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Nirbheek Chauhan edited this page Mar 24, 2017 · 272 revisions

This page lists functions and methods available in Meson scripts. For more in-depth documentation on how to use them, refer to the manual. For more basic information about how Meson works, take a look at the syntax reference.

Functions

The following functions are available in build files. Click on each to see the description and usage. The objects returned by them are list afterwards.

Built-in objects

These are built-in objects that are always available.

Returned objects

These are objects returned by the functions listed above.

add_global_arguments

void add_global_arguments(arg1, arg2, ...)

Adds the positional arguments to the compiler command line for the language specified in language keyword argument. Note that there is no way to remove an argument set in this way. If you have an argument that is only used in a subset of targets, you have to specify it in per-target flags.

The arguments are used in all compiler invocations with the exception of compile tests, because you might need to run a compile test with and without the argument in question. For this reason only the arguments explicitly specified are used during compile tests.

Note: Usually you should use add_project_arguments instead, because that works even when you project is used as a subproject.

Note: You must pass always arguments individually arg1, arg2, ... rather than as a string 'arg1 arg2', ...

add_global_link_arguments

void add_global_link_arguments(*arg1*, *arg2*, ...)

Like add_global_arguments but the arguments are passed to the linker.

add_languages

add_languages(*langs*)

Add support for new programming languages. Equivalent to having them in the project declaration. This function is usually used to add languages that are only used on some platforms like this:

project('foobar', 'c')
if compiling_for_osx
  add_languages('objc')
endif

Takes one keyword argument, required. It defaults to true, which means that if any of the languages specified is not found, Meson will halt. Returns true if all languages specified were found and false otherwise.

add_project_arguments

void add_project_arguments(arg1, arg2, ...)

This function behaves in the same way as add_global_arguments except that the arguments are only used for the current project, they won't be used in any other subproject.

add_project_link_arguments

void add_project_link_arguments(*arg1*, *arg2*, ...)

Like add_project_arguments but the arguments are passed to the linker.

add_test_setup

void add_test_setup(*name*, ...)

Add a custom test setup that can be used to run the tests with a custom setup, for example under Valgrind. The keyword arguments are the following:

  • exe_wrapper a list containing the wrapper command or script followed by the arguments to it
  • gdb if true, the tests are also run under gdb
  • timeout_multiplier a number to multiply the test timeout with
  • env an environment object to use a custom environment

To use the test setup, run mesontest --setup=*name* inside the build dir.

Note that all these options are also available while running the mesontest script for running tests instead of ninja test or msbuild RUN_TESTS.vcxproj, etc depending on the backend.

benchmark

void benchmark(name, executable, ...)

Creates a benchmark item that will be run when the benchmark target is run. The behaviour of this function is identical to test with the exception that there is no is_parallel keyword, because benchmarks are never run in parallel.

build_target

Creates a build target whose type can be set dynamically with the target_type keyword argument. This declaration:

executable(<arguments and keyword arguments>)

is equivalent to this:

build_target(<arguments and keyword arguments>, target_type : 'executable')

The object returned by build_target and all convenience wrappers for build_target such as executable and library has methods that are documented in the object methods section below.

configuration_data

configuration_data_object = configuration_data()

Creates an empty configuration object. You should add your configuration with its method calls and finally use it in a call to configure_file.

configure_file

generated_file = configure_file(...)

This function can run in two modes depending on the keyword arguments passed to it.

When a configuration_data() object is passed to the configuration: keyword argument, it takes a template file as the input: (optional) and produces the output: (required) by substituting values from the configuration data as detailed in the configuration file documentation.

When a list of strings is passed to the command: keyword argument, it takes any source or configured file as the input: and assumes that the output: is produced when the specified command is run.

These are all the supported keyword arguments:

  • input the input file name. If it's not specified in configuration mode, all the variables in the configuration: object (see above) are written to the output: file.
  • output the output file name. In configuration mode, the permissions of the input file (if it is specified) are copied to the output file.
  • configuration as explained above, this is where you pass the configuration data object as returned by configuration_data()
  • command as explained above, if specified, Meson does not create the file itself but rather runs the specified command, which allows you to do fully custom file generation
  • install_dir the subdirectory to install the generated file to (e.g. share/myproject), if omitted the file is not installed.

custom_target

ctarget custom_target(*name*, ...)

Create a custom top level build target. The only positional argument is the name of this target and the keyword arguments are the following.

