error cross-compiling to ARM
rob at landley.net
Sun Aug 29 18:30:41 UTC 2010
On Saturday 28 August 2010 08:12:20 Denys Vlasenko wrote:
> On Saturday 28 August 2010 12:47, Salim Tyrewala wrote:
> > Hi,
> > I'm new to busybox. I'm having trouble cross-compiling busybox to ARM
> > using arm-elf-gcc. It doesn't find some include files byteswap.h for
> > instance.
Building with a --target=arm-elf-gcc tuple means you're building a compiler
targeting the bare metal, with no Linux support. This means it can build
things that boot on the bare metal, like the u-boot binary, vmlinux, or stuff
where you supply your own OS support as part of the C library
(newlib/libgloss). But it's not set up to build userspace Linux programs.
(It won't automatically link them against crt1.o or libc.so, hasn't got a C
library's header files in its default #include search path, etc.)
> > I can compile natively just fine using native gcc.
> > I'm not sure what is happening differently when I cross-compile. Why
> > isn't the include path include /usr/include where it should find all
> > the headers?
> Whom do you ask? Are people who built your toolchain on this list?
Cross compiling is a giant evil pile of suck that takes a _long_ time to
It's a bit like c++: you can get a very shallow understanding in about 5
minutes, but everything you know is a polite fiction which doesn't match what
actually happens when you move out of the shallow end of the pool. Actually
understanding what _is_ going on under the covers takes weeks to explain and
months if not years to learn. (Meaning having learned lots of it I could sit
down and write up a course on it in a few weeks, but it would take you months
to absorb all the information.)
> > I think I'm doing something stupid. Please help!
> I tried to cross-compiling to arm using Rob's toolchain
> from Aboriginal Linux and it worked. Here's the script:
> set -e
> test -f cross-compiler-armv5l.tar.bz2 \
> || wget
> || http://impactlinux.com/aboriginal/downloads/binaries/cross-compiler-armv
> rm -rf cross-compiler-armv5l
> tar xf cross-compiler-armv5l.tar.bz2
> test -f busybox-1.17.2.tar.bz2 \
> || wget http://busybox.net/downloads/busybox-1.17.2.tar.bz2
> rm -rf busybox-1.17.2
> tar xf busybox-1.17.2.tar.bz2
> cd busybox-1.17.2
> make CROSS_COMPILE="$CROSS_COMPILE" defconfig
>MPILE\":" -i .config make
Just specify CROSS_COMPILE= on the actual make command line. The configure
stage doesn't need to know where it is. (Busybox configure is just doing
feature selection, it should be target-agnostic.)
# Extract the cross compiler and add it to the $PATH.
tar xvjf cross-compiler-armv5l.tar.bz2
# Extract busybox and cd into it.
tar xvjf busybox-1.17.2.tar.bz2
# Build the sucker, letting busybox know it needs to use the "armv5l-"
# prefix on tool names like armv5l-cc and armv5l-strip.
GPLv3: as worthy a successor as The Phantom Menace, as timely as Duke Nukem
Forever, and as welcome as New Coke.
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