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we're developing application that has received crash with the stack trace under. While debugging we're unable to find source of the problem for some time now. I'm aware that problem is related to the deallocated object. If someone could point me in direction of class or view or something that is causing the problem I would gladly appreciate. Thanks

Incident Identifier: 
CrashReporter Key:   
Hardware Model:      iPhone9,4
Process:         MYAPP [26490]
Path:            /var/containers/Bundle/Application/2D7244DE-6519-43CB-B3FF-AD502F5921D7/MYAPP.app/MYAPP
Identifier:      com.MYAPP.ios
Version:         1.2.0 (120)
Code Type:       ARM-64
Parent Process:  ??? [1]

Date/Time:       2017-08-24T13:57:21Z
Launch Time:     2017-08-24T13:32:26Z
OS Version:      iPhone OS 10.2.1 (14D27)
Report Version:  104

Exception Type:  SIGABRT
Exception Codes: #0 at 0x18c747014
Crashed Thread:  0

Thread 0 Crashed:
0   libsystem_kernel.dylib               0x000000018c747014 __pthread_kill + 8
1   libsystem_pthread.dylib              0x000000018c80f450 pthread_kill + 108
2   libsystem_c.dylib                    0x000000018c6bb400 abort + 136
3   libsystem_malloc.dylib               0x000000018c78ba5c nanozone_error + 328
4   libsystem_malloc.dylib               0x000000018c78cf18 nano_realloc + 372
5   libsystem_malloc.dylib               0x000000018c77f240 malloc_zone_realloc + 176
6   Foundation                           0x000000018e1ca628 -[NSString quotedStringRepresentation] + 728
7   Foundation                           0x000000018e1aa44c -[NSString _stringRepresentation] + 372
8   CoreFoundation                       0x000000018d6a1f3c -[NSArray descriptionWithLocale:indent:] + 400
9   Foundation                           0x000000018e184af4 _NSDescriptionWithLocaleFunc + 72
10  CoreFoundation                       0x000000018d73a23c __CFStringAppendFormatCore + 7992
11  CoreFoundation                       0x000000018d7382c8 _CFStringCreateWithFormatAndArgumentsAux2 + 240
12  Foundation                           0x000000018e184968 +[NSString stringWithFormat:] + 64
13  UIKit                                0x0000000193f83090 UIViewAlertForUnsatisfiableConstraints + 660
14  Foundation                           0x000000018e1f94cc -[NSISEngine handleUnsatisfiableRowWithHead:body:usingInfeasibilityHandlingBehavior:mutuallyExclusiveConstraints:] + 460
15  Foundation                           0x000000018e1d9df8 -[NSISEngine tryUsingArtificialVariableToAddConstraintWithMarker:rowBody:usingInfeasibilityHandlingBehavior:mutuallyExclusiveConstraints:] + 380
16  Foundation                           0x000000018e1d59c4 -[NSISEngine tryToAddConstraintWithMarker:expression:integralizationAdjustment:mutuallyExclusiveConstraints:] + 684
17  Foundation                           0x000000018e1d55cc -[NSLayoutConstraint _addLoweredExpression:toEngine:integralizationAdjustment:lastLoweredConstantWasRounded:mutuallyExclusiveConstraints:] + 280
18  Foundation                           0x000000018e1d31e0 -[NSLayoutConstraint _addToEngine:integralizationAdjustment:mutuallyExclusiveConstraints:] + 268
19  UIKit                                0x000000019372b2a0 -[UIView(UIConstraintBasedLayout) _layoutEngine_didAddLayoutConstraint:roundingAdjustment:mutuallyExclusiveConstraints:] + 504
20  UIKit                                0x000000019372b068 -[UIView(UIConstraintBasedLayout) _tryToAddConstraintWithoutUpdatingConstraintsArray:roundingAdjustment:mutuallyExclusiveConstraints:] + 32
21  UIKit                                0x000000019372b028 -[UIView(UIConstraintBasedLayout) _tryToAddConstraint:roundingAdjustment:mutuallyExclusiveConstraints:] + 224
22  UIKit                                0x0000000193f77900 -[UIView(UIConstraintBasedLayout) _resetLayoutEngineHostConstraintsForAxis:] + 324
23  Foundation                           0x000000018e1d2d10 -[NSISEngine withBehaviors:performModifications:] + 164
24  UIKit                                0x0000000193f7799c -[UIView(UIConstraintBasedLayout) _resetLayoutEngineHostConstraints] + 68
25  UIKit                                0x000000019376c1f0 -[UIView(UIConstraintBasedLayout) _updateLayoutEngineHostConstraints] + 548
26  UIKit                                0x0000000193f7f1cc -[UIView(AdditionalLayoutSupport) _updateSystemConstraints] + 68
