1 /*
  2  * Copyright (c) 1997, 2020, 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
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 24 
 25 #ifndef SHARE_OOPS_KLASS_HPP
 26 #define SHARE_OOPS_KLASS_HPP
 27 
 28 #include "classfile/classLoaderData.hpp"
 29 #include "memory/iterator.hpp"
 30 #include "memory/memRegion.hpp"
 31 #include "oops/markWord.hpp"
 32 #include "oops/metadata.hpp"
 33 #include "oops/oop.hpp"
 34 #include "oops/oopHandle.hpp"
 35 #include "utilities/accessFlags.hpp"
 36 #include "utilities/macros.hpp"
 37 #if INCLUDE_JFR
 38 #include "jfr/support/jfrTraceIdExtension.hpp"
 39 #endif
 40 
 41 // Klass IDs for all subclasses of Klass
 42 enum KlassID {
 43   InstanceKlassID,
 44   InstanceRefKlassID,
 45   InstanceMirrorKlassID,
 46   InstanceClassLoaderKlassID,
 47   TypeArrayKlassID,
 48   ObjArrayKlassID
 49 };
 50 
 51 const uint KLASS_ID_COUNT = 6;
 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 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   // Biased locking implementation and statistics
163   // (the 64-bit chunk goes first, to avoid some fragmentation)
164   jlong    _last_biased_lock_bulk_revocation_time;
165   markWord _prototype_header;   // Used when biased locking is both enabled and disabled for this type
166   jint     _biased_lock_revocation_count;
167 
168 private:
169   // This is an index into FileMapHeader::_shared_path_table[], to
170   // associate this class with the JAR file where it's loaded from during
171   // dump time. If a class is not loaded from the shared archive, this field is
172   // -1.
173   jshort _shared_class_path_index;
174 
175 #if INCLUDE_CDS
176   // Flags of the current shared class.
177   u2     _shared_class_flags;
178   enum {
179     _archived_lambda_proxy_is_available = 2
180   };
181 #endif
182 
183   CDS_JAVA_HEAP_ONLY(int _archived_mirror_index;)
184 
185 protected:
186 
187   // Constructor
188   Klass(KlassID id);
189   Klass() : _id(KlassID(-1)) { assert(DumpSharedSpaces || UseSharedSpaces, "only for cds"); }
190 
191   void* operator new(size_t size, ClassLoaderData* loader_data, size_t word_size, TRAPS) throw();
192 
193  public:
194   int id() { return _id; }
195 
196   enum class DefaultsLookupMode { find, skip };
197   enum class OverpassLookupMode { find, skip };
198   enum class StaticLookupMode   { find, skip };
199   enum class PrivateLookupMode  { find, skip };
200 
201   virtual bool is_klass() const { return true; }
202 
203   // super() cannot be InstanceKlass* -- Java arrays are covariant, and _super is used
204   // to implement that. NB: the _super of "[Ljava/lang/Integer;" is "[Ljava/lang/Number;"
205   // If this is not what your code expects, you're probably looking for Klass::java_super().
206   Klass* super() const               { return _super; }
207   void set_super(Klass* k)           { _super = k; }
208 
209   // initializes _super link, _primary_supers & _secondary_supers arrays
210   void initialize_supers(Klass* k, Array<InstanceKlass*>* transitive_interfaces, TRAPS);
211 
212   // klass-specific helper for initializing _secondary_supers
213   virtual GrowableArray<Klass*>* compute_secondary_supers(int num_extra_slots,
214                                                           Array<InstanceKlass*>* transitive_interfaces);
215 
216   // java_super is the Java-level super type as specified by Class.getSuperClass.
