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   InstanceStackChunkKlassKind,
 47   TypeArrayKlassKind,
 48   ObjArrayKlassKind
 49 };
 50 
 51 const uint KLASS_KIND_COUNT = ObjArrayKlassKind + 1;
 52 
 53 //
 54 // A Klass provides:
 55 //  1: language level class object (method dictionary etc.)
 56 //  2: provide vm dispatch behavior for the object
 57 // Both functions are combined into one C++ class.
 58 
 59 // One reason for the oop/klass dichotomy in the implementation is
 60 // that we don't want a C++ vtbl pointer in every object.  Thus,
 61 // normal oops don't have any virtual functions.  Instead, they
 62 // forward all "virtual" functions to their klass, which does have
 63 // a vtbl and does the C++ dispatch depending on the object's
 64 // actual type.  (See oop.inline.hpp for some of the forwarding code.)
 65 // ALL FUNCTIONS IMPLEMENTING THIS DISPATCH ARE PREFIXED WITH "oop_"!
 66 
 67 // Forward declarations.
 68 template <class T> class Array;
 69 template <class T> class GrowableArray;
 70 class ClassLoaderData;
 71 class fieldDescriptor;
 72 class klassVtable;
 73 class ModuleEntry;
 74 class PackageEntry;
 75 class ParCompactionManager;
 76 class PSPromotionManager;
 77 class vtableEntry;
 78 
 79 class Klass : public Metadata {
 80   friend class VMStructs;
 81   friend class JVMCIVMStructs;
 82  protected:
 83   // If you add a new field that points to any metaspace object, you
 84   // must add this field to Klass::metaspace_pointers_do().
 85 
 86   // note: put frequently-used fields together at start of klass structure
 87   // for better cache behavior (may not make much of a difference but sure won't hurt)
 88   enum { _primary_super_limit = 8 };
 89 
 90   // The "layout helper" is a combined descriptor of object layout.
 91   // For klasses which are neither instance nor array, the value is zero.
 92   //
 93   // For instances, layout helper is a positive number, the instance size.
 94   // This size is already passed through align_object_size and scaled to bytes.
 95   // The low order bit is set if instances of this class cannot be
 96   // allocated using the fastpath.
 97   //
 98   // For arrays, layout helper is a negative number, containing four
 99   // distinct bytes, as follows:
100   //    MSB:[tag, hsz, ebt, log2(esz)]:LSB
101   // where:
102   //    tag is 0x80 if the elements are oops, 0xC0 if non-oops
103   //    hsz is array header size in bytes (i.e., offset of first element)
104   //    ebt is the BasicType of the elements
105   //    esz is the element size in bytes
106   // This packed word is arranged so as to be quickly unpacked by the
107   // various fast paths that use the various subfields.
108   //
109   // The esz bits can be used directly by a SLL instruction, without masking.
110   //
111   // Note that the array-kind tag looks like 0x00 for instance klasses,
112   // since their length in bytes is always less than 24Mb.
113   //
114   // Final note:  This comes first, immediately after C++ vtable,
115   // because it is frequently queried.
116   jint        _layout_helper;
117 
118   // Klass kind used to resolve the runtime type of the instance.
119   //  - Used to implement devirtualized oop closure dispatching.
120   //  - Various type checking in the JVM
121   const KlassKind _kind;
122 
123   // Processed access flags, for use by Class.getModifiers.
124   jint        _modifier_flags;
125 
126   // The fields _super_check_offset, _secondary_super_cache, _secondary_supers
127   // and _primary_supers all help make fast subtype checks.  See big discussion
128   // in doc/server_compiler/checktype.txt
129   //
130   // Where to look to observe a supertype (it is &_secondary_super_cache for
131   // secondary supers, else is &_primary_supers[depth()].
132   juint       _super_check_offset;
133 
134   // Class name.  Instance classes: java/lang/String, etc.  Array classes: [I,
135   // [Ljava/lang/String;, etc.  Set to zero for all other kinds of classes.
