Environment variables¶

Environment variables can be used to influence meson-python’s behavior, as well as the behavior of Meson and other tools that may be used during the build. This page lists all the environment variables directly used by meson-python.

Meson recommends using command line arguments instead of environment variables, but does support a number of environment variables for compatibility with other build systems:

Other environment variables may influence how other tools used during the setup or build steps operate. For example, pkg-config supports PKG_CONFIG_PATH which influences the search path for .pc files describing the available dependencies.

Warning

Conda sets a number of environment variables during environment activation for compiler/linker selection (CC, CXX, FC, LD) and compile/link flags (CFLAGS, CXXFLAGS, FFLAGS, LDFLAGS) when compilers are installed in a conda environment. This may have unexpected side effects (see for example the note in Using debug builds).

Environment variables used by meson-python¶

ARCHFLAGS¶

This environmental variable is used for supporting architecture cross compilation on macOS in a way compatible with setuptools. It is ignored on all other platforms. It can be set to -arch arm64 or to -arch x86_64 for compiling for the arm64 and the x86_64 architectures respectively. Setting this environment variable to any other value is not supported.

The macOS toolchain allows architecture cross compilation passing the -arch flat to the compilers. meson-python inspects the content of this environment variable and synthesizes a Meson cross build definition file with the appropriate content, and passes it to meson setup via the --cross-file option.

Support for this environment variable is maintained only for compatibility with existing tools, cibuildwheel in particular, and is not the recommended solution for cross compilation.

FORCE_COLOR¶: Setting this environment variable to any value forces the use of ANSI escape sequences to colorize the meson-python’s console output. Setting both NO_COLOR and FORCE_COLOR environment variables is an error.

MACOSX_DEPLOYMENT_TARGET¶

This environment variables is used of specifying the target macOS platform major version to the Xcode development tools. If this environment variable is set, meson-python will use the specified macOS version for the Python wheel platform tag instead than the macOS version of the build machine.

This variable must be set to macOS major versions only: 10.9 to 10.15, 11, 12, 13, …

Please note that the macOS versioning changed from macOS 11 onward. For macOS 10, the versioning scheme is 10.$major.$minor. From macOS 11 onward, it is $major.$minor.$bugfix. Wheel tags and deployment targets are currently designed to specify compatibility only with major version number granularity.

Another way of specifying the target macOS platform is to use the -mmacosx-version-min compile and link flags. However, it is not possible for meson-python to detect this, and it will not set the Python wheel platform tag accordingly.

MESON¶: Specifies the meson executable or script to use. It overrides tool.meson-python.meson. See Project settings for more details.

MESONPY_EDITABLE_VERBOSE¶: Setting this environment variable to any value enables directing to the console the messages emitted during project rebuild triggered by imports of editable wheels generated by meson-python. Refer to the Editable installs guide for more information.

NINJA¶: Specifies the ninja executable to use. It can also be used to select ninja alternatives like samurai.

NO_COLOR¶: Setting this environment variable to any value disables the use of ANSI terminal escape sequences to colorize meson-python’s console output. Setting both NO_COLOR and FORCE_COLOR environment variables is an error.