Policies/CMake Coding Style
This document describes the recommended coding style for CMake files in KDE, i.e. CMakeLists.txt files and *.cmake files.
Indent all code correctly, i.e. the body of
- function/endfunction (CMake 2.6)
Use spaces for indenting, 2, 3 or 4 spaces preferably. Use the same amount of spaces for indenting as is used in the rest of the file. Do not use tabs.
CMake commands are case-insensitive (only the commands, not the arguments or variable names). So all the following versions work:
add_executable(foo foo.c) ADD_EXECUTABLE(bar bar.c) Add_Executable(hello hello.c) aDd_ExEcUtAbLe(blub blub.c)
But this would be ugly.
In KDE the all-lowercase style is preferred. The all-uppercase style is also ok. Mixing upper- and lowercase should not be done in KDE CMake files. Although all-lowercase is preferred, if a file is apparently in all-uppercase style, then stay consistent and also use all-uppercase in this file.
(Not) Using pkg-config
You are free to use pkg-config in FindXXX.cmake modules, as long as the following conditions are met:
- the FindXXX.cmake must also work without pkg-config, as long as the package is either installed to one of the default locations (as /usr or /usr/local) or if CMAKE_PREFIX_PATH is set accordingly
- use only FIND_PACKAGE(PkgConfig), don't use INCLUDE(UsePkgConfig), this one is deprecated
- make sure the variables created by PKG_CHECK_MODULES() are all prefixed with "PC_", so they don't mix up with other variables, e.g. set via FIND_PATH() etc.
- FindLibXml2.cmake as shipped with CMake 2.8.5 is a good example how pkg-config should be handled
- putting something like if(NOT WIN32) around the pkg-config stuff is not necessary (and should be removed if it is somewhere). If pkg-config is not found, e.g. on Windows, the macros simply do nothing.
Writing CMake Find-modules
- Follow the style guide from CMake when writing some FindFoo.cmake module:
- For checking the results inside the Find-module, the macro find_package_handle_standard_args() (coming with CMake) should be used, using the new extended syntax, which supports also version checking.
- Micro-optimizations like
if(FOO_LIBRARY AND FOO_INCLUDE_DIR) set(FOO_FOUND TRUE) else() ... execute the whole find-logic endif()
should be removed, the find-logic should be executed always. These shortcuts can cause problems e.g. when the same file is used from multiple directories but e.g. with different required versions or components etc.