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Date: Fri, 09 Nov 2001 06:17:00 -0000
To: gdb@sources.redhat.com
From: Pierre Muller <muller@cerbere.u-strasbg.fr>
Subject: Bug with watchpoints on Linux
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   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).

This makes me suspect that the problem is truely Linux specific.

   Is this a known Linux problem of version 5.1 ?




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