Good instructions for making a GCC cross compiler?

Question

Hi
I think this might be the best place to ask this since people probably have been making cross compilers. I am interested in trying to make a cross compiler of GCC targetting Plan9/i386. There is an old 3.0 version of GCC (http://cm.bell-labs.com/sources/extra/gcc/) ported to Plan9.
The thing that confuses me a bit about cross compilers is the use of binutils for the target architecture. How does that actually work? The host OS/architecture would not be able to execute those binaries. It feels a bit like a chicken-and-egg issure and I am not really sure how to get started. I have been trying to read up a bit on the PKGBUILDs for cross-arm but the whole theoretical issue of how to actually get the thing working in the first place is still a bit unclear to me.
Some good instructions/links/help would be appreciated
I could post my temporary PKGBUILD here if people want to help out with the actual build...

Answer 1

A small update to my attempts:
This is my binutils package, it has failed at multiple levels during my attempts. The binutils ported to Plan9 are relatively old so some stuff needs to be patched up to build. Now it fails on not being able to recognize arlex.o . This seems a bit odd I think.
# Adapted from cross-arm-elf, cross-i686-pc-gnu and cross-i686-pc-mingw32
pkgname=cross-i386-plan9-binutils
pkgver=2.11.2
pkgrel=1
pkgdesc="The GNU Compiler Collection - Cross compiler for Plan9 i386 target"
arch=('i686' 'x86_64')
license=('GPL')
url="http://plan9.bell-labs.com/wiki/plan9/porting_alien_software_to_plan_9/index.html"
depends=('glibc' 'zlib')
options=('!libtool' '!distcc' '!ccache')
source=('http://plan9.bell-labs.com/sources/extra/gcc/gnusrc.tgz' \
'bucommh.patch')
md5sums=('39d23b7223b68de4cf333205257112ce' \
'2945c4e40dbcd966217ed1349195e312')
_target=i386-lucent-plan9
_sysroot=/usr/lib/cross-${_target}
build() {
rm -rf ${srcdir}/build
mkdir ${srcdir}/build #starting fresh
msg "building and packaging binutils"
cp -ar ${srcdir}/binutils-2.11.2/* ${srcdir}/build/
cd ${srcdir}/build
msg "cheating broken references to Plan9-ported GNU binutils"
ln -s /usr/bin/ar "${_target}-ar"
ln -s /usr/bin/as "${_target}-as"
ln -s /usr/bin/ld "${_target}-ld"
ln -s /usr/bin/ranlib "${_target}-ranlib"
PATH=${srcdir}/build:$PATH
CFLAGS='-O2 -static'
msg "patching up stuff"
cd ${srcdir}/build/binutils
patch bucomm.h -i $srcdir/bucommh.patch
msg "going back to build directory and start configure"
cd ${srcdir}/build
./configure --prefix=${_sysroot} --bindir=/usr/bin \
--with-sysroot=${_sysroot} \
--build=$CHOST --host=$CHOST --target=${_target} \
--with-gcc --with-gnu-as --with-gnu-ld \
--enable-shared --without-included-gettext \
--disable-nls --disable-debug
msg "fixing some corrupt libraries"
cp /usr/lib/libiberty.a ${srcdir}/build/libiberty/
msg "finally making the actual binutils"
cd ${srcdir}/build
make
make DESTDIR=$pkgdir/ install
# clean-up cross compiler root
rm -r ${pkgdir}/${_sysroot}/share/{info,man}
# needed for gcc build
install -dm755 ${pkgdir}/${_sysroot}/include
this is the bucommh.patch:
81c81
< extern char *sbrk ();
> extern void *sbrk ();
Last edited by W.F.Cody (2011-09-13 18:57:17)