My application is crashing when one of the views is purged from memory because of low-memory condition. At least this is what I understand from the crashlog. It happens on numerous screens but only when opening a Facebook dialog (using the Facebook SDK). Basically, looks like the system sometimes runs out of memory when we need to present a Facebook dialog (e.g. to let user post something on the Facebook timeline).

Date/Time: 2012-03-14 19:47:33.819 +0000
OS Version: iPhone OS 5.1 (9B176)
Report Version: 104
Exception Type: EXC_BAD_ACCESS (SIGSEGV)
Exception Codes: KERN_INVALID_ADDRESS at 0x30000008
Crashed Thread: 0
Thread 0 name: Dispatch queue: com.apple.main-thread
Thread 0 Crashed:
0 libobjc.A.dylib 0x30f2bf78 objc_msgSend + 16
1 MyApp 0x00003c0e -LTBaseViewController viewDidUnload (LTBaseViewController.m:145)
2 MyApp 0x00004ea2 -LTBaseTableViewController viewDidUnload (LTBaseTableViewController.m:90)
3 UIKit 0x33766bd8 -[UIViewController unloadViewForced:] + 244
4 UIKit 0x338ae492 -[UIViewController purgeMemoryForReason:] + 58
5 Foundation 0x3071a4f8 __57-NSNotificationCenter addObserver:selector:name:object:_block_invoke_0 + 12
6 CoreFoundation 0x30e95540 ___CFXNotificationPost_block_invoke_0 + 64
7 CoreFoundation 0x30e21090 _CFXNotificationPost + 1400
8 Foundation 0x3068e3e4 -NSNotificationCenter postNotificationName:object:userInfo: + 60
9 Foundation 0x3068fc14 -NSNotificationCenter postNotificationName:object: + 24
10 UIKit 0x3387926a -UIApplication _performMemoryWarning + 74
11 UIKit 0x33879364 -UIApplication _receivedMemoryNotification + 168
12 libdispatch.dylib 0x36a12252 _dispatch_source_invoke + 510
13 libdispatch.dylib 0x36a0fb1e _dispatch_queue_invoke$VARIANT$up + 42
14 libdispatch.dylib 0x36a0fe64 _dispatch_main_queue_callback_4CF$VARIANT$up + 152
15 CoreFoundation 0x30e9c2a6 __CFRunLoopRun + 1262
16 CoreFoundation 0x30e1f49e CFRunLoopRunSpecific + 294
17 CoreFoundation 0x30e1f366 CFRunLoopRunInMode + 98
18 GraphicsServices 0x33fb6432 GSEventRunModal + 130
19 UIKit 0x336f5e76 UIApplicationMain + 1074
20 MyApp 0x00004818 main (main.m:16)
21 MyApp 0x000023b4 0x1000 + 5044

I checked and there are almost no memory leaks, e.g. when testing the app for an hour the total memory leaked was around 2-3Kb caused by some string-copying libraries. So I don't believe this is caused by the application. I guess that when the phone is not restarted for some time there are applications running in the background and when using Facebook SDK the memory becomes a problem and the system tries to recover the memory from random applications, including my application.

My question is, how can I prevent this crash from happening? How should I handle unloadViewForced on a view controller to make the app more robust in low-memory conditions? And lastly, am I right that this crashlog suggests the crash occurred because the system tried to free memory and my application didn't handle it properly?

Any help greatly appreciated.