IRGen: Perform completely fragile layout for all classes, not just @objc ancestry [4.2 6/11] #17211
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ancestry Otherwise, Objective C categories don't work for classes with resilient fields, such as the value types defined in the Foundation overlay. Fixes <rdar://problem/40819319>, <https://bugs.swift.org/browse/SR-7882>.
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@swift-ci Please test |
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Description: In 4.2 we enabled resilience for value types. If a class has fields of resilient type the class metadata has to be initialized dynamically since the size of those fields is not known. Dynamic initialization of this form is not supported by the Objective-C runtime. We added a workaround so that classes with @objc ancestry bypass resilience when doing layout, allowing them to be referenced from Objective-C code. However classes without @objc ancestry can also have Objective-C categories and Objective-C protocol conformances. So broaden the workaround for all classes when Objective-C interop is enabled.
Scope of the issue: Reported by users testing beta 1.
Origination: New in 4.2.
Tested: Existing test change changed to have a non-NSObject subclass.
Risk: Low, the existing workaround is already known to work in the wild.
Radar: Fixes rdar://problem/40819319
Reviewed by: @jckarter