Re: How to implement readonly property
Re: How to implement readonly property
- Subject: Re: How to implement readonly property
- From: Kyle Sluder <email@hidden>
- Date: Sat, 08 Dec 2012 08:35:56 -0800
On Dec 7, 2012, at 8:38 PM, Marco S Hyman <email@hidden> wrote:
> On Dec 7, 2012, at 8:18 PM, Steve Sisak <email@hidden> wrote:
>
>> I'm interested if there are an any issued I'm missing in the Obj-C, @synchronized(self), instance variable case.
>
>
> Your pattern can fail if this line
> _someDictionary = temp;
> isn't atomic.
The real issue with double-checked locking is whether the compiler promises to generate the proper memory barriers such that other threads are guaranteed to see the assignment to _someDictionary *after* the object has been constructed. C makes no such guarantee; other threads might see a non-nil value for _someDictionary before the first thread is done constructing the object.
--Kyle Sluder
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