Reference-manual.md

Reference manual

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.

add_global_arguments()

  void add_global_arguments(arg1, arg2, ...)

Adds the positional arguments to the compiler command line. This function has two keyword arguments:

• language specifies the language(s) that the arguments should be applied to. If a list of languages is given, the arguments are added to each of the corresponding compiler command lines. 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.

• native is a boolean specifying whether the arguments should be applied to the native or cross compilation. If true the arguments will only be used for native compilations. If false the arguments will only be used in cross compilations. If omitted, the flags are added to native compilations if compiling natively and cross compilations (only) when cross compiling. Available since 0.48.0

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()

  bool 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
if add_languages('cpp', required : false)
  executable('cpp-app', 'main.cpp')
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. Since 0.47.0 the value of a feature option can also be passed to the required keyword argument.

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:

• env an environment object to use a custom environment
• 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
• is_default a bool to set whether this is the default test setup. If true, the setup will be used whenever meson test is run without the --setup option. Since 0.49.0

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

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

alias_target

runtarget alias_target(target_name, dep1, ...)

Since 0.52.0

This function creates a new top-level target. Like all top-level targets, this integrates with the selected backend. For instance, with Ninja you can run it as ninja target_name. This is a dummy target that does not execute any command, but ensures that all dependencies are built. Dependencies can be any build target (e.g. return value of executable(), custom_target(), etc)

assert()

    void assert(*condition*, *message*)

Abort with an error message if condition evaluates to false.

benchmark()

    void benchmark(name, executable, ...)

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

both_libraries()

    buildtarget = both_libraries(library_name, list_of_sources, ...)

Builds both a static and shared library with the given sources. Positional and keyword arguments are otherwise the same as for library. Source files will be compiled only once and object files will be reused to build both shared and static libraries, unless b_staticpic user option or pic argument are set to false in which case sources will be compiled twice.

The returned buildtarget always represents the shared library. In addition it supports the following extra methods:

• get_shared_lib() returns the shared library build target
• get_static_lib() returns the static library build target

Added 0.46.0

build_target()

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

target_type may be set to one of:

• executable
• shared_library
• shared_module
• static_library
• both_libraries
• library
• jar

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.

Since 0.49.0 takes an optional dictionary as first argument. If provided, each key/value pair is added into the configuration_data as if set() method was called for each of them.

configure_file()

    generated_file = configure_file(...)

This function can run in three 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. Since 0.49.0 a dictionary can be passed instead of a configuration_data() object.

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.

Since 0.47.0, when the copy: keyword argument is set to true, this function will copy the file provided in input: to a file in the build directory with the name output: in the current directory.

These are all the supported keyword arguments:

• capture when this argument is set to true, Meson captures stdout of the command and writes it to the target file specified as output. Available since v0.41.0.
• 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. Since 0.52.0 the command can contain file objects and more than one file can be passed to the input keyword argument, see custom_target() for details about string substitutions.
• copy (added 0.47.0) as explained above, if specified Meson only copies the file from input to output.
• format (added 0.46.0) the format of defines. It defaults to meson, and so substitutes #mesondefine statements and variables surrounded by @ characters, you can also use cmake to replace #cmakedefine statements and variables with the ${variable} syntax. Finally you can use cmake@ in which case substitutions will apply on #cmakedefine statements and variables with the @variable@ syntax.
• 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.
• install (added 0.50.0) When true, this generated file is installed during the install step, and install_dir must be set and not empty. When false, this generated file is not installed regardless of the value of install_dir. When omitted it defaults to true when install_dir is set and not empty, false otherwise.
• install_dir the subdirectory to install the generated file to (e.g. share/myproject), if omitted or given the value of empty string, the file is not installed.
• install_mode (added 0.47.0) specify the file mode in symbolic format and optionally the owner/uid and group/gid for the installed files.
• output the output file name (since v0.41.0, may contain @PLAINNAME@ or @BASENAME@ substitutions). In configuration mode, the permissions of the input file (if it is specified) are copied to the output file.
• output_format (added 0.47.0) the format of the output to generate when no input was specified. It defaults to c, in which case preprocessor directives will be prefixed with #, you can also use nasm, in which case the prefix will be %.
• encoding (added v0.47.0) set the file encoding for the input and output file, defaults to utf-8. The supported encodings are those of python3, see standard-encodings.

custom_target()

    customtarget 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.

