Re: Question about core files

[Manish Katiyar <mkatiyar@gmail.com>]

On Fri, Oct 9, 2009 at 5:39 PM, Holger Kiehl <Holger.Kiehl@dwd.de> wrote:
> Hello Manish
>
> First, sorry for the late responce!
>
> On Wed, 7 Oct 2009, Manish Katiyar wrote:
>
>> On Wed, Oct 7, 2009 at 7:51 PM, Holger Kiehl <Holger.Kiehl@dwd.de> wrote:
>>>
>>> Hello Manish
>>>
>>> On Wed, 7 Oct 2009, Manish Katiyar wrote:
>>>
>>>> Hi Holger,
>>>>
>>>> I don't have the source code, so a bit hard to guess. But you can try
>>>> to find out which member of your fsa structure is at offset 236 (0xec)
>>>> and look around those lines in the function where you are accessing
>>>> that member.
>>>>
>>>> I am trying to download the AFD source code, which looks like it will
>>>> take ages on my slow broadband. Hopefully I can help after that.
>>>>
>>> If you download, please take afd-1.4.0-0.20.beta.tar.bz2 because that
>>> is the one that caused the error. You can get it from:
>>>
>>>   ftp://ftp.dwd.de/pub/afd/development/afd-1.4.0-0.20.beta.tar.bz2
>>>
>>> You will find the relevant code in src/fd.c.
>>
>> Hi Holger,
>>
>> (gdb) set $offset = (int)(&((struct filetransfer_status *)0)->host_status)
>> (gdb) p $offset
>> $5 = 236
>> (gdb) p/x 236
>> $6 = 0xec
>>
>> host_status is at offset 236. In the function start_process I can see
>> that this is used at places by dereferencing below
>> "fsa[fsa_pos].host_status ".
>>
>> At this point my guess would be that you are getting fsa_pos as
>> something illegal ie.. probably you are trying to access beyond the
>> array. Since this is an input to the function, you can just check its
>> value at the start and assert if that is ok and within reasonable
>> range.
>>
>> HTH
>>
> Many thanks for finding this out! I think I now, with your help, have a
> clue where the error could be. Is there a way to find out what value
> fsa_pos had at that time?

Since it is a runtime variable, probably we can get something by
looking at the output of "info registers". But you can try putting

if (fsa_pos <0 ) {
   printf("going to die ... \n");
   return
}

in the start of the function itself and try.

>  If it was -1 then it is definitely the error
> I am thinking of, but if it is something else then I don't know.
>
> Again many thanks for the valuable help!
>
> Regards,
> Holger



-- 
Thanks -
Manish
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