27  UIKit                                0x0000000193f7de80 -[UIView(AdditionalLayoutSupport) _sendUpdateConstraintsIfNecessaryForSecondPass:] + 188
28  UIKit                                0x0000000193f7e1d0 -[UIView(AdditionalLayoutSupport) _updateConstraintsIfNeededCollectingViews:forSecondPass:] + 628
29  Foundation                           0x000000018e1d2d10 -[NSISEngine withBehaviors:performModifications:] + 164
30  UIKit                                0x0000000193f7e41c -[UIView(AdditionalLayoutSupport) _recursiveUpdateConstraintsIfNeededCollectingViews:forSecondPass:] + 116
31  UIKit                                0x0000000193f7e158 -[UIView(AdditionalLayoutSupport) _updateConstraintsIfNeededCollectingViews:forSecondPass:] + 508
32  UIKit                                0x0000000193f7e974 __100-[UIView(AdditionalLayoutSupport) _updateConstraintsIfNeededWithViewForVariableChangeNotifications:]_block_invoke + 80
33  UIKit                                0x0000000193f7db30 -[UIView(AdditionalLayoutSupport) _withUnsatisfiableConstraintsLoggingSuspendedIfEngineDelegateExists:] + 132
34  UIKit                                0x0000000193f7e580 -[UIView(AdditionalLayoutSupport) _updateConstraintsIfNeededWithViewForVariableChangeNotifications:] + 160
35  UIKit                                0x0000000193f7f58c -[UIView(AdditionalLayoutSupport) _updateConstraintsAtEngineLevelIfNeededWithViewForVariableChangeNotifications:] + 368
36  UIKit                                0x00000001939285e4 -[UIView(Hierarchy) _updateConstraintsAsNecessaryAndApplyLayoutFromEngine] + 176
37  UIKit                                0x000000019362bacc -[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 1268
38  QuartzCore                           0x0000000190ad99d8 -[CALayer layoutSublayers] + 144
39  QuartzCore                           0x0000000190ace4cc CA::Layer::layout_if_needed(CA::Transaction*) + 288
40  UIKit                                0x0000000193640500 -[UIView(Hierarchy) layoutBelowIfNeeded] + 1012
41  UIKit                                0x000000019363c7dc +[UIView(Animation) performWithoutAnimation:] + 100
42  UIKit                                0x0000000193971cbc -[UITableView _createPreparedCellForGlobalRow:withIndexPath:willDisplay:] + 1068
43  UIKit                                0x0000000193971d88 -[UITableView _createPreparedCellForGlobalRow:willDisplay:] + 76
44  UIKit                                0x000000019395f320 -[UITableView _updateVisibleCellsNow:isRecursive:] + 2300
45  UIKit                                0x0000000193976dec -[UITableView _performWithCachedTraitCollection:] + 112
46  UIKit                                0x0000000193712de8 -[UITableView layoutSubviews] + 172
47  UIKit                                0x000000019362ba80 -[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 1192
48  QuartzCore                           0x0000000190ad99d8 -[CALayer layoutSublayers] + 144
49  QuartzCore                           0x0000000190ace4cc CA::Layer::layout_if_needed(CA::Transaction*) + 288
50  QuartzCore                           0x0000000190ace38c CA::Layer::layout_and_display_if_needed(CA::Transaction*) + 28
51  QuartzCore                           0x0000000190a4b3e0 CA::Context::commit_transaction(CA::Transaction*) + 248
52  QuartzCore                           0x0000000190a72a68 CA::Transaction::commit() + 508
53  QuartzCore                           0x0000000190a73488 CA::Transaction::observer_callback(__CFRunLoopObserver*, unsigned long, void*) + 116
54  CoreFoundation                       0x000000018d7260c0 __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 28
55  CoreFoundation                       0x000000018d723cf0 __CFRunLoopDoObservers + 368
56  CoreFoundation                       0x000000018d724180 __CFRunLoopRun + 1020
57  CoreFoundation                       0x000000018d6522b8 CFRunLoopRunSpecific + 440
58  GraphicsServices                     0x000000018f106198 GSEventRunModal + 176
59  UIKit                                0x00000001936997fc -[UIApplication _run] + 680
60  UIKit                                0x0000000193694534 UIApplicationMain + 204
61  MYAPP                                0x000000010003ad3c main (AppDelegate.swift:26)
62  ???                                  0x000000018c6355b8 0x0 + 0

