How can I fix an app crash which is irreproducible? Crash report and console log attached

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My ios app used a lot of Core Data and Core Animation. Due to multi-threading, it sometimes crashed in an irreproducible fashion. Can any programming ninja help on looking into this crash issues? I don't have an idea where I had an empty mutablearray being called objectAtIndex.

Also I don't know how to track where the CGContext errors happened. Since it's not an NSException, I don't how to set a breakpoint there. Can anyone teach me how to set breakpoint whenever CGContext errors come up?

My console log:

  May 30 09:12:39 Dons-iPod-touch larklife[6914] <Warning>: EventsViewController.m              680: indexPath in finish block<NSIndexPath 0x1f18fe60> 2 indexes [1, 0]

  May 30 09:12:39 Dons-iPod-touch larklife[6914] <Error>: CGContextSetFillColorWithColor: invalid context 0x0

  May 30 09:12:39 Dons-iPod-touch larklife[6914] <Error>: CGContextSaveGState: invalid context 0x0

  May 30 09:12:39 Dons-iPod-touch larklife[6914] <Error>: CGContextSetFlatness: invalid context 0x0

  May 30 09:12:39 Dons-iPod-touch larklife[6914] <Error>: CGContextAddPath: invalid context 0x0

  May 30 09:12:39 Dons-iPod-touch larklife[6914] <Error>: CGContextDrawPath: invalid context 0x0

  May 30 09:12:39 Dons-iPod-touch larklife[6914] <Error>: CGContextRestoreGState: invalid context 0x0

  May 30 09:12:40 Dons-iPod-touch larklife[6914] <Error>: *** Terminating app due to    uncaught exception 'NSRangeException', reason: '*** -[__NSArrayM objectAtIndex:]: index 0 beyond bounds for empty array'
*** First throw call stack:
(0x330e92a3 0x3ad6797f 0x33034b75 0x32f5bc0d 0xeb555 0xe5c9b 0x106549 0xe1521  0xebcad 0xde557 0xe4589 0xe5275 0x24b06d 0x339f7277 0x330be5df 0x330be291 0x330bcf01 0x3302febd 0x3302fd49 0x36be22eb 0x34f45301 0x206fd 0x3b19eb20)

Crash report:

Incident Identifier: C18D4D70-7157-4456-900B-077BDE488A70
CrashReporter Key:   7531fede04c2aea4fcfb40a804a8e2fdb0a4cb79
Hardware Model:      iPod4,1
Process:         larklife [6914]
Path:            /var/mobile/Applications/30FAAA4E-1FC4-452F-82E2- 1E706A34A0B8/larklife.app/larklife
Identifier:      larklife
Version:         ??? (???)
Code Type:       ARM (Native)
Parent Process:  launchd [1]

Date/Time:       2013-05-30 09:12:40.483 -0700
OS Version:      iOS 6.1.3 (10B329)
Report Version:  104

Exception Type:  EXC_CRASH (SIGABRT)
Exception Codes: 0x0000000000000000, 0x0000000000000000
Crashed Thread:  0

Last Exception Backtrace:
0   CoreFoundation                  0x330e929e __exceptionPreprocess + 158
1   libobjc.A.dylib                 0x3ad6797a objc_exception_throw + 26
2   CoreFoundation                  0x33034b70 -[__NSArrayM objectAtIndex:] + 160
3   CoreData                        0x32f5bc08 -[NSFetchedResultsController objectAtIndexPath:] + 236
4   larklife                        0x000eb550 0x19000 + 861520
5   larklife                        0x000e5c96 0x19000 + 838806
6   larklife                        0x00106544 0x19000 + 972100
7   larklife                        0x000e151c 0x19000 + 820508
8   larklife                        0x000ebca8 0x19000 + 863400
9   larklife                        0x000de552 0x19000 + 808274
10  larklife                        0x000e4584 0x19000 + 832900
11  larklife                        0x000e5270 0x19000 + 836208
12  larklife                        0x0024b068 0x19000 + 2302056
13  Foundation                      0x339f7272 __NSFireDelayedPerform + 446
14  CoreFoundation                  0x330be5da __CFRUNLOOP_IS_CALLING_OUT_TO_A_TIMER_CALLBACK_FUNCTION__ + 10
15  CoreFoundation                  0x330be28c __CFRunLoopDoTimer + 268
16  CoreFoundation                  0x330bcefc __CFRunLoopRun + 1228
17  CoreFoundation                  0x3302feb8 CFRunLoopRunSpecific + 352
18  CoreFoundation                  0x3302fd44 CFRunLoopRunInMode + 100
19  GraphicsServices                0x36be22e6 GSEventRunModal + 70
20  UIKit                           0x34f452fc UIApplicationMain + 1116
21  larklife                        0x000206f8 0x19000 + 30456
22  libdyld.dylib                   0x3b19eb1c start + 0


