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Date: Fri, 09 Nov 2001 09:40:00 -0000
To: gdb@sources.redhat.com
From: Pierre Muller <muller@cerbere.u-strasbg.fr>
Subject: Re: Bug with watchpoints on Linux
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At 13:01 21/11/2001 , vous avez écrit:

>   There seems to be a big problem with
>hardware watchpoints under Linux.
>
>   If I compile a simple program :
>
>/* START of twatch.c */
>static int x,y;
>int
>main ()
>{
>   x = 5;
>   y = x * 2;
>   x = y / 2;
>   x = 7;
>   return 0;
>}
>/* END of twatch.c */
>and set a hardware watchpoint on variable 'x',
>the debugger correctly stops at each program location where this global 
>var is changed.
>
>   But at the second run, the program is never stopped because
>of the changes to this global variable.
>
>   It seems like there is a problem with the hardware watchpoint
>resetting.
>
>   I tested this on only one Linux machine,
>but both the main and the 5.1 branches show this problem.
>
>
>   The current main CVS tree with a patch (not yet submitted)
>to add hardware watchpoints on cygwin target does not
>have this problem (It works but there are still some problems).

Whoops, I was too fast once again...

I do see the same problem in my cygwin implementation ...

>This makes me suspect that the problem is truely Linux specific.
>
>   Is this a known Linux problem of version 5.1 ?

   Is this a known problem for i386 hardware watches ?


Pierre Muller
Institut Charles Sadron
6,rue Boussingault
F 67083 STRASBOURG CEDEX (France)
mailto:muller@ics.u-strasbg.fr
Phone : (33)-3-88-41-40-07  Fax : (33)-3-88-41-40-99