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