building Makefile based projects:

• make CC=o32-clang CXX=o32-clang++

Building automake based projects:

• CC=o32-clang CXX=o32-clang++ ./configure --host=i386-apple-darwinXX

Building test.cpp with libc++:

Note: libc++ requires macOS 10.7 or later! If you really need C++11 for an older macOS version, then you can do the following:

1. Build GCC so you have an up-to-date libstdc++
2. Build your source code with GCC or clang++-gstdc++ / clang++ -foc-use-gcc-libstdc++

Usage Examples:

• Clang:

  • C++98: o32-clang++ -stdlib=libc++ -std=c++98 test.cpp -o test
  • C++11: o32-clang++ -stdlib=libc++ -std=c++11 test1.cpp -o test
  • C++14: o32-clang++ -stdlib=libc++ -std=c++14 test1.cpp -o test
  • C++17: o32-clang++ -stdlib=libc++ -std=c++17 test1.cpp -o test
  • C++2a: o32-clang++ -stdlib=libc++ -std=c++20 test1.cpp -o test

• Clang (shortcut):

  • C++98: o32-clang++-libc++ -std=c++98 test.cpp -o test
  • C++11: o32-clang++-libc++ -std=c++11 test.cpp -o test
  • C++14: o32-clang++-libc++ -std=c++14 test.cpp -o test
  • C++17: o32-clang++-libc++ -std=c++17 test.cpp -o test
  • C++2a: o32-clang++-libc++ -std=c++20 test.cpp -o test

• GCC

  • C++11: o32-g++-libc++ -std=c++11 test.cpp
  • C++14: o32-g++-libc++ -std=c++14 test.cpp -o test
  • C++17: o32-g++-libc++ -std=c++17 test.cpp -o test
  • C++2a: o32-g++-libc++ -std=c++20 test.cpp -o test

Building test1.cpp and test2.cpp with LTO (Link Time Optimization):

• build the first object file: o32-clang++ test1.cpp -O3 -flto -c
• build the second object file: o32-clang++ test2.cpp -O3 -flto -c
• link them with LTO: o32-clang++ -O3 -flto test1.o test2.o -o test

Building a universal binary:

• Clang:
  • o64-clang++ test.cpp -O3 -arch i386 -arch x86_64 -o test
• GCC:
  • build the 32 bit binary: o32-g++ test.cpp -O3 -o test.i386
  • build the 64 bit binary: o64-g++ test.cpp -O3 -o test.x86_64
  • use lipo to generate the universal binary: x86_64-apple darwinXX-lipo -create test.i386 test.x86_64 -output test

DEPLOYMENT TARGET:

The default deployment target is:

SDK <= 10.13: macOS 10.6
SDK >= 10.14: macOS 10.9

However, there are several ways to override the default value:

1. by passing OSX_VERSION_MIN=10.x to ./build.sh
2. by passing -mmacosx-version-min=10.x to the compiler
3. by setting the MACOSX_DEPLOYMENT_TARGET environment variable

>= 10.9 also defaults to libc++ instead of libstdc++,
this behavior can be overriden by explicitly passing -stdlib=libstdc++ to clang.

x86_64h defaults to macOS 10.8 and requires clang 3.5+.
x86_64h = x86_64 with optimizations for the Intel Haswell Architecture.

PROJECTS USING OSXCROSS:

• multiarch/crossbuild:
  various cross-compilers
  (Systems: Linux, macOS, Windows, Archs: x86_64,i386, arm, ppc, mips)
  in Docker. OSXCross powers the Darwin builds.
• Smartmontools

LICENSE:

• scripts/wrapper: GPLv2
• cctools/ld64: APSL 2.0
• xar: New BSD

CREDITS:

• cjacker for the initial cctools port