MesonPackage

Much like Autotools and CMake, Meson is a build system. But it is meant to be both fast and as user friendly as possible. GNOME’s goal is to port modules to use the Meson build system.

Phases

The MesonPackage base class comes with the following phases:

  1. meson - generate ninja files
  2. build - build the project
  3. install - install the project

By default, these phases run:

$ mkdir spack-build
$ cd spack-build
$ meson .. --prefix=/path/to/installation/prefix
$ ninja
$ ninja test  # optional
$ ninja install

Any of these phases can be overridden in your package as necessary. There is also a check method that looks for a test target in the build file. If a test target exists and the user runs:

$ spack install --test=root <meson-package>

Spack will run ninja test after the build phase.

Important files

Packages that use the Meson build system can be identified by the presence of a meson.build file. This file declares things like build instructions and dependencies.

One thing to look for is the meson_version key that gets passed to the project function:

project('gtk+', 'c',
     version: '3.94.0',
     default_options: [
       'buildtype=debugoptimized',
       'warning_level=1',
       # We only need c99, but glib needs GNU-specific features
       # https://github.com/mesonbuild/meson/issues/2289
       'c_std=gnu99',
     ],
     meson_version: '>= 0.43.0',
     license: 'LGPLv2.1+')

This means that Meson 0.43.0 is the earliest release that will work. You should specify this in a depends_on statement.

Build system dependencies

At the bare minimum, packages that use the Meson build system need meson and `ninja` dependencies. Since this is always the case, the MesonPackage base class already contains:

depends_on('meson', type='build')
depends_on('ninja', type='build')

If you need to specify a particular version requirement, you can override this in your package:

depends_on('meson@0.43.0:', type='build')
depends_on('ninja', type='build')

Finding meson flags

To get a list of valid flags that can be passed to meson, run the following command in the directory that contains meson.build:

$ meson setup --help

Passing arguments to meson

If you need to pass any arguments to the meson call, you can override the meson_args method like so:

def meson_args(self):
    return ['--default-library=both']

This method can be used to pass flags as well as variables.

External documentation

For more information on the Meson build system, see: https://mesonbuild.com/index.html