• build_by_default (added 0.38) causes, when set to true, to have this target be built by default, that is, when invoking plain ninja; the default value is false (changed in 0.50) if build_by_default is explicitly set to false, install will no longer override it. If build_by_default is not set, install will still determine its default.
• build_always (deprecated) if true this target is always considered out of date and is rebuilt every time. Equivalent to setting both build_always_stale and build_by_default to true.
• build_always_stale (added 0.47) if true the target is always considered out of date. Useful for things such as build timestamps or revision control tags. The associated command is run even if the outputs are up to date.
• 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.
• console (added 0.48) keyword argument conflicts with capture, and is meant for commands that are resource-intensive and take a long time to finish. With the Ninja backend, setting this will add this target to Ninja's console pool, which has special properties such as not buffering stdout and serializing all targets in this pool.
• command command to run to create outputs from inputs. The command may be strings or the return value of functions that return file-like objects such as find_program(), executable(), configure_file(), files(), custom_target(), etc. Meson will automatically insert the appropriate dependencies on targets and files listed in this keyword argument. Note: always specify commands in array form ['commandname', '-arg1', '-arg2'] rather than as a string 'commandname -arg1 -arg2' as the latter will not work.
• depend_files files (string, files(), or configure_file()) that this target depends on but are not listed in the command keyword argument. Useful for adding regen dependencies.
• 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.
• 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
• input list of source files. As of 0.41.0 the list will be flattened.
• install when true, this target is installed during the install step
• install_dir directory to install to
• install_mode (added 0.47.0) the file mode and optionally the owner/uid and group/gid
• output list of output files

The list of strings passed to the command keyword argument 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 behavior 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
• @PLAINNAME@: the input filename, without a path
• @BASENAME@: the input filename, with extension removed
• @PRIVATE_DIR@: path to a directory where the custom target must store all its intermediate files, available since 0.50.1

The depfile keyword argument also accepts the @BASENAME@ and @PLAINNAME@ substitutions. (since 0.47)

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

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 the following keyword arguments.

• compile_args, compile arguments to use
• dependencies, other dependencies needed to use this dependency
• include_directories, the directories to add to header search path, must be include_directories objects or, since 0.50.0, plain strings
• link_args, link arguments to use
• link_with, libraries to link against
• link_whole, libraries to link fully, same as executable Since 0.46.0
• sources, sources to add to targets (or generated header files that should be built before sources including them are built)
• version, the version of this dependency, such as 1.2.3

dependency()

    dependency_object dependency(*dependency_name*, ...)

Finds an external dependency (usually a library installed on your system) with the given name with pkg-config and with CMake if pkg-config fails. Additionally, frameworks (OSX only) and library-specific fallback detection logic are also supported. This function supports the following keyword arguments:

• default_options (added 0.37.0) an array of default option values that override those set in the subproject's meson_options.txt (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)
• 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 a dependency object such as the return value of declare_dependency or dependency(), etc. Note that this means the fallback dependency may be a not-found dependency, in which case the value of the required: kwarg will be obeyed.
• language (added 0.42.0) defines what language-specific dependency to find if it's available for multiple languages.
• method defines the way the dependency is detected, the default is auto but can be overridden to be e.g. qmake for Qt development, and different dependencies support different values for this (though auto will work on all of them)
• 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.
• not_found_message (added 0.50.0) is an optional string that will be printed as a message() if the dependency was not found.
• required, when set to false, Meson will proceed with the build even if the dependency is not found. Since 0.47.0 the value of a feature option can also be passed.
• 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)
• 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 keyword argument, such as: ['>=3.14.0', '<=4.1.0']. These requirements are never met if the version is unknown.
• other library-specific keywords may also be accepted (e.g. modules specifies submodules to use for dependencies such as Qt5 or Boost. )
• disabler if true and the dependency couldn't be found, return a disabler object instead of a not-found dependency. Since 0.49.0

If dependency_name is '', the dependency is always not found. So with required: false, this always returns a dependency object for which the found() method returns false, and which can be passed like any other dependency to the dependencies: keyword argument of a build_target. This can be used to implement a dependency which is sometimes not required e.g. in some branches of a conditional, or with a fallback: kwarg, can be used to declare an optional dependency that only looks in the specified subproject, and only if that's allowed by --wrap-mode.

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

disabler()

Returns a disabler object. Added in 0.44.0.

error()

    void error(message)

Print the argument string and halts the build process.

environment()

    environment_object environment()

Returns an empty environment variable object. Added in 0.35.0.

executable()

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

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

• Strings relative to the current source directory
• files() objects defined in any preceding build file
• The return value of configure-time generators such as configure_file()
• The return value of build-time generators such as custom_target() or generator.process()

These input 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 and objects (.o, .obj) and libraries (.so, .dll, etc) will be linked.

With the Ninja backend, Meson will create a build-time order-only dependency on all generated input files, including unknown files. For all input files (generated and non-generated), Meson uses the dependency file generated by your compiler to determine when to rebuild sources. The behavior is similar for other backends.

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.

