--- old/src/hotspot/share/gc/shared/memAllocator.hpp	2019-07-08 17:19:16.630723503 +0000
+++ new/src/hotspot/share/gc/shared/memAllocator.hpp	2019-07-08 17:19:16.362723225 +0000
@@ -55,7 +55,7 @@
   { }
 
   // This function clears the memory of the object
-  void mem_clear(HeapWord* mem) const;
+  virtual HeapWord* mem_clear(HeapWord* mem) const;
   // This finish constructing an oop by installing the mark word and the Klass* pointer
   // last. At the point when the Klass pointer is initialized, this is a constructed object
   // that must be parseable as an oop by concurrent collectors.