IRGen: Work around RemoteMirror bug generating reflection info for empty builtin types. #29037
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…pty builtin types. The RemoteMirror library in shipping versions of macOS/iOS/tvOS/watchOS crashes if the compiler emits a BuiltinTypeDescriptor with size zero. Although this is fixed in top-of-tree RemoteMirror, we want binaries built with the new compiler to still be inspectable when run on older OSes. Generate the metadata as an empty struct with no fields when deploying back to these older platforms, which should be functionally equivalent for most purposes. Fixes rdar://problem/57924984.
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@swift-ci Please test |
slavapestov
approved these changes
Jan 7, 2020
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| import EmptyStruct | ||
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| @_alignment(1) struct EmptyStruct { } |
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Why are you declaring the alignment here?
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The compiler always generates BuiltinTypeDescriptors for types with declared alignment (because the normal layout algorithm would mis-align them), so this is just to exercise that code path. An empty type should not be able to affect the layout of its enclosing aggregate regardless of its supposed alignment, so it should be OK to fall back to an empty struct layout.
mikeash
approved these changes
Jan 7, 2020
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The RemoteMirror library in shipping versions of macOS/iOS/tvOS/watchOS crashes if the compiler
emits a BuiltinTypeDescriptor with size zero. Although this is fixed in top-of-tree RemoteMirror,
we want binaries built with the new compiler to still be inspectable when run on older OSes.
Generate the metadata as an empty struct with no fields when deploying back to these older
platforms, which should be functionally equivalent for most purposes.
Fixes rdar://problem/57924984.