I found#128156 locally, so this is working. We'll see if it's caught in the current CI setup (it was not, setting0f4b63e now)

I set the deployment target to 10.9 and 🎉 we catch the unguarded symbol. I guess ideally it'd be 10.3 since that's the stated minimum but compilation fails for that on my machine. I'm happy to debate what the minimum should be, but perhaps we should open a dedicated issue for that discussion? Using 10.9 instead of 10.15 catches symbols that have been reported as bugs recently, so I don't think going to 10.15 here makes sense.

This pull request is now blocked on#128156 or reversion of0f4b63e — I'm fine with either as long as we follow-up with something like0f4b63e.

The current releases of Apple's Xcode and Command Line Tools now only fully support building for deployment targets of 10.13 or newer and we should be testing with that. There are older versions of Xcode available in the the Github Actions macOS images. We may need to set up a different build to test with older deployment targets. This requires some more investigation and thought.

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The current releases of Apple's Xcode and Command Line Tools now only fully support building for deployment targets of 10.13 or newer and we should be testing with that.

Done in24ee4a7 though we may want to just bump to 10.15 per#128156 (comment)

though we may want to just bump to 10.15

Oh, sorry, we're clearly going to need to do that in this PR otherwise all macOS CI checks will fail.

@ned-deily yeah, I wasn't sure if we wanted to try to solve#128156 before merging this but I'm happy to just bump to 10.15 then consider support for older versions separately?

Yes, let's go with macOS 10.15 for Python 3.14 for now.

For the record, this applies to "portable" builds, that is, built on a new version of macOS and run on a different (older) version of macOS. While not explicitly tested on older releases, configuring (without a MACOS_DEPLOYMENT_TARGET), building, and running on the same system should work with any particular version of macOS.

I think a next step here is to propose an explicit CPython macOS support policy for 3.14 as a PEP, something that has been in the queue for awhile, and include with it details on supported "portable" ranges (like building on macOS 15 with a deployment target of 10.15) and with which universal architectures, to be backed up by GHA and/or buildbots CI testing. Having that should make making implementation decisions easier. I'll try to get to that later this week when I again have access to older macOS systems.

P.S. Thanks,@zanieb, for all your work on this!