[cxx-interop] Avoid spurious references to _OBJC_CLASS symbols for C++ foreign reference types
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…C++ foreign reference types This removes erroneous references to `_OBJC_CLASS_$__xyz` symbols that Swift was emitting for certain usages of C/C++ foreign reference types. This was discovered when trying to iterate over a Swift array of foreign reference types using a Swift for-in loop. `Builtin.canBeClass` was returning true for foreign reference types, which led to the optimizer specializing the generic `canBeClass<T>` function to unconditionally return true for foreign reference types. This meant that `_isClassOrObjCExistential` for a foreign reference type evaluated to true, which made the Swift stdlib take the code path that was intended for Objective-C classes in `ArrayBuffer.getElement`, which assumed that the `Element` type conforms to `AnyObject`. Foreign reference types do not actually conform to `AnyObject`. rdar://161814644
egorzhdan
requested review from
zoecarver,
Xazax-hun,
j-hui,
fahadnayyar,
susmonteiro,
hnrklssn,
hborla,
slavapestov and
xedin
as code owners
|
@swift-ci please test |
Xazax-hun
approved these changes
Oct 3, 2025
|
@swift-ci please test macOS |
|
@swift-ci please test Linux |
j-hui
approved these changes
Oct 3, 2025
|
@swift-ci please test macOS |
1 similar comment
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@swift-ci please test macOS |
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This removes erroneous references to
_OBJC_CLASS_$__xyzsymbols that Swift was emitting for certain usages of C/C++ foreign reference types. This was discovered when trying to iterate over a Swift array of foreign reference types using a Swift for-in loop.Builtin.canBeClasswas returning true for foreign reference types, which led to the optimizer specializing the genericcanBeClass<T>function to unconditionally return true for foreign reference types. This meant that_isClassOrObjCExistentialfor a foreign reference type evaluated to true, which made the Swift stdlib take the code path that was intended for Objective-C classes inArrayBuffer.getElement, which assumed that theElementtype conforms toAnyObject. Foreign reference types do not actually conform toAnyObject.rdar://161814644