[glib/signal-performance: 6/10] Add _g_closure_is_void to check for NULL vfuncs

[Alexander Larsson <alexl src gnome org>]

commit 1c4f0ca48332f2e550b5e5e17365c43912958cee
Author: Alexander Larsson <alexl redhat com>
Date:   Tue Feb 28 15:48:20 2012 +0100

    Add _g_closure_is_void to check for NULL vfuncs
    
    https://bugzilla.gnome.org/show_bug.cgi?id=661140

 gobject/gclosure.c      |   36 ++++++++++++++++++++++++++++++++++++
 gobject/gtype-private.h |    2 ++
 2 files changed, 38 insertions(+), 0 deletions(-)
---
diff --git a/gobject/gclosure.c b/gobject/gclosure.c
index bf79754..4cee41c 100644
--- a/gobject/gclosure.c
+++ b/gobject/gclosure.c
@@ -1025,6 +1025,42 @@ g_type_iface_meta_marshal (GClosure       *closure,
 		      callback);
 }
 
+gboolean
+_g_closure_is_void (GClosure *closure,
+		    gpointer instance)
+{
+  GRealClosure *real_closure;
+  GTypeClass *class;
+  gpointer callback;
+  GType itype;
+  guint offset;
+
+  if (closure->is_invalid)
+    return TRUE;
+
+  real_closure = G_REAL_CLOSURE (closure);
+
+  if (real_closure->meta_marshal == g_type_iface_meta_marshal)
+    {
+      itype = (GType) closure->data;
+      offset = GPOINTER_TO_UINT (real_closure->meta_marshal_data);
+
+      class = G_TYPE_INSTANCE_GET_INTERFACE (instance, itype, GTypeClass);
+      callback = G_STRUCT_MEMBER (gpointer, class, offset);
+      return callback == NULL;
+    }
+  else if (real_closure->meta_marshal == g_type_class_meta_marshal)
+    {
+      offset = GPOINTER_TO_UINT (real_closure->meta_marshal_data);
+
+      class = G_TYPE_INSTANCE_GET_CLASS (instance, itype, GTypeClass);
+      callback = G_STRUCT_MEMBER (gpointer, class, offset);
+      return callback == NULL;
+    }
+
+  return FALSE;
+}
+
 static void
 g_type_iface_meta_marshalv (GClosure *closure,
 			    GValue   *return_value,
diff --git a/gobject/gtype-private.h b/gobject/gtype-private.h
index 9cbea77..04a252b 100644
--- a/gobject/gtype-private.h
+++ b/gobject/gtype-private.h
@@ -60,6 +60,8 @@ void            _g_type_boxed_init      (GType          type,
                                          GBoxedCopyFunc copy_func,
                                          GBoxedFreeFunc free_func);
 
+gboolean    _g_closure_is_void (GClosure       *closure,
+				gpointer        instance);
 gboolean    _g_closure_supports_invoke_va (GClosure       *closure);
 void        _g_closure_set_va_marshal (GClosure       *closure,
 				       GVaClosureMarshal marshal);