src/hotspot/share/oops/markOop.hpp

*** 102,111 ****
--- 102,116 ----
  
  class markWord {
   private:
    uintptr_t _value;
  
+   // Poison - prevent casts and pointer conversions.
+   // Use to_pointer and from_pointer instead.
+   template<typename T> operator T();
+   markWord(const volatile void*);
+ 
   public:
    explicit markWord(uintptr_t value) : _value(value) {}
  
    markWord() { /* uninitialized */}
  
*** 113,122 ****
--- 118,130 ----
    // destructable, copyable, and assignable.
  
    static markWord from_pointer(void* ptr) {
      return markWord((uintptr_t)ptr);
    }
+   void* to_pointer() const {
+     return (void*)_value;
+   }
  
    bool operator==(const markWord& other) const {
      return _value == other._value;
    }
    bool operator!=(const markWord& other) const {
*** 125,134 ****
--- 133,144 ----
  
    // Conversion
    uintptr_t value() const { return _value; }
  
    // Constants
+   static const uintptr_t zero     = 0;
+ 
    enum { age_bits                 = 4,
           lock_bits                = 2,
           biased_lock_bits         = 1,
           max_hash_bits            = BitsPerWord - age_bits - lock_bits - biased_lock_bits,
           hash_bits                = max_hash_bits > 31 ? 31 : max_hash_bits,
*** 241,251 ****
    // an existing stacklock.  0 indicates the markword is "BUSY".
    // Lockword mutators that use a LD...CAS idiom should always
    // check for and avoid overwriting a 0 value installed by some
    // other thread.  (They should spin or block instead.  The 0 value
    // is transient and *should* be short-lived).
!   static markWord INFLATING() { return markWord(0); }    // inflate-in-progress
  
    // Should this header be preserved during GC?
    inline bool must_be_preserved(oop obj_containing_mark) const;
    inline bool must_be_preserved_with_bias(oop obj_containing_mark) const;
  
--- 251,261 ----
    // an existing stacklock.  0 indicates the markword is "BUSY".
    // Lockword mutators that use a LD...CAS idiom should always
    // check for and avoid overwriting a 0 value installed by some
    // other thread.  (They should spin or block instead.  The 0 value
    // is transient and *should* be short-lived).
!   static markWord INFLATING() { return markWord(zero); }    // inflate-in-progress
  
    // Should this header be preserved during GC?
    inline bool must_be_preserved(oop obj_containing_mark) const;
    inline bool must_be_preserved_with_bias(oop obj_containing_mark) const;