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Date:      Thu, 1 Mar 2001 19:58:17 +0200
From:      Peter Pentchev <roam@orbitel.bg>
To:        Peter Dufault <dufault@hda.hda.com>
Cc:        hackers@freebsd.org
Subject:   Re: Stupid debugging pthread question
Message-ID:  <20010301195817.G55211@ringworld.oblivion.bg>
In-Reply-To: <200103011745.f21Hjts33386@hda.hda.com>; from dufault@hda.hda.com on Thu, Mar 01, 2001 at 12:44:39PM -0500
References:  <200103011745.f21Hjts33386@hda.hda.com>

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On Thu, Mar 01, 2001 at 12:44:39PM -0500, Peter Dufault wrote:
> This is a stupid question, basically it's how to debug something.
> 
> I have four cooperating p-threaded processes.  One of them keeps getting
> a SIGSEGV with the address 0x752f422f.  I'm not sure if that address is
> always the same, but with a given compile it is.  The thing that's a pain
> is it is random.  The four processes can run for a long time, or through
> several tests to completion, and then the
> nasty process gets that SIGSEGV.  The thread that receives the SIGSEGV
> is random, the stack of the SEGV'd thread is trash, the rest of the
> threads in the offending process still have intact stacks.  Arg!
> 
> Because this is intermittent my temptation is to ignore it and proceed
> and eventually something will happen to let me figure it out.  But
> it's been going on for a while, and it just happened twice in a row so...
> Anybody seen anything remotely similar and have a suggestion?  How
> does one dump the stack brute force on an x86?

Not too much help, but..

0x752f422f sure looks like a hex representation of 4 ASCII chars,
and in the alnum range to boot; it's '/B/u', if I'm not too sleepy,
and considering the little-endian Intel architecture.

It sure looks like you have a (self-inflicted? :) buffer overflow
somewhere in your code.

G'luck,
Peter

-- 
This sentence claims to be an Epimenides paradox, but it is lying.

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