Re: Increasing your app's stack size
Re: Increasing your app's stack size
- Subject: Re: Increasing your app's stack size
- From: Jim Ingham <email@hidden>
- Date: Wed, 19 Sep 2007 15:13:35 -0700
MarkW is right. The exception code for an EXC_BAD_ACCESS is the
address you were trying to access. So here you're dying because you
tried to access 0x0 which is in the "guard region" that's set to be
unreadable & unwritable specifically to catch null pointer accesses...
Usually if it's a stack overflow, you will get an EXC_BAD_ACCESS but
the address will be much higher - something with non-zero in the
eighth hex place.
You probably are accessing a NULL pointer.
Try rerunning the program and then look at the disassembly around
where you crash. The crashing address will most likely come from
accessing an address stored in some register. So, for instance on x86
in Jack's example, the crashing instruction is:
0x00001fb4 <something+10>: mov êx,(%esp)
Here the code is trying to write something to an address stored in the
stack pointer - %esp is the stack pointer. So you can tell that it's
the stack pointer that's gone bad. But if the faulting instruction is
one of the eax, ebx registers, then most likely that's some pointer
value that is invalid.
Jim
On Sep 19, 2007, at 2:27 PM, Mark Wagner wrote:
On 9/19/07, Mark Thomas <email@hidden> wrote:
Hi Mike,
I completely agree with your statement how-ever in this case I
cannot do
much about this, as most of the stack is OS Frameworks, not my
code :-(.
But looking at this technote it should possible ? - but at the
minute this
is a hunch, it there a way to tell from a crash log it's this issue.
Exception Type: EXC_BAD_ACCESS (SIGBUS)
Exception Codes: KERN_PROTECTION_FAILURE at 0x0000000000000000
Crashed Thread: 0
Thread 0 Crashed:
0 com.apple.CoreFoundation 0x93235834
CFURLCopyAbsoluteURL + 80
..
...
175 com.bt.220v 0x00007cb0 start + 56
I'm not an expert at reading crash logs, but that looks like
something's dereferencing a null pointer to me.
--
Mark
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