Joe Groff 7191b87759 Runtime: Don't touch potentially ObjC unowned-referenced objects to determine their species. ...

ObjC unowned references are backed by an ObjC weak reference which will eagerly deallocate the object when it's strongly released, so in an unknown-refcount situation, we can't safely dereference the object pointer to determine its Swiftness. We can, however, look at the side table of weak references; if there's an entry for this object, then it's reliably an ObjC object (or it's some other object that got allocated in the reclaimed space for the dead object, but that's a race we fundamentally can't win with this broken design). Fixes rdar://problem/18091547 (modulo the aforementioned reallocation race).

Swift SVN r24825

2015-01-29 22:49:45 +00:00

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