Now I really confirm this compiles without warnings on gcc 7.2.0, 6.3.0, 5.4.1, 4.9.2, 4.8.5.
Welcome to OpenJDK!
===================
For information about building OpenJDK, including how to fully retrieve all
source code, please see either of these:
* doc/building.html (html version)
* doc/building.md (markdown version)
See http://openjdk.java.net/ for more information about OpenJDK.