1 /*
  2  * Copyright (c) 1997, 2022, 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 Kinds for all subclasses of Klass
 41 enum KlassKind {
 42   InstanceKlassKind,
 43   InstanceRefKlassKind,
 44   InstanceMirrorKlassKind,
 45   InstanceClassLoaderKlassKind,
 46   TypeArrayKlassKind,
 47   ObjArrayKlassKind
 48 };
 49 
 50 const uint KLASS_KIND_COUNT = ObjArrayKlassKind + 1;
 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 kind used to resolve the runtime type of the instance.
118   //  - Used to implement devirtualized oop closure dispatching.
119   //  - Various type checking in the JVM
120   const KlassKind _kind;
121 
122   // Processed access flags, for use by Class.getModifiers.
123   jint        _modifier_flags;
124 
125   // The fields _super_check_offset, _secondary_super_cache, _secondary_supers
126   // and _primary_supers all help make fast subtype checks.  See big discussion
127   // in doc/server_compiler/checktype.txt
128   //
129   // Where to look to observe a supertype (it is &_secondary_super_cache for
130   // secondary supers, else is &_primary_supers[depth()].
131   juint       _super_check_offset;
132 
133   // Class name.  Instance classes: java/lang/String, etc.  Array classes: [I,
134   // [Ljava/lang/String;, etc.  Set to zero for all other kinds of classes.
135   Symbol*     _name;
136 
137   // Cache of last observed secondary supertype
138   Klass*      _secondary_super_cache;
139   // Array of all secondary supertypes
140   Array<Klass*>* _secondary_supers;
141   // Ordered list of all primary supertypes
142   Klass*      _primary_supers[_primary_super_limit];
143   // java/lang/Class instance mirroring this class
144   OopHandle   _java_mirror;
145   // Superclass
146   Klass*      _super;
147   // First subclass (NULL if none); _subklass->next_sibling() is next one
148   Klass* volatile _subklass;
149   // Sibling link (or NULL); links all subklasses of a klass
150   Klass* volatile _next_sibling;
151 
152   // All klasses loaded by a class loader are chained through these links
153   Klass*      _next_link;
154 
155   // The VM's representation of the ClassLoader used to load this class.
156   // Provide access the corresponding instance java.lang.ClassLoader.
157   ClassLoaderData* _class_loader_data;
158 
159   int _vtable_len;              // vtable length. This field may be read very often when we
160                                 // have lots of itable dispatches (e.g., lambdas and streams).
161                                 // Keep it away from the beginning of a Klass to avoid cacheline
162                                 // contention that may happen when a nearby object is modified.
163   AccessFlags _access_flags;    // Access flags. The class/interface distinction is stored here.
164 
165   JFR_ONLY(DEFINE_TRACE_ID_FIELD;)
166 
167   markWord _prototype_header;   // Used to initialize objects' header
168 
169 private:
170   // This is an index into FileMapHeader::_shared_path_table[], to
171   // associate this class with the JAR file where it's loaded from during
172   // dump time. If a class is not loaded from the shared archive, this field is
173   // -1.
174   jshort _shared_class_path_index;
175 
176 #if INCLUDE_CDS
177   // Flags of the current shared class.
178   u2     _shared_class_flags;
179   enum {
180     _archived_lambda_proxy_is_available    = 1 << 1,
181     _has_value_based_class_annotation      = 1 << 2,
182     _verified_at_dump_time                 = 1 << 3,
183     _has_archived_enum_objs                = 1 << 4,
184     _regenerated                           = 1 << 5
185   };
186 #endif
187 
188   CDS_JAVA_HEAP_ONLY(int _archived_mirror_index;)
189 
190 protected:
191 
192   // Constructor
193   Klass(KlassKind kind);
194   Klass() : _kind(KlassKind(-1)) { assert(DumpSharedSpaces || UseSharedSpaces, "only for cds"); }
195 
196   void* operator new(size_t size, ClassLoaderData* loader_data, size_t word_size, TRAPS) throw();
197 
198  public:
199   int kind() { return _kind; }
200 
201   enum class DefaultsLookupMode { find, skip };
202   enum class OverpassLookupMode { find, skip };
203   enum class StaticLookupMode   { find, skip };
204   enum class PrivateLookupMode  { find, skip };
205 
206   virtual bool is_klass() const { return true; }
207 
208   // super() cannot be InstanceKlass* -- Java arrays are covariant, and _super is used
209   // to implement that. NB: the _super of "[Ljava/lang/Integer;" is "[Ljava/lang/Number;"
210   // If this is not what your code expects, you're probably looking for Klass::java_super().