136   Symbol*     _name;
137 
138   // Cache of last observed secondary supertype
139   Klass*      _secondary_super_cache;
140   // Array of all secondary supertypes
141   Array<Klass*>* _secondary_supers;
142   // Ordered list of all primary supertypes
143   Klass*      _primary_supers[_primary_super_limit];
144   // java/lang/Class instance mirroring this class
145   OopHandle   _java_mirror;
146   // Superclass
147   Klass*      _super;
148   // First subclass (NULL if none); _subklass->next_sibling() is next one
149   Klass* volatile _subklass;
150   // Sibling link (or NULL); links all subklasses of a klass
151   Klass* volatile _next_sibling;
152 
153   // All klasses loaded by a class loader are chained through these links
154   Klass*      _next_link;
155 
156   // The VM's representation of the ClassLoader used to load this class.
157   // Provide access the corresponding instance java.lang.ClassLoader.
158   ClassLoaderData* _class_loader_data;
159 
160   int _vtable_len;              // vtable length. This field may be read very often when we
161                                 // have lots of itable dispatches (e.g., lambdas and streams).
162                                 // Keep it away from the beginning of a Klass to avoid cacheline
163                                 // contention that may happen when a nearby object is modified.
164   AccessFlags _access_flags;    // Access flags. The class/interface distinction is stored here.
165 
166   JFR_ONLY(DEFINE_TRACE_ID_FIELD;)
167 
168   markWord _prototype_header;   // Used to initialize objects' header
169 
170 private:
171   // This is an index into FileMapHeader::_shared_path_table[], to
172   // associate this class with the JAR file where it's loaded from during
173   // dump time. If a class is not loaded from the shared archive, this field is
174   // -1.
175   jshort _shared_class_path_index;
176 
177 #if INCLUDE_CDS
178   // Various attributes for shared classes. Should be zero for a non-shared class.
179   u2     _shared_class_flags;
180   enum CDSSharedClassFlags {
181     _archived_lambda_proxy_is_available    = 1 << 1,
182     _has_value_based_class_annotation      = 1 << 2,
183     _verified_at_dump_time                 = 1 << 3,
184     _has_archived_enum_objs                = 1 << 4,
185     // This class was not loaded from a classfile in the module image
186     // or classpath.
187     _is_generated_shared_class             = 1 << 5
188   };
189 #endif
190 
191   CDS_JAVA_HEAP_ONLY(int _archived_mirror_index;)
192 
193 protected:
194 
195   // Constructor
196   Klass(KlassKind kind);
197   Klass() : _kind(KlassKind(-1)) { assert(DumpSharedSpaces || UseSharedSpaces, "only for cds"); }
198 
199   void* operator new(size_t size, ClassLoaderData* loader_data, size_t word_size, TRAPS) throw();
200 
201  public:
202   int kind() { return _kind; }
203 
204   enum class DefaultsLookupMode { find, skip };
205   enum class OverpassLookupMode { find, skip };
206   enum class StaticLookupMode   { find, skip };
207   enum class PrivateLookupMode  { find, skip };
208 
209   virtual bool is_klass() const { return true; }
210 
211   // super() cannot be InstanceKlass* -- Java arrays are covariant, and _super is used
212   // to implement that. NB: the _super of "[Ljava/lang/Integer;" is "[Ljava/lang/Number;"
213   // If this is not what your code expects, you're probably looking for Klass::java_super().
214   Klass* super() const               { return _super; }
215   void set_super(Klass* k)           { _super = k; }
216 
217   // initializes _super link, _primary_supers & _secondary_supers arrays
218   void initialize_supers(Klass* k, Array<InstanceKlass*>* transitive_interfaces, TRAPS);
219 
220   // klass-specific helper for initializing _secondary_supers
221   virtual GrowableArray<Klass*>* compute_secondary_supers(int num_extra_slots,
222                                                           Array<InstanceKlass*>* transitive_interfaces);
223 
224   // java_super is the Java-level super type as specified by Class.getSuperClass.
