title: WebThread JavaScriptCore crash - what this crash report means
body: <p>I need help in understanding this crash log from a test user. 
  I did not write any JavaScriptCore related code in my app. </p>
  
  <p>I still don't know how to reproduce this crash. Any insights about this problem would be helpful to me in finding this problem.</p>
  
  <p>Thanks,</p>
  
  <p>P.S
  My app is using Admob mediation. I don't know if it has some relation about this.</p>
  
  <pre><code>Incident Identifier: 7B6EFFFF-4D55-48AE-8FE8-A55590405F0A
  CrashReporter Key:   ef1ad783966254a93308221f30f17134c95879f7
  Hardware Model:      iPad5,3
  Process:             ???? [2325]
  Path:                /private/var/mobile/Containers/Bundle/Application/16AE72E1-A8C8-45D9-955F-A6F96FCCE800/????.app/????
  Identifier:          ????
  Version:             3.75.14 (3.75)
  Code Type:           ARM-64 (Native)
  Parent Process:      launchd [1]
  
  Date/Time:           2015-05-16 10:36:50.459 -0700
  Launch Time:         2015-05-16 10:00:10.481 -0700
  OS Version:          iOS 8.3 (12F69)
  Report Version:      105
  
  Exception Type:  EXC_BAD_ACCESS (SIGSEGV)
  Exception Subtype: KERN_INVALID_ADDRESS at 0x00000000bbadbeef
  Triggered by Thread:  4
  
  Thread 0 name:  Dispatch queue: com.apple.main-thread
  Thread 0:
  0   libsystem_kernel.dylib          0x0000000197080e0c mach_msg_trap + 8
  1   libsystem_kernel.dylib          0x0000000197080c84 mach_msg + 68
  2   CoreFoundation                  0x00000001852fb720 __CFRunLoopServiceMachPort + 196
  3   CoreFoundation                  0x00000001852f9674 __CFRunLoopRun + 936
  4   CoreFoundation                  0x00000001852252d0 CFRunLoopRunSpecific + 392
  5   GraphicsServices                0x000000018e9036f8 GSEventRunModal + 164
  6   UIKit                           0x0000000189deafa8 UIApplicationMain + 1484
  7   ClockXtrm                       0x000000010004f668 main (main.m:17)
  8   libdyld.dylib                   0x0000000196f82a04 start + 0
  
  Thread 1 name:  Dispatch queue: com.apple.libdispatch-manager
  Thread 1:
  0   libsystem_kernel.dylib          0x0000000197080c24 kevent64 + 8
  1   libdispatch.dylib               0x0000000196f65e6c _dispatch_mgr_invoke + 272
  2   libdispatch.dylib               0x0000000196f57998 _dispatch_mgr_thread + 48
  
  Thread 2 name:  com.apple.coremedia.player.async
  Thread 2:
  0   libsystem_kernel.dylib          0x0000000197080e48 semaphore_wait_trap + 8
  1   libdispatch.dylib               0x0000000196f63f3c _dispatch_semaphore_wait_slow + 252
  2   MediaToolbox                    0x000000018780cb48 fpa_AsyncMovieControlThread + 1952
  3   CoreMedia                       0x0000000185b5f9ac figThreadMain + 244
  4   libsystem_pthread.dylib         0x0000000197137dc4 _pthread_body + 160
  5   libsystem_pthread.dylib         0x0000000197137d20 _pthread_start + 156
  6   libsystem_pthread.dylib         0x0000000197134ef4 thread_start + 0
  