211   Klass* super() const               { return _super; }
212   void set_super(Klass* k)           { _super = k; }
213 
214   // initializes _super link, _primary_supers & _secondary_supers arrays
215   void initialize_supers(Klass* k, Array<InstanceKlass*>* transitive_interfaces, TRAPS);
216 
217   // klass-specific helper for initializing _secondary_supers
218   virtual GrowableArray<Klass*>* compute_secondary_supers(int num_extra_slots,
219                                                           Array<InstanceKlass*>* transitive_interfaces);
220 
221   // java_super is the Java-level super type as specified by Class.getSuperClass.
222   virtual InstanceKlass* java_super() const  { return NULL; }
223 
224   juint    super_check_offset() const  { return _super_check_offset; }
225   void set_super_check_offset(juint o) { _super_check_offset = o; }
226 
227   Klass* secondary_super_cache() const     { return _secondary_super_cache; }
228   void set_secondary_super_cache(Klass* k) { _secondary_super_cache = k; }
229 
230   Array<Klass*>* secondary_supers() const { return _secondary_supers; }
231   void set_secondary_supers(Array<Klass*>* k) { _secondary_supers = k; }
232 
233   // Return the element of the _super chain of the given depth.
234   // If there is no such element, return either NULL or this.
235   Klass* primary_super_of_depth(juint i) const {
236     assert(i < primary_super_limit(), "oob");
237     Klass* super = _primary_supers[i];
238     assert(super == NULL || super->super_depth() == i, "correct display");
239     return super;
240   }
241 
242   // Can this klass be a primary super?  False for interfaces and arrays of
243   // interfaces.  False also for arrays or classes with long super chains.
244   bool can_be_primary_super() const {
245     const juint secondary_offset = in_bytes(secondary_super_cache_offset());
246     return super_check_offset() != secondary_offset;
247   }
248   virtual bool can_be_primary_super_slow() const;
249 
250   // Returns number of primary supers; may be a number in the inclusive range [0, primary_super_limit].
251   juint super_depth() const {
252     if (!can_be_primary_super()) {
253       return primary_super_limit();
254     } else {
255       juint d = (super_check_offset() - in_bytes(primary_supers_offset())) / sizeof(Klass*);
256       assert(d < primary_super_limit(), "oob");
257       assert(_primary_supers[d] == this, "proper init");
258       return d;
259     }
260   }
261 
262   // java mirror
263   oop java_mirror() const;
264   oop java_mirror_no_keepalive() const;
265   void set_java_mirror(Handle m);
266 
267   oop archived_java_mirror() NOT_CDS_JAVA_HEAP_RETURN_(NULL);
268   void set_archived_java_mirror(oop m) NOT_CDS_JAVA_HEAP_RETURN;
269 
270   // Temporary mirror switch used by RedefineClasses
271   void replace_java_mirror(oop mirror);
272 
273   // Set java mirror OopHandle to NULL for CDS
274   // This leaves the OopHandle in the CLD, but that's ok, you can't release them.
275   void clear_java_mirror_handle() { _java_mirror = OopHandle(); }
276 
277   // modifier flags
278   jint modifier_flags() const          { return _modifier_flags; }
279   void set_modifier_flags(jint flags)  { _modifier_flags = flags; }
280 
281   // size helper
282   int layout_helper() const            { return _layout_helper; }
283   void set_layout_helper(int lh)       { _layout_helper = lh; }
284 
285   // Note: for instances layout_helper() may include padding.
286   // Use InstanceKlass::contains_field_offset to classify field offsets.
