1 /*
  2  * Copyright (c) 1997, 2022, Oracle and/or its affiliates. All rights reserved.
  3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  4  *
  5  * This code is free software; you can redistribute it and/or modify it
  6  * under the terms of the GNU General Public License version 2 only, as
  7  * published by the Free Software Foundation.
  8  *
  9  * This code is distributed in the hope that it will be useful, but WITHOUT
 10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 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
 13  * accompanied this code).
 14  *
 15  * You should have received a copy of the GNU General Public License version
 16  * 2 along with this work; if not, write to the Free Software Foundation,
 17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 18  *
 19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 20  * or visit www.oracle.com if you need additional information or have any
 21  * questions.
 22  *
 23  */
 24 
 25 #ifndef SHARE_OOPS_KLASS_HPP
 26 #define SHARE_OOPS_KLASS_HPP
 27 
 28 #include "memory/iterator.hpp"
 29 #include "memory/memRegion.hpp"
 30 #include "oops/markWord.hpp"
 31 #include "oops/metadata.hpp"
 32 #include "oops/oop.hpp"
 33 #include "oops/oopHandle.hpp"
 34 #include "utilities/accessFlags.hpp"
 35 #include "utilities/macros.hpp"
 36 #if INCLUDE_JFR
 37 #include "jfr/support/jfrTraceIdExtension.hpp"
 38 #endif
 39 
 40 // Klass Kinds for all subclasses of Klass
 41 enum KlassKind {
 42   InstanceKlassKind,
 43   InstanceRefKlassKind,
 44   InstanceMirrorKlassKind,
 45   InstanceClassLoaderKlassKind,
 46   TypeArrayKlassKind,
 47   ObjArrayKlassKind
 48 };
 49 
 50 const uint KLASS_KIND_COUNT = ObjArrayKlassKind + 1;
 51 
 52 //
 53 // A Klass provides:
 54 //  1: language level class object (method dictionary etc.)
 55 //  2: provide vm dispatch behavior for the object
 56 // Both functions are combined into one C++ class.
 57 
 58 // One reason for the oop/klass dichotomy in the implementation is
 59 // that we don't want a C++ vtbl pointer in every object.  Thus,
 60 // normal oops don't have any virtual functions.  Instead, they
 61 // forward all "virtual" functions to their klass, which does have
 62 // a vtbl and does the C++ dispatch depending on the object's
 63 // actual type.  (See oop.inline.hpp for some of the forwarding code.)
 64 // ALL FUNCTIONS IMPLEMENTING THIS DISPATCH ARE PREFIXED WITH "oop_"!
 65 
 66 // Forward declarations.
 67 template <class T> class Array;
 68 template <class T> class GrowableArray;
 69 class ClassLoaderData;
 70 class fieldDescriptor;
 71 class klassVtable;
 72 class ModuleEntry;
 73 class PackageEntry;
 74 class ParCompactionManager;
 75 class PSPromotionManager;
 76 class vtableEntry;
 77 
 78 class Klass : public Metadata {
 79   friend class VMStructs;
 80   friend class JVMCIVMStructs;
 81  protected:
 82   // If you add a new field that points to any metaspace object, you
 83   // must add this field to Klass::metaspace_pointers_do().
 84 
 85   // note: put frequently-used fields together at start of klass structure
 86   // for better cache behavior (may not make much of a difference but sure won't hurt)
 87   enum { _primary_super_limit = 8 };
 88 
 89   // The "layout helper" is a combined descriptor of object layout.
 90   // For klasses which are neither instance nor array, the value is zero.
 91   //
 92   // For instances, layout helper is a positive number, the instance size.
 93   // This size is already passed through align_object_size and scaled to bytes.
 94   // The low order bit is set if instances of this class cannot be
 95   // allocated using the fastpath.
 96   //
 97   // For arrays, layout helper is a negative number, containing four
 98   // distinct bytes, as follows:
 99   //    MSB:[tag, hsz, ebt, log2(esz)]:LSB
100   // where:
101   //    tag is 0x80 if the elements are oops, 0xC0 if non-oops
102   //    hsz is array header size in bytes (i.e., offset of first element)
103   //    ebt is the BasicType of the elements
104   //    esz is the element size in bytes
105   // This packed word is arranged so as to be quickly unpacked by the
106   // various fast paths that use the various subfields.
