#Cmake cheat sheet in markdown
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#Cmake cheat sheet ## quick start 1. first example, see more details at <https://cmake.org/cmake-tutorial/> ``` cmake_minimum_required (VERSION 2.8.0)#cmake grammar evolves, project (testcpp) # define the output executive name add_executable (testcpp testcpp.cpp) #define source to object relation ``` 2. in source build cmdline: `cmake <path to toplevel cmakelists.txt> -G <generator> && make` out of source build is recommended to keep source tree clean: ``` cd dir_of_source_with_toplevel_cmakelists.txt && mkdir build cd build && camke .. &&make make install ``` using `nmake` on windows visual studio build tool, as cmake generate platform specific makefile 3. GUI tool `cmake-gui <path to toplevel cmakelists.txt>` build option can be turn on and off in GUI ``` option(<option_variable> "help string describing option" [initial value]) ``` 4. FindGTK module, work like `pkg-config` to get include and lib path ``` GTK_INCLUDE_DIR - Directories to include to use GTK GTK_LIBRARIES - Files to link against to use GTK GTK_FOUND - GTK was found GTK_GL_FOUND - GTK's GL features were found ``` for more details see <https://cmake.org/Wiki/CMake> ## cmake language syntax cmake is a script language, similar with shell to some extent. see [cmake wiki](https://cmake.org/Wiki/CMake/Language_Syntax) + only one kind of variable, i.e. string, > but it will be interpreted as bool in `IF (var)` or integer `IF (var GREATER 10) ... ENDIF` + variable substitution `${VAR}`, SET and UNSET, `IF(DEFINED x)` + only one kind of data structure: LIST, string sperated by semicolon `SET(var a b c)` is equal to `SET(var "a;b;c")` + quotation mark to reserve sapce "hello world" ``` SET( x a b c ) # stores a list "a;b;c" in x (without quotes) SET( y "a b c" ) # stores a string "a b c" in y (without quotes) MESSAGE( a b c ) # prints "abc" to stdout, automatically concat (without quotes) MESSAGE( ${x} ) # prints "abc" to stdout (without quotes) MESSAGE("${x}") # prints "a;b;c" to stdout (without quotes) MESSAGE( ${y} ) # prints "a b c" to stdout (without quotes) MESSAGE("${y}") # prints "a b c" to stdout (without quotes) ``` + comment by #, escape by \, line continuation by / > but in path string: "http://////www.example.com" > but it is different from bash shell > newline to split list element - cmake variable and command is case insensitive > but UPPER case for command is recommended and varible content like filename is case sensitive - ""(empty string), "NO; N; FALSE; <var>-NOTFOUND; OFF;0;" or lower case is regarded false in IF() - only integer algorithm `MATH(EXPR outputvar expr)` ``` SET( expression 4 LESS 10 ) # ${expression} is now "4;LESS;10" IF( ${expression} ) # expands to IF( 4;LESS;10 ) MESSAGE( "CMake believes that 4 is less than 10." ) ENDIF( ${expression} ) ``` bash shell math: `$((math_expr))` - generate `config.h` from `config.h.cmake` template > by replacing "@var" with var defined in camkelists.txt `MESSAGE( ${x}${y} ) # displays "31"` - function is different from macro whose variables have global scope ## important command and variable <https://cmake.org/Wiki/CMake_Useful_Variables> ### 1.commands + $ENV{HOME} #access to environment variable + EXECUTE_PROCESS(cmd var_to_hold_result) + INSTALL(TARGETS|FILES list_of_f dest) + CONFIGURE_FILE() #generate config.h from config template input file + INCLUDE_DIRECTORY() #subdir with cmakelists.txt + ADD_LIBRARY(), ADD_EXECUTABLE(), add_definitions, add_dependencies + INCLUDE(extra_cmake_file) #as include in c++ for extra functions ### 2. location variables + SET(CMAKE_MODULE_PATH ${PROJECT_SOURCE_DIR}/MyCMakeScripts) > where FIND_PACKAGE(FooBar) can find `findFooBar.cmake` + CMAKE_SOURCE_DIR # top source dir containing the top-level CMakeLists.txt, + CMAKE_BINARY_DIR # top folder to build binary object + CMAKE_CURRENT_LIST_FILE # full path of the current processed cmakelists.txt + CMAKE_INCLUDE_PATH # path to search for header file e.g. `/usr/include` + CMAKE_INSTALL_PREFIX #just as DESTDIR in `make DESTDIR=/home/john install` ### 3. compiler control variables + CMAKE_CXX_COMPILER + CMAKE_BUILD_TYPE # NONE, DEBUG, RELEASE, etc + CMAKE_<Lang>_FLAGS # for build_type NONE + CMAKE_LINK_LIBRARY_CFLAGS + enable C++ standard support in a portable way ``` set(CMAKE_CXX_STANDARD 11) #98, 14, 17 set(CMAKE_CXX_STANDARD_REQUIRED ON) ``` ### 4. predefined platform and compiler detection varibles platform like: WIN32, APPLE, UNIX (linux is UNIX but not APPLE), MYSYS, CYGWIN compilers: MSVC, MINGW, iNTEL; CMAKE_COMPILER_IS_GNUCXX, CLANG ### 5. command line help ```bash cmake --variable-list cmake --command-list cmake --module-list cmake -h #show all generator ``` <https://cmake.org/Wiki/CMake_Useful_Variables> ## Why cmake? cmake is a new language, why should we learn a new language instead of json or python (as in scons)? 1. cmake inherits some conception of traditional unix makefile 2. multiple programming lang support and cross-platform with generators for majourity of IDE tools 3. plenty of official modules like "FindXXX.cmake" 4. speedup by var cache `SET(var value CACHE)` 5. CPACK for binary package and windows NSIS installer generation 6. Generating Dependency Graphs with CMake, `cmake --graphviz=test.dot .` 7. tool to generate cmakelists.txt from scratch or convert from existent build system ## what I do not like - cmake is not a precise or clear script lang - confusing string quotation and substitution - un-intuitive function style programming to c/python programmers - messed up of variable_content and variable - mixed up argument list and keyword in function call, not sep by comma > relies heavily on this fuction to parse function/command input arg `CMAKE_PARSE_ARGUMENTS(<prefix> <options> <one_value_keywords> <multi_value_keywords> args...)` |
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Author: Qingfeng XIA
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