RPi Zero (armv6) Cross Compilation

This repository contains a working example of cross compilation on a x86_64 host system to the Raspberry Pi Zero (armv6).

Quickstart

First, clone the repository and initialize all submodules. We are using Sentry Native as an example since it provides everything any other possible dependency might have or use - it's compiled from source but requires some dependencies besides the standard library (curl and zlib).

git clone https://github.com/TumbleOwlee/rpizero-cross-compile.git
git submodule update --init --recursive

Next, we have to setup the sysroot and get the cross compiler. Keep in mind that you can not use the cross compilers from the official repositories, since they will most likely have dropped support of armv6 and will be compiled with --with-arch=armv7-a+fp. That makes them useless for the older Raspberry Pi Zero. This repository contains a script that will retrieve the compiler from tttapa/docker-arm-cross-toolchain and will set up the sysroot using a raspbian mirror. Check the script for more details.

Now let's set up the sysroot and get the compilers. Everything will be contained in the ./env subdirectory. Since we have to use qemu-arm-static for the sysroot, we also have to register it to binfmt_misc. Thus, you have to run the following commands.

# Register qemu-arm-static
./exec register

# Install the compiler and set up sysroot
./exec install
# Or alternatively, if you would like to customize some options (see --help)
./exec install --env=./path/to/some/dir --version=bookworm --compiler=12

Keep in mind, if you specify a custom path using --env, you will also have to change the paths in the CMakeLists.txt.

That's all. Finally you just have to add the following lines to your CMakeLists.txt.

set(CMAKE_SYSROOT "${CMAKE_CURRENT_SOURCE_DIR}/env/chroot/armv6")
set(CMAKE_FIND_ROOT_PATH "${CMAKE_SYSROOT}")
set(CMAKE_TOOLCHAIN_FILE "${CMAKE_CURRENT_SOURCE_DIR}/env/compiler/armv6/x-tools/armv6-rpi-linux-gnueabihf/armv6-rpi-linux-gnueabihf.toolchain.cmake")

If you would like to unregister the qemu-arm-static, just execute ./exec unregister.

In case you apply this setup to your own project with other or additional dependencies, you will have to install them in your sysroot. You can run apt-get install in your sysroot, using the following command.

sudo chroot ./env/chroot/armv6 /use/bin/apt-get install <packages>