I tried to assign a managed object (C) with its property another managed object (B) (a one-to-one relationship) in which this other managed object (B) has a to-many relationship with one other managed object (A). There is an error from this assignment in which I copied as follows:

#0  0x020e53a7 in ___forwarding___
#1  0x020c16c2 in __forwarding_prep_0___
#2  0x02078988 in CFRetain
#3  0x0207a728 in CFSetAddValue
#4  0x020c2fb2 in CFSetCreate
#5  0x01e51ce8 in -[_NSFaultingMutableSet copyWithZone:]
#6  0x020afcca in -[NSObject copy]
#7  0x01e50d22 in -[NSManagedObject(_NSInternalMethods) _newPropertiesForRetainedTypes:andCopiedTypes:preserveFaults:]
#8  0x01e51aa0 in -[NSManagedObject(_NSInternalMethods) _newAllPropertiesWithRelationshipFaultsIntact__]
#9  0x01e519b4 in -[NSManagedObjectContext(_NSInternalChangeProcessing) _establishEventSnapshotsForObject:]
#10 0x01e51866 in _PFFastMOCObjectWillChange
#11 0x01e516c5 in _PF_ManagedObject_WillChangeValueForKeyIndex
#12 0x01e51525 in _sharedIMPL_setvfk_core
#13 0x01e51483 in _PF_Handler_Public_SetProperty
#14 0x01e546d1 in -[NSManagedObject(_NSInternalMethods) _didChangeValue:forRelationship:named:withInverse:]
#15 0x0030ec1e in NSKVONotify
#16 0x002aae2a in -[NSObject(NSKeyValueObserverNotification) didChangeValueForKey:]
#17 0x01e5212f in _PF_ManagedObject_DidChangeValueForKeyIndex
#18 0x01e515b1 in _sharedIMPL_setvfk_core
#19 0x01e55827 in _svfk_5

I don't understand very well what the exact description of this error is. Can someone explain to me what it is and how to solve this one. Note that all other assignments in which the managed object B does not have any A items do not raise this error.

ObjectC *objectC = [NSEntityDescription insertNewObjectForEntityForName:@"ObjectC" inManagedObjectContext:managedObjectContext];
objectC.objectB = objectB;

Thank you in advance.

I added some more NSZombieEnabled/MallocStackLogging generated log:

2010-05-18 17:28:05.327 Foo[2069:207] *** -[CFSet retain]: message sent to deallocated instance 0x800c880
(gdb) shell malloc_history 207 0x800c880
malloc_history cannot examine process 207 because the process does not exist.
(gdb) shell malloc_history 2069 0x800c880

ALLOC 0x800c880-0x800c884 [size=5]: thread_a0a8c4e0 |start | main | UIApplicationMain | GSEventRun | GSEventRunModal | CFRunLoopRunInMode | CFRunLoopRunSpecific | __NSFireDelayedPerform | -[Step2ViewController downloadData] | -[Parser downloadVariantsWithPin:forTerminal:] | -[Parser parseByNSXMLParser:] | -[NSXMLParser parse] | xmlParseChunk | xmlIOParseDTD | _endElementNs | -[Parser parser:didEndElement:namespaceURI:qualifiedName:] | NSLog | NSLogv | _CFLogvEx | __CFLogCString | asl_send | _asl_send_level_message | asl_set_query | strdup | malloc | malloc_zone_malloc 
----
FREE  0x800c880-0x800c884 [size=5]: thread_a0a8c4e0 |start | main | UIApplicationMain | GSEventRun | GSEventRunModal | CFRunLoopRunInMode | CFRunLoopRunSpecific | __NSFireDelayedPerform | -[Step2ViewController downloadData] | -[Parser downloadVariantsWithPin:forTerminal:] | -[Parser parseByNSXMLParser:] | -[NSXMLParser parse] | xmlParseChunk | xmlIOParseDTD | _endElementNs | -[Parser parser:didEndElement:namespaceURI:qualifiedName:] | NSLog | NSLogv | _CFLogvEx | __CFLogCString | asl_send | _asl_send_level_message | asl_free | free 