217   virtual InstanceKlass* java_super() const  { return NULL; }
218 
219   juint    super_check_offset() const  { return _super_check_offset; }
220   void set_super_check_offset(juint o) { _super_check_offset = o; }
221 
222   Klass* secondary_super_cache() const     { return _secondary_super_cache; }
223   void set_secondary_super_cache(Klass* k) { _secondary_super_cache = k; }
224 
225   Array<Klass*>* secondary_supers() const { return _secondary_supers; }
226   void set_secondary_supers(Array<Klass*>* k) { _secondary_supers = k; }
227 
228   // Return the element of the _super chain of the given depth.
229   // If there is no such element, return either NULL or this.
230   Klass* primary_super_of_depth(juint i) const {
231     assert(i < primary_super_limit(), "oob");
232     Klass* super = _primary_supers[i];
233     assert(super == NULL || super->super_depth() == i, "correct display");
234     return super;
235   }
236 
237   // Can this klass be a primary super?  False for interfaces and arrays of
238   // interfaces.  False also for arrays or classes with long super chains.
239   bool can_be_primary_super() const {
240     const juint secondary_offset = in_bytes(secondary_super_cache_offset());
241     return super_check_offset() != secondary_offset;
242   }
243   virtual bool can_be_primary_super_slow() const;
244 
245   // Returns number of primary supers; may be a number in the inclusive range [0, primary_super_limit].
246   juint super_depth() const {
247     if (!can_be_primary_super()) {
248       return primary_super_limit();
249     } else {
250       juint d = (super_check_offset() - in_bytes(primary_supers_offset())) / sizeof(Klass*);
251       assert(d < primary_super_limit(), "oob");
252       assert(_primary_supers[d] == this, "proper init");
253       return d;
254     }
255   }
256 
257   // java mirror
258   oop java_mirror() const;
259   oop java_mirror_no_keepalive() const;
260   void set_java_mirror(Handle m);
261 
262   oop archived_java_mirror() NOT_CDS_JAVA_HEAP_RETURN_(NULL);
263   void set_archived_java_mirror(oop m) NOT_CDS_JAVA_HEAP_RETURN;
264 
265   // Temporary mirror switch used by RedefineClasses
266   void replace_java_mirror(oop mirror);
267 
268   // Set java mirror OopHandle to NULL for CDS
269   // This leaves the OopHandle in the CLD, but that's ok, you can't release them.
270   void clear_java_mirror_handle() { _java_mirror = OopHandle(); }
271 
272   // modifier flags
273   jint modifier_flags() const          { return _modifier_flags; }
274   void set_modifier_flags(jint flags)  { _modifier_flags = flags; }
275 
276   // size helper
277   int layout_helper() const            { return _layout_helper; }
278   void set_layout_helper(int lh)       { _layout_helper = lh; }
279 
280   // Note: for instances layout_helper() may include padding.
281   // Use InstanceKlass::contains_field_offset to classify field offsets.
282 
283   // sub/superklass links
284   Klass* subklass(bool log = false) const;
285   Klass* next_sibling(bool log = false) const;
286 
287   InstanceKlass* superklass() const;
288   void append_to_sibling_list();           // add newly created receiver to superklass' subklass list
