1 /*
  2  * Copyright (c) 1997, 2018, 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_VM_OOPS_KLASS_HPP
 26 #define SHARE_VM_OOPS_KLASS_HPP
 27 
 28 #include "classfile/classLoaderData.hpp"
 29 #include "memory/iterator.hpp"
 30 #include "memory/memRegion.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 fieldDescriptor;
 70 class KlassSizeStats;
 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   // The fields _super_check_offset, _secondary_super_cache, _secondary_supers
121   // and _primary_supers all help make fast subtype checks.  See big discussion
122   // in doc/server_compiler/checktype.txt
123   //
124   // Where to look to observe a supertype (it is &_secondary_super_cache for
125   // secondary supers, else is &_primary_supers[depth()].
126   juint       _super_check_offset;
127 
128   // Class name.  Instance classes: java/lang/String, etc.  Array classes: [I,
129   // [Ljava/lang/String;, etc.  Set to zero for all other kinds of classes.
130   Symbol*     _name;
131 
132   // Cache of last observed secondary supertype
133   Klass*      _secondary_super_cache;
134   // Array of all secondary supertypes
135   Array<Klass*>* _secondary_supers;
136   // Ordered list of all primary supertypes
137   Klass*      _primary_supers[_primary_super_limit];
138   // java/lang/Class instance mirroring this class
139   OopHandle _java_mirror;
140   // Superclass
141   Klass*      _super;
142   // First subclass (NULL if none); _subklass->next_sibling() is next one
143   Klass*      _subklass;
144   // Sibling link (or NULL); links all subklasses of a klass
145   Klass*      _next_sibling;
146 
147   // All klasses loaded by a class loader are chained through these links
148   Klass*      _next_link;
149 
150   // The VM's representation of the ClassLoader used to load this class.
151   // Provide access the corresponding instance java.lang.ClassLoader.
152   ClassLoaderData* _class_loader_data;
153 
154   jint        _modifier_flags;  // Processed access flags, for use by Class.getModifiers.
155   AccessFlags _access_flags;    // Access flags. The class/interface distinction is stored here.
156 
157   JFR_ONLY(DEFINE_TRACE_ID_FIELD;)
158 
159   // Biased locking implementation and statistics
160   // (the 64-bit chunk goes first, to avoid some fragmentation)
161   jlong    _last_biased_lock_bulk_revocation_time;
162   markOop  _prototype_header;   // Used when biased locking is both enabled and disabled for this type
163   jint     _biased_lock_revocation_count;
164 
165   // vtable length
166   int _vtable_len;
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     _has_raw_archived_mirror = 1,
180     _has_signer_and_not_archived = 1 << 2
181   };
182 #endif
183   // The _archived_mirror is set at CDS dump time pointing to the cached mirror
184   // in the open archive heap region when archiving java object is supported.
185   CDS_JAVA_HEAP_ONLY(narrowOop _archived_mirror;)
186 
187 protected:
188 
189   // Constructor
190   Klass(KlassID id);
191   Klass() : _id(KlassID(-1)) { assert(DumpSharedSpaces || UseSharedSpaces, "only for cds"); }
192 
193   void* operator new(size_t size, ClassLoaderData* loader_data, size_t word_size, TRAPS) throw();
194 
195  public:
196   int id() { return _id; }
197 
198   enum DefaultsLookupMode { find_defaults, skip_defaults };
199   enum OverpassLookupMode { find_overpass, skip_overpass };
200   enum StaticLookupMode   { find_static,   skip_static };
201   enum PrivateLookupMode  { find_private,  skip_private };
202 
203   bool is_klass() const volatile { return true; }
204 
205   // super() cannot be InstanceKlass* -- Java arrays are covariant, and _super is used
206   // to implement that. NB: the _super of "[Ljava/lang/Integer;" is "[Ljava/lang/Number;"
207   // If this is not what your code expects, you're probably looking for Klass::java_super().
