docs/meson.rst - external/github.com/Mesa3D/mesa - Git at Google

 Compilation and Installation Using Meson
 ========================================

 1. Introduction
 ---------------

 For general information about Meson see the `Meson
 website <https://mesonbuild.com/>`__.

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

 .. note::

    Mesa requires Meson >= 0.53.0 to build.

    If your distribution doesn't have something recent enough in its
    repositories, you can `try the methods suggested here
    <https://mesonbuild.com/Getting-meson.html>`__ to install the
    current version of Meson.

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

 Unix-like OSes
 ^^^^^^^^^^^^^^

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

 .. code-block:: console

    sudo apt-get install meson   # Ubuntu

 or

 .. code-block:: console

    sudo dnf install meson   # Fedora

 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 <https://ninja-build.org/>`__. If it's not
 already installed, use apt-get or dnf to install the *ninja-build*
 package.

 Windows
 ^^^^^^^

 You will need to install Python 3 and Meson as a module using pip. This
 is because we use Python for generating code, and rely on external
 modules (Mako). You also need pkg-config (a hard dependency of Meson),
 Flex, and Bison. The easiest way to install everything you need is with
 `Chocolatey <https://chocolatey.org/>`__.

 .. code-block:: console

    choco install python3 winflexbison pkgconfiglite

 You can even use Chocolatey to install MinGW and Ninja (Ninja can be
 used with MSVC as well)

 .. code-block:: console

    choco install ninja mingw

 Then install Meson using pip

 .. code-block:: console

    py -3 -m pip install meson mako

 You may need to add the Python 3 scripts directory to your path for
 Meson.

 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 <https://mesonbuild.com/Using-multiple-build-directories.html>`__
 for each configuration you might want to use.

 Basic configuration is done with:

 .. code-block:: console

    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:

 .. code-block:: console

    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 <https://gitlab.freedesktop.org/mesa/mesa/-/blob/main/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:

 .. code-block:: console

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

 Note that options taking lists (such as ``platforms``) are `a bit more
 complicated <https://mesonbuild.com/Build-options.html#using-build-options>`__,
 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:

 .. code-block:: console

    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:

 .. code-block:: console

    ninja -C build/ install

 Windows specific instructions
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

 On Windows you have a couple of choices for compilers. If you installed
 MinGW with Chocolatey and want to use Ninja you should be able to open
 any shell and follow the instructions above. If you want to you MSVC,
 clang-cl, or ICL (the Intel Compiler), read on.

 Both ICL and MSVC come with shell environments, the easiest way to use
 Meson with these it to open a shell. For clang-cl you will need to open
 an MSVC shell, and then override the compilers, either using a `native
 file <https://mesonbuild.com/Native-environments.html>`__, or with the
 CC and CXX environment variables.

 All of these compilers are tested and work with Ninja, but if you want
 Visual Studio integration or you just like msbuild, passing
 ``--backend=vs`` to Meson will generate a Visual Studio solution.

 3. Advanced Usage
 -----------------

 Installation Location
 ^^^^^^^^^^^^^^^^^^^^^

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

 .. code-block:: console

    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 recommended 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:

 .. code-block:: console

    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:

 .. code-block:: console

    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 <https://mesonbuild.com/Reference-tables.html#compiler-ids>`__.

 LLVM
 ^^^^

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

 Meson can use CMake to find LLVM. But due to the way LLVM implements its
 CMake finder it will only find static libraries, it will never find
 :file:`libllvm.so`. There is also a ``-Dcmake_module_path`` option,
 which points to the root of an alternative installation (the prefix).
 For example:

 .. code-block:: console

    meson builddir -Dcmake_module_path=/home/user/mycmake/prefix

 As of Meson 0.49.0 Meson also has the concept of a `"native
 file" <https://mesonbuild.com/Native-environments.html>`__, 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:

 .. code-block:: ini
    :caption: custom-llvm.ini

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

 Then configure Meson:

 .. code-block:: console

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

 For selecting llvm-config for cross compiling a `"cross
 file" <https://mesonbuild.com/Cross-compilation.html#defining-the-environment>`__
 should be used. It uses the same format as the native file above:

 .. code-block:: ini
    :caption: cross-llvm.ini

    [binaries]
    ...
    llvm-config = '/usr/lib/llvm-config-32'
    cmake = '/usr/bin/cmake-for-my-arch'

 Obviously, only cmake or llvm-config is required.

