Re: [PATCH] Add "thread-group id" and "id in thread-group" info to -thread-info output

[Pedro Alves <palves at redhat dot com>]

On 03/15/2017 09:36 PM, Simon Marchi wrote:
> On 2017-02-24 15:22, Simon Marchi wrote:
>> While writing the documentation parts, these question popped to mind:
>>
>> - The type of the id-in-tg field (a string) assumes that a thread
>> belongs to a single group.  Currently, the only kind of "thread-group"
>> we have is inferiors.  The thread-group terminology suggests that in
>> the future we might have other kinds of thread groups, like
>> user-defined arbitrary groups.  Otherwise, why would MI use "thread
>> group" instead of "inferior"?  Because of this, do you think that the
>> type of the field will be limiting?  For example, should we document
>> right that this field can be a list, when a thread is part of multiple
>> groups, for example?
>>
>> - The format of the id-in-tg field is "1" for inferior/thread-group 1.
>>  In -list-thread-groups, the id is shown as "i1".  Again, if there are
>> other kinds of groups later, we can assume that we'll need to
>> differentiate the type, so just "1" won't work.  For this reason and
>> for consistency with the result of -list-thread-groups, should we show
>> "i1" here as well?
> 
> I thought about this a bit more, and I wonder if the solution is not to
> just use "inferior" here.
> 
> In MI, so far, the wording "thread-group" was used instead of inferior. 
> An inferior is one kind (and the only one at the moment) of
> thread-group.  Using "thread-group" instead of "inferior" allows to have
> new kinds of thread-groups in the future, and still have commands that
> make sense (e.g. -list-thread-groups, or the --thread-group switch).
> 
> However, in this case, the information we want to convey is specifically
> about inferiors, it will never be about other kinds of thread groups (if
> some ever exist).  Since a thread always has exactly one parent inferior
> and exactly one id in this inferior, we don't have the single value vs
> list problem.  So I think it would make sense to use "id-in-inf" or
> instead of "id-in-tg" and "inf-num"/"inf-id" instead of "tg-id".
> 
> And I think that also takes care of the format issue, "1" vs "i1".  "i1"
> is the thread-group id.  It is necessary to have the i in case other
> kinds of thread groups appear.  But if the field is "inf-num" or
> "inf-id", then we no longer have the include the i.
> 
> Thoughts?

Makes sense to me.

Thanks,
Pedro Alves