208   Klass* super() const               { return _super; }
209   void set_super(Klass* k)           { _super = k; }
210 
211   // initializes _super link, _primary_supers & _secondary_supers arrays
212   void initialize_supers(Klass* k, Array<InstanceKlass*>* transitive_interfaces, TRAPS);
213 
214   // klass-specific helper for initializing _secondary_supers
215   virtual GrowableArray<Klass*>* compute_secondary_supers(int num_extra_slots,
216                                                           Array<InstanceKlass*>* transitive_interfaces);
217 
218   // java_super is the Java-level super type as specified by Class.getSuperClass.
219   virtual InstanceKlass* java_super() const  { return NULL; }
220 
221   juint    super_check_offset() const  { return _super_check_offset; }
222   void set_super_check_offset(juint o) { _super_check_offset = o; }
223 
224   Klass* secondary_super_cache() const     { return _secondary_super_cache; }
225   void set_secondary_super_cache(Klass* k) { _secondary_super_cache = k; }
226 
227   Array<Klass*>* secondary_supers() const { return _secondary_supers; }
228   void set_secondary_supers(Array<Klass*>* k) { _secondary_supers = k; }
229 
230   // Return the element of the _super chain of the given depth.
231   // If there is no such element, return either NULL or this.
232   Klass* primary_super_of_depth(juint i) const {
233     assert(i < primary_super_limit(), "oob");
234     Klass* super = _primary_supers[i];
235     assert(super == NULL || super->super_depth() == i, "correct display");
236     return super;
237   }
238 
239   // Can this klass be a primary super?  False for interfaces and arrays of
240   // interfaces.  False also for arrays or classes with long super chains.
241   bool can_be_primary_super() const {
242     const juint secondary_offset = in_bytes(secondary_super_cache_offset());
243     return super_check_offset() != secondary_offset;
244   }
245   virtual bool can_be_primary_super_slow() const;
246 
247   // Returns number of primary supers; may be a number in the inclusive range [0, primary_super_limit].
248   juint super_depth() const {
249     if (!can_be_primary_super()) {
250       return primary_super_limit();
251     } else {
252       juint d = (super_check_offset() - in_bytes(primary_supers_offset())) / sizeof(Klass*);
253       assert(d < primary_super_limit(), "oob");
254       assert(_primary_supers[d] == this, "proper init");
255       return d;
256     }
257   }
258 
259   // java mirror
260   oop java_mirror() const;
261   void set_java_mirror(Handle m);
262 
263   oop archived_java_mirror_raw() NOT_CDS_JAVA_HEAP_RETURN_(NULL); // no GC barrier
264   narrowOop archived_java_mirror_raw_narrow() NOT_CDS_JAVA_HEAP_RETURN_(0); // no GC barrier
265   void set_archived_java_mirror_raw(oop m) NOT_CDS_JAVA_HEAP_RETURN; // no GC barrier
266 
267   // Temporary mirror switch used by RedefineClasses
268   // Both mirrors are on the ClassLoaderData::_handles list already so no
269   // barriers are needed.
270   void set_java_mirror_handle(OopHandle mirror) { _java_mirror = mirror; }
271   OopHandle java_mirror_handle() const          {
272     return _java_mirror;
273   }
274 
275   // modifier flags
276   jint modifier_flags() const          { return _modifier_flags; }
277   void set_modifier_flags(jint flags)  { _modifier_flags = flags; }
278 
279   // size helper
280   int layout_helper() const            { return _layout_helper; }
281   void set_layout_helper(int lh)       { _layout_helper = lh; }
282 
283   // Note: for instances layout_helper() may include padding.
284   // Use InstanceKlass::contains_field_offset to classify field offsets.
