Bug 624473: GDBusSubtreeIntrospectFunc return type

Return a NULL terminated C array instead of a GPtrArray

Also, document that %NULL is a permitted return value and clarify its
meaning.

Finally, avoid calling the enumeration function during dispatch when the
G_DBUS_SUBTREE_FLAGS_DISPATCH_TO_UNENUMERATED_NODES flag was given.

gio/gdbusconnection.c

@@ -5167,7 +5167,7 @@ handle_subtree_introspect (GDBusConnection *connection,
   const gchar *sender;
   const gchar *requested_object_path;
   const gchar *requested_node;
-  GPtrArray *interfaces;
+  GDBusInterfaceInfo **interfaces;
   guint n;
   gchar **subnode_paths;
 
@@ -5209,18 +5209,14 @@ handle_subtree_introspect (GDBusConnection *connection,
                                        es->user_data);
   if (interfaces != NULL)
     {
-      if (interfaces->len > 0)
-        {
-          /* we're in business */
       introspect_append_standard_interfaces (s);
 
-          for (n = 0; n < interfaces->len; n++)
+      for (n = 0; interfaces[n] != NULL; n++)
         {
-              const GDBusInterfaceInfo *interface_info = interfaces->pdata[n];
+          g_dbus_interface_info_generate_xml (interfaces[n], 2, s);
-              g_dbus_interface_info_generate_xml (interface_info, 2, s);
+          g_dbus_interface_info_unref (interfaces[n]);
         }
-        }
+      g_free (interfaces);
-      g_ptr_array_unref (interfaces);
     }
 
   /* then include <node> entries from the Subtree for the root */
@@ -5265,12 +5261,11 @@ handle_subtree_method_invocation (GDBusConnection *connection,
   const gchar *requested_object_path;
   const gchar *requested_node;
   gboolean is_root;
-  gchar **children;
   const GDBusInterfaceInfo *interface_info;
   const GDBusInterfaceVTable *interface_vtable;
   gpointer interface_user_data;
   guint n;
-  GPtrArray *interfaces;
+  GDBusInterfaceInfo **interfaces;
   gboolean is_property_get;
   gboolean is_property_set;
   gboolean is_property_get_all;
@@ -5298,20 +5293,30 @@ handle_subtree_method_invocation (GDBusConnection *connection,
         is_property_get_all = TRUE;
     }
 
+  if (!is_root)
+    {
+      requested_node = strrchr (requested_object_path, '/') + 1;
+
+      if (~es->flags & G_DBUS_SUBTREE_FLAGS_DISPATCH_TO_UNENUMERATED_NODES)
+        {
+          /* We don't want to dispatch to unenumerated
+           * nodes, so ensure that the child exists.
+           */
+          gchar **children;
+          gboolean exists;
+
           children = es->vtable->enumerate (es->connection,
                                             sender,
                                             es->object_path,
                                             es->user_data);
 
-  if (!is_root)
+          exists = _g_strv_has_string ((const gchar * const *) children, requested_node);
-    {
+          g_strfreev (children);
-      requested_node = strrchr (requested_object_path, '/') + 1;
 
-      /* If not dynamic, skip if requested node is not part of children */
+          if (!exists)
-      if (!(es->flags & G_DBUS_SUBTREE_FLAGS_DISPATCH_TO_UNENUMERATED_NODES) &&
-          !_g_strv_has_string ((const gchar * const *) children, requested_node))
             goto out;
         }
+    }
   else
     {
       requested_node = "/";
@@ -5323,13 +5328,15 @@ handle_subtree_method_invocation (GDBusConnection *connection,
                                        requested_object_path,
                                        requested_node,
                                        es->user_data);
-  g_assert (interfaces != NULL);
+
+  if (interfaces == NULL)
+    goto out;
+
   interface_info = NULL;
-  for (n = 0; n < interfaces->len; n++)
+  for (n = 0; interfaces[n] != NULL; n++)
     {
-      const GDBusInterfaceInfo *id_n = (const GDBusInterfaceInfo *) interfaces->pdata[n];
+      if (g_strcmp0 (interfaces[n]->name, interface_name) == 0)
-      if (g_strcmp0 (id_n->name, interface_name) == 0)
+        interface_info = interfaces[n];
-        interface_info = id_n;
     }
 
   /* dispatch the call if the user wants to handle it */
@@ -5371,11 +5378,10 @@ handle_subtree_method_invocation (GDBusConnection *connection,
         g_assert_not_reached ();
 
