short-description: Built-in options to configure project properties ...
Meson provides two kinds of options: build options provided by the build files and built-in options that are either universal options, base options, compiler options.
All these can be set by passing -Doption=value to meson (aka meson setup), or by setting them inside default_options of [[project]] in your meson.build. Some options can also be set by --option=value, or --option value -- a list is shown by running meson setup --help.
For legacy reasons --warnlevel is the cli argument for the warning_level option.
They can also be edited after setup using meson configure -Doption=value.
Installation options are usually relative to the prefix but it should not be relied on, since they can be absolute paths in the following cases:
/usr: sysconfdir defaults to /etc, localstatedir defaults to /var, and sharedstatedir defaults to /var/lib/usr/local: localstatedir defaults to /var/local, and sharedstatedir defaults to /var/local/lib| Option | Default value | Description |
|---|---|---|
| prefix | see below | Installation prefix |
| bindir | bin | Executable directory |
| datadir | share | Data file directory |
| includedir | include | Header file directory |
| infodir | share/info | Info page directory |
| libdir | see below | Library directory |
| licensedir | see below | Licenses directory (since 1.1.0) |
| libexecdir | libexec | Library executable directory |
| localedir | share/locale | Locale data directory |
| localstatedir | var | Localstate data directory |
| mandir | share/man | Manual page directory |
| sbindir | sbin | System executable directory |
| sharedstatedir | com | Architecture-independent data directory |
| sysconfdir | etc | Sysconf data directory |
prefix defaults to C:/ on Windows, and /usr/local otherwise. You should always override this value.
libdir is automatically detected based on your platform, it should be correct when doing “native” (build machine == host machine) compilation. For cross compiles Meson will try to guess the correct libdir, but it may not be accurate, especially on Linux where different distributions have different defaults. Using a cross file, particularly the paths section may be necessary.
licensedir is empty by default. If set, it defines the default location to install a dependency manifest and project licenses. For more details, see [[meson.install_dependency_manifest]].
Options that are labeled “per machine” in the table are set per machine. See the specifying options per machine section for details.
| Option | Default value | Description | Is per machine | Is per subproject |
|---|---|---|---|---|
| auto_features {enabled, disabled, auto} | auto | Override value of all ‘auto’ features | no | no |
| backend {ninja, vs, vs2010, vs2012, vs2013, vs2015, vs2017, vs2019, vs2022, xcode, none} | ninja | Backend to use | no | no |
| genvslite {vs2022} | vs2022 | Setup multi-builtype ninja build directories and Visual Studio solution | no | no |
| buildtype {plain, debug, debugoptimized, release, minsize, custom} | debug | Build type to use | no | no |
| debug | true | Enable debug symbols and other information | no | no |
| default_library {shared, static, both} | shared | Default library type | no | yes |
| errorlogs | true | Whether to print the logs from failing tests. | no | no |
| install_umask {preserve, 0000-0777} | 022 | Default umask to apply on permissions of installed files | no | no |
| layout {mirror,flat} | mirror | Build directory layout | no | no |
| optimization {plain, 0, g, 1, 2, 3, s} | 0 | Optimization level | no | no |
| pkg_config_path {OS separated path} | '' | Additional paths for pkg-config to search before builtin paths | yes | no |
| prefer_static | false | Whether to try static linking before shared linking | no | no |
| cmake_prefix_path | [] | Additional prefixes for cmake to search before builtin paths | yes | no |
| stdsplit | true | Split stdout and stderr in test logs | no | no |
| strip | false | Strip targets on install | no | no |
| unity {on, off, subprojects} | off | Unity build | no | no |
| unity_size {>=2} | 4 | Unity file block size | no | no |
| warning_level {0, 1, 2, 3, everything} | 1 | Set the warning level. From 0 = compiler default to everything = highest | no | yes |
| werror | false | Treat warnings as errors | no | yes |
| wrap_mode {default, nofallback, nodownload, forcefallback, nopromote} | default | Wrap mode to use | no | no |
| force_fallback_for | [] | Force fallback for those dependencies | no | no |
| vsenv | false | Activate Visual Studio environment | no | no |
backendSeveral build file formats are supported as command runners to build the configured project. Meson prefers ninja by default, but platform-specific backends are also available for better IDE integration with native tooling: Visual Studio for Windows, and xcode for macOS. It is also possible to configure with no backend at all, which is an error if you have targets to build, but for projects that need configuration + testing + installation allows for a lighter automated build pipeline.
genvsliteSetup multiple buildtype-suffixed, ninja-backend build directories (e.g. [builddir]_[debug/release/etc.]) and generate [builddir]_vs containing a Visual Studio solution with multiple configurations that invoke a meson compile of the setup build directories, as appropriate for the current configuration (builtype).