  • input list of source files
  • output list of output files
  • command command to run to create outputs from inputs. The command may be strings or the return of find_program() or executable() (note: always specify commands in array form ['commandname', '-arg1', '-arg2'] rather than as a string 'commandname -arg1 -arg2' as the latter will not work)
  • install when true, this target is installed during the install step
  • install_dir directory to install to
  • build_always if true this target is always considered out of date and is rebuilt every time, useful for things such as build timestamps or revision control tags
  • capture, there are some compilers that can't be told to write their output to a file but instead write it to standard output. When this argument is set to true, Meson captures stdout and writes it to the target file. Note that your command argument list may not contain @OUTPUT@ when capture mode is active.
  • depends specifies that this target depends on the specified target(s), even though it does not take any of them as a command line argument. This is meant for cases where you have a tool that e.g. does globbing internally. Usually you should just put the generated sources as inputs and Meson will set up all dependencies automatically.
  • depend_files files (string, files(), or configure_file()) that this target depends on but are not listed in the command kwarg. Useful for adding regen dependencies.
  • depfile is a dependency file that the command can write listing all the additional files this target depends on, for example a C compiler would list all the header files it included, and a change in any one of these files triggers a recompilation
  • build_by_default (added 0.38.0) causes, when set to true, to have this target be built by default, that is, when invoking plain ninja; the default value is false

The list of strings passed to the command kwarg accept the following special string substitutions:

  • @INPUT@ the full path to the input passed to input. If more than one input is specified, all of them will be substituted as separate arguments only if the command uses '@INPUT@' as a standalone-argument. For instance, this would not work: command : ['cp', './@INPUT@'], but this would: command : ['cp', '@INPUT@'].
  • @OUTPUT@ the full path to the output passed to output. If more than one outputs are specified, the behaviour is the same as @INPUT@.
  • @INPUT0@ @INPUT1@ ... the full path to the input with the specified array index in input
  • @OUTPUT0@ @OUTPUT1@ ... the full path to the output with the specified array index in output
  • @OUTDIR@ the full path to the directory where the output(s) must be written
  • @DEPFILE@ the full path to the dependency file passed to depfile

declare_dependency

dependency_object declare_dependency(...)

This function returns a dependency object that behaves like the return value of dependency but is internal to the current build. The main use case for this is in subprojects. This allows a subproject to easily specify how it should be used. This makes it interchangeable with the same dependency that is provided externally by the system. This function has three keyword arguments.

  • include_directories, the directories to add to header search path
  • link_with, libraries to link against
  • sources, sources to add to targets (or generated header files that should be built before sources including them are built)
  • dependencies, other dependencies needed to use this dependency
  • compile_args, compile arguments to use
  • link_args, link arguments to use
  • version, the version of this depency, such as 1.2.3

dependency

dependency_object dependency(*dependency_name*, ...)

Finds an external dependency with the given name with pkg-config if possible and with fallback detection logic otherwise. Dependency supports the following keyword arguments.

  • modules specifies submodules to use for dependencies such as Qt5 or Boost.
  • required, when set to false, Meson will proceed with the build even if the dependency is not found
  • version, specifies the required version, a string containing a comparison operator followed by the version string, examples include >1.0.0, <=2.3.5 or 3.1.4 for exact matching. (Added 0.37.0) You can also specify multiple restrictions by passing a list to this kwarg, such as: ['>=3.14.0', '<=4.1.0'].
  • native if set to true, causes Meson to find the dependency on the build machine system rather than the host system (i.e. where the cross compiled binary will run on), usually only needed if you build a tool to be used during compilation.
  • static tells the dependency provider to try to get static libraries instead of dynamic ones (note that this is not supported by all dependency backends)
  • fallback specifies a subproject fallback to use in case the dependency is not found in the system. The value is an array ['subproj_name', 'subproj_dep'] where the first value is the name of the subproject and the second is the variable name in that subproject that contains the value of declare_dependency.
  • default_options (added 0.37.0) an array of option values that override those set in the project's default_options invocation (like default_options in project(), they only have effect when Meson is run for the first time, and command line arguments override any default options in build files)

The returned object also has methods that are documented in the object methods section below.

error

void error(message)

Print the argument string and halts the build process.

environment

environment_object environment()

Returns an empty environment variable object.

executable

exe executable(*exe_name*, *sources*, ...)

Creates a new executable. The first argument specifies its name and the remaining positional arguments define the source files to use. They can be of the following types:

These source files can be sources, objects, libraries, or any other file. Meson will automatically categorize them based on the extension and use them accordingly. For instance, sources (.c, .cpp, .vala, .rs, etc) will be compiled, objects (.o, .obj) and libraries (.so, .dll, etc) will be linked, and all other files (headers, unknown extensions, etc) will be ignored. Meson will still create a build-time dependency on all source files, which is useful with generated files.

Executable supports the following keyword arguments. Note that just like the positional arguments above, these keyword arguments can also be passed to shared and static libraries.