  Thread 3 name:  com.apple.NSURLConnectionLoader
  Thread 3:
  0   libsystem_kernel.dylib          0x0000000197080e0c mach_msg_trap + 8
  1   libsystem_kernel.dylib          0x0000000197080c84 mach_msg + 68
  2   CoreFoundation                  0x00000001852fb720 __CFRunLoopServiceMachPort + 196
  3   CoreFoundation                  0x00000001852f9674 __CFRunLoopRun + 936
  4   CoreFoundation                  0x00000001852252d0 CFRunLoopRunSpecific + 392
  5   CFNetwork                       0x0000000184d06890 +[NSURLConnection(Loader) _resourceLoadLoop:] + 436
  6   Foundation                      0x0000000186245db4 __NSThread__main__ + 1068
  7   libsystem_pthread.dylib         0x0000000197137dc4 _pthread_body + 160
  8   libsystem_pthread.dylib         0x0000000197137d20 _pthread_start + 156
  9   libsystem_pthread.dylib         0x0000000197134ef4 thread_start + 0
  
  Thread 4 name:  WebThread
  Thread 4 Crashed:
  0   JavaScriptCore                  0x0000000186c3d58c WTFCrash + 72
  1   JavaScriptCore                  0x0000000186c3d580 WTFCrash + 60
  2   JavaScriptCore                  0x0000000186b3df1c JSC::JSLock::DropAllLocks::DropAllLocks(JSC::VM*) + 268
  3   WebCore                         0x000000019391fd54 SendDelegateMessage(NSInvocation*) + 128
  4   CoreFoundation                  0x0000000185347f68 ___forwarding___ + 436
  5   CoreFoundation                  0x000000018524acc8 _CF_forwarding_prep_0 + 88
  6   WebCore                         0x000000019395fda0 WebCore::DOMWindow::removeAllEventListeners() + 176
  7   WebCore                         0x0000000193943694 WebCore::Document::removeAllEventListeners() + 28
  8   WebCore                         0x00000001939424b8 WebCore::Document::~Document() + 216
  9   WebCore                         0x0000000193d9a12c WebCore::HTMLDocument::~HTMLDocument() + 8
  10  WebCore                         0x0000000193942114 WebCore::Node::~Node() + 152
  11  WebCore                         0x0000000193941f0c WebCore::HTMLHtmlElement::~HTMLHtmlElement() + 8
  12  WebCore                         0x00000001939b7874 WebCore::JSNodeOwner::finalize(JSC::Handle&lt;JSC::Unknown&gt;, void*) + 420
  13  JavaScriptCore                  0x0000000186895498 JSC::WeakBlock::sweep() + 108
  14  JavaScriptCore                  0x000000018681c978 JSC::WeakSet::sweep() + 28
  15  JavaScriptCore                  0x000000018681c8fc JSC::MarkedBlock::sweep(JSC::MarkedBlock::SweepMode) + 24
  16  JavaScriptCore                  0x000000018681b58c JSC::MarkedAllocator::allocateSlowCase(unsigned long) + 296
  17  WebCore                         0x0000000194010c1c WebCore::JSDOMWrapper* WebCore::createWrapper&lt;WebCore::JSHTMLCanvasElement, WebCore::HTMLCanvasElement&gt;(WebCore::JSDOMGlobalObject*, WebCore::HTMLCanvasElement*) + 588
  18  WebCore                         0x0000000194007a3c WebCore::createJSHTMLWrapper(WebCore::JSDOMGlobalObject*, WTF::PassRefPtr&lt;WebCore::HTMLElement&gt;) + 312
  19  WebCore                         0x0000000193887348 WebCore::toJSNewlyCreated(JSC::ExecState*, WebCore::JSDOMGlobalObject*, WebCore::Element*) + 56
  20  WebCore                         0x00000001938871a4 WebCore::jsDocumentPrototypeFunctionCreateElement(JSC::ExecState*) + 376
  21  JavaScriptCore                  0x0000000186b96fac llint_entry + 26156
  22  JavaScriptCore                  0x0000000186b96974 llint_entry + 24564
  23  JavaScriptCore                  0x0000000186b96974 llint_entry + 24564
  24  JavaScriptCore                  0x0000000186b96974 llint_entry + 24564
