diff -r 13588c901957 -r 9cf78a70fa4f src/hotspot/share/oops/oopsHierarchy.hpp
--- a/src/hotspot/share/oops/oopsHierarchy.hpp	Thu Oct 17 20:27:44 2019 +0100
+++ b/src/hotspot/share/oops/oopsHierarchy.hpp	Thu Oct 17 20:53:35 2019 +0100
@@ -39,15 +39,14 @@
 typedef juint  narrowKlass;
 
 typedef void* OopOrNarrowOopStar;
-typedef class   markOopDesc*                markOop;
 
 #ifndef CHECK_UNHANDLED_OOPS
 
-typedef class oopDesc*                            oop;
+typedef class oopDesc*                    oop;
 typedef class   instanceOopDesc*            instanceOop;
-typedef class   arrayOopDesc*                    arrayOop;
+typedef class   arrayOopDesc*               arrayOop;
 typedef class     objArrayOopDesc*            objArrayOop;
-typedef class     typeArrayOopDesc*            typeArrayOop;
+typedef class     typeArrayOopDesc*           typeArrayOop;
 
 #else
 
@@ -74,7 +73,7 @@
 class PromotedObject;
 class oopDesc;
 
-extern bool CheckUnhandledOops;
+extern "C" bool CheckUnhandledOops;
 
 class oop {
   oopDesc* _o;
@@ -82,7 +81,6 @@
   void register_oop();
   void unregister_oop();
 
-  // friend class markOop;
 public:
   void set_obj(const void* p)         {
     raw_set_obj(p);
@@ -102,9 +100,9 @@
 
   // General access
   oopDesc*  operator->() const        { return obj(); }
-  bool operator==(const oop o) const;
+  bool operator==(const oop o) const  { return obj() == o.obj(); }
   bool operator==(void *p) const      { return obj() == p; }
-  bool operator!=(const volatile oop o) const;
+  bool operator!=(const volatile oop o) const { return obj() != o.obj(); }
   bool operator!=(void *p) const      { return obj() != p; }
 
   // Assignment
@@ -121,7 +119,6 @@
   operator oopDesc* () const volatile { return obj(); }
   operator intptr_t* () const         { return (intptr_t*)obj(); }
   operator PromotedObject* () const   { return (PromotedObject*)obj(); }
-  operator markOop () const volatile  { return markOop(obj()); }
   operator address   () const         { return (address)obj(); }
 
   // from javaCalls.cpp
@@ -193,10 +190,6 @@
   return (T)(CHECK_UNHANDLED_OOPS_ONLY((void*))o);
 }
 
-inline bool check_obj_alignment(oop obj) {
-  return (cast_from_oop<intptr_t>(obj) & MinObjAlignmentInBytesMask) == 0;
-}
-
 // The metadata hierarchy is separate from the oop hierarchy
 
 //      class MetaspaceObj