Thread 0 name:  Dispatch queue: com.apple.main-thread
Thread 0 Crashed:
0   libsystem_kernel.dylib          0x3b265350 __pthread_kill + 8
1   libsystem_c.dylib               0x3b1dc11e pthread_kill + 54
2   libsystem_c.dylib               0x3b21896e abort + 90
3   libc++abi.dylib                 0x3a7b6d4a abort_message + 70
4   libc++abi.dylib                 0x3a7b3ff4 _ZL17default_terminatev + 20
5   libobjc.A.dylib                 0x3ad67a74 _ZL15_objc_terminatev + 144
6   libc++abi.dylib                 0x3a7b4078 _ZL19safe_handler_callerPFvvE + 76
7   libc++abi.dylib                 0x3a7b4110 std::terminate() + 16
8   libc++abi.dylib                 0x3a7b5594 __cxa_rethrow + 84
9   libobjc.A.dylib                 0x3ad679cc objc_exception_rethrow + 8
10  CoreFoundation                  0x3302ff1c CFRunLoopRunSpecific + 452
11  CoreFoundation                  0x3302fd44 CFRunLoopRunInMode + 100
12  GraphicsServices                0x36be22e6 GSEventRunModal + 70
13  UIKit                           0x34f452fc UIApplicationMain + 1116
14  larklife                        0x000206f8 0x19000 + 30456
15  libdyld.dylib                   0x3b19eb1c start + 0

Thread 1 name:  Dispatch queue: com.apple.libdispatch-manager
Thread 1:
0   libsystem_kernel.dylib          0x3b255648 kevent64 + 24
1   libdispatch.dylib               0x3b18e4ec _dispatch_mgr_invoke + 792
2   libdispatch.dylib               0x3b180df4 _dispatch_mgr_thread$VARIANT$up + 32

Thread 2 name:  WebThread
Thread 2:
0   libsystem_kernel.dylib          0x3b254eb4 mach_msg_trap + 20
1   libsystem_kernel.dylib          0x3b255048 mach_msg + 36
2   CoreFoundation                  0x330be040 __CFRunLoopServiceMachPort + 124
3   CoreFoundation                  0x330bcd9e __CFRunLoopRun + 878
4   CoreFoundation                  0x3302feb8 CFRunLoopRunSpecific + 352
5   CoreFoundation                  0x3302fd44 CFRunLoopRunInMode + 100
6   WebCore                         0x3901d500 _ZL12RunWebThreadPv + 440
7   libsystem_c.dylib               0x3b1be30e _pthread_start + 306
8   libsystem_c.dylib               0x3b1be1d4 thread_start + 4

Thread 3:
0   libsystem_kernel.dylib          0x3b265d98 __workq_kernreturn + 8
1   libsystem_c.dylib               0x3b1b3cf6 _pthread_workq_return + 14
2   libsystem_c.dylib               0x3b1b3a12 _pthread_wqthread + 362
3   libsystem_c.dylib               0x3b1b38a0 start_wqthread + 4

Thread 4:
0   libsystem_kernel.dylib          0x3b265d98 __workq_kernreturn + 8
1   libsystem_c.dylib               0x3b1b3cf6 _pthread_workq_return + 14
2   libsystem_c.dylib               0x3b1b3a12 _pthread_wqthread + 362
3   libsystem_c.dylib               0x3b1b38a0 start_wqthread + 4

