CMake

The CMake class helps us to invoke cmake command with the generator, flags and definitions, reflecting the specified Conan settings.

There are two ways to invoke your cmake tools:

  • Using the helper attributes cmake.command_line and cmake.build_config:
from conans import ConanFile, CMake

 class ExampleConan(ConanFile):
     ...

     def build(self):
         cmake = CMake(self)
         self.run('cmake "%s" %s' % (self.source_folder, cmake.command_line))
         self.run('cmake --build . %s' % cmake.build_config)
         self.run('cmake --build . --target install')
  • Using the helper methods:
from conans import ConanFile, CMake

class ExampleConan(ConanFile):
    ...

    def build(self):
        cmake = CMake(self)
        # same as cmake.configure(source_folder=self.source_folder, build_folder=self.build_folder)
        cmake.configure()
        cmake.build()
        cmake.test() # Build the "RUN_TESTS" or "test" target
        # Build the "install" target, defining CMAKE_INSTALL_PREFIX to self.package_folder
        cmake.install()

Constructor

class CMake(object):

    def __init__(self, conanfile, generator=None, cmake_system_name=True,
                 parallel=True, build_type=None, toolset=None, make_program=None,
                 set_cmake_flags=False, msbuild_verbosity='minimal', cmake_program=None,
                 generator_platform=None)
Parameters:
  • conanfile (Required): Conanfile object. Usually self in a conanfile.py
  • generator (Optional, Defaulted to None): Specify a custom generator instead of autodetect it. e.g., “MinGW Makefiles”
  • cmake_system_name (Optional, Defaulted to True): Specify a custom value for CMAKE_SYSTEM_NAME instead of autodetect it.
  • parallel (Optional, Defaulted to True): If True, will append the -jN attribute for parallel building being N the cpu_count(). Also applies to parallel test execution (by defining CTEST_PARALLEL_LEVEL environment variable).
  • build_type (Optional, Defaulted to None): Force the build type instead of taking the value from the settings. Note this will also make the CMAKE_BUILD_TYPE to be declared for multi configuration generators.
  • toolset (Optional, Defaulted to None): Specify a toolset for Visual Studio.
  • make_program (Optional, Defaulted to None): Indicate path to make.
  • set_cmake_flags (Optional, Defaulted to None): Whether or not to set CMake flags like CMAKE_CXX_FLAGS, CMAKE_C_FLAGS, etc.
  • msbuild_verbosity (Optional, Defaulted to minimal): verbosity level for MSBuild (in case of Visual Studio generator). Set this parameter to None to avoid using it in the command line.
  • cmake_program (Optional, Defaulted to None): Path to the custom cmake executable.
  • generator_platform (Optional, Defaulted to None): Generator platform name or none to autodetect (-A cmake option).

Attributes

generator

Specifies a custom CMake generator to use, see also cmake-generators documentation.

generator_platform

Specifies a custom CMake generator platform to use, see also CMAKE_GENERATOR_PLATFORM documentation.

verbose

Defaulted to: False

Set it to True or False to automatically set the definition CMAKE_VERBOSE_MAKEFILE.

from conans import ConanFile, CMake

class ExampleConan(ConanFile):
    ...

    def build(self):
        cmake = CMake(self)
        cmake.verbose = True
        cmake.configure()
        cmake.build()

build_folder (Read only)

Build folder where the configure() and build() methods will be called.

build_type [Deprecated]

Build type can be forced with this variable instead of taking it from the settings.

flags (Read only)

Flag conversion of definitions to be used in the command line invocation (-D).

is_multi_configuration (Read only)

Indicates whether the generator selected allows builds with multi configuration: Release, Debug… Multi configuration generators are Visual Studio and Xcode ones.

command_line (Read only)

Arguments and flags calculated by the build helper that will be applied. It indicates the generator, the Conan definitions and the flags converted from the specified Conan settings. For example:

-G "Unix Makefiles" -DCMAKE_BUILD_TYPE=Release ... -DCONAN_C_FLAGS=-m64 -Wno-dev

build_config (Read only)

Value for --config option for Multi-configuration IDEs. This flag will only be set if the generator is_multi_configuration and build_type was not forced in constructor class.