• <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++
• 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
• build_rpath a string to add to target's rpath definition in the build dir, but which will be removed on install
• dependencies one or more objects created with dependency or find_library (for external deps) or declare_dependency (for deps built by the project)
• 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)
• gui_app when set to true flags this target as a GUI application on platforms where this makes a difference (e.g. Windows)
• link_args flags to use during linking. You can use UNIX-style flags here for all platforms.
• link_depends strings, files, or custom targets the link step depends on such as a symbol visibility map. The purpose is to automatically trigger a re-link (but not a re-compile) of the target when this file changes.
• link_language since 0.51.0 makes the linker for this target be for the specified language. This is helpful for multi-language targets.
• link_whole links all contents of the given static libraries whether they are used by not, equivalent to the -Wl,--whole-archive argument flag of GCC, available since 0.40.0. As of 0.41.0 if passed a list that list will be flattened. Starting from version 0.51.0 this argument also accepts outputs produced by custom targets. The user must ensure that the output is a library in the correct format.
• link_with, one or more shared or static libraries (built by this project) that this target should be linked with, If passed a list this list will be flattened as of 0.41.0. Starting with version 0.51.0, the arguments can also be custom targets. In this case Meson will assume that merely adding the output file in the linker command line is sufficient to make linking work. If this is not sufficient, then the build system writer must write all other steps manually.
• export_dynamic when set to true causes the target's symbols to be dynamically exported, allowing modules built using the shared_module function to refer to functions, variables and other symbols defined in the executable itself. Implies the implib argument. Since 0.45.0
• implib when set to true, an import library is generated for the executable (the name of the import library is based on exe_name). Alternatively, when set to a string, that gives the base name for the import library. The import library is used when the returned build target object appears in link_with: elsewhere. Only has any effect on platforms where that is meaningful (e.g. Windows). Implies the export_dynamic argument. Since 0.42.0
• implicit_include_directories is a boolean telling whether Meson adds the current source and build directories to the include path, defaults to true, since 0.42.0
• include_directories one or more objects created with the include_directories function, or, since 0.50.0, strings, which will be transparently expanded to include directory objects
• install, when set to true, this executable should be installed, defaults to false
• 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'.
• install_mode (added 0.47.0) specify the file mode in symbolic format and optionally the owner/uid and group/gid for the installed files.
• install_rpath a string to set the target's rpath to after install (but not before that)
• 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. Set this to [], or omit the keyword argument for the default behaviour.
• override_options takes an array of strings in the same format as project's default_options overriding the values of these options for this target only, since 0.40.0.
• gnu_symbol_visibility specifies how symbols should be exported, see e.g the GCC Wiki for more information. This value can either be an empty string or one of default, internal, hidden, protected or inlineshidden, which is the same as hidden but also includes things like C++ implicit constructors as specified in the GCC manual. Ignored on compilers that do not support GNU visibility arguments. Available since 0.48.0.
• d_import_dirs list of directories to look in for string imports used in the D programming language
• d_unittest, when set to true, the D modules are compiled in debug mode
• d_module_versions list of module version identifiers set when compiling D sources
• d_debug list of module debug identifiers set when compiling D sources
• pie (added 0.49.0) build a position-independent executable
• native, is a boolean controlling whether the target is compiled for the build or host machines. Defaults to false, building for the host machine.

The list of sources, objects, and dependencies is always flattened, which means you can freely nest and add lists while creating the final list.

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.

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.

Keyword arguments are the following:

• required By default, required is set to true and Meson will abort if no program can be found. If required is set to false, Meson continue even if none of the programs can be found. You can then use the .found() method on the returned object to check whether it was found or not. Since 0.47.0 the value of a feature option can also be passed to the required keyword argument.

• native (since 0.43) defines how this executable should be searched. By default it is set to false, which causes Meson to first look for the executable in the cross file (when cross building) and if it is not defined there, then from the system. If set to true, the cross file is ignored and the program is only searched from the system.

• disabler if true and the program couldn't be found, return a disabler object instead of a not-found object. Since 0.49.0

• version (since 0.52.0) Specifies the required version, see dependency() for argument format. The version of the program is determined by running program_name --version command. If stdout is empty it fallbacks to stderr. If the output contains more text than simply a version number, only the first occurence of numbers separated by dots is kept. If the output is more complicated than that, the version checking will have to be done manually using run_command().

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.

If you need to check for a program in a non-standard location, you can just pass an absolute path to find_program, e.g. setcap = find_program('setcap', '/usr/sbin/setcap', '/sbin/setcap', required : false)

It is also possible to pass an array to find_program in case you need to construct the set of paths to search on the fly:

setcap = find_program(['setcap', '/usr/sbin/setcap', '/sbin/setcap'], required : false)

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 generator(*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
• depends is an array of build targets that must be built before this generator can be run. This is used if you have a generator that calls a second executable that is built in this project. Available since 0.51.0
• 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
• 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
• capture when this argument is set to true, Meson captures stdout of the executable and writes it to the target file specified as output. Available since v0.43.0.

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

The template strings passed to all the above keyword arguments 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 output keyword argument must be constructed using one or both of these two substitutions.

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

• @OUTPUT@: the full path to the output file
• @INPUT@: the full path to the input file
• @DEPFILE@: the full path to the depfile
• @SOURCE_DIR@: the full path to the root of the source tree
• @CURRENT_SOURCE_DIR@: this is the directory where the currently processed meson.build is located in
• @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 specified in the positional argument.

Note that the value returned for built-in options that end in dir such as bindir and libdir is always a path relative to (and inside) the prefix.

The only exceptions are: sysconfdir, localstatedir, and sharedstatedir which will return the value passed during configuration as-is, which may be absolute, or relative to prefix. install_dir arguments handles that as expected, but if you need the absolute path to one of these e.g. to use in a define etc., you should use get_option('prefix') / get_option('localstatedir')

For options of type feature a special object is returned instead of a string. See feature options documentation for more details.

