A question about gdb script

A question about gdb script

[Hui Zhu]

Hi guys,

I got a trouble in line:
 /* Make sure there is at least one LWP that has been resumed.  */
 gdb_assert (iterate_over_lwps (ptid, resumed_callback, NULL));

I set a breakpoint in the begin of this function and add commands:
silent
record
c
to it.

And set a bp in the end of this function and add commands:
silent
record stop
c
to it.

And I set a bp in internal_error.

Then I found the bug.

But I found that still have 2 ways not very easy to implement. I know
nothing about it.  could you help me with it?

1. If I want get the gdb_record.xxx file of each record cycle.  It's
still hard to me.  Because if I add "record save" to commands, each
time it will save record entry to same file.
Does gdb have some way to handle it? like:
$a=1
record save $a
$a++

2.  Sometime, I want just record a function, I want:
b functon_name
commands
silent
record
finish
#Maybe we can record save in this line, this is first question.
record stop
end
But when I really do it.  I found that gdb stop running after finish.

Could you help me with them?


Thanks,
Hui

Re: A question about gdb script

[Daniel Jacobowitz]

On Wed, Nov 25, 2009 at 04:42:54PM +0800, Hui Zhu wrote:
> 1. If I want get the gdb_record.xxx file of each record cycle.  It's
> still hard to me.  Because if I add "record save" to commands, each
> time it will save record entry to same file.
> Does gdb have some way to handle it? like:
> $a=1
> record save $a
> $a++

Not directly, but you can do this using Python scripting.

> 2.  Sometime, I want just record a function, I want:
> b functon_name
> commands
> silent
> record
> finish
> #Maybe we can record save in this line, this is first question.
> record stop
> end
> But when I really do it.  I found that gdb stop running after finish.
> 
> Could you help me with them?

This is a known limitation of breakpoint commands.  It's very
difficult.

-- 
Daniel Jacobowitz
CodeSourcery

Re: A question about gdb script

[Pedro Alves]

On Wednesday 25 November 2009 15:11:51, Daniel Jacobowitz wrote:
> > 2.  Sometime, I want just record a function, I want:
> > b functon_name
> > commands
> > silent
> > record
> > finish
> > #Maybe we can record save in this line, this is first question.
> > record stop
> > end
> > But when I really do it.  I found that gdb stop running after finish.
> > 
> > Could you help me with them?
> 
> This is a known limitation of breakpoint commands.  It's very
> difficult.

Try using the hook-stop instead.  Something like this:

 set $stop_recording_on_next_stop=0

 b functon_name
  commands
  silent
  record
  set $stop_recording_on_next_stop=1
  finish
  end

 define hook-stop
   if $stop_recording_on_next_stop 
     set $stop_recording_on_next_stop=0
     record save
     record stop
     end
   end

-- 
Pedro Alves

Re: A question about gdb script

[Hui Zhu]

On Thu, Nov 26, 2009 at 00:06, Pedro Alves <pedro@codesourcery.com> wrote:
> On Wednesday 25 November 2009 15:11:51, Daniel Jacobowitz wrote:
>> > 2.  Sometime, I want just record a function, I want:
>> > b functon_name
>> > commands
>> > silent
>> > record
>> > finish
>> > #Maybe we can record save in this line, this is first question.
>> > record stop
>> > end
>> > But when I really do it.  I found that gdb stop running after finish.
>> >
>> > Could you help me with them?
>>
>> This is a known limitation of breakpoint commands.  It's very
>> difficult.
>
> Try using the hook-stop instead.  Something like this:
>
>  set $stop_recording_on_next_stop=0
>
>  b functon_name
>  commands
>  silent
>  record
>  set $stop_recording_on_next_stop=1
>  finish
>  end
>
>  define hook-stop
>   if $stop_recording_on_next_stop
>     set $stop_recording_on_next_stop=0
>     record save
>     record stop
>     end
>   end
>

Cool.  I change hook-stop to:
define hook-stop
   if $stop_recording_on_next_stop
     set $stop_recording_on_next_stop=0
     record save
     record stop
    c
     end
   end

It looks not bad, but got a lot of:
---Type <return> to continue, or q <return> to quit---q

If you don't mind, I will post a patch to change each fprintf_filtered
in record.c to fprintf_unfiltered.

