Users have been reporting a SIGSEGV crash that I’m having great difficulty reproducing – it happens relatively often for them, but I’ve never been able to reproduce it. From reading other StackOverflow posts, I know I’m supposed to turn NSZombies on to find the zombie object, but no matter what I do in Instruments I can’t get any zombies to show up.
Note that I am using ARC.
Can anyone make any sense out of these two crash reports so I at least know where to start looking for the zombie? And does anyone have any tips on how to get the zombie to show up in Instruments? Thanks!
Crash report #1:
0 MyApp 0x000e4972 testflight_backtrace + 238
1 MyApp 0x000e565c TFSignalHandler + 264
2 libsystem_c.dylib 0x31cd37ec _sigtramp + 48
3 UIKit 0x33e47bde -[UIViewController unloadViewForced:] + 250
4 UIKit 0x33f8f498 -[UIViewController purgeMemoryForReason:] + 64
5 Foundation 0x37f264fe __57-[NSNotificationCenter addObserver:selector:name:object:]_block_invoke_0 + 18
6 CoreFoundation 0x376c8546 ___CFXNotificationPost_block_invoke_0 + 70
7 CoreFoundation 0x37654096 _CFXNotificationPost + 1406
8 Foundation 0x37e9a3ea -[NSNotificationCenter postNotificationName:object:userInfo:] + 66
9 Foundation 0x37e9bc1a -[NSNotificationCenter postNotificationName:object:] + 30
10 UIKit 0x33f5a270 -[UIApplication _performMemoryWarning] + 80
11 UIKit 0x33f5a36a -[UIApplication _receivedMemoryNotification] + 174
12 libdispatch.dylib 0x349572e0 _dispatch_source_invoke + 516
13 libdispatch.dylib 0x34954b80 _dispatch_queue_invoke$VARIANT$mp + 52
14 libdispatch.dylib 0x34954ec0 _dispatch_main_queue_callback_4CF$VARIANT$mp + 156
15 CoreFoundation 0x376cf2ac __CFRunLoopRun + 1268
16 CoreFoundation 0x376524a4 CFRunLoopRunSpecific + 300
17 CoreFoundation 0x3765236c CFRunLoopRunInMode + 104
18 GraphicsServices 0x3255f438 GSEventRunModal + 136
19 UIKit 0x33dd6e7c UIApplicationMain + 1080
20 MyApp 0x0001b65e main (main.m:16)
21 MyApp 0x000115af start + 39
Crash report #2:
0 MyApp 0x0018e972 testflight_backtrace + 238
1 MyApp 0x0018f65c TFSignalHandler + 264
2 libsystem_c.dylib 0x31d067ec _sigtramp + 48
3 UIKit 0x33e7abde -[UIViewController unloadViewForced:] + 250
4 UIKit 0x33fc2498 -[UIViewController purgeMemoryForReason:] + 64
5 MyApp 0x000ec988 -[MyTableController didReceiveMemoryWarning] (MyTableController.m:129)
6 MyApp 0x0010a8a8 -[FeaturedViewController didReceiveMemoryWarning] (FeaturedViewController.m:65)
7 Foundation 0x37f594fe __57-[NSNotificationCenter addObserver:selector:name:object:]_block_invoke_0 + 18
8 CoreFoundation 0x376fb546 ___CFXNotificationPost_block_invoke_0 + 70
9 CoreFoundation 0x37687096 _CFXNotificationPost + 1406
10 Foundation 0x37ecd3ea -[NSNotificationCenter postNotificationName:object:userInfo:] + 66
11 Foundation 0x37ecec1a -[NSNotificationCenter postNotificationName:object:] + 30
12 UIKit 0x33f8d270 -[UIApplication _performMemoryWarning] + 80
13 UIKit 0x33f8d36a -[UIApplication _receivedMemoryNotification] + 174
14 libdispatch.dylib 0x3498a2e0 _dispatch_source_invoke + 516
15 libdispatch.dylib 0x34987b80 _dispatch_queue_invoke$VARIANT$mp + 52
16 libdispatch.dylib 0x34987ec0 _dispatch_main_queue_callback_4CF$VARIANT$mp + 156
17 CoreFoundation 0x377022ac __CFRunLoopRun + 1268
18 CoreFoundation 0x376854a4 CFRunLoopRunSpecific + 300
19 CoreFoundation 0x3768536c CFRunLoopRunInMode + 104
20 GraphicsServices 0x32592438 GSEventRunModal + 136
21 UIKit 0x33e09e7c UIApplicationMain + 1080
22 MyApp 0x000c565e main (main.m:16)
23 MyApp 0x000bb5af start + 39
It looks like something is being done wrong when your app receives a memory warning. You can force this to happen on the simulator using the debug menu, or on the device by sending the (illegal in production code)
_performMemoryWarningmethod:You can put this on a repeating timer to regularly send the warnings. I’d advise wrapping this in an
#IFDEF DEBUGto prevent it making it into production.This won’t solve your problem, but it may help you to reproduce the crash, which is the vital first step.