breakpoints/2332: watchpoints silently don't work on Opteron

breakpoints/2332: watchpoints silently don't work on Opteron

[yuri]

>Number:         2332
>Category:       breakpoints
>Synopsis:       watchpoints silently don't work on Opteron
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    unassigned
>State:          open
>Class:          change-request
>Submitter-Id:   net
>Arrival-Date:   Thu Oct 11 19:18:01 UTC 2007
>Closed-Date:
>Last-Modified:
>Originator:     yuri@tsoft.com
>Release:        gdb-6.7
>Organization:
>Environment:

>Description:
I am trying to set watchpoint on my Opteron (see log below).
Though this value has been changed watchpoint didn't occur.

gdb should either catch watchpoint or tell the user that watchpoints don't work and why they don't work when user sets a watchpoint.

Otherwise it looks completely broken.



My OS is:
Linux jf031 2.4.21-37.ELsmp #1 SMP Wed Sep 7 13:32:18 EDT 2005 x86_64 unknown

gdb log is:
Starting program: /home/yuriv/sandbox-mainline-last/libserv/test/w

Breakpoint 1, main () at w.C:8
8         int i = 1;
(gdb) n
9         f(&i);
(gdb) p &i
$1 = (int *) 0x7fbfffeb0c
(gdb) watch 0x7fbfffeb0c
Watchpoint 2: 548682066700
(gdb) c
Continuing.

Program exited with code 02.
(gdb)
>How-To-Repeat:
void f(int *i) { *i = 2; }

main() {
  int i = 1;
  f(&i);
  return (i);
}
>Fix:
n/a
>Release-Note:
>Audit-Trail:
>Unformatted:

Re: breakpoints/2332: watchpoints silently don't work on Opteron

[Daniel Jacobowitz]

The following reply was made to PR breakpoints/2332; it has been noted by GNATS.

From: Daniel Jacobowitz <drow@false.org>
To: yuri@tsoft.com
Cc: gdb-gnats@sources.redhat.com
Subject: Re: breakpoints/2332: watchpoints silently don't work on Opteron
Date: Thu, 11 Oct 2007 15:22:58 -0400

 On Thu, Oct 11, 2007 at 07:14:19PM -0000, yuri@tsoft.com wrote:
 > I am trying to set watchpoint on my Opteron (see log below).
 > Though this value has been changed watchpoint didn't occur.
 > 
 > gdb should either catch watchpoint or tell the user that watchpoints don't work and why they don't work when user sets a watchpoint.
 > 
 > Otherwise it looks completely broken.
 
 They work fine for me on a comparable system with a newer kernel.
 
 > (gdb) p &i
 > $1 = (int *) 0x7fbfffeb0c
 > (gdb) watch 0x7fbfffeb0c
 > Watchpoint 2: 548682066700
 
 That is not doing what you think.  Try watch *(int *)0x7fbfffeb0c.
 The value "0x7fbfffeb0c" is not changing.
 
 -- 
 Daniel Jacobowitz
 CodeSourcery