285 
286   // sub/superklass links
287   Klass* subklass() const              { return _subklass; }
288   Klass* next_sibling() const          { return _next_sibling; }
289   InstanceKlass* superklass() const;
290   void append_to_sibling_list();           // add newly created receiver to superklass' subklass list
291 
292   void set_next_link(Klass* k) { _next_link = k; }
293   Klass* next_link() const { return _next_link; }   // The next klass defined by the class loader.
294 
295   // class loader data
296   ClassLoaderData* class_loader_data() const               { return _class_loader_data; }
297   void set_class_loader_data(ClassLoaderData* loader_data) {  _class_loader_data = loader_data; }
298 
299   int shared_classpath_index() const   {
300     return _shared_class_path_index;
301   };
302 
303   void set_shared_classpath_index(int index) {
304     _shared_class_path_index = index;
305   };
306 
307   void set_has_raw_archived_mirror() {
308     CDS_ONLY(_shared_class_flags |= _has_raw_archived_mirror;)
309   }
310   void clear_has_raw_archived_mirror() {
311     CDS_ONLY(_shared_class_flags &= ~_has_raw_archived_mirror;)
312   }
313   bool has_raw_archived_mirror() const {
314     CDS_ONLY(return (_shared_class_flags & _has_raw_archived_mirror) != 0;)
315     NOT_CDS(return false;)
316   }
317 #if INCLUDE_CDS
318   void set_has_signer_and_not_archived() {
319     _shared_class_flags |= _has_signer_and_not_archived;
320   }
321   bool has_signer_and_not_archived() const {
322     assert(DumpSharedSpaces, "dump time only");
323     return (_shared_class_flags & _has_signer_and_not_archived) != 0;
324   }
325 #endif // INCLUDE_CDS
326 
327   // Obtain the module or package for this class
328   virtual ModuleEntry* module() const = 0;
329   virtual PackageEntry* package() const = 0;
330 
331  protected:                                // internal accessors
332   void     set_subklass(Klass* s);
333   void     set_next_sibling(Klass* s);
334 
335  public:
336 
337   // Compiler support
338   static ByteSize super_offset()                 { return in_ByteSize(offset_of(Klass, _super)); }
339   static ByteSize super_check_offset_offset()    { return in_ByteSize(offset_of(Klass, _super_check_offset)); }
340   static ByteSize primary_supers_offset()        { return in_ByteSize(offset_of(Klass, _primary_supers)); }
341   static ByteSize secondary_super_cache_offset() { return in_ByteSize(offset_of(Klass, _secondary_super_cache)); }
342   static ByteSize secondary_supers_offset()      { return in_ByteSize(offset_of(Klass, _secondary_supers)); }
343   static ByteSize java_mirror_offset()           { return in_ByteSize(offset_of(Klass, _java_mirror)); }
344   static ByteSize modifier_flags_offset()        { return in_ByteSize(offset_of(Klass, _modifier_flags)); }
345   static ByteSize layout_helper_offset()         { return in_ByteSize(offset_of(Klass, _layout_helper)); }
346   static ByteSize access_flags_offset()          { return in_ByteSize(offset_of(Klass, _access_flags)); }
347 
348   // Unpacking layout_helper:
349   enum {
350     _lh_neutral_value           = 0,  // neutral non-array non-instance value
351     _lh_instance_slow_path_bit  = 0x01,
352     _lh_log2_element_size_shift = BitsPerByte*0,
353     _lh_log2_element_size_mask  = BitsPerLong-1,
354     _lh_element_type_shift      = BitsPerByte*1,
355     _lh_element_type_mask       = right_n_bits(BitsPerByte),  // shifted mask
356     _lh_header_size_shift       = BitsPerByte*2,
357     _lh_header_size_mask        = right_n_bits(BitsPerByte),  // shifted mask
358     _lh_array_tag_bits          = 2,
359     _lh_array_tag_shift         = BitsPerInt - _lh_array_tag_bits,