  • link_with, one or more shared or static libraries (built by this project) that this target should be linked with
  • <languagename>_pch precompiled header file to use for the given language
  • <languagename>_args compiler flags to use for the given language; eg: cpp_args for C++
  • link_args flags to use during linking. You can use unix-style flags here for all platforms.
  • link_depends an extra file that the link step depends on such as a symbol visibility map
  • include_directories one or more objects created with the include_directories function
  • dependencies one or more objects created with dependency or find_library (for external deps) or declare_dependency (for deps built by the project)
  • gui_app when set to true flags this target as a GUI application on platforms where this makes a difference (e.g. Windows)
  • extra_files are not used for the build itself but are shown as source files in IDEs that group files by targets (such as Visual Studio)
  • install, when set to true, this executable should be installed
  • install_rpath a string to set the target's rpath to after install (but not before that)
  • install_dir override install directory for this file. The value is relative to the prefix specified. F.ex, if you want to install plugins into a subdir, you'd use something like this: install_dir : get_option('libdir') + '/projectname-1.0'.
  • objects list of prebuilt object files (usually for third party products you don't have source to) that should be linked in this target, never use this for object files that you build yourself.
  • name_suffix the string that will be used as the extension for the target by overriding the default. By default on Windows this is exe and on other platforms it is omitted.
  • build_by_default causes, when set to true, to have this target be built by default, that is, when invoking plain ninja, the default value is true for all built target types, since 0.38.0

The list of sources, objects, and dependencies is always flattened, which means you can freely nest and add lists while creating the final list. As a corollary, the best way to handle a 'disabled dependency' is by assigning an empty list [] to it and passing it like any other dependency to the dependencies: kwarg.

The returned object also has methods that are documented in the object methods section below.

find_library

This function is deprecated and in the 0.31.0 release it was moved to the compiler object as obtained from meson.get_compiler(lang).

find_program

program find_program(program_name1, program_name2, ...)

program_name1 here is a string that can be an executable or script to be searched for in PATH, or a script in the current source directory.

Meson will also autodetect scripts with a shebang line and run them with the executable/interpreter specified in it both on Windows (because the command invocator will reject the command otherwise) and UNIXes (if the script file does not have the executable bit set). Hence, you must not manually add the interpreter while using this script as part of a list of commands.

program_name2 and later positional arguments are used as fallback strings to search for. This is meant to be used for cases where the program may have many alternative names, such as foo and foo.py. The function will check for the arguments one by one and the first one that is found is returned. Meson versions earlier than 0.37.0 only accept one argument.

If none of the programs are found, Meson will abort. You can tell it not to by setting the keyword argument required to false, and then use the .found() method on the returned object to check whether it was found or not.

The returned object also has methods that are documented in the object methods section below.

files

file_array files(list_of_filenames)

This command takes the strings given to it in arguments and returns corresponding File objects that you can use as sources for build targets. The difference is that file objects remember the subdirectory they were defined in and can be used anywhere in the source tree. As an example suppose you have source file foo.cpp in subdirectory bar1 and you would like to use it in a build target that is defined in bar2. To make this happen you first create the object in bar1 like this:

    foofile = files('foo.cpp')

Then you can use it in bar2 like this:

    executable('myprog', 'myprog.cpp', foofile, ...)

Meson will then do the right thing.

generator

generator_object gen(*executable*, ...)

See also: custom_target

This function creates a generator object that can be used to run custom compilation commands. The only positional argument is the executable to use. It can either be a self-built executable or one returned by find_program. Keyword arguments are the following:

  • arguments a list of template strings that will be the command line arguments passed to the executable
  • output a template string (or list of template strings) defining how an output file name is (or multiple output names are) generated from a single source file name
  • depfile is a template string pointing to a dependency file that a generator can write listing all the additional files this target depends on, for example a C compiler would list all the header files it included, and a change in any one of these files triggers a recompilation

The returned object also has methods that are documented in the object methods section below.

The template strings passed to all the above kwargs accept the following special substitutions:

  • @PLAINNAME@: the complete input file name, e.g: foo.c becomes foo.c (unchanged)
  • @BASENAME@: the base of the input filename, e.g.: foo.c.y becomes foo.c (extension is removed)

Each string passed to the outputs kwarg must be constructed using one or both of these two substitutions.

In addition to the above substitutions, the arguments kwarg also accepts the following:

  • @OUTPUT@: the full path to the output file
  • @INPUT@: the full path to the input file
  • @SOURCE_DIR@: the full path to the root of the source tree
  • @BUILD_DIR@: the full path to the root of the build dir where the output will be placed

NOTE: Generators should only be used for outputs that will only be used as inputs for a build target or a custom target. When you use the processed output of a generator in multiple targets, the generator will be run multiple times to create outputs for each target. Each output will be created in a target-private directory @BUILD_DIR@.

If you want to generate files for general purposes such as for generating headers to be used by several sources, or data that will be installed, and so on, use a custom_target instead.

get_option

value get_option(option_name)

Obtains the value of the [project build option](Build options) specified in the positional argument.

get_variable

value get_variable(variable_name, fallback)

This function can be used to dynamically obtain a variable. res = get_variable(varname, fallback) takes the value of varname (which must be a string) and stores the variable of that name into res. If the variable does not exist, the variable fallback is stored to resinstead. If a fallback is not specified, then attempting to read a non-existing variable will cause a fatal error.

import

module_object import(module_name)

Imports the given extension module. Returns an opaque object that can be used to call the methods of the module. Here's an example for a hypothetical testmod module.

    tmod = import('testmod')
    tmod.do_something()

include_directories

include_object include_directories(directory_names, ...)

