[swift-dev] Combining native and ObjC swift_class_getInstanceExtents entry points

Joe Groff jgroff at apple.com
Wed Dec 23 18:12:02 CST 2015

In the runtime currently, there are two entry points for asking for the size of a class's instances, one for known-native Swift classes, and one for possibly-ObjC classes. It looks like they're only currently used for _debugPrecondition checks in ManagedBuffer's initializers to catch improperly-sized subclasses in debug builds, so I'm wondering whether saving an `isObjC` branch in the known-native case is worth the extra entry point. Any concerns with merging them?


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