Re: [PATCH] Replace deprecated_target_wait_hook by an observer

[Patrick Monnerat <patrick@monnerat.net>]

On 8/24/21 6:14 PM, Andrew Burgess wrote:
> * Patrick Monnerat via Gdb-patches <gdb-patches@sourceware.org> [2021-08-22 18:42:56 +0200]:
>
>> +DEFINE_OBSERVABLE (waiting_for_target);
> Given we already have events 'target_changed' and 'target_resumed', I
> wonder if it would be more consistent to name this event 'target_wait'?
>
Yes, it's possible. Here are the two reasons why I did not name this 
observer 'target_wait':

1) Because the observer is not supposed to wait by itself, I fear it 
will be a source of confusion.

2) As a good old C programmer, I still have some reluctance naming an 
object as a global procedure. Not being declared in the same namespace 
though!

Comments are welcome!

>>   
>> -  return target->wait (ptid, status, options);
>> +  gdb::observers::waiting_for_target.notify (true, ptid);
>> +  event_ptid = target->wait (ptid, status, options);
>> +  gdb::observers::waiting_for_target.notify (false, event_ptid);
>> +  return event_ptid;
> I would be tempted to wrap this notification inside an RAII class,
> then we will be guaranteed to send the second notification, even in
> the event that the wait call exits via an exception.

That would make sense, but in case we have an exception, event_ptid is 
not known. How would you handle it? pass it as null_ptid?

Thanks for review,

Patrick