Re: Isolating a bug?

FROM : Ondra Cada
DATE : Wed Apr 06 13:41:06 2005

On 6.4.2005, at 12:46, Gregory Weston wrote:

> Exception:  EXC_BAD_ACCESS (0x0001)
> Codes:      KERN_PROTECTION_FAILURE (0x0002) at 0x00000006
>
> Thread 0 Crashed:
> 0  com.apple.CoreFoundation     0x901939cc CFHash + 0x18
> 1  com.apple.CoreFoundation     0x90192d28 __CFDictionaryFindBuckets1b +
> 0x70
> 2  com.apple.CoreFoundation     0x90192184 CFDictionaryGetValue + 0xec
> 3  com.apple.CoreFoundation     0x901b0fb0
> _CFApplicationPreferencesCreateValueForKey + 0x6c
> 4  com.apple.Foundation         0x909fb38c -[NSUserDefaults
> objectForKey:] + 0x98
> 5  my.program.signature         0x00008658 -[MyApplication
> methodTakingAString:] + 0x5c
>
> The routine identified in line 5 is called repeatedly (although not
> rapidly) while the program is running - it had been invoked hundreds
> of times without error during this session. The argument to
> objectForKey: at line 4 is a freshly-created from
> NSString>>stringWithFormat:. I'm not sure where to start looking for
> the cause of a problem that manifests five invocations into external
> code. Advice?


For starters, log the "freshly-created from NSString>>stringWithFormat"
just before the objectForKey: gets called. There is still a chance it
gets something messed up somehow...

If that does not help, I kind of fear the problem *may* be elsewhere,
in an uninitialized pointer or somrthing alike, whose result are
mangled in-memory data. That's a bug alas very difficult to find, and
assembly-level debugging might be needed. Well, hopefully, the cause
would be something more trivial :)
---
Ondra Èada
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