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)

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.j: “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().
build_type (Optional, Defaulted to None): Force the build type to be declared in CMAKE_BUILD_TYPE. If you set this parameter the build type not will be taken from the settings.
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.

Attributes

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()

command_line (read only)

Generator, conan definitions and flags that reflects the specified Conan settings.

-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.

--config Release

definitions

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

Variable	Description
CMAKE_BUILD_TYPE	Debug or Release (from self.settings.build_type)
CMAKE_OSX_ARCHITECTURES	“i386” if architecture is x86 in an OSX system
BUILD_SHARED_LIBS	Only If your conanfile has a “shared” option
CONAN_COMPILER	Conan internal variable to check compiler
CMAKE_SYSTEM_NAME	If detected cross building it’s set to self.settings.os
CMAKE_SYSTEM_VERSION	If detected cross building it’s set to the self.settings.os_version
CMAKE_ANDROID_ARCH_ABI	If detected cross building to Android
CONAN_LIBCXX	from self.settings.compiler.libcxx
CONAN_CMAKE_SYSTEM_PROCESSOR	Definition only set if same environment variable is declared by user
CONAN_CMAKE_FIND_ROOT_PATH	Definition only set if same environment variable is declared by user
CONAN_CMAKE_FIND_ROOT_PATH_MODE_PROGRAM	Definition only set if same environment variable is declared by user
CONAN_CMAKE_FIND_ROOT_PATH_MODE_LIBRARY	Definition only set if same environment variable is declared by user
CONAN_CMAKE_FIND_ROOT_PATH_MODE_INCLUDE	Definition only set if same environment variable is declared by user
CONAN_CMAKE_POSITION_INDEPENDENT_CODE	When `fPIC` option is present and True or when `fPIC` is present and False but and option `shared` is present and True
CONAN_SHARED_LINKER_FLAGS	-m32 and -m64 based on your architecture
CONAN_C_FLAGS	-m32 and -m64 based on your architecture and /MP for MSVS
CONAN_C_FLAGS	-m32 and -m64 based on your architecture and /MP for MSVS
CONAN_LINK_RUNTIME	Runtime from self.settings.compiler.runtime for MSVS
CONAN_CMAKE_CXX_STANDARD	From setting `cppstd`
CONAN_CMAKE_CXX_EXTENSIONS	From setting `cppstd`, when GNU extensions are enabled
CONAN_STD_CXX_FLAG	From setting `cppstd`. Flag for compiler directly (for CMake < 3.1)

But you can change the automatic definitions after the CMake() object creation using the definitions property:

from conans import ConanFile, CMake

class ExampleConan(ConanFile):
    ...

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

Methods

configure()

def configure(self, args=None, defs=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
definitions (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_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)

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

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()

This method changes references to the absolute path of the installed package in exported CMake config files to the appropriate Conan variable. 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.

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()

Environment variables

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