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   TypeArrayKlassID,
 47   ObjArrayKlassID
 48 };
 49 
 50 const uint KLASS_ID_COUNT = 6;
 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 identifier used to implement devirtualized oop closure dispatching.
118   const KlassID _id;
119 
120   // vtable length
121   int _vtable_len;
122 
123   // The fields _super_check_offset, _secondary_super_cache, _secondary_supers
124   // and _primary_supers all help make fast subtype checks.  See big discussion
125   // in doc/server_compiler/checktype.txt
126   //
127   // Where to look to observe a supertype (it is &_secondary_super_cache for
128   // secondary supers, else is &_primary_supers[depth()].
129   juint       _super_check_offset;
130 
131   // Class name.  Instance classes: java/lang/String, etc.  Array classes: [I,
132   // [Ljava/lang/String;, etc.  Set to zero for all other kinds of classes.
133   Symbol*     _name;
134 
135   // Cache of last observed secondary supertype
136   Klass*      _secondary_super_cache;
137   // Array of all secondary supertypes
138   Array<Klass*>* _secondary_supers;
139   // Ordered list of all primary supertypes
140   Klass*      _primary_supers[_primary_super_limit];
141   // java/lang/Class instance mirroring this class
142   OopHandle   _java_mirror;
143   // Superclass
144   Klass*      _super;
145   // First subclass (NULL if none); _subklass->next_sibling() is next one
146   Klass* volatile _subklass;
147   // Sibling link (or NULL); links all subklasses of a klass
148   Klass* volatile _next_sibling;
149 
150   // All klasses loaded by a class loader are chained through these links
151   Klass*      _next_link;
152 
153   // The VM's representation of the ClassLoader used to load this class.
154   // Provide access the corresponding instance java.lang.ClassLoader.
155   ClassLoaderData* _class_loader_data;
156 
157   jint        _modifier_flags;  // Processed access flags, for use by Class.getModifiers.
158   AccessFlags _access_flags;    // Access flags. The class/interface distinction is stored here.
159 
160   JFR_ONLY(DEFINE_TRACE_ID_FIELD;)
161 
162   markWord _prototype_header;   // Used to initialize objects' header
163 
164 private:
165   // This is an index into FileMapHeader::_shared_path_table[], to
166   // associate this class with the JAR file where it's loaded from during
167   // dump time. If a class is not loaded from the shared archive, this field is
168   // -1.
169   jshort _shared_class_path_index;
170 
171 #if INCLUDE_CDS
172   // Flags of the current shared class.
173   u2     _shared_class_flags;
174   enum {
175     _archived_lambda_proxy_is_available = 2,
176     _has_value_based_class_annotation = 4,
177     _verified_at_dump_time = 8
178   };
179 #endif
180 
181   CDS_JAVA_HEAP_ONLY(int _archived_mirror_index;)
182 
183 protected:
184 
185   // Constructor
186   Klass(KlassID id);
187   Klass() : _id(KlassID(-1)) { assert(DumpSharedSpaces || UseSharedSpaces, "only for cds"); }
188 
189   void* operator new(size_t size, ClassLoaderData* loader_data, size_t word_size, TRAPS) throw();
190 
191  public:
192   int id() { return _id; }
193 
194   enum class DefaultsLookupMode { find, skip };
195   enum class OverpassLookupMode { find, skip };
196   enum class StaticLookupMode   { find, skip };
197   enum class PrivateLookupMode  { find, skip };
198 
199   virtual bool is_klass() const { return true; }
200 
201   // super() cannot be InstanceKlass* -- Java arrays are covariant, and _super is used
202   // to implement that. NB: the _super of "[Ljava/lang/Integer;" is "[Ljava/lang/Number;"
203   // If this is not what your code expects, you're probably looking for Klass::java_super().
204   Klass* super() const               { return _super; }
205   void set_super(Klass* k)           { _super = k; }
206 
207   // initializes _super link, _primary_supers & _secondary_supers arrays
208   void initialize_supers(Klass* k, Array<InstanceKlass*>* transitive_interfaces, TRAPS);
209 
210   // klass-specific helper for initializing _secondary_supers
211   virtual GrowableArray<Klass*>* compute_secondary_supers(int num_extra_slots,
212                                                           Array<InstanceKlass*>* transitive_interfaces);
213 
214   // java_super is the Java-level super type as specified by Class.getSuperClass.
