Optionaly disable OpenMP ...

[kif]

First of all, I would like to thank you for meson, it is a very nice build system, making the management of dependencies almost transparent in a cross-platform manner. I especially love the:
omp = dependency('openmp', required : false)

I am currently switching CI-platform for building the wheels (of a python project, built with meson-python) and found the windows packages broken because they were linked with libgomp.dll which is not generally available. This means meson finds the OpenMP dependency and compiles the code with it ... and as a consequence, the package is not working elsewhere.
silx-kit/pyFAI#2162
I wonder if you could suggest a way to disable the omp dependency even though it could be found ? I thought on an environment variable but maybe there are better ways to do it. An environment variable would be handy since the code has to be executed in a CI environment where meson is called from pip wheel called from ci-buildwheels ... many layers one on top of the other.

Thanks for your advice.

Jerome Kieffer

[kif]

I found the option and the feature in meson... this allows to setup easily something like this:
meson -Duse_openmp=disabled

The problem is that meson is embedded in meson-python which is called by pip wheel called from cibuildwheel ... not simple to have the information gone through.
Since some of PyPA developer impose all configuration to go via environment variable, which is incompatible with the philosophy of meson (according to #9 (comment)) I had a problem ...

But finally, going via a configuration file in root of the project looks like a viable solution (to be tested)
https://github.com/silx-kit/pyFAI/pull/2166/files

[eli-schwartz]

IIRC you can have a cibuildwheel config file that defines arguments always passed to pip, such as in this case -C setup-args=-Dopenmp=disabled. It would then run any time cibuildwheel is used, which of course is what you want in order to produce consistent PyPI wheels.