225   virtual InstanceKlass* java_super() const  { return NULL; }
226 
227   juint    super_check_offset() const  { return _super_check_offset; }
228   void set_super_check_offset(juint o) { _super_check_offset = o; }
229 
230   Klass* secondary_super_cache() const     { return _secondary_super_cache; }
231   void set_secondary_super_cache(Klass* k) { _secondary_super_cache = k; }
232 
233   Array<Klass*>* secondary_supers() const { return _secondary_supers; }
234   void set_secondary_supers(Array<Klass*>* k) { _secondary_supers = k; }
235 
236   // Return the element of the _super chain of the given depth.
237   // If there is no such element, return either NULL or this.
238   Klass* primary_super_of_depth(juint i) const {
239     assert(i < primary_super_limit(), "oob");
240     Klass* super = _primary_supers[i];
241     assert(super == NULL || super->super_depth() == i, "correct display");
242     return super;
243   }
244 
245   // Can this klass be a primary super?  False for interfaces and arrays of
246   // interfaces.  False also for arrays or classes with long super chains.
247   bool can_be_primary_super() const {
248     const juint secondary_offset = in_bytes(secondary_super_cache_offset());
249     return super_check_offset() != secondary_offset;
250   }
251   virtual bool can_be_primary_super_slow() const;
252 
253   // Returns number of primary supers; may be a number in the inclusive range [0, primary_super_limit].
254   juint super_depth() const {
255     if (!can_be_primary_super()) {
256       return primary_super_limit();
257     } else {
258       juint d = (super_check_offset() - in_bytes(primary_supers_offset())) / sizeof(Klass*);
259       assert(d < primary_super_limit(), "oob");
260       assert(_primary_supers[d] == this, "proper init");
261       return d;
262     }
263   }
264 
265   // java mirror
266   oop java_mirror() const;
267   oop java_mirror_no_keepalive() const;
268   void set_java_mirror(Handle m);
269 
270   oop archived_java_mirror() NOT_CDS_JAVA_HEAP_RETURN_(NULL);
271   void set_archived_java_mirror(oop m) NOT_CDS_JAVA_HEAP_RETURN;
272 
273   // Temporary mirror switch used by RedefineClasses
274   void replace_java_mirror(oop mirror);
275 
276   // Set java mirror OopHandle to NULL for CDS
277   // This leaves the OopHandle in the CLD, but that's ok, you can't release them.
278   void clear_java_mirror_handle() { _java_mirror = OopHandle(); }
279 
280   // modifier flags
281   jint modifier_flags() const          { return _modifier_flags; }
282   void set_modifier_flags(jint flags)  { _modifier_flags = flags; }
283 
284   // size helper
285   int layout_helper() const            { return _layout_helper; }
286   void set_layout_helper(int lh)       { _layout_helper = lh; }
287 
288   // Note: for instances layout_helper() may include padding.
289   // Use InstanceKlass::contains_field_offset to classify field offsets.
290 
291   // sub/superklass links
292   Klass* subklass(bool log = false) const;
293   Klass* next_sibling(bool log = false) const;
294 
295   InstanceKlass* superklass() const;
296   void append_to_sibling_list();           // add newly created receiver to superklass' subklass list
