Help with debug

Phil Lodwick Phil.Lodwick at EFI.COM
Thu Mar 15 00:32:18 CDT 2007


I have been debugging a problem today and am running low on batteries.  I am
hoping somebody can look at the attached snippet of log and point me in the
right direction.

>From what I can tell, there is a DLL called snoopy.dll that does a whole
bunch of allocs and reallocs and then tries to reference a NULL pointer which
causes an unhandled exception.  The code goes through a loop and does not
always crash on the same iteration, but it always seems to crash at the same

This code does not crash on Windows.  Just getting lucky?

Unfortunately I do not have the sources to this code, so it makes life a
little more difficult.  

Any good ideas for my next step in debugging?

-------------- next part --------------

000e:Call ntdll.RtlAllocateHeap(41210000,00000000,00000030) ret=7c3416b3
000e:trace:heap:RtlAllocateHeap (0x41210000,00000002,00000030): returning 0x46927938
000e:Ret  ntdll.RtlAllocateHeap() retval=46927938 ret=7c3416b3
000e:Call ntdll.RtlReAllocateHeap(41210000,00000000,4692a240,00000238) ret=7c3527e9
000e:trace:heap:RtlReAllocateHeap (0x41210000,00000002,0x4692a240,00000238): returning 0x46927970
000e:Ret  ntdll.RtlReAllocateHeap() retval=46927970 ret=7c3527e9
000e:trace:seh:__regs_RtlRaiseException code=c0000005 flags=0 addr=0x1133572a
000e:trace:seh:__regs_RtlRaiseException  info[0]=00000000
000e:trace:seh:__regs_RtlRaiseException  info[1]=00000000
000e:trace:seh:__regs_RtlRaiseException  eax=00000001 ebx=00000000 ecx=00000000 edx=00000000 esi=456b68b8 edi=46929d50
000e:trace:seh:__regs_RtlRaiseException  ebp=456b6880 esp=456b6598 cs=0073 ds=007b es=007b fs=003b gs=0033 flags=00010246
000e:Call ntdll.RtlEnterCriticalSection(4148f460) ret=41440765
000e:Ret  ntdll.RtlEnterCriticalSection() retval=00000000 ret=41440765
000e:Call ntdll.RtlLeaveCriticalSection(4148f460) ret=414407a6
000e:Ret  ntdll.RtlLeaveCriticalSection() retval=00000000 ret=414407a6
000e:trace:seh:EXC_CallHandler calling handler at 0x113f6cae code=c0000005 flags=0


Unhandled exception: page fault on read access to 0x00000000 in 32-bit code (0x1133572a).

=>1 0x1133572a in snoopy (+0x18572a) (0x456b6880)
  2 0x11337e52 in snoopy (+0x187e52) (0x00000000)

0x1133572a: movl   0x0(%ebx),%ecx

Module	Address			Debug info	Name (140 modules)
PE	0x111b0000-1149b000	Export          snoopy 

process  tid      prio (all id:s are in hex)
	00000016    0
	00000015    0
	00000014    0
	00000012    0
	00000010    0
	0000000f    0
	0000000e    0 <==
	0000000d    0
	0000000c    0
	0000000b    0
	0000000a    0
	00000009    0

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