Question

I’m having this crash now and then, in a thread that is not started by me that I know, with CFXPreferencesPropertyListSourceSynchronizer and CFXPreferencesPropertyListSource mentioned.
I do have a separate thread that accesses the NSUserDefaults. (NSUserDefaults is supposed to be thread safe.) Anyone recognize what is going wrong here?

Exception Type:  EXC_BAD_ACCESS (SIGSEGV)
Exception Codes: KERN_INVALID_ADDRESS at 0x444e4128
Crashed Thread:  5

Thread 5 name:  Dispatch queue: CFPreferences Background Sync Queue
Thread 5 Crashed:
0   libobjc.A.dylib                 0x34ec4f78 objc_msgSend + 16
1   CoreFoundation                  0x3710de90 CFRetain + 76
2   CoreFoundation                  0x3718aa96 __CFDictionaryStandardRetainValue + 62
3   CoreFoundation                  0x37114fe0 CFBasicHashCreateCopy + 832
4   CoreFoundation                  0x37124f50 CFDictionaryCreateMutableCopy + 388
5   CoreFoundation                  0x3712d340 -[CFXPreferencesPropertyListSourceSynchronizer initWithPropertyListSource:forLockedSynchronize:] + 232
6   CoreFoundation                  0x371b4800 __79-[CFXPreferencesPropertyListSource synchronizeInBackgroundWithCompletionBlock:]_block_invoke_0 + 56
7   libdispatch.dylib               0x302e5c52 _dispatch_call_block_and_release + 6
8   libdispatch.dylib               0x302f0ca4 _dispatch_queue_drain + 268
9   libdispatch.dylib               0x302f0b12 _dispatch_queue_invoke$VARIANT$up + 30
10  libdispatch.dylib               0x302f1784 _dispatch_worker_thread2 + 208
11  libsystem_c.dylib               0x33a34df4 _pthread_wqthread + 288
12  libsystem_c.dylib               0x33a34cc8 start_wqthread + 0

Answer 1

It crashes on CFRetain so my best guess is that you have over-released some key or some value, or you used non-object as key or value.