Meson

Meson project setup, build options, the wrap dependency system, and cross-compilation. Grounded against Meson 1.12.0; Meson drives Ninja as its backend.

Contract

Field	Bound contract
Trigger	The task sets up a Meson project, writes meson.build or meson.options, manages wrap dependencies, configures build options, cross-compiles with a cross file, or migrates from CMake or Autotools.
Authority	Reversible local: writes only meson.build, meson.options/meson_options.txt, cross and native files, subprojects/, and the build directory; rollback is version control plus deleting the build directory. No remote mutation.
Side effect	meson compile and meson test write local build outputs; meson wrap install downloads wrap files into subprojects/.
Done	meson setup, meson compile, and meson test run clean on the configured build directory, or the failing command is reported.

Inputs

• Project layout (required): sources and the root meson.build location.
• Meson version (required if not inferrable): run meson --version. meson.options needs Meson 1.1 or newer; older trees use meson_options.txt.
• Dependencies (optional): system libraries or wrap names from WrapDB.
• Cross target (optional): a cross file describing the host machine.

Procedure

1. Configure the build directory. Done when: meson setup builddir succeeds.

meson setup builddir
meson setup builddir \
    --buildtype=release \
    --prefix=/usr/local \
    -Db_lto=true \
    -Db_sanitize=address

meson configure builddir -Dbuildtype=debug   # reconfigure in place
meson configure builddir                     # list all options

--buildtype	Flags added
debug (default)	-O0 -g
debugoptimized	-O2 -g
release	-O3 -DNDEBUG
minsize	-Os -DNDEBUG
plain	none
custom	user-supplied flags only

2. Build, test, and install. Done when: compile and test pass in the build directory.

meson compile -C builddir
meson test -C builddir
meson test -C builddir --verbose
meson test -C builddir -t 5            # 5x timeout multiplier
meson test -C builddir --suite unit    # one suite only
meson install -C builddir
meson install -C builddir --dry-run

3. Write meson.build. Done when: every target declares its sources, includes, and dependencies.

project('myapp', 'c', 'cpp',
  version : '1.0.0',
  default_options : [
    'c_std=c23',
    'cpp_std=c++23',
    'warning_level=2',
  ]
)

glib_dep = dependency('glib-2.0', version : '>=2.68')
threads_dep = dependency('threads')
inc = include_directories('include')

mylib = static_library('mylib',
  sources : ['src/lib.c', 'src/util.c'],
  include_directories : inc,
)

executable('myapp',
  sources : ['src/main.c'],
  include_directories : inc,
  link_with : mylib,
  dependencies : [glib_dep, threads_dep],
  install : true,
)

test('basic', executable('test_basic',
  sources : ['tests/test_basic.c'],
  link_with : mylib,
))

4. Manage dependencies with wrap. Done when: dependency() resolves from the system or falls back to the wrap.

meson wrap search zlib
meson wrap install zlib
meson wrap list
meson wrap update

# System first, wrap as fallback
zlib_dep = dependency('zlib', fallback : ['zlib', 'zlib_dep'])

# Force the wrap for reproducible builds
zlib_dep = dependency('zlib',
  fallback : ['zlib', 'zlib_dep'],
  default_options : ['default_library=static'],
)

5. Define project options in meson.options (Meson 1.1+) or meson_options.txt. Done when: meson configure lists the option and get_option reads it.

option('with_tests', type : 'boolean', value : true,
  description : 'Build unit tests')

option('backend', type : 'combo',
  choices : ['opengl', 'vulkan', 'software'],
  value : 'opengl')

option('max_connections', type : 'integer',
  min : 1, max : 1024, value : 64)

if get_option('with_tests')
  subdir('tests')
endif

6. Cross-compile with a cross file. Use pkg-config as the key name; pkgconfig is deprecated. Done when: meson setup --cross-file configures for the host machine.

# cross/arm-linux.ini
[binaries]
c = 'arm-linux-gnueabihf-gcc'
cpp = 'arm-linux-gnueabihf-g++'
ar = 'arm-linux-gnueabihf-ar'
strip = 'arm-linux-gnueabihf-strip'
pkg-config = 'arm-linux-gnueabihf-pkg-config'

[properties]
sys_root = '/path/to/sysroot'

[host_machine]
system = 'linux'
cpu_family = 'arm'
cpu = 'cortex-a9'
endian = 'little'

meson setup builddir-arm --cross-file cross/arm-linux.ini
meson compile -C builddir-arm

7. Migrate from CMake with this mapping. Done when: each CMake construct has its Meson equivalent.

CMake	Meson
add_executable	executable()
add_library	library(), static_library(), shared_library()
target_include_directories	include_directories kwarg
target_link_libraries	dependencies and link_with kwargs
find_package	dependency()
option()	option() in meson.options
add_subdirectory	subdir()
install(TARGETS ...)	install : true kwarg

For wrap file types, subproject patching, and compiler checks see references/meson-wrap.md.

Failure and recovery

• dependency() fails and no wrap exists: run meson wrap search <name>; if WrapDB lacks it, vendor the source under subprojects/ with its own meson.build.
• meson setup rejects an option: the option lives in meson.options or is a built-in -D name; run meson configure builddir to list valid names.
• Cross build picks up host libraries: the cross file needs sys_root under [properties] and correct pkg-config under [binaries].
• Wrap download fails offline: pre-seed subprojects/packagecache/ with the archive named in the wrap's source_url.
• Reconfigure does not take: some options are read once at setup; wipe the build directory with meson setup --wipe builddir or delete it and reconfigure.

Output

A working meson.build with declared targets and dependencies, a configured build directory that compiles and tests clean, and for cross tasks a cross file verified by meson setup --cross-file.