question about -file-exec-and-symbols gdbmi command

question about -file-exec-and-symbols gdbmi command

[Dodji Seketeli]

Hello folks,

I am using  gdb with the mi2 interpreter.

I do -file-exec-and-symbols <prog-1>, set a couple of
breakpoints, do a bit of debugging a bit etc.

Then I do a -file-exec-and-symbols <prog-2> .
At this point, gdb tries to set the breakpoint I have set previously,
while debugging <prog-1>. Of course, that attempt fails. Is this
behavious normal ? I would have thought that gdb should clear the
current breakpoints when -file-exec-and-symbols is run on a new exec
file.

Also, is there an irc channel (or jabber room) where the gdb developers
can be reached ? This is typically the case of small stuff some people
(like me) would love sending a patch for. And having the developpers at
hand to ask some questions quickly like -  "where is function to look at
to clear the breakpoints ?" where the function called by
"-file-exec-and-symbols to actually do the work ?" - would help a lot
to increase the mindshare of GDB internals.


Cheers,



-- 
Dodji Seketeli
http://www.seketeli.org/dodji

Re: question about -file-exec-and-symbols gdbmi command

[Nick Roberts]

 > I am using  gdb with the mi2 interpreter.
 > 
 > I do -file-exec-and-symbols <prog-1>, set a couple of
 > breakpoints, do a bit of debugging a bit etc.
 > 
 > Then I do a -file-exec-and-symbols <prog-2> .
 > At this point, gdb tries to set the breakpoint I have set previously,
 > while debugging <prog-1>. Of course, that attempt fails. Is this
 > behavious normal ? I would have thought that gdb should clear the
 > current breakpoints when -file-exec-and-symbols is run on a new exec
 > file.

-file-exec-and-symbols is really just the `file' command:

In mi-cmds.c:

  { "file-exec-and-symbols", { "file", 1 }, NULL, NULL },

so it's not restricted to MI.

I don't really use either but maybe it would be inconvenient to have all
the breakpoints cleared, if you wanted to switch to another version of the
same program, say.  It's easier to delete then all manually, just with `delete'
than it is to add them back again.

Perhaps it could be a GDB option.

-- 
Nick                                           http://www.inet.net.nz/~nickrob

Re: question about -file-exec-and-symbols gdbmi command

[Dodji Seketeli]

On Wed, 18 Apr 2007 21:58:49 +1200
Nick Roberts <nickrob@snap.net.nz> wrote:

[...]

> -file-exec-and-symbols is really just the `file' command:
> 
> In mi-cmds.c:
> 
>   { "file-exec-and-symbols", { "file", 1 }, NULL, NULL },
> 
> so it's not restricted to MI.
> 
> I don't really use either but maybe it would be inconvenient to have
> all the breakpoints cleared, if you wanted to switch to another
> version of the same program, say.  It's easier to delete then all
> manually, just with `delete' than it is to add them back again.
> 
> Perhaps it could be a GDB option.

Okay thank you for the hints, Nick.

I maybe I could try a patch that introduces a new command that clears
all the breakpoints when you load a new file ?

Cheers,


-- 
Dodji Seketeli
http://www.seketeli.org/dodji

Re: question about -file-exec-and-symbols gdbmi command

[Nick Roberts]

 > > Perhaps it could be a GDB option.
 > 
 > Okay thank you for the hints, Nick.
 > 
 > I maybe I could try a patch that introduces a new command that clears
 > all the breakpoints when you load a new file ?

I was thinking modifying the GDB environment with the set command, e.g.,

set breakpoint auto-clear on/off

I think a new command would make behaviour hard to toggle, with a front end
say.

I can't approve your patches, so don't do anything yet.  Wait for Daniel
Jacobowitz, for example, to give his opinion.

-- 
Nick                                           http://www.inet.net.nz/~nickrob

Re: question about -file-exec-and-symbols gdbmi command

[Daniel Jacobowitz]

On Wed, Apr 18, 2007 at 10:36:37PM +1200, Nick Roberts wrote:
>  > > Perhaps it could be a GDB option.
>  > 
>  > Okay thank you for the hints, Nick.
>  > 
>  > I maybe I could try a patch that introduces a new command that clears
>  > all the breakpoints when you load a new file ?
> 
> I was thinking modifying the GDB environment with the set command, e.g.,
> 
> set breakpoint auto-clear on/off
> 
> I think a new command would make behaviour hard to toggle, with a front end
> say.
> 
> I can't approve your patches, so don't do anything yet.  Wait for Daniel
> Jacobowitz, for example, to give his opinion.

I don't see the point.  If you want to delete breakpoints when you
load a new file, why not just do so?  It's easy with -break-list and
-break-delete.

It shouldn't happen automatically.  For instance, one use of
-file-exec-and-symbols is to tell GDB that the file has been recompiled.