289 
290   void set_next_link(Klass* k) { _next_link = k; }
291   Klass* next_link() const { return _next_link; }   // The next klass defined by the class loader.
292   Klass** next_link_addr() { return &_next_link; }
293 
294   // class loader data
295   ClassLoaderData* class_loader_data() const               { return _class_loader_data; }
296   void set_class_loader_data(ClassLoaderData* loader_data) {  _class_loader_data = loader_data; }
297 
298   int shared_classpath_index() const   {
299     return _shared_class_path_index;
300   };
301 
302   void set_shared_classpath_index(int index) {
303     _shared_class_path_index = index;
304   };
305 
306   bool has_archived_mirror_index() const {
307     CDS_JAVA_HEAP_ONLY(return _archived_mirror_index >= 0);
308     NOT_CDS_JAVA_HEAP( return false);
309   }
310 
311   void clear_archived_mirror_index() NOT_CDS_JAVA_HEAP_RETURN;
312 
313   void set_lambda_proxy_is_available() {
314     CDS_ONLY(_shared_class_flags |= _archived_lambda_proxy_is_available;)
315   }
316   void clear_lambda_proxy_is_available() {
317     CDS_ONLY(_shared_class_flags &= ~_archived_lambda_proxy_is_available;)
318   }
319   bool lambda_proxy_is_available() const {
320     CDS_ONLY(return (_shared_class_flags & _archived_lambda_proxy_is_available) != 0;)
321     NOT_CDS(return false;)
322   }
323 
324   // Obtain the module or package for this class
325   virtual ModuleEntry* module() const = 0;
326   virtual PackageEntry* package() const = 0;
327 
328  protected:                                // internal accessors
329   void     set_subklass(Klass* s);
330   void     set_next_sibling(Klass* s);
331 
332  public:
333 
334   // Compiler support
335   static ByteSize super_offset()                 { return in_ByteSize(offset_of(Klass, _super)); }
336   static ByteSize super_check_offset_offset()    { return in_ByteSize(offset_of(Klass, _super_check_offset)); }
337   static ByteSize primary_supers_offset()        { return in_ByteSize(offset_of(Klass, _primary_supers)); }
338   static ByteSize secondary_super_cache_offset() { return in_ByteSize(offset_of(Klass, _secondary_super_cache)); }
339   static ByteSize secondary_supers_offset()      { return in_ByteSize(offset_of(Klass, _secondary_supers)); }
340   static ByteSize java_mirror_offset()           { return in_ByteSize(offset_of(Klass, _java_mirror)); }
341   static ByteSize class_loader_data_offset()     { return in_ByteSize(offset_of(Klass, _class_loader_data)); }
342   static ByteSize modifier_flags_offset()        { return in_ByteSize(offset_of(Klass, _modifier_flags)); }
343   static ByteSize layout_helper_offset()         { return in_ByteSize(offset_of(Klass, _layout_helper)); }
344   static ByteSize access_flags_offset()          { return in_ByteSize(offset_of(Klass, _access_flags)); }
345 
346   // Unpacking layout_helper:
347   static const int _lh_neutral_value           = 0;  // neutral non-array non-instance value
348   static const int _lh_instance_slow_path_bit  = 0x01;
349   static const int _lh_log2_element_size_shift = BitsPerByte*0;
350   static const int _lh_log2_element_size_mask  = BitsPerLong-1;
351   static const int _lh_element_type_shift      = BitsPerByte*1;
352   static const int _lh_element_type_mask       = right_n_bits(BitsPerByte);  // shifted mask
353   static const int _lh_header_size_shift       = BitsPerByte*2;
354   static const int _lh_header_size_mask        = right_n_bits(BitsPerByte);  // shifted mask
355   static const int _lh_array_tag_bits          = 2;
356   static const int _lh_array_tag_shift         = BitsPerInt - _lh_array_tag_bits;
357   static const int _lh_array_tag_obj_value     = ~0x01;   // 0x80000000 >> 30
358 
359   static const unsigned int _lh_array_tag_type_value = 0Xffffffff; // ~0x00,  // 0xC0000000 >> 30
360 
361   static int layout_helper_size_in_bytes(jint lh) {
362     assert(lh > (jint)_lh_neutral_value, "must be instance");
363     return (int) lh & ~_lh_instance_slow_path_bit;
364   }
365   static bool layout_helper_needs_slow_path(jint lh) {
366     assert(lh > (jint)_lh_neutral_value, "must be instance");
367     return (lh & _lh_instance_slow_path_bit) != 0;
368   }
369   static bool layout_helper_is_instance(jint lh) {
