wiki:CrossCompiler/Compiling
Last modified 2 years ago

  1. Cross-compiling sources
    1. Simple Makefile-based compilation
      1. Setting up pkg-config
      2. With ./configure
    2. For the Linux kernel
    3. Testing the binaries
    4. Known problems
      1. "CC=arm-linux-gnueabi make" fails on linking
      2. Some programs do not compile

Cross-compiling sources

Simple Makefile-based compilation

Well-written software (warning: this is highly subjective) should compile like this: 

$ make CC=arm-linux-gnueabi-gcc

(adapt if the sources are in another language than C or the architecture is other than arm)

If it fails, check the next section or look in the Known problems part.

Setting up pkg-config

pkg-config can be configured to look into the cross-compilation environment instead of the native one: 

# export PKG_CONFIG_LIBDIR="/usr/arm-linux-gnueabi/usr/lib/pkgconfig:/usr/arm-linux-gnueabi/usr/share/pkgconfig"
# export PKG_CONFIG_SYSROOT_DIR="/usr/arm-linux-gnueabi"

(These two lines can be found in /root/.bashrc, commented.)

This is automatically set in the environment when using hackable:1's trunk/packages/package.sh with the DEBIAN_ARCH option set.

With ./configure

Using the --host flags with software using autoconf/automake (through the ./configure script) should just work. For example, for the Openmoko Freerunner (ARM EABI): 

$ ./configure --host=arm-linux-gnueabi
$ make

In this case, the correct binaries are automatically called when using make.

For the Linux kernel

This will configure the kernel for an ARM platform: 

$ make ARCH=arm menuconfig

And to actually build the kernel: 

$ make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi

Testing the binaries

You may then use your favorite method to upload the binaries to your embedded device:

  • NFS share
  • SSH file uploads

Known problems

"CC=arm-linux-gnueabi make" fails on linking

When you cross-compile sources without packaging them, you may miss some flags, especially LD flags. The following is a possible error message: 

$ CC=arm-linux-gnueabi make
[...]
/usr/lib/gcc/arm-linux-gnueabi/4.3.2/../../../../arm-linux-gnueabi/bin/ld: skipping incompatible /usr/arm-linux-gnueabi/bin/../../lib/libXtst.so when searching for -lXtst
/usr/lib/gcc/arm-linux-gnueabi/4.3.2/../../../../arm-linux-gnueabi/bin/ld: skipping incompatible /usr/arm-linux-gnueabi/bin/../../lib/libXtst.a when searching for -lXtst
/usr/lib/gcc/arm-linux-gnueabi/4.3.2/../../../../arm-linux-gnueabi/bin/ld: cannot find -lXtst
collect2: ld returned 1 exit status

Here, ld looks for the libraries in /usr/lib instead of /usr/arm-linux-gnueabi/usr/lib even if PKG_CONFIG* env vars are correctly set. You should specify: 

CC=arm-linux-gnueabi LDFLAGS="-L/usr/arm-linux-gnueabi/lib -L/usr/arm-linux-gnueabi/usr/lib  -Wl,-rpath-link /usr/arm-linux-gnueabi/lib -Wl,-rpath-link /usr/arm-linux-gnueabi/usr/lib" make

and make sure the Makefile uses them.

Also, if you use libtool, you need to pass -inst-prefix-dir /usr/arm-linux-gnueabi to make and a patch in ltmain.sh as in  here

Some programs do not compile

There may be a number of causes:

  • hard-coded binaries are used to compile or link: native applications may be picked up instead of the cross-compiler, from within badly-written Makefiles for example