360     _lh_array_tag_obj_value     = ~0x01   // 0x80000000 >> 30
361   };
362 
363   static const unsigned int _lh_array_tag_type_value = 0Xffffffff; // ~0x00,  // 0xC0000000 >> 30
364 
365   static int layout_helper_size_in_bytes(jint lh) {
366     assert(lh > (jint)_lh_neutral_value, "must be instance");
367     return (int) lh & ~_lh_instance_slow_path_bit;
368   }
369   static bool layout_helper_needs_slow_path(jint lh) {
370     assert(lh > (jint)_lh_neutral_value, "must be instance");
371     return (lh & _lh_instance_slow_path_bit) != 0;
372   }
373   static bool layout_helper_is_instance(jint lh) {
374     return (jint)lh > (jint)_lh_neutral_value;
375   }
376   static bool layout_helper_is_array(jint lh) {
377     return (jint)lh < (jint)_lh_neutral_value;
378   }
379   static bool layout_helper_is_typeArray(jint lh) {
380     // _lh_array_tag_type_value == (lh >> _lh_array_tag_shift);
381     return (juint)lh >= (juint)(_lh_array_tag_type_value << _lh_array_tag_shift);
382   }
383   static bool layout_helper_is_objArray(jint lh) {
384     // _lh_array_tag_obj_value == (lh >> _lh_array_tag_shift);
385     return (jint)lh < (jint)(_lh_array_tag_type_value << _lh_array_tag_shift);
386   }
387   static int layout_helper_header_size(jint lh) {
388     assert(lh < (jint)_lh_neutral_value, "must be array");
389     int hsize = (lh >> _lh_header_size_shift) & _lh_header_size_mask;
390     assert(hsize > 0 && hsize < (int)sizeof(oopDesc)*3, "sanity");
391     return hsize;
392   }
393   static BasicType layout_helper_element_type(jint lh) {
394     assert(lh < (jint)_lh_neutral_value, "must be array");
395     int btvalue = (lh >> _lh_element_type_shift) & _lh_element_type_mask;
396     assert(btvalue >= T_BOOLEAN && btvalue <= T_OBJECT, "sanity");
397     return (BasicType) btvalue;
398   }
399 
400   // Want a pattern to quickly diff against layout header in register
401   // find something less clever!
402   static int layout_helper_boolean_diffbit() {
403     jint zlh = array_layout_helper(T_BOOLEAN);
404     jint blh = array_layout_helper(T_BYTE);
405     assert(zlh != blh, "array layout helpers must differ");
406     int diffbit = 1;
407     while ((diffbit & (zlh ^ blh)) == 0 && (diffbit & zlh) == 0) {
408       diffbit <<= 1;
409       assert(diffbit != 0, "make sure T_BOOLEAN has a different bit than T_BYTE");
410     }
411     return diffbit;
412   }
413 
414   static int layout_helper_log2_element_size(jint lh) {
415     assert(lh < (jint)_lh_neutral_value, "must be array");
416     int l2esz = (lh >> _lh_log2_element_size_shift) & _lh_log2_element_size_mask;
417     assert(l2esz <= LogBytesPerLong,
418            "sanity. l2esz: 0x%x for lh: 0x%x", (uint)l2esz, (uint)lh);
419     return l2esz;
420   }
421   static jint array_layout_helper(jint tag, int hsize, BasicType etype, int log2_esize) {
422     return (tag        << _lh_array_tag_shift)
423       |    (hsize      << _lh_header_size_shift)
424       |    ((int)etype << _lh_element_type_shift)
425       |    (log2_esize << _lh_log2_element_size_shift);
426   }
427   static jint instance_layout_helper(jint size, bool slow_path_flag) {
428     return (size << LogBytesPerWord)
429       |    (slow_path_flag ? _lh_instance_slow_path_bit : 0);
430   }
431   static int layout_helper_to_size_helper(jint lh) {
432     assert(lh > (jint)_lh_neutral_value, "must be instance");
433     // Note that the following expression discards _lh_instance_slow_path_bit.
434     return lh >> LogBytesPerWord;
435   }
436   // Out-of-line version computes everything based on the etype:
437   static jint array_layout_helper(BasicType etype);
438 
439   // What is the maximum number of primary superclasses any klass can have?
