diff -r bfb419c66ae9 -r a4cdca87152b src/hotspot/share/gc/z/zPage.hpp
--- a/src/hotspot/share/gc/z/zPage.hpp	Mon Oct 28 11:26:53 2019 +0100
+++ b/src/hotspot/share/gc/z/zPage.hpp	Mon Oct 28 11:27:27 2019 +0100
@@ -112,4 +112,9 @@
   void print() const;
 };
 
+class ZPageClosure {
+public:
+  virtual void do_page(const ZPage* page) = 0;
+};
+
 #endif // SHARE_GC_Z_ZPAGE_HPP