🍒[cxx-interop][Runtime] Initialize metadata of a Swift array of C++ references correctly #73671
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…ferences correctly This fixes a crash at runtime when destroying a Swift array of values of a C++ foreign reference type. Swift optimizes the amount of metadata emitted for `_ContiguousArrayStorage<Element>` by reusing `_ContiguousArrayStorage<AnyObject>` whenever possible (see `getContiguousArrayStorageType`). However, C++ foreign reference types are not `AnyObject`s, since they have custom retain/release operations. This change disables the `_ContiguousArrayStorage` metadata optimization for C++ reference types, which makes sure that `swift_arrayDestroy` will call the correct release operation for elements of `[MyCxxRefType]`. rdar://127154770 (cherry picked from commit fd04cc3)
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@swift-ci please test |
DougGregor
approved these changes
May 16, 2024
| @@ -1,5 +1,6 @@ | |||
| // RUN: %target-swift-emit-irgen %s -I %S/Inputs -cxx-interoperability-mode=default -Xcc -fignore-exceptions -disable-availability-checking | %FileCheck %s | |||
| // XFAIL: OS=linux-android, OS=linux-androideabi | |||
| // XFAIL: OS=windows-msvc | |||
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Why? If there are really platform-specific tests here, can we put them in a separate file?
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Foreign reference types don't yet work on Windows, since we don't have the lazy metadata initialization logic implemented: https://github.com/apple/swift/blob/d380bf9ae361520f0c1f16519a199afe46ea99dc/lib/IRGen/GenMeta.cpp#L6578-L6581
Previously this test wasn't going through this code path on Windows, but now it does and it hits llvm_unreachable.
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Explanation: This fixes a crash at runtime when destroying a Swift array of values of a C++ foreign reference type. Swift optimizes the amount of metadata emitted for
_ContiguousArrayStorage<Element>by reusing_ContiguousArrayStorage<AnyObject>whenever possible (seegetContiguousArrayStorageType). However, C++ foreign reference types are notAnyObjects, since they have custom retain/release operations. This change disables the_ContiguousArrayStoragemetadata optimization for C++ reference types, which makes sure thatswift_arrayDestroywill call the correct release operation for elements of[MyCxxRefType].Scope: Changes the runtime handling of C++ foreign reference types – they will no longer be treated as AnyObjects by the runtime. Also changes the SIL logic that handles the
_ContiguousArrayStorage<AnyObject>optimization.Risk: Low, only affects C++ foreign reference types.
Testing: Added a compile test.
Issue: rdar://127154770 / #72827
Reviewer: @mikeash @aschwaighofer @zoecarver
Original PR: #73615