Cocos2d, iOS and XCode: how can I debug/understand this stacktrace? - ios

Question

I am developing a Cocos2d 2.0 game and can't quiet get around on why my App is crashing.
The console output is as following:
2013-02-08 10:52:08.298 AppName[994:15203] cocos2d: CCSpriteBatchNode: resizing TextureAtlas capacity from [29] to [40].
2013-02-08 10:52:08.299 AppName[994:15203] cocos2d: CCSpriteBatchNode: resizing TextureAtlas capacity from [40] to [54].
2013-02-08 10:52:08.300 AppName[994:15203] cocos2d: CCSpriteBatchNode: resizing TextureAtlas capacity from [54] to [73].
(lldb)
The "game scene" loads and crashes immediately. I can see that has to do with CCSpriteBatchNode but I have absolutely no idea on where exactly the code fails. If I add a breakpoint it is not of much use as it will trigger way to many times before reaching the exact moment when it fails.
What does (lldb) mean? Is there a way to have a more explicit stacktrace? I used to work in Java and Eclipse and there was possible to read in English the full stacktrace.. I whish it was as simle using XCode.

Answer 1

You are probably getting one of those nasty EXC_BAD_ACCESS buggers. nope, no exceptions. For example
#try {
// this is caught
// NSMutableArray *ar = [NSMutableArray array];
// [ar addObject:nil];
// this is caught
// NSMutableDictionary *dic = [NSMutableDictionary dictionary] ;
// [dic setObject:#"a" forKey:nil];
// this crashes , no exception
// NSLog("21");
// and this will cause a message sent to a dealloced instance (zombie).
// no exception, just a bad crash.
GEIntEffect *eff = [GEIntEffect intEffectWithString:#"*1.1"
withOrder:geEffectOrderFightMagic
andImpact:geEffectImpactPositive];
[eff release];
NSLog([eff description]);
[[GameSpecs sharedGameSpecs] setupBattlesInitialSpecs];
// with a comment
}
#catch (NSException *e) {
MPLOGERROR(#"*** an exception [%#] occured while writing the game specs, continuing.\n%#\n\n%#",
e.description,
e.callStackSymbols,
e.callStackReturnAddresses);
}
the first two are trapped and the log statement is explicit, spewing me the stack trace in the log. The NSLog("21") ... ooops, forgot the "#" crashes badly. The fourth example, wrongly releasing an object before use ... well u know what that does. I can only suggest you :
check all your warnings (i had one on the bad NSLog)
Profile your app for zombies, using instruments. A message sent to a dealloced object will also crash nasty.
although there is a performance penalty, ie dont overdo it, some strategically placed try/catch blocks can help immensely. Typically, i wrap any 'update' method in Debug, removing the try/catch in Release.
recheck all your warnings :)
best of luck.
ps : here is what the log looks like when i trap an exception. The offsets are not to a 'line of code', symbolicating allows for that. But, typically, i have enough info from the trace to narrow it down to real close. :
-[MPGameSequencer sequenceInitState] : * an exception [* -[__NSArrayM insertObject:atIndex:]: object cannot be nil] occured while writing the game specs, continuing.
(
0 CoreFoundation 0x028de02e __exceptionPreprocess + 206
1 libobjc.A.dylib 0x022bbe7e objc_exception_throw + 44
2 CoreFoundation 0x02891b6a -[__NSArrayM insertObject:atIndex:] + 314
3 CoreFoundation 0x02891a20 -[__NSArrayM addObject:] + 64
4 Battles 0x00221c49 -[MPGameSequencer sequenceInitState] + 809
5 Battles 0x0021e359 -[MPGameSequencer nextFrame:] + 121
6 Battles 0x00067324 -[CCTimer update:] + 308
7 Battles 0x00070444 -[CCScheduler update:] + 772
8 Battles 0x0009dc81 -[CCDirectorIOS drawScene] + 225
9 Battles 0x0009ef44 -[CCDirectorDisplayLink mainLoop:] + 52
10 QuartzCore 0x007c32d2 _ZN2CA7Display11DisplayLink8dispatchEyy + 110
11 QuartzCore 0x007c375f _ZN2CA7Display16TimerDisplayLink8callbackEP16__CFRunLoopTimerPv + 161
12 CoreFoundation 0x0289d376 __CFRUNLOOP_IS_CALLING_OUT_TO_A_TIMER_CALLBACK_FUNCTION__ + 22
13 CoreFoundation 0x0289ce06 __CFRunLoopDoTimer + 534
14 CoreFoundation 0x02884a82 __CFRunLoopRun + 1810
15 CoreFoundation 0x02883f44 CFRunLoopRunSpecific + 276
16 CoreFoundation 0x02883e1b CFRunLoopRunInMode + 123
17 GraphicsServices 0x035e57e3 GSEventRunModal + 88
18 GraphicsServices 0x035e5668 GSEventRun + 104
19 UIKit 0x00e9165c UIApplicationMain + 1211
20 Battles 0x000c2bce main + 270
21 Battles 0x00002a15 start + 53
)