-- 
Daniel Jacobowitz
CodeSourcery

Re: question about -file-exec-and-symbols gdbmi command

[Nick Roberts]

 > >  > I maybe I could try a patch that introduces a new command that clears
 > >  > all the breakpoints when you load a new file ?
 > > 
 > > I was thinking modifying the GDB environment with the set command, e.g.,
 > > 
 > > set breakpoint auto-clear on/off
 > > 
 > > I think a new command would make behaviour hard to toggle, with a front end
 > > say.
 > > 
 > > I can't approve your patches, so don't do anything yet.  Wait for Daniel
 > > Jacobowitz, for example, to give his opinion.
 > 
 > I don't see the point.  If you want to delete breakpoints when you
 > load a new file, why not just do so?  It's easy with -break-list and
 > -break-delete.

I'm thinking that if you load a new program into a front end, there's no need
to restart GDB, and the user might be surprised to see his old breakpoints are
still there.  I don't have DDD or Insight to hand to see what they do.

 > It shouldn't happen automatically.  For instance, one use of
 > -file-exec-and-symbols is to tell GDB that the file has been recompiled.

That's independent of the breakpoint issue, isn't it?

-- 
Nick                                           http://www.inet.net.nz/~nickrob

Re: question about -file-exec-and-symbols gdbmi command

[Daniel Jacobowitz]

On Wed, Apr 18, 2007 at 11:59:47PM +1200, Nick Roberts wrote:
>  > I don't see the point.  If you want to delete breakpoints when you
>  > load a new file, why not just do so?  It's easy with -break-list and
>  > -break-delete.
> 
> I'm thinking that if you load a new program into a front end, there's no need
> to restart GDB, and the user might be surprised to see his old breakpoints are
> still there.  I don't have DDD or Insight to hand to see what they do.
> 
>  > It shouldn't happen automatically.  For instance, one use of
>  > -file-exec-and-symbols is to tell GDB that the file has been recompiled.
> 
> That's independent of the breakpoint issue, isn't it?

Nope.  The difference is that the front end has some knowledge of
"this is a new program" versus "this is the same program being
reloaded", because it issued the command in response to some user
stimulus.  GDB has no way to know why the command was issued; in one
case deleting breakpoints is appropriate, in the other it is not.

So if the front end wants breakpoints deleted, I think it's reasonable
for it to do so explicitly.

-- 
Daniel Jacobowitz
CodeSourcery

Re: question about -file-exec-and-symbols gdbmi command

[Dodji Seketeli]

On Wed, 18 Apr 2007 08:11:37 -0400
Daniel Jacobowitz <drow@false.org> wrote:

> Nope.  The difference is that the front end has some knowledge of
> "this is a new program" versus "this is the same program being
> reloaded", because it issued the command in response to some user
> stimulus.  GDB has no way to know why the command was issued; in one
> case deleting breakpoints is appropriate, in the other it is not.
> 
> So if the front end wants breakpoints deleted, I think it's reasonable
> for it to do so explicitly.

Indeed. I noticed this whilst writing a front end, actually. I got
hard time fuguring why I was seeing breakpoints from another binary
being returned by -break-list :-)

I understand your point and felt back on what you suggest.

Thank you for that.

So, there is no IRC channel where you guys can be reached ? :-)

Cheers,


-- 
Dodji Seketeli
http://www.seketeli.org/dodji

Re: question about -file-exec-and-symbols gdbmi command

[Daniel Jacobowitz]

On Wed, Apr 18, 2007 at 03:06:15PM +0200, Dodji Seketeli wrote:
> So, there is no IRC channel where you guys can be reached ? :-)

No, generally there isn't.

-- 
Daniel Jacobowitz
CodeSourcery

Re: question about -file-exec-and-symbols gdbmi command

[Nick Roberts]

 > >  > It shouldn't happen automatically.  For instance, one use of
 > >  > -file-exec-and-symbols is to tell GDB that the file has been
 > >  > recompiled.
 > > 
 > > That's independent of the breakpoint issue, isn't it?
 > 
 > Nope.  The difference is that the front end has some knowledge of
 > "this is a new program" versus "this is the same program being
 > reloaded", because it issued the command in response to some user
 > stimulus.  GDB has no way to know why the command was issued; in one
 > case deleting breakpoints is appropriate, in the other it is not.
 > 
 > So if the front end wants breakpoints deleted, I think it's reasonable
 > for it to do so explicitly.

In Emacs at least, GDB command can be entered through the GUD buffer, just like
they are on the command line, so I don't see how it would know the user's
purpose any more than GDB does.  Anyway, I have no need of this functionality
at the moment.  I'll raise it again when, or if, I need it later



-- 
Nick                                           http://www.inet.net.nz/~nickrob