297 
298   void set_next_link(Klass* k) { _next_link = k; }
299   Klass* next_link() const { return _next_link; }   // The next klass defined by the class loader.
300   Klass** next_link_addr() { return &_next_link; }
301 
302   // class loader data
303   ClassLoaderData* class_loader_data() const               { return _class_loader_data; }
304   void set_class_loader_data(ClassLoaderData* loader_data) {  _class_loader_data = loader_data; }
305 
306   int shared_classpath_index() const   {
307     return _shared_class_path_index;
308   };
309 
310   void set_shared_classpath_index(int index) {
311     _shared_class_path_index = index;
312   };
313 
314   bool has_archived_mirror_index() const {
315     CDS_JAVA_HEAP_ONLY(return _archived_mirror_index >= 0;)
316     NOT_CDS_JAVA_HEAP(return false);
317   }
318 
319   void clear_archived_mirror_index() NOT_CDS_JAVA_HEAP_RETURN;
320 
321   void set_lambda_proxy_is_available() {
322     CDS_ONLY(_shared_class_flags |= _archived_lambda_proxy_is_available;)
323   }
324   void clear_lambda_proxy_is_available() {
325     CDS_ONLY(_shared_class_flags &= ~_archived_lambda_proxy_is_available;)
326   }
327   bool lambda_proxy_is_available() const {
328     CDS_ONLY(return (_shared_class_flags & _archived_lambda_proxy_is_available) != 0;)
329     NOT_CDS(return false;)
330   }
331 
332   void set_has_value_based_class_annotation() {
333     CDS_ONLY(_shared_class_flags |= _has_value_based_class_annotation;)
334   }
335   void clear_has_value_based_class_annotation() {
336     CDS_ONLY(_shared_class_flags &= ~_has_value_based_class_annotation;)
337   }
338   bool has_value_based_class_annotation() const {
339     CDS_ONLY(return (_shared_class_flags & _has_value_based_class_annotation) != 0;)
340     NOT_CDS(return false;)
341   }
342 
343   void set_verified_at_dump_time() {
344     CDS_ONLY(_shared_class_flags |= _verified_at_dump_time;)
345   }
346   bool verified_at_dump_time() const {
347     CDS_ONLY(return (_shared_class_flags & _verified_at_dump_time) != 0;)
348     NOT_CDS(return false;)
349   }
350 
351   void set_has_archived_enum_objs() {
352     CDS_ONLY(_shared_class_flags |= _has_archived_enum_objs;)
353   }
354   bool has_archived_enum_objs() const {
355     CDS_ONLY(return (_shared_class_flags & _has_archived_enum_objs) != 0;)
356     NOT_CDS(return false;)
357   }
358 
359   void set_is_generated_shared_class() {
360     CDS_ONLY(_shared_class_flags |= _is_generated_shared_class;)
361   }
362   bool is_generated_shared_class() const {
363     CDS_ONLY(return (_shared_class_flags & _is_generated_shared_class) != 0;)
364     NOT_CDS(return false;)
365   }
366 
367   // Obtain the module or package for this class
368   virtual ModuleEntry* module() const = 0;
369   virtual PackageEntry* package() const = 0;
370 
371  protected:                                // internal accessors
372   void     set_subklass(Klass* s);
373   void     set_next_sibling(Klass* s);
374 
375  public:
376 
377   // Compiler support
378   static ByteSize super_offset()                 { return in_ByteSize(offset_of(Klass, _super)); }
379   static ByteSize super_check_offset_offset()    { return in_ByteSize(offset_of(Klass, _super_check_offset)); }
380   static ByteSize primary_supers_offset()        { return in_ByteSize(offset_of(Klass, _primary_supers)); }
381   static ByteSize secondary_super_cache_offset() { return in_ByteSize(offset_of(Klass, _secondary_super_cache)); }
382   static ByteSize secondary_supers_offset()      { return in_ByteSize(offset_of(Klass, _secondary_supers)); }
383   static ByteSize java_mirror_offset()           { return in_ByteSize(offset_of(Klass, _java_mirror)); }
384   static ByteSize class_loader_data_offset()     { return in_ByteSize(offset_of(Klass, _class_loader_data)); }
385   static ByteSize modifier_flags_offset()        { return in_ByteSize(offset_of(Klass, _modifier_flags)); }
386   static ByteSize layout_helper_offset()         { return in_ByteSize(offset_of(Klass, _layout_helper)); }
387   static ByteSize access_flags_offset()          { return in_ByteSize(offset_of(Klass, _access_flags)); }
388 
389   // Unpacking layout_helper:
390   static const int _lh_neutral_value           = 0;  // neutral non-array non-instance value
391   static const int _lh_instance_slow_path_bit  = 0x01;
392   static const int _lh_log2_element_size_shift = BitsPerByte*0;
393   static const int _lh_log2_element_size_mask  = BitsPerLong-1;
394   static const int _lh_element_type_shift      = BitsPerByte*1;
395   static const int _lh_element_type_mask       = right_n_bits(BitsPerByte);  // shifted mask
396   static const int _lh_header_size_shift       = BitsPerByte*2;
397   static const int _lh_header_size_mask        = right_n_bits(BitsPerByte);  // shifted mask
398   static const int _lh_array_tag_bits          = 2;
399   static const int _lh_array_tag_shift         = BitsPerInt - _lh_array_tag_bits;
400   static const int _lh_array_tag_obj_value     = ~0x01;   // 0x80000000 >> 30
401 
402   static const unsigned int _lh_array_tag_type_value = 0Xffffffff; // ~0x00,  // 0xC0000000 >> 30
403 
404   static int layout_helper_size_in_bytes(jint lh) {
405     assert(lh > (jint)_lh_neutral_value, "must be instance");
406     return (int) lh & ~_lh_instance_slow_path_bit;
407   }
408   static bool layout_helper_needs_slow_path(jint lh) {
409     assert(lh > (jint)_lh_neutral_value, "must be instance");
410     return (lh & _lh_instance_slow_path_bit) != 0;
411   }
412   static bool layout_helper_is_instance(jint lh) {
413     return (jint)lh > (jint)_lh_neutral_value;
414   }
415   static bool layout_helper_is_array(jint lh) {
416     return (jint)lh < (jint)_lh_neutral_value;
417   }
418   static bool layout_helper_is_typeArray(jint lh) {
419     // _lh_array_tag_type_value == (lh >> _lh_array_tag_shift);
420     return (juint)lh >= (juint)(_lh_array_tag_type_value << _lh_array_tag_shift);
421   }
422   static bool layout_helper_is_objArray(jint lh) {
423     // _lh_array_tag_obj_value == (lh >> _lh_array_tag_shift);
424     return (jint)lh < (jint)(_lh_array_tag_type_value << _lh_array_tag_shift);
425   }
426   static int layout_helper_header_size(jint lh) {
427     assert(lh < (jint)_lh_neutral_value, "must be array");
428     int hsize = (lh >> _lh_header_size_shift) & _lh_header_size_mask;
429     assert(hsize > 0 && hsize < (int)sizeof(oopDesc)*3, "sanity");
430     return hsize;
431   }
432   static BasicType layout_helper_element_type(jint lh) {
433     assert(lh < (jint)_lh_neutral_value, "must be array");
434     int btvalue = (lh >> _lh_element_type_shift) & _lh_element_type_mask;
435     assert(btvalue >= T_BOOLEAN && btvalue <= T_OBJECT, "sanity");
436     return (BasicType) btvalue;
437   }
438 
439   // Want a pattern to quickly diff against layout header in register
440   // find something less clever!
441   static int layout_helper_boolean_diffbit() {
442     jint zlh = array_layout_helper(T_BOOLEAN);
443     jint blh = array_layout_helper(T_BYTE);
444     assert(zlh != blh, "array layout helpers must differ");
445     int diffbit = 1;
446     while ((diffbit & (zlh ^ blh)) == 0 && (diffbit & zlh) == 0) {
447       diffbit <<= 1;
448       assert(diffbit != 0, "make sure T_BOOLEAN has a different bit than T_BYTE");
449     }
450     return diffbit;
451   }
452 
453   static int layout_helper_log2_element_size(jint lh) {
454     assert(lh < (jint)_lh_neutral_value, "must be array");
455     int l2esz = (lh >> _lh_log2_element_size_shift) & _lh_log2_element_size_mask;
456     assert(l2esz <= LogBytesPerLong,
457            "sanity. l2esz: 0x%x for lh: 0x%x", (uint)l2esz, (uint)lh);
458     return l2esz;
459   }
460   static jint array_layout_helper(jint tag, int hsize, BasicType etype, int log2_esize) {
461     return (tag        << _lh_array_tag_shift)
462       |    (hsize      << _lh_header_size_shift)
463       |    ((int)etype << _lh_element_type_shift)
464       |    (log2_esize << _lh_log2_element_size_shift);
465   }
466   static jint instance_layout_helper(jint size, bool slow_path_flag) {
467     return (size << LogBytesPerWord)
468       |    (slow_path_flag ? _lh_instance_slow_path_bit : 0);
469   }
470   static int layout_helper_to_size_helper(jint lh) {
471     assert(lh > (jint)_lh_neutral_value, "must be instance");
472     // Note that the following expression discards _lh_instance_slow_path_bit.
