Guidelines and HOWTOs/CMake: Difference between revisions

Latest revision as of 23:18, 7 October 2024

See https://develop.kde.org/docs/getting-started/building/cmake-build

Most KDE software uses CMake as a buildsystem. This page is the starting point for CMake-related documentation for KDE software.

This page contains some tutorials to help you get started on building a CMake-based buildsystem. This is the recommended way of building your software if you use KDE technologies, such as KDE Frameworks.

Beginners

A first CMake project: if you've never even looked at CMake code before, start here.
Using a framework: introduces you to using a KDE Framework - finding the package and linking your program against it.

Intermediate

Creating a library: demonstrates best practices when creating a library with a CMake-based buildsystem (such as a KDE Framework).

Building with CMake in short

If you just want to build a CMake-based project on a UNIX system, the following recipe will do that:

cd /path/to/project/source
mkdir build
cd build
cmake -DCMAKE_INSTALL_PREFIX=/where/to/install/to ..
make
make install

Don't forget to replace both paths. If you want an explanation of what this command does and how to make CMake behave differently, or you want to build on Windows or OS/X, see the building with CMake chapter.

How to debug CMake

See https://cliutils.gitlab.io/modern-cmake/chapters/features/debug.html

Run:

cmake --help

# Go to the directory that is used in order to run CMake.
cd ~/kde/build/kconfig
# Run the usual CMake configure command line.
cmake -B . -S /home/username/kde/src/kate -G Unix\ Makefiles -DCMAKE_EXPORT_COMPILE_COMMANDS:BOOL=ON -DCMAKE_BUILD_TYPE=Debug -DQT_MAJOR_VERSION=6 -DBUILD_WITH_QT6=ON -DBUILD_TESTING=TRUE -DBUILD_WITH_QT6=ON -DCMAKE_CXX_FLAGS:STRING=-pipe -DCMAKE_INSTALL_PREFIX=/home/username/kde/usr
# Says: "Qt5Core". Which is wrong because it should only use Qt6.

# Run a CMake command line with more verbose output. Using the command line parameter:
# --trace-expand
cmake -B . -S /home/username/kde/src/kate -G Unix\ Makefiles -DCMAKE_EXPORT_COMPILE_COMMANDS:BOOL=ON -DCMAKE_BUILD_TYPE=Debug -DQT_MAJOR_VERSION=6 -DBUILD_WITH_QT6=ON -DBUILD_TESTING=TRUE -DBUILD_WITH_QT6=ON -DCMAKE_CXX_FLAGS:STRING=-pipe -DCMAKE_INSTALL_PREFIX=/home/username/kde/usr --trace-expand |& tee ~/a.txt
kate  ~/a.txt &
# Go to the end of the file by pressing "Ctrl + End".
# Important information can be at the end of the file.
# Search for "Qt5". E.g. Search backwards from the end of the file towards the start of the file, i.e. press the button with the tooltip "Jump to the previous match" "Shift+F3".
# Says
# "/usr/lib/x86_64-linux-gnu/cmake/KUserFeedback/KUserFeedbackConfig.cmake(37):  find_package(Qt5 5.15 NO_MODULE REQUIRED COMPONENTS Core Network )"
# which is wrong because we build using kdesrc-build and
# all of the KDE Frameworks that are used in order to build
# should be in ~/kde/usr
# not in /usr.

Useful resources

CMake Resources

You may want to check out the CMake wiki, although beware that it contains quite a bit of out-of-date information.

Reference documentation

Upgrading from KDELibs4

See https://techbase.kde.org/ECM5/IncompatibleChangesKDELibs4ToECM.

FAQs

Mailing lists

The kde-buildsystem mailing list: Discussion of CMake in the KDE community, as well as development of Extra CMake Modules.

