1 /*
  2  * Copyright (c) 1997, 2021, 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 IDs for all subclasses of Klass
 41 enum KlassID {
 42   InstanceKlassID,
 43   InstanceRefKlassID,
 44   InstanceMirrorKlassID,
 45   InstanceClassLoaderKlassID,
 46   InstanceStackChunkKlassID,
 47   TypeArrayKlassID,
 48   ObjArrayKlassID
 49 };
 50 
 51 const uint KLASS_ID_COUNT = 7;
 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 identifier used to implement devirtualized oop closure dispatching.
119   const KlassID _id;
120 
121   // vtable length
122   int _vtable_len;
123 
124   // The fields _super_check_offset, _secondary_super_cache, _secondary_supers
125   // and _primary_supers all help make fast subtype checks.  See big discussion
126   // in doc/server_compiler/checktype.txt
127   //
128   // Where to look to observe a supertype (it is &_secondary_super_cache for
129   // secondary supers, else is &_primary_supers[depth()].
130   juint       _super_check_offset;
131 
132   // Class name.  Instance classes: java/lang/String, etc.  Array classes: [I,
133   // [Ljava/lang/String;, etc.  Set to zero for all other kinds of classes.
134   Symbol*     _name;
135 
136   // Cache of last observed secondary supertype
137   Klass*      _secondary_super_cache;
138   // Array of all secondary supertypes
139   Array<Klass*>* _secondary_supers;
140   // Ordered list of all primary supertypes
141   Klass*      _primary_supers[_primary_super_limit];
142   // java/lang/Class instance mirroring this class
143   OopHandle   _java_mirror;
144   // Superclass
145   Klass*      _super;
146   // First subclass (NULL if none); _subklass->next_sibling() is next one
147   Klass* volatile _subklass;
148   // Sibling link (or NULL); links all subklasses of a klass
149   Klass* volatile _next_sibling;
150 
151   // All klasses loaded by a class loader are chained through these links
152   Klass*      _next_link;
153 
154   // The VM's representation of the ClassLoader used to load this class.
155   // Provide access the corresponding instance java.lang.ClassLoader.
156   ClassLoaderData* _class_loader_data;
157 
158   jint        _modifier_flags;  // Processed access flags, for use by Class.getModifiers.
159   AccessFlags _access_flags;    // Access flags. The class/interface distinction is stored here.
160 
161   JFR_ONLY(DEFINE_TRACE_ID_FIELD;)
162 
163 private:
164   // This is an index into FileMapHeader::_shared_path_table[], to
165   // associate this class with the JAR file where it's loaded from during
166   // dump time. If a class is not loaded from the shared archive, this field is
167   // -1.
168   jshort _shared_class_path_index;
169 
170 #if INCLUDE_CDS
171   // Flags of the current shared class.
172   u2     _shared_class_flags;
173   enum {
174     _archived_lambda_proxy_is_available = 2,
175     _has_value_based_class_annotation = 4,
176     _verified_at_dump_time = 8
177   };
178 #endif
179 
180   CDS_JAVA_HEAP_ONLY(int _archived_mirror_index;)
181 
182 protected:
183 
184   // Constructor
185   Klass(KlassID id);
186   Klass() : _id(KlassID(-1)) { assert(DumpSharedSpaces || UseSharedSpaces, "only for cds"); }
187 
188   void* operator new(size_t size, ClassLoaderData* loader_data, size_t word_size, TRAPS) throw();
189 
190  public:
191   int id() { return _id; }
192 
193   enum class DefaultsLookupMode { find, skip };
194   enum class OverpassLookupMode { find, skip };
195   enum class StaticLookupMode   { find, skip };
196   enum class PrivateLookupMode  { find, skip };
197 
198   virtual bool is_klass() const { return true; }
199 
200   // super() cannot be InstanceKlass* -- Java arrays are covariant, and _super is used
201   // to implement that. NB: the _super of "[Ljava/lang/Integer;" is "[Ljava/lang/Number;"
202   // If this is not what your code expects, you're probably looking for Klass::java_super().
