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  <h1>The Mesa 3D Graphics Library</h1>
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<h1>Compilation and Installation using Meson</h1>

<ul>
  <li><a href="#intro">Introduction</a></li>
  <li><a href="#basic">Basic Usage</a></li>
  <li><a href="#advanced">Advanced Usage</a></li>
  <li><a href="#cross-compilation">Cross-compilation and 32-bit builds</a></li>
</ul>

<h2 id="intro">1. Introduction</h2>

<p>For general information about Meson see the
<a href="http://mesonbuild.com/">Meson website</a>.</p>

<p><strong>Mesa's Meson build system is generally considered stable and ready
for production.</strong></p>

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

<p>If Meson is not already installed on your system, you can typically
install it with your package installer.  For example:</p>
<pre>
sudo apt-get install meson   # Ubuntu
</pre>
or
<pre>
sudo dnf install meson   # Fedora
</pre>

<p><strong>Mesa requires Meson &gt;= 0.45.0 to build.</strong>

Some older versions of meson do not check that they are too old and will error
out in odd ways.
</p>

<p>You'll also need <a href="https://ninja-build.org/">Ninja</a>.
If it's not already installed, use apt-get or dnf to install
the <em>ninja-build</em> package.
</p>

<h2 id="basic">2. Basic Usage</h2>

<p>
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 <code>--backend</code> switch, as ninja is the default
backend on all
operating systems.
</p>

<p>
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
<a href="http://mesonbuild.com/Using-multiple-build-directories.html">
separate build directory</a> for each configuration you might want to use.
</p>


<p>Basic configuration is done with:</p>

<pre>
meson build/
</pre>

<p>
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).
</p>

<p>
To review the options which Meson chose, run:
</p>
<pre>
meson configure build/
</pre>

<p>
Meson does not currently support listing configuration options before
running "meson build/" but this feature is being discussed upstream.
For now, we have a <code>bin/meson-options.py</code> script that prints
the options for you.
If that script doesn't work for some reason, you can always look in the
<a href="https://gitlab.freedesktop.org/mesa/mesa/blob/master/meson_options.txt">
meson_options.txt</a> file at the root of the project.
</p>

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

<pre>
meson configure build/ -Dprefix=/tmp/install -Dglx=true
</pre>

<p>
Note that options taking lists (such as <code>platforms</code>) are
<a href="http://mesonbuild.com/Build-options.html#using-build-options">a bit
more complicated</a>, but the simplest form compatible with Mesa options
is to use a comma to separate values (<code>-D platforms=drm,wayland</code>)
and brackets to represent an empty list (<code>-D platforms=[]</code>).
</p>

<p>
Once you've run the initial <code>meson</code> command successfully you can use
your configured backend to build the project in your build directory:
</p>

<pre>
ninja -C build/
</pre>

<p>
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:
</p>

<pre>
ninja -C build/ install
</pre>

<p>
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:
</p>
<pre>
ninja -C build/ xmlpool-pot xmlpool-update-po xmlpool-gmo
</pre>

<h2 id="advanced">3. Advanced Usage</h2>

<dl>

<dt>Installation Location</dt>
<dd>
<p>
Meson default to installing libGL.so in your system's main lib/ directory
and DRI drivers to a dri/ subdirectory.
</p>
<p>
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:
</p>
<pre>
meson --prefix="${PWD}/build/install" build/
</pre>
<p>
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.
</p>
<p>
Meson also honors <code>DESTDIR</code> for installs.
</p>
</dd>

<dt>Compiler Options</dt>
<dd>
<p>Meson supports the common CFLAGS, CXXFLAGS, etc. environment
variables but their use is discouraged because of the many caveats
in using them.
</p>
<p>Instead, it is recomended to use <code>-D${lang}_args</code> and
<code>-D${lang}_link_args</code>. Among the benefits of these options
is that they are guaranteed to persist across rebuilds and reconfigurations.
</p>
<p>
This example sets -fmax-errors for compiling C sources and -DMAGIC=123
for C++ sources:
</p>
<pre>
meson builddir/ -Dc_args=-fmax-errors=10 -Dcpp_args=-DMAGIC=123
</pre>
</dd>


<dt>Compiler Specification</dt>
<dd>
<p>
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.
</p>
<p>
This is an example of specifying the clang compilers and cleaning
the build directory before reconfiguring with an extra C option:
</p>
<pre>
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
</pre>
<p>
The default compilers depends on your operating system. Meson supports most of
the popular compilers, a complete list is available
<a href="http://mesonbuild.com/Reference-tables.html#compiler-ids">here</a>.
</p>
</dd>

<dt>LLVM</dt>
<dd><p>Meson includes upstream logic to wrap llvm-config using its standard
dependency interface.
</p></dd>

<dd><p>
As of meson 0.49.0 meson also has the concept of a
<a href="https://mesonbuild.com/Native-environments.html">"native file"</a>,
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:
</p>

custom-llvm.ini
<pre>
    [binaries]
    llvm-config = '/usr/local/bin/llvm/llvm-config'
</pre>

Then configure meson:

<pre>
    meson builddir/ --native-file custom-llvm.ini
</pre>
</dd>

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

<p>cross-llvm.ini</p>
<pre>
    [binaries]
    ...
    llvm-config = '/usr/lib/llvm-config-32'
</pre>

<p>Then configure meson:</p>
<pre>
    meson builddir/ --cross-file cross-llvm.ini
</pre>

See the <a href="#cross-compilation">Cross Compilation</a> section for more information.
</dd>

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

<dt><code>PKG_CONFIG_PATH</code></dt>
<dd><p>The
<code>pkg-config</code> 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
<code>pkg-config</code>. For instance, setting
<code>PKG_CONFIG_PATH=/usr/X11R6/lib/pkgconfig</code> will search for package
metadata in <code>/usr/X11R6</code> before the standard directories.</p>
</dd>
</dl>

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

<p>For those coming from autotools be aware of the following:</p>

<dl>
<dt><code>--buildtype/-Dbuildtype</code></dt>
<dd><p>This option will set the compiler debug/optimisation levels to aid
debugging the Mesa libraries.</p>

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

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

<dt><code>-Db_ndebug</code></dt>
<dd><p>This option controls assertions in meson projects. When set to <code>false</code>
(the default) assertions are enabled, when set to true they are disabled. This
is unrelated to the <code>buildtype</code>; setting the latter to
<code>release</code> will not turn off assertions.
</p>
</dd>
</dl>

<h2 id="cross-compilation">4. Cross-compilation and 32-bit builds</h2>

<p><a href="https://mesonbuild.com/Cross-compilation.html">Meson supports
cross-compilation</a> by specifying a number of binary paths and
settings in a file and passing this file to <code>meson</code> or
<code>meson configure</code> with the <code>--cross-file</code>
parameter.</p>

<p>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</p>

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

<p>
Those running on ArchLinux can use the AUR-maintained packages for some
of those, as they'll have the right values for your system:
</p>
<ul>
  <li><a href="https://aur.archlinux.org/packages/meson-cross-x86-linux-gnu">meson-cross-x86-linux-gnu</a></li>
  <li><a href="https://aur.archlinux.org/packages/meson-cross-aarch64-linux-gnu">meson-cross-aarch64-linux-gnu</a></li>
</ul>

<p>
32-bit build on x86 linux:
</p>
<pre>
[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'
</pre>

<p>
64-bit build on ARM linux:
</p>
<pre>
[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'
</pre>

<p>
64-bit build on x86 windows:
</p>
<pre>
[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'
</pre>

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