iOS Crash Core Location CFBasicHashCreateCopy?

Question

I've got this issue being reported via Crashlytics, although I've been unable to replicate it locally, so I've got nothing to go on other than the stack trace below.. Not sure if the references to CoreLocation in the stack trace have anything to do with it, but I'm not sure what could possibly be the cause. My project is using ARC. Any clue?

Thread : Crashed: com.apple.CoreLocation.ConnectionClient.0x14eb3510.events
0  CoreFoundation                 0x307769a8 CFBasicHashCreateCopy + 712
1  libobjc.A.dylib                0x3afd1a19 object_setClass + 24
2  CoreFoundation                 0x30782d0f CFDictionaryCreateMutableCopy + 154
3  CoreLocation                   0x30d0a8f3 CLLocationCoordinate2DGetDistanceFrom + 47590
4  CoreLocation                   0x30d2d607 CLClientCreateIso6709Notation + 49626
5  CoreFoundation                 0x30786d45 __CFDictionaryApplyFunction_block_invoke + 16
6  CoreFoundation                 0x30772cd4 CFBasicHashApply + 128
7  CoreFoundation                 0x3077be27 CFDictionaryApplyFunction + 154
8  CoreLocation                   0x30d2cc25 CLClientCreateIso6709Notation + 47096
9  CoreLocation                   0x30d2b625 CLClientCreateIso6709Notation + 41464
10 libxpc.dylib                   0x3b5fc3a9 _xpc_connection_call_event_handler + 40
11 libxpc.dylib                   0x3b5fee67 do_mach_notify_port_destroyed + 122
12 libxpc.dylib                   0x3b5fedd1 _Xmach_notify_port_destroyed + 104
13 libxpc.dylib                   0x3b5fed47 notify_server + 62
14 libxpc.dylib                   0x3b5fa9cf _xpc_connection_mach_event + 1926
15 libdispatch.dylib              0x3b4bdf43 _dispatch_mach_msg_invoke + 118
16 libdispatch.dylib              0x3b4c0c71 _dispatch_queue_drain + 412
17 libdispatch.dylib              0x3b4bda6b _dispatch_mach_invoke + 78
18 libdispatch.dylib              0x3b4c0c71 _dispatch_queue_drain + 412
19 libdispatch.dylib              0x3b4bdc6f _dispatch_queue_invoke + 42
20 libdispatch.dylib              0x3b4c0c71 _dispatch_queue_drain + 412
21 libdispatch.dylib              0x3b4bdc6f _dispatch_queue_invoke + 42
22 libdispatch.dylib              0x3b4c15f1 _dispatch_root_queue_drain + 76
23 libdispatch.dylib              0x3b4c18dd _dispatch_worker_thread2 + 56
24 libsystem_pthread.dylib        0x3b5ecc17 _pthread_wqthread + 298

Here is another, likely related.

Crashed: com.apple.CoreLocation.ConnectionClient.0x17665330.events
EXC_BAD_ACCESS KERN_INVALID_ADDRESS at 0x11755e44

Thread : Crashed: com.apple.CoreLocation.ConnectionClient.0x17665330.events
0  libobjc.A.dylib                0x381db626 objc_msgSend + 5
1  CoreFoundation                 0x2d979d75 CFDictionaryCreateMutableCopy + 320
2  CoreLocation                   0x2df018f3 (null) + 47590
3  CoreLocation                   0x2df24607 (null) + 49626
4  CoreFoundation                 0x2d97dd05 __CFDictionaryApplyFunction_block_invoke + 16
5  CoreFoundation                 0x2d969c94 CFBasicHashApply + 128
6  CoreFoundation                 0x2d972de7 CFDictionaryApplyFunction + 154
7  CoreLocation                   0x2df23c25 (null) + 47096
8  CoreLocation                   0x2df22625 (null) + 41464
9  libxpc.dylib                   0x387fb3a9 _xpc_connection_call_event_handler + 40
10 libxpc.dylib                   0x387fde67 do_mach_notify_port_destroyed + 122
11 libxpc.dylib                   0x387fddd1 _Xmach_notify_port_destroyed + 104
12 libxpc.dylib                   0x387fdd47 notify_server + 62
13 libxpc.dylib                   0x387f99cf _xpc_connection_mach_event + 1926
14 libdispatch.dylib              0x386bcf43 _dispatch_mach_msg_invoke + 118
15 libdispatch.dylib              0x386bfc71 _dispatch_queue_drain + 412
16 libdispatch.dylib              0x386bca6b _dispatch_mach_invoke + 78
17 libdispatch.dylib              0x386bfc71 _dispatch_queue_drain + 412
18 libdispatch.dylib              0x386bcc6f _dispatch_queue_invoke + 42
19 libdispatch.dylib              0x386bfc71 _dispatch_queue_drain + 412
20 libdispatch.dylib              0x386bcc6f _dispatch_queue_invoke + 42
21 libdispatch.dylib              0x386c05f1 _dispatch_root_queue_drain + 76
22 libdispatch.dylib              0x386c08dd _dispatch_worker_thread2 + 56
23 libsystem_pthread.dylib        0x387ebc17 _pthread_wqthread + 298

Answer 1

You've had the system send a message to a bad memory location where an object should have been. So my suggestion is to enable zombie detection (Edit Scheme, then select the Diagnostics Tab, tick enable zombie objects) and re-do your test scenarios in particular anything that causes CoreLocation events.

Then when core location sends a message to a released object, you will know what the object was originally that got released (because it is artificially kept alive by this debug setting as a zombie object).