370     return (jint)lh > (jint)_lh_neutral_value;
371   }
372   static bool layout_helper_is_array(jint lh) {
373     return (jint)lh < (jint)_lh_neutral_value;
374   }
375   static bool layout_helper_is_typeArray(jint lh) {
376     // _lh_array_tag_type_value == (lh >> _lh_array_tag_shift);
377     return (juint)lh >= (juint)(_lh_array_tag_type_value << _lh_array_tag_shift);
378   }
379   static bool layout_helper_is_objArray(jint lh) {
380     // _lh_array_tag_obj_value == (lh >> _lh_array_tag_shift);
381     return (jint)lh < (jint)(_lh_array_tag_type_value << _lh_array_tag_shift);
382   }
383   static int layout_helper_header_size(jint lh) {
384     assert(lh < (jint)_lh_neutral_value, "must be array");
385     int hsize = (lh >> _lh_header_size_shift) & _lh_header_size_mask;
386     assert(hsize > 0 && hsize < (int)sizeof(oopDesc)*3, "sanity");
387     return hsize;
388   }
389   static BasicType layout_helper_element_type(jint lh) {
390     assert(lh < (jint)_lh_neutral_value, "must be array");
391     int btvalue = (lh >> _lh_element_type_shift) & _lh_element_type_mask;
392     assert(btvalue >= T_BOOLEAN && btvalue <= T_OBJECT, "sanity");
393     return (BasicType) btvalue;
394   }
395 
396   // Want a pattern to quickly diff against layout header in register
397   // find something less clever!
398   static int layout_helper_boolean_diffbit() {
399     jint zlh = array_layout_helper(T_BOOLEAN);
400     jint blh = array_layout_helper(T_BYTE);
401     assert(zlh != blh, "array layout helpers must differ");
402     int diffbit = 1;
403     while ((diffbit & (zlh ^ blh)) == 0 && (diffbit & zlh) == 0) {
404       diffbit <<= 1;
405       assert(diffbit != 0, "make sure T_BOOLEAN has a different bit than T_BYTE");
406     }
407     return diffbit;
408   }
409 
410   static int layout_helper_log2_element_size(jint lh) {
411     assert(lh < (jint)_lh_neutral_value, "must be array");
412     int l2esz = (lh >> _lh_log2_element_size_shift) & _lh_log2_element_size_mask;
413     assert(l2esz <= LogBytesPerLong,
414            "sanity. l2esz: 0x%x for lh: 0x%x", (uint)l2esz, (uint)lh);
415     return l2esz;
416   }
417   static jint array_layout_helper(jint tag, int hsize, BasicType etype, int log2_esize) {
418     return (tag        << _lh_array_tag_shift)
419       |    (hsize      << _lh_header_size_shift)
420       |    ((int)etype << _lh_element_type_shift)
421       |    (log2_esize << _lh_log2_element_size_shift);
422   }
423   static jint instance_layout_helper(jint size, bool slow_path_flag) {
424     return (size << LogBytesPerWord)
425       |    (slow_path_flag ? _lh_instance_slow_path_bit : 0);
426   }
427   static int layout_helper_to_size_helper(jint lh) {
428     assert(lh > (jint)_lh_neutral_value, "must be instance");
429     // Note that the following expression discards _lh_instance_slow_path_bit.
430     return lh >> LogBytesPerWord;
431   }
432   // Out-of-line version computes everything based on the etype:
433   static jint array_layout_helper(BasicType etype);
434 
435   // What is the maximum number of primary superclasses any klass can have?
436   static juint primary_super_limit()         { return _primary_super_limit; }
437 
438   // vtables
439   klassVtable vtable() const;
440   int vtable_length() const { return _vtable_len; }
441 
442   // subclass check
443   bool is_subclass_of(const Klass* k) const;
444   // subtype check: true if is_subclass_of, or if k is interface and receiver implements it
445   bool is_subtype_of(Klass* k) const {
446     juint    off = k->super_check_offset();
447     Klass* sup = *(Klass**)( (address)this + off );
448     const juint secondary_offset = in_bytes(secondary_super_cache_offset());
449     if (sup == k) {
450       return true;
451     } else if (off != secondary_offset) {
452       return false;
453     } else {
454       return search_secondary_supers(k);
455     }
456   }
457 
458   bool search_secondary_supers(Klass* k) const;
459 
460   // Find LCA in class hierarchy
461   Klass *LCA( Klass *k );
462 
463   // Check whether reflection/jni/jvm code is allowed to instantiate this class;
464   // if not, throw either an Error or an Exception.
