IRGen: Weak-link references to swift_getExtendedExistentialTypeMetadata() [5.9] #69462
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slavapestov
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…ta() Fixes rdar://117530421.
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@swift-ci Please test |
DougGregor
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Oct 28, 2023
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main PR: IRGen: Weak-link references to swift_getExtendedExistentialTypeMetadata() #69459
Description: The type checker guards certain dynamic uses of constrained existential types SE-0353 behind an availability check, because the runtime entry point to instantiate extended existential metadata is only available on newer OSes. However, even if the metadata instantiation was dynamically unreachable at runtime, we forgot to weak link the symbol. This caused missing symbol errors at runtime.
Scope of the issue: Affects framework authors attempting backward deployment of conditionally-available code that requires extended existential metadata.
Origination: This scenario never worked.
Risk: Very low as this just changes the linkage of a symbol when the deployment target is sufficiently old.
Tested: New test case added.
Reviewed by: @tshortli on main
Radar: rdar://117530421.