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

Hui Zhu
2009-05-11T07:07:26Z

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
>>
>