203   Klass* super() const               { return _super; }
204   void set_super(Klass* k)           { _super = k; }
205 
206   // initializes _super link, _primary_supers & _secondary_supers arrays
207   void initialize_supers(Klass* k, Array<InstanceKlass*>* transitive_interfaces, TRAPS);
208 
209   // klass-specific helper for initializing _secondary_supers
210   virtual GrowableArray<Klass*>* compute_secondary_supers(int num_extra_slots,
211                                                           Array<InstanceKlass*>* transitive_interfaces);
212 
213   // java_super is the Java-level super type as specified by Class.getSuperClass.
214   virtual InstanceKlass* java_super() const  { return NULL; }
215 
216   juint    super_check_offset() const  { return _super_check_offset; }
217   void set_super_check_offset(juint o) { _super_check_offset = o; }
218 
219   Klass* secondary_super_cache() const     { return _secondary_super_cache; }
220   void set_secondary_super_cache(Klass* k) { _secondary_super_cache = k; }
221 
222   Array<Klass*>* secondary_supers() const { return _secondary_supers; }
223   void set_secondary_supers(Array<Klass*>* k) { _secondary_supers = k; }
224 
225   // Return the element of the _super chain of the given depth.
226   // If there is no such element, return either NULL or this.
227   Klass* primary_super_of_depth(juint i) const {
228     assert(i < primary_super_limit(), "oob");
229     Klass* super = _primary_supers[i];
230     assert(super == NULL || super->super_depth() == i, "correct display");
231     return super;
232   }
233 
234   // Can this klass be a primary super?  False for interfaces and arrays of
235   // interfaces.  False also for arrays or classes with long super chains.
236   bool can_be_primary_super() const {
237     const juint secondary_offset = in_bytes(secondary_super_cache_offset());
238     return super_check_offset() != secondary_offset;
239   }
240   virtual bool can_be_primary_super_slow() const;
241 
242   // Returns number of primary supers; may be a number in the inclusive range [0, primary_super_limit].
243   juint super_depth() const {
244     if (!can_be_primary_super()) {
245       return primary_super_limit();
246     } else {
247       juint d = (super_check_offset() - in_bytes(primary_supers_offset())) / sizeof(Klass*);
248       assert(d < primary_super_limit(), "oob");
249       assert(_primary_supers[d] == this, "proper init");
250       return d;
251     }
252   }
253 
254   // java mirror
255   oop java_mirror() const;
256   oop java_mirror_no_keepalive() const;
257   void set_java_mirror(Handle m);
258 
259   oop archived_java_mirror() NOT_CDS_JAVA_HEAP_RETURN_(NULL);
260   void set_archived_java_mirror(oop m) NOT_CDS_JAVA_HEAP_RETURN;
261 
262   // Temporary mirror switch used by RedefineClasses
263   void replace_java_mirror(oop mirror);
264 
265   // Set java mirror OopHandle to NULL for CDS
266   // This leaves the OopHandle in the CLD, but that's ok, you can't release them.
267   void clear_java_mirror_handle() { _java_mirror = OopHandle(); }
268 
269   // modifier flags
270   jint modifier_flags() const          { return _modifier_flags; }
271   void set_modifier_flags(jint flags)  { _modifier_flags = flags; }
272 
273   // size helper
274   int layout_helper() const            { return _layout_helper; }
275   void set_layout_helper(int lh)       { _layout_helper = lh; }
276 
277   // Note: for instances layout_helper() may include padding.
278   // Use InstanceKlass::contains_field_offset to classify field offsets.
