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

Hui Zhu
2009-06-09T02:18:56Z

PING

On Mon, May 11, 2009 at 15:07, Hui Zhu<teawater@gmail.com> wrote:
> PING
>
> On Wed, May 6, 2009 at 15:23, Hui Zhu <teawater@gmail.com> wrote:
>> 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
>>>
>>
>