The Mesa 3D Graphics Library

# Compilation and Installation Using Meson

- Introduction
- Basic Usage
- Advanced Usage
- Cross-compilation and 32-bit builds

## 1. Introduction

For general information about Meson see the Meson website.

Mesa's Meson build system is generally considered stable and ready for production.

The Meson build of Mesa is tested on Linux, macOS, Cygwin and Haiku, FreeBSD, DragonflyBSD, NetBSD, and should work on OpenBSD.

If Meson is not already installed on your system, you can typically install it with your package installer. For example:

    sudo apt-get install meson   # Ubuntu

or

    sudo dnf install meson   # Fedora

Mesa requires Meson >= 0.46.0 to build. Some older versions of meson do not check that they are too old and will error out in odd ways.

You'll also need Ninja. If it's not already installed, use apt-get or dnf to install the ninja-build package.

## 2. Basic Usage

The meson program is used to configure the source directory and generates either a ninja build file or Visual Studio® build files. The latter must be enabled via the `--backend` switch, as ninja is the default backend on all operating systems.

Meson only supports out-of-tree builds, and must be passed a directory to put built and generated sources into. We'll call that directory "build" here. It's recommended to create a separate build directory for each configuration you might want to use.

Basic configuration is done with:

    meson build/

This will create the build directory. If any dependencies are missing, you can install them, or try to remove the dependency with a Meson configuration option (see below).

To review the options which Meson chose, run:

    meson configure build/

Meson does not currently support listing configuration options before running "meson build/" but this feature is being discussed upstream. For now, we have a `bin/meson-options.py` script that prints the options for you. If that script doesn't work for some reason, you can always look in the meson_options.txt file at the root of the project.

With additional arguments `meson configure` can be used to change options for a previously configured build directory. All options passed to this command are in the form `-D "option"="value"`. For example:

    meson configure build/ -Dprefix=/tmp/install -Dglx=true

Note that options taking lists (such as `platforms`) are a bit more complicated, but the simplest form compatible with Mesa options is to use a comma to separate values (`-D platforms=drm,wayland`) and brackets to represent an empty list (`-D platforms=[]`).

Once you've run the initial `meson` command successfully you can use your configured backend to build the project in your build directory:

    ninja -C build/

The next step is to install the Mesa libraries, drivers, etc. This also finishes up some final steps of the build process (such as creating symbolic links for drivers). To install:

    ninja -C build/ install

Note: autotools automatically updated translation files (used by the DRI configuration tool) as part of the build process, Meson does not do this. Instead, you will need do this:

    ninja -C build/ xmlpool-pot xmlpool-update-po xmlpool-gmo

## 3. Advanced Usage

Installation Location

  Meson default to installing libGL.so in your system's main lib/ directory and DRI drivers to a dri/ subdirectory.

  Developers will often want to install Mesa to a testing directory rather than the system library directory. This can be done with the --prefix option. For example:

      meson --prefix="${PWD}/build/install" build/

  will put the final libraries and drivers into the build/install/ directory. Then you can set LD_LIBRARY_PATH and LIBGL_DRIVERS_PATH to that location to run/test the driver.

  Meson also honors `DESTDIR` for installs.

Compiler Options

  Meson supports the common CFLAGS, CXXFLAGS, etc. environment variables but their use is discouraged because of the many caveats in using them.

  Instead, it is recomended to use `-D${lang}_args` and `-D${lang}_link_args`. Among the benefits of these options is that they are guaranteed to persist across rebuilds and reconfigurations.

  This example sets -fmax-errors for compiling C sources and -DMAGIC=123 for C++ sources:

      meson builddir/ -Dc_args=-fmax-errors=10 -Dcpp_args=-DMAGIC=123

Compiler Specification

  Meson supports the standard CC and CXX environment variables for changing the default compiler. Note that Meson does not allow changing the compilers in a configured builddir so you will need to create a new build dir for a different compiler.

  This is an example of specifying the clang compilers and cleaning the build directory before reconfiguring with an extra C option:

      CC=clang CXX=clang++ meson build-clang
      ninja -C build-clang
      ninja -C build-clang clean
      meson configure build -Dc_args="-Wno-typedef-redefinition"
      ninja -C build-clang

  The default compilers depends on your operating system. Meson supports most of the popular compilers, a complete list is available here.

LLVM

  Meson includes upstream logic to wrap llvm-config using its standard dependency interface.