279 
280   // sub/superklass links
281   Klass* subklass(bool log = false) const;
282   Klass* next_sibling(bool log = false) const;
283 
284   InstanceKlass* superklass() const;
285   void append_to_sibling_list();           // add newly created receiver to superklass' subklass list
286 
287   void set_next_link(Klass* k) { _next_link = k; }
288   Klass* next_link() const { return _next_link; }   // The next klass defined by the class loader.
289   Klass** next_link_addr() { return &_next_link; }
290 
291   // class loader data
292   ClassLoaderData* class_loader_data() const               { return _class_loader_data; }
293   void set_class_loader_data(ClassLoaderData* loader_data) {  _class_loader_data = loader_data; }
294 
295   int shared_classpath_index() const   {
296     return _shared_class_path_index;
297   };
298 
299   void set_shared_classpath_index(int index) {
300     _shared_class_path_index = index;
301   };
302 
303   bool has_archived_mirror_index() const {
304     CDS_JAVA_HEAP_ONLY(return _archived_mirror_index >= 0;)
305     NOT_CDS_JAVA_HEAP(return false);
306   }
307 
308   void clear_archived_mirror_index() NOT_CDS_JAVA_HEAP_RETURN;
309 
310   void set_lambda_proxy_is_available() {
311     CDS_ONLY(_shared_class_flags |= _archived_lambda_proxy_is_available;)
312   }
313   void clear_lambda_proxy_is_available() {
314     CDS_ONLY(_shared_class_flags &= ~_archived_lambda_proxy_is_available;)
315   }
316   bool lambda_proxy_is_available() const {
317     CDS_ONLY(return (_shared_class_flags & _archived_lambda_proxy_is_available) != 0;)
318     NOT_CDS(return false;)
319   }
320 
321   void set_has_value_based_class_annotation() {
322     CDS_ONLY(_shared_class_flags |= _has_value_based_class_annotation;)
323   }
324   void clear_has_value_based_class_annotation() {
325     CDS_ONLY(_shared_class_flags &= ~_has_value_based_class_annotation;)
326   }
327   bool has_value_based_class_annotation() const {
328     CDS_ONLY(return (_shared_class_flags & _has_value_based_class_annotation) != 0;)
329     NOT_CDS(return false;)
330   }
331 
332   void set_verified_at_dump_time() {
333     CDS_ONLY(_shared_class_flags |= _verified_at_dump_time;)
334   }
335   bool verified_at_dump_time() const {
336     CDS_ONLY(return (_shared_class_flags & _verified_at_dump_time) != 0;)
337     NOT_CDS(return false;)
338   }
339 
340 
341   // Obtain the module or package for this class
342   virtual ModuleEntry* module() const = 0;
343   virtual PackageEntry* package() const = 0;
344 
345  protected:                                // internal accessors
346   void     set_subklass(Klass* s);
347   void     set_next_sibling(Klass* s);
348 
349  public:
350 
351   // Compiler support
352   static ByteSize super_offset()                 { return in_ByteSize(offset_of(Klass, _super)); }
353   static ByteSize super_check_offset_offset()    { return in_ByteSize(offset_of(Klass, _super_check_offset)); }
354   static ByteSize primary_supers_offset()        { return in_ByteSize(offset_of(Klass, _primary_supers)); }
355   static ByteSize secondary_super_cache_offset() { return in_ByteSize(offset_of(Klass, _secondary_super_cache)); }
356   static ByteSize secondary_supers_offset()      { return in_ByteSize(offset_of(Klass, _secondary_supers)); }
357   static ByteSize java_mirror_offset()           { return in_ByteSize(offset_of(Klass, _java_mirror)); }
358   static ByteSize class_loader_data_offset()     { return in_ByteSize(offset_of(Klass, _class_loader_data)); }
359   static ByteSize modifier_flags_offset()        { return in_ByteSize(offset_of(Klass, _modifier_flags)); }
360   static ByteSize layout_helper_offset()         { return in_ByteSize(offset_of(Klass, _layout_helper)); }
361   static ByteSize access_flags_offset()          { return in_ByteSize(offset_of(Klass, _access_flags)); }
362 
363   // Unpacking layout_helper:
364   static const int _lh_neutral_value           = 0;  // neutral non-array non-instance value
365   static const int _lh_instance_slow_path_bit  = 0x01;
