src/hotspot/share/prims/jvm.cpp

*** 669,11 ***
      ResourceMark rm(THREAD);
      THROW_MSG_NULL(vmSymbols::java_lang_CloneNotSupportedException(), klass->external_name());
    }
  
    // Make shallow object copy
!   const size_t size = obj->size();
    oop new_obj_oop = nullptr;
    if (obj->is_array()) {
      const int length = ((arrayOop)obj())->length();
      new_obj_oop = Universe::heap()->array_allocate(klass, size, length,
                                                     /* do_zero */ true, CHECK_NULL);
--- 669,16 ---
      ResourceMark rm(THREAD);
      THROW_MSG_NULL(vmSymbols::java_lang_CloneNotSupportedException(), klass->external_name());
    }
  
    // Make shallow object copy
!   // With compact object headers, the original might have been expanded by GC
+   // for the identity hash. The clone must be allocated at the base size, since
+   // it will get a fresh (not-hashed, not-expanded) mark word.
+   const size_t size = UseCompactObjectHeaders
+     ? obj->base_size_given_klass(obj->mark(), klass)
+     : obj->size();
    oop new_obj_oop = nullptr;
    if (obj->is_array()) {
      const int length = ((arrayOop)obj())->length();
      new_obj_oop = Universe::heap()->array_allocate(klass, size, length,
                                                     /* do_zero */ true, CHECK_NULL);