473     return lh >> LogBytesPerWord;
474   }
475   // Out-of-line version computes everything based on the etype:
476   static jint array_layout_helper(BasicType etype);
477 
478   // What is the maximum number of primary superclasses any klass can have?
479   static juint primary_super_limit()         { return _primary_super_limit; }
480 
481   // vtables
482   klassVtable vtable() const;
483   int vtable_length() const { return _vtable_len; }
484 
485   // subclass check
486   bool is_subclass_of(const Klass* k) const;
487   // subtype check: true if is_subclass_of, or if k is interface and receiver implements it
488   bool is_subtype_of(Klass* k) const {
489     juint    off = k->super_check_offset();
490     Klass* sup = *(Klass**)( (address)this + off );
491     const juint secondary_offset = in_bytes(secondary_super_cache_offset());
492     if (sup == k) {
493       return true;
494     } else if (off != secondary_offset) {
495       return false;
496     } else {
497       return search_secondary_supers(k);
498     }
499   }
500 
501   bool search_secondary_supers(Klass* k) const;
502 
503   // Find LCA in class hierarchy
504   Klass *LCA( Klass *k );
505 
506   // Check whether reflection/jni/jvm code is allowed to instantiate this class;
507   // if not, throw either an Error or an Exception.
508   virtual void check_valid_for_instantiation(bool throwError, TRAPS);
509 
510   // array copying
511   virtual void  copy_array(arrayOop s, int src_pos, arrayOop d, int dst_pos, int length, TRAPS);
512 
513   // tells if the class should be initialized
514   virtual bool should_be_initialized() const    { return false; }
515   // initializes the klass
516   virtual void initialize(TRAPS);
517   virtual Klass* find_field(Symbol* name, Symbol* signature, fieldDescriptor* fd) const;
518   virtual Method* uncached_lookup_method(const Symbol* name, const Symbol* signature,
519                                          OverpassLookupMode overpass_mode,
520                                          PrivateLookupMode = PrivateLookupMode::find) const;
521  public:
522   Method* lookup_method(const Symbol* name, const Symbol* signature) const {
523     return uncached_lookup_method(name, signature, OverpassLookupMode::find);
524   }
525 
526   // array class with specific rank
527   virtual Klass* array_klass(int rank, TRAPS) = 0;
528 
529   // array class with this klass as element type
530   virtual Klass* array_klass(TRAPS) = 0;
531 
532   // These will return NULL instead of allocating on the heap:
533   virtual Klass* array_klass_or_null(int rank) = 0;
534   virtual Klass* array_klass_or_null() = 0;
535 
536   virtual oop protection_domain() const = 0;
537 
538   oop class_loader() const;
539 
540   inline oop klass_holder() const;
541 
542  protected:
543 
544   // Error handling when length > max_length or length < 0
545   static void check_array_allocation_length(int length, int max_length, TRAPS);
546 
547   void set_vtable_length(int len) { _vtable_len= len; }
548 
549   vtableEntry* start_of_vtable() const;
550   void restore_unshareable_info(ClassLoaderData* loader_data, Handle protection_domain, TRAPS);
551  public:
552   Method* method_at_vtable(int index);
553 
554   static ByteSize vtable_start_offset();
555   static ByteSize vtable_length_offset() {
556     return byte_offset_of(Klass, _vtable_len);
557   }
558 
559   // CDS support - remove and restore oops from metadata. Oops are not shared.