ALLOC 0x800c860-0x800c8df [size=128]: thread_a0a8c4e0 |start | main | UIApplicationMain | GSEventRun | GSEventRunModal | CFRunLoopRunInMode | CFRunLoopRunSpecific | __NSFireDelayedPerform | -[Step2ViewController downloadData] | -[Parser downloadVariantsWithPin:forTerminal:] | -[Parser parseByNSXMLParser:] | -[NSXMLParser parse] | xmlParseChunk | xmlParseCharData | _characters | -[Parser parser:foundCharacters:] | NSLog | NSLogv | _CFLogvEx | __CFLogCString | asl_send | _asl_send_level_message | asl_set_query | asprintf | malloc | malloc_zone_malloc 
----
FREE  0x800c860-0x800c8df [size=128]: thread_a0a8c4e0 |start | main | UIApplicationMain | GSEventRun | GSEventRunModal | CFRunLoopRunInMode | CFRunLoopRunSpecific | __NSFireDelayedPerform | -[Step2ViewController downloadData] | -[Parser downloadVariantsWithPin:forTerminal:] | -[Parser parseByNSXMLParser:] | -[NSXMLParser parse] | xmlParseChunk | xmlParseCharData | _characters | -[Parser parser:foundCharacters:] | NSLog | NSLogv | _CFLogvEx | __CFLogCString | asl_send | _asl_send_level_message | asl_set_query | free 

ALLOC 0x800c860-0x800c8df [size=128]: thread_a0a8c4e0 |start | main | UIApplicationMain | GSEventRun | GSEventRunModal | CFRunLoopRunInMode | CFRunLoopRunSpecific | __NSFireDelayedPerform | -[Step2ViewController downloadData] | -[Parser downloadVariantsWithPin:forTerminal:] | -[Parser parseByNSXMLParser:] | -[NSXMLParser parse] | xmlParseChunk | xmlParseCharData | _characters | -[Parser parser:foundCharacters:] | NSLog | NSLogv | _CFLogvEx | __CFLogCString | asl_send | _asl_send_level_message | asprintf | malloc | malloc_zone_malloc 
----
FREE  0x800c860-0x800c8df [size=128]: thread_a0a8c4e0 |start | main | UIApplicationMain | GSEventRun | GSEventRunModal | CFRunLoopRunInMode | CFRunLoopRunSpecific | __NSFireDelayedPerform | -[Step2ViewController downloadData] | -[Parser downloadVariantsWithPin:forTerminal:] | -[Parser parseByNSXMLParser:] | -[NSXMLParser parse] | xmlParseChunk | xmlParseCharData | _characters | -[Parser parser:foundCharacters:] | NSLog | NSLogv | _CFLogvEx | __CFLogCString | asl_send | _asl_send_level_message | free 

ALLOC 0x800c860-0x800c8df [size=128]: thread_a0a8c4e0 |start | main | UIApplicationMain | GSEventRun | GSEventRunModal | CFRunLoopRunInMode | CFRunLoopRunSpecific | __NSFireDelayedPerform | -[Step2ViewController downloadData] | -[Parser downloadVariantsWithPin:forTerminal:] | -[Parser parseByNSXMLParser:] | -[NSXMLParser parse] | xmlParseChunk | xmlParseCharData | _characters | -[Parser parser:foundCharacters:] | NSLog | NSLogv | _CFLogvEx | __CFLogCString | asl_send | _asl_send_level_message | asprintf | malloc | malloc_zone_malloc 
----
FREE  0x800c860-0x800c8df [size=128]: thread_a0a8c4e0 |start | main | UIApplicationMain | GSEventRun | GSEventRunModal | CFRunLoopRunInMode | CFRunLoopRunSpecific | __NSFireDelayedPerform | -[Step2ViewController downloadData] | -[Parser downloadVariantsWithPin:forTerminal:] | -[Parser parseByNSXMLParser:] | -[NSXMLParser parse] | xmlParseChunk | xmlParseCharData | _characters | -[Parser parser:foundCharacters:] | NSLog | NSLogv | _CFLogvEx | __CFLogCString | asl_send | _asl_send_level_message | free 

