Re: gdb, stderr, totally baffing experience!

[Paul E Johnson]

thanks. line 438 is the fprintf line.

Paul Box's suggestion that some class is running off the end of an array 
and damaging memory is a pretty good guess. I've been going through this 
code getting rid of C arrays and converting to Swarm lists and the seg 
fault has disappeared.

address@hidden wrote:
> Paul Johnson writes:
>  > Program received signal SIGSEGV, Segmentation fault.
>  > 0x420503da in vfprintf () from /lib/i686/libc.so.6
>  > (gdb) bt
>  > #0  0x420503da in vfprintf () from /lib/i686/libc.so.6
>  > #1  0x4205a297 in fprintf () from /lib/i686/libc.so.6
>  > #2  0x08050ff4 in _i_Agent__updateFamily (self=0x8b6d2d8, 
>  > _cmd=0x8058790) at Agent.m:438
>  > #3  0x08050907 in _i_Agent__step (self=0x8b6d2d8, _cmd=0x8056e00) at 
>  > Agent.m:256
>  > #4  0x40017ddb in L10 () from /usr/lib/swarm/libswarm.so.0
>  > #5  0x40205120 in objc_call (fa=0x8c36f10)
> [...]
>  > Is it possible that, when some part of a program accesses memory so 
>  > badly that it could damage memory in use by uniformIntRand in a way that 
>  > totally baffles the gdb?
>
> It's not necessarily true that gdb is baffled.  I suspect there
> is something in Agent::updateFamily() that is screwing up the 
> memory... dropping something that shouldn't be dropped, overwriting
> something... missing a null character at the end of a string...
> buffer overrun... etc. that is only being detected by the 
> vfprintf() function.  You're error is most likely at line 
> 438 in Agent.m.



--
Paul E. Johnson                       email: address@hidden
Dept. of Political Science            http://lark.cc.ku.edu/~pauljohn
1541 Lilac Lane, Rm 504
University of Kansas                  Office: (785) 864-9086
Lawrence, Kansas 66044-3177           FAX: (785) 864-5700


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