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.
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 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   FlatArrayKlassID,
 48   ObjArrayKlassID
 49 };
 50 
 51 const uint KLASS_ID_COUNT = 7;
 52 
 53 //
 54 // A Klass provides:
 55 //  1: language level class object (method dictionary etc.)
 56 //  2: provide vm dispatch behavior for the object
 57 // Both functions are combined into one C++ class.
 58 
 59 // One reason for the oop/klass dichotomy in the implementation is
 60 // that we don't want a C++ vtbl pointer in every object.  Thus,
 61 // normal oops don't have any virtual functions.  Instead, they
 62 // forward all "virtual" functions to their klass, which does have
 63 // a vtbl and does the C++ dispatch depending on the object's
 64 // actual type.  (See oop.inline.hpp for some of the forwarding code.)
 65 // ALL FUNCTIONS IMPLEMENTING THIS DISPATCH ARE PREFIXED WITH "oop_"!
 66 
 67 // Forward declarations.
 68 template <class T> class Array;
 69 template <class T> class GrowableArray;
 70 class ClassLoaderData;
 71 class fieldDescriptor;
 72 class klassVtable;
 73 class ModuleEntry;
 74 class PackageEntry;
 75 class ParCompactionManager;
 76 class PSPromotionManager;
 77 class vtableEntry;
 78 
 79 class Klass : public Metadata {
 80   friend class VMStructs;
 81   friend class JVMCIVMStructs;
 82  protected:
 83   // If you add a new field that points to any metaspace object, you
 84   // must add this field to Klass::metaspace_pointers_do().
 85 
 86   // note: put frequently-used fields together at start of klass structure
 87   // for better cache behavior (may not make much of a difference but sure won't hurt)
 88   enum { _primary_super_limit = 8 };
 89 
 90   // The "layout helper" is a combined descriptor of object layout.
 91   // For klasses which are neither instance nor array, the value is zero.
 92   //
 93   // For instances, layout helper is a positive number, the instance size.
 94   // This size is already passed through align_object_size and scaled to bytes.
 95   // The low order bit is set if instances of this class cannot be
 96   // allocated using the fastpath.
 97   //
 98   // For arrays, layout helper is a negative number, containing four
 99   // distinct bytes, as follows:
100   //    MSB:[tag, hsz, ebt, log2(esz)]:LSB
101   // where:
102   //    tag is 0x80 if the elements are oops, 0xC0 if non-oops, 0xA0 if value types
103   //    hsz is array header size in bytes (i.e., offset of first element)
104   //    ebt is the BasicType of the elements
105   //    esz is the element size in bytes
106   // This packed word is arranged so as to be quickly unpacked by the
107   // various fast paths that use the various subfields.
108   //
109   // The esz bits can be used directly by a SLL instruction, without masking.
110   //
111   // Note that the array-kind tag looks like 0x00 for instance klasses,
112   // since their length in bytes is always less than 24Mb.
113   //
114   // Final note:  This comes first, immediately after C++ vtable,
115   // because it is frequently queried.
116   jint        _layout_helper;
117 
118   // Klass identifier used to implement devirtualized oop closure dispatching.
119   const KlassID _id;
120 
121   // Processed access flags, for use by Class.getModifiers.
122   jint        _modifier_flags;
123 
124   // The fields _super_check_offset, _secondary_super_cache, _secondary_supers
125   // and _primary_supers all help make fast subtype checks.  See big discussion
126   // in doc/server_compiler/checktype.txt
127   //
128   // Where to look to observe a supertype (it is &_secondary_super_cache for
129   // secondary supers, else is &_primary_supers[depth()].
130   juint       _super_check_offset;
131 
132   // Class name.  Instance classes: java/lang/String, etc.  Array classes: [I,
133   // [Ljava/lang/String;, etc.  Set to zero for all other kinds of classes.