ALLOC 0x800c860-0x800c8df [size=128]: thread_a0a8c4e0 |start | main | UIApplicationMain | GSEventRun | GSEventRunModal | CFRunLoopRunInMode | CFRunLoopRunSpecific | __NSFireDelayedPerform | -[Step2ViewController downloadData] | -[Parser downloadVariantsWithPin:forTerminal:] | -[Parser parseByNSXMLParser:] | -[NSXMLParser parse] | xmlParseChunk | xmlParseCharData | _characters | -[Parser parser:foundCharacters:] | NSLog | NSLogv | _CFLogvEx | __CFLogCString | asl_send | _asl_send_level_message | asprintf | malloc | malloc_zone_malloc 
----
FREE  0x800c860-0x800c8df [size=128]: thread_a0a8c4e0 |start | main | UIApplicationMain | GSEventRun | GSEventRunModal | CFRunLoopRunInMode | CFRunLoopRunSpecific | __NSFireDelayedPerform | -[Step2ViewController downloadData] | -[Parser downloadVariantsWithPin:forTerminal:] | -[Parser parseByNSXMLParser:] | -[NSXMLParser parse] | xmlParseChunk | xmlParseCharData | _characters | -[Parser parser:foundCharacters:] | NSLog | NSLogv | _CFLogvEx | __CFLogCString | asl_send | _asl_send_level_message | free 

ALLOC 0x800c860-0x800c8df [size=128]: thread_a0a8c4e0 |start | main | UIApplicationMain | GSEventRun | GSEventRunModal | CFRunLoopRunInMode | CFRunLoopRunSpecific | __NSFireDelayedPerform | -[Step2ViewController downloadData] | -[Parser downloadVariantsWithPin:forTerminal:] | -[Parser parseByNSXMLParser:] | -[NSXMLParser parse] | xmlParseChunk | xmlParseCharData | _characters | -[Parser parser:foundCharacters:] | NSLog | NSLogv | _CFLogvEx | __CFLogCString | asl_send | _asl_send_level_message | asprintf | malloc | malloc_zone_malloc 
----
FREE  0x800c860-0x800c8df [size=128]: thread_a0a8c4e0 |start | main | UIApplicationMain | GSEventRun | GSEventRunModal | CFRunLoopRunInMode | CFRunLoopRunSpecific | __NSFireDelayedPerform | -[Step2ViewController downloadData] | -[Parser downloadVariantsWithPin:forTerminal:] | -[Parser parseByNSXMLParser:] | -[NSXMLParser parse] | xmlParseChunk | xmlParseCharData | _characters | -[Parser parser:foundCharacters:] | NSLog | NSLogv | _CFLogvEx | __CFLogCString | asl_send | _asl_send_level_message | free 

ALLOC 0x800c860-0x800c8df [size=128]: thread_a0a8c4e0 |start | main | UIApplicationMain | GSEventRun | GSEventRunModal | CFRunLoopRunInMode | CFRunLoopRunSpecific | __NSFireDelayedPerform | -[Step2ViewController downloadData] | -[Parser downloadVariantsWithPin:forTerminal:] | -[Parser parseByNSXMLParser:] | -[NSXMLParser parse] | xmlParseChunk | xmlParseCharData | _characters | -[Parser parser:foundCharacters:] | NSLog | NSLogv | _CFLogvEx | __CFLogCString | asl_send | _asl_send_level_message | asprintf | malloc | malloc_zone_malloc 
----
FREE  0x800c860-0x800c8df [size=128]: thread_a0a8c4e0 |start | main | UIApplicationMain | GSEventRun | GSEventRunModal | CFRunLoopRunInMode | CFRunLoopRunSpecific | __NSFireDelayedPerform | -[Step2ViewController downloadData] | -[Parser downloadVariantsWithPin:forTerminal:] | -[Parser parseByNSXMLParser:] | -[NSXMLParser parse] | xmlParseChunk | xmlParseCharData | _characters | -[Parser parser:foundCharacters:] | NSLog | NSLogv | _CFLogvEx | __CFLogCString | asl_send | _asl_send_level_message | free 

