Re: [PATCH 1/2] gdbserver, read_ptid: handle '0' and '-1' thread ids

[Simon Marchi <simark@simark.ca>]

On 8/13/25 11:36 PM, Thiago Jung Bauermann wrote:
> Hello Markus,
> 
> Markus Metzger <markus.t.metzger@intel.com> writes:
> 
>> The special thread id '-1' means 'all threads'.
>> The special thread id '0' means 'any thread'.
>>
>> Read_ptid () currently returns
>>
>>     <current pid>.-1.0
>>
>> and
>>
>>     <current pid>.0.0
>>
>> respectively.
>>
>> Change that to minus_one_ptid for '-1' and to null_ptid for '0'.

I can see that there are read_ptid functions both on GDB and
GDBserver-side.  We can see that they are similar, but they have
diverged a bit (and they will diverge even more with this patch).  IWBN
if possible to have just one shared implementation.  One part that
differs between the implementations is where we get the default pid
value.  That value would have to be passed in as a parameter.  The nice
side-effect of that is that it make it easy to unit test this function,
which we don't do right now.

>>
>> CC: Thiago Jung Bauermann  <thiago.bauermann@linaro.org>
>> ---
>>  gdbserver/remote-utils.cc | 20 ++++++++++++++++++++
>>  1 file changed, 20 insertions(+)
> 
> Nice improvement. Just a minor comment.
> 
>> diff --git a/gdbserver/remote-utils.cc b/gdbserver/remote-utils.cc
>> index 15f073dd6be..9562cc2e1fb 100644
>> --- a/gdbserver/remote-utils.cc
>> +++ b/gdbserver/remote-utils.cc
>> @@ -566,6 +566,26 @@ read_ptid (const char *buf, const char **obuf)
>>    const char *p = buf;
>>    const char *pp;
>>  
>> +  /* Handle special thread ids.  */
>> +  if (*p == '0')
> 
> I think this should also check the character after '0':

Agreed.  I think it would be valid to pass `0A`, to represent tid 10.

Can we instead let the code go through hex_or_minus_one below and handle
"tid == 0" there?

Simon