Cross compiling Qt for embedded platforms

This documentation lists the configurations I personally use when building Qt.

If the latest Qt is not available for your platform, or you're not pleased with it (eg. hardware acceleration is disabled), you'll need to build it manually. You can get the latest officially released source code from the Qt website, from here (select open source, click 'All downloads' on the bottom, then search for 'Source packages'). The general steps and requirements are described in the Qt documentation.

Building Qt takes significant time, about 30-60 minutes on a good desktop PC, depending on the selected components. It requires at least 2 GB of RAM and 6.5 GB free space. Do not try to build it on your $5 board computer.

Instead, you can cross compile Qt. Cross compilation means the program or library you build will run on a different architecture or platform than your own PC. For example, if you're on Linux, you can build programs that will run on Windows, or on a phone or embedded device. For this, you'll need a toolchain, a compiler that generates code for a certain platform, and a sysroot, a collection of libraries from the target device. Getting a toolchain and sysroot is different for every platform; you can find cross compilers for the popular targets, eg. ARMv7-Linux, while for others you might need to build a whole custom GCC. You'll have look around for them for your platform. For the Raspberry Pi cross compilation, this guide was very helpful: https://wiki.qt.io/RaspberryPi2EGLFS. This also shows how you can set up Qt Creator for testing and such.

The configurations below are mainly based on the Debian automatic builds, and the guide mentioned above. If you haven't read the official Qt docs yet, do it now. The configure step produces a detailed status report; make sure everything looks correct. You'll need everything under QML and Qt Quick (except maybe DirectX 12), and depending on your platform, 'EGLFS' under 'QPA backends' and at least one of the 'EGLFS details', that matches your device (eg. EGLFS Rasberry Pi). You might also want the X11 options off, if you won't use it. See configure --help or the documentation for the available options.

Raspbian sysroot

The sysroot used for compilation is based on Raspbian, with the following additional packages installed:

apt-get build-dep -y qt4-x11 libqt5gui5
apt-get install -y libudev-dev libinput-dev libts-dev libxcb-xinerama0-dev libxcb-xinerama0
apt-get install -y libopenal-dev libsqlite3-dev libfontconfig-dev
apt-get install -y libglib2.0-dev gstreamer1.0-omx libgstreamer1.0-dev libgstreamer-plugins-base1.0-dev
apt-get install -y libsmbclient-dev libssh-dev libsdl2-dev

Raspberry Pi 1 / Zero (ARMv6)

toolchain: https://github.com/raspberrypi/tools, cloned to /opt/raspberrypi-tools sysroot: see Raspbian sysroot

../configure \
    -opensource \
    -confirm-license \
    -release \
    -strip \
    -no-rpath \
    -make libs \
    -skip qtwebengine \
    -skip wayland \
    -device linux-rasp-pi-g++ \
    -opengl es2 \
    -device-option CROSS_COMPILE=/opt/raspberrypi-tools/arm-bcm2708/gcc-linaro-arm-linux-gnueabihf-raspbian-x64/bin/arm-linux-gnueabihf- \
    -sysroot /opt/rpi-sysroot \
    -prefix /opt/qt58-rpi1 \
    -extprefix /opt/qt58-rpi1 \
    -hostprefix /opt/qt58-rpi1_hosttools \
    -no-use-gold-linker \
    -openssl \
    -fontconfig \
    -gstreamer 1.0 \
    -no-xcb \
    -no-dbus \
    -no-glib \
    -no-icu \
    -system-zlib \
    -system-libpng \
    -system-libjpeg \
    -system-sqlite \
    -verbose

Raspberry Pi 2 (ARMv7) / 3 (ARMv8, but v7 compatible)

NOTE: The difference is the -device parameter and the output paths.

toolchain: https://github.com/raspberrypi/tools, cloned to /opt/raspberrypi-tools sysroot: see Raspbian sysroot

../configure \
    -opensource \
    -confirm-license \
    -release \
    -strip \
    -no-rpath \
    -make libs \
    -skip qtwebengine \
    -skip wayland \
    -device linux-rasp-pi2-g++ \
    -opengl es2 \
    -device-option CROSS_COMPILE=/opt/raspberrypi-tools/arm-bcm2708/gcc-linaro-arm-linux-gnueabihf-raspbian-x64/bin/arm-linux-gnueabihf- \
    -sysroot /opt/rpi-sysroot \
    -prefix /opt/qt58-rpi2 \
    -extprefix /opt/qt58-rpi2 \
    -hostprefix /opt/qt58-rpi2_hosttools \
    -no-use-gold-linker \
    -openssl \
    -fontconfig \
    -gstreamer 1.0 \
    -no-xcb \
    -no-dbus \
    -no-glib \
    -no-icu \
    -system-zlib \
    -system-libpng \
    -system-libjpeg \
    -system-sqlite \
    -verbose

X11 static build

This was actually a native build, so the cross compilation options aren't needed.

../configure
    -opensource
    -confirm-license
    -release
    -strip
    -no-rpath
    -static
    -c++std c++11
    -make libs
    -skip qtwebengine
    -skip wayland
    -prefix /opt/qt58-x11-static
    -openssl
    -gstreamer 1.0
    -fontconfig
    -no-dbus
    -verbose
    -no-glib
    -qt-zlib
    -platform linux-g++
    -no-icu
    -qpa xcb
    -xcb