Passing extra config settings to the CIBW_BUILD_FRONTEND.

[andyfaff]

I would like to use the CIBW_BUILD_FRONTEND: "build". More importantly I am interested in passing extra configuration settings to this front-end.

For example, if I use build directly I can pass extra config settings using the C flag:

python -m build . -C--opt=value

Is there a way of providing those extra config settings to cibuildwheel, such that it will then provide them to the CIBW_BUILD_FRONTEND? i.e. something along the lines of CIBW_BUILD_FRONTEND_FLAGS.

I can't find anything in the documentation that would suggest that's possible.

[Czaki]

The cibuildwheel set CIBUILDWHEEL environment variable to 1. So you could conditionally apply some flags in setup.py.

https://cibuildwheel.readthedocs.io/en/stable/faq/#building-packages-with-optional-c-extensions

I know that it is a workaround, not a solution requested by you, but maybe it is enough for your case.

[andyfaff]

Im not sure that will work. The build hierarchy is cibuildwheel --> pip-->mesonpy (the build backend in pyproject.toml) --> meson --> ninja. I'm trying to tell meson to do a cross compile. The normal way of specifying a cross-compile is meson setup --cross-file cross_arm64.txt build. This tells meson to use build as the build directory and place all of its build configuration in there. I can therefore do something like:

meson setup --cross-file cross_arm64.txt build
python -m build -Cbuilddir=build

and the build frontend will make a cross platform wheel. However, if using cibuildwheel I don't get to issue the second command, so I need cibuildwheel to pass in that extra configuration for me. The project I'm using doesn't use setup.py in the meson build.

[oscarbenjamin]

This is now possible with CIBW_CONFIG_SETTINGS:
https://cibuildwheel.pypa.io/en/stable/options/#config-settings

[henryiii]

There are two things: the build backend settings, which are -C flags, are possible via config-settings, yes. For arbitrary build frontend flags, that's also possible now with a custom syntax when setting build-frontend (table in TOML, semicolon in environment variable).