ALLOC 0x800c700-0x800c893 [size=404]: thread_a0a8c4e0 |start | main | UIApplicationMain | GSEventRun | GSEventRunModal | CFRunLoopRunInMode | CFRunLoopRunSpecific | __NSFireDelayedPerform | -[Step2ViewController downloadData] | -[Parser downloadVariantsWithPin:forTerminal:] | -[Parser parseByNSXMLParser:] | -[NSXMLParser parse] | xmlParseChunk | xmlIOParseDTD | _startElementNs | -[Parser parser:didStartElement:namespaceURI:qualifiedName:attributes:] | NSLog | NSLogv | _CFLogvEx | __CFLogCString | CFCalendarDecomposeAbsoluteTime | _CFCalendarDecomposeAbsoluteTimeV | __CFCalendarSetupCal | __CFCalendarCreateUCalendar | ucal_open | icu::Calendar::createInstance(icu::TimeZone*, icu::Locale const&, UErrorCode&) | malloc | malloc_zone_malloc 
----
FREE  0x800c700-0x800c893 [size=404]: thread_a0a8c4e0 |start | main | UIApplicationMain | GSEventRun | GSEventRunModal | CFRunLoopRunInMode | CFRunLoopRunSpecific | __NSFireDelayedPerform | -[Step2ViewController downloadData] | -[Parser downloadVariantsWithPin:forTerminal:] | -[Parser parseByNSXMLParser:] | -[NSXMLParser parse] | xmlParseChunk | xmlIOParseDTD | _startElementNs | -[Parser parser:didStartElement:namespaceURI:qualifiedName:attributes:] | NSLog | NSLogv | _CFLogvEx | __CFLogCString | _CFRelease | free 

ALLOC 0x800c880-0x800c8c7 [size=72]: thread_a0a8c4e0 |start | main | UIApplicationMain | GSEventRun | GSEventRunModal | CFRunLoopRunInMode | CFRunLoopRunSpecific | __NSFireDelayedPerform | -[Step2ViewController downloadData] | -[Parser downloadVariantsWithPin:forTerminal:] | -[Parser parseByNSXMLParser:] | -[NSXMLParser parse] | xmlParseChunk | xmlIOParseDTD | _startElementNs | -[Parser parser:didStartElement:namespaceURI:qualifiedName:attributes:] | +[NSEntityDescription insertNewObjectForEntityForName:inManagedObjectContext:] | +[NSManagedObject(_PFDynamicAccessorsAndPropertySupport) allocWithEntity:] | _PFAllocateObject | malloc_zone_calloc 
----
FREE  0x800c880-0x800c8c7 [size=72]: thread_a0a8c4e0 |start | main | UIApplicationMain | GSEventRun | GSEventRunModal | CFRunLoopRunInMode | CFRunLoopRunSpecific | __CFRunLoopDoObservers | _performRunLoopAction | -[_PFManagedObjectReferenceQueue _processReferenceQueue:] | _PFDeallocateObject | malloc_zone_free 