440 #ifdef PRODUCT
441   static juint primary_super_limit()         { return _primary_super_limit; }
442 #else
443   static juint primary_super_limit() {
444     assert(FastSuperclassLimit <= _primary_super_limit, "parameter oob");
445     return FastSuperclassLimit;
446   }
447 #endif
448 
449   // vtables
450   klassVtable vtable() const;
451   int vtable_length() const { return _vtable_len; }
452 
453   // subclass check
454   bool is_subclass_of(const Klass* k) const;
455   // subtype check: true if is_subclass_of, or if k is interface and receiver implements it
456   bool is_subtype_of(Klass* k) const {
457     juint    off = k->super_check_offset();
458     Klass* sup = *(Klass**)( (address)this + off );
459     const juint secondary_offset = in_bytes(secondary_super_cache_offset());
460     if (sup == k) {
461       return true;
462     } else if (off != secondary_offset) {
463       return false;
464     } else {
465       return search_secondary_supers(k);
466     }
467   }
468 
469   bool search_secondary_supers(Klass* k) const;
470 
471   // Find LCA in class hierarchy
472   Klass *LCA( Klass *k );
473 
474   // Check whether reflection/jni/jvm code is allowed to instantiate this class;
475   // if not, throw either an Error or an Exception.
476   virtual void check_valid_for_instantiation(bool throwError, TRAPS);
477 
478   // array copying
479   virtual void  copy_array(arrayOop s, int src_pos, arrayOop d, int dst_pos, int length, TRAPS);
480 
481   // tells if the class should be initialized
482   virtual bool should_be_initialized() const    { return false; }
483   // initializes the klass
484   virtual void initialize(TRAPS);
485   // lookup operation for MethodLookupCache
486   friend class MethodLookupCache;
487   virtual Klass* find_field(Symbol* name, Symbol* signature, fieldDescriptor* fd) const;
488   virtual Method* uncached_lookup_method(const Symbol* name, const Symbol* signature,
489                                          OverpassLookupMode overpass_mode,
490                                          PrivateLookupMode = find_private) const;
491  public:
492   Method* lookup_method(const Symbol* name, const Symbol* signature) const {
493     return uncached_lookup_method(name, signature, find_overpass);
494   }
495 
496   // array class with specific rank
497   Klass* array_klass(int rank, TRAPS)         {  return array_klass_impl(false, rank, THREAD); }
498 
499   // array class with this klass as element type
500   Klass* array_klass(TRAPS)                   {  return array_klass_impl(false, THREAD); }
501 
502   // These will return NULL instead of allocating on the heap:
503   // NB: these can block for a mutex, like other functions with TRAPS arg.
504   Klass* array_klass_or_null(int rank);
505   Klass* array_klass_or_null();
506 
507   virtual oop protection_domain() const = 0;
508 
509   oop class_loader() const;
510 
511   virtual oop klass_holder() const      { return class_loader(); }
512 
513  protected:
514   virtual Klass* array_klass_impl(bool or_null, int rank, TRAPS);
515   virtual Klass* array_klass_impl(bool or_null, TRAPS);
516 
517   void set_vtable_length(int len) { _vtable_len= len; }
518 
519   vtableEntry* start_of_vtable() const;
520  public:
521   Method* method_at_vtable(int index);
522 
523   static ByteSize vtable_start_offset();
524   static ByteSize vtable_length_offset() {
525     return byte_offset_of(Klass, _vtable_len);
526   }
527 
528   // CDS support - remove and restore oops from metadata. Oops are not shared.
529   virtual void remove_unshareable_info();
530   virtual void remove_java_mirror();
531   virtual void restore_unshareable_info(ClassLoaderData* loader_data, Handle protection_domain, TRAPS);
532 
533  protected:
534   // computes the subtype relationship
535   virtual bool compute_is_subtype_of(Klass* k);
536  public:
537   // subclass accessor (here for convenience; undefined for non-klass objects)
538   virtual bool is_leaf_class() const { fatal("not a class"); return false; }
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 #if INCLUDE_SERVICES
549   virtual void collect_statistics(KlassSizeStats *sz) const;
550 #endif
551 
552   // Returns the Java name for a class (Resource allocated)
553   // For arrays, this returns the name of the element with a leading '['.
554   // For classes, this returns the name with the package separators
555   //     turned into '.'s.
556   const char* external_name() const;
557   // Returns the name for a class (Resource allocated) as the class
558   // would appear in a signature.
