> On Jul 5, 2016, at 9:27 AM, Jens Alfke <j...@mooseyard.com> wrote: > >> On Jul 5, 2016, at 4:36 AM, Jonathan Taylor <jonathan.tay...@glasgow.ac.uk> >> wrote: >> >> It surprises me that I have to write different synthesis code for 32- or >> 64-bit builds > > It’s because they use different Obj-C runtimes. For compatibility reasons, > 32-bit Mac apps still use the old runtime, while 64-bit apps (and all iOS > apps) get to use the new improved runtime. > > One of the differences between the runtimes is how instance variables are > accessed, and I think your particular situation — trying to synthesize a > property backed by an _inherited_ ivar — is an edge case.
A synthesized property must use one of the following types of storage: 1. An ivar in that class that @synthesize creates. 2. An ivar in that class that you defined yourself. @synthesize on 32-bit macOS doesn't support #1. The problem is that 32-bit macOS doesn't support non-fragile ivars. Allowing @synthesize to create ivars would make it too easy to accidentally change ivar layout and break compatibility. No platform allows @synthesize to bind to a superclass ivar. That would make it too easy to accidentally bind to an unrelated superclass ivar when you really wanted to create a new ivar. -- Greg Parker gpar...@apple.com <mailto:gpar...@apple.com> Runtime Wrangler _______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