Returns an opaque object which contains the directories given in positional arguments. The result can then be used as a keyword argument when building executables or libraries. Both the source directory and the corresponding build directory are added. Note that this function call itself does not add the directories into the search path, since there is no global search path. You can use the the returned object in any subdirectory you want, Meson will make the paths work automatically. This function has one keyword argument is_system which, if set, flags the specified directories as system directories. This means that they will be used with the -isystem compiler argument rather than -I on compilers that support this flag (in practice everything except Visual Studio).

install_data

void install_data(list_of_files, ...)

Installs files from the source tree that are listed as positional arguments. The following keyword arguments are supported:

  • install_dir the absolute or relative path to the installation directory. If this is a relative path, it is assumed to be relative to the prefix.

  • install_mode specify the file mode in symbolic format and optionally the owner/uid and group/gid for the installed files. For example:

    install_mode: 'rw-r--r--' for just the file mode

    install_mode: ['rw-r--r--', 'nobody', 'nobody'] for the file mode and the user/group

    install_mode: ['rw-r-----', 0, 0] for the file mode and uid/gid

To leave any of these three as the default, specify false.

install_headers

void install_headers(list_of_headers, ...)

Installs the specified header files from the source tree into the system header directory (usually /{prefix}/include) during the install step. This directory can be overridden by specifying it with the install_dir keyword argument. If you just want to install into a subdirectory of the system header directory, then use the subdir argument. As an example if this has the value myproj then the headers would be installed to /{prefix}/include/myproj.

For example, this will install common.h and kola.h into /{prefix}/include:

install_headers('common.h', 'proj/kola.h')

This will install common.h and kola.h into /{prefix}/include/myproj:

install_headers('common.h', 'proj/kola.h', subdir : 'myproj')

This will install common.h and kola.h into /{prefix}/cust/myproj:

install_headers('common.h', 'proj/kola.h', install_dir : 'cust', subdir : 'myproj')

install_man

void install_man(list_of_manpages, ...)

Installs the specified man files from the source tree into system's man directory during the install step. This directory can be overridden by specifying it with the install_dir keyword argument.

install_subdir

void install_subdir(subdir_name)

Installs the entire given subdirectory and its contents from the source tree to the location specified by the keyword argument install_dir. Note that due to implementation issues this command deletes the entire target dir before copying the files, so you should never use install_subdir to install into two overlapping directories (such as foo and foo/bar) because if you do the behaviour is undefined.

is_variable

bool is_variable(varname)

Returns true if a variable of the given name exists and false otherwise.

jar

jar_object jar(name, list_of_sources, ...)

Build a jar from the specified Java source files. Keyword arguments are the same as executable's, with the addition of main_class which specifies the main class to execute when running the jar with java -jar file.jar.

join_paths

string join_paths(string1, string2, ...)

Joins the given strings into a file system path segment. For example join_paths('foo', 'bar') results in foo/bar. If any one of the individual segments is an absolute path, all segments before it are dropped. That means that join_paths('foo', '/bar') returns /bar.

Added 0.36.0

library

buildtarget library(library_name, list_of_sources, ...)

Builds a library that is either static or shared depending on the value of default_library user option. You should use this instead of shared_library or static_library most of the time. This allows you to toggle your entire project (including subprojects) from shared to static with only one option.

The keyword arguments for this are the same as for executable with the following addition:

  • name_prefix the string that will be used as the suffix for the target by overriding the default (only used for libraries). By default this is lib on all platforms and compilers except with MSVC where it is omitted.

static_library and shared_library also accept this keyword argument.

message

void message(text)

This function prints its argument to stdout.

project

void project(project_name, list_of_languages, ...)

The first argument to this function must be a string defining the name of this project. It must be followed by one or more programming languages that the project uses. Supported values for languages are c, cpp (for C++), objc, objcpp, fortran, java, cs (for C#) and vala.

The project name can be any string you want, it's not used for anything except descriptive purposes. However since it is written to e.g. the dependency manifest is usually makes sense to have it be the same as the project tarball or pkg-config name. So for example you would probably want to use the name libfoobar instead of The Foobar Library.

Project supports the following keyword arguments.

  • version, which is a free form string describing the version of this project. You can access the value in your Meson build files with meson.project_version().

  • subproject_dir specifies the top level directory name that holds Meson subprojects. This is only meant as a compatibility option for existing code bases that house their embedded source code in a custom directory. All new projects should not set this but instead use the default value. It should be noted that this keyword argument is ignored inside subprojects. There can be only one subproject dir and it is set in the top level Meson file.

  • meson_version takes a string describing which Meson version the project requires. Usually something like >0.28.0. Similarly you can specify the license(s) the code is under with the license keyword argument. Usually this would be something like license : 'GPL2+', but if the code has multiple licenses you can specify them as an array like this: license : ['proprietary', 'GPL3']. Note that the text is informal and is only written to the dependency manifest. Meson does not do any license validation, you are responsible for verifying that you abide by all licensing terms.

