GType: introduce GTYPE_TO_POINTER/GPOINTER_TO_TYPE

On CHERI-enabled systems we use uintptr_t as the underlying storage for
GType and therefore casting to gsize strips the upper bits from a pointer.
Fix this by casting via uintptr_t instead and introduce a new set of
macros to convert between GType and pointers.

docs/reference/gobject/gobject-sections.txt

@@ -48,6 +48,8 @@ G_TYPE_CHECK_CLASS_TYPE
 G_TYPE_CHECK_VALUE
 G_TYPE_CHECK_VALUE_TYPE
 G_TYPE_FLAG_RESERVED_ID_BIT
+GPOINTER_TO_TYPE
+GTYPE_TO_POINTER
 g_type_init
 GTypeDebugFlags
 g_type_init_with_debug_flags

gio/gdbus-2.0/codegen/codegen.py

@@ -5160,12 +5160,12 @@ class CodeGenerator:
         )
         for i in self.ifaces:
             self.outfile.write(
-                '      g_hash_table_insert (lookup_hash, (gpointer) "%s", GSIZE_TO_POINTER (%sTYPE_%s_PROXY));\n'
+                '      g_hash_table_insert (lookup_hash, (gpointer) "%s", (gpointer) (guintptr) (%sTYPE_%s_PROXY));\n'
                 % (i.name, i.ns_upper, i.name_upper)
             )
         self.outfile.write("      g_once_init_leave (&once_init_value, 1);\n" "    }\n")
         self.outfile.write(
-            "  ret = (GType) GPOINTER_TO_SIZE (g_hash_table_lookup (lookup_hash, interface_name));\n"
+            "  ret = (GType) (guintptr) (g_hash_table_lookup (lookup_hash, interface_name));\n"
             "  if (ret == (GType) 0)\n"
             "    ret = G_TYPE_DBUS_PROXY;\n"
         )

glib/docs.c

@@ -1108,6 +1108,12 @@
  * @s: #gsize to stuff into the pointer
  *
  * Stuffs a #gsize into a pointer type.
+ *
+ * Remember, you may not store pointers in integers. This is not portable
+ * in any way, shape or form. These macros only allow storing integers in
+ * pointers, and preserve all bits of a pointer (e.g. on CHERI systems).
+ * The only types that can store pointers as well as integers are #guintptr
+ * and #gintptr.
  */
 
 /**
@@ -1116,6 +1122,14 @@
  *
  * Extracts a #gsize from a pointer. The #gsize must have
  * been stored in the pointer with GSIZE_TO_POINTER().
+ *
+ * Remember, you may not store pointers in integers. This is not portable
+ * in any way, shape or form. These macros only allow storing integers in
+ * pointers, and preserve all bits of a pointer (e.g. on CHERI systems).
+ * The only types that can store pointers as well as integers are #guintptr
+ * and #gintptr.
+ *
+ * See also GPOINTER_TO_TYPE() for #gsize.
  */
  
 /* Byte order {{{1 */

gobject/gclosure.c

@@ -1175,7 +1175,7 @@ g_signal_type_cclosure_new (GType    itype,
   g_return_val_if_fail (G_TYPE_IS_CLASSED (itype) || G_TYPE_IS_INTERFACE (itype), NULL);
   g_return_val_if_fail (struct_offset >= sizeof (GTypeClass), NULL);
   
-  closure = g_closure_new_simple (sizeof (GClosure), (gpointer) itype);
+  closure = g_closure_new_simple (sizeof (GClosure), GTYPE_TO_POINTER (itype));
   if (G_TYPE_IS_INTERFACE (itype))
     {
       g_closure_set_meta_marshal (closure, GUINT_TO_POINTER (struct_offset), g_type_iface_meta_marshal);

gobject/gparam.c

@@ -1234,7 +1234,7 @@ g_param_spec_pool_list_owned (GParamSpecPool *pool,
   
   g_mutex_lock (&pool->mutex);
   data[0] = NULL;
-  data[1] = (gpointer) owner_type;
+  data[1] = GTYPE_TO_POINTER (owner_type);
   g_hash_table_foreach (pool->hash_table, pool_list, &data);
   g_mutex_unlock (&pool->mutex);
 
@@ -1373,7 +1373,7 @@ g_param_spec_pool_list (GParamSpecPool *pool,
   d = g_type_depth (owner_type);
   slists = g_new0 (GSList*, d);
   data[0] = slists;
-  data[1] = (gpointer) owner_type;
+  data[1] = GTYPE_TO_POINTER (owner_type);
   data[2] = pool->hash_table;
   data[3] = &n_pspecs;
 

gobject/gparamspecs.c

@@ -1222,7 +1222,7 @@ param_gtype_set_default (GParamSpec *pspec,
 {
   GParamSpecGType *tspec = G_PARAM_SPEC_GTYPE (pspec);
 
