Re: Understanding Application crash
Re: Understanding Application crash
- Subject: Re: Understanding Application crash
- From: Fritz Anderson <email@hidden>
- Date: Tue, 25 Mar 2014 09:26:05 -0500
On 25 Mar 2014, at 12:48 AM, Appa Rao Mulpuri <email@hidden> wrote:
All of this depends on your being able to produce the exception at least once. I agree that this is easier said than done.
> Exception type is:
>
> ERROR 2014-03-22 08:21:59 +0530 An uncaught exception occured
> Name: NSUncaughtSystemExceptionException
> Reason: Uncaught system exception: signal 11
Have you set an exception breakpoint? (Seventh inspector tab, cmd-7, click the + button at the bottom and select Add Exception Breakpoint. You’d probably be well-served to right-click on the new exception to get the breakpoint editor, and restrict it to Objective-C exceptions.)
>>
>>> 4 libsystem_c.dylib 0x00007fff8770394a _sigtramp +
>>> 26
>>> 5 ??? 0x0000000000000000 0x0 + 0
>>> 6 AppKit 0x00007fff8d3ed7b7 -[NSControl
>>> sendAction:to:] + 85
>>
>> Since the exception is triggered by a control sending its action, the
>> problem is likely that the object that¹s the target of the control got
>> deallocated.
>
> Agreed, Since this exception is getting rarely. Do we have any provision
> to extend the stack trace to print in which method the object is getting
> deallocated in our class?
You might learn something from Instruments: Add the Allocations instrument to your trace document, click the (i) button, and check “Record reference counts” and “Enable NSZombie detection.” Click the (x) button, and hope you can reproduce the crash.
If a message to a zombified object gets trapped, note the address, display the allocation history in the detail (bottom) area, and put the address in the search field. You should be able to see where any objects with that address were allocated, and the retain/release history. Open the Extended Detail view (View control in the toolbar, third segment); you’ll be shown a stack trace for any event you click on.
That does assume the zombified object gets messaged before this exception.
(I am delighted/dismayed to find that “zombified” is apparently in the Apple spelling dictionary.)
— F
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