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From: garyj@frt.dec.com
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To: Fred Condo <fred@lightside.net>
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In-Reply-To: Message from Fred Condo <fred@lightside.net>  of Thu, 17 Oct 96 
 18:08:34 PDT.
Reply-To: gjennejohn@frt.dec.com
Subject: Re: gdb can't access address 
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Date: Fri, 18 Oct 96 13:12:05 +0200
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fred@lightside.net writes:
> I've been trying to help track down the SEGV bug in Apache. To that end,
> I've tried to backtrace the core dump using gdb. When I do that, I can get
> a backtrace without symbols, but it can't do it with the symbols turned on.
> Here's an example:
> 
> Core was generated by `httpd-g'.
> Program terminated with signal 6, Abort trap.
> #0  0x8091ee5 in ?? ()
> (gdb) bt
> #0  0x8091ee5 in ?? ()
> #1  0x3e88 in ?? ()
> #2  0xefbfe13c in ?? ()
> #3  0xc7a9 in ?? ()
> #4  0xcb99 in ?? ()
> #5  0x4941 in ?? ()
> #6  0x4b2d in ?? ()
> #7  0x5127 in ?? ()
> #8  0x5419 in ?? ()
> #9  0x10d3 in ?? ()
> (gdb) file httpd-g
> Reading symbols from httpd-g...done.
> (gdb) bt
> #0  0x8091ee5 in end ()
> Cannot access memory at address 0x366c0.
> 
> After loading the symbols, it can only show me the innermost stack frame :(
> 
> Any suggestions would be appreciated. This is under FBSD 2.1.0R and
> whatever gcc comes with that (2.6.3, I think).
> 
> 

I assume that httpd-g was compiled with -g ?

gdb can't resolve the shared libraries from a core dump since they aren't
mapped. Unless the libraries were also compiled with -g you won't get
very meaningful info when gdb hits a library routine, of course.

Try doing the following:

gdb httpd-g
b main
run <-- should load & map the shared libs
core-file httpd-g.core

after that you should be able to get a stack trace. This used to work.

---
Gary Jennejohn				(work) gjennejohn@frt.dec.com
					(home) Gary.Jennejohn@munich.netsurf.de
					(play) gj@freebsd.org