[android] Use emulated thread-local storage for API 28 and earlier #78591
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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.
finagolfin
added
🍒 release cherry pick
|
@swift-ci please test |
DougGregor
approved these changes
Jan 14, 2025
Yes, I make a few more changes to the CMake config or Android module map that've been merged into trunk also, such as #76460 and #78241, but those are for all API versions and can be added easily on my CI. This change can't, as my Android CI uses the official prebuilt compiler for linux to cross-compile the stdlib and corelibs, so I'm trying to get this compiler change in for that. |
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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.