# The Mesa 3D Graphics Library

# Compilation and Installation using Meson

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

## 1. Basic Usage

The Meson build system is generally considered stable and ready for production

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

Mesa requires Meson >= 0.45.0 to build. Some older versions of meson do not check that they are too old and will error out in odd ways.

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" for examples.

        meson build/

To see a description of your options you can run `meson configure` along with a build directory to view the selected options for. This will show your meson global arguments and project arguments, along with their defaults and your local settings.

Meson does not currently support listing options before configure a build directory, but this feature is being discussed upstream. For now, the only way to see what options exist is to look at the `meson_options.txt` file at the root of the project.

        meson configure build/

With additional arguments `meson configure` is used to change options on already configured build directory. All options passed to this command are in the form `-D "command"="value"`.

        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. With ninja, the -C option can be be used to point at a directory to build.

        ninja -C build/

Without arguments, it will produce libGL.so and/or several other libraries depending on the options you have chosen. Later, if you want to rebuild for a different configuration, you should run `ninja clean` before changing the configuration, or create a new out of tree build directory for each configuration you want to build as recommended in the documentation

Autotools automatically updates translation files as part of the build process, meson does not do this. Instead if you want translated drirc files you will need to invoke non-default targets for ninja to update them: `ninja -C build/ xmlpool-pot xmlpool-update-po xmlpool-gmo`

`Environment Variables`

  Meson supports the standard CC and CXX environment variables for changing the default compiler. Meson does support CFLAGS, CXXFLAGS, etc. 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` instead. Among the benefits of these options is that they are guaranteed to persist across rebuilds and reconfigurations. Meson does not allow changing compiler in a configured builddir, you will need to create a new build dir for a different compiler.

          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.

  Meson also honors `DESTDIR` for installs

`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

  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.

  For older versions of meson `$PATH` (or `%PATH%` on windows) will be searched for llvm-config (and llvm-config$version and llvm-config-$version), you can override this environment variable to control the search: `PATH=/path/with/llvm-config:$PATH meson build`.

`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.

## 2. 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'