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 (relative to the current directory) given in the positional arguments. The result can then be passed to the include_directories: keyword argument when building executables or libraries. You can use the returned object in any subdirectory you want, Meson will make the paths work automatically.

Note that this function call itself does not add the directories into the search path, since there is no global search path. For something like that, see add_project_arguments().

See also implicit_include_directories parameter of executable(), which adds current source and build directories to include path.

Each directory given is converted to two include paths: one that is relative to the source root and one relative to the build root.

For example, with the following source tree layout in /home/user/project.git:

meson.build:

project(...)

subdir('include')
subdir('src')

...

include/meson.build:

inc = include_directories('.')

...

src/meson.build:

sources = [...]

executable('some-tool', sources,
  include_directories : inc,
  ...)

...

If the build tree is /tmp/build-tree, the following include paths will be added to the executable() call: -I/tmp/build-tree/include -I/home/user/project.git/include.

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.

  If omitted, the directory defaults to {datadir}/{projectname} (added 0.45.0).

• 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.

• rename if specified renames each source file into corresponding file from rename list. Nested paths are allowed and they are joined with install_dir. Length of rename list must be equal to the number of sources. (added 0.46.0)

See Installing for more examples.

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')

The install_mode argument can be used to specify the file mode in symbolic format and optionally the owner/uid and group/gid for the installed files. An example value could be ['rwxr-sr-x', 'root', 'root']. (Added 0.47.0).

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.

The install_mode argument can be used to specify the file mode in symbolic format and optionally the owner/uid and group/gid for the installed files. An example value could be ['rwxr-sr-x', 'root', 'root']. (Added 0.47.0).

Since 0.49.0, manpages are no longer compressed implicitly.

install_subdir()

    void install_subdir(subdir_name, install_dir : ..., exclude_files : ..., exclude_directories : ..., strip_directory : ...)

Installs the entire given subdirectory and its contents from the source tree to the location specified by the keyword argument install_dir.

The following keyword arguments are supported:

• exclude_files: a list of file names that should not be installed. Names are interpreted as paths relative to the subdir_name location.
• exclude_directories: a list of directory names that should not be installed. Names are interpreted as paths relative to the subdir_name location.
• install_dir: the location to place the installed subdirectory.
• install_mode: the file mode in symbolic format and optionally the owner/uid and group/gid for the installed files. (Added 0.47.0)
• strip_directory: install directory contents. strip_directory=false by default. If strip_directory=false only last component of source path is used. Since 0.45.0

For a given directory foo:

foo/
  bar/
    file1
  file2

install_subdir('foo', install_dir : 'share', strip_directory : false) creates

share/
  foo/
    bar/
      file1
    file2

install_subdir('foo', install_dir : 'share', strip_directory : true) creates

share/
  bar/
    file1
  file2

install_subdir('foo/bar', install_dir : 'share', strip_directory : false) creates

share/
  bar/
    file1

install_subdir('foo/bar', install_dir : 'share', strip_directory : true) creates

share/
  file1

is_disabler()

    bool is_disabler(var)

Returns true if a variable is a disabler and false otherwise. Added in 0.52.0.

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.

Warning Don't use join_paths() for sources in library and executable, you should use files instead.

Added 0.36.0

Since 0.49.0 using the/ operator on strings is equivalent to calling join_paths.

# res1 and res2 will have identical values
res1 = join_paths(foo, bar)
res2 = foo / bar

library()

    buildtarget library(library_name, list_of_sources, ...)

Builds a library that is either static, shared or both depending on the value of default_library user option. You should use this instead of shared_library, static_library or both_libraries 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 additions:

• name_prefix the string that will be used as the prefix for the target output filename by overriding the default (only used for libraries). By default this is lib on all platforms and compilers except with MSVC shared libraries where it is omitted to follow convention.
• name_suffix the string that will be used as the suffix for the target output filename by overriding the default (see also: executable()). By default, for shared libraries this is dylib on macOS, dll on Windows, and so everywhere else. For static libraries, it is a everywhere. By convention MSVC static libraries use the lib suffix, but we use a to avoid a potential name clash with shared libraries which also generate xxx.lib import files.
• rust_crate_type specifies the crate type for Rust libraries. Defaults to dylib for shared libraries and rlib for static libraries.

static_library, shared_library and both_libraries also accept these keyword arguments.

Note: You can set name_prefix and name_suffix to [], or omit them for the default behaviour for each platform.

message()

    void message(text)

This function prints its argument to stdout.

warning()

    void warning(text)

This function prints its argument to stdout prefixed with WARNING:.

Added 0.44.0

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 is followed by programming languages that the project uses. Supported values for languages are c, cpp (for C++), d, objc, objcpp, fortran, java, cs (for C#), vala and rust. In versions before 0.40.0 you must have at least one language listed.

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.

• default_options takes an array of strings. The strings are in the form key=value and have the same format as options to meson configure. 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.

• license takes a string or array of strings describing the license(s) the code is under. 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. You can access the value in your Meson build files with meson.project_license().