  25  JavaScriptCore                  0x0000000186b96974 llint_entry + 24564
  26  JavaScriptCore                  0x0000000186b96974 llint_entry + 24564
  27  JavaScriptCore                  0x0000000186b96974 llint_entry + 24564
  28  JavaScriptCore                  0x0000000186b96974 llint_entry + 24564
  29  JavaScriptCore                  0x0000000186b96974 llint_entry + 24564
  30  JavaScriptCore                  0x0000000186b96974 llint_entry + 24564
  31  JavaScriptCore                  0x0000000186b969d8 llint_entry + 24664
  32  JavaScriptCore                  0x0000000186b96974 llint_entry + 24564
  33  JavaScriptCore                  0x0000000186b96974 llint_entry + 24564
  34  JavaScriptCore                  0x0000000186b96974 llint_entry + 24564
  35  JavaScriptCore                  0x0000000186b96974 llint_entry + 24564
  36  JavaScriptCore                  0x0000000186b96974 llint_entry + 24564
  37  JavaScriptCore                  0x0000000186b90760 callToJavaScript + 304
  38  JavaScriptCore                  0x0000000186afeac4 JSC::JITCode::execute(JSC::VM*, JSC::ProtoCallFrame*) + 44
  39  JavaScriptCore                  0x00000001868695e0 JSC::Interpreter::executeCall(JSC::ExecState*, JSC::JSObject*, JSC::CallType, JSC::CallData const&amp;, JSC::JSValue, JSC::ArgList const&amp;) + 416
  40  JavaScriptCore                  0x0000000186940924 JSC::boundFunctionCall(JSC::ExecState*) + 532
  41  JavaScriptCore                  0x0000000186b908e8 callToNativeFunction + 312
  42  JavaScriptCore                  0x0000000186869624 JSC::Interpreter::executeCall(JSC::ExecState*, JSC::JSObject*, JSC::CallType, JSC::CallData const&amp;, JSC::JSValue, JSC::ArgList const&amp;) + 484
  43  JavaScriptCore                  0x0000000186995738 JSC::call(JSC::ExecState*, JSC::JSValue, JSC::CallType, JSC::CallData const&amp;, JSC::JSValue, JSC::ArgList const&amp;, JSC::JSValue*) + 88
  44  WebCore                         0x0000000193a932a4 WebCore::JSCallbackData::invokeCallback(JSC::JSValue, JSC::MarkedArgumentBuffer&amp;, bool*) + 580
  45  WebCore                         0x00000001940dd988 WebCore::JSRequestAnimationFrameCallback::handleEvent(double) + 176
  46  WebCore                         0x0000000194423de4 WebCore::ScriptedAnimationController::serviceScriptedAnimations(double) + 424
  47  WebCore                         0x0000000193c2462c WebCore::DisplayRefreshMonitor::displayDidRefresh() + 452
  48  QuartzCore                      0x000000018971a298 CA::Display::DisplayLinkItem::dispatch() + 28
  49  QuartzCore                      0x000000018971a130 CA::Display::DisplayLink::dispatch_items(unsigned long long, unsigned long long, unsigned long long) + 320
  50  IOKit                           0x00000001864f546c IODispatchCalloutFromCFMessage + 372
  51  CoreFoundation                  0x00000001852e6dc0 __CFMachPortPerform + 176
  52  CoreFoundation                  0x00000001852fba50 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ + 52
  53  CoreFoundation                  0x00000001852fb9b0 __CFRunLoopDoSource1 + 432
  54  CoreFoundation                  0x00000001852f9930 __CFRunLoopRun + 1636
  55  CoreFoundation                  0x00000001852252d0 CFRunLoopRunSpecific + 392
  56  WebCore                         0x0000000193904890 RunWebThread(void*) + 464
  57  libsystem_pthread.dylib         0x0000000197137dc4 _pthread_body + 160
  58  libsystem_pthread.dylib         0x0000000197137d20 _pthread_start + 156
  59  libsystem_pthread.dylib         0x0000000197134ef4 thread_start + 0
  
