(Crosstoolchain documentation is now collected and indexed on CrossToolchains)

Building a Cross Compiler

Very few people need to build a cross-toolchain. It is a complicated business and unless you are doing something really quite obscure you should just install a suitable apt-able toolchain. Installation info is on CrossToolchains.

We'll say that again: MOST PEOPLE SHOULDN'T BE BUILDING THEIR OWN CROSS-TOOLCHAIN - THEY SHOULD JUST INSTALL A PRE-BUILT ONE LIKE ANY OTHER PACKAGE.

But there are reasons why you might need to do this.

I really do want to build a cross compiler

Pick the most relevant heading from the list below.

I want a combination of BUILD x HOST not in Debian on unstable

HOST is a debian release architecture

If HOST is a debian release architecture then this is fairly straightforward:

apt-get install cross-gcc-dev

This is available from jessie (Debian 8) onwards

TARGET_LIST=<hostarch> cross-gcc-gensource <gccver>

Fill in your own <hostarch> and <gccver> above. (e.g. TARGET_LIST="armel armhf" cross-gcc-gensource 4.9) In jessie only '4.9' is supported as a gcc version.

This will generate (in a directory called cross-gcc-packages-<buildarch>) a cross-gcc-<gccver>-<arch> source package for each arch in the TARGET_LIST.

cd cross-gcc-<gccver>-<arch>
sbuild -d jessie 

You will need sbuild 0.64.3 or later installed, and a suitable chroot or build env for the target suite.

A more manual build, probably best done in a chroot, could be

cd packages/cross-gcc-4.9-<hostarch>
dpkg --add-architecture <hostarch>
apt-get update
[install build-deps]
dpkg-buildpackage

(This essentially automates the procedure described on MultiarchCrossToolchainBuild).

HOST is not a debian release architecture

If HOST is not a debian release architecture (debian-ports architecture or a new arch), then it may be much harder because you need to do a full kernel/libc/gcc bootstrap. cross-toolchain-base packages exist in Ubuntu for this for some architectures, but the procedure is broken in Debian at the time of writing (May 2015) so you'll need to fiddle with patches. We do hope to have this working soon.

I want the very latest arm support

Linaro's cross-toolchains (tarball install, sadly) are very up to date with patches and support, and may well be useful. But they are supplied as a binary tarball, not as debian packages.

I want toolchain packages for wheezy

The packages on emdebian.org aimed at wheezy have been uninstallable for a long time. Install buildcross from experimental and use that to build your own.

<some instructions here would be helpful>