View source for Building Qt 6 from Git

{{LangSwitch}}
[[Category:HowTo]]
[[Category:Developing with Qt]]

This article provides hints for checking out and building the Qt 6 repositories. This is primarily for '''developers who want to contribute to the Qt library itself,''' or who want to try the latest unreleased code.

If you simply want to build a specific release of Qt from source to use the libraries in your own project, you can download the source code from the [http://download.qt.io/official_releases/qt/ Official Releases] page or the [http://download.qt.io/archive/qt/ Archive]. Alternatively, commercial customers can download the Source Packages via the [https://account.qt.io Qt Account] portal.

*To compile Qt Creator, see [[Building Qt Creator from Git]].
*To compile Qt 5, see [[Building Qt 5 from Git]].
*For the ways Linux distributions package Qt 6, see [[Linux distributions that build Qt 6]].

==System Requirements==

*Git ('''>= 1.6.x''')
*CMake ('''>= 3.16''', '''>= 3.18.4''' for Ninja Multi-Config, '''>= 3.19''' for WebEngine, '''>= 3.21.1''' for static Qt builds in Qt 6.2+)
*Ninja
*C++ compiler supporting C++ 17
*Perl ('''>=5.14''')
*Python ('''>=2.6.x''')
*libclang ('''>=10''', prebuilt versions for each OS can be [https://download.qt.io/development_releases/prebuilt/libclang/ downloaded here] or installed through the libclang-dev package on Linux)
*Windows: Visual Studio 2022, Visual Studio 2019, [https://download.qt.io/development_releases/prebuilt/mingw_64/MinGW-w64-x86_64-11.2.0-release-posix-seh-rt_v9-rev1.7z MinGW 11.2]
*Linux: OpenGL developing library (libgl-dev)

==System Requirements - Qt WebEngine and Qt PDF==
Qt WebEngine and Qt PDF have additional build requirements

*Python ('''>=3.6.x''')
*Python html5lib
*Bison, Flex
*GPerf
*Node.js version 8 or later (version 12 or later is recommended)
*Windows: Visual Studio 2019 '''v16.11+''' (required for '''QtWebEngine''' to address an issue with defaulted noexcept operators)
*Windows: Windows 10 SDK '''>= 10.0.19041.0 (version 2004)''' for '''QtWebEngine'''

==Getting the source code==

First clone the top-level Qt git repository:

 $ git clone <nowiki>git://code.qt.io/qt/qt5.git</nowiki>

or (if you're behind a firewall and want to use the https protocol):

 $ git clone <nowiki>https://code.qt.io/qt/qt5.git</nowiki>

''Do not worry about the name mentioning qt5.git. This is also used for Qt 6.''

Then check out the target branch (see [[Branch Guidelines]]).
Latest changes are in <kbd>dev</kbd>, but
you may check out sources of any publicly released and tagged version,
or of any currently active branch.

 $ cd qt5
 $ git checkout dev

In order to build a specific release of Qt, you can checkout the desired tag, for example:

 $ cd qt5
 $ git checkout v6.3.0

for the 6.3.0 release; or you could likewise checkout 6.4 for the 6.4 stabilisation branch.

For commercial-only modules and commercial-only branches of public modules, see [[Getting Commercial Qt Sources]].

===Getting the submodule source code===

As described in the [http://code.qt.io/cgit/qt/qt5.git/tree/README.git README.git], initialize the repository using the <tt>init-repository</tt> script, which clones the various sub-modules of Qt 6.

Relevant options for <tt>init-repository</tt>:

*<tt>--module-subset</tt> : For example, to get modules for Qt Quick development: <tt>--module-subset=qtbase,qtshadertools,qtdeclarative,qtquickcontrols2</tt>. You can always add or remove individual submodules later with <tt>git submodule init/deinit</tt>.
*<tt>--codereview-username <Jira/Gerrit username></tt> : If you plan to contribute to Qt, you may specify your [[Setting_up_Gerrit|codereview username]] (pay attention to capitalization!) so that the git remotes are properly set up. Note that it is recommended to adjust your ssh configuration instead.

 $ cd qt5
 $ perl init-repository

==Configuring and Building==

Qt 6 is built with CMake, and can be configured also by just running ''cmake'' with appropriate options. We provide some convenience scripts though that makes configuring Qt, and individual Qt modules easier.

A build script called <tt>configure</tt> (or <tt>configure.bat</tt> for Windows) will be in the directory that you git cloned the source code into (<tt>~/qt5</tt> if you followed the directions above). You will want to call that script from a different, parallel-level directory, because you do not want to build Qt in the directory that holds the source code. Instead, you should use a "shadow build", meaning you should not build into the source directory. 

 $ mkdir qt6-build
 $ cd qt6-build
 $ ../qt5/configure -prefix /path/to/install
 $ cmake --build . --parallel 4
 $ cmake --install .

Where 4 is number of jobs. You can try your own value or use auto value using --parallel without argument.

On Windows:

 > mkdir qt6-build
 > cd qt6-build
 > ..\qt5\configure.bat -prefix C:\path\to\install
 > cmake --build .
 > cmake --install .

Run <tt>configure -help</tt> to get an overview of available options.

You may also pass CMake options directly to configure:

  > ../qt5/configure -- -DQT_BUILD_TESTS=ON
All options which are specified after a double-dash (--), will be passed verbatim to CMake.

===Developer Builds===

The configure option <kbd>-developer-build</kbd> sets the install prefix to the build directory, so that no install step is necessary. It also changes defaults so that all tests (including tests using private API that is otherwise not exported) can run.

This can take quite some time though. If you do want to be able to build the tests, but only on request, configure with CMake variable <kbd>QT_BUILD_TESTS_BY_DEFAULT=OFF</kbd>:

  $ ../qt5/configure -developer-build -- -DQT_BUILD_TESTS_BY_DEFAULT=OFF
  $ cmake --build . --parallel

Later on you can then build single tests, for instance :

  $ cmake --build . --target tst_qstyle

Use <kbd>ninja -t targets</kbd> to see all the targets that are provided in the build.

See [https://github.com/qt/qtbase/blob/dev/cmake/README.md <kbd>cmake/README.md</kbd>] in the sources for details on how to configure and build Qt 6 with CMake.

===Running Tests===

Once you've built (as long as you you did build with tests enabled), you can run the tests either directly using <kbd>ninja tst_qlocale_check</kbd> (for example, to run <kbd>tests/auto/corelib/text/qlocale/tst_qlocale</kbd>) or via <kbd>ctest</kbd> (see its <kbd>man</kbd> page for further options) like

  $ ctest -V -R qlocale

(for the same example); the parameter to <kbd>-R</kbd> is a regular expression, matching test names.
This includes the test output; if you omit <kbd>-V</kbd> that's skipped and you just get a single-line summary of the test result.

If you want to run only a particular test function, you pass it using the TESTARGS environment variable. For example:
 $ TESTARGS=emptyCtor  ctest -V -R qlocale
And if you want to run a specific test function with a specific data-tag, you provide it after a colon:
 $ TESTARGS=emptyCtor:en_GB  ctest -V -R qlocale