215   virtual InstanceKlass* java_super() const  { return NULL; }
216 
217   juint    super_check_offset() const  { return _super_check_offset; }
218   void set_super_check_offset(juint o) { _super_check_offset = o; }
219 
220   Klass* secondary_super_cache() const     { return _secondary_super_cache; }
221   void set_secondary_super_cache(Klass* k) { _secondary_super_cache = k; }
222 
223   Array<Klass*>* secondary_supers() const { return _secondary_supers; }
224   void set_secondary_supers(Array<Klass*>* k) { _secondary_supers = k; }
225 
226   // Return the element of the _super chain of the given depth.
227   // If there is no such element, return either NULL or this.
228   Klass* primary_super_of_depth(juint i) const {
229     assert(i < primary_super_limit(), "oob");
230     Klass* super = _primary_supers[i];
231     assert(super == NULL || super->super_depth() == i, "correct display");
232     return super;
233   }
234 
235   // Can this klass be a primary super?  False for interfaces and arrays of
236   // interfaces.  False also for arrays or classes with long super chains.
237   bool can_be_primary_super() const {
238     const juint secondary_offset = in_bytes(secondary_super_cache_offset());
239     return super_check_offset() != secondary_offset;
240   }
241   virtual bool can_be_primary_super_slow() const;
242 
243   // Returns number of primary supers; may be a number in the inclusive range [0, primary_super_limit].
244   juint super_depth() const {
245     if (!can_be_primary_super()) {
246       return primary_super_limit();
247     } else {
248       juint d = (super_check_offset() - in_bytes(primary_supers_offset())) / sizeof(Klass*);
249       assert(d < primary_super_limit(), "oob");
250       assert(_primary_supers[d] == this, "proper init");
251       return d;
252     }
253   }
254 
255   // java mirror
256   oop java_mirror() const;
257   oop java_mirror_no_keepalive() const;
258   void set_java_mirror(Handle m);
259 
260   oop archived_java_mirror() NOT_CDS_JAVA_HEAP_RETURN_(NULL);
261   void set_archived_java_mirror(oop m) NOT_CDS_JAVA_HEAP_RETURN;
262 
263   // Temporary mirror switch used by RedefineClasses
264   void replace_java_mirror(oop mirror);
265 
266   // Set java mirror OopHandle to NULL for CDS
267   // This leaves the OopHandle in the CLD, but that's ok, you can't release them.
268   void clear_java_mirror_handle() { _java_mirror = OopHandle(); }
269 
270   // modifier flags
271   jint modifier_flags() const          { return _modifier_flags; }
272   void set_modifier_flags(jint flags)  { _modifier_flags = flags; }
273 
274   // size helper
275   int layout_helper() const            { return _layout_helper; }
276   void set_layout_helper(int lh)       { _layout_helper = lh; }
277 
278   // Note: for instances layout_helper() may include padding.
279   // Use InstanceKlass::contains_field_offset to classify field offsets.
280 
281   // sub/superklass links
282   Klass* subklass(bool log = false) const;
283   Klass* next_sibling(bool log = false) const;
284 
285   InstanceKlass* superklass() const;
286   void append_to_sibling_list();           // add newly created receiver to superklass' subklass list