134   Symbol*     _name;
135 
136   // Cache of last observed secondary supertype
137   Klass*      _secondary_super_cache;
138   // Array of all secondary supertypes
139   Array<Klass*>* _secondary_supers;
140   // Ordered list of all primary supertypes
141   Klass*      _primary_supers[_primary_super_limit];
142   // java/lang/Class instance mirroring this class
143   OopHandle   _java_mirror;
144   // Superclass
145   Klass*      _super;
146   // First subclass (NULL if none); _subklass->next_sibling() is next one
147   Klass* volatile _subklass;
148   // Sibling link (or NULL); links all subklasses of a klass
149   Klass* volatile _next_sibling;
150 
151   // All klasses loaded by a class loader are chained through these links
152   Klass*      _next_link;
153 
154   // The VM's representation of the ClassLoader used to load this class.
155   // Provide access the corresponding instance java.lang.ClassLoader.
156   ClassLoaderData* _class_loader_data;
157 
158   int _vtable_len;              // vtable length. This field may be read very often when we
159                                 // have lots of itable dispatches (e.g., lambdas and streams).
160                                 // Keep it away from the beginning of a Klass to avoid cacheline
161                                 // contention that may happen when a nearby object is modified.
162   AccessFlags _access_flags;    // Access flags. The class/interface distinction is stored here.
163 
164   JFR_ONLY(DEFINE_TRACE_ID_FIELD;)
165 
166   markWord _prototype_header;  // inline type and inline array mark patterns
167 private:
168   // This is an index into FileMapHeader::_shared_path_table[], to
169   // associate this class with the JAR file where it's loaded from during
170   // dump time. If a class is not loaded from the shared archive, this field is
171   // -1.
172   jshort _shared_class_path_index;
173 
174 #if INCLUDE_CDS
175   // Flags of the current shared class.
176   u2     _shared_class_flags;
177   enum {
178     _archived_lambda_proxy_is_available    = 1 << 1,
179     _has_value_based_class_annotation      = 1 << 2,
180     _verified_at_dump_time                 = 1 << 3,
181     _has_archived_enum_objs                = 1 << 4,
182     _regenerated                           = 1 << 5
183   };
184 #endif
185 
186   CDS_JAVA_HEAP_ONLY(int _archived_mirror_index;)
187 
188 protected:
189 
190   // Constructor
191   Klass(KlassID id);
192   Klass() : _id(KlassID(-1)) { assert(DumpSharedSpaces || UseSharedSpaces, "only for cds"); }
193 
194   void* operator new(size_t size, ClassLoaderData* loader_data, size_t word_size, TRAPS) throw();
195 
196  public:
197   int id() { return _id; }
198 
199   enum class DefaultsLookupMode { find, skip };
200   enum class OverpassLookupMode { find, skip };
201   enum class StaticLookupMode   { find, skip };
202   enum class PrivateLookupMode  { find, skip };
203 
204   virtual bool is_klass() const { return true; }
205 
206   // super() cannot be InstanceKlass* -- Java arrays are covariant, and _super is used
207   // to implement that. NB: the _super of "[Ljava/lang/Integer;" is "[Ljava/lang/Number;"
208   // If this is not what your code expects, you're probably looking for Klass::java_super().
209   Klass* super() const               { return _super; }
210   void set_super(Klass* k)           { _super = k; }
211 
212   // initializes _super link, _primary_supers & _secondary_supers arrays
213   void initialize_supers(Klass* k, Array<InstanceKlass*>* transitive_interfaces, TRAPS);
214 
215   // klass-specific helper for initializing _secondary_supers
216   virtual GrowableArray<Klass*>* compute_secondary_supers(int num_extra_slots,
217                                                           Array<InstanceKlass*>* transitive_interfaces);
218 
219   // java_super is the Java-level super type as specified by Class.getSuperClass.
220   virtual InstanceKlass* java_super() const  { return NULL; }
221 
222   juint    super_check_offset() const  { return _super_check_offset; }
223   void set_super_check_offset(juint o) { _super_check_offset = o; }
224 
225   Klass* secondary_super_cache() const     { return _secondary_super_cache; }
226   void set_secondary_super_cache(Klass* k) { _secondary_super_cache = k; }
227 
228   Array<Klass*>* secondary_supers() const { return _secondary_supers; }
229   void set_secondary_supers(Array<Klass*>* k) { _secondary_supers = k; }
230 
231   // Return the element of the _super chain of the given depth.
