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POUnderstanding a malloc_history dump
 

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  1. POUnderstanding a malloc_history dump
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    <p>If you have ever asked how can I debug releasing/alloc issues in objective-c, you will have came across these environment settings that can help track the problem down:</p> <ul> <li><code>NSZombieEnabled</code> - Keeps abjects around after release, so you can get pointers etc.</li> <li><code>MallocStackLogging</code> - keeps object history for reference later </li> <li><code>NSDebugEnabled</code></li> </ul> <p>You set all of these to <code>YES</code> in the 'environment' section of the 'arguments' tab in the 'executables' (found in group tree) info.</p> <p><HR></p> <p>So, Im getting this console output</p> <blockquote> <p>MyApp [<strong>4413</strong>:40b] -[CALayer retainCount]: message sent to deallocated instance <strong>0x4dbb170</strong></p> </blockquote> <p>then open terminal, while the debugger has forwarded the break and type:</p> <blockquote> <p>malloc_history <strong>4413 0x4dbb170</strong></p> </blockquote> <p>Then, I get a big text dump, and as far as I understand the important bit is this:</p> <p>1</p> <pre><code>ALLOC 0x4dbb160-0x4dbb171 [size=18]: thread_a0375540 |start | main | UIApplicationMain | GSEventRun | GSEventRunModal | CFRunLoopRunInMode | CFRunLoopRunSpecific | __CFRunLoopRun | __CFRunLoopDoTimer | __CFRUNLOOP_IS_CALLING_OUT_TO_A_TIMER_CALLBACK_FUNCTION__ | __NSFireDelayedPerform | -[todoListViewController drillDocumentMenu:] | -[documentListViewController drillIntoDocumentWithToDoRecord:] | -[documentViewController OpenTodoDocument:OfType:WithPath:] | -[documentViewController OpenDocumentOfType:WithPath:] | -[documentViewController managePDFDocumentWithPath:] | -[PDFDocument loadPDFDocumentWithPath:andTitle:] | -[PDFDocument getMetaData] | CGPDFDictionaryApplyFunction | ListDictionaryObjects(char const*, CGPDFObject*, void*) | NSLog | NSLogv | _CFLogvEx | __CFLogCString | asl_send | _asl_send_level_message | asl_set_query | strdup | malloc | malloc_zone_malloc </code></pre> <p>2</p> <pre><code>FREE 0x4dbb160-0x4dbb171 [size=18]: thread_a0375540 |start | main | UIApplicationMain | GSEventRun | GSEventRunModal | CFRunLoopRunInMode | CFRunLoopRunSpecific | __CFRunLoopRun | __CFRunLoopDoTimer | __CFRUNLOOP_IS_CALLING_OUT_TO_A_TIMER_CALLBACK_FUNCTION__ | __NSFireDelayedPerform | -[todoListViewController drillDocumentMenu:] | -[documentListViewController drillIntoDocumentWithToDoRecord:] | -[documentViewController OpenTodoDocument:OfType:WithPath:] | -[documentViewController OpenDocumentOfType:WithPath:] | -[documentViewController managePDFDocumentWithPath:] | -[PDFDocument loadPDFDocumentWithPath:andTitle:] | -[PDFDocument getMetaData] | CGPDFDictionaryApplyFunction | ListDictionaryObjects(char const*, CGPDFObject*, void*) | NSLog | NSLogv | _CFLogvEx | __CFLogCString | asl_send | _asl_send_level_message | asl_free | free </code></pre> <p>3</p> <pre><code>ALLOC 0x4dbb170-0x4dbb19f [size=48]: thread_a0375540 |start | main | UIApplicationMain | GSEventRun | GSEventRunModal | CFRunLoopRunInMode | CFRunLoopRunSpecific | __CFRunLoopRun | __CFRunLoopDoTimer | __CFRUNLOOP_IS_CALLING_OUT_TO_A_TIMER_CALLBACK_FUNCTION__ | __NSFireDelayedPerform | -[todoListViewController drillDocumentMenu:] | -[documentListViewController drillIntoDocumentWithToDoRecord:] | -[documentViewController OpenTodoDocument:OfType:WithPath:] | -[documentViewController OpenDocumentOfType:WithPath:] | -[documentViewController managePDFDocumentWithPath:] | -[ScrollViewWithPagingViewController init] | -[UIView init] | -[UIScrollView initWithFrame:] | -[UIView initWithFrame:] | UIViewCommonInitWithFrame | -[UIView _createLayerWithFrame:] | +[NSObject(NSObject) alloc] | +[NSObject(NSObject) allocWithZone:] | class_createInstance | _internal_class_createInstanceFromZone | calloc | malloc_zone_calloc </code></pre> <p><strong>What i don't understand though is if it the history was ALLOC,FREE,ALLOC then why does the error indicate that it was released (net +1 alloc)?</strong></p> <p><strong>or is my understanding of the dump wrong?</strong></p> <p><hr> EDIT (fresh run= different object pointers):</p> <p>Zombie Detection with instruments:</p> <p><img src="https://i140.photobucket.com/albums/r18/reeferx/zombies.png"/></p> <p>Why and how, does the retain count jump from 1 to -1?</p> <p>Looking at the backtrace of the Zombie, looks like the retain count is being called by: Quartz through release_root_if_unused</p> <p><img src="https://i140.photobucket.com/albums/r18/reeferx/stacktrace2.png"/> </p> <hr> <p>Edit: <strong>Solved</strong>- I was removing a view from super, then releasing it. Fixed by just releasing it.</p>
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