App crashed on [ +[NSObject(NSObject) _copyDescription] ], however could not get why.

Question

Jeff_Lu OP

Created Apr ’25

Replies 2

Boosts 0

Participants 3

Hi All

my app randomly crash on very rare case. when bring app into foreground

I checked the code:

{
    NSError *error = nil;
    
    if (![sender authenticateWithPassword:MyManager.sharedManager.service.authToken.accessToken error:&error]) {
...
...
...
    }
}

accessToken is NSString type, was that because accessToken is deallocated? Manager and service could not be nil at all.

Last Exception Backtrace:
0   CoreFoundation                	       0x18b04d2ec __exceptionPreprocess + 164
1   libobjc.A.dylib               	       0x1884d1a7c objc_exception_throw + 88
2   CoreFoundation                	       0x18b0b767c +[NSObject(NSObject) _copyDescription] + 0
3   CoreFoundation                	       0x18af64b84 ___forwarding___ + 1492
4   CoreFoundation                	       0x18af644f0 _CF_forwarding_prep_0 + 96
5   PTComms                       	       0x102adafac __45-[XMPPStream authenticateWithPassword:error:]_block_invoke + 1884
6   libdispatch.dylib             	       0x192ecb584 _dispatch_client_callout + 16
7   libdispatch.dylib             	       0x192ec1b4c _dispatch_sync_invoke_and_complete_recurse + 64
8   libdispatch.dylib             	       0x192ec15dc _dispatch_sync_f_slow + 176
9   PTComms                       	       0x102ada760 -[XMPPStream authenticateWithPassword:error:] + 516
10  PTComms                       	       0x102a7b6f0 -[CommsService xmppStreamDidConnect:] + 160
11  CoreFoundation                	       0x18af64434 __invoking___ + 148
12  CoreFoundation                	       0x18af65044 -[NSInvocation invoke] + 424
13  CoreFoundation                	       0x18afbb6b8 -[NSInvocation invokeWithTarget:] + 64
14  PTComms                       	       0x102b391c8 __42-[GCDMulticastDelegate forwardInvocation:]_block_invoke + 68
15  libdispatch.dylib             	       0x192eb1aac _dispatch_call_block_and_release + 32
16  libdispatch.dylib             	       0x192ecb584 _dispatch_client_callout + 16
17  libdispatch.dylib             	       0x192ee8574 _dispatch_main_queue_drain.cold.5 + 812
18  libdispatch.dylib             	       0x192ec0d30 _dispatch_main_queue_drain + 180
19  libdispatch.dylib             	       0x192ec0c6c _dispatch_main_queue_callback_4CF + 44
20  CoreFoundation                	       0x18afa62b4 __CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__ + 16
21  CoreFoundation                	       0x18afa40b0 __CFRunLoopRun + 1980
22  CoreFoundation                	       0x18afc8700 CFRunLoopRunSpecific + 572
23  GraphicsServices              	       0x1d7b09190 GSEventRunModal + 168
24  UIKitCore                     	       0x18dbe6240 -[UIApplication _run] + 816
25  UIKitCore                     	       0x18dbe4470 UIApplicationMain + 336
26  VoceraEdgeComms               	       0x102542318 0x10253c000 + 25368
27  dyld                          	       0x1b19cbad8 start + 5964

Thread 0 name:   Dispatch queue: xmpp
Thread 0 Crashed:
0   libsystem_kernel.dylib        	       0x1dbb3a1dc __pthread_kill + 8
1   libsystem_pthread.dylib       	       0x2154b8b40 pthread_kill + 268
2   libsystem_c.dylib             	       0x192f6d360 __abort + 132
3   libsystem_c.dylib             	       0x192f6d2dc abort + 136
4   libc++abi.dylib               	       0x2153e25a0 abort_message + 132
5   libc++abi.dylib               	       0x2153d0f10 demangling_terminate_handler() + 344
6   libobjc.A.dylib               	       0x1884d3bb8 _objc_terminate() + 156
7   PTCore                        	       0x1061f0d98 FIRCLSTerminateHandler() (.cold.3) + 56
8   PTCore                        	       0x1060ef7e8 FIRCLSTerminateHandler() + 276
9   libc++abi.dylib               	       0x2153e18b4 std::__terminate(void (*)()) + 16
10  libc++abi.dylib               	       0x2153e4e1c __cxxabiv1::failed_throw(__cxxabiv1::__cxa_exception*) + 88
11  libc++abi.dylib               	       0x2153e4dc4 __cxa_throw + 92
12  libobjc.A.dylib               	       0x1884d1be4 objc_exception_throw + 448
13  CoreFoundation                	       0x18b0b767c -[NSObject(NSObject) doesNotRecognizeSelector:] + 364
14  CoreFoundation                	       0x18af64b84 ___forwarding___ + 1492
15  CoreFoundation                	       0x18af644f0 _CF_forwarding_prep_0 + 96
16  PTComms                       	       0x102adafac __45-[XMPPStream authenticateWithPassword:error:]_block_invoke +

Thanks,

CrashReporter.txt

Answered by DTS Engineer in 835177022

Frames 8 through 7 of thread 0 shows that you have a third-party crash reporter installed. I don’t trust the resulting crash reports, for the reasons I outline in Implementing Your Own Crash Reporter. I recommend that you remove it and then try to get an Apple crash report.

However, assuming that the crash report is to be believed, it’s most likely that sender is a bogus object. Note frame 4, where the Objective-C method dispatcher is calling out to the forwarding infrastructure. This suggests that the target object doesn’t implement the method involved, and that usually suggests a memory management problem, where the actual sender object has been deallocated and then some other object has been allocated in its place.

I recommend that you heavily exercise your app with zombies enabled. That might make the problem reproducible, and hence much easier to debug. See Standard Memory Debugging Tools.

Share and Enjoy
—
Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"

Boost

Answer 1

darkpaw OP

Apr ’25

Not sure if this is the problem, but you're passing by reference that error variable into that call, but you've set it to nil, so if there's an error in that call it can't write that error to that variable because it's nil.

Try: NSError *error; instead.

Then, when inspecting the results of that call, you need to check if error is nil before trying to access its contents.

0

Answer 2

DTS Engineer OP

Apple

Apr ’25

Accepted Answer

Recommended

Frames 8 through 7 of thread 0 shows that you have a third-party crash reporter installed. I don’t trust the resulting crash reports, for the reasons I outline in Implementing Your Own Crash Reporter. I recommend that you remove it and then try to get an Apple crash report.

However, assuming that the crash report is to be believed, it’s most likely that sender is a bogus object. Note frame 4, where the Objective-C method dispatcher is calling out to the forwarding infrastructure. This suggests that the target object doesn’t implement the method involved, and that usually suggests a memory management problem, where the actual sender object has been deallocated and then some other object has been allocated in its place.

I recommend that you heavily exercise your app with zombies enabled. That might make the problem reproducible, and hence much easier to debug. See Standard Memory Debugging Tools.

Share and Enjoy
—
Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"

0