iOS 3.14 issue with headers

[henryiii]

CMake can't find the headers on iOS for 3.14, while it works fine for 3.13. See https://github.com/scikit-hep/boost-histogram/actions/runs/16185879791/job/45691357501

This is reported missing:

/private/var/folders/y6/nj790rtn62lfktb1sh__79hc0000gn/T/build-env-r7hap9z2/include/python3.14

CC @freakboy3742

[freakboy3742]

After an initial investigation - it looks like the sysconfig paths aren't being updated correctly by the make-cross-venv script in the 3.14 support package. If you run:

>>>import sysconfig
>>> for key, value in sorted(sysconfig.get_paths().items()):
...     print(key, value)
...     

in a 3.14 environment, you get:

data /Users/rkm/projects/pillow/venv3.14-ios-sim
include /Users/rkm/projects/pillow/venv3.14-ios-sim/include/python3.14
platinclude /Users/rkm/projects/pillow/venv3.14-ios-sim/include/python3.14
platlib /Users/rkm/projects/pillow/venv3.14-ios-sim/lib/python3.14/site-packages
platstdlib /Users/rkm/projects/pillow/venv3.14-ios-sim/lib/python3.14
purelib /Users/rkm/projects/pillow/venv3.14-ios-sim/lib/python3.14/site-packages
scripts /Users/rkm/projects/pillow/venv3.14-ios-sim/bin
stdlib /Users/rkm/projects/pillow/venv3.14-ios-sim/lib/python3.14

but on 3.13, you get:

data /Users/rkm/projects/pillow/venv3.13-ios-sim
include /Users/rkm/Library/Caches/cibuildwheel/Python-3.13-iOS-support.b9/Python.xcframework/ios-arm64_x86_64-simulator/include/python3.13
platinclude /Users/rkm/Library/Caches/cibuildwheel/Python-3.13-iOS-support.b9/Python.xcframework/ios-arm64_x86_64-simulator/include/python3.13
platlib /Users/rkm/projects/pillow/venv3.13-ios-sim/lib/python3.13/site-packages
platstdlib /Users/rkm/projects/pillow/venv3.13-ios-sim/lib/python3.13
purelib /Users/rkm/projects/pillow/venv3.13-ios-sim/lib/python3.13/site-packages
scripts /Users/rkm/projects/pillow/venv3.13-ios-sim/bin
stdlib /Users/rkm/Library/Caches/cibuildwheel/Python-3.13-iOS-support.b9/Python.xcframework/ios-arm64_x86_64-simulator/lib/python3.13

As a result, the includes are not being found where they're expected.

My guess is that this is related to the introduction of the JSON sysconfig representation, but I'll need to dig deeper to be certain (and compose a fix).

[mhsmith]

I don't think the JSON sysconfig representation is actually being used for anything. There were plans to do this, but they weren't completed in time for 3.14. See python/cpython#127180.

[freakboy3742]

Sure - but something has changed, because the implementation of the monkeypatch file is identical between the 3.13 branch and the 3.14 branch of the support package.

[freakboy3742]

I've found the source of the problem - there's been a subtle change to how sysconfig._init_config_vars() works, which is messing with the cross-env script. I think I have a workaround; I'm in the process of testing it.

[freakboy3742]

Ok - so the fix is to modify three files.

Unfortunately, AFAIK there's no easy way for me to provide a version of the fix for testing - it needs to be in a formal iOS support package release, which is then incorporated into a formal cibuildwheel release.

However - it is possible to manually modify change locally to confirm that the fix will work.

In the cibuildwheel-cached Python 3.14 iOS support package (~/Library/Caches/cibuildwheel/Python-3.14-iOS-support.b5/), there is a file for each supported platform that sets up the cross-platform environment. The three files are:

• Python.xcframework/ios-arm64/platform-config/arm64-iphoneos/_cross_arm64_iphoneos.py
• Python.xcframework/ios-arm64_x86_64-simulator/platform-config/arm64-iphonesimulator/_cross_arm64_iphonesimulator.py
• Python.xcframework/ios-arm64_x86_64-simulator/platform-config/arm64-iphonesimulator/_cross_arm64_iphonesimulator.py

In each of these files, line 14 and 15 reads:

sys.base_prefix = sysconfig.get_config_var("prefix")
sys.base_exec_prefix = sysconfig.get_config_var("prefix")

If you modify this to read:

sys.base_prefix = sysconfig._get_sysconfigdata()["prefix"]
sys.base_exec_prefix = sysconfig._get_sysconfigdata()["prefix"]

you should be able to complete an iOS 3.14 build.

@henryiii If I could impose on you to make that tweak manually on your local cibuildwheel cache and confirm it's working for you, I'll roll that change into a new iOS support package release.

[henryiii]

I'll need to try that at home, my laptop is Intel, my mini at home is an M1.

[henryiii]

By the way, iOS 3.14 builds by default now in cibuildwheel 3.1. Having to manually skip it everywhere, like in pybind/scikit_build_example#166

I can try to set this up locally but flying out for my fourth conference in a row so might not manage to do it before then. (Edit: I didn't)

[freakboy3742]

Understood on 3.14 being a default build for cibuildwheel 3.1. I've got a PR ready to merge that implements the change I described above (see beeware/Python-Apple-support#310); that PR includes a test of cross-platform environments that should hopefully prevent this problem from emerging in future.

If you're unlikely to have a chance to do external testing of that fix any time soon, I'm happy to merge it as is, and cut new support package versions; we'd then need to bump the revisions in cibuldwheel and cut a new cibuildwheel release to make those versions live.

[henryiii]

I'd like to do a new cibuildwheel release soon with the recent hot fixes, it would be nice if this could make it in. I won't be back at home for a few days, so I'd recommend not waiting on me unless you really want to.

[freakboy3742]

No worries - I'm fairly certain this fixes the issue, so I'll merge that PR, cut new releases, and submit a PR for the cibuildwheel revision bump.

[freakboy3742]

3.14-b6 and 3.13-b10 have been published; #2530 contains the version bump for cibuildwheel.