287 
288   // sub/superklass links
289   Klass* subklass(bool log = false) const;
290   Klass* next_sibling(bool log = false) const;
291 
292   InstanceKlass* superklass() const;
293   void append_to_sibling_list();           // add newly created receiver to superklass' subklass list
294 
295   void set_next_link(Klass* k) { _next_link = k; }
296   Klass* next_link() const { return _next_link; }   // The next klass defined by the class loader.
297   Klass** next_link_addr() { return &_next_link; }
298 
299   // class loader data
300   ClassLoaderData* class_loader_data() const               { return _class_loader_data; }
301   void set_class_loader_data(ClassLoaderData* loader_data) {  _class_loader_data = loader_data; }
302 
303   int shared_classpath_index() const   {
304     return _shared_class_path_index;
305   };
306 
307   void set_shared_classpath_index(int index) {
308     _shared_class_path_index = index;
309   };
310 
311   bool has_archived_mirror_index() const {
312     CDS_JAVA_HEAP_ONLY(return _archived_mirror_index >= 0;)
313     NOT_CDS_JAVA_HEAP(return false);
314   }
315 
316   void clear_archived_mirror_index() NOT_CDS_JAVA_HEAP_RETURN;
317 
318   void set_lambda_proxy_is_available() {
319     CDS_ONLY(_shared_class_flags |= _archived_lambda_proxy_is_available;)
320   }
321   void clear_lambda_proxy_is_available() {
322     CDS_ONLY(_shared_class_flags &= ~_archived_lambda_proxy_is_available;)
323   }
324   bool lambda_proxy_is_available() const {
325     CDS_ONLY(return (_shared_class_flags & _archived_lambda_proxy_is_available) != 0;)
326     NOT_CDS(return false;)
327   }
328 
329   void set_has_value_based_class_annotation() {
330     CDS_ONLY(_shared_class_flags |= _has_value_based_class_annotation;)
331   }
332   void clear_has_value_based_class_annotation() {
333     CDS_ONLY(_shared_class_flags &= ~_has_value_based_class_annotation;)
334   }
335   bool has_value_based_class_annotation() const {
336     CDS_ONLY(return (_shared_class_flags & _has_value_based_class_annotation) != 0;)
337     NOT_CDS(return false;)
338   }
339 
340   void set_verified_at_dump_time() {
341     CDS_ONLY(_shared_class_flags |= _verified_at_dump_time;)
342   }
343   bool verified_at_dump_time() const {
344     CDS_ONLY(return (_shared_class_flags & _verified_at_dump_time) != 0;)
345     NOT_CDS(return false;)
346   }
347 
348   void set_has_archived_enum_objs() {
349     CDS_ONLY(_shared_class_flags |= _has_archived_enum_objs;)
350   }
351   bool has_archived_enum_objs() const {
352     CDS_ONLY(return (_shared_class_flags & _has_archived_enum_objs) != 0;)
353     NOT_CDS(return false;)
354   }
355 
356   void set_regenerated() {
357     CDS_ONLY(_shared_class_flags |= _regenerated;)
358   }
359   bool is_regenerated() const {
360     CDS_ONLY(return (_shared_class_flags & _regenerated) != 0;)
361     NOT_CDS(return false;)
362   }
363 
364   // Obtain the module or package for this class
365   virtual ModuleEntry* module() const = 0;
366   virtual PackageEntry* package() const = 0;
367 
368  protected:                                // internal accessors
369   void     set_subklass(Klass* s);
370   void     set_next_sibling(Klass* s);
371 
372  public:
373 
374   // Compiler support
375   static ByteSize super_offset()                 { return in_ByteSize(offset_of(Klass, _super)); }
376   static ByteSize super_check_offset_offset()    { return in_ByteSize(offset_of(Klass, _super_check_offset)); }
377   static ByteSize primary_supers_offset()        { return in_ByteSize(offset_of(Klass, _primary_supers)); }
