Unable to understand where MyApp crashes

Question

My application crashes in some scenarios. Could not find the cause and location of the failure.

Below is the crash log (iPad / iOS 8.0.2).

Hardware Model: iPad2,5 OS Version: iOS 8.0.2 (12A405) Report Version: 105 Exception Type: EXC_CRASH (SIGABRT) Exception Codes: 0x0000000000000000, 0x0000000000000000 Triggered by Thread: 0 Thread 0 Crashed: 0 libsystem_kernel.dylib 0x306b3dfc __pthread_kill + 8 1 libsystem_pthread.dylib 0x30733d0e pthread_kill + 58 2 libsystem_c.dylib 0x30653934 abort + 72 3 libc++abi.dylib 0x2f864bb8 abort_message + 84 4 libc++abi.dylib 0x2f87e66a default_terminate_handler() + 262 5 libobjc.A.dylib 0x30052f0e _objc_terminate() + 190 6 libc++abi.dylib 0x2f87bdec std::__terminate(void (*)()) + 76 7 libc++abi.dylib 0x2f87b5ac __cxa_throw + 108 8 libobjc.A.dylib 0x30052d46 objc_exception_throw + 246 9 CoreFoundation 0x225dfe58 +[NSException raise:format:arguments:] + 100 10 Foundation 0x232af2c4 -[NSAssertionHandler handleFailureInMethod:object:file:lineNumber:description:] + 88 11 BaseBoard 0x270a08d8 __25-[BSAction sendResponse:]_block_invoke + 140 12 libdispatch.dylib 0x305bc99c _dispatch_barrier_sync_f_invoke + 44 13 BaseBoard 0x270a0842 -[BSAction sendResponse:] + 98 14 UIKit 0x25fd54d0 -[UIFetchContentInBackgroundAction sendResponse:] + 212 15 libdispatch.dylib 0x305b3610 _dispatch_call_block_and_release + 8 16 libdispatch.dylib 0x305b35fc _dispatch_client_callout + 20 17 libdispatch.dylib 0x305be2b2 _dispatch_main_queue_callback_4CF$VARIANT$mp + 714 18 CoreFoundation 0x225a5e5c __CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__ + 4 19 CoreFoundation 0x225a457c __CFRunLoopRun + 1508 20 CoreFoundation 0x224f1dac CFRunLoopRunSpecific + 472 21 CoreFoundation 0x224f1bbe CFRunLoopRunInMode + 102 22 GraphicsServices 0x2985404c GSEventRunModal + 132 23 UIKit 0x25abda2c UIApplicationMain + 1436 24 MyApp 0x000fb9f2 main (main.m:15) 25 libdyld.dylib 0x305eeaac start + 0 

Thanks in advance.

Answer 1

An exception message that matches the stack trace:

"this request has been castrated - you cannot call -sendResponse: twice after it has been encoded"

While you cannot tell from the stack exactly, you are most likely calling the Handler completion passed to your application delegate delta - application: execute the FetchWithCompletionHandler: method twice.

Answer 2

Background fetch is launched by the OS based on the value set in the setMinimumBackgroundFetchInterval: method. What you see is similar to what the OS does with your application if the background fetch takes too much time.

You are assigned a time (30 seconds) to complete your work. If you are not done, the OS kills your application with the above exception. Read more about how to extend the required time here .

Basically, you need to ask for more time to complete the background task as follows:

 - (void)applicationDidEnterBackground:(UIApplication *)application { bgTask = [application beginBackgroundTaskWithName:@"MyTask" expirationHandler:^{ // Clean up any unfinished task business by marking where you // stopped or ending the task outright. [application endBackgroundTask:bgTask]; bgTask = UIBackgroundTaskInvalid; }]; // Start the long-running task and return immediately. dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{ // Do the work associated with the task, preferably in chunks. [application endBackgroundTask:bgTask]; bgTask = UIBackgroundTaskInvalid; }); }