107   //
108   // The esz bits can be used directly by a SLL instruction, without masking.
109   //
110   // Note that the array-kind tag looks like 0x00 for instance klasses,
111   // since their length in bytes is always less than 24Mb.
112   //
113   // Final note:  This comes first, immediately after C++ vtable,
114   // because it is frequently queried.
115   jint        _layout_helper;
116 
117   // Klass kind used to resolve the runtime type of the instance.
118   //  - Used to implement devirtualized oop closure dispatching.
119   //  - Various type checking in the JVM
120   const KlassKind _kind;
121 
122   // Processed access flags, for use by Class.getModifiers.
123   jint        _modifier_flags;
124 
125   // The fields _super_check_offset, _secondary_super_cache, _secondary_supers
126   // and _primary_supers all help make fast subtype checks.  See big discussion
127   // in doc/server_compiler/checktype.txt
128   //
129   // Where to look to observe a supertype (it is &_secondary_super_cache for
130   // secondary supers, else is &_primary_supers[depth()].
131   juint       _super_check_offset;
132 
133   // Class name.  Instance classes: java/lang/String, etc.  Array classes: [I,
134   // [Ljava/lang/String;, etc.  Set to zero for all other kinds of classes.
135   Symbol*     _name;
136 
137   // Cache of last observed secondary supertype
138   Klass*      _secondary_super_cache;
139   // Array of all secondary supertypes
140   Array<Klass*>* _secondary_supers;
141   // Ordered list of all primary supertypes
142   Klass*      _primary_supers[_primary_super_limit];
143   // java/lang/Class instance mirroring this class
144   OopHandle   _java_mirror;
145   // Superclass
146   Klass*      _super;
147   // First subclass (NULL if none); _subklass->next_sibling() is next one
148   Klass* volatile _subklass;
149   // Sibling link (or NULL); links all subklasses of a klass
150   Klass* volatile _next_sibling;
151 
152   // All klasses loaded by a class loader are chained through these links
153   Klass*      _next_link;
154 
155   // The VM's representation of the ClassLoader used to load this class.
156   // Provide access the corresponding instance java.lang.ClassLoader.
157   ClassLoaderData* _class_loader_data;
158 
159   int _vtable_len;              // vtable length. This field may be read very often when we
160                                 // have lots of itable dispatches (e.g., lambdas and streams).
161                                 // Keep it away from the beginning of a Klass to avoid cacheline
162                                 // contention that may happen when a nearby object is modified.
163   AccessFlags _access_flags;    // Access flags. The class/interface distinction is stored here.
164 
165   JFR_ONLY(DEFINE_TRACE_ID_FIELD;)
166 
167 private:
168   // This is an index into FileMapHeader::_shared_path_table[], to
169   // associate this class with the JAR file where it's loaded from during
170   // dump time. If a class is not loaded from the shared archive, this field is
171   // -1.
172   jshort _shared_class_path_index;
173 
174 #if INCLUDE_CDS
175   // Flags of the current shared class.
176   u2     _shared_class_flags;
177   enum {
178     _archived_lambda_proxy_is_available    = 1 << 1,
179     _has_value_based_class_annotation      = 1 << 2,
180     _verified_at_dump_time                 = 1 << 3,
181     _has_archived_enum_objs                = 1 << 4,
182     _regenerated                           = 1 << 5
183   };
184 #endif
185 
186   CDS_JAVA_HEAP_ONLY(int _archived_mirror_index;)
187 
188 protected:
189 
190   // Constructor
191   Klass(KlassKind kind);
192   Klass() : _kind(KlassKind(-1)) { assert(DumpSharedSpaces || UseSharedSpaces, "only for cds"); }
193 
194   void* operator new(size_t size, ClassLoaderData* loader_data, size_t word_size, TRAPS) throw();
195 
196  public:
197   int kind() { return _kind; }
198 
199   enum class DefaultsLookupMode { find, skip };
200   enum class OverpassLookupMode { find, skip };
201   enum class StaticLookupMode   { find, skip };
202   enum class PrivateLookupMode  { find, skip };
203 
204   virtual bool is_klass() const { return true; }
205 
206   // super() cannot be InstanceKlass* -- Java arrays are covariant, and _super is used
207   // to implement that. NB: the _super of "[Ljava/lang/Integer;" is "[Ljava/lang/Number;"
208   // If this is not what your code expects, you're probably looking for Klass::java_super().