378   static ByteSize secondary_super_cache_offset() { return in_ByteSize(offset_of(Klass, _secondary_super_cache)); }
379   static ByteSize secondary_supers_offset()      { return in_ByteSize(offset_of(Klass, _secondary_supers)); }
380   static ByteSize java_mirror_offset()           { return in_ByteSize(offset_of(Klass, _java_mirror)); }
381   static ByteSize class_loader_data_offset()     { return in_ByteSize(offset_of(Klass, _class_loader_data)); }
382   static ByteSize modifier_flags_offset()        { return in_ByteSize(offset_of(Klass, _modifier_flags)); }
383   static ByteSize layout_helper_offset()         { return in_ByteSize(offset_of(Klass, _layout_helper)); }
384   static ByteSize access_flags_offset()          { return in_ByteSize(offset_of(Klass, _access_flags)); }
385 
386   // Unpacking layout_helper:
387   static const int _lh_neutral_value           = 0;  // neutral non-array non-instance value
388   static const int _lh_instance_slow_path_bit  = 0x01;
389   static const int _lh_log2_element_size_shift = BitsPerByte*0;
390   static const int _lh_log2_element_size_mask  = BitsPerLong-1;
391   static const int _lh_element_type_shift      = BitsPerByte*1;
392   static const int _lh_element_type_mask       = right_n_bits(BitsPerByte);  // shifted mask
393   static const int _lh_header_size_shift       = BitsPerByte*2;
394   static const int _lh_header_size_mask        = right_n_bits(BitsPerByte);  // shifted mask
395   static const int _lh_array_tag_bits          = 2;
396   static const int _lh_array_tag_shift         = BitsPerInt - _lh_array_tag_bits;
397   static const int _lh_array_tag_obj_value     = ~0x01;   // 0x80000000 >> 30
398 
399   static const unsigned int _lh_array_tag_type_value = 0Xffffffff; // ~0x00,  // 0xC0000000 >> 30
400 
401   static int layout_helper_size_in_bytes(jint lh) {
402     assert(lh > (jint)_lh_neutral_value, "must be instance");
403     return (int) lh & ~_lh_instance_slow_path_bit;
404   }
405   static bool layout_helper_needs_slow_path(jint lh) {
406     assert(lh > (jint)_lh_neutral_value, "must be instance");
407     return (lh & _lh_instance_slow_path_bit) != 0;
408   }
409   static bool layout_helper_is_instance(jint lh) {
410     return (jint)lh > (jint)_lh_neutral_value;
411   }
412   static bool layout_helper_is_array(jint lh) {
413     return (jint)lh < (jint)_lh_neutral_value;
414   }
415   static bool layout_helper_is_typeArray(jint lh) {
416     // _lh_array_tag_type_value == (lh >> _lh_array_tag_shift);
417     return (juint)lh >= (juint)(_lh_array_tag_type_value << _lh_array_tag_shift);
418   }
419   static bool layout_helper_is_objArray(jint lh) {
420     // _lh_array_tag_obj_value == (lh >> _lh_array_tag_shift);
421     return (jint)lh < (jint)(_lh_array_tag_type_value << _lh_array_tag_shift);
422   }
423   static int layout_helper_header_size(jint lh) {
424     assert(lh < (jint)_lh_neutral_value, "must be array");
425     int hsize = (lh >> _lh_header_size_shift) & _lh_header_size_mask;
426     assert(hsize > 0 && hsize < (int)sizeof(oopDesc)*3, "sanity");
427     return hsize;
428   }
429   static BasicType layout_helper_element_type(jint lh) {
430     assert(lh < (jint)_lh_neutral_value, "must be array");
431     int btvalue = (lh >> _lh_element_type_shift) & _lh_element_type_mask;
432     assert(btvalue >= T_BOOLEAN && btvalue <= T_OBJECT, "sanity");
433     return (BasicType) btvalue;
434   }
435 
436   // Want a pattern to quickly diff against layout header in register
437   // find something less clever!