  Thread 5 name:  com.apple.CFSocket.private
  Thread 5:
  0   libsystem_kernel.dylib          0x000000019709b498 __select + 8
  1   CoreFoundation                  0x0000000185301124 __CFSocketManager + 668
  2   libsystem_pthread.dylib         0x0000000197137dc4 _pthread_body + 160
  3   libsystem_pthread.dylib         0x0000000197137d20 _pthread_start + 156
  4   libsystem_pthread.dylib         0x0000000197134ef4 thread_start + 0
  
  Thread 6 name:  JavaScriptCore::BlockFree
  Thread 6:
  0   libsystem_kernel.dylib          0x000000019709b078 __psynch_cvwait + 8
  1   libsystem_pthread.dylib         0x0000000197136f28 _pthread_cond_wait + 620
  2   libc++.1.dylib                  0x0000000196080d5c std::__1::condition_variable::__do_timed_wait(std::__1::unique_lock&lt;std::__1::mutex&gt;&amp;, std::__1::chrono::time_point&lt;std::__1::chrono::system_clock, std::__1::chrono::duration&lt;long long, std::__1::ratio&lt;1l, 1000000000l&gt; &gt; &gt;) + 136
  3   JavaScriptCore                  0x0000000186982574 JSC::BlockAllocator::waitForDuration(std::__1::chrono::duration&lt;long long, std::__1::ratio&lt;1l, 1000l&gt; &gt;) + 176
  4   JavaScriptCore                  0x0000000186819588 JSC::BlockAllocator::blockFreeingThreadMain() + 76
  5   JavaScriptCore                  0x0000000186814b9c WTF::wtfThreadEntryPoint(void*) + 20
  6   libsystem_pthread.dylib         0x0000000197137dc4 _pthread_body + 160
  7   libsystem_pthread.dylib         0x0000000197137d20 _pthread_start + 156
  8   libsystem_pthread.dylib         0x0000000197134ef4 thread_start + 0
  
  Thread 7 name:  JavaScriptCore::Marking
  Thread 7:
  0   libsystem_kernel.dylib          0x000000019709b078 __psynch_cvwait + 8
  1   libsystem_pthread.dylib         0x0000000197136f28 _pthread_cond_wait + 620
  2   libc++.1.dylib                  0x0000000196080cac std::__1::condition_variable::wait(std::__1::unique_lock&lt;std::__1::mutex&gt;&amp;) + 52
  3   JavaScriptCore                  0x0000000186ac2edc JSC::GCThread::waitForNextPhase() + 152
  4   JavaScriptCore                  0x0000000186ac2f80 JSC::GCThread::gcThreadMain() + 88
  5   JavaScriptCore                  0x0000000186814b9c WTF::wtfThreadEntryPoint(void*) + 20
  6   libsystem_pthread.dylib         0x0000000197137dc4 _pthread_body + 160
  7   libsystem_pthread.dylib         0x0000000197137d20 _pthread_start + 156
  8   libsystem_pthread.dylib         0x0000000197134ef4 thread_start + 0
  
  Thread 8 name:  JavaScriptCore::Marking
  Thread 8:
  0   libsystem_kernel.dylib          0x000000019709b078 __psynch_cvwait + 8
  1   libsystem_pthread.dylib         0x0000000197136f28 _pthread_cond_wait + 620
  2   libc++.1.dylib                  0x0000000196080cac std::__1::condition_variable::wait(std::__1::unique_lock&lt;std::__1::mutex&gt;&amp;) + 52
  3   JavaScriptCore                  0x0000000186ac2edc JSC::GCThread::waitForNextPhase() + 152
  4   JavaScriptCore                  0x0000000186ac2f80 JSC::GCThread::gcThreadMain() + 88
  5   JavaScriptCore                  0x0000000186814b9c WTF::wtfThreadEntryPoint(void*) + 20
  6   libsystem_pthread.dylib         0x0000000197137dc4 _pthread_body + 160
  7   libsystem_pthread.dylib         0x0000000197137d20 _pthread_start + 156
  8   libsystem_pthread.dylib         0x0000000197134ef4 thread_start + 0
  