209   Klass* super() const               { return _super; }
210   void set_super(Klass* k)           { _super = k; }
211 
212   // initializes _super link, _primary_supers & _secondary_supers arrays
213   void initialize_supers(Klass* k, Array<InstanceKlass*>* transitive_interfaces, TRAPS);
214 
215   // klass-specific helper for initializing _secondary_supers
216   virtual GrowableArray<Klass*>* compute_secondary_supers(int num_extra_slots,
217                                                           Array<InstanceKlass*>* transitive_interfaces);
218 
219   // java_super is the Java-level super type as specified by Class.getSuperClass.
220   virtual InstanceKlass* java_super() const  { return NULL; }
221 
222   juint    super_check_offset() const  { return _super_check_offset; }
223   void set_super_check_offset(juint o) { _super_check_offset = o; }
224 
225   Klass* secondary_super_cache() const     { return _secondary_super_cache; }
226   void set_secondary_super_cache(Klass* k) { _secondary_super_cache = k; }
227 
228   Array<Klass*>* secondary_supers() const { return _secondary_supers; }
229   void set_secondary_supers(Array<Klass*>* k) { _secondary_supers = k; }
230 
231   // Return the element of the _super chain of the given depth.
232   // If there is no such element, return either NULL or this.
233   Klass* primary_super_of_depth(juint i) const {
234     assert(i < primary_super_limit(), "oob");
235     Klass* super = _primary_supers[i];
236     assert(super == NULL || super->super_depth() == i, "correct display");
237     return super;
238   }
239 
240   // Can this klass be a primary super?  False for interfaces and arrays of
241   // interfaces.  False also for arrays or classes with long super chains.
242   bool can_be_primary_super() const {
243     const juint secondary_offset = in_bytes(secondary_super_cache_offset());
244     return super_check_offset() != secondary_offset;
245   }
246   virtual bool can_be_primary_super_slow() const;
247 
248   // Returns number of primary supers; may be a number in the inclusive range [0, primary_super_limit].
249   juint super_depth() const {
250     if (!can_be_primary_super()) {
251       return primary_super_limit();
252     } else {
253       juint d = (super_check_offset() - in_bytes(primary_supers_offset())) / sizeof(Klass*);
254       assert(d < primary_super_limit(), "oob");
255       assert(_primary_supers[d] == this, "proper init");
256       return d;
257     }
258   }
259 
260   // java mirror
261   oop java_mirror() const;
262   oop java_mirror_no_keepalive() const;
263   void set_java_mirror(Handle m);
264 
265   oop archived_java_mirror() NOT_CDS_JAVA_HEAP_RETURN_(NULL);
266   void set_archived_java_mirror(oop m) NOT_CDS_JAVA_HEAP_RETURN;
267 
268   // Temporary mirror switch used by RedefineClasses
269   void replace_java_mirror(oop mirror);
270 
271   // Set java mirror OopHandle to NULL for CDS
272   // This leaves the OopHandle in the CLD, but that's ok, you can't release them.
273   void clear_java_mirror_handle() { _java_mirror = OopHandle(); }
274 
275   // modifier flags
276   jint modifier_flags() const          { return _modifier_flags; }
277   void set_modifier_flags(jint flags)  { _modifier_flags = flags; }
278 
279   // size helper
280   int layout_helper() const            { return _layout_helper; }
281   void set_layout_helper(int lh)       { _layout_helper = lh; }
282 
283   // Note: for instances layout_helper() may include padding.
284   // Use InstanceKlass::contains_field_offset to classify field offsets.