438   static int layout_helper_boolean_diffbit() {
439     jint zlh = array_layout_helper(T_BOOLEAN);
440     jint blh = array_layout_helper(T_BYTE);
441     assert(zlh != blh, "array layout helpers must differ");
442     int diffbit = 1;
443     while ((diffbit & (zlh ^ blh)) == 0 && (diffbit & zlh) == 0) {
444       diffbit <<= 1;
445       assert(diffbit != 0, "make sure T_BOOLEAN has a different bit than T_BYTE");
446     }
447     return diffbit;
448   }
449 
450   static int layout_helper_log2_element_size(jint lh) {
451     assert(lh < (jint)_lh_neutral_value, "must be array");
452     int l2esz = (lh >> _lh_log2_element_size_shift) & _lh_log2_element_size_mask;
453     assert(l2esz <= LogBytesPerLong,
454            "sanity. l2esz: 0x%x for lh: 0x%x", (uint)l2esz, (uint)lh);
455     return l2esz;
456   }
457   static jint array_layout_helper(jint tag, int hsize, BasicType etype, int log2_esize) {
458     return (tag        << _lh_array_tag_shift)
459       |    (hsize      << _lh_header_size_shift)
460       |    ((int)etype << _lh_element_type_shift)
461       |    (log2_esize << _lh_log2_element_size_shift);
462   }
463   static jint instance_layout_helper(jint size, bool slow_path_flag) {
464     return (size << LogBytesPerWord)
465       |    (slow_path_flag ? _lh_instance_slow_path_bit : 0);
466   }
467   static int layout_helper_to_size_helper(jint lh) {
468     assert(lh > (jint)_lh_neutral_value, "must be instance");
469     // Note that the following expression discards _lh_instance_slow_path_bit.
470     return lh >> LogBytesPerWord;
471   }
472   // Out-of-line version computes everything based on the etype:
473   static jint array_layout_helper(BasicType etype);
474 
475   // What is the maximum number of primary superclasses any klass can have?
476   static juint primary_super_limit()         { return _primary_super_limit; }
477 
478   // vtables
479   klassVtable vtable() const;
480   int vtable_length() const { return _vtable_len; }
481 
482   // subclass check
483   bool is_subclass_of(const Klass* k) const;
484   // subtype check: true if is_subclass_of, or if k is interface and receiver implements it
485   bool is_subtype_of(Klass* k) const {
486     juint    off = k->super_check_offset();
487     Klass* sup = *(Klass**)( (address)this + off );
488     const juint secondary_offset = in_bytes(secondary_super_cache_offset());
489     if (sup == k) {
490       return true;
491     } else if (off != secondary_offset) {
492       return false;
493     } else {
494       return search_secondary_supers(k);
495     }
496   }
497 
498   bool search_secondary_supers(Klass* k) const;
499 
500   // Find LCA in class hierarchy
501   Klass *LCA( Klass *k );
502 
503   // Check whether reflection/jni/jvm code is allowed to instantiate this class;
504   // if not, throw either an Error or an Exception.
505   virtual void check_valid_for_instantiation(bool throwError, TRAPS);
506 
507   // array copying
508   virtual void  copy_array(arrayOop s, int src_pos, arrayOop d, int dst_pos, int length, TRAPS);
509 
510   // tells if the class should be initialized
511   virtual bool should_be_initialized() const    { return false; }
512   // initializes the klass
513   virtual void initialize(TRAPS);
514   virtual Klass* find_field(Symbol* name, Symbol* signature, fieldDescriptor* fd) const;
515   virtual Method* uncached_lookup_method(const Symbol* name, const Symbol* signature,
516                                          OverpassLookupMode overpass_mode,
517                                          PrivateLookupMode = PrivateLookupMode::find) const;
518  public:
519   Method* lookup_method(const Symbol* name, const Symbol* signature) const {
520     return uncached_lookup_method(name, signature, OverpassLookupMode::find);
521   }
522 
523   // array class with specific rank
524   virtual Klass* array_klass(int rank, TRAPS) = 0;
525 
526   // array class with this klass as element type
527   virtual Klass* array_klass(TRAPS) = 0;
528 
529   // These will return NULL instead of allocating on the heap:
530   virtual Klass* array_klass_or_null(int rank) = 0;
531   virtual Klass* array_klass_or_null() = 0;
532 
533   virtual oop protection_domain() const = 0;
534 
535   oop class_loader() const;
536 
537   inline oop klass_holder() const;
538 
539  protected:
540 
541   // Error handling when length > max_length or length < 0
542   static void check_array_allocation_length(int length, int max_length, TRAPS);
543 
544   void set_vtable_length(int len) { _vtable_len= len; }
545 
546   vtableEntry* start_of_vtable() const;
547   void restore_unshareable_info(ClassLoaderData* loader_data, Handle protection_domain, TRAPS);
548  public:
549   Method* method_at_vtable(int index);
550 
551   static ByteSize vtable_start_offset();
552   static ByteSize vtable_length_offset() {
553     return byte_offset_of(Klass, _vtable_len);
554   }
555 
556   // CDS support - remove and restore oops from metadata. Oops are not shared.
