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

[Hui Zhu <teawater at gmail dot com>]

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
>

Attachment: fix-function-tail-stack-same.txt
Description: Text document