[android] Use emulated thread-local storage for API 28 and earlier #78513
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Android before API 29 and a few other platforms don't support native TLS, so
fall back to LLVM's emulated TLS there, just like clang does. Also, make sure
`-Xcc -f{no-,}emulated-tls` flags passed in are applied to control what the
Swift compiler does.
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@swift-ci please test |
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@DougGregor, this is in trunk and 6.0 now, should get it in 6.1 also. |
DougGregor
approved these changes
Jan 15, 2025
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Explanation: Android before API 29 and a few other platforms don't support native TLS, so fall back to LLVM's emulated TLS there, just like clang does. Also, make sure
-Xcc -f{no-,}emulated-tlsflags passed in are applied to control what the Swift compiler does.Scope: Has no effect by default, except on Android API 28 or older, OpenBSD, and a couple other platforms Swift doesn't support
Issue: None
Original PR: #77883
Risk: very low
Testing: Passed all CI on trunk and now on my Android CI running at API 24, when built with the latest Jan. 10 trunk snapshot tag containing this commit
Reviewer: @compnerd
This will allow Foundation in my Android SDK bundle and native toolchain for Android to support APIs 24-28 again, finagolfin/swift-android-sdk#175.