Thanks,
Hui

RE: A question about gdb script

[Marc Khouzam]

 

> -----Original Message-----
> From: gdb-owner@sourceware.org 
> [mailto:gdb-owner@sourceware.org] On Behalf Of Hui Zhu
> Sent: November-26-09 9:30 AM
> To: Pedro Alves; Daniel Jacobowitz; Michael Snyder
> Cc: gdb@sourceware.org
> Subject: Re: A question about gdb script
> 
> On Thu, Nov 26, 2009 at 00:06, Pedro Alves 
> <pedro@codesourcery.com> wrote:
> > On Wednesday 25 November 2009 15:11:51, Daniel Jacobowitz wrote:
> >> > 2.  Sometime, I want just record a function, I want:
> >> > b functon_name
> >> > commands
> >> > silent
> >> > record
> >> > finish
> >> > #Maybe we can record save in this line, this is first question.
> >> > record stop
> >> > end
> >> > But when I really do it.  I found that gdb stop running 
> after finish.
> >> >
> >> > Could you help me with them?
> >>
> >> This is a known limitation of breakpoint commands.  It's very
> >> difficult.
> >
> > Try using the hook-stop instead.  Something like this:
> >
> >  set $stop_recording_on_next_stop=0
> >
> >  b functon_name
> >  commands
> >  silent
> >  record
> >  set $stop_recording_on_next_stop=1
> >  finish
> >  end
> >
> >  define hook-stop
> >   if $stop_recording_on_next_stop
> >     set $stop_recording_on_next_stop=0
> >     record save
> >     record stop
> >     end
> >   end
> >
> 
> Cool.  I change hook-stop to:
> define hook-stop
>    if $stop_recording_on_next_stop
>      set $stop_recording_on_next_stop=0
>      record save
>      record stop
>     c
>      end
>    end
> 
> It looks not bad, but got a lot of:
> ---Type <return> to continue, or q <return> to quit---q

I think the command
set pagination off
will prevent this.

> If you don't mind, I will post a patch to change each fprintf_filtered
> in record.c to fprintf_unfiltered.
> 
> Thanks,
> Hui
> 

Re: A question about gdb script

[Michael Snyder]

Hui Zhu wrote:

> It looks not bad, but got a lot of:
> ---Type <return> to continue, or q <return> to quit---q

That can be fixed by saying "set height 0".

> If you don't mind, I will post a patch to change each fprintf_filtered
> in record.c to fprintf_unfiltered.

No, I don't agree with that.  If you do that, then user has
no choice about pagination.  "Set height" gives user a choice.

Re: A question about gdb script

[Hui Zhu]

Cool.

What I did is:
set $stop_recording_on_next_stop=0
set height 0

b functon_name
commands
record
set $stop_recording_on_next_stop=1
finish
end

define hook-stop
if $stop_recording_on_next_stop
set $stop_recording_on_next_stop=0
record save
record stop
c
end
end

It works very well.  When we done the record name issue, I will post it to wiki.

Thanks everyone.  :)

Hui

On Fri, Nov 27, 2009 at 02:24, Michael Snyder <msnyder@vmware.com> wrote:
> Hui Zhu wrote:
>
>> It looks not bad, but got a lot of:
>> ---Type <return> to continue, or q <return> to quit---q
>
> That can be fixed by saying "set height 0".
>
>> If you don't mind, I will post a patch to change each fprintf_filtered
>> in record.c to fprintf_unfiltered.
>
> No, I don't agree with that.  If you do that, then user has
> no choice about pagination.  "Set height" gives user a choice.
>
>

Re: A question about gdb script

[Michael Snyder]

Hui Zhu wrote:

> 1. If I want get the gdb_record.xxx file of each record cycle.  It's
> still hard to me.  Because if I add "record save" to commands, each
> time it will save record entry to same file.
> Does gdb have some way to handle it? like:
> $a=1
> record save $a
> $a++

If you look at cmd_record_save, you see it has (char *args).
GDB will pass "$a" as "args", so at that point you have the
opportunity to say, eg. "if (args[0] == '$') then do something".

