> On 5 Jul 2016, at 18:21, Jordan Rose <[email protected]> wrote:
>
> Longstanding bug, rdar://problem/17277899 <rdar://problem/17277899>.
> Surprisingly few people have asked for it.
>
> Jordan
>
Good to know, thanks.
Maybe not enough people know/care about the overheads of weak references?
Since the WWDC Swift performance talk I’ve been more conscious of eliminating
unnecessary retains/releases. That goes for weak references as well, as
(certainly on Obj-C), accessing the value means acquiring a lock to ensure
nobody is trying to zero that reference while you read it:
http://opensource.apple.com//source/objc4/objc4-493.9/runtime/objc-arr.mm
<http://opensource.apple.com//source/objc4/objc4-493.9/runtime/objc-arr.mm>
(see: objc_loadWeak). It’s basically never going to be in contention, but it’s
still more overhead than a simple pointer.
Karl
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