Re: Classes incompatible with weak references
Re: Classes incompatible with weak references
- Subject: Re: Classes incompatible with weak references
- From: Kyle Sluder <email@hidden>
- Date: Mon, 13 Aug 2012 15:40:39 -0700
On Mon, Aug 13, 2012, at 02:47 PM, Mike Abdullah wrote:
> An idea I've vaguely wondered about would be turning the isa variable
> into a tagged pointer. If you know nothing is accessing it directly (to
> do so was deprecated with the modern runtime), then, say, the last 4 bits
> of the pointer could be used to record the retain count. Once they're
> used up (for those rare, highly retained objects), you spill over to
> runtime's existing system. Any calls to the runtime to determine an
> object's class would of course be aware of this and ignore those bits.
Unfortunately a lot of code out there accesses isa directly. We used to
be a pretty big offender.
--Kyle Sluder
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