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Re: Strange behaviour?

From Kaz Kylheku <kaz@kylheku.com>
Newsgroups comp.lang.c
Subject Re: Strange behaviour?
Date 2011-11-16 19:12 +0000
Organization A noiseless patient Spider
Message-ID <20111116111038.130@kylheku.com> (permalink)
References <ae447417-7ce0-420a-84be-620f6cbedf7d@p2g2000vbj.googlegroups.com> <haGdnexi_tbTYF7TnZ2dnUVZ_sqdnZ2d@bestweb.net>

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On 2011-11-16, Kenneth Brody <kenbrody@spamcop.net> wrote:
> I would recommend going back to the compile flags in which the bug was 
> visible.  Run that in the debugger again, and at the point that rmid is 
> about to "magically" change, check the values of N, rredge, rmid, and rrj. 
> You will probably see that redge+rmid-rj exceeds N-2, or is less than zero.

With optimization, looking at variables is not reliable under the GNU toolchain
(gcc + gdb). GDB does not know, in general, where a variable lives at any
point in the code: is its current home in the backing memory location or
in a register?  You have to disassemble the code, or add some printf calls and
hope that it still reproduces the same way.

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Thread

Strange behaviour? dmjcunha <dmjcunha@gmail.com> - 2011-11-15 11:31 -0800
  Re: Strange behaviour? James Kuyper <jameskuyper@verizon.net> - 2011-11-15 14:43 -0500
  Re: Strange behaviour? Seebs <usenet-nospam@seebs.net> - 2011-11-15 19:26 +0000
    Re: Strange behaviour? dmjcunha <dmjcunha@gmail.com> - 2011-11-15 13:15 -0800
      Re: Strange behaviour? Keith Thompson <kst-u@mib.org> - 2011-11-15 14:33 -0800
      Re: Strange behaviour? Willem <willem@toad.stack.nl> - 2011-11-15 22:35 +0000
        Re: Strange behaviour? dmjcunha <dmjcunha@gmail.com> - 2011-11-16 03:37 -0800
          Re: Strange behaviour? Willem <willem@toad.stack.nl> - 2011-11-16 13:34 +0000
          Re: Strange behaviour? Nick Keighley <nick_keighley_nospam@hotmail.com> - 2011-11-16 06:07 -0800
  Re: Strange behaviour? Kenneth Brody <kenbrody@spamcop.net> - 2011-11-16 13:13 -0500
    Re: Strange behaviour? Kaz Kylheku <kaz@kylheku.com> - 2011-11-16 19:12 +0000
      Re: Strange behaviour? dmjcunha <dmjcunha@gmail.com> - 2011-11-16 13:14 -0800
        Re: Strange behaviour? Seebs <usenet-nospam@seebs.net> - 2011-11-16 22:18 +0000

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