287 
288   void set_next_link(Klass* k) { _next_link = k; }
289   Klass* next_link() const { return _next_link; }   // The next klass defined by the class loader.
290   Klass** next_link_addr() { return &_next_link; }
291 
292   // class loader data
293   ClassLoaderData* class_loader_data() const               { return _class_loader_data; }
294   void set_class_loader_data(ClassLoaderData* loader_data) {  _class_loader_data = loader_data; }
295 
296   int shared_classpath_index() const   {
297     return _shared_class_path_index;
298   };
299 
300   void set_shared_classpath_index(int index) {
301     _shared_class_path_index = index;
302   };
303 
304   bool has_archived_mirror_index() const {
305     CDS_JAVA_HEAP_ONLY(return _archived_mirror_index >= 0;)
306     NOT_CDS_JAVA_HEAP(return false);
307   }
308 
309   void clear_archived_mirror_index() NOT_CDS_JAVA_HEAP_RETURN;
310 
311   void set_lambda_proxy_is_available() {
312     CDS_ONLY(_shared_class_flags |= _archived_lambda_proxy_is_available;)
313   }
314   void clear_lambda_proxy_is_available() {
315     CDS_ONLY(_shared_class_flags &= ~_archived_lambda_proxy_is_available;)
316   }
317   bool lambda_proxy_is_available() const {
318     CDS_ONLY(return (_shared_class_flags & _archived_lambda_proxy_is_available) != 0;)
319     NOT_CDS(return false;)
320   }
321 
322   void set_has_value_based_class_annotation() {
323     CDS_ONLY(_shared_class_flags |= _has_value_based_class_annotation;)
324   }
325   void clear_has_value_based_class_annotation() {
326     CDS_ONLY(_shared_class_flags &= ~_has_value_based_class_annotation;)
327   }
328   bool has_value_based_class_annotation() const {
329     CDS_ONLY(return (_shared_class_flags & _has_value_based_class_annotation) != 0;)
330     NOT_CDS(return false;)
331   }
332 
333   void set_verified_at_dump_time() {
334     CDS_ONLY(_shared_class_flags |= _verified_at_dump_time;)
335   }
336   bool verified_at_dump_time() const {
337     CDS_ONLY(return (_shared_class_flags & _verified_at_dump_time) != 0;)
338     NOT_CDS(return false;)
339   }
340 
341 
342   // Obtain the module or package for this class
343   virtual ModuleEntry* module() const = 0;
344   virtual PackageEntry* package() const = 0;
345 
346  protected:                                // internal accessors
347   void     set_subklass(Klass* s);
348   void     set_next_sibling(Klass* s);
349 
350  public:
351 
352   // Compiler support
353   static ByteSize super_offset()                 { return in_ByteSize(offset_of(Klass, _super)); }
354   static ByteSize super_check_offset_offset()    { return in_ByteSize(offset_of(Klass, _super_check_offset)); }
355   static ByteSize primary_supers_offset()        { return in_ByteSize(offset_of(Klass, _primary_supers)); }
356   static ByteSize secondary_super_cache_offset() { return in_ByteSize(offset_of(Klass, _secondary_super_cache)); }
357   static ByteSize secondary_supers_offset()      { return in_ByteSize(offset_of(Klass, _secondary_supers)); }
358   static ByteSize java_mirror_offset()           { return in_ByteSize(offset_of(Klass, _java_mirror)); }
359   static ByteSize class_loader_data_offset()     { return in_ByteSize(offset_of(Klass, _class_loader_data)); }
360   static ByteSize modifier_flags_offset()        { return in_ByteSize(offset_of(Klass, _modifier_flags)); }
361   static ByteSize layout_helper_offset()         { return in_ByteSize(offset_of(Klass, _layout_helper)); }
362   static ByteSize access_flags_offset()          { return in_ByteSize(offset_of(Klass, _access_flags)); }
363 
364   // Unpacking layout_helper:
365   static const int _lh_neutral_value           = 0;  // neutral non-array non-instance value
366   static const int _lh_instance_slow_path_bit  = 0x01;
367   static const int _lh_log2_element_size_shift = BitsPerByte*0;
368   static const int _lh_log2_element_size_mask  = BitsPerLong-1;
369   static const int _lh_element_type_shift      = BitsPerByte*1;
370   static const int _lh_element_type_mask       = right_n_bits(BitsPerByte);  // shifted mask
371   static const int _lh_header_size_shift       = BitsPerByte*2;
372   static const int _lh_header_size_mask        = right_n_bits(BitsPerByte);  // shifted mask
373   static const int _lh_array_tag_bits          = 2;
374   static const int _lh_array_tag_shift         = BitsPerInt - _lh_array_tag_bits;
375   static const int _lh_array_tag_obj_value     = ~0x01;   // 0x80000000 >> 30
376 
377   static const unsigned int _lh_array_tag_type_value = 0Xffffffff; // ~0x00,  // 0xC0000000 >> 30
378 
379   static int layout_helper_size_in_bytes(jint lh) {
380     assert(lh > (jint)_lh_neutral_value, "must be instance");
381     return (int) lh & ~_lh_instance_slow_path_bit;
382   }
383   static bool layout_helper_needs_slow_path(jint lh) {
384     assert(lh > (jint)_lh_neutral_value, "must be instance");
385     return (lh & _lh_instance_slow_path_bit) != 0;
386   }
387   static bool layout_helper_is_instance(jint lh) {
388     return (jint)lh > (jint)_lh_neutral_value;
389   }
390   static bool layout_helper_is_array(jint lh) {
391     return (jint)lh < (jint)_lh_neutral_value;
392   }
393   static bool layout_helper_is_typeArray(jint lh) {
394     // _lh_array_tag_type_value == (lh >> _lh_array_tag_shift);
395     return (juint)lh >= (juint)(_lh_array_tag_type_value << _lh_array_tag_shift);
396   }
397   static bool layout_helper_is_objArray(jint lh) {
398     // _lh_array_tag_obj_value == (lh >> _lh_array_tag_shift);
399     return (jint)lh < (jint)(_lh_array_tag_type_value << _lh_array_tag_shift);
400   }
401   static int layout_helper_header_size(jint lh) {
402     assert(lh < (jint)_lh_neutral_value, "must be array");
403     int hsize = (lh >> _lh_header_size_shift) & _lh_header_size_mask;
404     assert(hsize > 0 && hsize < (int)sizeof(oopDesc)*3, "sanity");
405     return hsize;
406   }
407   static BasicType layout_helper_element_type(jint lh) {
408     assert(lh < (jint)_lh_neutral_value, "must be array");
409     int btvalue = (lh >> _lh_element_type_shift) & _lh_element_type_mask;
410     assert(btvalue >= T_BOOLEAN && btvalue <= T_OBJECT, "sanity");
411     return (BasicType) btvalue;
412   }
413 
414   // Want a pattern to quickly diff against layout header in register
415   // find something less clever!