Thread 1:
0   libsystem_kernel.dylib               0x000000018c729188 mach_msg_trap + 8
1   CoreFoundation                       0x000000018d7265d0 __CFRunLoopServiceMachPort + 188
2   CoreFoundation                       0x000000018d7241ec __CFRunLoopRun + 1128
3   CoreFoundation                       0x000000018d6522b8 CFRunLoopRunSpecific + 440
4   Foundation                           0x000000018e18f26c -[NSRunLoop(NSRunLoop) runMode:beforeDate:] + 300
5   Foundation                           0x000000018e1afdd0 -[NSRunLoop(NSRunLoop) runUntilDate:] + 92
6   UIKit                                0x000000019400dc38 -[UIEventFetcher threadMain] + 132
7   Foundation                           0x000000018e28ce68 __NSThread__start__ + 1020
8   libsystem_pthread.dylib              0x000000018c80d850 _pthread_body + 236
9   libsystem_pthread.dylib              0x000000018c80d760 _pthread_start + 280
10  libsystem_pthread.dylib              0x000000018c80ad94 thread_start + 0

Thread 2:
0   libsystem_kernel.dylib               0x000000018c729188 mach_msg_trap + 8
1   CoreFoundation                       0x000000018d7265d0 __CFRunLoopServiceMachPort + 188
2   CoreFoundation                       0x000000018d7241ec __CFRunLoopRun + 1128
3   CoreFoundation                       0x000000018d6522b8 CFRunLoopRunSpecific + 440
4   CFNetwork                            0x000000018de57a70 +[NSURLConnection(Loader) _resourceLoadLoop:] + 332
5   Foundation                           0x000000018e28ce68 __NSThread__start__ + 1020
6   libsystem_pthread.dylib              0x000000018c80d850 _pthread_body + 236
7   libsystem_pthread.dylib              0x000000018c80d760 _pthread_start + 280
8   libsystem_pthread.dylib              0x000000018c80ad94 thread_start + 0

Thread 3:
0   libsystem_kernel.dylib               0x000000018c729188 mach_msg_trap + 8
1   CoreFoundation                       0x000000018d7265d0 __CFRunLoopServiceMachPort + 188
2   CoreFoundation                       0x000000018d7241ec __CFRunLoopRun + 1128
3   CoreFoundation                       0x000000018d6522b8 CFRunLoopRunSpecific + 440
4   CoreFoundation                       0x000000018d7340ec _legacyStreamRunLoop_workThread + 264
5   libsystem_pthread.dylib              0x000000018c80d850 _pthread_body + 236
6   libsystem_pthread.dylib              0x000000018c80d760 _pthread_start + 280
7   libsystem_pthread.dylib              0x000000018c80ad94 thread_start + 0

Thread 4:
0   libsystem_kernel.dylib               0x000000018c74723c __select + 8
1   libsystem_pthread.dylib              0x000000018c80d850 _pthread_body + 236
2   libsystem_pthread.dylib              0x000000018c80d760 _pthread_start + 280
3   libsystem_pthread.dylib              0x000000018c80ad94 thread_start + 0

Thread 5:
0   libsystem_kernel.dylib               0x000000018c729188 mach_msg_trap + 8
1   CoreFoundation                       0x000000018d7265d0 __CFRunLoopServiceMachPort + 188
2   CoreFoundation                       0x000000018d7241ec __CFRunLoopRun + 1128
3   CoreFoundation                       0x000000018d6522b8 CFRunLoopRunSpecific + 440
4   AVFAudio                             0x00000001a7157d24 GenericRunLoopThread::Entry(void*) + 160
5   AVFAudio                             0x00000001a717dd9c CAPThread::Entry(CAPThread*) + 80
6   libsystem_pthread.dylib              0x000000018c80d850 _pthread_body + 236
7   libsystem_pthread.dylib              0x000000018c80d760 _pthread_start + 280
8   libsystem_pthread.dylib              0x000000018c80ad94 thread_start + 0