  Thread 9 name:  WebCore: CFNetwork Loader
  Thread 9:
  0   libsystem_kernel.dylib          0x0000000197080e0c mach_msg_trap + 8
  1   libsystem_kernel.dylib          0x0000000197080c84 mach_msg + 68
  2   CoreFoundation                  0x00000001852fb720 __CFRunLoopServiceMachPort + 196
  3   CoreFoundation                  0x00000001852f9674 __CFRunLoopRun + 936
  4   CoreFoundation                  0x00000001852252d0 CFRunLoopRunSpecific + 392
  5   WebCore                         0x00000001939389ac WebCore::runLoaderThread(void*) + 284
  6   JavaScriptCore                  0x0000000186814b9c WTF::wtfThreadEntryPoint(void*) + 20
  7   libsystem_pthread.dylib         0x0000000197137dc4 _pthread_body + 160
  8   libsystem_pthread.dylib         0x0000000197137d20 _pthread_start + 156
  9   libsystem_pthread.dylib         0x0000000197134ef4 thread_start + 0
  
  Thread 10 name:  WebCore: LocalStorage
  Thread 10:
  0   libsystem_kernel.dylib          0x000000019709b078 __psynch_cvwait + 8
  1   libsystem_pthread.dylib         0x0000000197136f28 _pthread_cond_wait + 620
  2   JavaScriptCore                  0x00000001868197bc WTF::ThreadCondition::timedWait(WTF::Mutex&amp;, double) + 76
  3   WebCore                         0x000000019448e32c std::__1::unique_ptr&lt;WTF::Function&lt;void ()&gt;, std::__1::default_delete&lt;WTF::Function&lt;void ()&gt; &gt; &gt; WTF::MessageQueue&lt;WTF::Function&lt;void ()&gt; &gt;::waitForMessageFilteredWithTimeout&lt;WTF::MessageQueue&lt;WTF::Function&lt;void ()&gt; &gt;::waitForMessage()::'lambda'(WTF::Function&lt;void ()&gt; const&amp;)&gt;(WTF::MessageQueueWaitResult&amp;, WTF::MessageQueue&lt;WTF::Function&lt;void ()&gt; &gt;::waitForMessage()::'lambda'(WTF::Function&lt;void ()&gt; const&amp;)&amp;&amp;, double) + 96
  4   WebCore                         0x0000000193a00ff8 WebCore::StorageThread::threadEntryPoint() + 220
  5   JavaScriptCore                  0x0000000186814b9c WTF::wtfThreadEntryPoint(void*) + 20
  6   libsystem_pthread.dylib         0x0000000197137dc4 _pthread_body + 160
  7   libsystem_pthread.dylib         0x0000000197137d20 _pthread_start + 156
  8   libsystem_pthread.dylib         0x0000000197134ef4 thread_start + 0
  
  Thread 11 name:  AVAudioSession Notify Thread
  Thread 11:
  0   libsystem_kernel.dylib          0x0000000197080e0c mach_msg_trap + 8
  1   libsystem_kernel.dylib          0x0000000197080c84 mach_msg + 68
  2   CoreFoundation                  0x00000001852fb720 __CFRunLoopServiceMachPort + 196
  3   CoreFoundation                  0x00000001852f9674 __CFRunLoopRun + 936
  4   CoreFoundation                  0x00000001852252d0 CFRunLoopRunSpecific + 392
  5   libAVFAudio.dylib               0x0000000183ca102c GenericRunLoopThread::Entry(void*) + 160
  6   libAVFAudio.dylib               0x0000000183c93a0c CAPThread::Entry(CAPThread*) + 116
  7   libsystem_pthread.dylib         0x0000000197137dc4 _pthread_body + 160
  8   libsystem_pthread.dylib         0x0000000197137d20 _pthread_start + 156
  9   libsystem_pthread.dylib         0x0000000197134ef4 thread_start + 0
  