416   static int layout_helper_boolean_diffbit() {
417     jint zlh = array_layout_helper(T_BOOLEAN);
418     jint blh = array_layout_helper(T_BYTE);
419     assert(zlh != blh, "array layout helpers must differ");
420     int diffbit = 1;
421     while ((diffbit & (zlh ^ blh)) == 0 && (diffbit & zlh) == 0) {
422       diffbit <<= 1;
423       assert(diffbit != 0, "make sure T_BOOLEAN has a different bit than T_BYTE");
424     }
425     return diffbit;
426   }
427 
428   static int layout_helper_log2_element_size(jint lh) {
429     assert(lh < (jint)_lh_neutral_value, "must be array");
430     int l2esz = (lh >> _lh_log2_element_size_shift) & _lh_log2_element_size_mask;
431     assert(l2esz <= LogBytesPerLong,
432            "sanity. l2esz: 0x%x for lh: 0x%x", (uint)l2esz, (uint)lh);
433     return l2esz;
434   }
435   static jint array_layout_helper(jint tag, int hsize, BasicType etype, int log2_esize) {
436     return (tag        << _lh_array_tag_shift)
437       |    (hsize      << _lh_header_size_shift)
438       |    ((int)etype << _lh_element_type_shift)
439       |    (log2_esize << _lh_log2_element_size_shift);
440   }
441   static jint instance_layout_helper(jint size, bool slow_path_flag) {
442     return (size << LogBytesPerWord)
443       |    (slow_path_flag ? _lh_instance_slow_path_bit : 0);
444   }
445   static int layout_helper_to_size_helper(jint lh) {
446     assert(lh > (jint)_lh_neutral_value, "must be instance");
447     // Note that the following expression discards _lh_instance_slow_path_bit.
448     return lh >> LogBytesPerWord;
449   }
450   // Out-of-line version computes everything based on the etype:
451   static jint array_layout_helper(BasicType etype);
452 
453   // What is the maximum number of primary superclasses any klass can have?
454   static juint primary_super_limit()         { return _primary_super_limit; }
455 
456   // vtables
457   klassVtable vtable() const;
458   int vtable_length() const { return _vtable_len; }
459 
460   // subclass check
461   bool is_subclass_of(const Klass* k) const;
462   // subtype check: true if is_subclass_of, or if k is interface and receiver implements it
463   bool is_subtype_of(Klass* k) const {
464     juint    off = k->super_check_offset();
465     Klass* sup = *(Klass**)( (address)this + off );
466     const juint secondary_offset = in_bytes(secondary_super_cache_offset());
467     if (sup == k) {
468       return true;
469     } else if (off != secondary_offset) {
470       return false;
471     } else {
472       return search_secondary_supers(k);
473     }
474   }
475 
476   bool search_secondary_supers(Klass* k) const;
477 
478   // Find LCA in class hierarchy
479   Klass *LCA( Klass *k );
480 
481   // Check whether reflection/jni/jvm code is allowed to instantiate this class;
482   // if not, throw either an Error or an Exception.