285 
286   // sub/superklass links
287   Klass* subklass(bool log = false) const;
288   Klass* next_sibling(bool log = false) const;
289 
290   InstanceKlass* superklass() const;
291   void append_to_sibling_list();           // add newly created receiver to superklass' subklass list
292 
293   void set_next_link(Klass* k) { _next_link = k; }
294   Klass* next_link() const { return _next_link; }   // The next klass defined by the class loader.
295   Klass** next_link_addr() { return &_next_link; }
296 
297   // class loader data
298   ClassLoaderData* class_loader_data() const               { return _class_loader_data; }
299   void set_class_loader_data(ClassLoaderData* loader_data) {  _class_loader_data = loader_data; }
300 
301   int shared_classpath_index() const   {
302     return _shared_class_path_index;
303   };
304 
305   void set_shared_classpath_index(int index) {
306     _shared_class_path_index = index;
307   };
308 
309   bool has_archived_mirror_index() const {
310     CDS_JAVA_HEAP_ONLY(return _archived_mirror_index >= 0;)
311     NOT_CDS_JAVA_HEAP(return false);
312   }
313 
314   void clear_archived_mirror_index() NOT_CDS_JAVA_HEAP_RETURN;
315 
316   void set_lambda_proxy_is_available() {
317     CDS_ONLY(_shared_class_flags |= _archived_lambda_proxy_is_available;)
318   }
319   void clear_lambda_proxy_is_available() {
320     CDS_ONLY(_shared_class_flags &= ~_archived_lambda_proxy_is_available;)
321   }
322   bool lambda_proxy_is_available() const {
323     CDS_ONLY(return (_shared_class_flags & _archived_lambda_proxy_is_available) != 0;)
324     NOT_CDS(return false;)
325   }
326 
327   void set_has_value_based_class_annotation() {
328     CDS_ONLY(_shared_class_flags |= _has_value_based_class_annotation;)
329   }
330   void clear_has_value_based_class_annotation() {
331     CDS_ONLY(_shared_class_flags &= ~_has_value_based_class_annotation;)
332   }
333   bool has_value_based_class_annotation() const {
334     CDS_ONLY(return (_shared_class_flags & _has_value_based_class_annotation) != 0;)
335     NOT_CDS(return false;)
336   }
337 
338   void set_verified_at_dump_time() {
339     CDS_ONLY(_shared_class_flags |= _verified_at_dump_time;)
340   }
341   bool verified_at_dump_time() const {
342     CDS_ONLY(return (_shared_class_flags & _verified_at_dump_time) != 0;)
343     NOT_CDS(return false;)
344   }
345 
346   void set_has_archived_enum_objs() {
347     CDS_ONLY(_shared_class_flags |= _has_archived_enum_objs;)
348   }
349   bool has_archived_enum_objs() const {
350     CDS_ONLY(return (_shared_class_flags & _has_archived_enum_objs) != 0;)
351     NOT_CDS(return false;)
352   }
353 
354   void set_regenerated() {
355     CDS_ONLY(_shared_class_flags |= _regenerated;)
356   }
357   bool is_regenerated() const {
358     CDS_ONLY(return (_shared_class_flags & _regenerated) != 0;)
359     NOT_CDS(return false;)
360   }
361 
362   // Obtain the module or package for this class
363   virtual ModuleEntry* module() const = 0;
364   virtual PackageEntry* package() const = 0;
365 
366  protected:                                // internal accessors
367   void     set_subklass(Klass* s);
368   void     set_next_sibling(Klass* s);
369 
370  public:
371 
372   // Compiler support
373   static ByteSize super_offset()                 { return in_ByteSize(offset_of(Klass, _super)); }
374   static ByteSize super_check_offset_offset()    { return in_ByteSize(offset_of(Klass, _super_check_offset)); }
375   static ByteSize primary_supers_offset()        { return in_ByteSize(offset_of(Klass, _primary_supers)); }
