I am getting some weird coredata error in the production app and I was able to get hold of the Crash Report.
Its Crashing with the following message at times
*** error for object 0x17e400000: Freeing unallocated pointer
*** error for object 0x17fd03730: pointer being reallocated was not allocated
And here is the stack trace
Crashed: SQLQueue 0x13ff15250 for datastore.sqlite
SIGABRT ABORT 0x0000000183986014
0 libsystem_kernel.dylib __pthread_kill + 8
1 libsystem_pthread.dylib pthread_kill + 112
2 libsystem_c.dylib abort + 140
3 libsystem_malloc.dylib _nano_vet_and_size_of_live + 330
4 libsystem_malloc.dylib nano_free + 220
5 libsqlite3.dylib sqlite3_finalize + 244
6 CoreData -[NSSQLiteConnection _finalizeStatement] + 100
7 CoreData -[NSSQLiteConnection releaseSQLStatement] + 52
8 CoreData newFetchedRowsForFetchPlan_MT + 2420
9 CoreData _executeFetchRequest + 72
10 CoreData -[NSSQLFetchRequestContext executeRequestUsingConnection:] + 60
11 CoreData __52-[NSSQLDefaultConnectionManager handleStoreRequest:]_block_invoke + 260
12 libdispatch.dylib _dispatch_client_callout + 16
13 libdispatch.dylib _dispatch_barrier_sync_f_invoke + 84
14 CoreData -[NSSQLDefaultConnectionManager handleStoreRequest:] + 208
15 CoreData -[NSSQLCoreDispatchManager routeStoreRequest:] + 288
16 CoreData -[NSSQLCore dispatchRequest:withRetries:] + 200
17 CoreData -[NSSQLCore processFetchRequest:inContext:] + 108
18 CoreData -[NSSQLCore executeRequest:withContext:error:] + 504
19 CoreData __65-[NSPersistentStoreCoordinator executeRequest:withContext:error:]_block_invoke + 4512
20 CoreData -[NSPersistentStoreCoordinator _routeHeavyweightBlock:] + 276
21 CoreData -[NSPersistentStoreCoordinator executeRequest:withContext:error:] + 408
22 CoreData -[NSManagedObjectContext executeFetchRequest:error:] + 572
23 CoreData -[NSManagedObjectContext(_NestedContextSupport) _parentObjectsForFetchRequest:inContext:error:] + 456
24 CoreData __82-[NSManagedObjectContext(_NestedContextSupport) executeRequest:withContext:error:]_block_invoke + 584
25 CoreData internalBlockToNSManagedObjectContextPerform + 92
26 libdispatch.dylib _dispatch_client_callout + 16
27 libdispatch.dylib _dispatch_barrier_sync_f_invoke + 84
28 CoreData _perform + 232
29 CoreData -[NSManagedObjectContext(_NestedContextSupport) executeRequest:withContext:error:] + 188
30 CoreData -[NSManagedObjectContext executeFetchRequest:error:] + 572
31 *MY_APP* NSManagedObject+MagicalRecord.m line 50__67+[NSManagedObject(MagicalRecord) MR_executeFetchRequest:inContext:]_block_invoke
It did happen on the main thread and I am puzzled on how to debug this. Looks like a memory issue though. Also while using instruments its showing some leaks in the app when it comes across NSPrivateQueueConcurrencyType .
Looking for some insights on nailing it down.
App is using MagicalRecord Extensively and here is the code block in the App Which leads to above crash. Its just a normal fetch from Main Thread. Most interestingly it crash randomly, ie it doesn't always crash but at times it crashes while doing a Fetch.
NSPredicate *filterPredicate = [NSPredicate predicateWithFormat:@"code == %@ and pid == %@", aCode,pid]; Permission *aPermission = [Permission MR_findFirstWithPredicate:filterPredicate];
Accessing (Write or Read) a Managed Object on any thread other than the Managed Object Context Queue causes undefined behaviour & leads to random weird crashes.
It looks like your Managed Object Context was created with NSPrivateQueueConcurrencyType & your performing fetch on the Main Queue. This is the source of the weird crash.
You can either initialize MOC with NSMainQueueConcurrencyType or nest all your fetchRequests inside [MOC performBlock:{...}]
Core-date managedObjectContext and managedObjects are not thread-safe - neither for writing or for reading. If you ever violate this rule core-date can crash at any time - not necessarily where/when the violation occurred. So even if you are on the main thread and accessing a context designed for the main thread it can still crash if you did something wrong somewhere else in your app.
来源：https://stackoverflow.com/questions/42248955/coredata-crash-while-fetching