[RFC 2/2] gdb/mi: add new async events =target-connected and =target-disconnected

[Simon Marchi]

On 2018-10-14 8:55 a.m., Jan Vrany wrote:
> Whenever a target is connected or disconnected, emit new asynchronous
> event =target-connected and =target-disconnected. Events report
> both short name and full name of connected or disconnected target.
> In addition, =target-connected report a set of target features.
> 
> This allows frontends to keep track of current target and its features
> regardless whether target is changed explicitly by MI -target-select
> command, CLI target command or implicitly by  native target auto-connect.

Thanks, I like the idea.  A non-RFC version of this would require corresponding
tests to be accepted.

> @@ -1271,6 +1275,73 @@ mi_user_selected_context_changed (user_selected_what selection)
>      }
>  }
>  
> +static void
> +mi_target_connected (struct target_ops *target)
> +{
> +  SWITCH_THRU_ALL_UIS ()
> +    {
> +      struct mi_interp *mi = as_mi_interp (top_level_interpreter ());
> +      struct ui_out *mi_uiout;
> +
> +      if (mi == NULL)
> +        continue;
> +
> +      mi_uiout = top_level_interpreter ()->interp_ui_out ();
> +
> +      target_terminal::scoped_restore_terminal_state term_state;
> +      target_terminal::ours_for_output ();
> +
> +      fprintf_unfiltered (mi->event_channel,"target-connected");
> +
> +      mi_uiout->redirect (mi->event_channel);
> +
> +      mi_uiout->field_string ("type", target->shortname());
> +      mi_uiout->field_string ("name", target->longname());
> +
> +      {
> +        ui_out_emit_list list_emitter (mi_uiout, "features");
> +
> +        if (mi_async_p ())
> +          mi_uiout->field_string (NULL, "async");
> +        if (target_can_execute_reverse)
> +          mi_uiout->field_string (NULL, "reverse");
> +      }
> +
> +      mi_uiout->redirect (NULL);
> +
> +      gdb_flush (mi->event_channel);
> +    }
> +}

I think there is a (kind of corner-case, but still) bug with using
mi_async_p and target_can_execute_reverse.  Here are some CLI commands
I type in a "gdb -i mi", and the corresponding
=target-connected/disconnected event:

set mi-async on
file test
=target-connected,type="exec",name="Local exec file",features=[]

start
=target-connected,type="native",name="Native process",features=["async"]

record
=target-connected,type="record-full",name="Process record and replay target",features=["async","reverse"]

file
=target-disonnected,type="exec",name="Local exec file"

file /bin/ls
=target-connected,type="exec",name="Local exec file",features=["async","reverse"]

That last event says the exec target supports async and reverse, which is wrong.
So you would need to write an equivalent of mi_async_p/target_can_execute_reverse
to which you can pass a target_ops*, it should not be too hard.

Simon