366   static const int _lh_log2_element_size_shift = BitsPerByte*0;
367   static const int _lh_log2_element_size_mask  = BitsPerLong-1;
368   static const int _lh_element_type_shift      = BitsPerByte*1;
369   static const int _lh_element_type_mask       = right_n_bits(BitsPerByte);  // shifted mask
370   static const int _lh_header_size_shift       = BitsPerByte*2;
371   static const int _lh_header_size_mask        = right_n_bits(BitsPerByte);  // shifted mask
372   static const int _lh_array_tag_bits          = 2;
373   static const int _lh_array_tag_shift         = BitsPerInt - _lh_array_tag_bits;
374   static const int _lh_array_tag_obj_value     = ~0x01;   // 0x80000000 >> 30
375 
376   static const unsigned int _lh_array_tag_type_value = 0Xffffffff; // ~0x00,  // 0xC0000000 >> 30
377 
378   static int layout_helper_size_in_bytes(jint lh) {
379     assert(lh > (jint)_lh_neutral_value, "must be instance");
380     return (int) lh & ~_lh_instance_slow_path_bit;
381   }
382   static bool layout_helper_needs_slow_path(jint lh) {
383     assert(lh > (jint)_lh_neutral_value, "must be instance");
384     return (lh & _lh_instance_slow_path_bit) != 0;
385   }
386   static bool layout_helper_is_instance(jint lh) {
387     return (jint)lh > (jint)_lh_neutral_value;
388   }
389   static bool layout_helper_is_array(jint lh) {
390     return (jint)lh < (jint)_lh_neutral_value;
391   }
392   static bool layout_helper_is_typeArray(jint lh) {
393     // _lh_array_tag_type_value == (lh >> _lh_array_tag_shift);
394     return (juint)lh >= (juint)(_lh_array_tag_type_value << _lh_array_tag_shift);
395   }
396   static bool layout_helper_is_objArray(jint lh) {
397     // _lh_array_tag_obj_value == (lh >> _lh_array_tag_shift);
398     return (jint)lh < (jint)(_lh_array_tag_type_value << _lh_array_tag_shift);
399   }
400   static int layout_helper_header_size(jint lh) {
401     assert(lh < (jint)_lh_neutral_value, "must be array");
402     int hsize = (lh >> _lh_header_size_shift) & _lh_header_size_mask;
403     assert(hsize > 0 && hsize < (int)sizeof(oopDesc)*3, "sanity");
404     return hsize;
405   }
406   static BasicType layout_helper_element_type(jint lh) {
407     assert(lh < (jint)_lh_neutral_value, "must be array");
408     int btvalue = (lh >> _lh_element_type_shift) & _lh_element_type_mask;
409     assert(btvalue >= T_BOOLEAN && btvalue <= T_OBJECT, "sanity");
410     return (BasicType) btvalue;
411   }
412 
413   // Want a pattern to quickly diff against layout header in register
414   // find something less clever!
415   static int layout_helper_boolean_diffbit() {
416     jint zlh = array_layout_helper(T_BOOLEAN);
417     jint blh = array_layout_helper(T_BYTE);
418     assert(zlh != blh, "array layout helpers must differ");
419     int diffbit = 1;
420     while ((diffbit & (zlh ^ blh)) == 0 && (diffbit & zlh) == 0) {
421       diffbit <<= 1;
422       assert(diffbit != 0, "make sure T_BOOLEAN has a different bit than T_BYTE");
423     }
424     return diffbit;
425   }
426 
427   static int layout_helper_log2_element_size(jint lh) {
428     assert(lh < (jint)_lh_neutral_value, "must be array");
429     int l2esz = (lh >> _lh_log2_element_size_shift) & _lh_log2_element_size_mask;
430     assert(l2esz <= LogBytesPerLong,
431            "sanity. l2esz: 0x%x for lh: 0x%x", (uint)l2esz, (uint)lh);
432     return l2esz;
433   }
434   static jint array_layout_helper(jint tag, int hsize, BasicType etype, int log2_esize) {
435     return (tag        << _lh_array_tag_shift)
436       |    (hsize      << _lh_header_size_shift)
437       |    ((int)etype << _lh_element_type_shift)
438       |    (log2_esize << _lh_log2_element_size_shift);
439   }
440   static jint instance_layout_helper(jint size, bool slow_path_flag) {
441     return (size << LogBytesPerWord)
442       |    (slow_path_flag ? _lh_instance_slow_path_bit : 0);
443   }
444   static int layout_helper_to_size_helper(jint lh) {
445     assert(lh > (jint)_lh_neutral_value, "must be instance");
446     // Note that the following expression discards _lh_instance_slow_path_bit.