@@ Line 1: / Line 1: @@
-This is the central directory of all [http://www.cmake.org CMake]-related pages on TechBase.
+See https://develop.kde.org/docs/getting-started/building/cmake-build
-== KDE4 Specific CMake Documentation==
+Most KDE software uses [http://www.cmake.org CMake] as a buildsystem. This page is the starting point for CMake-related documentation for KDE software.
-;[[Development/Tutorials/CMake|CMake tutorial]]
+This page contains some tutorials to help you get started on building a CMake-based buildsystem. This is the recommended way of building your software if you use KDE technologies, such as KDE Frameworks.
-:''An introduction to using CMake for KDE4''
-;[[Guidelines HOWTOs/CMake_FAQ|KDE's CMake FAQ]]
+==Beginners==
-:''Some Frequently Asked Questions''
-;[[Guidelines HOWTOs/CMake_KDE_4_2 |Changes im the buildsystem with KDE 4.2]]
+* [[/FirstProject|A first CMake project]]: if you've never even looked at CMake code before, start here.
-:''What has changed in KDE 4.2 compared to KDE 4.0/4.1''
+* [[/Frameworks|Using a framework]]: introduces you to using a KDE Framework - finding the package and linking your program against it.
-;[[Policies/CMake_and_Source_Compatibility|Source compatiblity with CMake]]
+==Intermediate==
-:''This page discusses what has to be taken care of in order to stay source compatible on the CMake level.''
-;[[Policies/CMake_Coding_Style|Coding style for CMake files]]
+* [[/Library|Creating a library]]: demonstrates best practices when creating a library with a CMake-based buildsystem (such as a KDE Framework).
-:''Some guidelines how to write CMake scripts in KDE.''
-;[[Development/Tools/Automoc4|Automoc4]]
+== Building with CMake in short ==
-:''Automoc4 documentation.''
-;[http://api.kde.org/cmake/modules.html KDE CMake modules API]
+If you just want to build a CMake-based project on a UNIX system, the following recipe will do that:
-:''Documentation for all CMake modules in kdelibs (generated from kdelibs svn)''
-;[[Guidelines HOWTOs/CMake/Addons for KDE|KDE4 CMake macros and variables]]
+<syntaxhighlight lang="bash">
-:''Documentation for the macros and variables for building KDE4 software, provided by FindKDE4Internal.cmake (manually written)''
+cd /path/to/project/source
+mkdir build
+cd build
+cmake -DCMAKE_INSTALL_PREFIX=/where/to/install/to ..
+make
+make install
+</syntaxhighlight>
-==More Places to learn about CMake==
+Don't forget to replace both paths. If you want an explanation of what this command does and how to make CMake behave differently, or you want to build on Windows or OS/X, see [[/Building | the building with CMake]] chapter.
-Here are some good places to learn about CMake in general:
+==How to debug CMake==
-* [http://www.cmake.org/HTML/Documentation.html CMake Manual]
-* [http://www.cmake.org/Wiki/CMake CMake Wiki]
-* [http://www.cmake.org/Wiki/CMake_HowToDoPlatformChecks CMake System Checks ]
-* [http://www.cmake.org/Wiki/CMake_HowToFindInstalledSoftware Finding Optional Packages ]
-* [http://www.cmake.org/Wiki/HowToBuildKDE4Software KDE 4 Tutorial at the CMake Wiki ]
-* [http://www.cmake.org/Wiki/CMake_FAQ CMake FAQ]
-* [http://www.elpauer.org/stuff/learning_cmake.pdf Slides for the "Learning CMake" seminar]
-* [http://mail.kde.org/pipermail/kde-buildsystem/ The kde-buildsystem Mailing List Archive]
-Also, consider joining the [http://www.cmake.org/mailman/listinfo/cmake CMake mailing list].
+See https://cliutils.gitlab.io/modern-cmake/chapters/features/debug.html
+Run:
+<pre>
+cmake --help
+</pre>
+<pre>
+# Go to the directory that is used in order to run CMake.
+cd ~/kde/build/kconfig
+# Run the usual CMake configure command line.
+cmake -B . -S /home/username/kde/src/kate -G Unix\ Makefiles -DCMAKE_EXPORT_COMPILE_COMMANDS:BOOL=ON -DCMAKE_BUILD_TYPE=Debug -DQT_MAJOR_VERSION=6 -DBUILD_WITH_QT6=ON -DBUILD_TESTING=TRUE -DBUILD_WITH_QT6=ON -DCMAKE_CXX_FLAGS:STRING=-pipe -DCMAKE_INSTALL_PREFIX=/home/username/kde/usr
+# Says: "Qt5Core". Which is wrong because it should only use Qt6.
+# Run a CMake command line with more verbose output. Using the command line parameter:
+# --trace-expand
+cmake -B . -S /home/username/kde/src/kate -G Unix\ Makefiles -DCMAKE_EXPORT_COMPILE_COMMANDS:BOOL=ON -DCMAKE_BUILD_TYPE=Debug -DQT_MAJOR_VERSION=6 -DBUILD_WITH_QT6=ON -DBUILD_TESTING=TRUE -DBUILD_WITH_QT6=ON -DCMAKE_CXX_FLAGS:STRING=-pipe -DCMAKE_INSTALL_PREFIX=/home/username/kde/usr --trace-expand |& tee ~/a.txt
+kate  ~/a.txt &
+# Go to the end of the file by pressing "Ctrl + End".
+# Important information can be at the end of the file.
+# Search for "Qt5". E.g. Search backwards from the end of the file towards the start of the file, i.e. press the button with the tooltip "Jump to the previous match" "Shift+F3".
+# Says
+# "/usr/lib/x86_64-linux-gnu/cmake/KUserFeedback/KUserFeedbackConfig.cmake(37):  find_package(Qt5 5.15 NO_MODULE REQUIRED COMPONENTS Core Network )"
+# which is wrong because we build using kdesrc-build and
+# all of the KDE Frameworks that are used in order to build
+# should be in ~/kde/usr
+# not in /usr.
+</pre>
+==Useful resources==
+[https://cmake.org/resources/ CMake Resources]
+You may want to check out the [https://gitlab.kitware.com/cmake/community/-/wikis/home CMake wiki], although beware that it contains quite a bit of out-of-date information.
+===Reference documentation===
+* [http://www.cmake.org/HTML/Documentation.html CMake's own documentation]
+* [http://api.kde.org/ecm Extra CMake Modules documentation]
+===Upgrading from KDELibs4===
+See https://techbase.kde.org/ECM5/IncompatibleChangesKDELibs4ToECM.
+===FAQs===
+* [[/FAQs|KDE's CMake FAQs]]
+* [https://gitlab.kitware.com/cmake/community/-/wikis/FAQ CMake FAQ on the CMake wiki]
+===Mailing lists===
+;[http://mail.kde.org/pipermail/kde-buildsystem/ The kde-buildsystem mailing list]
+:Discussion of CMake in the KDE community, as well as development of Extra CMake Modules.