-  value->data[0].v_pointer = GSIZE_TO_POINTER (tspec->is_a_type);
+  value->data[0].v_pointer = GTYPE_TO_POINTER (tspec->is_a_type);
 }
 
 static gboolean
@@ -1230,7 +1230,7 @@ param_gtype_is_valid (GParamSpec   *pspec,
                       const GValue *value)
 {
   GParamSpecGType *tspec = G_PARAM_SPEC_GTYPE (pspec);
-  GType gtype = GPOINTER_TO_SIZE (value->data[0].v_pointer);
+  GType gtype = GPOINTER_TO_TYPE (value->data[0].v_pointer);
   
   return tspec->is_a_type == G_TYPE_NONE ||
          g_type_is_a (gtype, tspec->is_a_type);
@@ -1241,12 +1241,12 @@ param_gtype_validate (GParamSpec *pspec,
 		      GValue     *value)
 {
   GParamSpecGType *tspec = G_PARAM_SPEC_GTYPE (pspec);
-  GType gtype = GPOINTER_TO_SIZE (value->data[0].v_pointer);
+  GType gtype = GPOINTER_TO_TYPE (value->data[0].v_pointer);
   guint changed = 0;
   
   if (tspec->is_a_type != G_TYPE_NONE && !g_type_is_a (gtype, tspec->is_a_type))
     {
-      value->data[0].v_pointer = GSIZE_TO_POINTER (tspec->is_a_type);
+      value->data[0].v_pointer = GTYPE_TO_POINTER (tspec->is_a_type);
       changed++;
     }
   
@@ -1258,8 +1258,8 @@ param_gtype_values_cmp (GParamSpec   *pspec,
 			const GValue *value1,
 			const GValue *value2)
 {
-  GType p1 = GPOINTER_TO_SIZE (value1->data[0].v_pointer);
+  GType p1 = GPOINTER_TO_TYPE (value1->data[0].v_pointer);
-  GType p2 = GPOINTER_TO_SIZE (value2->data[0].v_pointer);
+  GType p2 = GPOINTER_TO_TYPE (value2->data[0].v_pointer);
 
   /* not much to compare here, try to at least provide stable lesser/greater result */
 

gobject/gtype.c

@@ -422,7 +422,7 @@ type_node_any_new_W (TypeNode             *pnode,
 #endif
     }
   else
-    type = (GType) node;
+    type = GPOINTER_TO_TYPE (node);
   
   g_assert ((type & TYPE_ID_MASK) == 0);
   
@@ -497,7 +497,7 @@ type_node_any_new_W (TypeNode             *pnode,
   node->global_gdata = NULL;
   g_hash_table_insert (static_type_nodes_ht,
 		       (gpointer) g_quark_to_string (node->qname),
-		       (gpointer) type);
+		       GTYPE_TO_POINTER (type));
 
   g_atomic_int_inc ((gint *)&type_registration_serial);
 
@@ -3444,7 +3444,7 @@ g_type_from_name (const gchar *name)
   g_return_val_if_fail (name != NULL, 0);
   
   G_READ_LOCK (&type_rw_lock);
-  type = (GType) g_hash_table_lookup (static_type_nodes_ht, name);
+  type = GPOINTER_TO_TYPE (g_hash_table_lookup (static_type_nodes_ht, name));
   G_READ_UNLOCK (&type_rw_lock);
   
   return type;

gobject/gtype.h

@@ -2710,6 +2710,27 @@ const gchar *    g_type_name_from_class         (GTypeClass	*g_class);
  */
 #define	G_TYPE_FLAG_RESERVED_ID_BIT	((GType) (1 << 0))
 
+/**
+ * GPOINTER_TO_TYPE:
+ * @p: The pointer to convert to a #GType
+ *
+ * This macro should be used instead of GPOINTER_TO_SIZE() to ensure
+ * portability since #GType is not guaranteed to be the same as #gsize.
+ *
+ * Since: 2.80
+ */
+#define GPOINTER_TO_TYPE(p) ((GType) (guintptr) (p)) GOBJECT_AVAILABLE_MACRO_IN_2_80
+/**
+ * GTYPE_TO_POINTER:
+ * @t: The #GType to convert to a pointer
+ *
+ * This macro should be used instead of GSIZE_TO_POINTER() to ensure
+ * portability since #GType is not guaranteed to be the same as #gsize.
+ *
+ * Since: 2.80
+ */
+#define GTYPE_TO_POINTER(t) ((gpointer) (guintptr) (t)) GOBJECT_AVAILABLE_MACRO_IN_2_80
+
 G_END_DECLS
 
 #endif /* __G_TYPE_H__ */

gobject/gvaluetypes.c

@@ -1208,7 +1208,7 @@ g_value_set_gtype (GValue *value,
 {
   g_return_if_fail (G_VALUE_HOLDS_GTYPE (value));
 
-  value->data[0].v_pointer = GSIZE_TO_POINTER (v_gtype);
+  value->data[0].v_pointer = GTYPE_TO_POINTER (v_gtype);
   
 }
 
@@ -1227,7 +1227,7 @@ g_value_get_gtype (const GValue *value)
 {
   g_return_val_if_fail (G_VALUE_HOLDS_GTYPE (value), 0);
 
-  return GPOINTER_TO_SIZE (value->data[0].v_pointer);
+  return GPOINTER_TO_TYPE (value->data[0].v_pointer);
 }
 
 /**