Re: [PATCH 02/11] gdb: introduce intrusive_list, make thread_info use it

[Pedro Alves <pedro@palves.net>]

On 2021-07-06 8:38 p.m., Simon Marchi wrote:
> On 2021-07-05 11:44 a.m., Pedro Alves wrote:
>>>>  $1 = intrusive list of thread_info = {
>>    {id = 1.1, ptid = 1000.1000.0, state = THREAD_RUNNING}, 
>>    {id = 1.3, ptid = 1000.1002.0, state = THREAD_STOPPED},
>>    {id = 1.5, ptid = 1000.3672.0, state = THREAD_STOPPED}
>>  }
> 
> How would you accomplish this, with a struct thread_info
> pretty-printer?  This means that printing a single thread like this:
> 
>   (gdb) print *tp
> 
> would also produce the short output, I don't think we want that.  When
> we print a single thread_info structure, I think it's good to have all
> the fields shown.

I don't have a great answer.  It feels to me like the pretty printer code
should ask the container if it has a custom printer for the element, and only
if it doesn't would it look up the printer for the element's type.

Maybe having a printer for thread_info all the time isn't that bad.  printing
thread_info structures does dump a lot of stuff and isn't that easy to parse.
If you want to see the whole thing, there's always "print /r" to disable the
printer.

> 
> Perhaps by defining a more specialized pretty-printer for
> intrusive_list<thread_info>?  But then I'm not sure what kind of value
> the children method would return.

I guess it could return a typedef for "thread_info *" like e.g., "thread_info_p" instead
of the raw pointer, and then we'd register a printer for only the typedef.  I
think that means that indexing via thread_list[1] etc. would also return the typedef,
and thus give you the short print..