how to create and hardware watchpoint from a commands list.

[Doug Evans]

On Sun, Feb 8, 2015 at 6:49 AM, Julien Chavanton <jchavanton@gmail.com> wrote:
> Hi Doug, thank you for trying to help, I spent a few hours on this so
> I am interested to solve this puzzle for next time.
>
> ----------------------------
> By doing it manually I mean,
>
> step-1) I type :
>
> printf "0x%x\n", &call->stream->session->ext.settings.mode
>
> and then :
>
> step-2) I type :
> watch *(int *){result from step 1}
>
> -------------------------------
> This did not work for me :
>
> watch -location call->stream->session->ext.settings.mode
> -------------------------------

Without more details it's hard to help.
Can you provide a cut-n-paste of the gdb session that shows the problem?


>
> I can rerun the session and provide exact output or I could just try
> an alternative "piping" the output of step-1 to step-2 from the GDB
> "command line interpreter" not sure how it is called, this as to be
> executed from a breakpoint command list ?
>
>
> On Sun, Feb 8, 2015 at 5:26 AM, Doug Evans <xdje42@gmail.com> wrote:
>> On Wed, Feb 4, 2015 at 2:14 AM, Julien Chavanton <jchavanton@gmail.com> wrote:
>>> Hi Folks, I would like to create and hardware watchpoint from a commands list.
>>>
>>> retrieve the addres of a variable and create a watch.
>>>
>>> watch *(int *) &call->stream->session->ext.settings.mode
>>>
>>> Manualy this is working fine, but I do not know the right syntax in GDB.
>>
>> What do you mean by this working manually but then not knowing the right syntax?
>>
>>>
>>> I tried "watch -location call->stream->session->ext.settings.mode"
>>>
>>> And sereval other things, is there a way to pipe the output of one
>>> command to another one ?
>>
>> You tried several things, but you need to be more specific about
>> what problems you had.  Complete unedited session logs are useful.
>>
>> There are various ways to "pipe" (for lack of a better term) the
>> output of previous commands into subsequent commands.
>> value history, convenience variables and/or eval or python come to mind.
>> But do you need to?
>> What about "watch -location ..." didn't work?
>>
>>>
>>> watch *(int *) | printf "0x%x\n", &call->stream->session->ext.settings.mode
>>>
>>>
>>> ----------------------------------------------------------
>>>
>>>
>>> define myhook
>>>   echo myhook \n
>>>   next
>>>   next
>>>   next
>>>   print call->stream->session->ext.settings.mode
>>>   print &call->stream->session->ext.settings.mode
>>>   printf "watch *(int *)0x%x\n", &call->stream->session->ext.settings.mode
>>> end
>>>
>>> break set_settings
>>> commands
>>>  myhook
>>> end