  Thread 12:
  0   libsystem_kernel.dylib          0x000000019709bc78 __workq_kernreturn + 8
  1   libsystem_pthread.dylib         0x00000001971352d8 _pthread_wqthread + 988
  2   libsystem_pthread.dylib         0x0000000197134eec start_wqthread + 0
  
  Thread 13:
  0   libsystem_kernel.dylib          0x000000019709bc78 __workq_kernreturn + 8
  1   libsystem_pthread.dylib         0x00000001971352d8 _pthread_wqthread + 988
  2   libsystem_pthread.dylib         0x0000000197134eec start_wqthread + 0
  
  Thread 14:
  0   libsystem_kernel.dylib          0x000000019709bc78 __workq_kernreturn + 8
  1   libsystem_pthread.dylib         0x00000001971352d8 _pthread_wqthread + 988
  2   libsystem_pthread.dylib         0x0000000197134eec start_wqthread + 0
  
  Thread 15:
  0   libsystem_kernel.dylib          0x000000019709bc78 __workq_kernreturn + 8
  1   libsystem_pthread.dylib         0x00000001971352d8 _pthread_wqthread + 988
  2   libsystem_pthread.dylib         0x0000000197134eec start_wqthread + 0
  
  Thread 16:
  0   libsystem_kernel.dylib          0x000000019709bc78 __workq_kernreturn + 8
  1   libsystem_pthread.dylib         0x00000001971352d8 _pthread_wqthread + 988
  2   libsystem_pthread.dylib         0x0000000197134eec start_wqthread + 0
  
  Thread 17:
  0   libsystem_kernel.dylib          0x000000019709bc78 __workq_kernreturn + 8
  1   libsystem_pthread.dylib         0x00000001971352d8 _pthread_wqthread + 988
  2   libsystem_pthread.dylib         0x0000000197134eec start_wqthread + 0
  
  Thread 18:
  0   libsystem_kernel.dylib          0x000000019709bc78 __workq_kernreturn + 8
  1   libsystem_pthread.dylib         0x00000001971352d8 _pthread_wqthread + 988
  2   libsystem_pthread.dylib         0x0000000197134eec start_wqthread + 0
  
  Thread 4 crashed with ARM Thread State (64-bit):
      x0: 0x0000000000000000   x1: 0x00001f0000001f00   x2: 0x000000019aeb1ee0   x3: 0x0000000103b2c82c
      x4: 0x0000000103b2c828   x5: 0x0000000103b2c900   x6: 0x000000000000000a   x7: 0x0000000000000fa0
      x8: 0x00000000bbadbeef   x9: 0x0000000000000000  x10: 0x0000000000001f00  x11: 0x0000000000001f00
     x12: 0x0000000186b96978  x13: 0x0000000000000000  x14: 0x0000000000000003  x15: 0x0000000000000000
     x16: 0x00000001970c80fc  x17: 0x0000000000000000  x18: 0x0000000000000000  x19: 0x0000000103b2c9a8
     x20: 0x0000000170a786c0  x21: 0x0000000170a786c0  x22: 0x000000018a59aedd  x23: 0x000000019a8ebb20
     x24: 0x000000019a8eba10  x25: 0x000000018a58a2d0  x26: 0x0000000103b2cfa0  x27: 0x000000000000a740
     x28: 0x0000000000000002  fp: 0x0000000103b2cac0   lr: 0x0000000186c3d584
      sp: 0x0000000103b2c9a0   pc: 0x0000000186c3d58c cpsr: 0x60000000
  </code></pre>