483   virtual void check_valid_for_instantiation(bool throwError, TRAPS);
484 
485   // array copying
486   virtual void  copy_array(arrayOop s, int src_pos, arrayOop d, int dst_pos, int length, TRAPS);
487 
488   // tells if the class should be initialized
489   virtual bool should_be_initialized() const    { return false; }
490   // initializes the klass
491   virtual void initialize(TRAPS);
492   virtual Klass* find_field(Symbol* name, Symbol* signature, fieldDescriptor* fd) const;
493   virtual Method* uncached_lookup_method(const Symbol* name, const Symbol* signature,
494                                          OverpassLookupMode overpass_mode,
495                                          PrivateLookupMode = PrivateLookupMode::find) const;
496  public:
497   Method* lookup_method(const Symbol* name, const Symbol* signature) const {
498     return uncached_lookup_method(name, signature, OverpassLookupMode::find);
499   }
500 
501   // array class with specific rank
502   virtual Klass* array_klass(int rank, TRAPS) = 0;
503 
504   // array class with this klass as element type
505   virtual Klass* array_klass(TRAPS) = 0;
506 
507   // These will return NULL instead of allocating on the heap:
508   virtual Klass* array_klass_or_null(int rank) = 0;
509   virtual Klass* array_klass_or_null() = 0;
510 
511   virtual oop protection_domain() const = 0;
512 
513   oop class_loader() const;
514 
515   inline oop klass_holder() const;
516 
517  protected:
518 
519   // Error handling when length > max_length or length < 0
520   static void check_array_allocation_length(int length, int max_length, TRAPS);
521 
522   void set_vtable_length(int len) { _vtable_len= len; }
523 
524   vtableEntry* start_of_vtable() const;
525   void restore_unshareable_info(ClassLoaderData* loader_data, Handle protection_domain, TRAPS);
526  public:
527   Method* method_at_vtable(int index);
528 
529   static ByteSize vtable_start_offset();
530   static ByteSize vtable_length_offset() {
531     return byte_offset_of(Klass, _vtable_len);
532   }
533 
534   // CDS support - remove and restore oops from metadata. Oops are not shared.
535   virtual void remove_unshareable_info();
536   virtual void remove_java_mirror();
537 
538   bool is_unshareable_info_restored() const {
539     assert(is_shared(), "use this for shared classes only");
540     if (has_archived_mirror_index()) {
541       // _java_mirror is not a valid OopHandle but rather an encoded reference in the shared heap
542       return false;
543     } else if (_java_mirror.ptr_raw() == NULL) {
544       return false;
545     } else {
546       return true;
547     }
548   }
549 
550  public:
551   // ALL FUNCTIONS BELOW THIS POINT ARE DISPATCHED FROM AN OOP
552   // These functions describe behavior for the oop not the KLASS.
553 
554   // actual oop size of obj in memory in word size.
555   virtual size_t oop_size(oop obj) const = 0;
556 
557   // Size of klass in word size.
558   virtual int size() const = 0;
559 
560   // Returns the Java name for a class (Resource allocated)
561   // For arrays, this returns the name of the element with a leading '['.
562   // For classes, this returns the name with the package separators
563   //     turned into '.'s.
564   const char* external_name() const;
565   // Returns the name for a class (Resource allocated) as the class
566   // would appear in a signature.
567   // For arrays, this returns the name of the element with a leading '['.
568   // For classes, this returns the name with a leading 'L' and a trailing ';'
569   //     and the package separators as '/'.
570   virtual const char* signature_name() const;
571 
572   const char* joint_in_module_of_loader(const Klass* class2, bool include_parent_loader = false) const;
573   const char* class_in_module_of_loader(bool use_are = false, bool include_parent_loader = false) const;
574 
575   // Returns "interface", "abstract class" or "class".
