Cross-compiling for iOS on Linux

The procedure for this is somewhat complex and requires a lot of steps, but once you have the environment properly configured it will be easy to compile Godot for iOS anytime you want.

Disclaimer

While it is possible to compile for iOS on a Linux environment, Apple is very restrictive about the tools to be used (especially hardware-wise), allowing pretty much only their products to be used for development. So this is not official. However, a statement from Apple in 2010 says they relaxed some of the App Store review guidelines to allow any tool to be used, as long as the resulting binary does not download any code, which means it should be OK to use the procedure described here and cross-compiling the binary.

Requirements

  • XCode with the iOS SDK (a dmg image)

  • Clang >= 3.5 for your development machine installed and in the PATH. It has to be version >= 3.5 to target arm64 architecture.

  • Fuse for mounting and umounting the dmg image.

  • darling-dmg, which needs to be built from source. The procedure for that is explained below.

    • For building darling-dmg, you’ll need the development packages of the following libraries: fuse, icu, openssl, zlib, bzip2.

  • cctools-port for the needed build tools. The procedure for building is quite peculiar and is described below.

    • This also has some extra dependencies: automake, autogen, libtool.

Configuring the environment

darling-dmg

Clone the repository on your machine:

  1. $ git clone https://github.com/darlinghq/darling-dmg.git

Build it:

  1. $ cd darling-dmg
  2. $ mkdir build
  3. $ cd build
  4. $ cmake .. -DCMAKE_BUILD_TYPE=Release
  5. $ make -j 4  # The number is the amount of cores your processor has, for faster build
  6. $ cd ../..

Preparing the SDK

Mount the XCode image:

  1. $ mkdir xcode
  2. $ ./darling-dmg/build/darling-dmg /path/to/Xcode_7.1.1.dmg xcode
  3. [...]
  4. Everything looks OK, disk mounted

Extract the iOS SDK:

  1. $ mkdir -p iPhoneSDK/iPhoneOS9.1.sdk
  2. $ cp -r xcode/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS.sdk/* iPhoneSDK/iPhoneOS9.1.sdk
  3. $ cp -r xcode/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/* iPhoneSDK/iPhoneOS9.1.sdk/usr/include/c++
  4. $ fusermount -u xcode  # unmount the image

Pack the SDK:

  1. $ cd iPhoneSDK
  2. $ tar -cf - * | xz -9 -c - > iPhoneOS9.1.sdk.tar.xz

Toolchain

Build cctools:

  1. $ git clone https://github.com/tpoechtrager/cctools-port.git
  2. $ cd cctools-port/usage_examples/ios_toolchain
  3. $ ./build.sh /path/iPhoneOS9.1.sdk.tar.xz arm64

Copy the tools to a nicer place. Note that the SCons scripts for building will look under usr/bin inside the directory you provide for the toolchain binaries, so you must copy to such subdirectory, akin to the following commands:

  1. $ mkdir -p /home/user/iostoolchain/usr
  2. $ cp -r target/bin /home/user/iostoolchain/usr/

Now you should have the iOS toolchain binaries in /home/user/iostoolchain/usr/bin.

Compiling Godot for iPhone

Once you’ve done the above steps, you should keep two things in your environment: the built toolchain and the iPhoneOS SDK directory. Those can stay anywhere you want since you have to provide their paths to the SCons build command.

For the iPhone platform to be detected, you need the OSXCROSS_IOS environment variable defined to anything.

  1. $ export OSXCROSS_IOS=anything

Now you can compile for iPhone using SCons like the standard Godot way, with some additional arguments to provide the correct paths:

  1. $ scons -j 4 platform=iphone arch=arm target=release_debug IPHONESDK="/path/to/iPhoneSDK" IPHONEPATH="/path/to/iostoolchain" ios_triple="arm-apple-darwin11-"
  2. $ scons -j 4 platform=iphone arch=arm64 target=release_debug IPHONESDK="/path/to/iPhoneSDK" IPHONEPATH="/path/to/iostoolchain" ios_triple="arm-apple-darwin11-"

Producing fat binaries

Apple requires a fat binary with both architectures (armv7 and arm64) in a single file. To do this, use the arm-apple-darwin11-lipo executable. The following example assumes you are in the root Godot source directory:

  1. $ /path/to/iostoolchain/usr/bin/arm-apple-darwin11-lipo -create bin/libgodot.iphone.opt.debug.arm.a bin/libgodot.iphone.opt.debug.arm64.a -output bin/libgodot.iphone.debug.fat.a
  2. $ /path/to/iostoolchain/usr/bin/arm-apple-darwin11-lipo -create bin/libgodot_camera_module.iphone.opt.debug.arm.a bin/libgodot_camera_module.iphone.opt.debug.arm64.a -output bin/libgodot_camera_module.iphone.debug.fat.a
  3. $ /path/to/iostoolchain/usr/bin/arm-apple-darwin11-lipo -create bin/libgodot_arkit_module.iphone.opt.debug.arm.a bin/libgodot_arkit_module.iphone.opt.debug.arm64.a -output bin/libgodot_arkit_module.iphone.debug.fat.a

Then you will have iOS fat binaries in bin directory.