On Wed, Oct 12, 2011 at 1:23 AM, Wookey wookey@wookware.org wrote:
One output from the 11.09 release was a reasonably painless way of cross-building whole images against an archive, which also forms the basis for an auto-crossbuilder.
There is a HOWTO (for building linaro-nano images) here: https://wiki.linaro.org/Platform/DevPlatform/CrossCompile/CrossBuildNano (It uses armel as the example, but should work the same for armhf)
Summary of process
Essentially you can generate a cross-building chroot in one command (using multistrap), chroot into that (using schroot), and give the builder (xbuilder-simple) a list of packages to build - either a pre-generated one for an image, or your own.
It chunters through and builds them all (using xdeb), and leaving build-logs for each package.
Then at the end (from outside the chroot) you cross-generate an image from the debs (using multistrap, but the pile could be input for a different tool if you prefer).
To make this work usefully against a stable (natty) baseline, updated versions of both tools and packages are in two PPAs at: https://launchpad.net/~linaro-foundations/+archive/cross-build-tools and https://launchpad.net/~linaro-foundations/+archive/cross-alip
Caveats
This is currently a technology demonstration in so far as some of the packages needed for a nano image don't successfully cross-build, so you can't actually currently cross-build all of it, but that should be fixed quite soon. Anyone who wants to help with that is very welcome. I've filed current status and remaining bugs here: https://wiki.linaro.org/Platform/DevPlatform/CrossCompile/LinaroNanoStatus
The autobuilder can actually run just as well using pdebuild-cross as xdeb to do the build-work, but that's not been tested for a while and is not covered in the HOWTO.
The existing xbuilder is pretty stupid (that's why it's called xbuilder-simple) and it does not yet fully ensure a clean build environment every time (when using xdeb, it should if using pbuilder-cross), but it does enough to work reasonably well in practice. A more rigorous environment reset is on the list of improvements RSN.
Ongoing work
The current focus is on getting the remaining packages cross-building so that the whole process works to completeion without cheating by bringing in pre-built packages from the existing archive (That's a useful way to proceed if you want to use this tech today - just adjust the multistrap config to include the base natty armel/armhf archive too)
Once this is completed I'll be setting up a continuously-running autobuilder so that the cross-buildability or otherwise of packages can be more easily discovered and more people can get involved in fixing up packages so that cross-building of larger images becomes realistic.
Nice. So with the proper setup I could inject a different GCC and use this as a compiler testsuite? Perhaps with NEON and -O3 on by default?
I know we don't support it, but could it build an ARMv5 subset of Ubuntu?
-- Michael