An example of the value of this property could be:

--config Release

parallel

Defaulted to: True

Run CMake process in parallel for compilation, installation and testing. This is translated into the proper command line argument: For Unix Makefiles it is -jX and for Visual Studio it is /m:X.

However, the parallel executing can be changed for testing like this:

cmake = CMake(self)
cmake.configure()
cmake.build()  # 'parallel' is enabled by default
cmake.parallel = False
cmake.test()

In the case of cmake.test() this flag sets the CTEST_PARALLEL_LEVEL variable to the according value in tools.cpu_count().

definitions

The CMake helper will automatically append some definitions based on your settings:

Variable Description
CMAKE_BUILD_TYPE Debug, Release… from self.settings.build_type or build_type attribute only if is_multi_configuration
CMAKE_OSX_ARCHITECTURES i386 if architecture is x86 in an OSX system
BUILD_SHARED_LIBS Only if your recipe has a shared option
CONAN_COMPILER Conan internal variable to check the compiler
CMAKE_SYSTEM_NAME Set to self.settings.os value if cross-building is detected
CMAKE_SYSTEM_VERSION Set to self.settings.os_version value if cross-building is detected
CMAKE_ANDROID_ARCH_ABI Set to a suitable value if cross-building to an Android is detected
CONAN_LIBCXX Set to self.settings.compiler.libcxx value
CONAN_CMAKE_SYSTEM_PROCESSOR Definition set only if same environment variable is declared by user
CONAN_CMAKE_FIND_ROOT_PATH Definition set only if same environment variable is declared by user
CONAN_CMAKE_FIND_ROOT_PATH_MODE_PROGRAM Definition set only if same environment variable is declared by user
CONAN_CMAKE_FIND_ROOT_PATH_MODE_LIBRARY Definition set only if same environment variable is declared by user
CONAN_CMAKE_FIND_ROOT_PATH_MODE_INCLUDE Definition set only if same environment variable is declared by user
CONAN_CMAKE_POSITION_INDEPENDENT_CODE Set when fPIC option exists and True or fPIC exists and False but shared option exists and True
CONAN_SHARED_LINKER_FLAGS Set to -m32 or -m64 values based on the architecture
CONAN_C_FLAGS Set to -m32 or -m64 values based on the architecture and /MP for MSVS
CONAN_CXX_FLAGS Set to -m32 or -m64 values based on the architecture and /MP for MSVS
CONAN_LINK_RUNTIME Set to the runtime value from self.settings.compiler.runtime for MSVS
CONAN_CMAKE_CXX_STANDARD Set to the self.settings.compiler.cppstd value (or self.settings.cppstd for backward compatibility)
CONAN_CMAKE_CXX_EXTENSIONS Set to ON or OFF value when GNU extensions for the given C++ standard are enabled
CONAN_STD_CXX_FLAG Set to the flag corresponding to the C++ standard defined in self.settings.compiler.cppstd. Used for CMake < 3.1)
CMAKE_EXPORT_NO_PACKAGE_REGISTRY Defined by default to disable the package registry
CONAN_IN_LOCAL_CACHE ON if the build runs in local cache, OFF if running in a user folder
CONAN_EXPORTED Defined when CMake is called using Conan CMake helper
ANDROID_ABI Just alias for CMAKE_ANDROID_ARCH_ABI
ANDROID_NDK Defined when one of ANDROID_NDK_ROOT or ANDROID_NDK_HOME environment variables presented

There are some definitions set to be used later on the the install() step too:

Variable Description
CMAKE_INSTALL_PREFIX Set to conanfile.package_folder value.
CMAKE_INSTALL_BINDIR Set to bin inside the package folder.
CMAKE_INSTALL_SBINDIR Set to bin inside the package folder.
CMAKE_INSTALL_LIBEXECDIR Set to bin inside the package folder.
CMAKE_INSTALL_LIBDIR Set to lib inside the package folder.
CMAKE_INSTALL_INCLUDEDIR Set to include inside the package folder.
CMAKE_INSTALL_OLDINCLUDEDIR Set to include inside the package folder.
CMAKE_INSTALL_DATAROOTDIR Set to share inside the package folder.

But you can change the automatic definitions after the CMake() object creation using the definitions property or even add your own ones:

from conans import ConanFile, CMake

class ExampleConan(ConanFile):
    ...

    def build(self):
        cmake = CMake(self)
        cmake.definitions["CMAKE_SYSTEM_NAME"] = "Generic"
        cmake.definitions["MY_CUSTOM_DEFINITION"] = True
        cmake.configure()
        cmake.build()
        cmake.install()  # Build --target=install

Note that definitions changed after the configure() call will not take effect later on the build(), test() or install() ones.

Methods

configure()

def configure(self, args=None, defs=None, source_dir=None, build_dir=None,
              source_folder=None, build_folder=None, cache_build_folder=None,
              pkg_config_paths=None)

Configures CMake project with the given parameters.

Parameters:
  • args (Optional, Defaulted to None): A list of additional arguments to be passed to the cmake command. Each argument will be escaped according to the current shell. No extra arguments will be added if args=None
  • defs (Optional, Defaulted to None): A dict that will be converted to a list of CMake command line variable definitions of the form -DKEY=VALUE. Each value will be escaped according to the current shell and can be either str, bool or of numeric type
  • source_dir (Optional, Defaulted to None): [DEPRECATED] Use source_folder instead. CMake’s source directory where CMakeLists.txt is located. The default value is the build folder if None is specified (or the source folder if no_copy_source is specified). Relative paths are allowed and will be relative to build_folder.
  • build_dir (Optional, Defaulted to None): [DEPRECATED] Use build_folder instead. CMake’s output directory. The default value is the package build root folder if None is specified. The CMake object will store build_folder internally for subsequent calls to build().
  • source_folder: CMake’s source directory where CMakeLists.txt is located. The default value is the self.source_folder. Relative paths are allowed and will be relative to self.source_folder.
  • build_folder: CMake’s output directory. The default value is the self.build_folder if None is specified. The CMake object will store build_folder internally for subsequent calls to build().
  • cache_build_folder (Optional, Defaulted to None): Use the given subfolder as build folder when building the package in the local cache. This argument doesn’t have effect when the package is being built in user folder with conan build but overrides build_folder when working in the local cache. See self.in_local_cache.
  • pkg_config_paths (Optional, Defaulted to None): Specify folders (in a list) of relative paths to the install folder or absolute ones where to find *.pc files (by using the env var PKG_CONFIG_PATH). If None is specified but the conanfile is using the pkg_config generator, the self.install_folder will be added to the PKG_CONFIG_PATH in order to locate the pc files of the requirements of the conanfile.

build()

def build(self, args=None, build_dir=None, target=None)

Builds CMake project with the given parameters.

Parameters:
  • args (Optional, Defaulted to None): A list of additional arguments to be passed to the cmake command. Each argument will be escaped according to the current shell. No extra arguments will be added if args=None
  • build_dir (Optional, Defaulted to None): CMake’s output directory. If None is specified the build_dir from configure() will be used.
  • target (Optional, Defaulted to None): Specifies the target to execute. The default all target will be built if None is specified. "install" can be used to relocate files to aid packaging.

test()

def test(args=None, build_dir=None, target=None, output_on_failure=False)

Build CMake test target (could be RUN_TESTS in multi-config projects or test in single-config projects), which usually means building and running unit tests

