Deprecate g_type_class_add_private()

It's been 4 years and 8 development cycles since we introduced
G_ADD_PRIVATE and offset-based private data access. It is now
time to finally deprecate the old mechanism.

Closes: #699

gobject/gtype.c

@@ -76,7 +76,7 @@
  *
  * Type instance and class structs are limited to a total of 64 KiB,
  * including all parent types. Similarly, type instances' private data
- * (as created by g_type_class_add_private()) are limited to a total of
+ * (as created by G_ADD_PRIVATE()) are limited to a total of
  * 64 KiB. If a type instance needs a large static buffer, allocate it
  * separately (typically by using #GArray or #GPtrArray) and put a pointer
  * to the buffer in the structure.
@@ -4562,6 +4562,8 @@ gobject_init_ctor (void)
  * ]|
  *
  * Since: 2.4
+ * Deprecated: 2.58: Use the G_ADD_PRIVATE() macro with the `G_DEFINE_*`
+ *   family of macros to add instance private data to a type
  */
 void
 g_type_class_add_private (gpointer g_class,

gobject/gtype.h

@@ -634,6 +634,8 @@ struct _GTypeQuery
  * This macro should only be used in type implementations.
  * 
  * Since: 2.4
+ * Deprecated: 2.58: Use %G_ADD_PRIVATE and the generated
+ *   `your_type_get_instance_private()` function instead
  * Returns: (not nullable): a pointer to the private data structure
  */
 #define G_TYPE_INSTANCE_GET_PRIVATE(instance, g_type, c_type)   ((c_type*) g_type_instance_get_private ((GTypeInstance*) (instance), (g_type)))
@@ -1297,7 +1299,7 @@ void  g_type_interface_add_prerequisite (GType			     interface_type,
 GLIB_AVAILABLE_IN_ALL
 GType*g_type_interface_prerequisites    (GType                       interface_type,
 					 guint                      *n_prerequisites);
-GLIB_AVAILABLE_IN_ALL
+GLIB_DEPRECATED_IN_2_58
 void     g_type_class_add_private       (gpointer                    g_class,
                                          gsize                       private_size);
 GLIB_AVAILABLE_IN_2_38

gobject/tests/private.c

@@ -128,7 +128,9 @@ G_DEFINE_TYPE (TestMixed, test_mixed, test_object_get_type ())
 static void
 test_mixed_class_init (TestMixedClass *klass)
 {
+G_GNUC_BEGIN_IGNORE_DEPRECATIONS
   g_type_class_add_private (klass, sizeof (TestMixedPrivate));
+G_GNUC_END_IGNORE_DEPRECATIONS
 }
 
 static void

tests/gobject/testgobject.c

@@ -154,6 +154,13 @@ static gboolean	test_signal_accumulator	(GSignalInvocationHint	*ihint,
 static gchar*	test_object_test_signal	(TestObject		*tobject,
 					 TestIface		*iface_object,
 					 gpointer		 tdata);
+static gint TestObject_private_offset;
+static inline gpointer
+test_object_get_instance_private (TestObject *self)
+{
+  return (G_STRUCT_MEMBER_P (self, TestObject_private_offset));
+}
+
 static GType
 test_object_get_type (void)
 {
@@ -177,6 +184,9 @@ test_object_get_type (void)
 
       test_object_type = g_type_register_static (G_TYPE_OBJECT, "TestObject", &test_object_info, 0);
       g_type_add_interface_static (test_object_type, TEST_TYPE_IFACE, &iface_info);
+
+      TestObject_private_offset =
+        g_type_add_instance_private (test_object_type, sizeof (TestObjectPrivate));
     }
 
   return test_object_type;
@@ -185,6 +195,7 @@ static void
 test_object_class_init (TestObjectClass *class)
 {
   /*  GObjectClass *gobject_class = G_OBJECT_CLASS (class); */
+  g_type_class_adjust_private_offset (class, &TestObject_private_offset);
 
   class->test_signal = test_object_test_signal;
 
@@ -195,15 +206,11 @@ test_object_class_init (TestObjectClass *class)
 		test_signal_accumulator, NULL,
 		g_cclosure_marshal_STRING__OBJECT_POINTER,
 		G_TYPE_STRING, 2, TEST_TYPE_IFACE, G_TYPE_POINTER);
-
-  g_type_class_add_private (class, sizeof (TestObjectPrivate));
 }
 static void
 test_object_init (TestObject *tobject)
 {
-  TestObjectPrivate *priv;
-
-  priv = TEST_OBJECT_GET_PRIVATE (tobject);
+  TestObjectPrivate *priv = test_object_get_instance_private (tobject);
 
   g_assert (priv);
 
@@ -215,9 +222,7 @@ test_object_init (TestObject *tobject)
 static void
 test_object_check_private_init (TestObject *tobject)
 {
-  TestObjectPrivate *priv;
-
-  priv = TEST_OBJECT_GET_PRIVATE (tobject);
+  TestObjectPrivate *priv = test_object_get_instance_private (tobject);
 
   g_print ("private data during initialization: %u == %u\n", priv->dummy1, 54321);
   g_assert (priv->dummy1 == 54321);
@@ -317,6 +322,12 @@ struct _DerivedObjectPrivate
 };
 static void derived_object_class_init (DerivedObjectClass *class);
 static void derived_object_init       (DerivedObject      *dobject);
+static gint DerivedObject_private_offset;
+static inline gpointer
+derived_object_get_instance_private (DerivedObject *self)
+{
+  return (G_STRUCT_MEMBER_P (self, DerivedObject_private_offset));
+}
 static GType
 derived_object_get_type (void)
 {
@@ -340,6 +351,8 @@ derived_object_get_type (void)
 
       derived_object_type = g_type_register_static (TEST_TYPE_OBJECT, "DerivedObject", &derived_object_info, 0);
       g_type_add_interface_static (derived_object_type, TEST_TYPE_IFACE, &iface_info);
+      DerivedObject_private_offset =
+        g_type_add_instance_private (derived_object_type, sizeof (DerivedObjectPrivate));
     }
 
   return derived_object_type;
@@ -347,7 +360,7 @@ derived_object_get_type (void)
 static void
 derived_object_class_init (DerivedObjectClass *class)
 {
-  g_type_class_add_private (class, sizeof (DerivedObjectPrivate));
+  g_type_class_adjust_private_offset (class, &DerivedObject_private_offset);
 }
 static void
 derived_object_init (DerivedObject *dobject)
@@ -355,14 +368,13 @@ derived_object_init (DerivedObject *dobject)
   TestObjectPrivate *test_priv;
   DerivedObjectPrivate *derived_priv;
 
-  derived_priv = DERIVED_OBJECT_GET_PRIVATE (dobject);
+  derived_priv = derived_object_get_instance_private (dobject);
 
   g_assert (derived_priv);
 
-  test_priv = TEST_OBJECT_GET_PRIVATE (dobject);
+  test_priv = test_object_get_instance_private (TEST_OBJECT (dobject));
   
   g_assert (test_priv);
-
 }
 
 /* --- main --- */
@@ -411,7 +423,7 @@ main (int   argc,
   iface_print_string (TEST_IFACE (sigarg), "iface-string-from-test-type");
   iface_print_string (TEST_IFACE (dobject), "iface-string-from-derived-type");
 
-  priv = TEST_OBJECT_GET_PRIVATE (dobject);
+  priv = test_object_get_instance_private (TEST_OBJECT (dobject));
   g_print ("private data after initialization: %u == %u\n", priv->dummy1, 54321);
   g_assert (priv->dummy1 == 54321);