ci: ios

[henryiii]

Description

Builds on #5708.

Suggested changelog entry:

• Test on iOS in CI.

[henryiii]

@b-pass how hard would it be to work around thread_local, possibly via an opt-in mechanism? iOS requires an increased target to get thread_local, but you can't require it currently due to python/cpython#133183 not being in a release yet. It would also be nice to have a way to target iOS 13 (I think 17 is required for thread-local). Ideally we could detect the the target iOS version and select the correct mechanism.

[b-pass]

@b-pass how hard would it be to work around thread_local, possibly via an opt-in mechanism?

The easiest thing would be to just exclude the platform from PYBIND11_HAS_SUBINTERPRETER_SUPPORT.

Does CPython's PyThread_tss_set (and friends) work on this target? pybind11 is using that else where so I am guessing yes?

If so, then I can probably make something that uses that....

[henryiii]

This might just be a problem with it defaulting to iOS 1, hopefully a new build with the upstream fix will be out soon. What I did for now was allow this to be manually overridden. 13 is was CPython itself is compiled against. If 13+ turns out to be fine, it's okay. If it does require 17+, we can document it at least, and develop a workaround if it wasn't too hard.

[henryiii]

iOS test pass! (Minus the sub interpreter ones which I disabled when building)

[henryiii]

I think it must handle PYBIND11_TLS_*, happy to test something in the iOS job if you have an idea.

[henryiii]

It would probably be easier to set up a PYBIND11_TLS_* version if this was in so it would be part of the CI, so taking out of draft.