--- /dev/null	2019-04-08 17:27:49.000000000 +0530
+++ new/src/jdk.jextract/share/classes/com/sun/tools/jextract/BuiltinTypesHandler.java	2019-04-08 17:27:43.000000000 +0530
@@ -0,0 +1,103 @@
+/*
+ * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+package com.sun.tools.jextract;
+
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.logging.Logger;
+import com.sun.tools.jextract.parser.Parser;
+import com.sun.tools.jextract.tree.HeaderTree;
+import com.sun.tools.jextract.tree.SimpleTreeVisitor;
+import com.sun.tools.jextract.tree.Tree;
+import com.sun.tools.jextract.tree.TreeMaker;
+import com.sun.tools.jextract.tree.TreePhase;
+import com.sun.tools.jextract.tree.TreePrinter;
+import jdk.internal.clang.Cursor;
+
+/**
+ * Handles builtin struct/union types by creating fake Trees in a
+ * builtin header tree.
+ */
+final class BuiltinTypesHandler extends SimpleTreeVisitor<Void, Void>
+        implements TreePhase {
+    private final TreeMaker treeMaker = new TreeMaker();
+
+    // Potential Tree instances that will go into transformed HeaderTree
+    // are collected in this list.
+    private List<Tree> decls = new ArrayList<>();
+    private final Log log;
+
+    public BuiltinTypesHandler(Context ctx) {
+        this.log = ctx.log;
+    }
+
+    @Override
+    public HeaderTree transform(HeaderTree ht) {
+        // Process all header declarations are collect potential
+        // declarations that will go into transformed HeaderTree
+        // into the this.decls field.
+        ht.accept(this, null);
+
+        return treeMaker.createHeader(ht.cursor(), ht.path(), decls);
+    }
+
+    @Override
+    public Void defaultAction(Tree tree, Void v) {
+        /*
+         * There are built-in types like struct __va_list_tag. These are not exposed
+         * as declaration cursor for any headers, but are available from Type objects.
+         * We've to walk and check null file path to detect these Cursors and create Trees.
+         */
+        Utils.getBuiltinRecordTypes(tree.type()).forEach(c -> {
+            decls.add(treeMaker.createTree(c));
+        });
+
+        decls.add(tree);
+        return null;
+    }
+
+    @Override
+    public Void visitHeader(HeaderTree ht, Void v) {
+        ht.declarations().forEach(decl -> decl.accept(this, null));
+        return null;
+    }
+
+    // test main to manually check this visitor
+    public static void main(String[] args) {
+        if (args.length == 0) {
+            System.err.println("Expected a header file");
+            return;
+        }
+
+        Context context = Context.createDefault();
+        Parser p = new Parser(context, true);
+        Path builtinInc = Paths.get(System.getProperty("java.home"), "conf", "jextract");
+        List<String> clangArgs = List.of("-I" + builtinInc);
+        HeaderTree header = p.parse(Paths.get(args[0]), clangArgs);
+        TreePrinter printer = new TreePrinter();
+        BuiltinTypesHandler handler = new BuiltinTypesHandler(context);
+        handler.transform(header).accept(printer, null);
+    }
+}