Re: [RFA] Patch to fix reverse-debug recursion function tail bug

Hui Zhu
2009-05-06T07:24:35Z

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Hi Michael,

Like the prev patch I send to you, this issue still affect cvs-head
and the patch can fix it.
Please help me review it.

The attachment is the new patch follow cvs-head.

2009-05-06 Hui Zhu <teawater@gmail.com>

* infrun.c (handle_inferior_event): Check frame_id when
check range in reverse debug mode.

Thanks,
Hui

On Sat, Mar 21, 2009 at 16:52, Hui Zhu <teawater@gmail.com> wrote:
> Hi,
>
> This patch is for bug report by Marc in
> http://sourceware.org/ml/gdb/2009-03/msg00127.html.
>
> This bug in "handle_inferior_event" deal with recursion function tail
> in reverse debug.
> infrun: infwait_normal_state
> infrun: TARGET_WAITKIND_STOPPED
> infrun: stop_pc = 0x8048457
> infrun: stepping inside range [0x8048457-0x804845a]
> infrun: stop_stepping
> factorial (x=4) at b.cc:5
>
> Inferior already step into another frame. But because this is a
> recursion function call, And 0x8048457 is in
> ecs->event_thread->step_range_start and
> ecs->event_thread->step_range_start.
>
> So gdb run in:
>
> if (stop_pc >= ecs->event_thread->step_range_start
>      && stop_pc < ecs->event_thread->step_range_end)
>    {
>
> This code is in front of:
>  if (!frame_id_eq (get_frame_id (get_current_frame ()),
>                    ecs->event_thread->step_frame_id)
>      && (frame_id_eq (frame_unwind_id (get_current_frame ()),
>                       ecs->event_thread->step_frame_id)
>          || execution_direction == EXEC_REVERSE))
>
> So gdb check range without check frame_id.
>
> So I make a patch to check frame_id when check range in reverse debug mode.
>
> 2008-03-21  Hui Zhu  <teawater@gmail.com>
>
>        * infrun.c (handle_inferior_event): Check frame_id when
>        check range in reverse debug mode.
>
>
>
>
>
> Actually, there is another thing, when gdb begin reverse-debug, it's range is:
>  8048439:       8b 45 08                mov    0x8(%ebp),%eax
>  804843c:       83 e8 01                sub    $0x1,%eax
>  804843f:       89 04 24                mov    %eax,(%esp)
>  8048442:       e8 dd ff ff ff          call   8048424 <_Z9factoriali>
>  8048447:       0f af 45 08             imul   0x8(%ebp),%eax
>  804844b:       89 45 fc                mov    %eax,-0x4(%ebp)
> Why is changed to infrun: stepping inside range [0x8048457-0x804845a]?
> That is because when inferior step at:
>  8048458:       c3                      ret
> In this address, $ebp is same with high level function and this
> function is factorial too.
> So the gdb can't found inferior step into another frame.  It will run to:
>  ecs->event_thread->step_range_start = stop_pc_sal.pc;
>  ecs->event_thread->step_range_end = stop_pc_sal.end;
>  ecs->event_thread->step_frame_id = get_frame_id (get_current_frame ());
>  ecs->event_thread->current_line = stop_pc_sal.line;
>  ecs->event_thread->current_symtab = stop_pc_sal.symtab;
>
>  if (debug_infrun)
>     fprintf_unfiltered (gdb_stdlog, "infrun: keep going\n");
>  keep_going (ecs);
> }
> So ecs->event_thread->step_range_start and ecs->event_thread->step_range_end.
>
> I don't find that it affect the reverse debug or something.  So I didn't fix it.
>
>
>
>
> Thanks,
> Hui
>

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---
infrun.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

--- a/infrun.c
+++ b/infrun.c
@@ -3421,7 +3421,10 @@ infrun: BPSTAT_WHAT_SET_LONGJMP_RESUME (
beyond the step range, and NOT the address of the last instruction
within it! */
if (stop_pc >= ecs->event_thread->step_range_start
- && stop_pc < ecs->event_thread->step_range_end)
+ && stop_pc < ecs->event_thread->step_range_end
+ && (frame_id_eq (get_frame_id (get_current_frame ()),
+ ecs->event_thread->step_frame_id)
+ || execution_direction != EXEC_REVERSE))
{
if (debug_infrun)
fprintf_unfiltered (gdb_stdlog, "infrun: stepping inside range [0x%s-0x%s]\n",