My app has some kind of Zombie problem. (Not an NSZombie problem. Like, a coming-back-from-the-dead problem.)
I first noticed that after a debugging session, when I would go for a run the music on my iPhone would pause every ~7 minutes, and when I’d unlock the device the app name would be flashing red in the status bar as though it had just crashed. Sometimes there would even be phantom sound from the app, like it was still running in the background somehow.
Manually quit the app, continue. Still get the intermittent audio artifacts even though the app no longer appears in my list of running apps.
When I plug back in, this is in the console for each time the app zombified and restarted itself. It looks just like a normal launch of the app! What the? What could be triggering my app to restart itself?
Console:
Apr 26 12:10:01 unknown Breakout[2658] <Warning>: cocos2d: cocos2d v1.1.0-beta2b
Apr 26 12:10:01 unknown Breakout[2658] <Warning>: cocos2d: Using Director Type:CCDirectorDisplayLink
Apr 26 12:10:01 unknown Breakout[2658] <Warning>: cocos2d: OS version: 5.1 (0x05010000)
Apr 26 12:10:01 unknown Breakout[2658] <Warning>: cocos2d: GL_VENDOR: Imagination Technologies
Apr 26 12:10:01 unknown Breakout[2658] <Warning>: cocos2d: GL_RENDERER: PowerVR SGX 535
Apr 26 12:10:01 unknown Breakout[2658] <Warning>: cocos2d: GL_VERSION: OpenGL ES-CM 1.1 IMGSGX535-63.24
Apr 26 12:10:01 unknown Breakout[2658] <Warning>: cocos2d: GL_MAX_TEXTURE_SIZE: 2048
Apr 26 12:10:01 unknown Breakout[2658] <Warning>: cocos2d: GL_MAX_MODELVIEW_STACK_DEPTH: 16
// etc //
Apr 26 12:10:01 unknown kernel[0] <Debug>: launchd[2658] Builtin profile: container (sandbox)
Apr 26 12:10:01 unknown kernel[0] <Debug>: launchd[2658] Container: /private/var/mobile/Applications/FFEB0A26-06D1-4C46-8AE5-C60582D09A1D [69] (sandbox)
Apr 26 12:10:01 unknown Breakout[2658] <Warning>: Audio session details
Apr 26 12:10:01 unknown Breakout[2658] <Warning>: Audio Input Available? YES
Apr 26 12:10:01 unknown mediaserverd[32] <Warning>: 12:10:01.641 <SystemSoundServer> WARNING translating HAL error: 561214578
Apr 26 12:10:01 unknown Breakout[2658] <Warning>: Max Possible Inputs 15151420
Apr 26 12:10:01 unknown Breakout[2658] <Warning>: Outputs 2
Apr 26 12:10:01 unknown Breakout[2658] <Warning>: Device sample rate 44100.000000
Apr 26 12:10:01 unknown Breakout[2658] <Warning>: Hardware buffer size 0.023220
// etc //
Apr 26 12:10:33 unknown SpringBoard[52] <Notice>: Posting 'com.apple.iokit.hid.displayStatus' notifyState=1
Apr 26 12:10:33 unknown UserEventAgent[12] <Warning>: DEBUG: Changing screen blanked state: 0
Apr 26 12:10:33 unknown SpringBoard[52] <Notice>: MultitouchHID: detection mode: 255->0 (deferring until bootloaded)
Apr 26 12:10:33 unknown SpringBoard[52] <Notice>: MultitouchHID: device bootloaded
Apr 26 12:10:33 unknown SpringBoard[52] <Notice>: MultitouchHID: detection mode: 0->0
Apr 26 12:10:34 unknown kernel[0] <Debug>: set_crc_notification_state 0
Apr 26 12:10:34 unknown ReportCrash[2659] <Notice>: Formulating crash report for process Breakout[2658]
>
Apr 26 12:10:34 unknown SpringBoard[52] <Warning>: pid_suspend failed for [2658]: Unknown error: -1, Unknown error: -1
Apr 26 12:10:34 unknown SpringBoard[52] <Warning>: Could not set priority of [2658] to 4096, priority: No such process
Apr 26 12:10:34 unknown com.apple.launchd[1] <Warning>: (UIKitApplication:com.charliewilliams.Breakout[0xd5ad]) Job appears to have crashed: Trace/BPT trap: 5
Apr 26 12:10:34 unknown SpringBoard[52] <Warning>: Application 'Breakout' exited abnormally with signal 5: Trace/BPT trap: 5
Apr 26 12:10:35 unknown ReportCrash[2659] <Error>: libMobileGestalt computeUniqueDeviceID: total time for bb to return imei: 0
Apr 26 12:10:35 unknown ReportCrash[2659] <Notice>: Saved crashreport to /var/mobile/Library/Logs/CrashReporter/Breakout_2012-04-26-121033_Tortuga-Gigante.plist using uid: 0 gid: 0, synthetic_euid: 501 egid: 0
Explanation of the solution: It turned out to be simple – 1. I was shutting down my audio session in dealloc but not in applicationDidEnterBackground. And since I’m using kaudiosessioncategory_playandrecord that seems to tell iOS to restart the app if it crashes in the background.
Now, why is it crashing in the background? …well, that’s my next task.
The app may have a background voip flag set. If it does, the OS will restart the app if it exits abnormally (or when the device restarts).