• meson_version takes a string describing which Meson version the project requires. Usually something like >=0.28.0.

• 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.

• 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().

run_command()

    runresult run_command(command, list_of_args, ...)

Runs the command specified in positional arguments. command can be a string, or the output of find_program(), files() or configure_file(), or a compiler object.

Returns an opaque object containing the result of the invocation. The command 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.

This function supports the following keyword arguments:

• check takes a boolean. If true, the exit status code of the command will be checked, and the configuration will fail if it is non-zero. The default is false. Since 0.47.0
• env an environment object to use a custom environment Since 0.50.0

See also External commands.

run_target

runtarget 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. Note that a run target produces no output as far as Meson is concerned. It is only meant for tasks such as running a code formatter or flashing an external device's firmware with a built file.

The command 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.

Note: Prior to v0.46.1, the value parameter could not be an array type, due to flattening of the function parameters.

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.

• 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 (see below). For example, if version is 3.6.0 and soversion is not defined, it is set to 3.
• 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 above).
• darwin_versions (added 0.48) an integer, string, or a list of versions to use for setting dylib compatibility version and current version on macOS. If a list is specified, it must be either zero, one, or two elements. If only one element is specified or if it's not a list, the specified value will be used for setting both compatibility version and current version. If unspecified, the soversion will be used as per the aforementioned rules.
• vs_module_defs a string, a File object, or Custom Target for a Microsoft module definition file for controlling symbol exports, etc., on platforms where that is possible (e.g. Windows).

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.

If you want the shared module to be able to refer to functions and variables defined in the executable it is loaded by, you will need to set the export_dynamic argument of the executable to true.

Supports the following extra keyword arguments:

• vs_module_defs, (Added 0.52.0), a string, a File object, or Custom Target for a Microsoft module definition file for controlling symbol exports, etc., on platforms where that is possible (e.g. Windows).

Note: Linking to a shared module is not supported on some platforms, notably OSX. Consider using a shared_library instead, if you need to both dlopen() and link with a library.

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.

This function has one keyword argument.

• if_found takes one or several dependency objects and will only recurse in the subdir if they all return true when queried with .found()

subdir_done()

    subdir_done()

Stops further interpretation of the meson script file from the point of the invocation. All steps executed up to this point are valid and will be executed by meson. This means that all targets defined before the call of subdir_done will be build.

If the current script was called by subdir the execution returns to the calling directory and continues as if the script had reached the end. If the current script is the top level script meson configures the project as defined up to this point.

Example:

project('example exit', 'cpp')
executable('exe1', 'exe1.cpp')
subdir_done()
executable('exe2', 'exe2.cpp')

The executable exe1 will be build, while the executable exe2 is not build.

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:

• default_options (added 0.37.0) an array of default option values that override those set in the subproject's meson_options.txt (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)
• 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
• required (added 0.48.0) By default, required is true and Meson will abort if the subproject could not be setup. You can set this to false and then use the .found() method on the returned object. You may also pass the value of a feature option, same as dependency().

Note that you can use the returned subproject object to access any variable in the subproject. However, if you want to use a dependency object from inside a subproject, an easier way is to use the fallback: keyword argument to dependency().

See additional documentation.

test()

    void test(name, executable, ...)

Defines a test to run with the test harness. Takes two positional arguments, the first is the name of the test and the second is the executable to run. The executable can be an executable build target object returned by executable() or an external program object returned by find_program().

Keyword arguments are the following:

• args arguments to pass to the executable

• env environment variables to set, such as ['NAME1=value1', 'NAME2=value2'], or an environment() object which allows more sophisticated environment juggling

• 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)

• suite 'label' (or list of labels ['label1', 'label2']) attached to this test. The suite name is qualified by a (sub)project name resulting in (sub)project_name:label. In the case of a list of strings, the suite names will be (sub)project_name:label1, (sub)project_name:label2, etc.

• 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

• depends specifies that this test 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 test finds those targets internally, e.g. plugins or globbing. Those targets are built before test is executed even if they have build_by_default : false. Since 0.46.0

• protocol specifies how the test results are parsed and can be one of exitcode (the executable's exit code is used by the test harness to record the outcome of the test) or tap (Test Anything Protocol). For more on the Meson test harness protocol read Unit Tests. Since 0.50.0

• priority specifies the priority of a test. Tests with a higher priority are started before tests with a lower priority. The starting order of tests with identical priorities is implementation-defined. The default priority is 0, negative numbers are permitted. Since 0.52.0

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

vcs_tag()

    customtarget 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.

• command string list with the command to execute, see custom_target for details on how this command must be specified
• fallback version number to use when no revision control information is present, such as when building from a release tarball (defaults to meson.project_version())
• input file to modify (e.g. version.c.in) (required)
• output file to write the results to (e.g. version.c) (required)
• replace_string string in the input file to substitute with the commit information (defaults to @VCS_TAG@)

Meson will read the contents of input, substitute the replace_string with the detected revision number, and write the result to output. This method returns a custom_target object that (as usual) should be used to signal dependencies if other targets use the file outputted by this.