  As of meson 0.49.0 meson also has the concept of a "native file", these files provide information about the native build environment (as opposed to a cross build environment). They are ini formatted and can override where to find llvm-config:

  custom-llvm.ini

          [binaries]
          llvm-config = '/usr/local/bin/llvm/llvm-config'

  Then configure meson:

          meson builddir/ --native-file custom-llvm.ini

  Meson < 0.49 doesn't support native files, so to specify a custom `llvm-config` you need to modify your `$PATH` (or `%PATH%` on windows), which will be searched for `llvm-config`, `llvm-config$version`, and `llvm-config-$version`:

      PATH=/path/to/folder/with/llvm-config:$PATH meson build

  For selecting llvm-config for cross compiling a "cross file" should be used. It uses the same format as the native file above:

  cross-llvm.ini

          [binaries]
          ...
          llvm-config = '/usr/lib/llvm-config-32'

  Then configure meson:

          meson builddir/ --cross-file cross-llvm.ini

  See the Cross Compilation section for more information.
`PKG_CONFIG_PATH`

  The `pkg-config` utility is a hard requirement for configuring and building Mesa on Unix-like systems. It is used to search for external libraries on the system. This environment variable is used to control the search path for `pkg-config`. For instance, setting `PKG_CONFIG_PATH=/usr/X11R6/lib/pkgconfig` will search for package metadata in `/usr/X11R6` before the standard directories.

One of the oddities of meson is that some options are different when passed to the `meson` than to `meson configure`. These options are passed as --option=foo to `meson`, but -Doption=foo to `meson configure`. Mesa defined options are always passed as -Doption=foo.

For those coming from autotools be aware of the following:

`--buildtype/-Dbuildtype`

  This option will set the compiler debug/optimisation levels to aid debugging the Mesa libraries.

  Note that in meson this defaults to `debugoptimized`, and not setting it to `release` will yield non-optimal performance and binary size. Not using `debug` may interfere with debugging as some code and validation will be optimized away.

  For those wishing to pass their own optimization flags, use the `plain` buildtype, which causes meson to inject no additional compiler arguments, only those in the C/CXXFLAGS and those that mesa itself defines.

`-Db_ndebug`

  This option controls assertions in meson projects. When set to `false` (the default) assertions are enabled, when set to true they are disabled. This is unrelated to the `buildtype`; setting the latter to `release` will not turn off assertions.

## 4. Cross-compilation and 32-bit builds

Meson supports cross-compilation by specifying a number of binary paths and settings in a file and passing this file to `meson` or `meson configure` with the `--cross-file` parameter.

This file can live at any location, but you can use the bare filename (without the folder path) if you put it in $XDG_DATA_HOME/meson/cross or ~/.local/share/meson/cross

Below are a few example of cross files, but keep in mind that you will likely have to alter them for your system.

Those running on ArchLinux can use the AUR-maintained packages for some of those, as they'll have the right values for your system:

- meson-cross-x86-linux-gnu
- meson-cross-aarch64-linux-gnu

32-bit build on x86 linux:

    [binaries]
    c = '/usr/bin/gcc'
    cpp = '/usr/bin/g++'
    ar = '/usr/bin/gcc-ar'
    strip = '/usr/bin/strip'
    pkgconfig = '/usr/bin/pkg-config-32'
    llvm-config = '/usr/bin/llvm-config32'

    [properties]
    c_args = ['-m32']
    c_link_args = ['-m32']
    cpp_args = ['-m32']
    cpp_link_args = ['-m32']

    [host_machine]
    system = 'linux'
    cpu_family = 'x86'
    cpu = 'i686'
    endian = 'little'

64-bit build on ARM linux:

    [binaries]
    c = '/usr/bin/aarch64-linux-gnu-gcc'
    cpp = '/usr/bin/aarch64-linux-gnu-g++'
    ar = '/usr/bin/aarch64-linux-gnu-gcc-ar'
    strip = '/usr/bin/aarch64-linux-gnu-strip'
    pkgconfig = '/usr/bin/aarch64-linux-gnu-pkg-config'
    exe_wrapper = '/usr/bin/qemu-aarch64-static'

    [host_machine]
    system = 'linux'
    cpu_family = 'aarch64'
    cpu = 'aarch64'
    endian = 'little'

64-bit build on x86 windows:

    [binaries]
    c = '/usr/bin/x86_64-w64-mingw32-gcc'
    cpp = '/usr/bin/x86_64-w64-mingw32-g++'
    ar = '/usr/bin/x86_64-w64-mingw32-ar'
    strip = '/usr/bin/x86_64-w64-mingw32-strip'
    pkgconfig = '/usr/bin/x86_64-w64-mingw32-pkg-config'
    exe_wrapper = 'wine'

    [host_machine]
    system = 'windows'
    cpu_family = 'x86_64'
    cpu = 'i686'
    endian = 'little'