Xapian devel - Jun 2011 - xapian csharp bindings crash

We're running xapian on our windows web machine, and we're having
intermittent crashes from time to time, I've managed to capture two
DUMP-s of the processes on two different occasions. There was some
issue with a mismatched .pdb since I've compiled it a few times in
development since the production server was updated so I can't match
those.

However, in both cases the faulting module was _XapianSharp.dll, the
windows exception is c0000005 (Access violation), the following is
what I managed to get from windbg:

FAULTING_IP:
_XapianSharp!CSharp_TermGenerator_SetFlags__SWIG_1+f2ca5
000007fe`e3d8533e 8b440208        mov     eax,dword ptr [rdx+rax+8]

EXCEPTION_RECORD:  ffffffffffffffff -- (.exr 0xffffffffffffffff)
ExceptionAddress: 000007fee3d8533e
(_XapianSharp!CSharp_TermGenerator_SetFlags__SWIG_1+0x00000000000f2ca5)
   ExceptionCode: c0000005 (Access violation)
  ExceptionFlags: 00000000
NumberParameters: 2
   Parameter[0]: 0000000000000000
   Parameter[1]: 000000001dcb0058
Attempt to read from address 000000001dcb0058

PROCESS_NAME:  w3wp.exe

ERROR_CODE: (NTSTATUS) 0xc0000005 - The instruction at 0x%08lx
referenced memory at 0x%08lx. The memory could not be %s.

EXCEPTION_CODE: (NTSTATUS) 0xc0000005 - The instruction at 0x%08lx
referenced memory at 0x%08lx. The memory could not be %s.

EXCEPTION_PARAMETER1:  0000000000000000

EXCEPTION_PARAMETER2:  000000001dcb0058

READ_ADDRESS:  000000001dcb0058

FOLLOWUP_IP:
_XapianSharp!CSharp_TermGenerator_SetFlags__SWIG_1+f2ca5
000007fe`e3d8533e 8b440208        mov     eax,dword ptr [rdx+rax+8]

I still have the dump files I could upload if they'll help, I'll also
upload the latest compiled binaries to our production so that next
crash will have proper pdb-s. In any case it looks to be an issue with
pointer access in CSharp_TermGenerator_SetFlags__SWIG_1.

Any help would be much appreciated, thanks.

On Sat, Jun 25, 2011 at 05:37:09PM +0200, Greg wrote:
> FAULTING_IP:
> _XapianSharp!CSharp_TermGenerator_SetFlags__SWIG_1+f2ca5
> 000007fe`e3d8533e 8b440208        mov     eax,dword ptr [rdx+rax+8]
> 
> EXCEPTION_RECORD:  ffffffffffffffff -- (.exr 0xffffffffffffffff)
> ExceptionAddress: 000007fee3d8533e
> (_XapianSharp!CSharp_TermGenerator_SetFlags__SWIG_1+0x00000000000f2ca5)
>    ExceptionCode: c0000005 (Access violation)
>   ExceptionFlags: 00000000
> NumberParameters: 2
>    Parameter[0]: 0000000000000000
>    Parameter[1]: 000000001dcb0058
> Attempt to read from address 000000001dcb0058
What version of Xapian are you using here?

This sounds like Parameter[1] is the "this" pointer and Parameter[0]
is
the flags being set.  The other way round doesn't make sense, since the
C++ code doesn't try to read the flags as an address, and also that's
not a sensible flags value.

The generated C++ code there looks fine to me, at least in the latest
version.  So it looks like the pointer to the C++ object which the C#
object is holding is invalid.  I'm not sure how that might have happened
though.  Do you know if that's a plausible pointer value to a C++ heap
allocated object in your environment?
> I still have the dump files I could upload if they'll help, I'll
also
> upload the latest compiled binaries to our production so that next
> crash will have proper pdb-s. In any case it looks to be an issue with
> pointer access in CSharp_TermGenerator_SetFlags__SWIG_1.
The dump files wouldn't help me - perhaps somebody else would know
what to do with them though.

Cheers,
    Olly