560   virtual void remove_unshareable_info();
561   virtual void remove_java_mirror();
562 
563   bool is_unshareable_info_restored() const {
564     assert(is_shared(), "use this for shared classes only");
565     if (has_archived_mirror_index()) {
566       // _java_mirror is not a valid OopHandle but rather an encoded reference in the shared heap
567       return false;
568     } else if (_java_mirror.ptr_raw() == NULL) {
569       return false;
570     } else {
571       return true;
572     }
573   }
574 
575  public:
576   // ALL FUNCTIONS BELOW THIS POINT ARE DISPATCHED FROM AN OOP
577   // These functions describe behavior for the oop not the KLASS.
578 
579   // actual oop size of obj in memory in word size.
580   virtual size_t oop_size(oop obj) const = 0;
581 
582   // Size of klass in word size.
583   virtual int size() const = 0;
584 
585   // Returns the Java name for a class (Resource allocated)
586   // For arrays, this returns the name of the element with a leading '['.
587   // For classes, this returns the name with the package separators
588   //     turned into '.'s.
589   const char* external_name() const;
590   // Returns the name for a class (Resource allocated) as the class
591   // would appear in a signature.
592   // For arrays, this returns the name of the element with a leading '['.
593   // For classes, this returns the name with a leading 'L' and a trailing ';'
594   //     and the package separators as '/'.
595   virtual const char* signature_name() const;
596 
597   const char* joint_in_module_of_loader(const Klass* class2, bool include_parent_loader = false) const;
598   const char* class_in_module_of_loader(bool use_are = false, bool include_parent_loader = false) const;
599 
600   // Returns "interface", "abstract class" or "class".
601   const char* external_kind() const;
602 
603   // type testing operations
604 #ifdef ASSERT
605  protected:
606   virtual bool is_instance_klass_slow()     const { return false; }
607   virtual bool is_array_klass_slow()        const { return false; }
608   virtual bool is_objArray_klass_slow()     const { return false; }
609   virtual bool is_typeArray_klass_slow()    const { return false; }
610 #endif // ASSERT
611  public:
612 
613   // Fast non-virtual versions
614   #ifndef ASSERT
615   #define assert_same_query(xval, xcheck) xval
616   #else
617  private:
618   static bool assert_same_query(bool xval, bool xslow) {
619     assert(xval == xslow, "slow and fast queries agree");
620     return xval;
621   }
622  public:
623   #endif
624 
625   bool is_instance_klass()              const { return assert_same_query(_kind <= InstanceStackChunkKlassKind, is_instance_klass_slow()); }
626   // Other is anything that is not one of the more specialized kinds of InstanceKlass.