  • default_options takes an array of strings. The strings are in the form key=value and have the same format as options to mesonconf. For example to set the default project type you would set this: default_options : ['buildtype=debugoptimized']. Note that these settings are only used when running Meson for the first time. Global options such as buildtype can only be specified in the master project, settings in subprojects are ignored. Project specific options are used normally even in subprojects.

run_command

runresult run_command(command, list_of_args)

Runs the command specified in positional arguments. Returns an opaque object containing the result of the invocation. The script is run from an unspecified directory, and Meson will set three environment variables MESON_SOURCE_ROOT, MESON_BUILD_ROOT and MESON_SUBDIR that specify the source directory, build directory and subdirectory the target was defined in, respectively.

run_target

buildtarget run_target(target_name, ...)

This function creates a new top-level target that runs a specified command with the specified arguments. Like all top-level targets, this integrates with the selected backend. For instance, with Ninja you can run it as ninja target_name.

The script is run from an unspecified directory, and Meson will set three environment variables MESON_SOURCE_ROOT, MESON_BUILD_ROOT and MESON_SUBDIR that specify the source directory, build directory and subdirectory the target was defined in, respectively.

  • command is a list containing the command to run and the arguments to pass to it. Each list item may be a string or a target. For instance, passing the return value of executable() as the first item will run that executable, or passing a string as the first item will find that command in PATH and run it.
  • depends is a list of targets that this target depends on but which are not listed in the command array (because, for example, the script does file globbing internally)

set_variable

void set_variable(variable_name, value)

Assigns a value to the given variable name. Calling set_variable('foo', bar) is equivalent to foo = bar.

shared_library

buildtarget shared_library(library_name, list_of_sources, ...)

Builds a shared library with the given sources. Positional and keyword arguments are the same as for library with the following extra keyword arguments.

  • version a string specifying the version of this shared library, such as 1.1.0. On Linux and OS X, this is used to set the shared library version in the filename, such as libfoo.so.1.1.0 and libfoo.1.1.0.dylib. If this is not specified, soversion is used instead (see below).
  • soversion a string specifying the soversion of this shared library, such as 0. On Linux and Windows this is used to set the soversion (or equivalent) in the filename. For example, if soversion is 4, a Windows DLL will be called foo-4.dll and one of the aliases of the Linux shared library would be libfoo.so.4. If this is not specified, the first part of version is used instead. For example, if version is 3.6.0 and soversion is not defined, it is set to 3.
  • vs_module_defs a string pointing to a file that contains Visual Studio symbol export definitions.

shared_module

buildtarget shared_module(module_name, list_of_sources, ...)

Builds a shared module with the given sources. Positional and keyword arguments are the same as for library.

This is useful for building modules that will be dlopen()ed and hence may contain undefined symbols that will be provided by the library that is loading it.

Added 0.37.0

static_library

buildtarget static_library(library_name, list_of_sources, ...)

Builds a static library with the given sources. Positional and keyword arguments are otherwise the same as for library, but it has one argument the others don't have:

  • pic, (Added 0.36.0) builds the library as positional independent code (so it can be linked into a shared library). This option has no effect on Windows and OS X since it doesn't make sense on Windows and PIC cannot be disabled on OS X.

subdir

void subdir(dir_name)

Enters the specified subdirectory and executes the meson.build file in it. Once that is done, it returns and execution continues on the line following this subdir() command. Variables defined in that meson.build file are then available for use in later parts of the current build file and in all subsequent build files executed with subdir().

Note that this means that each meson.build file in a source tree can and must only be executed once.

subproject

subproject_object subproject(subproject_name, ...)

Takes the project specified in the positional argument and brings that in the current build specification by returning a subproject object. Subprojects must always be placed inside the subprojects directory at the top source directory. So for example a subproject called foo must be located in ${MESON_SOURCE_ROOT}/subprojects/foo. Supports the following keyword arguments:

  • version keyword argument that works just like the one in dependency. It specifies what version the subproject should be, as an example >=1.0.1
  • default_options, (added 0.37.0) an array of default option values that override those set in the project's default_options invocation (like default_options in project, they only have effect when Meson is run for the first time, and command line arguments override any default options in build files)

test

void test(name, executable, ...)

Defines an unit test. Takes two positional arguments, the first is the name of this test and the second is the executable to run. Keyword arguments are the following.

  • args arguments to pass to the executable
  • env environment variables to set, such as ['NAME1=value1', 'NAME2=value2']
  • is_parallel when false, specifies that no other test must be running at the same time as this test
  • should_fail when true the test is considered passed if the executable returns a non-zero return value (i.e. reports an error)
  • valgrind_args if the test is run under Valgrind, pass these arguments to Valgrind (and not to the executable itself)
  • timeout the amount of seconds the test is allowed to run, a test that exceeds its time limit is always considered failed, defaults to 30 seconds
  • workdir absolute path that will be used as the working directory for the test

Defined tests can be run in a backend-agnostic way by calling mesontest inside the build dir, or by using backend-specific commands, such as ninja test or msbuild RUN_TESTS.vcxproj.

vcs_tag

ctarget vcs_tag(...)