For example, if you generate a header with this and want to use that in a build target, you must add the return value to the sources of that build target. Without that, Meson will not know the order in which to build the targets.

If you desire more specific behavior than what this command provides, you should use custom_target.

Built-in objects

These are built-in objects that are always available.

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.

• add_dist_script(script_name, arg1, arg, ...) causes the script given as argument to run during dist operation after the distribution source has been generated but before it is archived. Note that this runs the script file that is in the staging directory, not the one in the source directory. If the script file can not be found in the staging directory, it is a hard error. This command can only invoked from the main project, calling it from a subproject is a hard error. Available since 0.48.0. Before 0.49.0, the function only accepted a single argument.

• 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, MESON_INSTALL_DESTDIR_PREFIX, and MESONINTROSPECT set. All additional arguments are passed as parameters.

  Meson uses the DESTDIR environment variable as set by the inherited environment to determine the (temporary) installation location for files. Your install script must be aware of this while manipulating and installing files. The correct way to handle this is with the MESON_INSTALL_DESTDIR_PREFIX variable which is always set and contains DESTDIR (if set) and prefix joined together. This is useful because both are usually absolute paths and there are platform-specific edge-cases in joining two absolute paths.

  In case it is needed, MESON_INSTALL_PREFIX is also always set and has the value of the prefix option passed to Meson.

  MESONINTROSPECT contains the path to the introspect command that corresponds to the meson executable that was used to configure the build. (This might be a different path then the first executable found in PATH.) It can be used to query build configuration. Note that the value will contain many parts, f.ex., it may be python3 /path/to/meson.py introspect. The user is responsible for splitting the string to an array if needed by splitting lexically like a UNIX shell would. If your script uses Python, shlex.split() is the easiest correct way to do this.

• 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.

• backend() (added 0.37.0) returns a string representing the current backend: ninja, vs2010, vs2015, vs2017, vs2019, or xcode.

• build_root() returns a string with the absolute path to the build root directory. Note: this function will return the build root of the parent project if called from a subproject, which is usually not what you want. Try using current_build_dir().

• 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(). This function will return the source root of the parent project if called from a subproject, which is usually not what you want. Try using current_source_dir().

• current_build_dir() returns a string with the absolute path to the current build directory.

• 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().

• 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.

• 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.

• 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).

• 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.

• is_cross_build() returns true if the current build is a cross 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.

• is_unity() returns true when doing a unity build (multiple sources are combined before compilation to reduce build time) and false otherwise.

• override_find_program(progname, program) (Added 0.46.0) specifies that whenever find_program is used to find a program named progname, Meson should not not look it up on the system but instead return program, which may either be the result of find_program, configure_file or executable.

  If program is an executable, it cannot be used during configure.

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

• project_license() returns the array of licenses 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.

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. This table contains all known CPU families. These are guaranteed to continue working.

• cpu() returns a more specific CPU name, such as i686, amd64, etc.

• system() returns the operating system name. This table Lists all of the currently known Operating System names, these are guaranteed to continue working.

• endian() returns big on big-endian systems and little on little-endian systems.

Currently, these values are populated using platform.system() and platform.machine(). If you think the returned values for any of these are incorrect for your system or CPU, or if your OS is not in the linked table, please file a bug report with details and we'll look into it.

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.

When not cross-compiling, all the methods return the same values as build_machine (because the build machine is the host machine)

Note that while cross-compiling, 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.

When all compilation is 'native', all the methods return the same values as build_machine (because the build machine is the host machine and the target machine).

Note that while cross-compiling, 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.

string object

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

• contains(string) returns true if string contains the string specified as the argument

• endswith(string) returns true if string ends with the string specified as the argument

• format() formats text, see the Syntax manual for usage info

• join(list_of_strings) is the opposite of split, for example '.'.join(['a', 'b', 'c'] yields 'a.b.c'

• 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

• strip() removes whitespace at the beginning and end of the string (added 0.43.0) optionally can take one positional string argument, and all characters in that string will be stripped

• to_int returns the string converted to an integer (error if string is not a number)

• to_lower() creates a lower case version of the string

• to_upper() creates an upper case version of the string

• underscorify() creates a string where every non-alphabetical non-number character is replaced with _

• 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
• to_string() returns the value of the number as a string.

boolean object

A boolean object has two simple methods:

• to_int() as above, but returns either 1 or 0

• 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.

array object

The following methods are defined for all arrays:

• 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

• length(), the size of the array

You can also iterate over arrays with the foreach statement.

dictionary object

The following methods are defined for all dictionaries:

• has_key(key) returns true if the dictionary contains the key given as argument, false otherwise

• get(key, fallback), returns the value for the key given as first argument if it is present in the dictionary, or the optional fallback value given as the second argument. If a single argument was given and the key was not found, causes a fatal error

You can also iterate over dictionaries with the foreach statement.

Dictionaries are available since 0.47.0.

Since 0.48.0 dictionaries can be added (e.g. d1 = d2 + d3 and d1 += d2). Values from the second dictionary overrides values from the first.