465   virtual void check_valid_for_instantiation(bool throwError, TRAPS);
466 
467   // array copying
468   virtual void  copy_array(arrayOop s, int src_pos, arrayOop d, int dst_pos, int length, TRAPS);
469 
470   // tells if the class should be initialized
471   virtual bool should_be_initialized() const    { return false; }
472   // initializes the klass
473   virtual void initialize(TRAPS);
474   virtual Klass* find_field(Symbol* name, Symbol* signature, fieldDescriptor* fd) const;
475   virtual Method* uncached_lookup_method(const Symbol* name, const Symbol* signature,
476                                          OverpassLookupMode overpass_mode,
477                                          PrivateLookupMode = PrivateLookupMode::find) const;
478  public:
479   Method* lookup_method(const Symbol* name, const Symbol* signature) const {
480     return uncached_lookup_method(name, signature, OverpassLookupMode::find);
481   }
482 
483   // array class with specific rank
484   Klass* array_klass(int rank, TRAPS)         {  return array_klass_impl(false, rank, THREAD); }
485 
486   // array class with this klass as element type
487   Klass* array_klass(TRAPS)                   {  return array_klass_impl(false, THREAD); }
488 
489   // These will return NULL instead of allocating on the heap:
490   // NB: these can block for a mutex, like other functions with TRAPS arg.
491   Klass* array_klass_or_null(int rank);
492   Klass* array_klass_or_null();
493 
494   virtual oop protection_domain() const = 0;
495 
496   oop class_loader() const;
497 
498   // This loads the klass's holder as a phantom. This is useful when a weak Klass
499   // pointer has been "peeked" and then must be kept alive before it may
500   // be used safely.  All uses of klass_holder need to apply the appropriate barriers,
501   // except during GC.
502   oop klass_holder() const { return class_loader_data()->holder_phantom(); }
503 
504  protected:
505   virtual Klass* array_klass_impl(bool or_null, int rank, TRAPS);
506   virtual Klass* array_klass_impl(bool or_null, TRAPS);
507 
508   // Error handling when length > max_length or length < 0
509   static void check_array_allocation_length(int length, int max_length, TRAPS);
510 
511   void set_vtable_length(int len) { _vtable_len= len; }
512 
513   vtableEntry* start_of_vtable() const;
514   void restore_unshareable_info(ClassLoaderData* loader_data, Handle protection_domain, TRAPS);
515  public:
516   Method* method_at_vtable(int index);
517 
518   static ByteSize vtable_start_offset();
519   static ByteSize vtable_length_offset() {
520     return byte_offset_of(Klass, _vtable_len);
521   }
522 
523   // CDS support - remove and restore oops from metadata. Oops are not shared.
524   virtual void remove_unshareable_info();
525   virtual void remove_java_mirror();
526 
527   bool is_unshareable_info_restored() const {
528     assert(is_shared(), "use this for shared classes only");
529     if (has_archived_mirror_index()) {
530       // _java_mirror is not a valid OopHandle but rather an encoded reference in the shared heap
531       return false;
532     } else if (_java_mirror.ptr_raw() == NULL) {
533       return false;
534     } else {
535       return true;
536     }
537   }
538 
539  public:
540   // ALL FUNCTIONS BELOW THIS POINT ARE DISPATCHED FROM AN OOP
541   // These functions describe behavior for the oop not the KLASS.
542 
543   // actual oop size of obj in memory
544   virtual int oop_size(oop obj) const = 0;
545 
546   // Size of klass in word size.
547   virtual int size() const = 0;
548 
549   // Returns the Java name for a class (Resource allocated)
550   // For arrays, this returns the name of the element with a leading '['.
