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<h1>The Mesa 3D Graphics Library</h1>
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<h1>Compilation and Installation using Meson</h1>
<h2 id="basic">1. Basic Usage</h2>
<p><strong>The Meson build system for Mesa is still under active development,
and should not be used in production environments.</strong></p>
<p>The meson build is currently only tested on linux, and is known to not work
on macOS, Windows, and haiku. This will be fixed.</p>
<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 --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.
</p>
<pre>
meson build/
</pre>
<p>
To see a description of your options you can run <code>meson configure</code>
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.
Moes does not currently support listing options before configure a build
directory, but this feature is being discussed upstream.
</p>
<pre>
meson configure build/
</pre>
<p>
With additional arguments <code>meson configure</code> is used to change
options on already configured build directory. All options passed to this
command are in the form -D "command"="value".
</p>
<pre>
meson configure build/ -Dprefix=/tmp/install -Dglx=true
</pre>
<p>
Once you've run the initial <code>meson</code> 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.
</p>
<pre>
ninja -C build/
</pre>
<p>
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 <code>ninja clean</code> before
changing the configuration, or create a new out of tree build directory for
each configuration you want to build.
http://mesonbuild.com/Using-multiple-build-directories.html
</p>
<dt><code>Environment Variables</code></dt>
<dd><p>Meson supports the standard CC and CXX envrionment variables for
changing the default compiler, and CFLAGS, CXXFLAGS, and LDFLAGS for setting
options to the compiler and linker.
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>.
These arguments are consumed and stored by meson when it is initialized or
re-initialized. Therefore passing them to meson configure will not do anything,
and passing them to ninja will only do something if ninja decides to
re-initialze meson, for example, if a meson.build file has been changed.
Changing these variables will not cause all targets to be rebuilt, so running
ninja clean is recomended when changing CFLAGS or CXXFLAGS. meson will never
change compiler in a configured build directory.
</p>
<pre>
CC=clang CXX=clang++ meson build-clang
ninja -C build-clang
ninja -C build-clang clean
touch meson.build
CFLAGS=-Wno-typedef-redefinition ninja -C build-clang
</pre>
<p>Meson also honors DESTDIR for installs</p>
</dd>
<dt><code>LLVM</code></dt>
<dd><p>Meson includes upstream logic to wrap llvm-config using it's standard
dependncy interface. It will search $PATH (or %PATH% on windows) for
llvm-config, so using an LLVM from a non-standard path is as easy as
<code>PATH=/path/with/llvm-config:$PATH meson build</code>.
</p></dd>
</dl>
<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 Linux and *BSD. 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 "debugoptimized", and not setting it to
"release" will yield non-optimal performance and binary size. Not using "debug"
may interfer with debbugging as some code and validation will be optimized
away.
</p>
<p> For those wishing to pass their own -O option, use the "plain" buildtype,
which cuases meson to inject no additional compiler arguments, only those in
the C/CXXFLAGS and those that mesa itself defines.</p>
</dd>
</dl>
<dl>
<dt><code>-Db_ndebug</code></dt>
<dd><p>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 <code>buildtype</code>; setting the latter to
<code>release</code> will not turn off assertions.
</p>
</dd>
</dl>