Re: Weird Crash in
Re: Weird Crash in
- Subject: Re: Weird Crash in
- From: Greg Parker <email@hidden>
- Date: Fri, 17 Jun 2011 15:51:42 -0700
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.
--
Greg Parker email@hidden Runtime Wrangler
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