Stretch armhf cross compile

From Technologic Systems Manuals

Debian Stretch provides cross compilers from the Debian apt repository archive for Debian Stretch. An install on a workstation can build for the same release on other architectures. A Linux desktop or laptop PC, virtual machine, or chroot will need to be used for this. Debian Stretch for a workstation can be downloaded from here.

From a Debian workstation (not the target), run these commands to set up the cross compiler:

# Run "lsb_release -a" and verify Debian 9.X is returned.  These instructions are not
# expected to work on any other version or distribution.
su root
# Not needed for the immediate apt-get install, but used
# so we can install package:armhf for cross compiling
dpkg --add-architecture armhf
apt-get update
apt-get install curl build-essential crossbuild-essential-armhf -y

This will install a toolchain that can be used with the prefix "arm-linux-gnueabihf-". The standard GCC tools will start with that name, eg "arm-linux-gnueabihf-gcc".

The toolchain can now compile a simple hello world application. Create hello-world.c on the Debian workstation:

#include <stdio.h>
int main(){
    printf("Hello World\n");
}

To compile this:

arm-linux-gnueabihf-gcc hello-world.c -o hello-world
file hello-world

This will return that the binary created is for ARM. Copy this to the target platform to run it there.

Debian Stretch supports multiarch which can install packages designed for other architectures. On workstations this is how 32-bit and 64-bit support is provided. This can also be used to install armhf packages on an x86 based workstation.

This cross compile environment can link to a shared library from the Debian root. The package would be installed in Debian on the workstation to provide headers and libraries. This is included in most "-dev" packages. When run on the arm target it will also need a copy of the library installed, but it does not need the -dev package.

apt-get install libcurl4-openssl-dev:armhf

# Download the simple.c example from curl:
wget https://raw.githubusercontent.com/bagder/curl/master/docs/examples/simple.c
# After installing the supporting library, curl will link as compiling on the unit.
arm-linux-gnueabihf-gcc simple.c -o simple -lcurl

Copy the binary to the target platform and run on the target. This can be accomplished with network protocols like NFS, SCP, FTP, etc.

If any created binaries do not rely on hardware support like GPIO or CAN, they can be run using 'qemu'.

# using the hello world example from before:
./hello-world
# Returns Exec format error
apt-get install qemu-user-static
./hello-world