CMake Useful Variables
CMake uses and defines many variables, which can be used in CMakeLists.txt files.
Locations
- CMAKE_BINARY_DIR
- if you are building in-source, this is the same as CMAKE_SOURCE_DIR, otherwise this is the top level directory of your build tree
- CMAKE_COMMAND
- this is the complete path of the cmake which runs currently (e.g. /usr/local/bin/cmake)
- CMAKE_CURRENT_BINARY_DIR
- if you are building in-source, this is the same as CMAKE_CURRENT_SOURCE_DIR, otherwise this is the directory where the compiled or generated files from the current CMakeLists.txt will go to
- CMAKE_CURRENT_LIST_FILE
- this is the filename including the complete path of the file where this variable is used.
- CMAKE_CURRENT_LIST_LINE
- this is linenumber where the variable is used.
CMakeLists.txt contains the PROJECT() command
- CMAKE_CURRENT_SOURCE_DIR
- this is the directory where the currently processed CMakeLists.txt is located in
- CMAKE_FILES_DIRECTORY
- the directory within the current binary directory that contains all the CMake generated files. Typically evaluates to "/CMakeFiles". Note the leading slash for the directory. Typically used with the current binary directory, i.e. ${CMAKE_CURRENT_BINARY_DIR}${CMAKE_FILES_DIRECTORY}
- CMAKE_MODULE_PATH
- tell CMake to search first in directories listed in CMAKE_MODULE_PATH when you use FIND_PACKAGE() or INCLUDE()
SET(CMAKE_MODULE_PATH ${PROJECT_SOURCE_DIR}/MyCMakeScripts)
FIND_PACKAGE(HelloWorld)
- CMAKE_ROOT
- this is the CMake installation directory
- CMAKE_SOURCE_DIR
- this is the directory, from which cmake was started, i.e. the top level source directory
- EXECUTABLE_OUTPUT_PATH
- set this variable to specify a common place where CMake should put all executable files (instead of CMAKE_CURRENT_BINARY_DIR)
SET(EXECUTABLE_OUTPUT_PATH ${PROJECT_BINARY_DIR}/bin) - LIBRARY_OUTPUT_PATH
- set this variable to specify a common place where CMake should put all libraries (instead of CMAKE_CURRENT_BINARY_DIR)
SET(LIBRARY_OUTPUT_PATH ${PROJECT_BINARY_DIR}/lib) - PROJECT_NAME
- the name of the project set by PROJECT() command.
- PROJECT_BINARY_DIR
- contains the full path to the top level directory of your build tree
- PROJECT_SOURCE_DIR
- contains the full path to the root of your project source directory, i.e. to the nearest directory where
Environment Variables
These are environment variables which effect cmake behaviour.
- CMAKE_INCLUDE_PATH
- This is used when searching for include files e.g. using the FIND_PATH() command. If you have headers in non-standard locations, it may be useful to set this variable to this directory (e.g. /sw/include on Mac OS X). If you need several directories, separate them by the platform specific separators (e.g. ":" on UNIX)
- CMAKE_LIBRARY_PATH
- This is used when searching for libraries e.g. using the FIND_LIBRARY() command. If you have libraries in non-standard locations, it may be useful to set this variable to this directory (e.g. /sw/lib on Mac OS X). If you need several directories, separate them by the platform specific separators (e.g. ":" on UNIX)
- CMAKE_INSTALL_ALWAYS
- If set during installation CMake will install all files whether they have changed or not. The default when this is not set is to install only files that have changed since the previous installation. In both cases all files are reported to indicate CMake knows they are up to date in the installed location.
