[Lldb-commits] [PATCH] Improvement for lldb-gdb-remote.txt qHostInfo documentation

[Matthew Gardiner]

Hi Jason,

Indeed my stub implementation does not rely on the hex/otherwise 
encoding of the triple. I'm happy to revert the patch and change the 
implementation in the GDBRemote code (probably not till next week, 
though). My main regret is not floating my patch on lldb-dev first, but 
I assumed that the implementation was set in stone at that stage.

While we are at it, I also note that distribution_id, os_build, 
hostname, os_kernel are also currently hex encoded in qHostInfo 
response, so I'm now curious as to the encoding rationale to those datas 
too...

Matt


Jason Molenda wrote:
> Hi Matthew,
>
> If your stub implementation is not locked into hex encoding this triple string, let's change the lldb / stub implementation and the documentation.  It's a mistake and I'd hate to propagate it further.  Yeah, the - and + characters are used for ACK / NACK when a packet consists only of that character but normal packets are bounded by # and $ so we don't need to worry about + and -.  (plus lldb prefers to go into "no-ack" mode as soon as possible anyway :)  We've already got a ton of randomness in the remote protocol because of bugs which get deployed and we need to support them forever.
>
> Thanks!
>
> On Jul 24, 2014, at 10:22 PM, Matthew Gardiner <mg11 at csr.com> wrote:
>
>> Hi Jason,
>>
>> Having the triple hex encoded did confuse me for a while in getting my architecture's stub up and working properly, when the previous documentation suggested a plain textual representation.
>>
>> The comment in GDBRemoteCommunicationClient .cpp "// The triple comes as ASCII hex bytes since it contains '-' chars" got me thinking, and I discovered that '-' is used as the *first* byte in a packet to specify a NACK (in section E.11 Packet Acknowledgement of the GDB documentation).
>>
>> I agree that the need to escape the '-' is probably unfounded since in the case of qHostInfo the '-' is wedged between $ and # characters anyway.
>>
>> I'm happy to proceed with either presentation - so long as the documentation is correct.
>>
>> Matt
>>
>>
>> Jason Molenda wrote:
>>> The change to make the documentation match the implementation is fine.
>>>
>>> But I don't see why the triple is sent hex encoded.  The comment & hex encoding was added in r128193 from March 23 2011 by Greg Clayton.  AFAIK '-' is not special in gdb-remote protocol.  Characters that can be a problem are $, #, *, }.
>>>
>>> Greg?
>>>
>>> J
>>>
>>>
>>>> On Jul 23, 2014, at 6:23 AM, Matthew Gardiner <mg11 at csr.com> wrote:
>>>>
>>>> Folks,
>>>>
>>>> When I first implemented the qHostInfo for the kalimba gdbserver stub, I sent the triple string as kalimba-csr-unknown. However the receiving code (GDBRemoteCommunicationClient) expects the string to be encoded as hex bytes, since '-' are a reserved GDB-RSP control character.
>>>>
>>>> The documentation for qHostInfo in lldb-gdb-remote.txt does not allude to this at all. So I'm sending this patch which I think improves this state of affairs.
>>>>
>>>> Could someone please apply this patch?
>>>>
>>>> thanks Matt
>>>>
>>>>
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