Cross-compiling bzip2 for iOS

As detailed in my previous blog post, I showed you how to compile Git using an on-device toolchain. Now, I’ll show you how to do something similar, but instead, on Linux.

First things first, we’re going to need the iOS SDK and Linux Toolchain. You can download the former from this website and the latter from here.

This tutorial assumes you are running Ubuntu 16.04 LTS. If this does not apply to you, then you may need to make some modifications to the following processes.

OK, now that you’ve got the SDK and Toolchain, it’s time to extract them. Suppose my home directory was /home/citrusui. Create two folders in this directory called sdks and toolchain, then unzip the files to these locations accordingly.

Now, its time to download a script that automates the compiling process. Make sure you run this process as root or sudo!

#!/bin/bash rm -rf ~/built/bzip2* VER=1.0.6 CHAIN=~/toolchain/linux/iphone/bin/armv7-apple-darwin11 AR=$CHAIN-ar CC=$CHAIN-clang RANLIB=$CHAIN-ranlib SDK=/home/citrusui/sdks/iPhoneOS9.3.sdk CFLAGS="-arch armv7 -arch arm64 -isysroot $SDK" LDFLAGS="-Wl,-segalign,4000" PREFIX=~/built/bzip2/var/stash/usr apt install bison clang libcurl4-openssl-dev xutils-dev if [ -f bzip2-$VER.tar.gz ] && [ -d bzip2* ]; then echo "Already downloaded." cd bzip2* make clean make install CC="$CC" CFLAGS="$CFLAGS" RANLIB="$RANLIB" AR=$AR LDFLAGS="$LDFLAGS" PREFIX="$PREFIX" cd ~/built/bzip2 lndir var/stash mkdir DEBIAN cd DEBIAN cp ~/build/bzip2-control control sed '/^Version:/ s/$/ $1.0.6/' control cd ../.. dpkg-deb -Zgzip -b bzip2 mv bzip2.deb bzip2_iphoneos-arm.deb exit 0 fi curl -O http://www.bzip.org/$VER/bzip2-$VER.tar.gz echo "Downloading..." tar -xvzf bzip2-$VER.tar.gz cd bzip2* make clean make install CC="$CC" CFLAGS="$CFLAGS" RANLIB="$RANLIB" AR=$AR LDFLAGS="$LDFLAGS" PREFIX="$PREFIX" cd ~/built/bzip2 lndir var/stash mkdir DEBIAN cd DEBIAN cp ~/build/bzip2-control control sed -i '/^Version:/ s/$/1.0.6/' control cd ../.. dpkg-deb -Zgzip -b bzip2 mv bzip2.deb bzip2_iphoneos-arm.deb

All right, what does this script do? Well…

• Clears out cache of any previously “built” versions of bzip2
• Sets the current version of bzip2 (1.0.6)
• Specifies which compiler to use (armv7-apple-darwin11-clang)
• Sets some CFLAGS and LDFLAGS in order to build for iOS
• Installs some dependencies needed for the compile process
• Downloads bzip2 source code
• Unzips source code, and compiles it
• Runs lndir to avoid any issues with Cydia stashing
• Copies the current version of bzip2 (1.0.6) to the Debian control file
• Packages the directory in ~/built/bzip2 into a .deb

You may notice that a file, aptly named “bzip2-control” is specified in this script too. This is a file that you’ll need to add manually, in the same directory that you’ve saved bzip2.sh to. It should look something like this:

Package: bzip2 Priority: important Section: Archiving Maintainer: Your Name <[email protected]> Architecture: iphoneos-arm Version: Description: Freely available high-quality data compressor Homepage: http://www.bzip.org/

Make sure you leave a blank line at the bottom of your control file, or else dpkg-deb will return an error.

Important Note: I left out a step that involves running ldid -S on all of the bzip2 binaries. Without this step, iOS will refuse to run bzip2 (I think).

Hopefully this tutorial helped you cross-compile bzip2 for iOS! Feel free to upload the generated package to your personal Cydia repository. If I manage to get Git to properly cross-compile, I might make a follow-up to the previous blog post.

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