[Mesa-dev] [PATCH] docs: add documentation for building with meson

Wed Nov 8 12:00:54 UTC 2017

On Tuesday, 2017-11-07 09:28:35 -0800, Dylan Baker wrote:
> v2: - Add information about CC, CXX, CFLAGS, and CXXFLAGS (Nicolai)
>     - Add message at top that meson for mesa is still a work in progress
>     - Add trailing "/" to directories (Eric E.)
>     - Fix a number of spelling/grammar/style suggestions from Eric E.
>     - Make a number of changes as suggested by Emil.
> v3: - Fix order of commands in example (Eric E.)
>     - Add documentation for overriding LLVM version (Eric E.)
> v4: - Rebase on master
>     - update default buildtype
>     - add note about b_ndebug
>     - Clarify meson configure a bit
> 
> Signed-off-by: Dylan Baker <dylanx.c.baker at intel.com>
> Reviewed-by: Eric Engestrom <eric at engestrom.ch> (v3)
> ---
>  docs/contents.html |   1 +
>  docs/meson.html    | 151 +++++++++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 152 insertions(+)
>  create mode 100644 docs/meson.html
> 
> diff --git a/docs/contents.html b/docs/contents.html
> index d5455421091..9a86019e2f6 100644
> --- a/docs/contents.html
> +++ b/docs/contents.html
> @@ -43,6 +43,7 @@
>  <li><a href="install.html" target="_parent">Compiling / Installing</a>
>    <ul>
>      <li><a href="autoconf.html" target="_parent">Autoconf</a></li>
> +    <li><a href="meson.html" target="_parent">Meson</a></li>
>    </ul>
>  </li>
>  <li><a href="precompiled.html" target="_parent">Precompiled Libraries</a>
> diff --git a/docs/meson.html b/docs/meson.html
> new file mode 100644
> index 00000000000..ee505b1d5ee
> --- /dev/null
> +++ b/docs/meson.html
> @@ -0,0 +1,151 @@
> +<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
> +<html lang="en">
> +<head>
> +  <meta http-equiv="content-type" content="text/html; charset=utf-8">
> +  <title>Compilation and Installation using Meson</title>
> +  <link rel="stylesheet" type="text/css" href="mesa.css">
> +</head>
> +<body>
> +
> +<div class="header">
> +  <h1>The Mesa 3D Graphics Library</h1>
> +</div>
> +
> +<iframe src="contents.html"></iframe>
> +<div class="content">
> +
> +<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, and must
> +be enabled via the --backend switch, as ninja is always the default. Meson only

missing words in that last sentence

> +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 "meson configure" along with a

<code>meson configure</code>

same for the other commands in this page, as this is the way we show
them in the rest of the docs

> +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 configuring
+ a build directory, but this feature is being discussed upstream.

(since the question came up a couple times already)

> +</p>
> +
> +<pre>
> +    meson configure build/
> +</pre>
> +
> +<p>
> +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".

Doesn't matter to meson, but I'd put a space between `-D` and
`"command"="value"` to make it more readable.

> +</p>
> +
> +<pre>
> +    meson configure build/ -Dprefix=/tmp/install -Dglx=true
> +</pre>
> +
> +<p>
> +Once you've run meson successfully you can use your configured backend to build

"Once you've run the initial <code>meson</code> successfully"
("initial" being the important change)

> +the project.

+ You probably don't need to ever run <code>meson</code> after that,
+ as running <code>ninja</code> (and other backends) automatically detects
+ changes and re-configures the project as needed. If you think some change
+ is not being detected correctly, you can always run
+ <code>ninja reconfigure</code> manually.

> 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
> +rebuilding,

before changing the configuration, I think?

Feels weird to give this advice though. One of the arguments for having
your build out of tree is that your various build configurations don't
interfere with each other, so let's just suggest
"different config? different build dir"

> or create a new out of tree build directory (meson supports an
> +unlimited number of them) for each configuration you want to build.

This "unlimited build dirs" sentence looks weird to me every time I read
it. Why would there be a limit to the number of build dirs?
Maybe saying something like "meson doesn't restrict you to a single
build dir" would be clearer, but mentioning it at all still feels weird.

Maybe add a link to the meson doc on out of tree builds?
http://mesonbuild.com/Using-multiple-build-directories.html

> +</p>
> +
> +<dt><code>CC, CFLAGS, CXX, CXXFLAGS</code></dt>

weird to list them, but if you do, might as well have LDFLAGS in the
list :)

> +<dd><p>These environment variables
> +control the C and C++ compilers used during the build. 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>
> +</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.</p>

+ and not setting it to "debug" might interfere with your ability to
+ debug Mesa, as some code & variables will be optimised out.

> +
> +<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

"causes"

> +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.</p>

+ This is unrelated to the <code>buildtype</code>; setting the latter to
+ <code>release</code> will not turn off assertions, for instance.

> +</dd>
> +</dl>
> -- 
> 2.15.0
> 