232   // If there is no such element, return either NULL or this.
233   Klass* primary_super_of_depth(juint i) const {
234     assert(i < primary_super_limit(), "oob");
235     Klass* super = _primary_supers[i];
236     assert(super == NULL || super->super_depth() == i, "correct display");
237     return super;
238   }
239 
240   // Can this klass be a primary super?  False for interfaces and arrays of
241   // interfaces.  False also for arrays or classes with long super chains.
242   bool can_be_primary_super() const {
243     const juint secondary_offset = in_bytes(secondary_super_cache_offset());
244     return super_check_offset() != secondary_offset;
245   }
246   virtual bool can_be_primary_super_slow() const;
247 
248   // Returns number of primary supers; may be a number in the inclusive range [0, primary_super_limit].
249   juint super_depth() const {
250     if (!can_be_primary_super()) {
251       return primary_super_limit();
252     } else {
253       juint d = (super_check_offset() - in_bytes(primary_supers_offset())) / sizeof(Klass*);
254       assert(d < primary_super_limit(), "oob");
255       assert(_primary_supers[d] == this, "proper init");
256       return d;
257     }
258   }
259 
260   // java mirror
261   oop java_mirror() const;
262   oop java_mirror_no_keepalive() const;
263   void set_java_mirror(Handle m);
264 
265   oop archived_java_mirror() NOT_CDS_JAVA_HEAP_RETURN_(NULL);
266   void set_archived_java_mirror(oop m) NOT_CDS_JAVA_HEAP_RETURN;
267 
268   // Temporary mirror switch used by RedefineClasses
269   void replace_java_mirror(oop mirror);
270 
271   // Set java mirror OopHandle to NULL for CDS
272   // This leaves the OopHandle in the CLD, but that's ok, you can't release them.
273   void clear_java_mirror_handle() { _java_mirror = OopHandle(); }
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(bool log = false) const;
288   Klass* next_sibling(bool log = false) const;
289 
290   InstanceKlass* superklass() const;
291   void append_to_sibling_list();           // add newly created receiver to superklass' subklass list
292 
293   void set_next_link(Klass* k) { _next_link = k; }
294   Klass* next_link() const { return _next_link; }   // The next klass defined by the class loader.
295   Klass** next_link_addr() { return &_next_link; }
296 
297   // class loader data
298   ClassLoaderData* class_loader_data() const               { return _class_loader_data; }
299   void set_class_loader_data(ClassLoaderData* loader_data) {  _class_loader_data = loader_data; }
300 
301   int shared_classpath_index() const   {
302     return _shared_class_path_index;
303   };
304 
305   void set_shared_classpath_index(int index) {
306     _shared_class_path_index = index;
307   };
308 
309   bool has_archived_mirror_index() const {
310     CDS_JAVA_HEAP_ONLY(return _archived_mirror_index >= 0;)
311     NOT_CDS_JAVA_HEAP(return false);
312   }
313 
314   void clear_archived_mirror_index() NOT_CDS_JAVA_HEAP_RETURN;
315 
316   void set_lambda_proxy_is_available() {
317     CDS_ONLY(_shared_class_flags |= _archived_lambda_proxy_is_available;)
318   }
319   void clear_lambda_proxy_is_available() {
320     CDS_ONLY(_shared_class_flags &= ~_archived_lambda_proxy_is_available;)
321   }
322   bool lambda_proxy_is_available() const {
323     CDS_ONLY(return (_shared_class_flags & _archived_lambda_proxy_is_available) != 0;)
324     NOT_CDS(return false;)
325   }
326 
327   void set_has_value_based_class_annotation() {
328     CDS_ONLY(_shared_class_flags |= _has_value_based_class_annotation;)
329   }
330   void clear_has_value_based_class_annotation() {
331     CDS_ONLY(_shared_class_flags &= ~_has_value_based_class_annotation;)
332   }
333   bool has_value_based_class_annotation() const {
334     CDS_ONLY(return (_shared_class_flags & _has_value_based_class_annotation) != 0;)
