gdb: add inferior parameter to architecture_changed observable

This is to make it explicit which inferior's architecture just changed,
and that the callbacks should not assume it is the current inferior.

Update the only caller, pyuw_on_new_gdbarch, to add the parameter,
although it doesn't use it currently.

Change-Id: Ieb7f21377e4252cc6e7b1ce2cc812cd1a1840e0e
Reviewed-By: John Baldwin <jhb@FreeBSD.org>
Approved-By: Andrew Burgess <aburgess@redhat.com>

gdb/arch-utils.c

@@ -1489,7 +1489,8 @@ set_target_gdbarch (struct gdbarch *new_gdbarch)
   gdb_assert (new_gdbarch != NULL);
   gdb_assert (new_gdbarch->initialized_p);
   current_inferior ()->set_arch (new_gdbarch);
-  gdb::observers::architecture_changed.notify (new_gdbarch);
+  gdb::observers::architecture_changed.notify (current_inferior (),
+					       new_gdbarch);
   registers_changed ();
 }
 

gdb/observable.h

@@ -153,9 +153,10 @@ extern observable<struct breakpoint */* b */> breakpoint_deleted;
    is the modified breakpoint.  */
 extern observable<struct breakpoint */* b */> breakpoint_modified;
 
-/* The current architecture has changed.  The argument NEWARCH is a
+/* INF's architecture has changed.  The argument NEWARCH is a
    pointer to the new architecture.  */
-extern observable<struct gdbarch */* newarch */> architecture_changed;
+extern observable<inferior */* inf */, struct gdbarch */* newarch */>
+  architecture_changed;
 
 /* The thread's ptid has changed.  The OLD_PTID parameter specifies
    the old value, and NEW_PTID specifies the new value.  */

gdb/python/py-unwind.c

@@ -945,7 +945,7 @@ static const registry<gdbarch>::key<pyuw_gdbarch_data_type> pyuw_gdbarch_data;
    intermediary.  */
 
 static void
-pyuw_on_new_gdbarch (struct gdbarch *newarch)
+pyuw_on_new_gdbarch (inferior *inf, gdbarch *newarch)
 {
   struct pyuw_gdbarch_data_type *data = pyuw_gdbarch_data.get (newarch);
   if (data == nullptr)