+/* Return whether STRUCT_TYPE has an anonymous field with type TYPE.
+ This is used to implement -fplan9-extensions. */
+
+static bool
+find_anonymous_field_with_type (tree struct_type, tree type)
+{
+ tree field;
+ bool found;
+
+ gcc_assert (TREE_CODE (struct_type) == RECORD_TYPE
+ || TREE_CODE (struct_type) == UNION_TYPE);
+ found = false;
+ for (field = TYPE_FIELDS (struct_type);
+ field != NULL_TREE;
+ field = TREE_CHAIN (field))
+ {
+ if (DECL_NAME (field) == NULL
+ && comptypes (type, TYPE_MAIN_VARIANT (TREE_TYPE (field))))
+ {
+ if (found)
+ return false;
+ found = true;
+ }
+ else if (DECL_NAME (field) == NULL
+ && (TREE_CODE (TREE_TYPE (field)) == RECORD_TYPE
+ || TREE_CODE (TREE_TYPE (field)) == UNION_TYPE)
+ && find_anonymous_field_with_type (TREE_TYPE (field), type))
+ {
+ if (found)
+ return false;
+ found = true;
+ }
+ }
+ return found;
+}
+
+/* RHS is an expression whose type is pointer to struct. If there is
+ an anonymous field in RHS with type TYPE, then return a pointer to
+ that field in RHS. This is used with -fplan9-extensions. This
+ returns NULL if no conversion could be found. */
+
+static tree
+convert_to_anonymous_field (location_t location, tree type, tree rhs)
+{
+ tree rhs_struct_type, lhs_main_type;
+ tree field, found_field;
+ bool found_sub_field;
+ tree ret;
+
+ gcc_assert (POINTER_TYPE_P (TREE_TYPE (rhs)));
+ rhs_struct_type = TREE_TYPE (TREE_TYPE (rhs));
+ gcc_assert (TREE_CODE (rhs_struct_type) == RECORD_TYPE
+ || TREE_CODE (rhs_struct_type) == UNION_TYPE);
+
+ gcc_assert (POINTER_TYPE_P (type));
+ lhs_main_type = TYPE_MAIN_VARIANT (TREE_TYPE (type));
+
+ found_field = NULL_TREE;
+ found_sub_field = false;
+ for (field = TYPE_FIELDS (rhs_struct_type);
+ field != NULL_TREE;
+ field = TREE_CHAIN (field))
+ {
+ if (DECL_NAME (field) != NULL_TREE
+ || (TREE_CODE (TREE_TYPE (field)) != RECORD_TYPE
+ && TREE_CODE (TREE_TYPE (field)) != UNION_TYPE))
+ continue;
+ if (comptypes (lhs_main_type, TYPE_MAIN_VARIANT (TREE_TYPE (field))))
+ {
+ if (found_field != NULL_TREE)
+ return NULL_TREE;
+ found_field = field;
+ }
+ else if (find_anonymous_field_with_type (TREE_TYPE (field),
+ lhs_main_type))
+ {
+ if (found_field != NULL_TREE)
+ return NULL_TREE;
+ found_field = field;
+ found_sub_field = true;
+ }
+ }
+
+ if (found_field == NULL_TREE)
+ return NULL_TREE;
+
+ ret = fold_build3_loc (location, COMPONENT_REF, TREE_TYPE (found_field),
+ build_fold_indirect_ref (rhs), found_field,
+ NULL_TREE);
+ ret = build_fold_addr_expr_loc (location, ret);
+
+ if (found_sub_field)
+ {
+ ret = convert_to_anonymous_field (location, type, ret);
+ gcc_assert (ret != NULL_TREE);
+ }
+
+ return ret;
+}
+