Returned objects

These are objects returned by the functions listed above.

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:

• alignment(typename) returns the alignment of the type specified in the positional argument, you can specify external dependencies to use with dependencies keyword argument.

• cmd_array() returns an array containing the command arguments for the current compiler.

• 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.

• 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.

• 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. Since 0.47.0 the value of a feature option can also be passed to the required keyword argument. Since 0.49.0 if the keyword argument disabler is true and the dependency couldn't be found, return a disabler object instead of a not-found dependency. Since 0.50.0 the has_headers keyword argument can be a list of header files that must be found as well, using has_header() method. All keyword arguments prefixed with header_ will be passed down to has_header() method with the prefix removed. Since 0.51.0 the static keyword (boolean) can be set to true to limit the search to static libraries and false for dynamic/shared.

• first_supported_argument(list_of_strings), given a list of strings, returns the first argument that passes the has_argument test or an empty array if none pass.

• first_supported_link_argument(list_of_strings) (added 0.46.0), given a list of strings, returns the first argument that passes the has_link_argument test or an empty array if none pass.

• get_define(definename) returns the given preprocessor symbol's value as a string or empty string if it is not defined. Starting with 0.47.0, this method will concatenate string literals as the compiler would. E.g. "a" "b" will become "ab".

• get_id() returns a string identifying the compiler. For example, gcc, msvc, and more.

• get_argument_syntax() (new in 0.49.0) returns a string identifying the type of arguments the compiler takes. Can be one of gcc, msvc, or an undefined string value. This method is useful for identifying compilers that are not gcc or msvc, but use the same argument syntax as one of those two compilers such as clang or icc, especially when they use different syntax on different operating systems.

• get_supported_arguments(list_of_string) (added 0.43.0) returns an array containing only the arguments supported by the compiler, as if has_argument were called on them individually.

• get_supported_link_arguments(list_of_string) (added 0.46.0) returns an array containing only the arguments supported by the linker, as if has_link_argument were called on them individually.

• 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.

• has_link_argument(argument_name) (added 0.46.0) returns true if the linker accepts the specified command line argument, that is, can compile and link code without erroring out or printing a warning about an unknown flag. Link arguments will be passed to the compiler, so should usually have the -Wl, prefix. On VisualStudio a /link argument will be prepended.

• 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.

• check_header (added 0.47.0) returns true if the specified header is usable with the specified prefix, dependencies, and arguments. 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. Since 0.50.0 the required keyword argument can be used to abort if the header cannot be found.

• has_header returns true if the specified header exists, and is faster than check_header() since it only does a pre-processor check. 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. Since 0.50.0 the required keyword argument can be used to abort if the header cannot be found.

• 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. Since 0.50.0 the required keyword argument can be used to abort if the symbol cannot be found.

• 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_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.

• has_multi_link_arguments(arg1, arg2, arg3, ...) (added 0.46.0) is the same as has_link_argument but takes multiple arguments and uses them all in a single compiler invocation.

• has_type(typename) returns true if the specified token is a type, you can specify external dependencies to use with dependencies keyword argument.

• 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.

• symbols_have_underscore_prefix() returns true if the C symbol mangling is one underscore (_) prefixed to the symbol, available since 0.37.0.

• 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.

• version() returns the compiler's version number as a string.

• has_function_attribute(name) (added in 0.48.0) returns true if the compiler supports the GNU style (__attribute__(...)) name. This is preferable to manual compile checks as it may be optimized for compilers that do not support such attributes. This table lists all of the supported attributes.

• get_supported_function_attributes(list_of_names) (added in 0.48.0) returns an array containing any names that are supported GCC style attributes. Equivalent to has_function_attribute was called on each of them individually.

The following keyword arguments can be used:

• 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 below. 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.

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

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

• no_builtin_args when set to true, the compiler arguments controlled by built-in configuration options are not added.

• 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, check_header, has_header, has_header_symbol.

Note: These compiler checks do not use compiler arguments added with add_*_arguments(), via -Dlang_args on the command-line, or through CFLAGS/LDFLAGS, etc in the environment. Hence, you can trust that the tests will be fully self-contained, and won't fail because of custom flags added by other parts of the build file or by users.

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

build target object

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

• extract_all_objects() is same as extract_objects but returns all object files generated by this target. Since 0.46.0 keyword argument recursive must be set to true to also return objects passed to the object argument of this target. By default only objects built for this target are returned to maintain backward compatibility with previous versions. The default will eventually be changed to true in a future version.

• extract_objects(source1, source2, ...) takes as its arguments a number of source files as string or files() and returns an opaque value representing the object files generated for those source files. This is typically 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.

• full_path() returns a full path pointing to the result target file. NOTE: In most cases using the object itself will do the same job as this and will also allow Meson to setup inter-target dependencies correctly. Please file a bug if that doesn't work for you.

