Re: [RFA/PATCH] breakpoint.c: fix until command

Elena Zannoni
2003-01-02T20:01:23Z

Michael Snyder writes:
> Daniel Jacobowitz wrote:
> >
> > On Mon, Dec 23, 2002 at 03:53:22PM -0800, Michael Snyder wrote:
> > > Elena Zannoni wrote:
> > > >
> > > > This fixes the problem reported in:
> > > > http://sources.redhat.com/ml/gdb/2002-11/msg00144.html
> > > >
> > > > testsuite patch coming
> > >
> > > Elena, can you sum up in a sentence or two, what this change
> > > is intended to do?
> >
> > [Since I happen to be reading email right now, I'll do a sketchy
> > imitation.]
> >
> > The problem is that we were marking the breakpoint on the
> > user-specified line with the current frame. But when we hit that
> > breakpoint, if it's in a different function, it will have a different
> > frame. Right now we see that the frames don't match and resume
> > executing.
> >
> > Oops.
>
> OK, thanks. But we _need_ to mark the breakpoint with the current
> frame, because if the breakpoint is in the current frame, we don't
> want to stop in an inner recursive call, ie. not until the current
> frame hits the breakpoint.
>

You mean this:

(gdb) l
91 #else
92 int factorial (value)
93 int value;
94 #endif
95 {
96 if (value > 1) {
97 value *= factorial (value - 1);
98 }
99 return (value);
100 }
(gdb) until 99

where should we stop? At the same invocation of factorial from which
we issued the until, or the next time line 99 is executed, i.e. the
next inner invocation of factorial? I would find the latter more
intuitive. To do what you want one could use 'break 99' and 'ignore n'.

(gdb) b factorial
Breakpoint 2 at 0x80485d7: file /home/ezannoni/sources/src/gdb/testsuite/gdb.base/break.c, line 96.
(gdb) r
The program being debugged has been started already.
Start it from the beginning? (y or n) y

Starting program: /home/ezannoni/sources/native/gdb/testsuite/gdb.base/break

Breakpoint 2, factorial (value=6)
at /home/ezannoni/sources/src/gdb/testsuite/gdb.base/break.c:96
96 if (value > 1) {
(gdb) delete
Delete all breakpoints? (y or n) y
(gdb) b 99

Breakpoint 3 at 0x80485f8: file /home/ezannoni/sources/src/gdb/testsuite/gdb.base/break.c, line 99.
(gdb) ignore 3 5
Will ignore next 5 crossings of breakpoint 3.
(gdb) c
Continuing.

Breakpoint 3, factorial (value=720)
at /home/ezannoni/sources/src/gdb/testsuite/gdb.base/break.c:99
99 return (value);

And here you are at the outermost invocation of factorial:

(gdb) n
100 }
(gdb)
720
main (argc=1, argv=0xbffff374, envp=0xbffff37c)
at /home/ezannoni/sources/src/gdb/testsuite/gdb.base/break.c:81
81 marker1 ();

Elena

> So this needs further consideration, and I don't think it can
> be approved as is.
>
> Michael
>
> > >
> > > > 2002-12-20 Elena Zannoni <ezannoni@redhat.com>
> > > >
> > > > Fix PR breakpoints/898.
> > > > * breakpoint.c (until_break_command): Don't use selected_frame,
> > > > but the null frame.
> > > >
> > > > Index: breakpoint.c
> > > > ===================================================================
> > > > RCS file: /cvs/uberbaum/gdb/breakpoint.c,v
> > > > retrieving revision 1.104
> > > > diff -u -p -r1.104 breakpoint.c
> > > > --- breakpoint.c 17 Dec 2002 17:27:44 -0000 1.104
> > > > +++ breakpoint.c 20 Dec 2002 18:06:27 -0000
> > > > @@ -5615,9 +5615,7 @@ until_break_command (char *arg, int from
> > > >
> > > > resolve_sal_pc (&sal);
> > > >
> > > > - breakpoint =
> > > > - set_momentary_breakpoint (sal,get_frame_id (deprecated_selected_frame),
> > > > - bp_until);
> > > > + breakpoint = set_momentary_breakpoint (sal, null_frame_id, bp_until);
> > > >
> > > > if (!event_loop_p || !target_can_async_p ())
> > > > old_chain = make_cleanup_delete_breakpoint (breakpoint);
> > >
> >
> > --
> > Daniel Jacobowitz
> > MontaVista Software Debian GNU/Linux Developer