Feature suggestion: location conditioned watchpoint

Feature suggestion: location conditioned watchpoint

[Etienne Buira via Gdb]

Hi all,

I tried to debug memory corruption issue with gdb, using watchpoints,
and as the bug appeared rarely, i wish i could state "break on this
memloc write, if it is not this known good location".

I searched the docs for conditions and convenience variables, but could
not find anything useful.

Ideally, i would like to issue a command like:
condition WPNUM !(location path/to/myfile.c:42)

If there is already a way to do this, i'd like to hear about it, or
please consider it as feature suggestion.

Unfortunately, the bug did not show up when ran under gdb supervision,
even after enabling memory space randomisation, but that's another
topic.

Regards.

Re: Feature suggestion: location conditioned watchpoint

[Martin Simmons]

>>>>> On Sat, 19 Oct 2024 09:35:40 +0200, Etienne Buira via Gdb said:
> 
> I tried to debug memory corruption issue with gdb, using watchpoints,
> and as the bug appeared rarely, i wish i could state "break on this
> memloc write, if it is not this known good location".
> 
> I searched the docs for conditions and convenience variables, but could
> not find anything useful.
> 
> Ideally, i would like to issue a command like:
> condition WPNUM !(location path/to/myfile.c:42)
> 
> If there is already a way to do this, i'd like to hear about it, or
> please consider it as feature suggestion.

You could use a condition like:

$pc != <some_address>

where <some_address> is the address of the instruction that changes the
location.

__Martin

Re: Feature suggestion: location conditioned watchpoint

[Etienne Buira via Gdb]

On Sat, Oct 19, 2024 at 02:19:08PM +0100, Martin Simmons wrote:
> >>>>> On Sat, 19 Oct 2024 09:35:40 +0200, Etienne Buira via Gdb said:
> > 
> > I tried to debug memory corruption issue with gdb, using watchpoints,
> > and as the bug appeared rarely, i wish i could state "break on this
> > memloc write, if it is not this known good location".
> > 
> > I searched the docs for conditions and convenience variables, but could
> > not find anything useful.
> > 
> > Ideally, i would like to issue a command like:
> > condition WPNUM !(location path/to/myfile.c:42)
> > 
> > If there is already a way to do this, i'd like to hear about it, or
> > please consider it as feature suggestion.
> 
> You could use a condition like:
> 
> $pc != <some_address>
> 
> where <some_address> is the address of the instruction that changes the
> location.
> 
> __Martin

Hi Martin, thank you, sorry to have missed such an obvious way.

Regards.