 Then configure Meson:

 .. code-block:: console

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

 See the :ref:`Cross Compilation <cross-compilation>` section for more
 information.

 On Windows (and in other cases), using llvm-config or CMake may be
 either undesirable or impossible. Meson's solution for this is a
 `wrap <https://mesonbuild.com/Wrap-dependency-system-manual.html>`__, in
 this case a "binary wrap". Follow the steps below:

 -  Install the binaries and headers into the
    ``$mesa_src/subprojects/llvm``
 -  Add a :file:`meson.build` file to that directory (more on that later)

 The wrap file must define the following:

 -  ``dep_llvm``: a ``declare_dependency()`` object with
    include_directories, dependencies, and version set)

 It may also define:

 -  ``irbuilder_h``: a ``files()`` object pointing to llvm/IR/IRBuilder.h
 -  ``has_rtti``: a ``bool`` that declares whether LLVM was built with
    RTTI. Defaults to true

 such a :file:`meson.build` file might look like:

 ::

    project('llvm', ['cpp'])

    cpp = meson.get_compiler('cpp')

    _deps = []
    _search = join_paths(meson.current_source_dir(), 'lib')
    foreach d : ['libLLVMCodeGen', 'libLLVMScalarOpts', 'libLLVMAnalysis',
                 'libLLVMTransformUtils', 'libLLVMCore', 'libLLVMX86CodeGen',
                 'libLLVMSelectionDAG', 'libLLVMipo', 'libLLVMAsmPrinter',
                 'libLLVMInstCombine', 'libLLVMInstrumentation', 'libLLVMMC',
                 'libLLVMGlobalISel', 'libLLVMObjectYAML', 'libLLVMDebugInfoPDB',
                 'libLLVMVectorize', 'libLLVMPasses', 'libLLVMSupport',
                 'libLLVMLTO', 'libLLVMObject', 'libLLVMDebugInfoCodeView',
                 'libLLVMDebugInfoDWARF', 'libLLVMOrcJIT', 'libLLVMProfileData',
                 'libLLVMObjCARCOpts', 'libLLVMBitReader', 'libLLVMCoroutines',
                 'libLLVMBitWriter', 'libLLVMRuntimeDyld', 'libLLVMMIRParser',
                 'libLLVMX86Desc', 'libLLVMAsmParser', 'libLLVMTableGen',
                 'libLLVMFuzzMutate', 'libLLVMLinker', 'libLLVMMCParser',
                 'libLLVMExecutionEngine', 'libLLVMCoverage', 'libLLVMInterpreter',
                 'libLLVMTarget', 'libLLVMX86AsmParser', 'libLLVMSymbolize',
                 'libLLVMDebugInfoMSF', 'libLLVMMCJIT', 'libLLVMXRay',
                 'libLLVMX86AsmPrinter', 'libLLVMX86Disassembler',
                 'libLLVMMCDisassembler', 'libLLVMOption', 'libLLVMIRReader',
                 'libLLVMLibDriver', 'libLLVMDlltoolDriver', 'libLLVMDemangle',
                 'libLLVMBinaryFormat', 'libLLVMLineEditor',
                 'libLLVMWindowsManifest', 'libLLVMX86Info', 'libLLVMX86Utils']
      _deps += cpp.find_library(d, dirs : _search)
    endforeach

    dep_llvm = declare_dependency(
      include_directories : include_directories('include'),
      dependencies : _deps,
      version : '6.0.0',
    )

    has_rtti = false
    irbuilder_h = files('include/llvm/IR/IRBuilder.h')

 It is very important that version is defined and is accurate, if it is
 not, workarounds for the wrong version of LLVM might be used resulting
 in build failures.

 ``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.

 Options
 ^^^^^^^

 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/optimization 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.

 .. _cross-compilation:

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

 `Meson supports
 cross-compilation <https://mesonbuild.com/Cross-compilation.html>`__ 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
 :file:`$XDG_DATA_HOME/meson/cross` or :file:`~/.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 <https://aur.archlinux.org/packages/meson-cross-x86-linux-gnu>`__
 -  `meson-cross-aarch64-linux-gnu <https://aur.archlinux.org/packages/meson-cross-aarch64-linux-gnu>`__

 32-bit build on x86 linux:

 .. code-block:: ini

    [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:

 .. code-block:: ini

    [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:

 .. code-block:: ini

    [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'
	Compilation and Installation Using Meson
	========================================

	1. Introduction
	---------------

	For general information about Meson see the `Meson
	website <https://mesonbuild.com/>`__.

