conan.tools.meson

MesonToolchain

Warning

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

Available since: 1.33.0

The MesonToolchain can be used in the generate() method:

from conans import ConanFile
from conan.tools.meson import MesonToolchain

class App(ConanFile):
    settings = "os", "arch", "compiler", "build_type"
    requires = "hello/0.1"
    options = {"shared": [True, False]}
    default_options = {"shared": False}

    def generate(self):
        tc = MesonToolchain(self)
        tc.preprocessor_definitions["MYDEFINE"] = "MYDEF_VALUE"
        tc.generate()

The MesonToolchain will generate the following file during conan install command (or before calling the build() method when the package is being built in the cache): conan_meson_native.ini, if doing a native build, or conan_meson_cross.ini, if doing a cross-build (tools.cross_building()).

conan_meson_native.ini will contain the definitions of all the Meson properties related to the Conan options and settings for the current package, platform, etc. This includes but is not limited to the following:

• Detection of default_library from Conan settings

  • Based on existance/value of a option named shared

• Detection of buildtype from Conan settings

• Definition of the C++ standard as necessary

• The Visual Studio runtime (b_vscrt), obtained from Conan input settings

conan_meson_cross.ini contains the same information as conan_meson_native.ini, but with additional information to describe host, target, and build machines (such as the processor architecture).

Check out the meson documentation for more details on native and cross files:

• Machine files

• Native environments

• Cross compilation

constructor

def __init__(self, conanfile, env=os.environ):

Most of the arguments are optional and will be deduced from the current settings, and not necessary to define them.

• conanfile: the current recipe object. Always use self.

• env: the dictionary of the environment variables.

definitions

This attribute allows defining Meson project options:

def generate(self):
    tc = MesonToolchain(self)
    tc.definitions["MYVAR"] = "MyValue"
    tc.generate()

• One project options definition for MYVAR in conan_meson_native.init or conan_meson_cross.ini file.

preprocessor_definitions

This attribute allows defining compiler preprocessor definitions, for multiple configurations (Debug, Release, etc).

def generate(self):
    tc = MesonToolchain(self)
    tc.preprocessor_definitions["MYDEF"] = "MyValue"
    tc.generate()

This will be translated to:

• One preprocessor definition for MYDEF in conan_meson_native.init or conan_meson_cross.ini file.

Generators

The MesonToolchain only works with the pkg_config generator. Please, do not use other generators, as they can have overlapping definitions that can conflict.

Using the toolchain in developer flow

One of the advantages of using Conan toolchains is that they can help to achieve the exact same build with local development flows, than when the package is created in the cache.

With the MesonToolchain it is possible to do:

# Lets start in the folder containing the conanfile.py
$ mkdir build && cd build
# Install both debug and release deps and create the toolchain
$ conan install ..
# the build type Release is encoded in the toolchain already.
# This conan_meson_native.iniis specific for release
$ meson setup --native-file conan_meson_native.ini build .
$ meson compile -C build

Meson

The Meson() build helper that works with the MesonToolchain is also experimental, and subject to breaking change in the future. It will evolve to adapt and complement the toolchain functionality.

The helper is intended to be used in the build() method, to call Meson commands automatically when a package is being built directly by Conan (create, install)

from conan.tools.meson import Meson

def build(self):
    meson = Meson(self)
    meson.configure(source_folder="src")
    meson.build()

It supports the following methods:

constructor

def __init__(self, conanfile, build_folder='build'):

• conanfile: the current recipe object. Always use self.

• build_folder: Relative path to a folder to contain the temporary build files

configure()

def configure(self, source_folder=None):

Calls meson, with the given generator and passing either --native-file conan_meson_native.ini (native builds) or --cross-file conan_meson_cross.ini (cross builds).

• source_folder: Relative path to the folder containing the root meson.build

build()

def build(self, target=None):

Calls the build system. Equivalent to meson compile -C . in the build folder.

Parameters:

• target (Optional, Defaulted to None): Specifies the target to execute. The default all target will be built if None is specified.

install()

def install(self):

Installs development files (headers, libraries, etc.). Equivalent to run meson install -C . in the build folder.

test()

def test(self):

Runs project’s tests. Equivalent to running meson test -v -C . in the build folder..

conf

• tools.ninja:jobs argument for the --jobs parameter when running Ninja. (overrides the general tools.build:processes).