376   static ByteSize secondary_super_cache_offset() { return in_ByteSize(offset_of(Klass, _secondary_super_cache)); }
377   static ByteSize secondary_supers_offset()      { return in_ByteSize(offset_of(Klass, _secondary_supers)); }
378   static ByteSize java_mirror_offset()           { return in_ByteSize(offset_of(Klass, _java_mirror)); }
379   static ByteSize class_loader_data_offset()     { return in_ByteSize(offset_of(Klass, _class_loader_data)); }
380   static ByteSize modifier_flags_offset()        { return in_ByteSize(offset_of(Klass, _modifier_flags)); }
381   static ByteSize layout_helper_offset()         { return in_ByteSize(offset_of(Klass, _layout_helper)); }
382   static ByteSize access_flags_offset()          { return in_ByteSize(offset_of(Klass, _access_flags)); }
383 
384   // Unpacking layout_helper:
385   static const int _lh_neutral_value           = 0;  // neutral non-array non-instance value
386   static const int _lh_instance_slow_path_bit  = 0x01;
387   static const int _lh_log2_element_size_shift = BitsPerByte*0;
388   static const int _lh_log2_element_size_mask  = BitsPerLong-1;
389   static const int _lh_element_type_shift      = BitsPerByte*1;
390   static const int _lh_element_type_mask       = right_n_bits(BitsPerByte);  // shifted mask
391   static const int _lh_header_size_shift       = BitsPerByte*2;
392   static const int _lh_header_size_mask        = right_n_bits(BitsPerByte);  // shifted mask
393   static const int _lh_array_tag_bits          = 2;
394   static const int _lh_array_tag_shift         = BitsPerInt - _lh_array_tag_bits;
395   static const int _lh_array_tag_obj_value     = ~0x01;   // 0x80000000 >> 30
396 
397   static const unsigned int _lh_array_tag_type_value = 0Xffffffff; // ~0x00,  // 0xC0000000 >> 30
398 
399   static int layout_helper_size_in_bytes(jint lh) {
400     assert(lh > (jint)_lh_neutral_value, "must be instance");
401     return (int) lh & ~_lh_instance_slow_path_bit;
402   }
403   static bool layout_helper_needs_slow_path(jint lh) {
404     assert(lh > (jint)_lh_neutral_value, "must be instance");
405     return (lh & _lh_instance_slow_path_bit) != 0;
406   }
407   static bool layout_helper_is_instance(jint lh) {
408     return (jint)lh > (jint)_lh_neutral_value;
409   }
410   static bool layout_helper_is_array(jint lh) {
411     return (jint)lh < (jint)_lh_neutral_value;
412   }
413   static bool layout_helper_is_typeArray(jint lh) {
414     // _lh_array_tag_type_value == (lh >> _lh_array_tag_shift);
415     return (juint)lh >= (juint)(_lh_array_tag_type_value << _lh_array_tag_shift);
416   }
417   static bool layout_helper_is_objArray(jint lh) {
418     // _lh_array_tag_obj_value == (lh >> _lh_array_tag_shift);
419     return (jint)lh < (jint)(_lh_array_tag_type_value << _lh_array_tag_shift);
420   }
421   static int layout_helper_header_size(jint lh) {
422     assert(lh < (jint)_lh_neutral_value, "must be array");
423     int hsize = (lh >> _lh_header_size_shift) & _lh_header_size_mask;
424     assert(hsize > 0 && hsize < (int)sizeof(oopDesc)*3, "sanity");
425     return hsize;
426   }
427   static BasicType layout_helper_element_type(jint lh) {
428     assert(lh < (jint)_lh_neutral_value, "must be array");
429     int btvalue = (lh >> _lh_element_type_shift) & _lh_element_type_mask;
430     assert(btvalue >= T_BOOLEAN && btvalue <= T_OBJECT, "sanity");
431     return (BasicType) btvalue;
432   }
433 
434   // Want a pattern to quickly diff against layout header in register
435   // find something less clever!
