Re: Creating debs using a cross-build environment?

On Thu, 2012-02-23 at 14:42 +0100, Hector Oron wrote:
> Hello,
> 
> 2012/2/23 Svante Signell <[email protected]>:
> > On Thu, 2012-02-23 at 13:00 +0100, Hector Oron wrote:
> >> 2012/2/23 Jonathan Nieder <[email protected]>:
> 
> >> Most underlying mechanisms assume Linux kernel, AFAICT, none has
> >> attempted to change those to use another kernel, but that might be
> >> possible changing Linux kernel headers by some other kernel headers.
> 
> > I've looked at this web page (and several other guides and web pages).
> > The Debian web page does not help much in creating a cross compiler for
> > another kernel than GNU/Linux. These steps I already have done and
> > written down for the GNU/Hurd OS. Anybody interested?
> 
> Just for fun, I'd be curious to see.

I'll send to the list soon. There are still some workarounds to solve in
a better way. Maybe you can help here, it's mainly about giving the
correct options to various configure scripts.

> > My questions and aims are:
> > Assuming the cross and target build environment is available, as above.
> >
> > BUILD=x86_64-linux-gnu
> > TARGET=i486-gnu
> > TOOLS=/somewhere/cross_tools
> > SYSROOT=/somewhere/target_tools
> 
> Note: While it is possible to build SYSROOT cross-tools, it is not in
> Debian cross defaults.

OK, it that even a possibility in the future?

> > Current method:
> > ===============
> > apt-get source package
> > mkdir build-package
> > cd build-package
> > ../package/configure --build=$BUILD --host=$HOST (+ other options)
> > make all
> > make install
> > No .deb package is created, all headers, libraries and executables are
> > directly installed in $SYSROOT.
> 
> Not sure, what you mean? What is 'package'? Are you trying to populate $SYSROOT?
> You might be able to do that from binary packages, using debootstrap
> or multistrap.

If I succeed with a cross build, it would be nice to get a .deb package
to copy to the target box and dpkg -i there! Populating sysroot is not
important, except for creating files to install on the target box if deb
creation is not possible. To me debootstrap and multistrap are creating
a (target) base system for use in a chroot. That wouldn't work cross-OS
would it, at least without copying the files to the target and reboot
into the target?

> > With cross-build dpkg-support:
> > ==============================
> > Set up where the cross tools and target headers, libraries and
> > executables are located.
> > cd package
> > DEB_BUILD_GNU_TYPE=$BUILD DEB_HOST_GNU_TYPE=$TARGET dpkg-buildpackage -b
> > That will create .debs to be installed on the target box or in $SYSROOT.
> 
> Actually, not all packages support cross compilation, you might need
> to check, proper way would be by setting -a$ARCH flag. So,
>   dpkg-buildpackage -b -ahurd-i386 (+extra flags)

Haven't tried yet. How is the cross-build environment found by
dpkg-buildpackage?