551   // For classes, this returns the name with the package separators
552   //     turned into '.'s.
553   const char* external_name() const;
554   // Returns the name for a class (Resource allocated) as the class
555   // would appear in a signature.
556   // For arrays, this returns the name of the element with a leading '['.
557   // For classes, this returns the name with a leading 'L' and a trailing ';'
558   //     and the package separators as '/'.
559   virtual const char* signature_name() const;
560 
561   const char* joint_in_module_of_loader(const Klass* class2, bool include_parent_loader = false) const;
562   const char* class_in_module_of_loader(bool use_are = false, bool include_parent_loader = false) const;
563 
564   // Returns "interface", "abstract class" or "class".
565   const char* external_kind() const;
566 
567   // type testing operations
568 #ifdef ASSERT
569  protected:
570   virtual bool is_instance_klass_slow()     const { return false; }
571   virtual bool is_array_klass_slow()        const { return false; }
572   virtual bool is_objArray_klass_slow()     const { return false; }
573   virtual bool is_typeArray_klass_slow()    const { return false; }
574 #endif // ASSERT
575  public:
576 
577   // Fast non-virtual versions
578   #ifndef ASSERT
579   #define assert_same_query(xval, xcheck) xval
580   #else
581  private:
582   static bool assert_same_query(bool xval, bool xslow) {
583     assert(xval == xslow, "slow and fast queries agree");
584     return xval;
585   }
586  public:
587   #endif
588   inline  bool is_instance_klass()            const { return assert_same_query(
589                                                       layout_helper_is_instance(layout_helper()),
590                                                       is_instance_klass_slow()); }
591   inline  bool is_array_klass()               const { return assert_same_query(
592                                                     layout_helper_is_array(layout_helper()),
593                                                     is_array_klass_slow()); }
594   inline  bool is_objArray_klass()            const { return assert_same_query(
595                                                     layout_helper_is_objArray(layout_helper()),
596                                                     is_objArray_klass_slow()); }
597   inline  bool is_typeArray_klass()           const { return assert_same_query(
598                                                     layout_helper_is_typeArray(layout_helper()),
599                                                     is_typeArray_klass_slow()); }
600   #undef assert_same_query
601 
602   // Access flags
603   AccessFlags access_flags() const         { return _access_flags;  }
604   void set_access_flags(AccessFlags flags) { _access_flags = flags; }
605 
606   bool is_public() const                { return _access_flags.is_public(); }
607   bool is_final() const                 { return _access_flags.is_final(); }
608   bool is_interface() const             { return _access_flags.is_interface(); }
609   bool is_abstract() const              { return _access_flags.is_abstract(); }
610   bool is_super() const                 { return _access_flags.is_super(); }
611   bool is_synthetic() const             { return _access_flags.is_synthetic(); }
612   void set_is_synthetic()               { _access_flags.set_is_synthetic(); }
613   bool has_finalizer() const            { return _access_flags.has_finalizer(); }
614   bool has_final_method() const         { return _access_flags.has_final_method(); }
615   void set_has_finalizer()              { _access_flags.set_has_finalizer(); }
616   void set_has_final_method()           { _access_flags.set_has_final_method(); }
617   bool has_vanilla_constructor() const  { return _access_flags.has_vanilla_constructor(); }
618   void set_has_vanilla_constructor()    { _access_flags.set_has_vanilla_constructor(); }
619   bool has_miranda_methods () const     { return access_flags().has_miranda_methods(); }
620   void set_has_miranda_methods()        { _access_flags.set_has_miranda_methods(); }
621   bool is_shared() const                { return access_flags().is_shared_class(); } // shadows MetaspaceObj::is_shared)()
622   void set_is_shared()                  { _access_flags.set_is_shared_class(); }
623   bool is_hidden() const                { return access_flags().is_hidden_class(); }
624   void set_is_hidden()                  { _access_flags.set_is_hidden_class(); }
625   bool is_non_strong_hidden() const     { return access_flags().is_hidden_class() &&
626                                           class_loader_data()->has_class_mirror_holder(); }
627   bool is_box() const                   { return access_flags().is_box_class(); }
628   void set_is_box()                     { _access_flags.set_is_box_class(); }
629 
630   bool is_cloneable() const;
631   void set_is_cloneable();
632 
633   // Biased locking support
634   // Note: the prototype header is always set up to be at least the
635   // prototype markWord. If biased locking is enabled it may further be
636   // biasable and have an epoch.