This has the effect of a simple setup macro of multiple ‘meson setup ...’ invocations with a set of different buildtype values. E.g. meson setup ... --genvslite vs2022 somebuilddir does the following -
meson setup ... --backend ninja --buildtype debug somebuilddir_debug meson setup ... --backend ninja --buildtype debugoptimized somebuilddir_debugoptimized meson setup ... --backend ninja --buildtype release somebuilddir_release
and additionally creates another ‘somebuilddir_vs’ directory that contains a generated multi-configuration visual studio solution and project(s) that are set to build/compile with the somebuilddir_[...] that‘s appropriate for the solution’s selected buildtype configuration.
buildtype For setting optimization levels and toggling debug, you can either set the buildtype option, or you can set the optimization and debug options which give finer control over the same. Whichever you decide to use, the other will be deduced from it. For example, -Dbuildtype=debugoptimized is the same as -Ddebug=true -Doptimization=2 and vice-versa. This table documents the two-way mapping:
| buildtype | debug | optimization |
|---|---|---|
| plain | false | plain |
| debug | true | 0 |
| debugoptimized | true | 2 |
| release | false | 3 |
| minsize | true | s |
All other combinations of debug and optimization set buildtype to 'custom'.
warning_levelExact flags per warning level is compiler specific, but there is an approximative table for most common compilers.
| Warning level | GCC/Clang | MSVC |
|---|---|---|
| 0 | ||
| 1 | -Wall | /W2 |
| 2 | -Wall -Wextra | /W3 |
| 3 | -Wall -Wextra -Wpedantic | /W4 |
| everything | -Weverything | /Wall |
Clang's -Weverything is emulated on GCC by passing all known warning flags.
vsenvThe --vsenv argument is supported since 0.60.0, -Dvsenv=true syntax is supported since 1.1.0.
Since 0.59.0, meson automatically activates a Visual Studio environment on Windows for all its subcommands, but only if no other compilers (e.g. gcc or clang) are found, and silently continues if Visual Studio activation fails.
Setting the vsenv option to true forces Visual Studio activation even when other compilers are found. It also make Meson abort with an error message when activation fails.
vsenv is true by default when using the vs backend.
These are set in the same way as universal options, either by -Doption=value, or by setting them inside default_options of [[project]] in your meson.build. However, they cannot be shown in the output of meson setup --help because they depend on both the current platform and the compiler that will be selected. The only way to see them is to setup a builddir and then run meson configure on it with no options.
The following options are available. Note that they may not be available on all platforms or with all compilers:
| Option | Default value | Possible values | Description |
|---|---|---|---|
| b_asneeded | true | true, false | Use -Wl,--as-needed when linking |
| b_bitcode | false | true, false | Embed Apple bitcode, see below |
| b_colorout | always | auto, always, never | Use colored output |
| b_coverage | false | true, false | Enable coverage tracking |
| b_lundef | true | true, false | Don't allow undefined symbols when linking |
| b_lto | false | true, false | Use link time optimization |
| b_lto_threads | 0 | Any integer* | Use multiple threads for lto. (Added in 0.57.0) |
| b_lto_mode | default | default, thin | Select between lto modes, thin and default. (Added in 0.57.0) |
| b_thinlto_cache | false | true, false | Enable LLVM's ThinLTO cache for faster incremental builds. (Added in 0.64.0) |
| b_thinlto_cache_dir | (Internal build dir) | true, false | Specify where to store ThinLTO cache objects. (Added in 0.64.0) |
| b_ndebug | false | true, false, if-release | Disable asserts |
| b_pch | true | true, false | Use precompiled headers |
| b_pgo | off | off, generate, use | Use profile guided optimization |
| b_sanitize | none | see below | Code sanitizer to use |
| b_staticpic | true | true, false | Build static libraries as position independent |
| b_pie | false | true, false | Build position-independent executables (since 0.49.0) |
| b_vscrt | from_buildtype | none, md, mdd, mt, mtd, from_buildtype, static_from_buildtype | VS runtime library to use (since 0.48.0) (static_from_buildtype since 0.56.0) |
The value of b_sanitize can be one of: none, address, thread, undefined, memory, leak, address,undefined, but note that some compilers might not support all of them. For example Visual Studio only supports the address sanitizer.
