# Docker Image for Qt Development and Continuous Integration on x64 and arm64

## Intro

It happens from time to time that I would benefit from having a simple Docker image with all the deps needed to build and run Qt apps on specific Qt versions. For instance, I may need to build some binary on Mac OS for Linux or I may need to have an image for some continuous integration system.

## Problem

I had a look around and there are quite a few projects: some do not provide an arm build, some rely on the Qt official installer, that is a bit tricky to automate and tends to change often, some rely on distro-provided packages, that do not provide every version etc… I’d prefer to have a solid build procedure to build images for any Qt version I want. Also, my CI system runs on arm64, so I’d need a multiarch image, and therefore two different Qt builds. I thought it could be simpler to just build Qt on-the-fly in a Dockerfile but… turned out it is exactly simple.

## Solution

At first I created a Dockerfile to:

1. install all the needed deps on Ubuntu focal;
3. configure;
4. build;
5. install;
6. cleanup.

This proved to be a simple solution, but building Qt for arm on qemu or building on arm took way too much. So I though of a different solution. I created two images:

With the first image Qt can be built and cross-built in a few hours for both x64 and arm64, directly on x64. The builds are then injected into a second multiarch image. This is way faster than building on qemu.

Only one problem left: in Qt 5, crossbuilding Qt results in some Qt tools like qmake to be built for the host arch, which is unacceptable in this case. So, in the second image, a build of the only qtbase module is also needed to build arm64 binaries. Qt 6 works differently instead.

## Result

The code to build Qt and all the images are available at: https://github.com/carlonluca/docker-qt.
The image to build Qt is available at: https://hub.docker.com/repository/docker/carlonluca/qt-builder.
The image to use for app development is available at: https://hub.docker.com/repository/docker/carlonluca/qt-dev.

## Continuous Integration on GitLab with Qt

An example of usage of the dev image is running continuous integration and unit tests on your code on Jenkins or GitLab. For example, I can now run my unit tests in my GitLab instance running on Raspberry Pi 4 with the following code (taken from my project https://github.com/carlonluca/lqobjectserializer):

variables:
GIT_SUBMODULE_STRATEGY: recursive

stages:
- test_qt5
- test_qt6

Test_qt5:
stage: test_qt5
image:
name: "carlonluca/qt-dev:5.15.2"
entrypoint: [""]
script:
- cd LQObjectSerializerTest
- mkdir build
- cd build
- cmake ../qt5
- make
- ./LQObjectSerializerTest
- ./LGithubTestCase

Test_qt6:
stage: test_qt6
image:
name: "carlonluca/qt-dev:6.1.2"
entrypoint: [""]
script:
- cd LQObjectSerializerTest
- mkdir build
- cd build
- cmake ../qt6
- make
- ./LQObjectSerializerTest
- ./LGithubTestCase


These images are still experimental though.
Have fun 😉

Bye!

## 4 thoughts on “Docker Image for Qt Development and Continuous Integration on x64 and arm64”

Hi Luca,
i am interested in your project, but i can’t see the difference between qt-builder and qt-dev.
On the other hand, I tried to launch the docker from qt-dev, but I’m not doing it right as it says it requires an argument.

> docker run carlonluca/qt-dev
/bin/bash: -c: option requires an argument

1. Hello,
qt-builder is used to build Qt itself. It includes all the libraries and the headers needed to build Qt from its sources. qt-dev is instead an image which includes the Qt build (resulting from the builder) and only includes what is needed to build a Qt app and run it (so some dev packages are not needed). A single qt-builder can be used to build many versions of Qt. There are instead qt-dev images for each Qt version.

qt-dev images expect a command (https://github.com/carlonluca/docker-qt/blob/master/Dockerfile_6.x_jammy#L2). For instance:

$docker run -it –rm carlonluca/qt-dev:6.3.2 bash At this point you’ll have your Qt 6.3.2 in /opt:$ docker run –rm carlonluca/qt-dev:6.3.2 “ls /opt/”
Qt-amd64-6.3.2
Qt-arm64-6.3.2