title: iOS 8 crash - objc_msgSend() selector name: respondsToSelector:
body: <p>I have the following crash report. It only happens on iOS 8. I know exactly how to reproduce it but cannot for the life of me figure out where the problem is in my code. When I use a breakpoint and try to step through the app, the crash doesn't happen. How can I find where the issue is in my app?</p>
  
  <pre><code>Exception Type:  SIGSEGV
  Exception Codes: SEGV_ACCERR at 0x10
  Crashed Thread:  0
  
      Application Specific Information:
  objc_msgSend() selector name: respondsToSelector:
  
  Thread 0 Crashed:
  0   libobjc.A.dylib                      0x00000001974b3bd0 objc_msgSend + 16
  1   UIKit                                0x000000018ab960f4 -[UIToolbar _didMoveFromWindow:toWindow:] + 108
  2   UIKit                                0x000000018aa30d44 -[UIView(Internal) _didMoveFromWindow:toWindow:] + 700
  3   UIKit                                0x000000018aa30d44 -[UIView(Internal) _didMoveFromWindow:toWindow:] + 700
  4   UIKit                                0x000000018aa30d44 -[UIView(Internal) _didMoveFromWindow:toWindow:] + 700
  5   UIKit                                0x000000018aa303dc __45-[UIView(Hierarchy) _postMovedFromSuperview:]_block_invoke + 140
  6   UIKit                                0x000000018aa302bc -[UIView(Hierarchy) _postMovedFromSuperview:] + 480
  7   UIKit                                0x000000018aa3c0b0 -[UIView(Internal) _addSubview:positioned:relativeTo:] + 1788
  8   UIKit                                0x000000018ac1c368 __53-[_UINavigationParallaxTransition animateTransition:]_block_invoke + 1432
  9   UIKit                                0x000000018aa42b6c +[UIView(Animation) performWithoutAnimation:] + 84
  10  UIKit                                0x000000018ac1bb2c -[_UINavigationParallaxTransition animateTransition:] + 852
  11  UIKit                                0x000000018abd7b70 -[UINavigationController _startCustomTransition:] + 3032
  12  UIKit                                0x000000018aae9ef0 -[UINavigationController _startDeferredTransitionIfNeeded:] + 464
  13  UIKit                                0x000000018aae9cbc -[UINavigationController __viewWillLayoutSubviews] + 52
  14  UIKit                                0x000000018aae9c3c -[UILayoutContainerView layoutSubviews] + 196
  15  UIKit                                0x000000018aa31760 -[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 576
  16  QuartzCore                           0x000000018a379e1c -[CALayer layoutSublayers] + 148
  17  QuartzCore                           0x000000018a374884 CA::Layer::layout_if_needed(CA::Transaction*) + 316
  18  QuartzCore                           0x000000018a374728 CA::Layer::layout_and_display_if_needed(CA::Transaction*) + 28
  19  QuartzCore                           0x000000018a373ebc CA::Context::commit_transaction(CA::Transaction*) + 272
  20  QuartzCore                           0x000000018a373c3c CA::Transaction::commit() + 524
  21  QuartzCore                           0x000000018a36d364 CA::Transaction::observer_callback(__CFRunLoopObserver*, unsigned long, void*) + 76
  22  CoreFoundation                       0x0000000185fac2a4 __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 28
  23  CoreFoundation                       0x0000000185fa9230 __CFRunLoopDoObservers + 356
  24  CoreFoundation                       0x0000000185fa9610 __CFRunLoopRun + 832
  25  CoreFoundation                       0x0000000185ed52d4 CFRunLoopRunSpecific + 392
  26  GraphicsServices                     0x000000018f59b6fc GSEventRunModal + 164
  27  UIKit                                0x000000018aa9afac UIApplicationMain + 1484
  28  MyAppName                            0x00000001001b8ae0 main (main.m:16)
  29  libdyld.dylib                        0x0000000197b1ea08 start + 0
  </code></pre>