Re: Weird Crash in
Re: Weird Crash in
- Subject: Re: Weird Crash in
- From: Laurent Daudelin <email@hidden>
- Date: Fri, 17 Jun 2011 16:28:34 -0700
On Jun 17, 2011, at 15:51, Greg Parker wrote:
> On Jun 17, 2011, at 3:48 PM, Laurent Daudelin wrote:
>
>> On Jun 17, 2011, at 15:22, Greg Parker wrote:
>>
>>> On Jun 17, 2011, at 2:40 PM, Laurent Daudelin wrote:
>>>> One of my user sent me a crash log with an excerpt here:
>>>>
>>>> ...
>>>> Exception Type: EXC_BAD_ACCESS (SIGSEGV)
>>>> Exception Codes: KERN_INVALID_ADDRESS at 0x0000000000000027
>>>> ...
>>>> Thread 4 Crashed: Dispatch queue: com.apple.root.default-priority
>>>> 0 libobjc.A.dylib 0x00007fff85ea115c objc_msgSend_vtable2 + 12
>>>> 1 com.apple.Foundation 0x00007fff827f79a5 -[NSCFString isEqualToString:] + 63
>>>> ...
>>>>
>>>> It's a part of my code that compares NSStrings. Of course, nobody besides him are able to reproduce this.
>>>>
>>>> My question: what could cause a crash in function 'objc_msgSend_vtable2'?
>>>
>>> Short answer: for any of the same reasons that cause a crash in objc_msgSend().
>>>
>>> The vtable versions of objc_msgSend() are specialized optimizations for a few of the most frequently-called methods. objc_msgSend_vtable2 is currently optimizing the -class method. Presumably one of the two string objects was invalid and -isEqualToString: was trying to check which class the bad object belonged to.
>>
>> Thanks for the speedy reply, Greg. What do you mean exactly by "invalid"? Bad pointers? Pointers on instances of different classes? Or both?
>
>
> Pointer to anything that is not a valid object. Merely being an instance of the wrong class would not cause that crash.
Thanks for that valuable information, Greg. At least I know where to look.
Cheers!
-Laurent.
--
Laurent Daudelin
AIM/iChat/Skype:LaurentDaudelin http://www.nemesys-soft.com/
Logiciels Nemesys Software email@hidden
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