Thread 6:
0   libsystem_kernel.dylib               0x000000018c746e1c __psynch_cvwait + 8
1   TwilioChatClient                     0x00000001021480ac 0x102110000 + 229548
2   TwilioChatClient                     0x0000000102151c2c 0x102110000 + 269356
3   TwilioChatClient                     0x0000000102162c8c 0x102110000 + 339084
4   TwilioChatClient                     0x000000010215f7fc 0x102110000 + 325628
5   libsystem_pthread.dylib              0x000000018c80d850 _pthread_body + 236
6   libsystem_pthread.dylib              0x000000018c80d760 _pthread_start + 280
7   libsystem_pthread.dylib              0x000000018c80ad94 thread_start + 0

Thread 7:
0   libsystem_kernel.dylib               0x000000018c746e1c __psynch_cvwait + 8
1   TwilioChatClient                     0x000000010224f834 0x102110000 + 1308724
2   TwilioChatClient                     0x000000010224f614 0x102110000 + 1308180
3   TwilioChatClient                     0x000000010224f2f8 0x102110000 + 1307384
4   libsystem_pthread.dylib              0x000000018c80d850 _pthread_body + 236
5   libsystem_pthread.dylib              0x000000018c80d760 _pthread_start + 280
6   libsystem_pthread.dylib              0x000000018c80ad94 thread_start + 0

Thread 8:
0   libsystem_kernel.dylib               0x000000018c746e1c __psynch_cvwait + 8
1   TwilioChatClient                     0x000000010224f834 0x102110000 + 1308724
2   TwilioChatClient                     0x000000010224f614 0x102110000 + 1308180
3   TwilioChatClient                     0x000000010224f2f8 0x102110000 + 1307384
4   libsystem_pthread.dylib              0x000000018c80d850 _pthread_body + 236
5   libsystem_pthread.dylib              0x000000018c80d760 _pthread_start + 280
6   libsystem_pthread.dylib              0x000000018c80ad94 thread_start + 0

Thread 9:
0   libsystem_kernel.dylib               0x000000018c746e1c __psynch_cvwait + 8
1   TwilioChatClient                     0x000000010224f834 0x102110000 + 1308724
2   TwilioChatClient                     0x000000010224f614 0x102110000 + 1308180
3   TwilioChatClient                     0x000000010224f2f8 0x102110000 + 1307384
4   libsystem_pthread.dylib              0x000000018c80d850 _pthread_body + 236
5   libsystem_pthread.dylib              0x000000018c80d760 _pthread_start + 280
6   libsystem_pthread.dylib              0x000000018c80ad94 thread_start + 0

Thread 10:
0   libsystem_kernel.dylib               0x000000018c746e1c __psynch_cvwait + 8
1   TwilioChatClient                     0x000000010224f834 0x102110000 + 1308724
2   TwilioChatClient                     0x000000010224f614 0x102110000 + 1308180
3   TwilioChatClient                     0x000000010224f2f8 0x102110000 + 1307384
4   libsystem_pthread.dylib              0x000000018c80d850 _pthread_body + 236
5   libsystem_pthread.dylib              0x000000018c80d760 _pthread_start + 280
6   libsystem_pthread.dylib              0x000000018c80ad94 thread_start + 0

Thread 11:
0   libsystem_kernel.dylib               0x000000018c746e1c __psynch_cvwait + 8
1   TwilioChatClient                     0x000000010224f834 0x102110000 + 1308724
2   TwilioChatClient                     0x000000010224f614 0x102110000 + 1308180
3   TwilioChatClient                     0x000000010224f2f8 0x102110000 + 1307384
4   libsystem_pthread.dylib              0x000000018c80d850 _pthread_body + 236
5   libsystem_pthread.dylib              0x000000018c80d760 _pthread_start + 280
6   libsystem_pthread.dylib              0x000000018c80ad94 thread_start + 0

Thread 12:
0   libsystem_kernel.dylib               0x000000018c746e1c __psynch_cvwait + 8
1   TwilioChatClient                     0x000000010224f834 0x102110000 + 1308724
2   TwilioChatClient                     0x000000010224f614 0x102110000 + 1308180
3   TwilioChatClient                     0x000000010224f2f8 0x102110000 + 1307384
4   libsystem_pthread.dylib              0x000000018c80d850 _pthread_body + 236
5   libsystem_pthread.dylib              0x000000018c80d760 _pthread_start + 280
6   libsystem_pthread.dylib              0x000000018c80ad94 thread_start + 0