ALLOC 0x800c880-0x800c8a7 [size=40]: thread_a0a8c4e0 |start | main | UIApplicationMain | GSEventRun | GSEventRunModal | CFRunLoopRunInMode | CFRunLoopRunSpecific | __CFRunLoopDoObservers | CA::Transaction::observer_callback(__CFRunLoopObserver*, unsigned long, void*) | CA::Transaction::commit() | CA::Context::commit_transaction(CA::Transaction*) | CALayerDisplayIfNeeded | -[TileLayer display] | -[CALayer _display] | CABackingStoreUpdate | backing_callback(CGContext*, void*) | WebCore::TiledSurface::drawLayer(CALayer*, CGContext*) | WKWindowDrawRect | WKViewDisplayRect | _WKViewDraw(CGContext*, WKView*, CGRect) | _WKViewDraw(CGContext*, WKView*, CGRect) | _WKViewDraw(CGContext*, WKView*, CGRect) | _WKViewDraw(CGContext*, WKView*, CGRect) | _WKViewDraw(CGContext*, WKView*, CGRect) | -[WebHTMLView drawSingleRect:] | -[WebFrame(WebInternal) _drawRect:contentsOnly:] | WebCore::FrameView::paintContents(WebCore::GraphicsContext*, WebCore::IntRect const&) | WebCore::RenderLayer::paint(WebCore::GraphicsContext*, WebCore::IntRect const&, WebCore::PaintRestriction, WebCore::RenderObject*) | WebCore::RenderLayer::paintLayer(WebCore::RenderLayer*, WebCore::GraphicsContext*, WebCore::IntRect const&, bool, WebCore::PaintRestriction, WebCore::RenderObject*, bool, bool) | WebCore::RenderLayer::paintLayer(WebCore::RenderLayer*, WebCore::GraphicsContext*, WebCore::IntRect const&, bool, WebCore::PaintRestriction, WebCore::RenderObject*, bool, bool) | WebCore::RenderBlock::paint(WebCore::RenderObject::PaintInfo&, int, int) | WebCore::RenderBlock::paintObject(WebCore::RenderObject::PaintInfo&, int, int) | WebCore::RenderBlock::paintChildren(WebCore::RenderObject::PaintInfo&, int, int) | WebCore::RenderBlock::paint(WebCore::RenderObject::PaintInfo&, int, int) | WebCore::RenderBlock::paintObject(WebCore::RenderObject::PaintInfo&, int, int) | WebCore::RenderBlock::paintChildren(WebCore::RenderObject::PaintInfo&, int, int) | WebCore::RenderBlock::paint(WebCore::RenderObject::PaintInfo&, int, int) | WebCore::RenderBlock::paintObject(WebCore::RenderObject::PaintInfo&, int, int) | WebCore::RenderBlock::paintChildren(WebCore::RenderObject::PaintInfo&, int, int) | WebCore::RenderBlock::paint(WebCore::RenderObject::PaintInfo&, int, int) | WebCore::RenderBlock::paintObject(WebCore::RenderObject::PaintInfo&, int, int) | WebCore::RenderFlow::paintLines(WebCore::RenderObject::PaintInfo&, int, int) | WebCore::RootInlineBox::paint(WebCore::RenderObject::PaintInfo&, int, int) | WebCore::InlineFlowBox::paint(WebCore::RenderObject::PaintInfo&, int, int) | WebCore::InlineTextBox::paint(WebCore::RenderObject::PaintInfo&, int, int) | WebCore::paintTextWithShadows(WebCore::GraphicsContext*, WebCore::Font const&, WebCore::TextRun const&, int, int, WebCore::IntPoint const&, int, int, int, int, WebCore::ShadowData*, bool) | WebCore::GraphicsContext::drawText(WebCore::Font const&, WebCore::TextRun const&, WebCore::IntPoint const&, int, int) | WebCore::Font::drawSimpleText(WebCore::GraphicsContext*, WebCore::TextRun const&, WebCore::FloatPoint const&, int, int) const | WebCore::Font::drawGlyphBuffer(WebCore::GraphicsContext*, WebCore::GlyphBuffer const&, WebCore::TextRun const&, WebCore::FloatPoint&) const | WebCore::Font::drawGlyphs(WebCore::GraphicsContext*, WebCore::SimpleFontData const*, WebCore::GlyphBuffer const&, int, int, WebCore::FloatPoint const&, bool) const | CGGStateSetFont | maybeCopyTextState | calloc | malloc_zone_calloc 
----
