NSDrawer delegate pointing to deallocated object?
- by Isaac
A user has sent in a crash report with the stack trace listed below (I have not been able to reproduce the crash myself, but every other crash this user has reported has been a valid bug, even when I couldn't reproduce the effect). The application is a reference-counted Objective-C/Cocoa app.
If I am interpreting it correctly, the crash is caused by attempting to send a drawerDidOpen: message to a deallocated object. The only object that should be receiving drawerDidOpen: is the drawer's delegate object (nowhere does any object register to receive drawer notifications), and the drawer's delegate object is instantiated via the XIB/NIB file, wired to the delegate outlet of the drawer, and not referenced anywhere else.
Given that, how can I protect against the delegate getting dealloc'd before the drawer notification? Or, alternately, what have I misinterpreted that might be causing the crash?
Crash log/stack trace:
Exception Type: EXC_BAD_ACCESS (SIGSEGV)
Exception Codes: KERN_INVALID_ADDRESS at 0x0000000000000010
Crashed Thread: 0 Dispatch queue: com.apple.main-thread
Application Specific Information:
objc_msgSend() selector name: drawerDidOpen:
Thread 0 Crashed: Dispatch queue: com.apple.main-thread
0 libobjc.A.dylib 0x00007fff8272011c objc_msgSend + 40
1 com.apple.Foundation 0x00007fff87d0786e _nsnote_callback + 167
2 com.apple.CoreFoundation 0x00007fff831bcaea __CFXNotificationPost + 954
3 com.apple.CoreFoundation 0x00007fff831a9098 _CFXNotificationPostNotification + 200
4 com.apple.Foundation 0x00007fff87cfe7d8 -[NSNotificationCenter postNotificationName:object:userInfo:] + 101
5 com.apple.AppKit 0x00007fff8512e944 _NSDrawerObserverCallBack + 840
6 com.apple.CoreFoundation 0x00007fff831d40d7 __CFRunLoopDoObservers + 519
7 com.apple.CoreFoundation 0x00007fff831af8c4 CFRunLoopRunSpecific + 548
8 com.apple.HIToolbox 0x00007fff839b8ada RunCurrentEventLoopInMode + 333
9 com.apple.HIToolbox 0x00007fff839b883d ReceiveNextEventCommon + 148
10 com.apple.HIToolbox 0x00007fff839b8798 BlockUntilNextEventMatchingListInMode + 59
11 com.apple.AppKit 0x00007fff84de8a2a _DPSNextEvent + 708
12 com.apple.AppKit 0x00007fff84de8379 -[NSApplication nextEventMatchingMask:untilDate:inMode:dequeue:] + 155
13 com.apple.AppKit 0x00007fff84dae05b -[NSApplication run] + 395
14 com.apple.AppKit 0x00007fff84da6d7c NSApplicationMain + 364
15 (my app's identifier) 0x0000000100001188 start + 52