335     NOT_CDS(return false;)
336   }
337 
338   void set_verified_at_dump_time() {
339     CDS_ONLY(_shared_class_flags |= _verified_at_dump_time;)
340   }
341   bool verified_at_dump_time() const {
342     CDS_ONLY(return (_shared_class_flags & _verified_at_dump_time) != 0;)
343     NOT_CDS(return false;)
344   }
345 
346   void set_has_archived_enum_objs() {
347     CDS_ONLY(_shared_class_flags |= _has_archived_enum_objs;)
348   }
349   bool has_archived_enum_objs() const {
350     CDS_ONLY(return (_shared_class_flags & _has_archived_enum_objs) != 0;)
351     NOT_CDS(return false;)
352   }
353 
354   void set_regenerated() {
355     CDS_ONLY(_shared_class_flags |= _regenerated;)
356   }
357   bool is_regenerated() const {
358     CDS_ONLY(return (_shared_class_flags & _regenerated) != 0;)
359     NOT_CDS(return false;)
360   }
361 
362   // Obtain the module or package for this class
363   virtual ModuleEntry* module() const = 0;
364   virtual PackageEntry* package() const = 0;
365 
366  protected:                                // internal accessors
367   void     set_subklass(Klass* s);
368   void     set_next_sibling(Klass* s);
369 
370  public:
371 
372   // Compiler support
373   static ByteSize super_offset()                 { return in_ByteSize(offset_of(Klass, _super)); }
374   static ByteSize super_check_offset_offset()    { return in_ByteSize(offset_of(Klass, _super_check_offset)); }
375   static ByteSize primary_supers_offset()        { return in_ByteSize(offset_of(Klass, _primary_supers)); }
376   static ByteSize secondary_super_cache_offset() { return in_ByteSize(offset_of(Klass, _secondary_super_cache)); }
377   static ByteSize secondary_supers_offset()      { return in_ByteSize(offset_of(Klass, _secondary_supers)); }
378   static ByteSize java_mirror_offset()           { return in_ByteSize(offset_of(Klass, _java_mirror)); }
379   static ByteSize class_loader_data_offset()     { return in_ByteSize(offset_of(Klass, _class_loader_data)); }
380   static ByteSize modifier_flags_offset()        { return in_ByteSize(offset_of(Klass, _modifier_flags)); }
381   static ByteSize layout_helper_offset()         { return in_ByteSize(offset_of(Klass, _layout_helper)); }
382   static ByteSize access_flags_offset()          { return in_ByteSize(offset_of(Klass, _access_flags)); }
383 
384   // Unpacking layout_helper:
385   static const int _lh_neutral_value           = 0;  // neutral non-array non-instance value
386   static const int _lh_instance_slow_path_bit  = 0x01;
387   static const int _lh_log2_element_size_shift = BitsPerByte*0;
388   static const int _lh_log2_element_size_mask  = BitsPerLong-1;
389   static const int _lh_element_type_shift      = BitsPerByte*1;
390   static const int _lh_element_type_mask       = right_n_bits(BitsPerByte);  // shifted mask
391   static const int _lh_header_size_shift       = BitsPerByte*2;
392   static const int _lh_header_size_mask        = right_n_bits(BitsPerByte);  // shifted mask
393   static const int _lh_array_tag_bits          = 3;
394   static const int _lh_array_tag_shift         = BitsPerInt - _lh_array_tag_bits;
395 
396   static const unsigned int _lh_array_tag_type_value = 0Xfffffffc;
397   static const unsigned int _lh_array_tag_vt_value   = 0Xfffffffd;
398   static const unsigned int _lh_array_tag_obj_value  = 0Xfffffffe;
399 
400   // null-free array flag bit under the array tag bits, shift one more to get array tag value
401   static const int _lh_null_free_shift = _lh_array_tag_shift - 1;
402   static const int _lh_null_free_mask  = 1;
403 
404   static const jint _lh_array_tag_flat_value_bit_inplace = (jint) (1 << _lh_array_tag_shift);
405   static const jint _lh_null_free_array_bit_inplace = (jint) (_lh_null_free_mask << _lh_null_free_shift);
406 
407   static int layout_helper_size_in_bytes(jint lh) {