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

	.. note::

	Mesa requires Meson >= 0.53.0 to build.

	If your distribution doesn't have something recent enough in its
	repositories, you can `try the methods suggested here
	<https://mesonbuild.com/Getting-meson.html>`__ to install the
	current version of Meson.

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

	Unix-like OSes
	^^^^^^^^^^^^^^

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

	.. code-block:: console

	sudo apt-get install meson # Ubuntu

	or

	.. code-block:: console

	sudo dnf install meson # Fedora

	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 <https://ninja-build.org/>`__. If it's not
	already installed, use apt-get or dnf to install the ninja-build
	package.

	Windows
	^^^^^^^

	You will need to install Python 3 and Meson as a module using pip. This
	is because we use Python for generating code, and rely on external
	modules (Mako). You also need pkg-config (a hard dependency of Meson),
	Flex, and Bison. The easiest way to install everything you need is with
	`Chocolatey <https://chocolatey.org/>`__.

	.. code-block:: console

	choco install python3 winflexbison pkgconfiglite

	You can even use Chocolatey to install MinGW and Ninja (Ninja can be
	used with MSVC as well)

	.. code-block:: console

	choco install ninja mingw

	Then install Meson using pip

	.. code-block:: console

	py -3 -m pip install meson mako

	You may need to add the Python 3 scripts directory to your path for
	Meson.

	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 <https://mesonbuild.com/Using-multiple-build-directories.html>`__
	for each configuration you might want to use.

	Basic configuration is done with:

	.. code-block:: console

	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:

	.. code-block:: console

	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 <https://gitlab.freedesktop.org/mesa/mesa/-/blob/main/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:

	.. code-block:: console

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

	Note that options taking lists (such as ``platforms``) are `a bit more
	complicated <https://mesonbuild.com/Build-options.html#using-build-options>`__,
	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:

	.. code-block:: console

	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:

	.. code-block:: console

	ninja -C build/ install

	Windows specific instructions
	^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

	On Windows you have a couple of choices for compilers. If you installed
	MinGW with Chocolatey and want to use Ninja you should be able to open
	any shell and follow the instructions above. If you want to you MSVC,
	clang-cl, or ICL (the Intel Compiler), read on.

	Both ICL and MSVC come with shell environments, the easiest way to use
	Meson with these it to open a shell. For clang-cl you will need to open
	an MSVC shell, and then override the compilers, either using a `native
	file <https://mesonbuild.com/Native-environments.html>`__, or with the
	CC and CXX environment variables.

	All of these compilers are tested and work with Ninja, but if you want
	Visual Studio integration or you just like msbuild, passing
	``--backend=vs`` to Meson will generate a Visual Studio solution.

	3. Advanced Usage
	-----------------

	Installation Location
	^^^^^^^^^^^^^^^^^^^^^

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

	.. code-block:: console

	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 recommended 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:

	.. code-block:: console

	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:

	.. code-block:: console

	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 <https://mesonbuild.com/Reference-tables.html#compiler-ids>`__.

	LLVM
	^^^^

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

	Meson can use CMake to find LLVM. But due to the way LLVM implements its
	CMake finder it will only find static libraries, it will never find
	:file:`libllvm.so`. There is also a ``-Dcmake_module_path`` option,
	which points to the root of an alternative installation (the prefix).
	For example:

	.. code-block:: console

	meson builddir -Dcmake_module_path=/home/user/mycmake/prefix

	As of Meson 0.49.0 Meson also has the concept of a `"native
	file" <https://mesonbuild.com/Native-environments.html>`__, 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:

	.. code-block:: ini
	:caption: custom-llvm.ini

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

	Then configure Meson:

	.. code-block:: console

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

	For selecting llvm-config for cross compiling a `"cross
	file" <https://mesonbuild.com/Cross-compilation.html#defining-the-environment>`__
	should be used. It uses the same format as the native file above:

	.. code-block:: ini
	:caption: cross-llvm.ini

	[binaries]
	...
	llvm-config = '/usr/lib/llvm-config-32'
	cmake = '/usr/bin/cmake-for-my-arch'

	Obviously, only cmake or llvm-config is required.