Parameters:
  • args (Optional, Defaulted to None): A list of additional arguments to be passed to the cmake command. Each argument will be escaped according to the current shell. No extra arguments will be added if args=None.
  • build_dir (Optional, Defaulted to None): CMake’s output directory. If None is specified the build_folder from configure() will be used.
  • target (Optional, default to None). Alternative target name for running the tests. If not defined RUN_TESTS or test will be used.
  • output_on_failure (Optional, default to False). Enables ctest to show output of failed tests by defining CTEST_OUTPUT_ON_FAILURE environment variable (same effect as ctest --output-on-failure).

install()

def install(args=None, build_dir=None)

Installs CMake project with the given parameters.

Parameters:
  • args (Optional, Defaulted to None): A list of additional arguments to be passed to the cmake command. Each argument will be escaped according to the current shell. No extra arguments will be added if args=None.
  • build_dir (Optional, Defaulted to None): CMake’s output directory. If None is specified the build_folder from configure() will be used.

patch_config_paths() [EXPERIMENTAL]

def patch_config_paths()

Warning

This is an experimental feature subject to breaking changes in future releases.

This method changes references to the absolute path of the installed package in exported CMake config files to the appropriate Conan variable. Method also changes references to other packages installation paths in export CMake config files to Conan variable with their installation roots. This makes most CMake config files portable.

For example, if a package foo installs a file called fooConfig.cmake to be used by cmake’s find_package() method, normally this file will contain absolute paths to the installed package folder, for example it will contain a line such as:

SET(Foo_INSTALL_DIR /home/developer/.conan/data/Foo/1.0.0/...)

This will cause cmake’s find_package() method to fail when someone else installs the package via Conan. This function will replace such paths to:

SET(Foo_INSTALL_DIR ${CONAN_FOO_ROOT})

Which is a variable that is set by conanbuildinfo.cmake, so that find_package() now correctly works on this Conan package.

For dependent packages method replaces lines with references to dependencies installation paths such as:

SET_TARGET_PROPERTIES(foo PROPERTIES INTERFACE_INCLUDE_DIRECTORIES "/home/developer/.conan/data/Bar/1.0.0/user/channel/id/include")

to following lines:

SET_TARGET_PROPERTIES(foo PROPERTIES INTERFACE_INCLUDE_DIRECTORIES "${CONAN_BAR_ROOT}/include")

If the install() method of the CMake object in the conanfile is used, this function should be called after that invocation. For example:

def build(self):
    cmake = CMake(self)
    cmake.configure()
    cmake.build()
    cmake.install()
    cmake.patch_config_paths()

get_version()

@staticmethod
def get_version()

Returns the CMake version in a conans.model.Version object as it is evaluated by the command line. Will raise if cannot resolve it to valid version.

Environment variables

There are some environment variables that will also affect the CMake() helper class. Check them in the CMAKE RELATED VARIABLES section.

Example

The following example of conanfile.py shows you how to manage a project with conan and CMake.

from conans import ConanFile, CMake

class SomePackage(ConanFile):
    name = "SomePackage"
    version = "1.0.0"
    settings = "os", "compiler", "build_type", "arch"
    generators = "cmake"

def configure_cmake(self):
    cmake = CMake(self)

    # put definitions here so that they are re-used in cmake between
    # build() and package()
    cmake.definitions["SOME_DEFINITION_NAME"] = "On"

    cmake.configure()
    return cmake

def build(self):
    cmake = self.configure_cmake()
    cmake.build()

    # run unit tests after the build
    cmake.test()

    # run custom make command
    self.run("make -j3 check)

def package(self):
    cmake = self.configure_cmake()
    cmake.install()

Default used generators

When a compiler or its version is not detected, the CMake helper uses a default generator based on the platform operating system. For Unix systems it generates Unix Makefiles. For Windows there is no default generator, it will be detected by CMake automatically.