Meson Setup and Configuration

meson setup creates the build directory and locks in the compiler, toolchain, and option set. Use meson configure for later edits and meson setup --reconfigure when the build state should be refreshed.

Useful defaults

meson setup builddir -Dwarning_level=3

Common configuration goals

• switch between debug and release
• turn warnings into errors
• enable or disable optional features
• set the install prefix and directories
• choose sanitizers or LTO
• adjust the language standard
• choose native or cross machine files

Build-type guidance

Use build types as workflow choices, not as hidden policy inside every project example.

• debug for day-to-day development
• debugoptimized for a practical developer build
• release for shipping binaries
• minsize when footprint matters
• plain when the build should avoid Meson-imposed defaults

Practical rules

• set compiler selection before the first meson setup
• edit options with meson configure instead of rewriting the build tree by hand
• wipe or reconfigure when the toolchain changes
• keep project options in meson_options.txt and project(default_options: ...)
• use built-in options for standards and warning levels rather than manual -std= flags

Modern baseline

All examples in this repository assume meson_version: '>=1.7.0' and the following standard project header:

project(
  'my-project',
  'c',
  'cpp',
  version: '0.1.0',
  meson_version: '>=1.7.0',
  license: 'MIT',
  license_files: ['LICENSE'],
  default_options: [
    'c_std=c17',
    'cpp_std=c++20',
    'warning_level=3',
  ],
)

Common mistakes

• changing compiler variables after setup and expecting them to take effect automatically
• editing the build tree by hand instead of reconfiguring
• putting language standards in random target arguments instead of built-in options
• forcing production-only settings into beginner examples
• confusing project defaults with per-build workflow decisions

Language Standard Selection Guidance

When migrating a project to Meson:

1. Inspect CMakeLists.txt for CMAKE_C_STANDARD and CMAKE_CXX_STANDARD.
2. Inspect Autotools files such as configure.ac and Makefile.am, plus any compiler flags like -std=c17 or -std=c++20.
3. Inspect plain Makefiles for -std= flags.
4. Inspect CI configurations and compiler invocation scripts.
5. If the standards still cannot be deduced, ask the user directly which C and C++ standards they want.
6. If the project is being created from scratch and the user has no preference, default to the default_options block in the project header above.

Do not silently change language standards during Meson migration.