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


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
>>
>


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