• 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

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:

• 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

• get_unquoted(varname, default_value) returns the value of varname but without surrounding double quotes ("). If the value has not been set returns default_value if it is defined and errors out if not. Available since 0.44.0

• has(varname), returns true if the specified variable is set

• merge_from(other) takes as argument a different configuration data object and copies all entries from that object to the current object, available since 0.42.0

• 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 (")

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.

custom target object

This object is returned by custom_target and contains a target with the following methods:

• full_path() returns a full path pointing to the result target file NOTE: In most cases using the object itself will do the same job as this and will also allow Meson to setup inter-target dependencies correctly. Please file a bug if that doesn't work for you.

• [index] returns an opaque object that references this target, and can be used as a source in other targets. When it is used as such it will make that target depend on this custom target, but the only source added will be the one that corresponds to the index of the custom target's output argument.

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

• name() (Added 0.48.0) returns the name of the dependency that was searched. Returns internal for dependencies created with declare_dependency().

• 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. (Added 0.44.0) You can also redefine a variable by passing a list to the define_variable parameter that can affect the retrieved variable: ['prefix', '/']). (Added 0.45.0) A warning is issued if the variable is not defined, unless a default parameter is specified.

• get_configtool_variable(varname) (Added 0.44.0) will get the command line argument from the config tool (with -- prepended), or, if invoked on a non config-tool dependency, error out.

• type_name() which returns a string describing the type of the dependency, the most common values are internal for deps created with declare_dependency() and pkgconfig for system dependencies obtained with Pkg-config.

• version() is the version number as a string, for example 1.2.8. unknown if the dependency provider doesn't support determining the version.

• partial_dependency(compile_args : false, link_args : false, links : false, includes : false, source : false) (Added 0.46.0) returns a new dependency object with the same name, version, found status, type name, and methods as the object that called it. This new object will only inherit other attributes from its parent as controlled by keyword arguments.

  If the parent has any dependencies, those will be applied to the new partial dependency with the same rules. So , given:

  dep1 = declare_dependency(compile_args : '-Werror=foo', link_with : 'libfoo')
  dep2 = declare_dependency(compile_args : '-Werror=bar', dependencies : dep1)
  dep3 = dep2.partial_dependency(compile_args : true)

  dep3 will add ['-Werror=foo', '-Werror=bar'] to the compiler args of any target it is added to, but libfoo will not be added to the link_args.

  Note: A bug present until 0.50.1 results in the above behavior not working correctly.

  The following arguments will add the following attributes:

  • compile_args: any arguments passed to the compiler
  • link_args: any arguments passed to the linker
  • links: anything passed via link_with or link_whole
  • includes: any include_directories
  • sources: any compiled or static sources the dependency has

• get_variable(cmake : str, pkgconfig : str, configtool : str, default_value : str, pkgconfig_define : [str, str]) (Added in 0.51.0) A generic variable getter method, which repalces the get_type_variable methods. This allows one to get the variable from a dependency without knowing specifically how that dependency was found. If default_value is set and the value cannot be gotten from the object then default_value is returned, if it is not set then an error is raised.

disabler object

A disabler object is an object that behaves in much the same way as NaN numbers do in floating point math. That is when used in any statement (function call, logical op, etc) they will cause the statement evaluation to immediately short circuit to return a disabler object. A disabler object has one method:

• found(), always returns false

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 a string pointing to the script or executable NOTE: You should not need to use this method. Passing the object itself should work in all cases. For example: run_command(obj, arg1, arg2)

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 and other functions. It has the following methods.

• append(varname, value1, value2, ...) appends the given values to the old value of the environment variable, e.g. env.append('FOO', 'BAR', 'BAZ', separator : ';') produces BOB;BAR;BAZ if FOO had the value BOB and plain BAR;BAZ 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, value1, value2, ...) is the same as append except that it writes to the beginning of the variable

• set(varname, value1, value2) sets the environment variable specified in the first argument to the values in the second argument joined by the separator, e.g. env.set('FOO', 'BAR'), sets envvar FOO to value BAR. See append() above for how separators work.

Note: All these methods overwrite the previously-defined value(s) if called twice with the same varname.

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 the following methods:

• found() which returns whether the library was found.

• type_name() (added 0.48.0) which returns a string describing the type of the dependency, which will be library in this case.

• partial_dependency(compile_args : false, link_args : false, links : false, includes : false, source : false) (Added 0.46.0) returns a new dependency object with the same name, version, found status, type name, and methods as the object that called it. This new object will only inherit other attributes from its parent as controlled by keyword arguments.

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. The keyword argument preserve_path_from, if given, specifies that the output files need to maintain their directory structure inside the target temporary directory. The most common value for this is meson.current_source_dir(). With this value when a file called subdir/one.input is processed it generates a file <target private directory>/subdir/one.out as opposed to <target private directory>/one.out.

subproject object

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

• found() (added 0.48.0) which returns whether the subproject was successfully setup

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

  If the variable does not exist, the variable fallback is returned. If a fallback is not specified, then attempting to read a non-existing variable will cause a fatal error.

run result object

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

• compiled() if true, the compilation succeeded, if false it did not and the other methods return unspecified data. This is only available for compiler.run() results.
• returncode() the return code of executing the compiled binary
• stderr() the standard error produced when the command was run
• stdout() the standard out produced when the command was run