	Then configure Meson:

	.. code-block:: console

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

	See the :ref:`Cross Compilation <cross-compilation>` section for more
	information.

	On Windows (and in other cases), using llvm-config or CMake may be
	either undesirable or impossible. Meson's solution for this is a
	`wrap <https://mesonbuild.com/Wrap-dependency-system-manual.html>`__, in
	this case a "binary wrap". Follow the steps below:

	- Install the binaries and headers into the
	``$mesa_src/subprojects/llvm``
	- Add a :file:`meson.build` file to that directory (more on that later)

	The wrap file must define the following:

	- ``dep_llvm``: a ``declare_dependency()`` object with
	include_directories, dependencies, and version set)

	It may also define:

	- ``irbuilder_h``: a ``files()`` object pointing to llvm/IR/IRBuilder.h
	- ``has_rtti``: a ``bool`` that declares whether LLVM was built with
	RTTI. Defaults to true

	such a :file:`meson.build` file might look like:

	::

	project('llvm', ['cpp'])

	cpp = meson.get_compiler('cpp')

	_deps = []
	_search = join_paths(meson.current_source_dir(), 'lib')
	foreach d : ['libLLVMCodeGen', 'libLLVMScalarOpts', 'libLLVMAnalysis',
	'libLLVMTransformUtils', 'libLLVMCore', 'libLLVMX86CodeGen',
	'libLLVMSelectionDAG', 'libLLVMipo', 'libLLVMAsmPrinter',
	'libLLVMInstCombine', 'libLLVMInstrumentation', 'libLLVMMC',
	'libLLVMGlobalISel', 'libLLVMObjectYAML', 'libLLVMDebugInfoPDB',
	'libLLVMVectorize', 'libLLVMPasses', 'libLLVMSupport',
	'libLLVMLTO', 'libLLVMObject', 'libLLVMDebugInfoCodeView',
	'libLLVMDebugInfoDWARF', 'libLLVMOrcJIT', 'libLLVMProfileData',
	'libLLVMObjCARCOpts', 'libLLVMBitReader', 'libLLVMCoroutines',
	'libLLVMBitWriter', 'libLLVMRuntimeDyld', 'libLLVMMIRParser',
	'libLLVMX86Desc', 'libLLVMAsmParser', 'libLLVMTableGen',
	'libLLVMFuzzMutate', 'libLLVMLinker', 'libLLVMMCParser',
	'libLLVMExecutionEngine', 'libLLVMCoverage', 'libLLVMInterpreter',
	'libLLVMTarget', 'libLLVMX86AsmParser', 'libLLVMSymbolize',
	'libLLVMDebugInfoMSF', 'libLLVMMCJIT', 'libLLVMXRay',
	'libLLVMX86AsmPrinter', 'libLLVMX86Disassembler',
	'libLLVMMCDisassembler', 'libLLVMOption', 'libLLVMIRReader',
	'libLLVMLibDriver', 'libLLVMDlltoolDriver', 'libLLVMDemangle',
	'libLLVMBinaryFormat', 'libLLVMLineEditor',
	'libLLVMWindowsManifest', 'libLLVMX86Info', 'libLLVMX86Utils']
	_deps += cpp.find_library(d, dirs : _search)
	endforeach

	dep_llvm = declare_dependency(
	include_directories : include_directories('include'),
	dependencies : _deps,
	version : '6.0.0',
	)

	has_rtti = false
	irbuilder_h = files('include/llvm/IR/IRBuilder.h')

	It is very important that version is defined and is accurate, if it is
	not, workarounds for the wrong version of LLVM might be used resulting
	in build failures.

	``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.

	Options
	^^^^^^^

	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/optimization 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.

	.. _cross-compilation:

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

	`Meson supports
	cross-compilation <https://mesonbuild.com/Cross-compilation.html>`__ 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
	:file:`$XDG_DATA_HOME/meson/cross` or :file:`~/.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 <https://aur.archlinux.org/packages/meson-cross-x86-linux-gnu>`__
	- `meson-cross-aarch64-linux-gnu <https://aur.archlinux.org/packages/meson-cross-aarch64-linux-gnu>`__

	32-bit build on x86 linux:

	.. code-block:: ini

	[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:

	.. code-block:: ini

	[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:

	.. code-block:: ini

	[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'