Re: crash on altering NSMutableArray
Re: crash on altering NSMutableArray
- Subject: Re: crash on altering NSMutableArray
- From: Kyle Sluder <email@hidden>
- Date: Sat, 1 May 2010 17:17:00 -0700
On May 1, 2010, at 5:04 PM, James Maxwell <email@hidden>
wrote:
I'm having a crash when trying to remove the last item in an
NSMutableArray.
The app is a pretty complex system, and runs its two main processes
in consecutively executed blocks.
The blocks are run using dispatch_apply, on the global queue. The
operation that's trying to
access the NSArray is, I think, within the first block... but
honestly, I can't be totally sure, as
I don't know exactly why the app is crashing.
Yes you do. You have a debugger and a stack trace.
I guess what I'm wondering is whether there's some fool-proof way of
protecting that NSArray from being read and changed simultaneously?
I tried making the array nonatomic, but that didn't solve the problem.
Of note is the fact that this is directly related to processing
load, so I'm assuming it has to do
with some timing thing -- as the app gets more loaded down, things
get sketchy.
The concept you're looking for is thread safety. It is, in general, a
Very Hard Problem.
I know this isn't a great description of the problem, but hopefully
someone has some thoughts to share.
If you have a crash, the only two useful pieces of information are the
source code and the stack trace. Anything else risks misinterpretation
and therefore wasted time.
--Kyle Sluder
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