FREE  0x800c880-0x800c8a7 [size=40]: thread_a0a8c4e0 |start | main | UIApplicationMain | GSEventRun | GSEventRunModal | CFRunLoopRunInMode | CFRunLoopRunSpecific | __CFRunLoopDoObservers | CA::Transaction::observer_callback(__CFRunLoopObserver*, unsigned long, void*) | CA::Transaction::commit() | CA::Context::commit_transaction(CA::Transaction*) | CALayerDisplayIfNeeded | -[TileLayer display] | -[CALayer _display] | CABackingStoreUpdate | backing_callback(CGContext*, void*) | WebCore::TiledSurface::drawLayer(CALayer*, CGContext*) | WKWindowDrawRect | WKViewDisplayRect | _WKViewDraw(CGContext*, WKView*, CGRect) | _WKViewDraw(CGContext*, WKView*, CGRect) | _WKViewDraw(CGContext*, WKView*, CGRect) | _WKViewDraw(CGContext*, WKView*, CGRect) | _WKViewDraw(CGContext*, WKView*, CGRect) | -[WebHTMLView drawSingleRect:] | -[WebFrame(WebInternal) _drawRect:contentsOnly:] | WebCore::FrameView::paintContents(WebCore::GraphicsContext*, WebCore::IntRect const&) | WebCore::RenderLayer::paint(WebCore::GraphicsContext*, WebCore::IntRect const&, WebCore::PaintRestriction, WebCore::RenderObject*) | WebCore::RenderLayer::paintLayer(WebCore::RenderLayer*, WebCore::GraphicsContext*, WebCore::IntRect const&, bool, WebCore::PaintRestriction, WebCore::RenderObject*, bool, bool) | WebCore::RenderLayer::paintLayer(WebCore::RenderLayer*, WebCore::GraphicsContext*, WebCore::IntRect const&, bool, WebCore::PaintRestriction, WebCore::RenderObject*, bool, bool) | WebCore::RenderBlock::paint(WebCore::RenderObject::PaintInfo&, int, int) | WebCore::RenderBlock::paintObject(WebCore::RenderObject::PaintInfo&, int, int) | WebCore::RenderBlock::paintChildren(WebCore::RenderObject::PaintInfo&, int, int) | WebCore::RenderBlock::paint(WebCore::RenderObject::PaintInfo&, int, int) | WebCore::RenderBlock::paintObject(WebCore::RenderObject::PaintInfo&, int, int) | WebCore::RenderBlock::paintChildren(WebCore::RenderObject::PaintInfo&, int, int) | WebCore::RenderBlock::paint(WebCore::RenderObject::PaintInfo&, int, int) | WebCore::RenderBlock::paintObject(WebCore::RenderObject::PaintInfo&, int, int) | WebCore::RenderBlock::paintChildren(WebCore::RenderObject::PaintInfo&, int, int) | WebCore::RenderBlock::paint(WebCore::RenderObject::PaintInfo&, int, int) | WebCore::RenderBlock::paintObject(WebCore::RenderObject::PaintInfo&, int, int) | WebCore::RenderFlow::paintLines(WebCore::RenderObject::PaintInfo&, int, int) | WebCore::RootInlineBox::paint(WebCore::RenderObject::PaintInfo&, int, int) | WebCore::InlineFlowBox::paint(WebCore::RenderObject::PaintInfo&, int, int) | WebCore::InlineTextBox::paint(WebCore::RenderObject::PaintInfo&, int, int) | WebCore::paintTextWithShadows(WebCore::GraphicsContext*, WebCore::Font const&, WebCore::TextRun const&, int, int, WebCore::IntPoint const&, int, int, int, int, WebCore::ShadowData*, bool) | WebCore::GraphicsContext::restorePlatformState() | CGContextRestoreGState | CGGStackRestore | CGGStateRelease | textStateRelease | free 

ALLOC 0x800c880-0x800c8bf [size=64]: thread_a0a8c4e0 |start | main | UIApplicationMain | GSEventRun | GSEventRunModal | CFRunLoopRunInMode | CFRunLoopRunSpecific | CA::timer_callback(__CFRunLoopTimer*, void*) | run_animation_callbacks(double, void*) | -[UIViewAnimationState animationDidStop:finished:] | -[UIViewAnimationState sendDelegateAnimationDidStop:finished:] | -[UINavigationTransitionView _navigationTransitionDidStop] | -[UIView(Hierarchy) removeFromSuperview] | -[UITextField resignFirstResponder] | -[UIFieldEditor resignFirstResponder] | -[UIKeyboardImpl setDelegate:] | -[UIKeyboardImpl setDelegate:force:] | -[UITextInteractionAssistant setGestureRecognizers] | -[UITextInteractionAssistant addTwoFingerRangedSelectRecognizer] | -[UILongPressGestureRecognizer initWithTarget:action:] | -[__NSPlaceholderSet init] | -[__NSPlaceholderSet initWithCapacity:] | __CFSetInit | _CFRuntimeCreateInstance | malloc_zone_malloc