637   markWord prototype_header() const      { return _prototype_header; }
638 
639   // NOTE: once instances of this klass are floating around in the
640   // system, this header must only be updated at a safepoint.
641   // NOTE 2: currently we only ever set the prototype header to the
642   // biasable prototype for instanceKlasses. There is no technical
643   // reason why it could not be done for arrayKlasses aside from
644   // wanting to reduce the initial scope of this optimization. There
645   // are potential problems in setting the bias pattern for
646   // JVM-internal oops.
647   inline void set_prototype_header(markWord header);
648   static ByteSize prototype_header_offset() { return in_ByteSize(offset_of(Klass, _prototype_header)); }
649 
650   int  biased_lock_revocation_count() const { return (int) _biased_lock_revocation_count; }
651   // Atomically increments biased_lock_revocation_count and returns updated value
652   int atomic_incr_biased_lock_revocation_count();
653   void set_biased_lock_revocation_count(int val) { _biased_lock_revocation_count = (jint) val; }
654   jlong last_biased_lock_bulk_revocation_time() { return _last_biased_lock_bulk_revocation_time; }
655   void  set_last_biased_lock_bulk_revocation_time(jlong cur_time) { _last_biased_lock_bulk_revocation_time = cur_time; }
656 
657   JFR_ONLY(DEFINE_TRACE_ID_METHODS;)
658 
659   virtual void metaspace_pointers_do(MetaspaceClosure* iter);
660   virtual MetaspaceObj::Type type() const { return ClassType; }
661 
662   // Iff the class loader (or mirror for unsafe anonymous classes) is alive the
663   // Klass is considered alive. This is safe to call before the CLD is marked as
664   // unloading, and hence during concurrent class unloading.
665   bool is_loader_alive() const { return class_loader_data()->is_alive(); }
666 
667   void clean_subklass();
668 
669   static void clean_weak_klass_links(bool unloading_occurred, bool clean_alive_klasses = true);
670   static void clean_subklass_tree() {
671     clean_weak_klass_links(/*unloading_occurred*/ true , /* clean_alive_klasses */ false);
672   }
673 
674   virtual void array_klasses_do(void f(Klass* k)) {}
675 
676   // Return self, except for abstract classes with exactly 1
677   // implementor.  Then return the 1 concrete implementation.
678   Klass *up_cast_abstract();
679 
680   // klass name
681   Symbol* name() const                   { return _name; }
682   void set_name(Symbol* n);
683 
684   virtual void release_C_heap_structures();
685 
686  public:
687   // jvm support
688   virtual jint compute_modifier_flags(TRAPS) const;
689 
690   // JVMTI support
691   virtual jint jvmti_class_status() const;
692 
693   // Printing
694   virtual void print_on(outputStream* st) const;
695 
696   virtual void oop_print_value_on(oop obj, outputStream* st);
697   virtual void oop_print_on      (oop obj, outputStream* st);
698 
699   virtual const char* internal_name() const = 0;
700 
701   // Verification
702   virtual void verify_on(outputStream* st);
703   void verify() { verify_on(tty); }
704 
705 #ifndef PRODUCT
706   bool verify_vtable_index(int index);
707 #endif
708 
709   virtual void oop_verify_on(oop obj, outputStream* st);
710 
711   // for error reporting
712   static bool is_valid(Klass* k);
713 };
714 
715 #endif // SHARE_OOPS_KLASS_HPP