408     assert(lh > (jint)_lh_neutral_value, "must be instance");
409     return (int) lh & ~_lh_instance_slow_path_bit;
410   }
411   static bool layout_helper_needs_slow_path(jint lh) {
412     assert(lh > (jint)_lh_neutral_value, "must be instance");
413     return (lh & _lh_instance_slow_path_bit) != 0;
414   }
415   static bool layout_helper_is_instance(jint lh) {
416     return (jint)lh > (jint)_lh_neutral_value;
417   }
418   static bool layout_helper_is_array(jint lh) {
419     return (jint)lh < (jint)_lh_neutral_value;
420   }
421   static bool layout_helper_is_typeArray(jint lh) {
422     return (juint) _lh_array_tag_type_value == (juint)(lh >> _lh_array_tag_shift);
423   }
424   static bool layout_helper_is_objArray(jint lh) {
425     return (juint)_lh_array_tag_obj_value == (juint)(lh >> _lh_array_tag_shift);
426   }
427   static bool layout_helper_is_flatArray(jint lh) {
428     return (juint)_lh_array_tag_vt_value == (juint)(lh >> _lh_array_tag_shift);
429   }
430   static bool layout_helper_is_null_free(jint lh) {
431     assert(layout_helper_is_flatArray(lh) || layout_helper_is_objArray(lh), "must be array of inline types");
432     return ((lh >> _lh_null_free_shift) & _lh_null_free_mask);
433   }
434   static jint layout_helper_set_null_free(jint lh) {
435     lh |= (_lh_null_free_mask << _lh_null_free_shift);
436     assert(layout_helper_is_null_free(lh), "Bad encoding");
437     return lh;
438   }
439   static int layout_helper_header_size(jint lh) {
440     assert(lh < (jint)_lh_neutral_value, "must be array");
441     int hsize = (lh >> _lh_header_size_shift) & _lh_header_size_mask;
442     assert(hsize > 0 && hsize < (int)sizeof(oopDesc)*3, "sanity");
443     return hsize;
444   }
445   static BasicType layout_helper_element_type(jint lh) {
446     assert(lh < (jint)_lh_neutral_value, "must be array");
447     int btvalue = (lh >> _lh_element_type_shift) & _lh_element_type_mask;
448     assert((btvalue >= T_BOOLEAN && btvalue <= T_OBJECT) || btvalue == T_PRIMITIVE_OBJECT, "sanity");
449     return (BasicType) btvalue;
450   }
451 
452   // Want a pattern to quickly diff against layout header in register
453   // find something less clever!
454   static int layout_helper_boolean_diffbit() {
455     jint zlh = array_layout_helper(T_BOOLEAN);
456     jint blh = array_layout_helper(T_BYTE);
457     assert(zlh != blh, "array layout helpers must differ");
458     int diffbit = 1;
459     while ((diffbit & (zlh ^ blh)) == 0 && (diffbit & zlh) == 0) {
460       diffbit <<= 1;
461       assert(diffbit != 0, "make sure T_BOOLEAN has a different bit than T_BYTE");
462     }
463     return diffbit;
464   }
465 
466   static int layout_helper_log2_element_size(jint lh) {
467     assert(lh < (jint)_lh_neutral_value, "must be array");
468     int l2esz = (lh >> _lh_log2_element_size_shift) & _lh_log2_element_size_mask;
469     assert(layout_helper_element_type(lh) == T_PRIMITIVE_OBJECT || l2esz <= LogBytesPerLong,
470            "sanity. l2esz: 0x%x for lh: 0x%x", (uint)l2esz, (uint)lh);
471     return l2esz;
472   }
473   static jint array_layout_helper(jint tag, bool null_free, int hsize, BasicType etype, int log2_esize) {
474     return (tag        << _lh_array_tag_shift)
475       |    ((null_free ? 1 : 0) <<  _lh_null_free_shift)
476       |    (hsize      << _lh_header_size_shift)
477       |    ((int)etype << _lh_element_type_shift)
478       |    (log2_esize << _lh_log2_element_size_shift);
479   }
480   static jint instance_layout_helper(jint size, bool slow_path_flag) {
481     return (size << LogBytesPerWord)
482       |    (slow_path_flag ? _lh_instance_slow_path_bit : 0);
483   }
484   static int layout_helper_to_size_helper(jint lh) {
485     assert(lh > (jint)_lh_neutral_value, "must be instance");
486     // Note that the following expression discards _lh_instance_slow_path_bit.
