The Meson Build System
http://mesonbuild.com/
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157 lines
6.4 KiB
157 lines
6.4 KiB
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short-description: Building a project with Meson |
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# Running Meson |
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There are two different ways of invoking Meson. First, you can run it |
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directly from the source tree with the command |
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`/path/to/source/meson.py`. Meson may also be installed in which case |
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the command is simply `meson`. In this manual we only use the latter |
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format for simplicity. |
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At the time of writing only a command line version of Meson is |
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available. This means that Meson must be invoked using the |
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terminal. If you wish to use the MSVC compiler, you need to run Meson |
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under "Visual Studio command prompt". |
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Configuring the source |
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== |
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Let us assume that we have a source tree that has a Meson build |
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system. This means that at the topmost directory has a file called |
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`meson.build`. We run the following commands to get the build started. |
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cd /path/to/source/root |
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mkdir builddir |
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cd builddir |
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meson .. |
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First we create a directory to hold all files generated during the |
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build. Then we go into it and invoke Meson, giving it the location of |
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the source root. |
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Hint: The syntax of meson is `meson [options] [srcdir] [builddir]`, |
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but you may omit either `srcdir` or `builddir`. Meson will deduce the |
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`srcdir` by the location of `meson.build`. The other one will be your |
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`pwd`. |
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Meson then loads the build configuration file and writes the |
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corresponding build backend in the build directory. By default Meson |
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generates a *debug build*, which turns on basic warnings and debug |
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information and disables compiler optimizations. |
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You can specify a different type of build with the `--buildtype` |
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command line argument. It can have one of the following values. |
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| value | meaning | |
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| ------ | -------- | |
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| `plain` | no extra build flags are used, even for compiler warnings, useful for distro packagers and other cases where you need to specify all arguments by yourself | |
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| `debug` | debug info is generated but the result is not optimized, this is the default | |
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| `debugoptimized` | debug info is generated and the code is optimized (on most compilers this means `-g -O2`) | |
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| `release` | full optimization, no debug info | |
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The build directory is mandatory. The reason for this is that it |
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simplifies the build process immensely. Meson will not under any |
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circumstances write files inside the source directory (if it does, it |
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is a bug and should be fixed). This means that the user does not need |
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to add a bunch of files to their revision control's ignore list. It |
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also means that you can create arbitrarily many build directories for |
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any given source tree. If we wanted to test building the source code |
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with the Clang compiler instead of the system default, we could just |
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type the following commands. |
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cd /path/to/source/root |
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mkdir buildclang |
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cd buildclang |
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CC=clang CXX=clang++ meson .. |
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This separation is even more powerful if your code has multiple |
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configuration options (such as multiple data backends). You can create |
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a separate subdirectory for each of them. You can also have build |
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directories for optimized builds, code coverage, static analysis and |
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so on. They are all neatly separated and use the same source |
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tree. Changing between different configurations is just a question of |
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changing to the corresponding directory. |
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Unless otherwise mentioned, all following command line invocations are |
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meant to be run in the build directory. |
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By default Meson will use the Ninja backend to build your project. If |
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you wish to use any of the other backends, you need to pass the |
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corresponding argument during configuration time. As an example, here |
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is how you would use Meson to generate a Visual studio solution. |
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meson <source dir> <build dir> --backend=vs2010 |
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You can then open the generated solution with Visual Studio and |
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compile it in the usual way. A list of backends can be obtained with |
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`meson --help`. |
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Building the source |
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== |
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If you are not using an IDE, Meson uses the [Ninja build |
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system](https://ninja-build.org/) to actually build the code. To start |
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the build, simply type the following command. |
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ninja |
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The main usability difference between Ninja and Make is that Ninja |
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will automatically detect the number of CPUs in your computer and |
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parallelize itself accordingly. You can override the amount of |
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parallel processes used with the command line argument `-j <num |
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processes>`. |
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It should be noted that after the initial configure step `ninja` is |
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the only command you ever need to type to compile. No matter how you |
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alter your source tree (short of moving it to a completely new |
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location), Meson will detect the changes and regenerate itself |
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accordingly. This is especially handy if you have multiple build |
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directories. Often one of them is used for development (the "debug" |
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build) and others only every now and then (such as a "static analysis" |
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build). Any configuration can be built just by `cd`'ing to the |
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corresponding directory and running Ninja. |
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Running tests |
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== |
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Meson provides native support for running tests. The command to do |
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that is simple. |
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ninja test |
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Meson does not force the use of any particular testing framework. You |
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are free to use GTest, Boost Test, Check or even custom executables. |
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Installing |
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== |
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Installing the built software is just as simple. |
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ninja install |
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Note that Meson will only install build targets explicitly tagged as |
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installable, as detailed in the [installing targets documentation](Installing.md). |
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By default Meson installs to `/usr/local`. This can be changed by |
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passing the command line argument `--prefix /your/prefix` to Meson |
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during configure time. Meson also supports the `DESTDIR` variable used |
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in e.g. building packages. It is used like this: |
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DESTDIR=/path/to/staging ninja install |
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Command line help |
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== |
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Meson has a standard command line help feature. It can be accessed |
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with the following command. |
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meson --help |
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Exit status |
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== |
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Meson exits with status 0 if successful, 1 for problems with the command line or |
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meson.build file, and 2 for internal errors.
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