One possibility would be to create your default name, eg.
gdb_record.12345, and then append $a making gdb_record.12345.1

That's the quick and dirty way.  Something more elegant might
be better.

> 2.  Sometime, I want just record a function, I want:
> b functon_name
> commands
> silent
> record
> finish
> #Maybe we can record save in this line, this is first question.
> record stop
> end
> But when I really do it.  I found that gdb stop running after finish.

That is unfortunately a long-standing gdb "limitation" (I mean ,
known bug).  It is so old that it is not likely to be fixed soon.

Re: A question about gdb script

[Hui Zhu]

On Thu, Nov 26, 2009 at 03:15, Michael Snyder <msnyder@vmware.com> wrote:
> Hui Zhu wrote:
>
>> 1. If I want get the gdb_record.xxx file of each record cycle.  It's
>> still hard to me.  Because if I add "record save" to commands, each
>> time it will save record entry to same file.
>> Does gdb have some way to handle it? like:
>> $a=1
>> record save $a
>> $a++
>
> If you look at cmd_record_save, you see it has (char *args).
> GDB will pass "$a" as "args", so at that point you have the
> opportunity to say, eg. "if (args[0] == '$') then do something".
>
> One possibility would be to create your default name, eg.
> gdb_record.12345, and then append $a making gdb_record.12345.1
>
> That's the quick and dirty way.  Something more elegant might
> be better.

I try this way but got:
(gdb) set $record = 3
(gdb) record save core.$record
Saved core file core.$record with execution log.

Maybe I can post a patch for it. What about following:
(gdb) set record not_overwrite_save on
(gdb) record save core
Saved core file core with execution log.
(gdb) record save core
Saved core file core.0 with execution log.
(gdb) record save core
Saved core file core.1 with execution log.

Thanks,
Hui

>
>> 2.  Sometime, I want just record a function, I want:
>> b functon_name
>> commands
>> silent
>> record
>> finish
>> #Maybe we can record save in this line, this is first question.
>> record stop
>> end
>> But when I really do it.  I found that gdb stop running after finish.
>
> That is unfortunately a long-standing gdb "limitation" (I mean ,
> known bug).  It is so old that it is not likely to be fixed soon.
>

Re: A question about gdb script

[Michael Snyder]

Hui Zhu wrote:
> On Thu, Nov 26, 2009 at 03:15, Michael Snyder <msnyder@vmware.com> wrote:
>> Hui Zhu wrote:
>>
>>> 1. If I want get the gdb_record.xxx file of each record cycle.  It's
>>> still hard to me.  Because if I add "record save" to commands, each
>>> time it will save record entry to same file.
>>> Does gdb have some way to handle it? like:
>>> $a=1
>>> record save $a
>>> $a++
>> If you look at cmd_record_save, you see it has (char *args).
>> GDB will pass "$a" as "args", so at that point you have the
>> opportunity to say, eg. "if (args[0] == '$') then do something".
>>
>> One possibility would be to create your default name, eg.
>> gdb_record.12345, and then append $a making gdb_record.12345.1
>>
>> That's the quick and dirty way.  Something more elegant might
>> be better.
> 
> I try this way but got:
> (gdb) set $record = 3
> (gdb) record save core.$record
> Saved core file core.$record with execution log.

No, what I meant was
   (gdb) set $foo = 3
   (gdb) record save $foo

That way you can look at the *first character* of "args", and
use an 'if' to do something special with it, such as

   char *filename = strcat("gdb_record.core", args);

> Maybe I can post a patch for it. What about following:
> (gdb) set record not_overwrite_save on
> (gdb) record save core
> Saved core file core with execution log.
> (gdb) record save core
> Saved core file core.0 with execution log.
> (gdb) record save core
> Saved core file core.1 with execution log.

That's also a possibility, although I think we are headed
in the direction of having too many mode variables associated
with process rec.