how to debug EXC_CRASH (SIGTRAP) - iphone

Question

i'm running my app are running fine until i resume from background or with out location services, the app will crash.
the crash log shows Exception Type: EXC_CRASH (SIGTRAP)
Anybody know how to debug it ?
Exception Type: EXC_CRASH (SIGTRAP)
Exception Codes: 0x00000000, 0x00000000
Crashed Thread: 0
Thread 0 name: Dispatch queue: com.apple.main-thread
Thread 0 Crashed:
0 libsystem_kernel.dylib 0x36398848 __kill + 8
1 FrogFinder 0x000b5034 0x69000 + 311348
2 CoreFoundation 0x3447e980 __handleUncaughtException + 68
3 libobjc.A.dylib 0x346ce2ca _objc_terminate + 122
4 libc++abi.dylib 0x338a33be _ZL19safe_handler_callerPFvvE + 70
5 libc++abi.dylib 0x338a344a std::terminate() + 14
6 libc++abi.dylib 0x338a481e __cxa_rethrow + 82
7 libobjc.A.dylib 0x346ce22e objc_exception_rethrow + 6
8 CoreFoundation 0x343d453e CFRunLoopRunSpecific + 398
9 CoreFoundation 0x343d439e CFRunLoopRunInMode + 98
10 GraphicsServices 0x30c58fc6 GSEventRunModal + 150
11 UIKit 0x3785573c UIApplicationMain + 1084
12 FrogFinder 0x0006a7e6 0x69000 + 6118
13 FrogFinder 0x0006a7a4 0x69000 + 6052
Thread 1 name: Dispatch queue: com.apple.libdispatch-manager
Thread 1:
0 libsystem_kernel.dylib 0x363893b4 kevent + 24
1 libdispatch.dylib 0x370b3e78 _dispatch_mgr_invoke + 708
2 libdispatch.dylib 0x370b3b96 _dispatch_mgr_thread + 30
Thread 2 name: WebThread
Thread 2:
0 libsystem_kernel.dylib 0x36389010 mach_msg_trap + 20
1 libsystem_kernel.dylib 0x36389206 mach_msg + 50
2 CoreFoundation 0x3445241c __CFRunLoopServiceMachPort + 120
3 CoreFoundation 0x34451154 __CFRunLoopRun + 876
4 CoreFoundation 0x343d44d6 CFRunLoopRunSpecific + 294
5 CoreFoundation 0x343d439e CFRunLoopRunInMode + 98
6 WebCore 0x368a8128 _ZL12RunWebThreadPv + 396
7 libsystem_c.dylib 0x33224c16 _pthread_start + 314
8 libsystem_c.dylib 0x33224ad0 thread_start + 0
Thread 3 name: com.apple.NSURLConnectionLoader
Thread 3:
0 libsystem_kernel.dylib 0x36389010 mach_msg_trap + 20
1 libsystem_kernel.dylib 0x36389206 mach_msg + 50
2 CoreFoundation 0x3445241c __CFRunLoopServiceMachPort + 120
3 CoreFoundation 0x34451154 __CFRunLoopRun + 876
4 CoreFoundation 0x343d44d6 CFRunLoopRunSpecific + 294
5 CoreFoundation 0x343d439e CFRunLoopRunInMode + 98
6 Foundation 0x35dd4bc2 +[NSURLConnection(Loader) _resourceLoadLoop:] + 302
7 Foundation 0x35dd4a8a -[NSThread main] + 66
8 Foundation 0x35e6859a __NSThread__main__ + 1042
9 libsystem_c.dylib 0x33224c16 _pthread_start + 314
10 libsystem_c.dylib 0x33224ad0 thread_start + 0
Thread 4:
0 libsystem_kernel.dylib 0x36389010 mach_msg_trap + 20
1 libsystem_kernel.dylib 0x36389206 mach_msg + 50
2 CoreFoundation 0x3445241c __CFRunLoopServiceMachPort + 120
3 CoreFoundation 0x34451154 __CFRunLoopRun + 876
4 CoreFoundation 0x343d44d6 CFRunLoopRunSpecific + 294
5 CoreFoundation 0x343d439e CFRunLoopRunInMode + 98
6 Foundation 0x35dc8b7e -[NSRunLoop(NSRunLoop) runMode:beforeDate:] + 250
7 Foundation 0x35de252c -[NSRunLoop(NSRunLoop) run] + 72
8 FrogFinder 0x000c8da6 0x69000 + 392614
9 Foundation 0x35dd4a8a -[NSThread main] + 66
10 Foundation 0x35e6859a __NSThread__main__ + 1042
11 libsystem_c.dylib 0x33224c16 _pthread_start + 314
12 libsystem_c.dylib 0x33224ad0 thread_start + 0
Thread 5 name: NetworkIO
Thread 5:
0 libsystem_kernel.dylib 0x36389010 mach_msg_trap + 20
1 libsystem_kernel.dylib 0x36389206 mach_msg + 50
2 CoreFoundation 0x3445241c __CFRunLoopServiceMachPort + 120
3 CoreFoundation 0x34451154 __CFRunLoopRun + 876
4 CoreFoundation 0x343d44d6 CFRunLoopRunSpecific + 294
5 CoreFoundation 0x343d439e CFRunLoopRunInMode + 98
6 MapKit 0x38030412 0x38022000 + 58386
7 Foundation 0x35dd4a8a -[NSThread main] + 66
8 Foundation 0x35e6859a __NSThread__main__ + 1042
9 libsystem_c.dylib 0x33224c16 _pthread_start + 314
10 libsystem_c.dylib 0x33224ad0 thread_start + 0

Answer 1

You can also turn on Exception breakpoints. In XCode 4 click your project and choose the breakpoints tab. At the bottom of that tab is | + | - | search bar. Choose the + item and "Add Exeception Breakpoint". You can leave it at All or choose Objective-C. This way you will break in the debugger and be able to see what caused the exeception.

Answer 2

With Xcode 4.2 and iOS 5 uncaught exceptions do not seem to show in the console anymore. I would recommend adding the following or modifying your existing uncaught exception handler to dump the exceptions callstack for you.
#ifdef DEBUG
void eHandler(NSException *);
void eHandler(NSException *exception) {
NSLog(#"%#", exception);
NSLog(#"%#", [exception callStackSymbols]);
}
#endif
int main(int argc, char *argv[]) {
#ifdef DEBUG
NSSetUncaughtExceptionHandler(&eHandler);
#endif
...rest of your main function here...
}

Answer 3

The easiest way for this kind of crashes which are occuring during development is to add exception break points.
You can add exception breakpoint like below
Select the break points option in left menu in XCode
Add the exception break point
Add breakpoint for all the exceptions
Run the app. In most of the cases when exception occurs XCode will stop the execution and show you the line which caused the exception.