557   virtual void remove_unshareable_info();
558   virtual void remove_java_mirror();
559 
560   bool is_unshareable_info_restored() const {
561     assert(is_shared(), "use this for shared classes only");
562     if (has_archived_mirror_index()) {
563       // _java_mirror is not a valid OopHandle but rather an encoded reference in the shared heap
564       return false;
565     } else if (_java_mirror.ptr_raw() == NULL) {
566       return false;
567     } else {
568       return true;
569     }
570   }
571 
572  public:
573   // ALL FUNCTIONS BELOW THIS POINT ARE DISPATCHED FROM AN OOP
574   // These functions describe behavior for the oop not the KLASS.
575 
576   // actual oop size of obj in memory in word size.
577   virtual size_t oop_size(oop obj) const = 0;
578 
579   // Size of klass in word size.
580   virtual int size() const = 0;
581 
582   // Returns the Java name for a class (Resource allocated)
583   // For arrays, this returns the name of the element with a leading '['.
584   // For classes, this returns the name with the package separators
585   //     turned into '.'s.
586   const char* external_name() const;
587   // Returns the name for a class (Resource allocated) as the class
588   // would appear in a signature.
589   // For arrays, this returns the name of the element with a leading '['.
590   // For classes, this returns the name with a leading 'L' and a trailing ';'
591   //     and the package separators as '/'.
592   virtual const char* signature_name() const;
593 
594   const char* joint_in_module_of_loader(const Klass* class2, bool include_parent_loader = false) const;
595   const char* class_in_module_of_loader(bool use_are = false, bool include_parent_loader = false) const;
596 
597   // Returns "interface", "abstract class" or "class".
598   const char* external_kind() const;
599 
600   // type testing operations
601 #ifdef ASSERT
602  protected:
603   virtual bool is_instance_klass_slow()     const { return false; }
604   virtual bool is_array_klass_slow()        const { return false; }
605   virtual bool is_objArray_klass_slow()     const { return false; }
606   virtual bool is_typeArray_klass_slow()    const { return false; }
607 #endif // ASSERT
608  public:
609 
610   // Fast non-virtual versions
611   #ifndef ASSERT
612   #define assert_same_query(xval, xcheck) xval
613   #else
614  private:
615   static bool assert_same_query(bool xval, bool xslow) {
616     assert(xval == xslow, "slow and fast queries agree");
617     return xval;
618   }
619  public:
620   #endif
621 
622   bool is_instance_klass()              const { return assert_same_query(_kind <= InstanceClassLoaderKlassKind, is_instance_klass_slow()); }
623   // Other is anything that is not one of the more specialized kinds of InstanceKlass.
