This is being worked on, please maintain your patience. I have successfully done this before but I don't remember what I did, so I will have to recreate a lot of stuff.
- a mind so deadset on cross-compiling you won't stop to think
- the Xcode .dmg for your target OS X version
- root access to your build system
- a good processor and a lot of RAM
The following should be done on the host system first. Download the Xcode DMG, and use dmg2img to convert it to an IMG. Mount the IMG, and put the .pkg files into the chroot somewhere. I'm using /mnt/apple.
Making the chroot
I used Ubuntu 14.04 "Trusty Tahr" for doing the initial chroot. The process was as follows:
apt-get install dchroot debootstrap
Then edit /etc/schroot/schroot.conf with your favourite text editor, and add this at the end:
[trusty] description=Ubuntu Trusty location=/var/chroot priority=3 users=your_username groups=sbuild root-groups=root
Install a base system:
sudo debootstrap --variant=buildd --arch amd64 trusty /var/chroot/ mirror.url.com/ubuntu/
where mirror.url.com/ubuntu/ can be any of these mirrors.
Now copy your resolv.conf for internet access (required):
sudo cp /etc/resolv.conf /var/chroot/etc/resolv.conf
Bind your procfs into the chroot for gnustep:
sudo mount -o bind /proc /var/chroot/proc
Finally, chroot into your target:
sudo chroot /var/chroot
You should now have a working chroot, free for you to destroy as you see fit. (from https://help.ubuntu.com/community/BasicChroot)
To avoid pointless warnings about missing locales, do this:
apt-get install language-pack-en
Install some packages to start off with:
apt-get install sudo nano vim bzr subversion groff man-db
Edit your /etc/apt/sources.list to include the universe source and update:
deb mirror.url.com/ubuntu/ trusty main deb-src mirror.url.com/ubuntu/ trusty main deb mirror.url.com/ubuntu/ trusty universe deb-src mirror.url.com/ubuntu/ trusty universe
Now install gnustep:
apt-get install gnustep gnustep-devel
This may take a while.
NOTE: There is a bug with building cross-compilers for OS X.
cd /usr/src svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm cd llvm/tools svn co http://llvm.org/svn/llvm-project/cfe/trunk clang cd ..; mkdir build; cd build ../configure --prefix=/usr/clang_3_4 --enable-optimized --enable-targets=x86_64,x86 \ --disable-compiler-version-checks --host=x86_64-unknown-linux-gnu --build=x86_64-unknown-linux-gnu \ --target=x86_64-apple-darwin11.4.2 make -j4 make install
To tease the headers out of the Xcode so that we can compile anything, we need to install the xar archiver, which is not packaged in Trusty.
wget https://xar.googlecode.com/files/xar-1.5.2.tar.gz tar -xvf xar-1.5.2.tar.gz apt-get install libxml2-dev libssl-dev libbz2-dev cd xar-1.5.2; ./configure make; make install
Now go to the location of your PKG files. Each one needs to be extracted, and then the payload needs to be extracted too.
cd /mnt/apple mkdir DeveloperToolsCLI cd DeveloperToolsCLI xar -xvf ../DeveloperToolsCLI.pkg
Extract the payload (gzip doesn't really like unnamed files)
mv ./Payload ./Payload.gz gunzip ./Payload.gz
The resulting file is a compressed CPIO archive. Extract that too:
mkdir Contents; cd Contents cpio -idv < ../Payload
Okay, finally. Now we can figure out what's going where.
./System and ./Library are fine. We can just copy those over:
cp -R ./System /System cp -R ./Library /Library
But ./usr is tricky — we might end up overwriting some sort of important file if we try just blatantly overwriting our /usr. So, what do we do? Scan the include paths for clang, and see what we can get away with, of course.
Next step: APSL headers for OSX, from Xcode, and then add libc++ compile instructions