This command detects revision control commit information at build time and places it in the specified output file. This file is guaranteed to be up to date on every build. Keywords are similar to custom_target and all of them are mandatory.

  • input file to modify (e.g. version.c.in)
  • output file to write the results to (e.g. version.c)
  • fallback version number to use when no revision control information is present, such as when building from a release tarball

Meson will read the contents of input, replace the string @VCS_TAG@ with the detected revision number and write the result to output. This method returns an opaque custom_target object that you should put in your main program. If you desire more specific behavior than what this command provides, you should use custom_target.

Object methods

Meson has several different object types that have methods users can call. This section describes them.

meson object

The meson object allows you to introspect various properties of the system. This object is always mapped in the meson variable. It has the following methods.

  • get_compiler(language) returns an object describing a compiler, takes one positional argument which is the language to use. It also accepts one keyword argument, native which when set to true makes Meson return the compiler for the build machine (the "native" compiler) and when false it returns the host compiler (the "cross" compiler). If native is omitted, Meson returns the "cross" compiler if we're currently cross-compiling and the "native" compiler if we're not.

  • backend() (added 0.37.0) returns a string representing the current backend: ninja, vs2010, vs2015, or xcode.

  • is_cross_build() returns true if the current build is a cross build and false otherwise

  • is_unity() returns true when doing a unity build and false otherwise

  • is_subproject() returns true if the current project is being built as a subproject of some other project and false otherwise

  • has_exe_wrapper() returns true when doing a cross build if there is a wrapper command that can be used to execute cross built binaries (for example when cross compiling from Linux to Windows, one can use wine as the wrapper)

  • add_install_script(script_name, arg1, arg2, ...) causes the script given as an argument to be run during the install step, this script will have the environment variables MESON_SOURCE_ROOT, MESON_BUILD_ROOT, MESON_INSTALL_PREFIX, and MESON_INSTALL_DESTDIR_PREFIX set. All additional arguments are passed as parameters.

MESON_INSTALL_PREFIX has the value of the prefix option passed to Meson, and MESON_INSTALL_DESTDIR_PREFIX has both the value of DESTDIR and prefix joined together. This is useful because both are absolute paths, and many path-joining functions such as os.path.join in Python special-case absolute paths.

  • add_postconf_script(script_name, arg1, arg2, ...) will run the executable given as an argument after all project files have been generated. This script will have the environment variables MESON_SOURCE_ROOT and MESON_BUILD_ROOT set.

  • current_source_dir() returns a string to the current source directory. Note: you do not need to use this function when passing files from the current source directory to a function since that is the default. Also, you can use the files() function to refer to files in the current or any other source directory instead of constructing paths manually with meson.current_source_dir().

  • current_build_dir() returns a string to the current build directory

  • source_root() returns a string with the absolute path to the source root directory. Note: you should use the files() function to refer to files in the root source directory instead of constructing paths manually with meson.source_root().

  • build_root() returns a string with the absolute path to the build root directory

  • project_version() returns the version string specified in project function call

  • project_name() returns the project name specified in the project function call

  • version() return a string with the version of Meson

  • get_cross_property(propname, fallback_value) returns the given property from a cross file, the optional second argument is returned if not cross compiling or the given property is not found

  • install_dependency_manifest(output_name) installs a manifest file containing a list of all subprojects, their versions and license files to the file name given as the argument

build_machine object

Provides information about the build machine — the machine that is doing the actual compilation. See Cross-compilation. It has the following methods:

  • cpu_family() returns the CPU family name. Guaranteed to return x86 for 32-bit userland on x86 CPUs, x86_64 for 64-bit userland on x86 CPUs, arm for 32-bit userland on all ARM CPUs, etc.
  • cpu() returns a more specific CPU name, such as i686, amd64, etc.
  • system() returns the operating system name, such as windows (all versions of Windows), linux (all Linux distros), darwin (all versions of OS X), etc.
  • endian() returns big on big-endian systems and little on little-endian systems.

If you think the returned values for any of these are incorrect for your system or CPU, please file a bug report.

host_machine object

Provides information about the host machine — the machine on which the compiled binary will run. See Cross-compilation.

It has the same methods as build_machine, but note that it simply returns the values defined in the cross-info file.

target_machine object

Provides information about the target machine — the machine on which the compiled binary's output will run. Hence, this object should only be used while cross-compiling a compiler. See Cross-compilation.

It has the same methods as build_machine, but note that it simply returns the values defined in the cross-info file. If target_machine values are not defined in the cross-info file, host_machine values are returned instead.

build target object

A build target is either an executable, shared or static library.

  • extract_objects() returns an opaque value representing the generated object files of arguments, usually used to take single object files and link them to unit tests or to compile some source files with custom flags. To use the object file(s) in another build target, use the objects: keyword argument.

