iOS objc_msgSend crash, with no report or warning given

Question

I am testing my app out, pushing it pretty hard, and I'm getting it to crash (black screen, image doesn't save, drops back to springboard). However, I get no crash reports logged in the console. When I test using profiler all I get is a message saying the target died, but it gives no clues.

In the organiser I got the device crash logs which gives me this which I believe is telling me I'm sending a message to something I've released (objc-msgSend + 22)? Am I on the right track here?

---

Exception Type:  EXC_BAD_ACCESS (SIGSEGV)
Exception Codes: KERN_INVALID_ADDRESS at 0x576e6f69
Crashed Thread:  0

Thread 0 name:  Dispatch queue: com.apple.main-thread
Thread 0 Crashed:
0   libobjc.A.dylib                 0x34f8ef7e objc_msgSend + 22
1   CoreFoundation                  0x371d7e90 CFRetain + 76
2   CoreFoundation                  0x371e1b74 +[__NSArrayI __new::] + 48
3   CoreFoundation                  0x371e1a8e -[__NSPlaceholderArray initWithObjects:count:] + 294
4   CoreFoundation                  0x371e9394 -[NSArray initWithArray:range:copyItems:] + 756
5   CoreFoundation                  0x371fcd5a +[NSArray arrayWithArray:] + 66
6   AVFoundation                    0x335da766 -[AVCaptureSession outputs] + 146
7   AVFoundation                    0x335de26e -[AVCaptureSession _doDidStop:] + 38
8   AVFoundation                    0x335dfaea -[AVCaptureSession _handleNotification:payload:] + 2002
9   AVFoundation                    0x335d8af6 avcaptureSessionFigRecorderNotification + 1202
10  AVFoundation                    0x335fafd8 AVCMNotificationDispatcherCallback + 184
11  CoreFoundation                  0x3725b7c8 __CFNotificationCenterAddObserver_block_invoke_0 + 116
12  CoreFoundation                  0x3725b540 ___CFXNotificationPost_block_invoke_0 + 64
13  CoreFoundation                  0x371e7090 _CFXNotificationPost + 1400
14  CoreFoundation                  0x371ef1c6 CFNotificationCenterPostNotification + 102
15  CoreMedia                       0x366eeeb0 CMNotificationCenterPostNotification + 112
16  Celestial                       0x374b08a2 FigRecorderRemoteCallbacksServer_NotificationIsPending + 478
17  Celestial                       0x374b06ba _XNotificationIsPending + 54
18  Celestial                       0x374b0678 figrecordercallbacks_server + 92
19  Celestial                       0x374af642 remrec_ClientPortCallBack + 146
20  CoreFoundation                  0x37258f0c __CFMachPortPerform + 356
21  CoreFoundation                  0x3726351c __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ + 32
22  CoreFoundation                  0x372634be __CFRunLoopDoSource1 + 134
23  CoreFoundation                  0x3726230c __CFRunLoopRun + 1364
24  CoreFoundation                  0x371e549e CFRunLoopRunSpecific + 294
25  CoreFoundation                  0x371e5366 CFRunLoopRunInMode + 98
26  AVFoundation                    0x335ef4d0 -[AVRunLoopCondition _waitInMode:untilDate:] + 348
27  AVFoundation                    0x335ef36c -[AVRunLoopCondition waitUntilDate:inMode:] + 20
28  AVFoundation                    0x335dc13a -[AVCaptureSession _stopPreviewing] + 438
29  AVFoundation                    0x335dc2d6 -[AVCaptureSession _setRunning:] + 166
30  AVFoundation                    0x335dbe42 -[AVCaptureSession stopRunning] + 274
31  zApp                            0x0007e1ce 0x79000 + 20942
32  UIKit                           0x30fa5b8e -[UIViewController _setViewAppearState:isAnimating:] + 138
33  UIKit                           0x30fff8a8 -[UIViewController beginAppearanceTransition:animated:] + 184
34  UIKit                           0x310468be -[UIWindowController transition:fromViewController:toViewController:target:didEndSelector:] + 4098
35  UIKit                           0x31045360 -[UIViewController presentViewController:withTransition:completion:] + 3116
36  UIKit                           0x310a06a0 -[UIViewController presentModalViewController:animated:] + 24
37  CoreFoundation                  0x371e93f6 -[NSObject performSelector:withObject:withObject:] + 46
38  UIKit                           0x30f7ee00 -[UIApplication sendAction:to:from:forEvent:] + 56
39  UIKit                           0x30f7edbc -[UIApplication sendAction:toTarget:fromSender:forEvent:] + 24
40  UIKit                           0x30f7ed9a -[UIControl sendAction:to:forEvent:] + 38
41  UIKit                           0x30f7eb0a -[UIControl(Internal) _sendActionsForEvents:withEvent:] + 486
42  UIKit                           0x30f7f442 -[UIControl touchesEnded:withEvent:] + 470
43  UIKit                           0x30f7d924 -[UIWindow _sendTouchesForEvent:] + 312
44  UIKit                           0x30f7d312 -[UIWindow sendEvent:] + 374
45  UIKit                           0x30f6368e -[UIApplication sendEvent:] + 350
46  UIKit                           0x30f62f34 _UIApplicationHandleEvent + 5820
47  GraphicsServices                0x339a5224 PurpleEventCallback + 876
48  CoreFoundation                  0x3726351c __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ + 32
49  CoreFoundation                  0x372634be __CFRunLoopDoSource1 + 134
50  CoreFoundation                  0x3726230c __CFRunLoopRun + 1364
51  CoreFoundation                  0x371e549e CFRunLoopRunSpecific + 294
52  CoreFoundation                  0x371e5366 CFRunLoopRunInMode + 98
53  GraphicsServices                0x339a4432 GSEventRunModal + 130
54  UIKit                           0x30f91cce UIApplicationMain + 1074
55  zApp                            0x0007ffa6 0x79000 + 28582
56  zApp                            0x0007a680 0x79000 + 5760

Answer 1

1. If you suspect that you are overreleasing something, try running your app with NSZombie enabled. (how to enable NSZombie)

2. You can set exception breakpoint to print backtrace in console.

Answer 2

sometimes that happens when you set an object as an observer for notifications, like

[[NSNotificationCenter defaultCenter] addObserver //details

and don't remove it from the observers list when it's released.
the system tries to send a message to it, and the app crashes because it's not there.

try adding

[[NSNotificationCenter defaultCenter] removeObserver:self];

in the dealloc function.
(even if you're working with arc, create a dealloc function, and write that in it).

good luck