Thread 5 name:  com.apple.NSURLConnectionLoader
Thread 5:
0   libsystem_kernel.dylib          0x3b254eb4 mach_msg_trap + 20
1   libsystem_kernel.dylib          0x3b255048 mach_msg + 36
2   CoreFoundation                  0x330be040 __CFRunLoopServiceMachPort + 124
3   CoreFoundation                  0x330bcd9e __CFRunLoopRun + 878
4   CoreFoundation                  0x3302feb8 CFRunLoopRunSpecific + 352
5   CoreFoundation                  0x3302fd44 CFRunLoopRunInMode + 100
6   Foundation                      0x3397c3d0 +[NSURLConnection(Loader) _resourceLoadLoop:] + 304
7   Foundation                      0x339ffe80 __NSThread__main__ + 968
8   libsystem_c.dylib               0x3b1be30e _pthread_start + 306
9   libsystem_c.dylib               0x3b1be1d4 thread_start + 4

Thread 6 name:  com.apple.CFSocket.private
Thread 6:
0   libsystem_kernel.dylib          0x3b265594 __select + 20
1   CoreFoundation                  0x330c21f2 __CFSocketManager + 674
2   libsystem_c.dylib               0x3b1be30e _pthread_start + 306
3   libsystem_c.dylib               0x3b1be1d4 thread_start + 4

Thread 7 name:  Dispatch queue: NSManagedObjectContext Queue
Thread 7:
0   CoreData                        0x32ebe19c _kvcPropertysPrimitiveSetters + 0
1   CoreData                        0x32edc700 _sharedIMPL_setvfk_core + 44
2   larklife                        0x000ba374 0x19000 + 660340
3   CoreData                        0x32ed0bf0 _PF_Handler_Public_SetProperty + 88
4   CoreData                        0x32ed312a -[NSManagedObject setValue:forKey:] + 86
5   larklife                        0x002314f2 0x19000 + 2196722
6   larklife                        0x00060ed8 0x19000 + 294616
7   CoreFoundation                  0x330dd99e __NSArrayEnumerate + 394
8   CoreFoundation                  0x3303fb66 -[NSArray enumerateObjectsWithOptions:usingBlock:] + 58
9   larklife                        0x00060d44 0x19000 + 294212
10  larklife                        0x0005d204 0x19000 + 279044
11  CoreData                        0x32ee6072 developerSubmittedBlockToNSManagedObjectContextPerform_privateasync + 66
12  libdispatch.dylib               0x3b17e996 _dispatch_queue_drain$VARIANT$up + 142
13  libdispatch.dylib               0x3b17e890 _dispatch_queue_invoke$VARIANT$up + 32
14  libdispatch.dylib               0x3b18d212 _dispatch_root_queue_drain + 190
15  libdispatch.dylib               0x3b18d3b4 _dispatch_worker_thread2 + 80
16  libsystem_c.dylib               0x3b1b3a0e _pthread_wqthread + 358
17  libsystem_c.dylib               0x3b1b38a0 start_wqthread + 4

Thread 0 crashed with ARM Thread State (32-bit):
    r0: 0x00000000    r1: 0x00000000      r2: 0x00000000      r3: 0x3cd16534
    r4: 0x00000006    r5: 0x3cd16b88      r6: 0x1f483d54      r7: 0x2fde7a04
    r8: 0x1f483d30    r9: 0x00000400     r10: 0x00000000     r11: 0x00000000
    ip: 0x00000148    sp: 0x2fde79f8      lr: 0x3b1dc123      pc: 0x3b265350
  cpsr: 0x00080010
ios
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asked on Stack Overflow Jun 3, 2013 by YoungLion • edited Jun 3, 2013 by Adrian P

3 Answers

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You error message said:

[__NSArrayM objectAtIndex:]: index 0 beyond bounds

. The reason probably is that using an NSMUtableArray (__NSArrayM) is not thread safe, see here.
Without any code provided, I suggest that you read the Threading Programming Guide cited very carefully, and correct your code accordingly.

answered on Stack Overflow Jun 3, 2013 by Reinhard Männer
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In events viewcontroller.m the array you used was empty at index 0 and 1. Check the 160 and 236 of your code for the error that accrued. It was definitely related to fetching data. It seems that it could not fetch data from you store. It is what i gather without seeing the actual code.

answered on Stack Overflow Jun 3, 2013 by Adrian P • edited Jun 3, 2013 by Adrian P
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You trying to get the first element of an empty array, which produce the crash and the exception is self explanatory.

you can debug the array when the app crashes using the po command (print object):

po the_array_object

Also, make sure you set breakpoints ON in the breakpoint navigator in order to get better debugging stuck from the compiler.

answered on Stack Overflow Jun 3, 2013 by Malloc

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