- $ENV{name}
- This is not an environment variable , but this is how you can access environment variables from cmake files. It returns the content of the environment variable with the given name (e.g. $ENV{PROGRAMFILES})
System Information
- CMAKE_MAJOR_VERSION
- major version number for CMake, e.g. the "2" in CMake 2.4.3
- CMAKE_MINOR_VERSION
- minor version number for CMake, e.g. the "4" in CMake 2.4.3
- CMAKE_PATCH_VERSION
- patch version number for CMake, e.g. the "3" in CMake 2.4.3
- CMAKE_SYSTEM
- the complete system name, e.g. "Linux-2.4.22", "FreeBSD-5.4-RELEASE" or "Windows 5.1"
- CMAKE_SYSTEM_NAME
- the short system name, e.g. "Linux", "FreeBSD" or "Windows"
- CMAKE_SYSTEM_VERSION
- only the version part of CMAKE_SYSTEM
- CMAKE_SYSTEM_PROCESSOR
- the processor name (e.g. "Intel(R) Pentium(R) M processor 2.00GHz")
- UNIX
- is TRUE on all UNIX-like OS's, including Apple OS X and CygWin
- WIN32
- is TRUE on Windows, including CygWin
- APPLE
- is TRUE on Apple OS X
- MINGW
- is TRUE when using the MinGW compiler in Windows
- MSYS
- is TRUE when using the MSYS developer environment in Windows
- CYGWIN
- is TRUE on Windows when using the CygWin version of cmake
- BORLAND
- is TRUE on Windows when using a Borland compiler
- WATCOM
- is TRUE on Windows when using the Open Watcom compiler
- MSVC, MSVC_IDE, MSVC60, MSVC70, MSVC71, MSVC80, CMAKE_COMPILER_2005
- Microsoft compiler
Various Options
- CMAKE_SKIP_RULE_DEPENDENCY
- set this to true if you don't want to rebuild the object files if the rules have changed, but not the actual source files or headers (e.g. if you changed the some compiler switches)
- CMAKE_SKIP_INSTALL_ALL_DEPENDENCY
- since CMake 2.1 the install rule depends on all, i.e. everything will be built before installing. If you don't like this, set this one to true.
- CMAKE_SKIP_RPATH
- If set, runtime paths are not added when using shared libraries. Default it is set to OFF.
- CMAKE_VERBOSE_MAKEFILE
- set this to true if you are using makefiles and want to see the full compile and link commands instead of only the shortened ones
- CMAKE_SUPPRESS_REGENERATION
- this will cause CMake to not put in the rules that re-run CMake. This might be useful if you want to use the generated build files on another machine.
- CMAKE_COLOR_MAKEFILE
- create Makefiles with colored output
- CMAKE_INCLUDE_CURRENT_DIR
- automatically add CMAKE_CURRENT_SOURCE_DIR and CMAKE_CURRENT_BINARY_DIR to the include directories in every directory
- CMAKE_INCLUDE_DIRECTORIES_PROJECT_BEFORE
- order the include directories so that directories which are in the source or build tree always come before directories outside the project
- CMAKE_SKIP_PREPROCESSED_SOURCE_RULES
- (since 2.4.4) if set to TRUE, the generated Makefiles will not contain rules for creating preprocessed files (foo.i)
- CMAKE_SKIP_ASSEMBLY_SOURCE_RULES
- (since 2.4.4) if set to TRUE, the generated Makefiles will not contain rules for creating compiled, but not yet assembled files (foo.s)
Compilers and Tools
- BUILD_SHARED_LIBS
- if this is set to ON, then all libraries are built as shared libraries by default.
SET(BUILD_SHARED_LIBS ON)
- CMAKE_AR
- tool for creating libraries. See also CMAKE_RANLIB, as "ar" and "ranlib" are typically used together.
