Get Platform and Architecture at Build Time

[seanlaw]

Hi all,

I am using Github Actions and cibuildwheel to build wheels for Windows x64 and win32. Additionally, I have a CIBW_BEFORE_BUILD: bash ./build.sh script that executes right before building the wheel but contains a condition (if/else) that depends on whether it is an x64 build (i.e., omit a cmake flag) OR a win32 build (i.e., add a cmake flag). I was wondering if there was any way to add some logic inside of the build.sh script to detect that cibuildwheel is currently building a wheel for win32 so that I can set my cmake flag accordingly?

So, inside of build.sh, I'd be looking to do something like:

if [ "$PLATFORM" == "Windows" && "$ARCH" == "win32"]; then
    # Set cmake flag here
fi

Any help would be greatly appreciated!

[louisabraham]

Why not use CIBW_ARCHS to restrict the architecture and use two different jobs (one for x86 and one for x64)?

[seanlaw]

Definitely possible. I was hoping for something a bit more straightforward like the if condition :). It will just make the Github Actions workflow much longer than it already is.

[henryiii]

Could we set an extra environment variable or two, perhaps, to make this a bit easier? We could set CIBW_CURRENT_SELECTOR to the current selector inside the (before) build steps, and maybe CIBW_ARCH (no S) inside build-all and before-build?

Splitting the build by CIBW_ARCH likely is nice for doing parallel builds, so not a bad solution, but just thinking of a possible general solution.

[seanlaw]

Yes, I think that would be helpful! And I agree that a general solution is best. Essentially, to some extent, I think my condition/question is satisfied as long as I can "introspect" (??) from within a given step (i.e., before build) the current architecture and platform (along with any other cibuildwheel condition) that is unique to the current build environment.

[joerick]

This seems pretty reasonable to me. In terms of naming, we already set CIBUILDWHEEL=1 for our builds, so perhaps we could add CIBUILDWHEEL_BUILD_IDENTIFIER - the CIBUILDWHEEL prefix distinguishing these variables from CIBW options.

[hynek]

I would love to have something like CIBW_CURRENT_SELECTOR / CIBW_ARCH.

In argon2-cffi-bindings I need to distinguish whether I'm cross-compiling and my current approach feels super janky and I expect it to break in weird ways in the most unfortunate moment.

[joerick]

Thanks for the feedback! Created an issue for this feature request #944