576   const char* external_kind() const;
577 
578   // type testing operations
579 #ifdef ASSERT
580  protected:
581   virtual bool is_instance_klass_slow()     const { return false; }
582   virtual bool is_array_klass_slow()        const { return false; }
583   virtual bool is_objArray_klass_slow()     const { return false; }
584   virtual bool is_typeArray_klass_slow()    const { return false; }
585 #endif // ASSERT
586  public:
587 
588   // Fast non-virtual versions
589   #ifndef ASSERT
590   #define assert_same_query(xval, xcheck) xval
591   #else
592  private:
593   static bool assert_same_query(bool xval, bool xslow) {
594     assert(xval == xslow, "slow and fast queries agree");
595     return xval;
596   }
597  public:
598   #endif
599   inline  bool is_instance_klass()            const { return assert_same_query(
600                                                       layout_helper_is_instance(layout_helper()),
601                                                       is_instance_klass_slow()); }
602   inline  bool is_array_klass()               const { return assert_same_query(
603                                                     layout_helper_is_array(layout_helper()),
604                                                     is_array_klass_slow()); }
605   inline  bool is_objArray_klass()            const { return assert_same_query(
606                                                     layout_helper_is_objArray(layout_helper()),
607                                                     is_objArray_klass_slow()); }
608   inline  bool is_typeArray_klass()           const { return assert_same_query(
609                                                     layout_helper_is_typeArray(layout_helper()),
610                                                     is_typeArray_klass_slow()); }
611   #undef assert_same_query
612 
613   // Access flags
614   AccessFlags access_flags() const         { return _access_flags;  }
615   void set_access_flags(AccessFlags flags) { _access_flags = flags; }
616 
617   bool is_public() const                { return _access_flags.is_public(); }
618   bool is_final() const                 { return _access_flags.is_final(); }
619   bool is_interface() const             { return _access_flags.is_interface(); }
620   bool is_abstract() const              { return _access_flags.is_abstract(); }
621   bool is_super() const                 { return _access_flags.is_super(); }
622   bool is_synthetic() const             { return _access_flags.is_synthetic(); }
623   void set_is_synthetic()               { _access_flags.set_is_synthetic(); }
624   bool has_finalizer() const            { return _access_flags.has_finalizer(); }
625   bool has_final_method() const         { return _access_flags.has_final_method(); }
626   void set_has_finalizer()              { _access_flags.set_has_finalizer(); }
627   void set_has_final_method()           { _access_flags.set_has_final_method(); }
628   bool has_vanilla_constructor() const  { return _access_flags.has_vanilla_constructor(); }
629   void set_has_vanilla_constructor()    { _access_flags.set_has_vanilla_constructor(); }
630   bool has_miranda_methods () const     { return access_flags().has_miranda_methods(); }
631   void set_has_miranda_methods()        { _access_flags.set_has_miranda_methods(); }
632   bool is_shared() const                { return access_flags().is_shared_class(); } // shadows MetaspaceObj::is_shared)()
633   void set_is_shared()                  { _access_flags.set_is_shared_class(); }
634   bool is_hidden() const                { return access_flags().is_hidden_class(); }
635   void set_is_hidden()                  { _access_flags.set_is_hidden_class(); }
636   bool is_value_based()                 { return _access_flags.is_value_based_class(); }
637   void set_is_value_based()             { _access_flags.set_is_value_based_class(); }
638 
639   inline bool is_non_strong_hidden() const;
640 
641   bool is_cloneable() const;
642   void set_is_cloneable();
643 
644   markWord prototype_header() const      { return _prototype_header; }
645   inline void set_prototype_header(markWord header);
646   static ByteSize prototype_header_offset() { return in_ByteSize(offset_of(Klass, _prototype_header)); }
647 
648   JFR_ONLY(DEFINE_TRACE_ID_METHODS;)
649 
650   virtual void metaspace_pointers_do(MetaspaceClosure* iter);
651   virtual MetaspaceObj::Type type() const { return ClassType; }
652 
653   inline bool is_loader_alive() const;
654 
655   void clean_subklass();
656 
657   static void clean_weak_klass_links(bool unloading_occurred, bool clean_alive_klasses = true);
658   static void clean_subklass_tree() {
659     clean_weak_klass_links(/*unloading_occurred*/ true , /* clean_alive_klasses */ false);
660   }
661 
662   // Return self, except for abstract classes with exactly 1
663   // implementor.  Then return the 1 concrete implementation.
664   Klass *up_cast_abstract();
665 
666   // klass name
667   Symbol* name() const                   { return _name; }
668   void set_name(Symbol* n);
669 
670   virtual void release_C_heap_structures(bool release_constant_pool = true);
671 
672  public:
673   virtual jint compute_modifier_flags() const = 0;
674 
675   // JVMTI support
676   virtual jint jvmti_class_status() const;
677 
678   // Printing
679   virtual void print_on(outputStream* st) const;
680 
681   virtual void oop_print_value_on(oop obj, outputStream* st);
682   virtual void oop_print_on      (oop obj, outputStream* st);
683 
684   virtual const char* internal_name() const = 0;
685 
686   // Verification
687   virtual void verify_on(outputStream* st);
688   void verify() { verify_on(tty); }
689 
690 #ifndef PRODUCT
691   bool verify_vtable_index(int index);
692 #endif
693 
694   virtual void oop_verify_on(oop obj, outputStream* st);
695 
696   // for error reporting
697   static bool is_valid(Klass* k);
698 };
699 
700 #endif // SHARE_OOPS_KLASS_HPP