* < 0 means disable, == 0 means automatic selection, > 0 sets a specific number to use
LLVM supports thin lto, for more discussion see LLVM's documentation
The default value of b_vscrt is from_buildtype. The following table is used internally to pick the CRT compiler arguments for from_buildtype or static_from_buildtype (since 0.56) based on the value of the buildtype option:
| buildtype | from_buildtype | static_from_buildtype |
|---|---|---|
| debug | /MDd | /MTd |
| debugoptimized | /MD | /MT |
| release | /MD | /MT |
| minsize | /MD | /MT |
| custom | error! | error! |
b_bitcode will pass -fembed-bitcode while compiling and will pass -Wl,-bitcode_bundle while linking. These options are incompatible with b_asneeded, so that option will be silently disabled.
[[shared_module]]s will not have bitcode embedded because -Wl,-bitcode_bundle is incompatible with both -bundle and -Wl,-undefined,dynamic_lookup which are necessary for shared modules to work.
Same caveats as base options above.
The following options are available. They can be set by passing -Doption=value to meson. Note that both the options themselves and the possible values they can take will depend on the target platform or compiler being used:
| Option | Default value | Possible values | Description |
|---|---|---|---|
| c_args | free-form comma-separated list | C compile arguments to use | |
| c_link_args | free-form comma-separated list | C link arguments to use | |
| c_std | none | none, c89, c99, c11, c17, c18, c2x, c23, gnu89, gnu99, gnu11, gnu17, gnu18, gnu2x, gnu23 | C language standard to use |
| c_winlibs | see below | free-form comma-separated list | Standard Windows libs to link against |
| c_thread_count | 4 | integer value ≥ 0 | Number of threads to use with emcc when using threads |
| cpp_args | free-form comma-separated list | C++ compile arguments to use | |
| cpp_link_args | free-form comma-separated list | C++ link arguments to use | |
| cpp_std | none | none, c++98, c++03, c++11, c++14, c++17, c++20 c++2a, c++1z, gnu++03, gnu++11, gnu++14, gnu++17, gnu++1z, gnu++2a, gnu++20, vc++14, vc++17, vc++20, vc++latest | C++ language standard to use |
| cpp_debugstl | false | true, false | C++ STL debug mode |
| cpp_eh | default | none, default, a, s, sc | C++ exception handling type |
| cpp_rtti | true | true, false | Whether to enable RTTI (runtime type identification) |
| cpp_thread_count | 4 | integer value ≥ 0 | Number of threads to use with emcc when using threads |
| cpp_winlibs | see below | free-form comma-separated list | Standard Windows libs to link against |
| fortran_std | none | [none, legacy, f95, f2003, f2008, f2018] | Fortran language standard to use |
| cuda_ccbindir | filesystem path | CUDA non-default toolchain directory to use (-ccbin) (Added in 0.57.1) |
The default values of c_winlibs and cpp_winlibs are in compiler-specific argument forms, but the libraries are: kernel32, user32, gdi32, winspool, shell32, ole32, oleaut32, uuid, comdlg32, advapi32.
All these <lang>_* options are specified per machine. See below in the specifying options per machine section on how to do this in cross builds.
When using MSVC, cpp_eh=[value] will result in /EH[value] being passed. The magic value none translates to s-c- to disable exceptions. Since 0.51.0 default translates to sc. When using gcc-style compilers, nothing is passed (allowing exceptions to work), while cpp_eh=none passes -fno-exceptions.
Since 0.54.0 The <lang>_thread_count option can be used to control the value passed to -s PTHREAD_POOL_SIZE when using emcc. No other c/c++ compiler supports this option.
Since 0.63.0 all compiler options can be set per subproject, see here for details on how the default value is inherited from the main project. This is useful, for example, when the main project requires C++11, but a subproject requires C++14. The cpp_std value from the subproject's default_options is now respected.
Since 1.3.0 c_std and cpp_std options now accept a list of values. Projects that prefer GNU C, but can fallback to ISO C, can now set, for example, default_options: 'c_std=gnu11,c11', and it will use gnu11 when available, but fallback to c11 otherwise. It is an error only if none of the values are supported by the current compiler. Likewise, a project that can take benefit of c++17 but can still build with c++11 can set default_options: 'cpp_std=c++17,c++11'. This allows us to deprecate gnuXX values from the MSVC compiler. That means that default_options: 'c_std=gnu11' will now print a warning with MSVC but fallback to c11. No warning is printed if at least one of the values is valid, i.e. default_options: 'c_std=gnu11,c11'. In the future that deprecation warning will become an hard error because c_std=gnu11 should mean GNU is required, for projects that cannot be built with MSVC for example.