- CMAKE_BUILD_TYPE
- Choose the type of build. CMake has default flags for these:
- None (CMAKE_C_FLAGS or CMAKE_CXX_FLAGS used)
- Debug (CMAKE_C_FLAGS_DEBUG or CMAKE_CXX_FLAGS_DEBUG)
- Release (CMAKE_C_FLAGS_RELEASE or CMAKE_CXX_FLAGS_RELEASE)
- RelWithDebInfo (CMAKE_C_FLAGS_RELWITHDEBINFO or CMAKE_CXX_FLAGS_RELWITHDEBINFO
- MinSizeRel (CMAKE_C_FLAGS_MINSIZEREL or CMAKE_CXX_FLAGS_MINSIZEREL)
Example: SET(CMAKE_BUILD_TYPE Debug)
You can create your own build type like this:
SET(CMAKE_BUILD_TYPE distribution)
SET(CMAKE_CXX_FLAGS_DISTRIBUTION "-O3")
SET(CMAKE_C_FLAGS_DISTRIBUTION "-O3")
- CMAKE_C_COMPILER
- the compiler used for C files. Normally it is detected and set during the CMake run, but you can override it at configuration time. Note! It can not be changed after the first cmake or ccmake run. Although the gui allows to enter an alternative, it will be ignored in the next 'configure' run. Use for example:
CC=gcc-3.3 CXX=g++-3.3 cmake
to set the compiler. Any other way (like writing make CC=gcc-3.3 CXX=g++-3.3) will not work. When using distcc or similar tools, you need to write:
CC="distcc gcc-3.3" CXX="distcc g++-3.3" cmake
- CMAKE_C_FLAGS
- the compiler flags for compiling C sources. Note you can also specify switches with ADD_DEFINITIONS().
- CMAKE_C_OUTPUT_EXTENSION
- what C object files end in. Typically .o or .obj.
- CMAKE_COMPILER_IS_GNUCC
- if the compiler is a variant of gcc, this should be set to 1
- CMAKE_COMPILER_IS_GNUCXX
- if the compiler is a variant of g++, this should be set to 1
- CMAKE_CXX_COMPILER
- the compiler used for C++ files. Normally it is detected and set during the CMake run, but you can override it at configuration time. Note! It can not be changed after the first cmake or ccmake run. See CMAKE_C_COMPILER above.
- CMAKE_CXX_FLAGS
- the compiler flags for compiling C++ sources. Note you can also specify switches with ADD_DEFINITIONS().
- CMAKE_CXX_OUTPUT_EXTENSION
- what C++ object files end in. Typically .o or .obj.
- CMAKE_RANLIB
- tool for creating libraries. See also CMAKE_AR, as "ar" and "ranlib" are typically used together.
Build rules
Build rules are defined in CMakeCInformation.cmake and CMakeCXXInformation.cmake.
Rules for C++ sources:
- CMAKE_CXX_CREATE_SHARED_LIBRARY
- CMAKE_CXX_CREATE_SHARED_MODULE
- CMAKE_CXX_CREATE_STATIC_LIBRARY
- CMAKE_CXX_COMPILE_OBJECT
- CMAKE_CXX_LINK_EXECUTABLE
and the equivalents for C sources:
- CMAKE_C_CREATE_SHARED_LIBRARY
- CMAKE_C_CREATE_SHARED_MODULE
- CMAKE_C_CREATE_STATIC_LIBRARY
- CMAKE_C_COMPILE_OBJECT
- CMAKE_C_LINK_EXECUTABLE
You can override the variables manually, e.g. replacing some flags in the linker command, but you can't change the value of the variables in sharp braces. Usually you don't have to change these rules, only in rare cases. You should only do this if you know what you are doing and there is no other way.
Variables not listed here
CMake has many more variables than are listed above. Documenting all of them is an ongoing project. We need everyone's help with this. If you know of a CMake variable that is not listed here, please edit the wiki and add it. Don't worry about whether you have a precise description for it. This is a wiki, and other people can provide a better description as time goes on.
How does one find out about additional variables? The CMake mailing list is probably the best resource. Some things can be learned from inspecting the CMake source code. Many - but not all of them - are also listed by this Dashboard script for extracting variables. The output of this script is rather raw, but it is a good starting point for finding more variables.
When a CMake dashboard is run, a "SystemInformation test" is usually run as well. Among other things, it lists the names and values of all of the CMake variables that are in use when the test is run. The script looks at the SystemInformation test output, and uses regular expressions to find the start and end of the "AllVariables.txt" section. It prints the results out in the form of XML.
Logging code
This code may be placed in a CMakelists.txt file to create status messages that log a number of the variables documented above. It is not a complete list, however. The variables are not auto-generated from the wiki, it is just sample code. Add whatever variables you are interested in.