487     return lh >> LogBytesPerWord;
488   }
489   // Out-of-line version computes everything based on the etype:
490   static jint array_layout_helper(BasicType etype);
491 
492   // What is the maximum number of primary superclasses any klass can have?
493   static juint primary_super_limit()         { return _primary_super_limit; }
494 
495   // vtables
496   klassVtable vtable() const;
497   int vtable_length() const { return _vtable_len; }
498 
499   // subclass check
500   bool is_subclass_of(const Klass* k) const;
501   // subtype check: true if is_subclass_of, or if k is interface and receiver implements it
502   bool is_subtype_of(Klass* k) const {
503     juint    off = k->super_check_offset();
504     Klass* sup = *(Klass**)( (address)this + off );
505     const juint secondary_offset = in_bytes(secondary_super_cache_offset());
506     if (sup == k) {
507       return true;
508     } else if (off != secondary_offset) {
509       return false;
510     } else {
511       return search_secondary_supers(k);
512     }
513   }
514 
515   bool search_secondary_supers(Klass* k) const;
516 
517   // Find LCA in class hierarchy
518   Klass *LCA( Klass *k );
519 
520   // Check whether reflection/jni/jvm code is allowed to instantiate this class;
521   // if not, throw either an Error or an Exception.
522   virtual void check_valid_for_instantiation(bool throwError, TRAPS);
523 
524   // array copying
525   virtual void  copy_array(arrayOop s, int src_pos, arrayOop d, int dst_pos, int length, TRAPS);
526 
527   // tells if the class should be initialized
528   virtual bool should_be_initialized() const    { return false; }
529   // initializes the klass
530   virtual void initialize(TRAPS);
531   virtual Klass* find_field(Symbol* name, Symbol* signature, fieldDescriptor* fd) const;
532   virtual Method* uncached_lookup_method(const Symbol* name, const Symbol* signature,
533                                          OverpassLookupMode overpass_mode,
534                                          PrivateLookupMode = PrivateLookupMode::find) const;
535  public:
536   Method* lookup_method(const Symbol* name, const Symbol* signature) const {
537     return uncached_lookup_method(name, signature, OverpassLookupMode::find);
538   }
539 
540   // array class with specific rank
541   virtual Klass* array_klass(int rank, TRAPS) = 0;
542 
543   // array class with this klass as element type
544   virtual Klass* array_klass(TRAPS) = 0;
545 
546   // These will return NULL instead of allocating on the heap:
547   virtual Klass* array_klass_or_null(int rank) = 0;
548   virtual Klass* array_klass_or_null() = 0;
549 
550   virtual oop protection_domain() const = 0;
551 
552   oop class_loader() const;
553 
554   inline oop klass_holder() const;
555 
556  protected:
557 
558   // Error handling when length > max_length or length < 0
559   static void check_array_allocation_length(int length, int max_length, TRAPS);
560 
561   void set_vtable_length(int len) { _vtable_len= len; }
562 
563   vtableEntry* start_of_vtable() const;
564   void restore_unshareable_info(ClassLoaderData* loader_data, Handle protection_domain, TRAPS);
565  public:
566   Method* method_at_vtable(int index);
567 
568   static ByteSize vtable_start_offset();
569   static ByteSize vtable_length_offset() {
570     return byte_offset_of(Klass, _vtable_len);
571   }
572 
573   // CDS support - remove and restore oops from metadata. Oops are not shared.