  • extract_all_objects() is same as above but returns all object files generated by this target

  • private_dir_include() returns a opaque value that works like include_directories but points to the private directory of this target, usually only needed if an another target needs to access some generated internal headers of this target

  • full_path() returns a full path pointing to the result target file

compiler object

This object is returned by meson.get_compiler(lang). It represents a compiler for a given language and allows you to query its properties. It has the following methods:

  • get_id() returns a string identifying the compiler (e.g. 'gcc')
  • version() returns the compiler's version number as a string
  • find_library(lib_name, ...) tries to find the library specified in the positional argument. The result object can be used just like the return value of dependency. If the keyword argument required is false, Meson will proceed even if the library is not found. By default the library is searched for in the system library directory (e.g. /usr/lib). This can be overridden with the dirs keyword argument, which can be either a string or a list of strings.
  • sizeof(typename, ...) returns the size of the given type (e.g. 'int') or -1 if the type is unknown, to add includes set them in the prefix keyword argument, you can specify external dependencies to use with dependencies keyword argument
  • alignment(typename) returns the alignment of the type specified in the positional argument, you can specify external dependencies to use with dependencies keyword argument
  • compiles(code) returns true if the code fragment given in the positional argument compiles, you can specify external dependencies to use with dependencies keyword argument, code can be either a string containing source code or a file object pointing to the source code
  • links(code) returns true if the code fragment given in the positional argument compiles and links, you can specify external dependencies to use with dependencies keyword argument, code can be either a string containing source code or a file object pointing to the source code
  • run(code) attempts to compile and execute the given code fragment, returns a run result object, you can specify external dependencies to use with dependencies keyword argument, code can be either a string containing source code or a file object pointing to the source code
  • has_header returns true if the specified header can be included, you can specify external dependencies to use with dependencies keyword argument and extra code to put above the header test with the prefix keyword. In order to look for headers in a specific directory you can use args : '-I/extra/include/dir, but this should only be used in exceptional cases for includes that can't be detected via pkg-config and passed via dependencies.
  • has_type(typename) returns true if the specified token is a type, you can specify external dependencies to use with dependencies keyword argument
  • has_function(funcname) returns true if the given function is provided by the standard library or a library passed in with the args keyword, you can specify external dependencies to use with dependencies keyword argument
  • has_member(typename, membername) takes two arguments, type name and member name and returns true if the type has the specified member, you can specify external dependencies to use with dependencies keyword argument
  • has_members(typename, membername1, membername2, ...) takes at least two arguments, type name and one or more member names, returns true if the type has all the specified members, you can specify external dependencies to use with dependencies keyword argument
  • has_header_symbol(headername, symbolname) allows one to detect whether a particular symbol (function, variable, #define, type definition, etc) is declared in the specified header, you can specify external dependencies to use with dependencies keyword argument
  • has_argument(argument_name) returns true if the compiler accepts the specified command line argument, that is, can compile code without erroring out or printing a warning about an unknown flag, you can specify external dependencies to use with dependencies keyword argument
  • has_multi_arguments(arg1, arg2, arg3, ...) is the same as has_argument but takes multiple arguments and uses them all in a single compiler invocation, available since 0.37.0
  • first_supported_argument(list_of_strings), given a list of strings, returns the first argument that passes the has_argument test above or an empty array if none pass
  • symbols_have_underscore_prefix() returns true if the C symbol mangling is one underscore (_) prefixed to the symbol, available since 0.37.0
  • compute_int(expr, ...') computes the value of the given expression (as an example 1 + 2). When cross compiling this is evaluated with an iterative algorithm, you can specify keyword arguments low (defaults to -1024), high (defaults to 1024) and guess to specify max and min values for the search and the value to try first.

The following keyword arguments can be used:

  • name the name to use for printing a message about the compiler check. Supported by the methods compiles(), links(), and run(). If this kwarg is not passed to those methods, no message will be printed about the check.

  • prefix can be used to add #includes and other things that are required for the symbol to be declared. System definitions should be passed via compiler args (eg: _GNU_SOURCE is often required for some symbols to be exposed on Linux, and it should be passed via args keyword argument, see below). Supported by the methods sizeof, has_type, has_function, has_member, has_members, has_header_symbol.

  • include_directories specifies extra directories for header searches. (added 0.38.0)

  • args can be used to pass a list of compiler arguments that are required to find the header or symbol. For example, you might need to pass the include path -Isome/path/to/header if a header is not in the default include path. In versions newer than 0.38.0 you should use the include_directories keyword described above. You may also want to pass a library name -lfoo for has_function to check for a function. Supported by all methods except get_id, version, and find_library.

Note that if you have a single prefix with all your dependencies, you might find it easier to append to the environment variables C_INCLUDE_PATH with gcc/clang and INCLUDE with msvc to expand the default include path, and LIBRARY_PATH with gcc/clang and LIB with msvc to expand the default library search path.