436   static int layout_helper_boolean_diffbit() {
437     jint zlh = array_layout_helper(T_BOOLEAN);
438     jint blh = array_layout_helper(T_BYTE);
439     assert(zlh != blh, "array layout helpers must differ");
440     int diffbit = 1;
441     while ((diffbit & (zlh ^ blh)) == 0 && (diffbit & zlh) == 0) {
442       diffbit <<= 1;
443       assert(diffbit != 0, "make sure T_BOOLEAN has a different bit than T_BYTE");
444     }
445     return diffbit;
446   }
447 
448   static int layout_helper_log2_element_size(jint lh) {
449     assert(lh < (jint)_lh_neutral_value, "must be array");
450     int l2esz = (lh >> _lh_log2_element_size_shift) & _lh_log2_element_size_mask;
451     assert(l2esz <= LogBytesPerLong,
452            "sanity. l2esz: 0x%x for lh: 0x%x", (uint)l2esz, (uint)lh);
453     return l2esz;
454   }
455   static jint array_layout_helper(jint tag, int hsize, BasicType etype, int log2_esize) {
456     return (tag        << _lh_array_tag_shift)
457       |    (hsize      << _lh_header_size_shift)
458       |    ((int)etype << _lh_element_type_shift)
459       |    (log2_esize << _lh_log2_element_size_shift);
460   }
461   static jint instance_layout_helper(jint size, bool slow_path_flag) {
462     return (size << LogBytesPerWord)
463       |    (slow_path_flag ? _lh_instance_slow_path_bit : 0);
464   }
465   static int layout_helper_to_size_helper(jint lh) {
466     assert(lh > (jint)_lh_neutral_value, "must be instance");
467     // Note that the following expression discards _lh_instance_slow_path_bit.
468     return lh >> LogBytesPerWord;
469   }
470   // Out-of-line version computes everything based on the etype:
471   static jint array_layout_helper(BasicType etype);
472 
473   // What is the maximum number of primary superclasses any klass can have?
474   static juint primary_super_limit()         { return _primary_super_limit; }
475 
476   // vtables
477   klassVtable vtable() const;
478   int vtable_length() const { return _vtable_len; }
479 
480   // subclass check
481   bool is_subclass_of(const Klass* k) const;
482   // subtype check: true if is_subclass_of, or if k is interface and receiver implements it
483   bool is_subtype_of(Klass* k) const {
484     juint    off = k->super_check_offset();
485     Klass* sup = *(Klass**)( (address)this + off );
486     const juint secondary_offset = in_bytes(secondary_super_cache_offset());
487     if (sup == k) {
488       return true;
489     } else if (off != secondary_offset) {
490       return false;
491     } else {
492       return search_secondary_supers(k);
493     }
494   }
495 
496   bool search_secondary_supers(Klass* k) const;
497 
498   // Find LCA in class hierarchy
499   Klass *LCA( Klass *k );
500 
501   // Check whether reflection/jni/jvm code is allowed to instantiate this class;
502   // if not, throw either an Error or an Exception.
503   virtual void check_valid_for_instantiation(bool throwError, TRAPS);
504 
505   // array copying
506   virtual void  copy_array(arrayOop s, int src_pos, arrayOop d, int dst_pos, int length, TRAPS);
507 
508   // tells if the class should be initialized
509   virtual bool should_be_initialized() const    { return false; }
510   // initializes the klass
511   virtual void initialize(TRAPS);
512   virtual Klass* find_field(Symbol* name, Symbol* signature, fieldDescriptor* fd) const;
513   virtual Method* uncached_lookup_method(const Symbol* name, const Symbol* signature,
514                                          OverpassLookupMode overpass_mode,
515                                          PrivateLookupMode = PrivateLookupMode::find) const;
516  public:
517   Method* lookup_method(const Symbol* name, const Symbol* signature) const {
518     return uncached_lookup_method(name, signature, OverpassLookupMode::find);
519   }
520 
521   // array class with specific rank
522   virtual Klass* array_klass(int rank, TRAPS) = 0;
523 
524   // array class with this klass as element type
525   virtual Klass* array_klass(TRAPS) = 0;
526 
527   // These will return NULL instead of allocating on the heap:
528   virtual Klass* array_klass_or_null(int rank) = 0;
529   virtual Klass* array_klass_or_null() = 0;
530 
531   virtual oop protection_domain() const = 0;
532 
533   oop class_loader() const;
534 
535   inline oop klass_holder() const;
536 
537  protected:
538 
539   // Error handling when length > max_length or length < 0
540   static void check_array_allocation_length(int length, int max_length, TRAPS);
541 
542   void set_vtable_length(int len) { _vtable_len= len; }
543 
544   vtableEntry* start_of_vtable() const;
545   void restore_unshareable_info(ClassLoaderData* loader_data, Handle protection_domain, TRAPS);
546  public:
547   Method* method_at_vtable(int index);
548 
549   static ByteSize vtable_start_offset();
550   static ByteSize vtable_length_offset() {
551     return byte_offset_of(Klass, _vtable_len);
552   }
553 
554   // CDS support - remove and restore oops from metadata. Oops are not shared.
