I have a garbage collected Cocoa application built on 10.5 frameworks. In an NSOperation In a loop I am quickly creating hundreds of NSManagedObjects. Frequently the creation of those NSManagedObejcts will crash with a exc_bad_access error.

for (offsetCount; offsetCount < [parsedData count]; offsetCount++) {
    NSManagedObject *child = [NSEntityDescription insertNewObjectForEntityForName:@"Thread" inManagedObjectContext:[self moc]];
    Thumbnail *thumb = [Thumbnail insertInManagedObjectContext:[self moc]];
    Image *image = [Image insertInManagedObjectContext:[self moc]];
    ...
}

Thumbnail and Image are both subclasses of NSManagedObject generated with mogenerator. insertInManagedObjectContext: looks like

NSParameterAssert(moc_);
return [NSEntityDescription insertNewObjectForEntityForName:@"Thumbnail" inManagedObjectContext:moc_];

NSParameterAssert(moc_);
return [NSEntityDescription insertNewObjectForEntityForName:@"Image" inManagedObjectContext:moc_];

The NSManagedObjectContext returned by [self moc] is created for the NSOperation with

NSPersistentStoreCoordinator *coord = [(MyApp_AppDelegate *)[[NSApplication sharedApplication] delegate] persistentStoreCoordinator];
self.moc = [[NSManagedObjectContext alloc] init];
[self.moc setPersistentStoreCoordinator:coord];
[[NSNotificationCenter defaultCenter] addObserver:self
           selector:@selector(contextDidSave:) 
               name:NSManagedObjectContextDidSaveNotification 
             object:self.moc];
[self.moc setMergePolicy:NSMergeByPropertyObjectTrumpMergePolicy];
[self.moc setUndoManager:nil];
[self.moc setRetainsRegisteredObjects:YES];

moc is defined as (nonatomic, retain) and synthesized. As far as I can tell it, the persistent store and my appDelegate have no reason to be and are not being garbage collected.

The stack trace looks like

Thread 2 Crashed:  Dispatch queue: com.apple.root.default-priority
0   libauto.dylib                   0x00007fff82d63600 auto_zone_root_write_barrier + 688
1   libobjc.A.dylib                 0x00007fff826f963b objc_assign_strongCast_gc + 59
2   com.apple.CoreFoundation        0x00007fff88677068 __CFBasicHashAddValue + 504
3   com.apple.CoreFoundation        0x00007fff88676d2f CFBasicHashAddValue + 191
4   com.apple.CoreData              0x00007fff82bdee5e -[NSManagedObjectContext(_NSInternalAdditions) _insertObjectWithGlobalID:globalID:] + 190
5   com.apple.CoreData              0x00007fff82bded24 -[NSManagedObjectContext insertObject:] + 148
6   com.apple.CoreData              0x00007fff82bbd75c -[NSManagedObject initWithEntity:insertIntoManagedObjectContext:] + 716
7   com.apple.CoreData              0x00007fff82bdf075 +[NSEntityDescription insertNewObjectForEntityForName:inManagedObjectContext:] + 101
8   com.yourcompany.MyApp           0x000000010002c7a7 +[_Thumbnail insertInManagedObjectContext:] + 256 (_Thumbnail.m:14)
9   com.yourcompany.MyApp           0x000000010002672d -[ThreadParse main] + 10345 (B4ChanThreadParse.m:174)
10  com.apple.Foundation            0x00007fff85ee807e -[__NSOperationInternal start] + 698
11  com.apple.Foundation            0x00007fff85ee7d23 ____startOperations_block_invoke_2 + 99
12  libSystem.B.dylib               0x00007fff812bece8 _dispatch_call_block_and_release + 15
13  libSystem.B.dylib               0x00007fff8129d279 _dispatch_worker_thread2 + 231
14  libSystem.B.dylib               0x00007fff8129cbb8 _pthread_wqthread + 353
15  libSystem.B.dylib               0x00007fff8129ca55 start_wqthread + 13

My app is crashing in other places with exc_bad_access but this is code that it happens most with. All of the stack traces look similar and have something to do with CFHash.

Any help would be appreciated.