Built-in options
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.
Universal 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:
- When the prefix is
/usr:sysconfdirdefaults to/etc,localstatedirdefaults to/var, andsharedstatedirdefaults to/var/lib - When the prefix is
/usr/local:localstatedirdefaults to/var/local, andsharedstatedirdefaults to/var/local/lib - When an absolute path outside of prefix is provided by the user/distributor.
Directories
| 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().
Core options
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 |
| 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 = none 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 |
Details for backend
Several 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.
Details for 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'.
Details for warning_level
Exact 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.
Details for vsenv
The --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.
Base options
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! |
Notes about Apple Bitcode support
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.
Compiler options
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, gnu89, gnu99, gnu11, gnu17, gnu18, gnu2x | 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=none will result in no exception flags being
passed, while the cpp_eh=[value] will result in /EH[value]. Since
0.51.0 cpp_eh=default will result in /EHsc on MSVC. 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.
Specifying options per machine
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_pathcontrols the paths pkg-config will search fornative: true(build machine) dependencies. -
pkg_config_pathcontrols the paths pkg-config will search fornative: 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.
Specifying options per subproject
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:
- Value from parent project
- Value from subproject's default_options if set
- Value from subproject() default_options if set
- Value from command line if set
Since 0.56.0 warning_level can also be defined per subproject.
Module options
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).
Pkgconfig module
| 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.
Python module
| 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) |
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). 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:
- 0, bytecode without optimizations
- 1, bytecode with some optimizations
- 2, bytecode with some more optimizations
To this, Meson adds level -1, which is to not attempt to compile bytecode at
all.
The results of the search are