555   virtual void remove_unshareable_info();
556   virtual void remove_java_mirror();
557 
558   bool is_unshareable_info_restored() const {
559     assert(is_shared(), "use this for shared classes only");
560     if (has_archived_mirror_index()) {
561       // _java_mirror is not a valid OopHandle but rather an encoded reference in the shared heap
562       return false;
563     } else if (_java_mirror.ptr_raw() == NULL) {
564       return false;
565     } else {
566       return true;
567     }
568   }
569 
570  public:
571   // ALL FUNCTIONS BELOW THIS POINT ARE DISPATCHED FROM AN OOP
572   // These functions describe behavior for the oop not the KLASS.
573 
574   // actual oop size of obj in memory in word size.
575   virtual size_t oop_size(oop obj) const = 0;
576 
577   // Size of klass in word size.
578   virtual int size() const = 0;
579 
580   // Returns the Java name for a class (Resource allocated)
581   // For arrays, this returns the name of the element with a leading '['.
582   // For classes, this returns the name with the package separators
583   //     turned into '.'s.
584   const char* external_name() const;
585   // Returns the name for a class (Resource allocated) as the class
586   // would appear in a signature.
587   // For arrays, this returns the name of the element with a leading '['.
588   // For classes, this returns the name with a leading 'L' and a trailing ';'
589   //     and the package separators as '/'.
590   virtual const char* signature_name() const;
591 
592   const char* joint_in_module_of_loader(const Klass* class2, bool include_parent_loader = false) const;
593   const char* class_in_module_of_loader(bool use_are = false, bool include_parent_loader = false) const;
594 
595   // Returns "interface", "abstract class" or "class".
596   const char* external_kind() const;
597 
598   // type testing operations
599 #ifdef ASSERT
600  protected:
601   virtual bool is_instance_klass_slow()     const { return false; }
602   virtual bool is_array_klass_slow()        const { return false; }
603   virtual bool is_objArray_klass_slow()     const { return false; }
604   virtual bool is_typeArray_klass_slow()    const { return false; }
605 #endif // ASSERT
606  public:
607 
608   // Fast non-virtual versions
609   #ifndef ASSERT
610   #define assert_same_query(xval, xcheck) xval
611   #else
612  private:
613   static bool assert_same_query(bool xval, bool xslow) {
614     assert(xval == xslow, "slow and fast queries agree");
615     return xval;
616   }
617  public:
618   #endif
619 
620   bool is_instance_klass()              const { return assert_same_query(_kind <= InstanceClassLoaderKlassKind, is_instance_klass_slow()); }
621   // Other is anything that is not one of the more specialized kinds of InstanceKlass.