447     return lh >> LogBytesPerWord;
448   }
449   // Out-of-line version computes everything based on the etype:
450   static jint array_layout_helper(BasicType etype);
451 
452   // What is the maximum number of primary superclasses any klass can have?
453   static juint primary_super_limit()         { return _primary_super_limit; }
454 
455   // vtables
456   klassVtable vtable() const;
457   int vtable_length() const { return _vtable_len; }
458 
459   // subclass check
460   bool is_subclass_of(const Klass* k) const;
461   // subtype check: true if is_subclass_of, or if k is interface and receiver implements it
462   bool is_subtype_of(Klass* k) const {
463     juint    off = k->super_check_offset();
464     Klass* sup = *(Klass**)( (address)this + off );
465     const juint secondary_offset = in_bytes(secondary_super_cache_offset());
466     if (sup == k) {
467       return true;
468     } else if (off != secondary_offset) {
469       return false;
470     } else {
471       return search_secondary_supers(k);
472     }
473   }
474 
475   bool search_secondary_supers(Klass* k) const;
476 
477   // Find LCA in class hierarchy
478   Klass *LCA( Klass *k );
479 
480   // Check whether reflection/jni/jvm code is allowed to instantiate this class;
481   // if not, throw either an Error or an Exception.
482   virtual void check_valid_for_instantiation(bool throwError, TRAPS);
483 
484   // array copying
485   virtual void  copy_array(arrayOop s, int src_pos, arrayOop d, int dst_pos, int length, TRAPS);
486 
487   // tells if the class should be initialized
488   virtual bool should_be_initialized() const    { return false; }
489   // initializes the klass
490   virtual void initialize(TRAPS);
491   virtual Klass* find_field(Symbol* name, Symbol* signature, fieldDescriptor* fd) const;
492   virtual Method* uncached_lookup_method(const Symbol* name, const Symbol* signature,
493                                          OverpassLookupMode overpass_mode,
494                                          PrivateLookupMode = PrivateLookupMode::find) const;
495  public:
496   Method* lookup_method(const Symbol* name, const Symbol* signature) const {
497     return uncached_lookup_method(name, signature, OverpassLookupMode::find);
498   }
499 
500   // array class with specific rank
501   virtual Klass* array_klass(int rank, TRAPS) = 0;
502 
503   // array class with this klass as element type
504   virtual Klass* array_klass(TRAPS) = 0;
505 
506   // These will return NULL instead of allocating on the heap:
507   virtual Klass* array_klass_or_null(int rank) = 0;
508   virtual Klass* array_klass_or_null() = 0;
509 
510   virtual oop protection_domain() const = 0;
511 
512   oop class_loader() const;
513 
514   inline oop klass_holder() const;
515 
516  protected:
517 
518   // Error handling when length > max_length or length < 0
519   static void check_array_allocation_length(int length, int max_length, TRAPS);
520 
521   void set_vtable_length(int len) { _vtable_len= len; }
522 
523   vtableEntry* start_of_vtable() const;
524   void restore_unshareable_info(ClassLoaderData* loader_data, Handle protection_domain, TRAPS);
525  public:
526   Method* method_at_vtable(int index);
527 
528   static ByteSize vtable_start_offset();
529   static ByteSize vtable_length_offset() {
530     return byte_offset_of(Klass, _vtable_len);
531   }
532 
533   // CDS support - remove and restore oops from metadata. Oops are not shared.
