title: How to know where crash for postNotificationName:object:userInfo
body: <p>Is there some method to know crash reason in Xcode 4.6?</p>
  
  <pre><code>The crash stack is :
  Exception Type:  SIGSEGV
  Exception Codes: SEGV_ACCERR at 0xd9f2c061
  Crashed Thread:  0
  
  Thread 0 Crashed:
  0   libobjc.A.dylib                     0x3a74f5aa objc_msgSend + 10
  1   Foundation                          0x33157599 -[NSNotificationCenter postNotificationName:object:userInfo:] + 73
  2   UIKit                               0x347830cd -[UIApplication _handleApplicationSuspend:eventInfo:] + 733
  3   UIKit                               0x346f91e7 -[UIApplication handleEvent:withNewEvent:] + 2459
  4   UIKit                               0x346f86cd -[UIApplication sendEvent:] + 73
  5   UIKit                               0x346f811b _UIApplicationHandleEvent + 6155
  6   GraphicsServices                    0x363ee5a3 _PurpleEventCallback + 591
  </code></pre>