Thread 13:
0   libsystem_kernel.dylib               0x000000018c746e1c __psynch_cvwait + 8
1   TwilioChatClient                     0x000000010224f834 0x102110000 + 1308724
2   TwilioChatClient                     0x000000010224f614 0x102110000 + 1308180
3   TwilioChatClient                     0x000000010224f2f8 0x102110000 + 1307384
4   libsystem_pthread.dylib              0x000000018c80d850 _pthread_body + 236
5   libsystem_pthread.dylib              0x000000018c80d760 _pthread_start + 280
6   libsystem_pthread.dylib              0x000000018c80ad94 thread_start + 0

Thread 14:
0   libsystem_kernel.dylib               0x000000018c746e1c __psynch_cvwait + 8
1   TwilioChatClient                     0x000000010224f834 0x102110000 + 1308724
2   TwilioChatClient                     0x000000010224f614 0x102110000 + 1308180
3   TwilioChatClient                     0x000000010224f2f8 0x102110000 + 1307384
4   libsystem_pthread.dylib              0x000000018c80d850 _pthread_body + 236
5   libsystem_pthread.dylib              0x000000018c80d760 _pthread_start + 280
6   libsystem_pthread.dylib              0x000000018c80ad94 thread_start + 0

Thread 15:
0   libsystem_kernel.dylib               0x000000018c746e1c __psynch_cvwait + 8
1   TwilioChatClient                     0x000000010224f834 0x102110000 + 1308724
2   TwilioChatClient                     0x000000010224f614 0x102110000 + 1308180
3   TwilioChatClient                     0x000000010224f2f8 0x102110000 + 1307384
4   libsystem_pthread.dylib              0x000000018c80d850 _pthread_body + 236
5   libsystem_pthread.dylib              0x000000018c80d760 _pthread_start + 280
6   libsystem_pthread.dylib              0x000000018c80ad94 thread_start + 0

Thread 16:
0   libsystem_kernel.dylib               0x000000018c746e1c __psynch_cvwait + 8
1   TwilioChatClient                     0x000000010224f834 0x102110000 + 1308724
2   TwilioChatClient                     0x000000010224f614 0x102110000 + 1308180
3   TwilioChatClient                     0x000000010224f2f8 0x102110000 + 1307384
4   libsystem_pthread.dylib              0x000000018c80d850 _pthread_body + 236
5   libsystem_pthread.dylib              0x000000018c80d760 _pthread_start + 280
6   libsystem_pthread.dylib              0x000000018c80ad94 thread_start + 0

Thread 17:
0   libsystem_kernel.dylib               0x000000018c746e1c __psynch_cvwait + 8
1   TwilioChatClient                     0x000000010224f834 0x102110000 + 1308724
2   TwilioChatClient                     0x000000010224f614 0x102110000 + 1308180
3   TwilioChatClient                     0x000000010224f2f8 0x102110000 + 1307384
4   libsystem_pthread.dylib              0x000000018c80d850 _pthread_body + 236
5   libsystem_pthread.dylib              0x000000018c80d760 _pthread_start + 280
6   libsystem_pthread.dylib              0x000000018c80ad94 thread_start + 0

Thread 18:
0   libsystem_kernel.dylib               0x000000018c72d64c kevent + 8
1   TwilioChatClient                     0x000000010224f88c 0x102110000 + 1308812
2   TwilioChatClient                     0x000000010224f614 0x102110000 + 1308180
3   TwilioChatClient                     0x000000010224f2f8 0x102110000 + 1307384
4   libsystem_pthread.dylib              0x000000018c80d850 _pthread_body + 236
5   libsystem_pthread.dylib              0x000000018c80d760 _pthread_start + 280
6   libsystem_pthread.dylib              0x000000018c80ad94 thread_start + 0

Thread 19:
0   libsystem_kernel.dylib               0x000000018c746e1c __psynch_cvwait + 8
1   TwilioChatClient                     0x000000010224f834 0x102110000 + 1308724
2   TwilioChatClient                     0x000000010224f614 0x102110000 + 1308180
3   TwilioChatClient                     0x000000010224f2f8 0x102110000 + 1307384
4   libsystem_pthread.dylib              0x000000018c80d850 _pthread_body + 236
5   libsystem_pthread.dylib              0x000000018c80d760 _pthread_start + 280
6   libsystem_pthread.dylib              0x000000018c80ad94 thread_start + 0