534   virtual void remove_unshareable_info();
535   virtual void remove_java_mirror();
536 
537   bool is_unshareable_info_restored() const {
538     assert(is_shared(), "use this for shared classes only");
539     if (has_archived_mirror_index()) {
540       // _java_mirror is not a valid OopHandle but rather an encoded reference in the shared heap
541       return false;
542     } else if (_java_mirror.ptr_raw() == NULL) {
543       return false;
544     } else {
545       return true;
546     }
547   }
548 
549  public:
550   // ALL FUNCTIONS BELOW THIS POINT ARE DISPATCHED FROM AN OOP
551   // These functions describe behavior for the oop not the KLASS.
552 
553   // actual oop size of obj in memory
554   virtual int oop_size(oop obj) const = 0;
555 
556   // the size of the object in memory after possible compression during GC promotion/compaction
557   virtual int compact_oop_size(oop obj) const { return oop_size(obj); }
558 
559   // Size of klass in word size.
560   virtual int size() const = 0;
561 
562   // Returns the Java name for a class (Resource allocated)
563   // For arrays, this returns the name of the element with a leading '['.
564   // For classes, this returns the name with the package separators
565   //     turned into '.'s.
566   const char* external_name() const;
567   // Returns the name for a class (Resource allocated) as the class
568   // would appear in a signature.
569   // For arrays, this returns the name of the element with a leading '['.
570   // For classes, this returns the name with a leading 'L' and a trailing ';'
571   //     and the package separators as '/'.
572   virtual const char* signature_name() const;
573 
574   const char* joint_in_module_of_loader(const Klass* class2, bool include_parent_loader = false) const;
575   const char* class_in_module_of_loader(bool use_are = false, bool include_parent_loader = false) const;
576 
577   // Returns "interface", "abstract class" or "class".
578   const char* external_kind() const;
579 
580   virtual size_t copy_disjoint(oop obj, HeapWord* to, size_t word_size);
581   virtual size_t copy_conjoint(oop obj, HeapWord* to, size_t word_size);
582   virtual size_t copy_disjoint_compact(oop obj, HeapWord* to);
583   virtual size_t copy_conjoint_compact(oop obj, HeapWord* to);
584 
585   // type testing operations
586 #ifdef ASSERT
587  protected:
588   virtual bool is_instance_klass_slow()     const { return false; }
589   virtual bool is_array_klass_slow()        const { return false; }
590   virtual bool is_objArray_klass_slow()     const { return false; }
591   virtual bool is_typeArray_klass_slow()    const { return false; }
592 #endif // ASSERT
593  public:
594 
595   // Fast non-virtual versions
596   #ifndef ASSERT
597   #define assert_same_query(xval, xcheck) xval
598   #else
599  private:
600   static bool assert_same_query(bool xval, bool xslow) {
601     assert(xval == xslow, "slow and fast queries agree");
602     return xval;
603   }
604  public:
605   #endif
606   inline  bool is_instance_klass()            const { return assert_same_query(
607                                                       layout_helper_is_instance(layout_helper()),
608                                                       is_instance_klass_slow()); }
609   inline  bool is_array_klass()               const { return assert_same_query(
610                                                     layout_helper_is_array(layout_helper()),
611                                                     is_array_klass_slow()); }
612   inline  bool is_objArray_klass()            const { return assert_same_query(
613                                                     layout_helper_is_objArray(layout_helper()),
614                                                     is_objArray_klass_slow()); }
615   inline  bool is_typeArray_klass()           const { return assert_same_query(
616                                                     layout_helper_is_typeArray(layout_helper()),
