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 11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 12  * version 2 for more details (a copy is included in the LICENSE file that
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 24 
 25 #ifndef SHARE_OOPS_OOPSHIERARCHY_HPP
 26 #define SHARE_OOPS_OOPSHIERARCHY_HPP
 27 
 28 #include "metaprogramming/primitiveConversions.hpp"
 29 #include "utilities/globalDefinitions.hpp"
 30 
 31 #include <type_traits>
 32 
 33 // OBJECT hierarchy
 34 // This hierarchy is a representation hierarchy, i.e. if A is a superclass
 35 // of B, A's representation is a prefix of B's representation.
 36 
 37 // Global offset instead of address for an oop within a java object.
 38 enum class narrowOop : uint32_t { null = 0 };
 39 
 40 typedef void* OopOrNarrowOopStar;
 41 
 42 #ifndef CHECK_UNHANDLED_OOPS
 43 
 44 typedef class oopDesc*                    oop;
 45 typedef class   instanceOopDesc*            instanceOop;
 46 typedef class     stackChunkOopDesc*          stackChunkOop;
 47 typedef class   arrayOopDesc*               arrayOop;
 48 typedef class     objArrayOopDesc*            objArrayOop;
 49 typedef class     typeArrayOopDesc*           typeArrayOop;
 50 
 51 #else
 52 
 53 // When CHECK_UNHANDLED_OOPS is defined, an "oop" is a class with a
 54 // carefully chosen set of constructors and conversion operators to go
 55 // to and from the underlying oopDesc pointer type.
 56 //
 57 // Because oop and its subclasses <type>Oop are class types, arbitrary
 58 // conversions are not accepted by the compiler.  Applying a cast to
 59 // an oop will cause the best matched conversion operator to be
 60 // invoked returning the underlying oopDesc* type if appropriate.
 61 // No copy constructors, explicit user conversions or operators of
 62 // numerical type should be defined within the oop class. Most C++
 63 // compilers will issue a compile time error concerning the overloading
 64 // ambiguity between operators of numerical and pointer types. If
 65 // a conversion to or from an oop to a numerical type is needed,
 66 // use the inline template methods, cast_*_oop, defined below.
 67 //
 68 // Converting null to oop to Handle implicit is no longer accepted by the
 69 // compiler because there are too many steps in the conversion.  Use Handle()
 70 // instead, which generates less code anyway.
 71 
 72 class Thread;
 73 class oopDesc;
 74 
 75 extern "C" bool CheckUnhandledOops;
 76 
 77 // Extra verification when creating and using oops.
 78 // Used to catch broken oops as soon as possible.
 79 using CheckOopFunctionPointer = void(*)(oopDesc*);
 80 extern CheckOopFunctionPointer check_oop_function;
 81 
 82 class oop {
 83   oopDesc* _o;
 84 
 85   void register_oop();
 86   void unregister_oop();
 87 
 88   // Extra verification of the oop
 89   void check_oop() const { if (check_oop_function != nullptr && _o != nullptr) check_oop_function(_o); }
 90 
 91   void on_usage() const  { check_oop(); }
 92   void on_construction() { check_oop(); if (CheckUnhandledOops)   register_oop(); }
 93   void on_destruction()  {              if (CheckUnhandledOops) unregister_oop(); }
 94 
 95 public:
 96   oop()             : _o(nullptr) { on_construction(); }
 97   oop(const oop& o) : _o(o._o)    { on_construction(); }
 98   oop(oopDesc* o)   : _o(o)       { on_construction(); }
 99   ~oop() {
100     on_destruction();
101   }
102 
103   oopDesc* obj() const                  { on_usage(); return _o; }
104 
105   oopDesc* operator->() const           { return obj(); }
106   operator oopDesc* () const            { return obj(); }
107 
108   bool operator==(const oop& o) const   { return obj() == o.obj(); }
109   bool operator!=(const oop& o) const   { return obj() != o.obj(); }
110 
111   bool operator==(std::nullptr_t) const { return obj() == nullptr; }
112   bool operator!=(std::nullptr_t) const { return obj() != nullptr; }
113 
114   oop& operator=(const oop& o)          { _o = o.obj(); return *this; }
115 };
116 
117 template<>
118 struct PrimitiveConversions::Translate<oop> : public std::true_type {
119   typedef oop Value;
120   typedef oopDesc* Decayed;
121 
122   static Decayed decay(Value x) { return x.obj(); }
123   static Value recover(Decayed x) { return oop(x); }
124 };
125 
126 #define DEF_OOP(type)                                                          \
127    class type##OopDesc;                                                        \
128    class type##Oop : public oop {                                              \
129      public:                                                                   \
130        type##Oop() : oop() {}                                                  \
131        type##Oop(const type##Oop& o) : oop(o) {}                               \
132        type##Oop(const oop& o) : oop(o) {}                                     \
133        type##Oop(type##OopDesc* o) : oop((oopDesc*)o) {}                       \
134        operator type##OopDesc* () const { return (type##OopDesc*)obj(); }      \
135        type##OopDesc* operator->() const {                                     \
136             return (type##OopDesc*)obj();                                      \
137        }                                                                       \
138        type##Oop& operator=(const type##Oop& o) {                              \
139             oop::operator=(o);                                                 \
140             return *this;                                                      \
141        }                                                                       \
142    };                                                                          \
143                                                                                \
144    template<>                                                                  \
145    struct PrimitiveConversions::Translate<type##Oop> : public std::true_type { \
146      typedef type##Oop Value;                                                  \
147      typedef type##OopDesc* Decayed;                                           \
148                                                                                \
149      static Decayed decay(Value x) { return (type##OopDesc*)x.obj(); }         \
150      static Value recover(Decayed x) { return type##Oop(x); }                  \
151    };
152 
153 DEF_OOP(instance);
154 DEF_OOP(stackChunk);
155 DEF_OOP(array);
156 DEF_OOP(objArray);
157 DEF_OOP(typeArray);
158 
159 #endif // CHECK_UNHANDLED_OOPS
160 
161 // Cast functions to convert to and from oops.
162 template <typename T> inline oop cast_to_oop(T value) {
163   return (oopDesc*)value;
164 }
165 template <typename T> inline T cast_from_oop(oop o) {
166   return (T)(CHECK_UNHANDLED_OOPS_ONLY((oopDesc*))o);
167 }
168 
169 inline intptr_t p2i(narrowOop o) {
170   return static_cast<intptr_t>(o);
171 }
172 
173 // The metadata hierarchy is separate from the oop hierarchy
174 
175 //      class MetaspaceObj
176 class   ConstMethod;
177 class   ConstantPoolCache;
178 class   MethodData;
179 //      class Metadata
180 class   Method;
181 class   ConstantPool;
182 
183 // The klass hierarchy is separate from the oop hierarchy.
184 
185 class Klass;
186 class   InstanceKlass;
187 class     InstanceMirrorKlass;
188 class     InstanceClassLoaderKlass;
189 class     InstanceRefKlass;
190 class     InstanceStackChunkKlass;
191 class   ArrayKlass;
192 class     ObjArrayKlass;
193 class     TypeArrayKlass;
194 
195 #endif // SHARE_OOPS_OOPSHIERARCHY_HPP