Thanks Jordan! > On 19 Aug 2016, at 23:04, Jordan Rose <jordan_r...@apple.com> wrote: > > We have an old Radar about this, rdar://problem/16754935 > <rdar://problem/16754935>. It's probably just a case we're missing in enum > layout. My guess is that it's because we don't have a whole spare bit in a > RawPointer, but we should be able to pick some up either from alignment or > from ABI knowledge. > > Jordan > >> On Aug 19, 2016, at 13:30, Ole Begemann via swift-dev <swift-dev@swift.org >> <mailto:swift-dev@swift.org>> wrote: >> >> The Character type is essentially defined like this [1]: >> >> struct Character { >> enum Representation { >> // A _StringBuffer whose first grapheme cluster is self. >> // NOTE: may be more than 1 Character long. >> case large(_StringBuffer._Storage) >> case small(Builtin.Int63) >> } >> >> var _representation: Representation >> } >> >> Note the type of the associated value for `case .small`, `Builtin.Int63`. >> Presumably, this is so that the type fits into a single word, including the >> single bit that is needed for the enum case. >> >> However, `MemoryLayout<Character>.size` returns 9. Given the above, I would >> have expected 8 bytes. >> >> Why? Is this a potential optimization that hasn't been implemented? Or am I >> missing something? >> >> Thanks >> Ole >> >> [1]: >> https://github.com/apple/swift/blob/master/stdlib/public/core/Character.swift >> >> <https://github.com/apple/swift/blob/master/stdlib/public/core/Character.swift>
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