Thread 0 crashed with ARM-64 Thread State:
    pc: 0x000000018c747014     fp: 0x000000016fdcd430     sp: 0x000000016fdcd410     x0: 0x0000000000000000 
    x1: 0x0000000000000000     x2: 0x0000000000000000     x3: 0x0000000000000000     x4: 0x0000000000000000 
    x5: 0x0000000000000000     x6: 0x0000000000000001     x7: 0x0000000000000000     x8: 0x0000000008000000 
    x9: 0x0000000004000000    x10: 0x0000000000000000    x11: 0x000000000000000a    x12: 0x0000000000000000 
   x13: 0x0000000000000035    x14: 0x0034003100780030    x15: 0x0037003700300033    x16: 0x0000000000000148 
   x17: 0x000000018d65ca34    x18: 0x0000000000000000    x19: 0x0000000000000006    x20: 0x00000001b2f01c40 
   x21: 0x0000000000000001    x22: 0x0000000103164000    x23: 0x0000000177f1c1c0    x24: 0x0000000000000000 
   x25: 0xbaddc0dedeadbead    x26: 0x000000000000ffff    x27: 0x0000000000000087    x28: 0x000000000000005c 
    lr: 0x000000018c80f450   cpsr: 0x0000000000000000 

Link Register Analysis:
  Symbol: pthread_kill + 108
  Description: We have determined that the link register (lr) is very likely to contain the return address of frame #0's calling function, and have inserted it into the crashing thread's backtrace as frame #1 to aid in analysis. This determination was made by applying a heuristic to determine whether the crashing function was likely to have created a new stack frame at the time of the crash.
  Type: 1

If it's needed I can upload rest of stack trace. There is a limit under body length of post.

Baki
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  • Do you use Visual Contraints? – Larme Aug 24 '17 at 20:04
  • Yeah, we're using them. Are they creating issues? – Baki Aug 24 '17 at 20:30
  • There is a lot of calls about contraints, and the fact that a `[NSArray descriptionWithLocale:indent:]` is called, made my think when the debugger prints an array of contraints that is creating an issue. Can you reproduce yourself the crash with XCode debugger plugged to the device? – Larme Aug 24 '17 at 20:33
  • Unfortunately I cannot reproduce it. :( – Baki Aug 24 '17 at 21:07
  • You should enable NSJombie https://stackoverflow.com/questions/5386160/how-to-enable-nszombie-in-xcode for detect actual errror – Govaadiyo Sep 06 '17 at 12:40

1 Answers1

2

I can't give you a precise diagnosis but perhaps these observations may help narrow down the realm of possibilities.

1) The crash is not in your code (at least not directly) since the stack trace only contains system/UIKit calls.

2) The error occurs in the preparation of a string which is seemingly an error (alert) message to report a layout constraint issue.

3) The calls preceding the attempt to show an alert indicate that layout constraints are attempting to adjust for rounding of coordinates to integer values.

4) The layout being processed is in the preparation of a UITableView cell. But it is likely not in a call to your code (i.e. not in dequeuing a custom UITableViewCell). So this would be a static or standard cell in the tableview.

5) The pattern of layout processing seems to indicate that a "proportional" constraint is involved and that the sizes and ratio produce a value that exceeds the size of an integer. The fact that there is an error in preparing an error message is what leads me to believe this may be related to invalid numerical values. Note that there could be other reasons for the string to fail but the context of the call would be consistent with large numbers.

6) The layout process is triggered by a value observer which does not call to your code (or at least doesn't seem to). The trigger of the issue (user action) is likely a UI altering event that would/should be processed automatically (such as a device orientation change). Since this happened on an iPhone, you can exclude split screen issues (which you could only get on an iPad). Other possible events would depend on what your application does.

With this, you could probably narrow down the possibilities to a view that has a UITableview with static cells. These cells would have to contain some subviews that use proportional constraints (e.g. aspect ratio, relative height/width). Note that the names of the Layout constraint functions suggest that this could be related internal constraints set automatically between the tableView cells and the tableview. Event if that is the case, at some point at least one of your own constraints will be involved.

If you're application doesn't have a large number of tableviews, you can probably focus your investigation on the "automatic" reactions to user actions that can be performed on the UITableviews that you do have. Given that this happens on an iPhone, you will also want to examine transitions back from modal views through unwind segues or dismiss(). iPhones and iPods often release some of the UI elements from the presenting VC which may cause unwanted behaviour in some cases.

Hope this helps.

Alain T.
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  • Hi Alain, thank you for detailed report, I'll take a look at this and let you know results. – Baki Sep 07 '17 at 07:34
  • Hi Alain, this gave me a good understanding of where error is/could occur, since this is something that happens time from time, I have updated some layout constraints and now I'm waiting for the feedback on this one. thank you – Baki Sep 11 '17 at 06:36