       /* see if the object supports this interface at all */
-      for (n = 0; n < interfaces->len; n++)
+      for (n = 0; interfaces[n] != NULL; n++)
         {
-          const GDBusInterfaceInfo *id_n = (const GDBusInterfaceInfo *) interfaces->pdata[n];
+          if (g_strcmp0 (interfaces[n]->name, interface_name) == 0)
-          if (g_strcmp0 (id_n->name, interface_name) == 0)
+            interface_info = interfaces[n];
-            interface_info = id_n;
         }
 
       /* Fail with org.freedesktop.DBus.Error.InvalidArgs if the user-code
@@ -5437,8 +5443,12 @@ handle_subtree_method_invocation (GDBusConnection *connection,
 
  out:
   if (interfaces != NULL)
-    g_ptr_array_unref (interfaces);
+    {
-  g_strfreev (children);
+      for (n = 0; interfaces[n] != NULL; n++)
+        g_dbus_interface_info_unref (interfaces[n]);
+      g_free (interfaces);
+    }
+
   return handled;
 }
 

gio/gdbusconnection.h

@@ -325,12 +325,25 @@ typedef gchar** (*GDBusSubtreeEnumerateFunc) (GDBusConnection       *connection,
  *
  * The type of the @introspect function in #GDBusSubtreeVTable.
  *
- * Returns: A newly-allocated #GPtrArray with pointers to #GDBusInterfaceInfo describing
+ * This function should return %NULL to indicate that there is no object
- * the interfaces implemented by @node.
+ * at this node.
+ *
+ * If this function returns non-%NULL, the return value is expected to
+ * be a %NULL-terminated array of pointers to #GDBusInterfaceInfo
+ * structures describing the interfaces implemented by @node.  This
+ * array will have g_dbus_interface_info_unref() called on each item
+ * before being freed with g_free().
+ *
+ * The difference between returning %NULL and an array containing zero
+ * items is that the standard DBus interfaces will returned to the
+ * remote introspector in the empty array case, but not in the %NULL
+ * case.
+ *
+ * Returns: A %NULL-terminated array of pointers to #GDBusInterfaceInfo, or %NULL.
  *
  * Since: 2.26
  */
-typedef GPtrArray *(*GDBusSubtreeIntrospectFunc) (GDBusConnection       *connection,
+typedef GDBusInterfaceInfo ** (*GDBusSubtreeIntrospectFunc) (GDBusConnection       *connection,
                                                              const gchar           *sender,
                                                              const gchar           *object_path,
                                                              const gchar           *node,

gio/tests/gdbus-export.c

@@ -614,37 +614,38 @@ subtree_enumerate (GDBusConnection       *connection,
 }
 
 /* Only allows certain objects, and aborts on unknowns */
-static GPtrArray *
+static GDBusInterfaceInfo **
 subtree_introspect (GDBusConnection       *connection,
                     const gchar           *sender,
                     const gchar           *object_path,
                     const gchar           *node,
                     gpointer               user_data)
 {
-  GPtrArray *interfaces;
+  const GDBusInterfaceInfo *interfaces[2] = {
+     NULL /* filled in below */, NULL
+  };
 
   /* VPs implement the Foo interface, EVPs implement the Bar interface. The root
    * does not implement any interfaces
    */
-  interfaces = g_ptr_array_new ();
   if (g_str_has_prefix (node, "vp"))
     {
-      g_ptr_array_add (interfaces, (gpointer) &foo_interface_info);
+      interfaces[0] = &foo_interface_info;
     }
   else if (g_str_has_prefix (node, "evp"))
     {
-      g_ptr_array_add (interfaces, (gpointer) &bar_interface_info);
+      interfaces[0] = &bar_interface_info;
     }
   else if (g_strcmp0 (node, "/") == 0)
     {
-      /* do nothing */
+      return NULL;
     }
   else
     {
       g_assert_not_reached ();
     }
 
-  return interfaces;
+  return g_memdup (interfaces, 2 * sizeof (void *));
 }
 
 static const GDBusInterfaceVTable *
@@ -691,20 +692,16 @@ dynamic_subtree_enumerate (GDBusConnection       *connection,
 }
 
 /* Allow all objects to be introspected */
-static GPtrArray *
+static GDBusInterfaceInfo **
 dynamic_subtree_introspect (GDBusConnection       *connection,
                             const gchar           *sender,
                             const gchar           *object_path,
                             const gchar           *node,
                             gpointer               user_data)
 {
-  GPtrArray *interfaces;
+  const GDBusInterfaceInfo *interfaces[2] = { &dyna_interface_info, NULL };
 
-  /* All nodes (including the root node) implements the Dyna interface */
+  return g_memdup (interfaces, 2 * sizeof (void *));
-  interfaces = g_ptr_array_new ();
-  g_ptr_array_add (interfaces, (gpointer) &dyna_interface_info);
-
-  return interfaces;
 }
 
 static const GDBusInterfaceVTable *