559   // For arrays, this returns the name of the element with a leading '['.
560   // For classes, this returns the name with a leading 'L' and a trailing ';'
561   //     and the package separators as '/'.
562   virtual const char* signature_name() const;
563 
564   const char* joint_in_module_of_loader(const Klass* class2, bool include_parent_loader = false) const;
565   const char* class_in_module_of_loader(bool use_are = false, bool include_parent_loader = false) const;
566 
567   // Returns "interface", "abstract class" or "class".
568   const char* external_kind() const;
569 
570   // type testing operations
571 #ifdef ASSERT
572  protected:
573   virtual bool is_instance_klass_slow()     const { return false; }
574   virtual bool is_array_klass_slow()        const { return false; }
575   virtual bool is_objArray_klass_slow()     const { return false; }
576   virtual bool is_typeArray_klass_slow()    const { return false; }
577 #endif // ASSERT
578  public:
579 
580   // Fast non-virtual versions
581   #ifndef ASSERT
582   #define assert_same_query(xval, xcheck) xval
583   #else
584  private:
585   static bool assert_same_query(bool xval, bool xslow) {
586     assert(xval == xslow, "slow and fast queries agree");
587     return xval;
588   }
589  public:
590   #endif
591   inline  bool is_instance_klass()            const { return assert_same_query(
592                                                       layout_helper_is_instance(layout_helper()),
593                                                       is_instance_klass_slow()); }
594   inline  bool is_array_klass()               const { return assert_same_query(
595                                                     layout_helper_is_array(layout_helper()),
596                                                     is_array_klass_slow()); }
597   inline  bool is_objArray_klass()            const { return assert_same_query(
598                                                     layout_helper_is_objArray(layout_helper()),
599                                                     is_objArray_klass_slow()); }
600   inline  bool is_typeArray_klass()           const { return assert_same_query(
601                                                     layout_helper_is_typeArray(layout_helper()),
602                                                     is_typeArray_klass_slow()); }
603   #undef assert_same_query
604 
605   // Access flags
606   AccessFlags access_flags() const         { return _access_flags;  }
607   void set_access_flags(AccessFlags flags) { _access_flags = flags; }
608 
609   bool is_public() const                { return _access_flags.is_public(); }
610   bool is_final() const                 { return _access_flags.is_final(); }
611   bool is_interface() const             { return _access_flags.is_interface(); }
612   bool is_abstract() const              { return _access_flags.is_abstract(); }
613   bool is_super() const                 { return _access_flags.is_super(); }
614   bool is_synthetic() const             { return _access_flags.is_synthetic(); }
615   void set_is_synthetic()               { _access_flags.set_is_synthetic(); }
616   bool has_finalizer() const            { return _access_flags.has_finalizer(); }
617   bool has_final_method() const         { return _access_flags.has_final_method(); }
618   void set_has_finalizer()              { _access_flags.set_has_finalizer(); }
619   void set_has_final_method()           { _access_flags.set_has_final_method(); }
620   bool has_vanilla_constructor() const  { return _access_flags.has_vanilla_constructor(); }
621   void set_has_vanilla_constructor()    { _access_flags.set_has_vanilla_constructor(); }
622   bool has_miranda_methods () const     { return access_flags().has_miranda_methods(); }
623   void set_has_miranda_methods()        { _access_flags.set_has_miranda_methods(); }
624   bool is_shared() const                { return access_flags().is_shared_class(); } // shadows MetaspaceObj::is_shared)()
625   void set_is_shared()                  { _access_flags.set_is_shared_class(); }
626 
627   bool is_cloneable() const;
628   void set_is_cloneable();
629 
630   // Biased locking support
631   // Note: the prototype header is always set up to be at least the
632   // prototype markOop. If biased locking is enabled it may further be
633   // biasable and have an epoch.
634   markOop prototype_header() const      { return _prototype_header; }
635   // NOTE: once instances of this klass are floating around in the
636   // system, this header must only be updated at a safepoint.
