[inferior events] cleanups in evpy_emit_event

[Tom Tromey <tromey@redhat.com>]

Sami --

This patch cleans up evpy_emit_event:

* It isn't ok to call error here
* Now we check all Python operations
* Now we call gdbpy_print_stack on error.  This seems correct since
  we don't actually want errors here to propagate -- just to be printed
  if the user asked for that
* Now objects are properly deallocated

I needed this while debugging an event listener of mine.

Ok to push?

Tom

@@ -137,15 +145,31 @@ evpy_emit_event (event_object *event)
      a notification.  */
   callback_list_copy = copy_py_list (callback_list);
   if (!callback_list_copy)
-    error(_("Cannot copy callback list."));
-
-  args_tuple = PyTuple_New ((Py_ssize_t) 1);
-  PyTuple_SetItem (args_tuple, (Py_ssize_t) 0, (PyObject *) event);
+    goto fail;
 
   for (i = 0; i < PyList_Size (callback_list_copy); i++)
     {
-      PyObject_CallObject (PyList_GET_ITEM (callback_list_copy, i), args_tuple);
+      PyObject *func = PyList_GetItem (callback_list_copy, i);
+
+      if (func == NULL)
+	goto fail;
+
+      if (!PyObject_CallFunctionObjArgs (func, event_obj, NULL))
+	{
+	  /* Print the trace here, but keep going -- we want to try to
+	     call all of the callbacks even if one is broken.  */
+	  gdbpy_print_stack ();
+	}
     }
+
+  Py_XDECREF (callback_list_copy);
+  Py_XDECREF (event_obj);
+  return;
+
+ fail:
+  gdbpy_print_stack ();
+  Py_XDECREF (callback_list_copy);
+  Py_XDECREF (event_obj);
 }
 
 static PyGetSetDef event_object_getset[] =