However, with GCC, these variables will be ignored when cross-compiling. In that case you need to use a specs file. See: http://www.mingw.org/wiki/SpecsFileHOWTO

run result object

This object encapsulates the result of trying to compile and run a sample piece of code with compiler.run(). It has the following methods:

  • compiled() if true, the compilation succeeded, if false it did not and the other methods return unspecified data
  • returncode() the return code of executing the compiled binary
  • stdout() the standard out produced when the binary was run
  • stderr() the standard error produced when the binary was run

configuration data object

This object is returned by configuration_data and encapsulates configuration values to be used for generating configuration files. A more in-depth description can be found in the the configuration wiki page It has three methods:

  • set(varname, value), sets a variable to a given value
  • set10(varname, boolean_value) is the same as above but the value is either true or false and will be written as 1 or 0, respectively
  • set_quoted(varname, value) is same as set but quotes the value in double quotes (")
  • has(varname), returns true if the specified variable is set
  • get(varname, default_value) returns the value of varname, if the value has not been set returns default_value if it is defined (added 0.38.0) and errors out if not

They all take the description keyword that will be written in the result file. The replacement assumes a file with C syntax. If your generated file is source code in some other language, you probably don't want to add a description field because it most likely will cause a syntax error.

dependency object

This object is returned by dependency and contains an external dependency with the following methods:

  • found() which returns whether the dependency was found
  • type_name() which returns a string describing the type of the dependency, the most common values are internal for deps created with declare_dependencies and pkgconfig for system dependencies obtained with Pkg-config.
  • version() is the version number as a string, for example 1.2.8
  • get_pkgconfig_variable(varname) (Added 0.36.0) will get the pkg-config variable specified, or, if invoked on a non pkg-config dependency, error out

external program object

This object is returned by find_program and contains an external (i.e. not built as part of this project) program and has the following methods:

  • found() which returns whether the executable was found
  • path() which returns an array pointing to the executable (this is an array as opposed to a string because the program might be ['python', 'foo.py'], for example)

environment object

This object is returned by environment and stores detailed information about how environment variables should be set during tests. It should be passed as the env keyword argument to tests. It has the following methods.

  • set(varname, value) sets environment variable in the first argument to the value in the second argument, e.g. env.set('FOO', 'BAR') sets envvar FOOto valueBAR`
  • append(varname, value) appends the given value to the old value of the environment variable, e.g. env.append'('FOO', 'BAR', separator : ';') produces BOB;BAR if FOO had the value BOB and plain BAR if the value was not defined. If the separator is not specified explicitly, the default path separator for the host operating system will be used, i.e. ';' for Windows and ':' for UNIX/POSIX systems.
  • prepend(varname, value) is the same as append except that it writes to the beginning of the variable

external library object

This object is returned by find_library and contains an external (i.e. not built as part of this project) library. This object has only one method, found, which returns whether the library was found.

generator object

This object is returned by generator and contains a generator that is used to transform files from one type to another by an executable (e.g. idl files into source code and headers).

  • process(list_of_files) takes a list of files, causes them to be processed and returns an object containing the result which can then, for example, be passed into a build target definition. The keyword argument extra_args, if specified, will be used to replace an entry @EXTRA_ARGS@ in the argument list.

subproject object

This object is returned by subproject and is an opaque object representing it.

  • get_variable(name) fetches the specified variable from inside the subproject. This is useful to, for instance, get a declared dependency from the subproject.

string object

All strings have the following methods. Strings are immutable, all operations return their results as a new string.

  • strip() removes whitespace at the beginning and end of the string
  • format() formats text, see the Syntax manual for usage info
  • to_upper() creates an upper case version of the string
  • to_lower() creates a lower case version of the string
  • underscorify() creates a string where every non-alphabetical non-number character is replaced with _
  • split(split_character) splits the string at the specified character (or whitespace if not set) and returns the parts in an array
  • startswith(string) returns true if string starts with the string specified as the argument
  • endswith(string) returns true if string ends with the string specified as the argument
  • contains(string) returns true if string contains the string specified as the argument
  • to_int returns the string converted to an integer (error if string is not a number)
  • join(list_of_strings) is the opposite of split, for example '.'.join(['a', 'b', 'c'] yields 'a.b.c'
  • version_compare(comparison_string) does semantic version comparison, if x = '1.2.3' then x.version_compare('>1.0.0') returns true

Number object

Numbers support these methods:

  • is_even() returns true if the number is even
  • is_odd() returns true if the number is odd

boolean object

A boolean object has two simple methods:

  • to_string() returns the string 'true' if the boolean is true or 'false' otherwise. You can also pass it two strings as positional arguments to specify what to return for true/false. For instance, bool.to_string('yes', 'no') will return yes if the boolean is true and no if it is false.
  • to_int() as above, but returns either 1 or 0

array object

The following methods are defined for all arrays:

  • length(), the size of the array
  • contains(item), returns true if the array contains the object given as argument, false otherwise
  • get(index, fallback), returns the object at the given index, negative indices count from the back of the array, indexing out of bounds returns the fallback value (added 0.38.0) or, if it is not specified, causes a fatal error

You can also iterate over arrays with the foreach statement.

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