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+Building cross-compiler Debian packages
+---------------------------------------
+
+It is possible to build C and C++ cross compilers and support libraries
+from gcc-4.0 source package. This document describes how to do so.
+Cross-compiler build support is not perfect yet, please send fixes
+and improvements to debian-gcc@lists.debian.org and 
+debian-embedded@lists.debian.org
+
+Before you start, you should probably check available pre-built
+cross-toolchain debs. Available at http://www.emdebian.org
+
+Old patches could be reached at
+  http://zigzag.lvk.cs.msu.su/~nikita/debian/
+  
+If they are no longer there, you may check EmDebian web site at
+  http://www.emdebian.org/
+or ask debian-embedded@lists.debian.org for newer location.
+
+Please check http://bugs.debian.org/391445 if you are about building
+gcc-4.3 or above.
+
+Most of them has been merged with gcc debian sources.
+
+0. What's wrong with toolchain-source approach
+
+Package toolchain-source contains sources for binutils and gcc, as well as
+some support scripts to build cross-compiler packages. They seem to work.
+
+However, there is one fundamental problem with this approach.
+Gcc package is actively maintained and frequently updated. These updates
+do contain bug fixes and improvements, especially for non-x86 architectures.
+Cross-compilers built using toolchain-source will not get those fixes unless
+toolchain-source package is updated after each binutils and gcc update.
+The later is not hapenning in real life. For example, toolchain-source
+was upgraded from gcc-3.2 to gcc-3.3 half a year later than gcc-3.3 became
+Debian default compiler.
+
+Keeping toolchain-source package up-to-date requires lots of work, and seems
+to be a waste of time. It is much better to build cross-compilers directly
+from gcc source package.
+
+
+1. What is needed to build a cross-compiler from gcc-4.3 source
+
+1.1. dpkg-cross package
+
+Dpkg-cross package contains several tools to manage cross-compile environment.
+
+It can convert native debian library and lib-dev packages for the target
+architecture to binary-all packages that keep libraries and headers under
+/usr/$(TARGET)/.
+
+Also it contains helper tools for cross-compiling debian packages. Some of
+these tools are used while building libgcc1 and libstdc++ library packages.
+The resulting library packages follow the same convensions as library packages
+converted by dpkg-cross.
+
+Currently, at least version 1.18 of dpkg-cross is needed for cross-gcc
+package build. Version 1.32 of dpkg-cross is needed in order to build gcc-4.3.
+
+1.2. cross-binutils for the target
+
+You need cross-binutils for your target to build cross-compiler.
+Binutils-multiarch package will not work because it does not provide cross-
+assemblers.
+
+If you don't want to use pre-built cross-binutils packages, you may build
+your own from binutils debian source package, using patches posted to
+bug #231707. Please use the latest of patch versions available there.
+
+Alternatively, you may use toolchain-source package to build cross-binutils
+(but in this case you will probably also want to use toolchain-source
+to build cross-compiler itself). However, multilib'ed cross-compilers may
+not build or work with these binutils.
+
+1.3. libc for target
+
+You also need libc library and development packages for the target
+architecture installed.
+
+To get those, download linux-kernel-headers, libc6, and libc6-dev binary
+debs for your target, convert those using dpkg-cross -b, and install
+resulting -arch-cross debs. Consult dpkg-cross manual page for more
+information.
+
+Building with/for alternative libc's is not supported yet (but this is in
+TODO).
+
+Note that if you plan to use your cross-toolchain to develop kernel drivers
+or similar low-level things, you will probably also need kernel headers
+for the exact kernel version that your target hardware uses.
+
+
+2. Building cross-compiler packages
+
+Get gcc-4.3 source package.
+
+Unpack it using dpkg-source -x, and cd to the package directory.
+
+Set GCC_TARGET environment variable to the target architectire name. Note
+that currently you should use debian architecture name (i.e 'powerpc' or 'arm'),
+not GNU system type (i.e. 'powerpc-linux' or 'arm-linux'). Setting GCC_TARGET
+to GNU system type will cause cross-compiler build to fail.
+
+Instead of setting GCC_TARGET, target architecture name may be put into
+debian/target file. If both GCC_TARGET is defined and debian/target file
+exists, GCC_TARGET is used.
+
+Run debian/rules control. This will change debian/control file,
+adjusting build-depends.  By default, the packages will not depend on the
+system -base package. A variable DEB_CROSS_INDEPENDENT has been merged with DEB_CROSS variable.
+
+You can then build with either
+
+$ GCC_TARGET=[arch] dpkg-buildpackage -rfakeroot
+
+3. Using crosshurd
+
+Jeff Bailey <jbailey@raspberryginger.com> suggests alternate way to setup
+environment to build cross-compiler, using 'crosshurd' package. 
+Crosshurd is like debootstrap but cross-arch, and works on the Hurd,
+Linux and FreeBSD.  (The name is historical).
+
+If you setup your environment with crosshurd, you will need to fix symlinks
+in lib and usr/lib to be relative instead of absolute. For example:
+
+lrwxrwxrwx    1 root     root           20 2004-05-06 23:02 libcom_err.so -> /lib/libcom_err.so.2
+
+Needs to be changed to:
+
+lrwxrwxrwx    1 root     root           20 2004-05-06 23:02 libcom_err.so -> ../../lib/libcom_err.so.2
+
+Also, if you choose this method, set the environment variable 'with_sysroot'
+to point to the ABSOLUTE PATH where the crosshurd was done.
+
+Note however that build-depends of cross-gcc and dependencies in generated
+libgcc1 and libstdc++ packages assume that you use dpkg-cross to set up
+your environment, and may be wrong or incomplete if you use alternate methods.
+But probably you don't care.
+
+--
+Nikita V. Youshchenko <yoush@debian.org> - Jun 2004
+Hector Oron Martinez  <hector.oron@gmail.com> - Oct 2006