Debugging SIGKILL when opening app after multitasking quit

Question

Debugging SIGKILL when opening app after multitasking quit

Hi everyone,

I'm having some trouble trying to debug a complication with an application I'm working on.

Now, we've not added any multitasking functionality - infact most of it is as Xcode creates it. However, if I launch the app in the simulator, quit the app completely (via the double home button tap) then launch it again it all falls over with a SIGKILL complaint.

The thing that's really causing me a problem is that all of the crash reports and profiling methods all seem to stop 'following' the app once I fully quit it and thus I get no feedback about what's causing the application to crash.

Am I missing something?

Thanks.
Greg.

Macbook Pro, Mac OS X (10.6.6)

Posted on Mar 19, 2011 9:18 AM

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Answer 1

Best reply

xnav

Level 5

7,089 points

Mar 19, 2011 1:43 PM in response to GregularExpressions

Are you sure about when you get SIGKILL? When you double-tap Home and remove an app from the task list the mechanism used by iOS to stop it is a SIGKILL of the process.

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Answer 2

Mar 20, 2011 3:40 AM in response to xnav

Hi xnav, thanks for responding.

I had done some research and come across that information, the reason I decided to post still was that Xcode doesn't report the SIGKILL at the point I fully close the application in the simulator but actually when I relaunch the app. Perhaps it's only noticing then and obscuring whatever the real cause of the crash is?

This behaviour also occurs on a physical device, the whole thing locks up. It's almost certainly something incorrect I'm doing somewhere but the absence of any debug help is making it difficult to narrow down.

Greg.

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Answer 3

xnav

Level 5

7,089 points

Mar 20, 2011 7:49 AM in response to GregularExpressions

This behaviour also occurs on a physical device,

The SIGKILL would be normal on the device also.

the whole thing locks up.

This is not normal, you did not mention that this happens on the simulator? Are you actually running something (eg location services) in background or do you just suspend?

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Answer 4

Mar 20, 2011 10:11 AM in response to xnav

Yes it does occur in the simulator too, no we're doing nothing at all on suspend or resume. Really I just need a way to tell the diagnostic instruments to continue monitoring the simulator even once I've quit the app.

That way I'll hopefully get a crash log when it fails.

Greg.

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Answer 5

xnav

Level 5

7,089 points

Mar 20, 2011 12:31 PM in response to GregularExpressions

Try putting a breakpoint in applicationWillTerminate: and stepping through when it gets triggered.

If it never triggers try setting UIApplicationExitsOnSuspend to YES in the Info.plist. This should revert the exit logic back to pre-multitasking behavior.

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Answer 6

Mar 21, 2011 8:37 AM in response to xnav

Well, this is odd. Alarm bells started going off when we created a brand new tab bar application (as Xcode creates it) and it was also crashing. Implying that it wasn't something we were specifically doing.

I decided to try running the application outside of Xcode's reach so I built to the device, then removed the 30 pin cable thus leaving the iPhone running the app 'stand-alone' as it were. It then doesn't crash on relaunch after multitasking quit! I was also able to replicate this in the simulator by clicking the stop button once the app had started running on the simulator.

Seems very odd, something Xcode is doing or monitoring causes it to hang. Perhaps an Xcode 4 bug/foible?

Anyway, thanks for your help.

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Answer 7

xnav

Level 5

7,089 points

Mar 21, 2011 8:43 AM in response to GregularExpressions

I have not seen a hang with Xcode3 or 4.

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Answer 8

Mar 21, 2011 10:54 AM in response to xnav

So to clarify, if you do the following you do not get any sort of crash?

- Create new tab navigation application.
- Click the 'play' button to run the new application in the simulator.
- Click the home button to exit the app.
- Trigger the multitasking bar and close the app entirely.
- Launch the tab bar app again.

Every time we repeat the above (skipping the creation of the project once it's down of course) the simulator falls over and we see the sigkill in Xcode.

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Answer 9

xnav

Level 5

7,089 points

Mar 21, 2011 11:29 AM in response to GregularExpressions

* Create new tab navigation application.
* Click the 'play' button to run the new application in the simulator.
* Click the home button to exit the app.
* Trigger the multitasking bar and close the app entirely.
* Launch the tab bar app again.
No, however, when I relaunch I get a prompt to stop the running debug session. I get the following in the OSX Console App.


3/21/11 8:21:01 AM, Mar 21 com.apple.launchd.peruser.501[161] (UIKitApplication:xnav.hangTest[0x4159][581]) Exited: Killed
3/21/11 8:21:01 AM, Mar 21 SpringBoard[561] Application 'hangTest' exited abnormally with signal 9: Killed

This in Xcode4 debug console:


This GDB was configured as "x86_64-apple-darwin".Attaching to process 581.
kill
quit
Program ended with exit code: 0

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Answer 10

Mar 21, 2011 1:17 PM in response to xnav

hmm, that's very odd.

I'm able to replicate my crashes on three separate machines, all creating their own tab bar project.

In the OSX console I see the below but nothing much of interest in the Xcode console.

21/03/2011 20:11:03 SpringBoard [358]Error deserializing wallpaper image: 
Error Domain=CPBitmapErrorDomain Code=0 "The operation couldn’t be completed. (CPBitmapErrorDomain 
error 0 - No data provided to CPBitmapCreateImagesFromData)" UserInfo=0x70c8290 {NSDescription=No 
data provided to CPBitmapCreateImagesFromData}