624   bool is_other_instance_klass()        const { return _kind == InstanceKlassKind; }
625   bool is_reference_instance_klass()    const { return _kind == InstanceRefKlassKind; }
626   bool is_mirror_instance_klass()       const { return _kind == InstanceMirrorKlassKind; }
627   bool is_class_loader_instance_klass() const { return _kind == InstanceClassLoaderKlassKind; }
628   bool is_array_klass()                 const { return assert_same_query( _kind >= TypeArrayKlassKind, is_array_klass_slow()); }
629   bool is_objArray_klass()              const { return assert_same_query( _kind == ObjArrayKlassKind,  is_objArray_klass_slow()); }
630   bool is_typeArray_klass()             const { return assert_same_query( _kind == TypeArrayKlassKind, is_typeArray_klass_slow()); }
631   #undef assert_same_query
632 
633   // Access flags
634   AccessFlags access_flags() const         { return _access_flags;  }
635   void set_access_flags(AccessFlags flags) { _access_flags = flags; }
636 
637   bool is_public() const                { return _access_flags.is_public(); }
638   bool is_final() const                 { return _access_flags.is_final(); }
639   bool is_interface() const             { return _access_flags.is_interface(); }
640   bool is_abstract() const              { return _access_flags.is_abstract(); }
641   bool is_super() const                 { return _access_flags.is_super(); }
642   bool is_synthetic() const             { return _access_flags.is_synthetic(); }
643   void set_is_synthetic()               { _access_flags.set_is_synthetic(); }
644   bool has_finalizer() const            { return _access_flags.has_finalizer(); }
645   bool has_final_method() const         { return _access_flags.has_final_method(); }
646   void set_has_finalizer()              { _access_flags.set_has_finalizer(); }
647   void set_has_final_method()           { _access_flags.set_has_final_method(); }
648   bool has_vanilla_constructor() const  { return _access_flags.has_vanilla_constructor(); }
649   void set_has_vanilla_constructor()    { _access_flags.set_has_vanilla_constructor(); }
650   bool has_miranda_methods () const     { return access_flags().has_miranda_methods(); }
651   void set_has_miranda_methods()        { _access_flags.set_has_miranda_methods(); }
652   bool is_shared() const                { return access_flags().is_shared_class(); } // shadows MetaspaceObj::is_shared)()
653   void set_is_shared()                  { _access_flags.set_is_shared_class(); }
654   bool is_hidden() const                { return access_flags().is_hidden_class(); }
655   void set_is_hidden()                  { _access_flags.set_is_hidden_class(); }
656   bool is_value_based()                 { return _access_flags.is_value_based_class(); }
657   void set_is_value_based()             { _access_flags.set_is_value_based_class(); }
658 
659   inline bool is_non_strong_hidden() const;
660 
661   bool is_cloneable() const;
662   void set_is_cloneable();
663 
664   markWord prototype_header() const      { return _prototype_header; }
665   inline void set_prototype_header(markWord header);
666   static ByteSize prototype_header_offset() { return in_ByteSize(offset_of(Klass, _prototype_header)); }
667 
668   JFR_ONLY(DEFINE_TRACE_ID_METHODS;)
669 
670   virtual void metaspace_pointers_do(MetaspaceClosure* iter);
671   virtual MetaspaceObj::Type type() const { return ClassType; }
672 
673   inline bool is_loader_alive() const;
674 
675   void clean_subklass();
676 
677   static void clean_weak_klass_links(bool unloading_occurred, bool clean_alive_klasses = true);
678   static void clean_subklass_tree() {
679     clean_weak_klass_links(/*unloading_occurred*/ true , /* clean_alive_klasses */ false);
680   }
681 
682   // Return self, except for abstract classes with exactly 1
683   // implementor.  Then return the 1 concrete implementation.
684   Klass *up_cast_abstract();
685 
686   // klass name
687   Symbol* name() const                   { return _name; }
688   void set_name(Symbol* n);
689 
690   virtual void release_C_heap_structures(bool release_constant_pool = true);
691 
692  public:
693   virtual jint compute_modifier_flags() const = 0;
694 
695   // JVMTI support
696   virtual jint jvmti_class_status() const;
697 
698   // Printing
699   virtual void print_on(outputStream* st) const;
700 
701   virtual void oop_print_value_on(oop obj, outputStream* st);
702   virtual void oop_print_on      (oop obj, outputStream* st);
703 
704   virtual const char* internal_name() const = 0;
705 
706   // Verification
707   virtual void verify_on(outputStream* st);
708   void verify() { verify_on(tty); }
709 
710 #ifndef PRODUCT
711   bool verify_vtable_index(int index);
712 #endif
713 
714   virtual void oop_verify_on(oop obj, outputStream* st);
715 
716   // for error reporting
717   static bool is_valid(Klass* k);
718 };
719 
720 #endif // SHARE_OOPS_KLASS_HPP