622   bool is_other_instance_klass()        const { return _kind == InstanceKlassKind; }
623   bool is_reference_instance_klass()    const { return _kind == InstanceRefKlassKind; }
624   bool is_mirror_instance_klass()       const { return _kind == InstanceMirrorKlassKind; }
625   bool is_class_loader_instance_klass() const { return _kind == InstanceClassLoaderKlassKind; }
626   bool is_array_klass()                 const { return assert_same_query( _kind >= TypeArrayKlassKind, is_array_klass_slow()); }
627   bool is_objArray_klass()              const { return assert_same_query( _kind == ObjArrayKlassKind,  is_objArray_klass_slow()); }
628   bool is_typeArray_klass()             const { return assert_same_query( _kind == TypeArrayKlassKind, is_typeArray_klass_slow()); }
629   #undef assert_same_query
630 
631   // Access flags
632   AccessFlags access_flags() const         { return _access_flags;  }
633   void set_access_flags(AccessFlags flags) { _access_flags = flags; }
634 
635   bool is_public() const                { return _access_flags.is_public(); }
636   bool is_final() const                 { return _access_flags.is_final(); }
637   bool is_interface() const             { return _access_flags.is_interface(); }
638   bool is_abstract() const              { return _access_flags.is_abstract(); }
639   bool is_super() const                 { return _access_flags.is_super(); }
640   bool is_synthetic() const             { return _access_flags.is_synthetic(); }
641   void set_is_synthetic()               { _access_flags.set_is_synthetic(); }
642   bool has_finalizer() const            { return _access_flags.has_finalizer(); }
643   bool has_final_method() const         { return _access_flags.has_final_method(); }
644   void set_has_finalizer()              { _access_flags.set_has_finalizer(); }
645   void set_has_final_method()           { _access_flags.set_has_final_method(); }
646   bool has_vanilla_constructor() const  { return _access_flags.has_vanilla_constructor(); }
647   void set_has_vanilla_constructor()    { _access_flags.set_has_vanilla_constructor(); }
648   bool has_miranda_methods () const     { return access_flags().has_miranda_methods(); }
649   void set_has_miranda_methods()        { _access_flags.set_has_miranda_methods(); }
650   bool is_shared() const                { return access_flags().is_shared_class(); } // shadows MetaspaceObj::is_shared)()
651   void set_is_shared()                  { _access_flags.set_is_shared_class(); }
652   bool is_hidden() const                { return access_flags().is_hidden_class(); }
653   void set_is_hidden()                  { _access_flags.set_is_hidden_class(); }
654   bool is_value_based()                 { return _access_flags.is_value_based_class(); }
655   void set_is_value_based()             { _access_flags.set_is_value_based_class(); }
656 
657   inline bool is_non_strong_hidden() const;
658 
659   bool is_cloneable() const;
660   void set_is_cloneable();
661 
662   JFR_ONLY(DEFINE_TRACE_ID_METHODS;)
663 
664   virtual void metaspace_pointers_do(MetaspaceClosure* iter);
665   virtual MetaspaceObj::Type type() const { return ClassType; }
666 
667   inline bool is_loader_alive() const;
668 
669   void clean_subklass();
670 
671   static void clean_weak_klass_links(bool unloading_occurred, bool clean_alive_klasses = true);
672   static void clean_subklass_tree() {
673     clean_weak_klass_links(/*unloading_occurred*/ true , /* clean_alive_klasses */ false);
674   }
675 
676   // Return self, except for abstract classes with exactly 1
677   // implementor.  Then return the 1 concrete implementation.
678   Klass *up_cast_abstract();
679 
680   // klass name
681   Symbol* name() const                   { return _name; }
682   void set_name(Symbol* n);
683 
684   virtual void release_C_heap_structures(bool release_constant_pool = true);
685 
686  public:
687   virtual jint compute_modifier_flags() const = 0;
688 
689   // JVMTI support
690   virtual jint jvmti_class_status() const;
691 
692   // Printing
693   virtual void print_on(outputStream* st) const;
694 
695   virtual void oop_print_value_on(oop obj, outputStream* st);
696   virtual void oop_print_on      (oop obj, outputStream* st);
697 
698   virtual const char* internal_name() const = 0;
699 
700   // Verification
701   virtual void verify_on(outputStream* st);
702   void verify() { verify_on(tty); }
703 
704 #ifndef PRODUCT
705   bool verify_vtable_index(int index);
706 #endif
707 
708   virtual void oop_verify_on(oop obj, outputStream* st);
709 
710   // for error reporting
711   static bool is_valid(Klass* k);
712 };
713 
714 #endif // SHARE_OOPS_KLASS_HPP