Since 0.51.0, some options are specified per machine rather than globally for all machine configurations. Prefixing the option with build. only affects the build machine configuration, while leaving it unprefixed only affects the host machine configuration. For example:
build.pkg_config_path controls the paths pkg-config will search for native: true (build machine) dependencies.
pkg_config_path controls the paths pkg-config will search for native: false (host machine) dependencies.
This is useful for cross builds. In native builds, the build and host machines are the same, and the unprefixed option alone will suffice.
Prior to 0.51.0, these options only affected native builds when specified on the command line as there was no build. prefix. Similarly named fields in the [properties] section of the cross file would affect cross compilers, but the code paths were fairly different, allowing differences in behavior to crop out.
Since 0.54.0 default_library and werror built-in options can be defined per subproject. This is useful, for example, when building shared libraries in the main project and statically linking a subproject, or when the main project must build with no warnings but some subprojects cannot.
Most of the time, this would be used either in the parent project by setting subproject's default_options (e.g. subproject('foo', default_options: 'default_library=static')), or by the user through the command line: -Dfoo:default_library=static.
The value is overridden in this order:
Since 0.56.0 warning_level can also be defined per subproject.
Some Meson modules have built-in options. They can be set by prefixing the option with the module's name: -D<module>.<option>=<value> (e.g. -Dpython.platlibdir=/foo).
| Option | Default value | Possible values | Description |
|---|---|---|---|
| relocatable | false | true, false | Generate the pkgconfig files as relocatable (Since 0.63.0) |
Since 0.63.0 The pkgconfig.relocatable option is used by the pkgconfig module–namely pkg.generate()–and affects how the prefix (not to be confused with the install prefix) in the generated pkgconfig file is set. When it is true, the prefix will be relative to the install_dir-this allows the pkgconfig file to be moved around and still work, as long as the relative path is not broken. In general, this allows for the whole installed package to be placed anywhere on the system and still work as a dependency. When it is set to false, the prefix will be the same as the install prefix.
An error will be raised if pkgconfig.relocatable is true and the install_dir for a generated pkgconfig file points outside the install prefix. For example: if the install prefix is /usr and the install_dir for a pkgconfig file is /var/lib/pkgconfig.
| Option | Default value | Possible values | Description |
|---|---|---|---|
| bytecompile | 0 | integer from -1 to 2 | What bytecode optimization level to use (Since 1.2.0) |
| install_env | prefix | {auto,prefix,system,venv} | Which python environment to install to (Since 0.62.0) |
| platlibdir | Directory path | Directory for site-specific, platform-specific files (Since 0.60.0) | |
| purelibdir | Directory path | Directory for site-specific, non-platform-specific files (Since 0.60.0) | |
| allow_limited_api | true | true, false | Disables project-wide use of the Python Limited API (Since 1.3.0) |
Since 0.60.0 The python.platlibdir and python.purelibdir options are used by the python module methods python.install_sources() and python.get_install_dir(); Meson tries to detect the correct installation paths and make them relative to the installation prefix by default which will often result in the interpreter not finding the installed python modules unless prefix is /usr on Linux, or, for instance, C:\Python39 on Windows. These options can be absolute paths outside of prefix.
Since 0.62.0 The python.install_env option is used to detect the correct installation path. Setting to system will avoid making the paths relative to prefix and instead use the global site-packages of the selected python interpreter directly, even if it is a venv. Setting to venv will instead use the paths for the virtualenv the python found installation comes from (or fail if it is not a virtualenv). Setting to auto will check if the found installation is a virtualenv, and use venv or system as appropriate (but never prefix). Note that Conda environments are treated as system. This option is mutually exclusive with the platlibdir/purelibdir.
For backwards compatibility purposes, the default install_env is prefix.
Since 1.2.0 The python.bytecompile option can be used to enable compiling python bytecode. Bytecode has 3 optimization levels:
To this, Meson adds level -1, which is to not attempt to compile bytecode at all.
Since 1.3.0 The python.allow_limited_api option affects whether the limited_api keyword argument of the extension_module method is respected. If set to false, the effect of the limited_api argument is disabled.