[lldb-dev] GDB RSP qVAttachOrWaitSupported

[jingham at apple.com]

On May 9, 2014, at 9:45 AM, Todd Fiala <tfiala at google.com> wrote:

> Oh right, good point.
> 
> All the remote sides I worked with essentially have a default incoming packet rule that says "if I don't know what this is, respond with $#00", so no need to add that explicitly if your remote side already does that, Matthew.

That's actually a requirement of the protocol (from E.1 Overview):

    For any command not supported by the stub, an empty response (‘$#00’) should be returned.

Jim


> 
> -Todd
> 
> 
> On Fri, May 9, 2014 at 9:27 AM, <jingham at apple.com> wrote:
> Note also as a general rule, you never need to add support for a query packet unless you support the thing it is querying for, since whoever is sending it is supposed to take the "unrecognized packet" error to mean not supported.
> 
> Jim
> 
> On May 9, 2014, at 9:26 AM, jingham at apple.com wrote:
> 
> > My bad, there are actually a bunch of vAttach variant packets we added to support attaching by process name, and "wait for a process to show up and then attach to it" and the like.
> >
> > I added documentation for them.
> >
> > Jim
> >
> > On May 9, 2014, at 8:57 AM, Todd Fiala <todd.fiala at gmail.com> wrote:
> >
> >> Hey Matthew,
> >>
> >> Essentially you'll want to return a string like this:
> >> $OK#9a
> >>
> >> if your gdb remote debug monitor can handle that (undocumented) element, or return this:
> >> $#00
> >>
> >> if you do not support the packet.
> >>
> >> I've been digging into the protocol lately since I'm adding tests for gdb remote protocol-layer activity, so that I can verify lldb-gdbserver (llgs) on Linux is acting identically to debugserver on MacOSX (and to make it easier for us to transition from debugserver to llgs).
> >>
> >> I had noted that packet wasn't documented a while back.  When I get to testing that one, I'll update the doc text file on it.
> >>
> >>
> >> On Fri, May 9, 2014 at 6:40 AM, Abid, Hafiz <Hafiz_Abid at mentor.com> wrote:
> >> I have not read the documentation for this packet. But looking at the code,
> >> It seems that you will return OK if your stub supports this packet. Otherwise an empty reply can
> >> Indicate that packet is not supported.
> >>
> >> Please look at the following link for more details about query packets.
> >> https://sourceware.org/gdb/onlinedocs/gdb/General-Query-Packets.html#General-Query-Packets
> >>
> >> Thanks,
> >> Abid
> >>
> >>> -----Original Message-----
> >>> From: Matthew Gardiner [mailto:mg11 at csr.com]
> >>> Sent: 09 May 2014 13:24
> >>> To: Abid, Hafiz; lldb-dev at cs.uiuc.edu
> >>> Subject: Re: [lldb-dev] GDB RSP qVAttachOrWaitSupported
> >>>
> >>> Abid, Hafiz wrote:
> >>>> RNBRemote::HandlePacket_qVAttachOrWaitSupported has the following
> >>> comments which may give you some idea.
> >>>>     // We support attachOrWait meaning attach if the process exists,
> >>> otherwise wait to attach.
> >>> Ok, thanks.
> >>>
> >>> So this whole entity "VAttachOrWaitSupported" is a concept which the stub
> >>> does or not support, correct?
> >>>
> >>> If so, does the stub write back "1", if it does support it, otherwise "0"?
> >>>
> >>> Presumably if the stub does support this feature, are there any other
> >>> messages which the stub should then support?
> >>>
> >>> I'm still not really clear what's happening here....
> >>>
> >>> Matt
> >>>
> >>>
> >>>
> >>> Member of the CSR plc group of companies. CSR plc registered in England
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> >>
> >>
> >> --
> >> -Todd
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> Todd Fiala |	 Software Engineer |	 tfiala at google.com |	 650-943-3180
>