From: Reuben Thomas <rrt@sc3d.org>
To: "Maciej W. Rozycki" <macro@wdc.com>
Cc: Christo Crause <christo.crause@gmail.com>,
Reuben Thomas via Gdb <gdb@sourceware.org>
Subject: Re: Remote protocol question: the documentation says '?' is not required, but maybe it is?
Date: Tue, 21 Jul 2020 21:24:00 +0100 [thread overview]
Message-ID: <CAOnWdoh2hTb3rMnby4eZhj+2U7+KhqwXxS_+Wy-UFvYnk6O0Tw@mail.gmail.com> (raw)
In-Reply-To: <alpine.LFD.2.21.2007212021180.24175@redsun52.ssa.fujisawa.hgst.com>
On Tue, 21 Jul 2020 at 20:34, Maciej W. Rozycki <macro@wdc.com> wrote:
> On Tue, 21 Jul 2020, Reuben Thomas wrote:
>
> > > FYI, I do believe `?' is indeed mandatory, as GDB needs to figure out
> the
> > > initial state of the remote target as it has connected to it, and
> there is
> > > no other way.
> >
> > It seems to be more complicated than that. In principle, '?' isn't needed
> > in principle to figure out the initial state: the T packet, or in my
> > current case, the S packet tells GDB the signal, and yet GDB still asks
> for
> > it again with '?'. The signal that caused the remote to halt is not going
> > to change until the next 'c', so there's no need for GDB to ask for it
> > again; and yet it does.
>
> I take you mean a `T' or `S' stop reply, right?
>
> Well, such replies are only expected by GDB in response to specific
> packets, which are all listed at the top of Section E.3 "Stop Reply
> Packets". If you issue an unsolicited stop reply from your debug stub,
> then at best GDB will ignore it and at worst GDB will get confused.
>
Sorry, I didn't explain this clearly enough before.
As you can see in section E.3, T is an allowed reply to the 'c' command.
As I explained in my previous message, the first packet that the debug stub
sends is discarded by gdb.
Therefore, the stub is only sending the T packet when it is allowed: the
first time, it is discarded, and every other time, it is in response to a
'c' command.
--
https://rrt.sc3d.org
next prev parent reply other threads:[~2020-07-21 20:24 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-19 19:08 Reuben Thomas
2020-07-21 10:22 ` Christo Crause
2020-07-21 10:29 ` Reuben Thomas
2020-07-21 11:33 ` Maciej W. Rozycki
2020-07-21 16:35 ` Christo Crause
2020-07-21 18:51 ` Reuben Thomas
2020-07-21 19:34 ` Maciej W. Rozycki
2020-07-21 20:24 ` Reuben Thomas [this message]
2020-07-21 20:26 ` Reuben Thomas
2020-07-21 20:48 ` Reuben Thomas
2020-07-21 21:19 ` Maciej W. Rozycki
2020-07-21 21:23 ` Reuben Thomas
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