[MI] Synchronous event notification

[Keith Seitz <keiths@redhat.com>]

Hi,

I've been working on integrating Apple's "-interpreter-exec" changes, and
I wanted to see if I could get some sort of consensus on how event
notifications should be defined.

In the trunk right now, MI ignores event notifications. Adding a mechanism
is vital to the success of MI.

Apple has added this, and all event notifications are tacked onto the
mi-command result:

  (gdb)
  -interpreter-exec console "break main"
  Breakpoint 1 at ...
  ^done,MI_HOOK_RESULT=[HOOK_TYPE="breakpoint_create",bkpt={number="1",...}]

Right now, this is done by defining a bunch of (existing) hooks when mi
runs. I presume that we want to switch over to using gdb-events, hoping
one day to deprecate the hooks, but that's not really the issue (since
they behave essentially the same in non-asynch). The real question is, how
do maintainers want this information communicated to mi clients?

The example above shows that Apple has added a syntax like:

  result ==>
     stuff [ "," event-list ]
  event-list ==>
     "MI_HOOK_RESULT=[" event ( "," event )* "]"
  event ==>
     "HOOK_TYPE=" event-name [ event-data ]
  event-name ==>
     "breakpoint_create" | "breakpoint_delete" | ...

and such.

Since hooks are really just event notifications, I would like to propose
that we use a definition like the above, but changing the string literals
a litte:

  event-list ==>
    "events=[" event ( "," event )* "]"
  event ==>
    "name=" event-name [ event-data ]
  event-name ==>
    "breakpoint_create" | "breakpoint_delete" | ...

Please discuss.
Keith