627   bool is_other_instance_klass()        const { return _kind == InstanceKlassKind; }
628   bool is_reference_instance_klass()    const { return _kind == InstanceRefKlassKind; }
629   bool is_mirror_instance_klass()       const { return _kind == InstanceMirrorKlassKind; }
630   bool is_class_loader_instance_klass() const { return _kind == InstanceClassLoaderKlassKind; }
631   bool is_array_klass()                 const { return assert_same_query( _kind >= TypeArrayKlassKind, is_array_klass_slow()); }
632   bool is_stack_chunk_instance_klass()  const { return _kind == InstanceStackChunkKlassKind; }
633   bool is_objArray_klass()              const { return assert_same_query( _kind == ObjArrayKlassKind,  is_objArray_klass_slow()); }
634   bool is_typeArray_klass()             const { return assert_same_query( _kind == TypeArrayKlassKind, is_typeArray_klass_slow()); }
635   #undef assert_same_query
636 
637   // Access flags
638   AccessFlags access_flags() const         { return _access_flags;  }
639   void set_access_flags(AccessFlags flags) { _access_flags = flags; }
640 
641   bool is_public() const                { return _access_flags.is_public(); }
642   bool is_final() const                 { return _access_flags.is_final(); }
643   bool is_interface() const             { return _access_flags.is_interface(); }
644   bool is_abstract() const              { return _access_flags.is_abstract(); }
645   bool is_super() const                 { return _access_flags.is_super(); }
646   bool is_synthetic() const             { return _access_flags.is_synthetic(); }
647   void set_is_synthetic()               { _access_flags.set_is_synthetic(); }
648   bool has_finalizer() const            { return _access_flags.has_finalizer(); }
649   bool has_final_method() const         { return _access_flags.has_final_method(); }
650   void set_has_finalizer()              { _access_flags.set_has_finalizer(); }
651   void set_has_final_method()           { _access_flags.set_has_final_method(); }
652   bool has_vanilla_constructor() const  { return _access_flags.has_vanilla_constructor(); }
653   void set_has_vanilla_constructor()    { _access_flags.set_has_vanilla_constructor(); }
654   bool has_miranda_methods () const     { return access_flags().has_miranda_methods(); }
655   void set_has_miranda_methods()        { _access_flags.set_has_miranda_methods(); }
656   bool is_shared() const                { return access_flags().is_shared_class(); } // shadows MetaspaceObj::is_shared)()
657   void set_is_shared()                  { _access_flags.set_is_shared_class(); }
658   bool is_hidden() const                { return access_flags().is_hidden_class(); }
659   void set_is_hidden()                  { _access_flags.set_is_hidden_class(); }
660   bool is_value_based()                 { return _access_flags.is_value_based_class(); }
661   void set_is_value_based()             { _access_flags.set_is_value_based_class(); }
662 
663   inline bool is_non_strong_hidden() const;
664 
665   bool is_cloneable() const;
666   void set_is_cloneable();
667 
668   markWord prototype_header() const      { return _prototype_header; }
669   inline void set_prototype_header(markWord header);
670   static ByteSize prototype_header_offset() { return in_ByteSize(offset_of(Klass, _prototype_header)); }
671 
672   JFR_ONLY(DEFINE_TRACE_ID_METHODS;)
673 
674   virtual void metaspace_pointers_do(MetaspaceClosure* iter);
675   virtual MetaspaceObj::Type type() const { return ClassType; }
676 
677   inline bool is_loader_alive() const;
678 
679   void clean_subklass();
680 
681   static void clean_weak_klass_links(bool unloading_occurred, bool clean_alive_klasses = true);
682   static void clean_subklass_tree() {
683     clean_weak_klass_links(/*unloading_occurred*/ true , /* clean_alive_klasses */ false);
684   }
685 
686   // Return self, except for abstract classes with exactly 1
687   // implementor.  Then return the 1 concrete implementation.
688   Klass *up_cast_abstract();
689 
690   // klass name
691   Symbol* name() const                   { return _name; }
692   void set_name(Symbol* n);
693 
694   virtual void release_C_heap_structures(bool release_constant_pool = true);
695 
696  public:
697   virtual jint compute_modifier_flags() const = 0;
698 
699   // JVMTI support
700   virtual jint jvmti_class_status() const;
701 
702   // Printing
703   virtual void print_on(outputStream* st) const;
704 
705   virtual void oop_print_value_on(oop obj, outputStream* st);
706   virtual void oop_print_on      (oop obj, outputStream* st);
707 
708   virtual const char* internal_name() const = 0;
709 
710   // Verification
711   virtual void verify_on(outputStream* st);
712   void verify() { verify_on(tty); }
713 
714 #ifndef PRODUCT
715   bool verify_vtable_index(int index);
716 #endif
717 
718   virtual void oop_verify_on(oop obj, outputStream* st);
719 
720   // for error reporting
721   static bool is_valid(Klass* k);
722 };
723 
724 #endif // SHARE_OOPS_KLASS_HPP