574   virtual void remove_unshareable_info();
575   virtual void remove_java_mirror();
576 
577   bool is_unshareable_info_restored() const {
578     assert(is_shared(), "use this for shared classes only");
579     if (has_archived_mirror_index()) {
580       // _java_mirror is not a valid OopHandle but rather an encoded reference in the shared heap
581       return false;
582     } else if (_java_mirror.ptr_raw() == NULL) {
583       return false;
584     } else {
585       return true;
586     }
587   }
588 
589  public:
590   // ALL FUNCTIONS BELOW THIS POINT ARE DISPATCHED FROM AN OOP
591   // These functions describe behavior for the oop not the KLASS.
592 
593   // actual oop size of obj in memory in word size.
594   virtual size_t oop_size(oop obj) const = 0;
595 
596   // Size of klass in word size.
597   virtual int size() const = 0;
598 
599   // Returns the Java name for a class (Resource allocated)
600   // For arrays, this returns the name of the element with a leading '['.
601   // For classes, this returns the name with the package separators
602   //     turned into '.'s.
603   const char* external_name() const;
604   // Returns the name for a class (Resource allocated) as the class
605   // would appear in a signature.
606   // For arrays, this returns the name of the element with a leading '['.
607   // For classes, this returns the name with a leading 'L' and a trailing ';'
608   //     and the package separators as '/'.
609   virtual const char* signature_name() const;
610 
611   const char* joint_in_module_of_loader(const Klass* class2, bool include_parent_loader = false) const;
612   const char* class_in_module_of_loader(bool use_are = false, bool include_parent_loader = false) const;
613 
614   // Returns "interface", "abstract class" or "class".
615   const char* external_kind() const;
616 
617   // type testing operations
618 #ifdef ASSERT
619  protected:
620   virtual bool is_instance_klass_slow()     const { return false; }
621   virtual bool is_array_klass_slow()        const { return false; }
622   virtual bool is_objArray_klass_slow()     const { return false; }
623   virtual bool is_typeArray_klass_slow()    const { return false; }
624   virtual bool is_flatArray_klass_slow()    const { return false; }
625 #endif // ASSERT
626   // current implementation uses this method even in non debug builds
627   virtual bool is_inline_klass_slow()       const { return false; }
628  public:
629 
630   // Fast non-virtual versions
631   #ifndef ASSERT
632   #define assert_same_query(xval, xcheck) xval
633   #else
634  private:
635   static bool assert_same_query(bool xval, bool xslow) {
636     assert(xval == xslow, "slow and fast queries agree");
637     return xval;
638   }
639  public:
640   #endif
641   inline  bool is_instance_klass()            const { return assert_same_query(
642                                                       layout_helper_is_instance(layout_helper()),
643                                                       is_instance_klass_slow()); }
644   inline  bool is_array_klass()               const { return assert_same_query(
645                                                     layout_helper_is_array(layout_helper()),
646                                                     is_array_klass_slow()); }
647   inline  bool is_objArray_klass()            const { return assert_same_query(
648                                                     layout_helper_is_objArray(layout_helper()),
649                                                     is_objArray_klass_slow()); }
650   inline  bool is_typeArray_klass()           const { return assert_same_query(
651                                                     layout_helper_is_typeArray(layout_helper()),
652                                                     is_typeArray_klass_slow()); }
653   inline  bool is_inline_klass()              const { return is_inline_klass_slow(); } //temporary hack
654   inline  bool is_flatArray_klass()           const { return assert_same_query(
655                                                     layout_helper_is_flatArray(layout_helper()),
656                                                     is_flatArray_klass_slow()); }
657 
658   #undef assert_same_query
659 
660   inline bool is_null_free_array_klass()      const { return layout_helper_is_null_free(layout_helper()); }
661 
662   // Access flags