637   // NOTE 2: currently we only ever set the prototype header to the
638   // biasable prototype for instanceKlasses. There is no technical
639   // reason why it could not be done for arrayKlasses aside from
640   // wanting to reduce the initial scope of this optimization. There
641   // are potential problems in setting the bias pattern for
642   // JVM-internal oops.
643   inline void set_prototype_header(markOop header);
644   static ByteSize prototype_header_offset() { return in_ByteSize(offset_of(Klass, _prototype_header)); }
645 
646   int  biased_lock_revocation_count() const { return (int) _biased_lock_revocation_count; }
647   // Atomically increments biased_lock_revocation_count and returns updated value
648   int atomic_incr_biased_lock_revocation_count();
649   void set_biased_lock_revocation_count(int val) { _biased_lock_revocation_count = (jint) val; }
650   jlong last_biased_lock_bulk_revocation_time() { return _last_biased_lock_bulk_revocation_time; }
651   void  set_last_biased_lock_bulk_revocation_time(jlong cur_time) { _last_biased_lock_bulk_revocation_time = cur_time; }
652 
653   JFR_ONLY(DEFINE_TRACE_ID_METHODS;)
654 
655   virtual void metaspace_pointers_do(MetaspaceClosure* iter);
656   virtual MetaspaceObj::Type type() const { return ClassType; }
657 
658   // Iff the class loader (or mirror for unsafe anonymous classes) is alive the
659   // Klass is considered alive.  Has already been marked as unloading.
660   bool is_loader_alive() const { return !class_loader_data()->is_unloading(); }
661 
662   // Load the klass's holder as a phantom. This is useful when a weak Klass
663   // pointer has been "peeked" and then must be kept alive before it may
664   // be used safely.
665   oop holder_phantom() const;
666 
667   static void clean_weak_klass_links(bool unloading_occurred, bool clean_alive_klasses = true);
668   static void clean_subklass_tree() {
669     clean_weak_klass_links(/*unloading_occurred*/ true , /* clean_alive_klasses */ false);
670   }
671 
672   // GC specific object visitors
673   //
674 #if INCLUDE_PARALLELGC
675   // Parallel Scavenge
676   virtual void oop_ps_push_contents(  oop obj, PSPromotionManager* pm)   = 0;
677   // Parallel Compact
678   virtual void oop_pc_follow_contents(oop obj, ParCompactionManager* cm) = 0;
679   virtual void oop_pc_update_pointers(oop obj, ParCompactionManager* cm) = 0;
680 #endif
681 
682   virtual void array_klasses_do(void f(Klass* k)) {}
683 
684   // Return self, except for abstract classes with exactly 1
685   // implementor.  Then return the 1 concrete implementation.
686   Klass *up_cast_abstract();
687 
688   // klass name
689   Symbol* name() const                   { return _name; }
690   void set_name(Symbol* n);
691 
692  public:
693   // jvm support
694   virtual jint compute_modifier_flags(TRAPS) const;
695 
696   // JVMTI support
697   virtual jint jvmti_class_status() const;
698 
699   // Printing
700   virtual void print_on(outputStream* st) const;
701 
702   virtual void oop_print_value_on(oop obj, outputStream* st);
703   virtual void oop_print_on      (oop obj, outputStream* st);
704 
705   virtual const char* internal_name() const = 0;
706 
707   // Verification
708   virtual void verify_on(outputStream* st);
709   void verify() { verify_on(tty); }
710 
711 #ifndef PRODUCT
712   bool verify_vtable_index(int index);
713 #endif
714 
715   virtual void oop_verify_on(oop obj, outputStream* st);
716 
717   static bool is_null(narrowKlass obj);
718   static bool is_null(Klass* obj);
719 
720   // klass encoding for klass pointer in objects.
721   static narrowKlass encode_klass_not_null(Klass* v);
722   static narrowKlass encode_klass(Klass* v);
723 
724   static Klass* decode_klass_not_null(narrowKlass v);
725   static Klass* decode_klass(narrowKlass v);
726 };
727 
728 #endif // SHARE_VM_OOPS_KLASS_HPP