617                                                     is_typeArray_klass_slow()); }
618   #undef assert_same_query
619 
620   // Access flags
621   AccessFlags access_flags() const         { return _access_flags;  }
622   void set_access_flags(AccessFlags flags) { _access_flags = flags; }
623 
624   bool is_public() const                { return _access_flags.is_public(); }
625   bool is_final() const                 { return _access_flags.is_final(); }
626   bool is_interface() const             { return _access_flags.is_interface(); }
627   bool is_abstract() const              { return _access_flags.is_abstract(); }
628   bool is_super() const                 { return _access_flags.is_super(); }
629   bool is_synthetic() const             { return _access_flags.is_synthetic(); }
630   void set_is_synthetic()               { _access_flags.set_is_synthetic(); }
631   bool has_finalizer() const            { return _access_flags.has_finalizer(); }
632   bool has_final_method() const         { return _access_flags.has_final_method(); }
633   void set_has_finalizer()              { _access_flags.set_has_finalizer(); }
634   void set_has_final_method()           { _access_flags.set_has_final_method(); }
635   bool has_vanilla_constructor() const  { return _access_flags.has_vanilla_constructor(); }
636   void set_has_vanilla_constructor()    { _access_flags.set_has_vanilla_constructor(); }
637   bool has_miranda_methods () const     { return access_flags().has_miranda_methods(); }
638   void set_has_miranda_methods()        { _access_flags.set_has_miranda_methods(); }
639   bool is_shared() const                { return access_flags().is_shared_class(); } // shadows MetaspaceObj::is_shared)()
640   void set_is_shared()                  { _access_flags.set_is_shared_class(); }
641   bool is_hidden() const                { return access_flags().is_hidden_class(); }
642   void set_is_hidden()                  { _access_flags.set_is_hidden_class(); }
643   bool is_value_based()                 { return _access_flags.is_value_based_class(); }
644   void set_is_value_based()             { _access_flags.set_is_value_based_class(); }
645 
646   inline bool is_non_strong_hidden() const;
647 
648   bool is_cloneable() const;
649   void set_is_cloneable();
650 
651   JFR_ONLY(DEFINE_TRACE_ID_METHODS;)
652 
653   virtual void metaspace_pointers_do(MetaspaceClosure* iter);
654   virtual MetaspaceObj::Type type() const { return ClassType; }
655 
656   inline bool is_loader_alive() const;
657 
658   void clean_subklass();
659 
660   static void clean_weak_klass_links(bool unloading_occurred, bool clean_alive_klasses = true);
661   static void clean_subklass_tree() {
662     clean_weak_klass_links(/*unloading_occurred*/ true , /* clean_alive_klasses */ false);
663   }
664 
665   virtual void array_klasses_do(void f(Klass* k)) {}
666 
667   // Return self, except for abstract classes with exactly 1
668   // implementor.  Then return the 1 concrete implementation.
669   Klass *up_cast_abstract();
670 
671   // klass name
672   Symbol* name() const                   { return _name; }
673   void set_name(Symbol* n);
674 
675   virtual void release_C_heap_structures();
676 
677  public:
678   virtual jint compute_modifier_flags() const = 0;
679 
680   // JVMTI support
681   virtual jint jvmti_class_status() const;
682 
683   // Printing
684   virtual void print_on(outputStream* st) const;
685 
686   virtual void oop_print_value_on(oop obj, outputStream* st);
687   virtual void oop_print_on      (oop obj, outputStream* st);
688 
689   virtual const char* internal_name() const = 0;
690 
691   // Verification
692   virtual void verify_on(outputStream* st);
693   void verify() { verify_on(tty); }
694 
695 #ifndef PRODUCT
696   bool verify_vtable_index(int index);
697 #endif
698 
699   virtual void oop_verify_on(oop obj, outputStream* st);
700 
701   // for error reporting
702   static bool is_valid(Klass* k);
703 };
704 
705 #endif // SHARE_OOPS_KLASS_HPP