[json-glib/wip/ordered-iter] Assert that foreach_member() won't mutate the object

[Emmanuele Bassi <ebassi src gnome org>]

commit 9d31efb712ab43035163d46e34d020f0febb7e02
Author: Emmanuele Bassi <ebassi gnome org>
Date:   Mon Aug 24 12:42:58 2020 +0100

    Assert that foreach_member() won't mutate the object
    
    We document that it's not safe, but we kind of rely on GHashTable to do
    that for us. Instead, let's use the newly added age field to protect
    against accidental mutations during iteration, just like we do for the
    iterator API.

 json-glib/json-object.c | 5 +++++
 1 file changed, 5 insertions(+)
---
diff --git a/json-glib/json-object.c b/json-glib/json-object.c
index a17fd6d..8555eb9 100644
--- a/json-glib/json-object.c
+++ b/json-glib/json-object.c
@@ -968,16 +968,21 @@ json_object_foreach_member (JsonObject        *object,
                             gpointer           data)
 {
   GList *l;
+  int age;
 
   g_return_if_fail (object != NULL);
   g_return_if_fail (func != NULL);
 
+  age = object->age;
+
   for (l = object->members_ordered.head; l != NULL; l = l->next)
     {
       const gchar *member_name = l->data;
       JsonNode *member_node = g_hash_table_lookup (object->members, member_name);
 
       func (object, member_name, member_node, data);
+
+      g_assert (object->age == age);
     }
 }