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Re: Class gets EXC_BAD_ACCESS only as NSOperation
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Re: Class gets EXC_BAD_ACCESS only as NSOperation


  • Subject: Re: Class gets EXC_BAD_ACCESS only as NSOperation
  • From: Bill Bumgarner <email@hidden>
  • Date: Tue, 24 Mar 2009 09:04:56 -0700

On Mar 24, 2009, at 8:22 AM, James Maxwell wrote:
	int sliceCount = [pitchSlices count];

	float midiEventsToHTM[sliceCount][20];
	float rhythmEventsToHTM[sliceCount][20];
....

The rhythmEventsToHTM array is the one that's getting the bad access error, and I can NSLog the rhythmSlices NSArray without issue. The other thing that seems very weird is that, if I just run the midiEventsToHTM data (i.e., commenting out anything to do with "rhythm") it runs fine in ... the NSOperation thread.

How big is sliceCount?

Threads typically have pretty darned small stack limits. The two float arrays above are both allocated on the stack. Thus, you are reserving (sliceCount * 20 * sizeof(float) * 2) bytes worth of space on the stack.

That the crash goes away when you only run w/one array and that the crash happens always on accessing the second array for the first time in the loop indicates that this is quite likely the case.

In general, creating really large buffers on the stack is risky. Move the arrays to the heap and the problem will quite likely be fixed.

b.bum
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References: 
 >Class gets EXC_BAD_ACCESS only as NSOperation (From: James Maxwell <email@hidden>)
 >Re: Class gets EXC_BAD_ACCESS only as NSOperation (From: Bill Bumgarner <email@hidden>)
 >Re: Class gets EXC_BAD_ACCESS only as NSOperation (From: James Maxwell <email@hidden>)

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