663   AccessFlags access_flags() const         { return _access_flags;  }
664   void set_access_flags(AccessFlags flags) { _access_flags = flags; }
665 
666   bool is_public() const                { return _access_flags.is_public(); }
667   bool is_final() const                 { return _access_flags.is_final(); }
668   bool is_interface() const             { return _access_flags.is_interface(); }
669   bool is_abstract() const              { return _access_flags.is_abstract(); }
670   bool is_super() const                 { return _access_flags.is_super(); }
671   bool is_synthetic() const             { return _access_flags.is_synthetic(); }
672   bool is_permits_value_class() const   { return _access_flags.is_permits_value_class(); }
673   bool is_identity_class() const        { return _access_flags.is_identity_class(); }
674   void set_is_synthetic()               { _access_flags.set_is_synthetic(); }
675   bool has_finalizer() const            { return _access_flags.has_finalizer(); }
676   bool has_final_method() const         { return _access_flags.has_final_method(); }
677   void set_has_finalizer()              { _access_flags.set_has_finalizer(); }
678   void set_has_final_method()           { _access_flags.set_has_final_method(); }
679   bool has_vanilla_constructor() const  { return _access_flags.has_vanilla_constructor(); }
680   void set_has_vanilla_constructor()    { _access_flags.set_has_vanilla_constructor(); }
681   bool has_miranda_methods () const     { return access_flags().has_miranda_methods(); }
682   void set_has_miranda_methods()        { _access_flags.set_has_miranda_methods(); }
683   bool is_shared() const                { return access_flags().is_shared_class(); } // shadows MetaspaceObj::is_shared)()
684   void set_is_shared()                  { _access_flags.set_is_shared_class(); }
685   bool is_hidden() const                { return access_flags().is_hidden_class(); }
686   void set_is_hidden()                  { _access_flags.set_is_hidden_class(); }
687   bool is_value_based()                 { return _access_flags.is_value_based_class(); }
688   void set_is_value_based()             { _access_flags.set_is_value_based_class(); }
689 
690   inline bool is_non_strong_hidden() const;
691 
692   bool is_cloneable() const;
693   void set_is_cloneable();
694 
695   // inline types and inline type array patterns
696   markWord prototype_header() const {
697     return _prototype_header;
698   }
699   static inline markWord default_prototype_header(Klass* k) {
700     return (k == NULL) ? markWord::prototype() : k->prototype_header();
701   }
702 
703   inline void set_prototype_header(markWord header);
704   static ByteSize prototype_header_offset() { return in_ByteSize(offset_of(Klass, _prototype_header)); }
705 
706   JFR_ONLY(DEFINE_TRACE_ID_METHODS;)
707 
708   virtual void metaspace_pointers_do(MetaspaceClosure* iter);
709   virtual MetaspaceObj::Type type() const { return ClassType; }
710 
711   inline bool is_loader_alive() const;
712 
713   void clean_subklass();
714 
715   static void clean_weak_klass_links(bool unloading_occurred, bool clean_alive_klasses = true);
716   static void clean_subklass_tree() {
717     clean_weak_klass_links(/*unloading_occurred*/ true , /* clean_alive_klasses */ false);
718   }
719 
720   // Return self, except for abstract classes with exactly 1
721   // implementor.  Then return the 1 concrete implementation.
722   Klass *up_cast_abstract();
723 
724   // klass name
725   Symbol* name() const                   { return _name; }
726   void set_name(Symbol* n);
727 
728   virtual void release_C_heap_structures(bool release_constant_pool = true);
729 
730  public:
731   virtual jint compute_modifier_flags() const = 0;
732 
733   // JVMTI support
734   virtual jint jvmti_class_status() const;
735 
736   // Printing
737   virtual void print_on(outputStream* st) const;
738 
739   virtual void oop_print_value_on(oop obj, outputStream* st);
740   virtual void oop_print_on      (oop obj, outputStream* st);
741 
742   virtual const char* internal_name() const = 0;
743 
744   // Verification
745   virtual void verify_on(outputStream* st);
746   void verify() { verify_on(tty); }
747 
748 #ifndef PRODUCT
749   bool verify_vtable_index(int index);
750 #endif
751 
752   virtual void oop_verify_on(oop obj, outputStream* st);
753 
754   // for error reporting
755   static bool is_valid(Klass* k);
756 };
757 
758 #endif // SHARE_OOPS_KLASS_HPP