1 /*
  2  * Copyright (c) 1997, 2023, 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 //
 41 // A Klass provides:
 42 //  1: language level class object (method dictionary etc.)
 43 //  2: provide vm dispatch behavior for the object
 44 // Both functions are combined into one C++ class.
 45 
 46 // One reason for the oop/klass dichotomy in the implementation is
 47 // that we don't want a C++ vtbl pointer in every object.  Thus,
 48 // normal oops don't have any virtual functions.  Instead, they
 49 // forward all "virtual" functions to their klass, which does have
 50 // a vtbl and does the C++ dispatch depending on the object's
 51 // actual type.  (See oop.inline.hpp for some of the forwarding code.)
 52 // ALL FUNCTIONS IMPLEMENTING THIS DISPATCH ARE PREFIXED WITH "oop_"!
 53 
 54 // Forward declarations.
 55 template <class T> class Array;
 56 template <class T> class GrowableArray;
 57 class ClassLoaderData;
 58 class fieldDescriptor;
 59 class klassVtable;
 60 class ModuleEntry;
 61 class PackageEntry;
 62 class ParCompactionManager;
 63 class PSPromotionManager;
 64 class vtableEntry;
 65 
 66 class Klass : public Metadata {
 67   friend class VMStructs;
 68   friend class JVMCIVMStructs;
 69  public:
 70   // Klass Kinds for all subclasses of Klass
 71   enum KlassKind {
 72     InstanceKlassKind,
 73     InlineKlassKind,
 74     InstanceRefKlassKind,
 75     InstanceMirrorKlassKind,
 76     InstanceClassLoaderKlassKind,
 77     InstanceStackChunkKlassKind,
 78     TypeArrayKlassKind,
 79     FlatArrayKlassKind,
 80     ObjArrayKlassKind,
 81     UnknownKlassKind
 82   };
 83 
 84   static const uint KLASS_KIND_COUNT = ObjArrayKlassKind + 1;
 85  protected:
 86 
 87   // If you add a new field that points to any metaspace object, you
 88   // must add this field to Klass::metaspace_pointers_do().
 89 
 90   // note: put frequently-used fields together at start of klass structure
 91   // for better cache behavior (may not make much of a difference but sure won't hurt)
 92   enum { _primary_super_limit = 8 };
 93 
 94   // The "layout helper" is a combined descriptor of object layout.
 95   // For klasses which are neither instance nor array, the value is zero.
 96   //
 97   // For instances, layout helper is a positive number, the instance size.
 98   // This size is already passed through align_object_size and scaled to bytes.
 99   // The low order bit is set if instances of this class cannot be
100   // allocated using the fastpath.
101   //
102   // For arrays, layout helper is a negative number, containing four
103   // distinct bytes, as follows:
104   //    MSB:[tag, hsz, ebt, log2(esz)]:LSB
105   // where:
106   //    tag is 0x80 if the elements are oops, 0xC0 if non-oops, 0xA0 if value types
107   //    hsz is array header size in bytes (i.e., offset of first element)
108   //    ebt is the BasicType of the elements
109   //    esz is the element size in bytes
110   // This packed word is arranged so as to be quickly unpacked by the
111   // various fast paths that use the various subfields.
112   //
113   // The esz bits can be used directly by a SLL instruction, without masking.
114   //
115   // Note that the array-kind tag looks like 0x00 for instance klasses,
116   // since their length in bytes is always less than 24Mb.
117   //
118   // Final note:  This comes first, immediately after C++ vtable,
119   // because it is frequently queried.
120   jint        _layout_helper;
121 
122   // Klass kind used to resolve the runtime type of the instance.
123   //  - Used to implement devirtualized oop closure dispatching.
124   //  - Various type checking in the JVM
125   const KlassKind _kind;
126 
127   // Processed access flags, for use by Class.getModifiers.
128   jint        _modifier_flags;
129 
130   // The fields _super_check_offset, _secondary_super_cache, _secondary_supers
131   // and _primary_supers all help make fast subtype checks.  See big discussion
132   // in doc/server_compiler/checktype.txt
133   //
134   // Where to look to observe a supertype (it is &_secondary_super_cache for
135   // secondary supers, else is &_primary_supers[depth()].
136   juint       _super_check_offset;
137 
138   // Class name.  Instance classes: java/lang/String, etc.  Array classes: [I,
139   // [Ljava/lang/String;, etc.  Set to zero for all other kinds of classes.
140   Symbol*     _name;
141 
142   // Cache of last observed secondary supertype
143   Klass*      _secondary_super_cache;
144   // Array of all secondary supertypes
145   Array<Klass*>* _secondary_supers;
146   // Ordered list of all primary supertypes
147   Klass*      _primary_supers[_primary_super_limit];
148   // java/lang/Class instance mirroring this class
149   OopHandle   _java_mirror;
150   // Superclass
151   Klass*      _super;
152   // First subclass (null if none); _subklass->next_sibling() is next one
153   Klass* volatile _subklass;
154   // Sibling link (or null); links all subklasses of a klass
155   Klass* volatile _next_sibling;
156 
157   // All klasses loaded by a class loader are chained through these links
158   Klass*      _next_link;
159 
160   // The VM's representation of the ClassLoader used to load this class.
161   // Provide access the corresponding instance java.lang.ClassLoader.
162   ClassLoaderData* _class_loader_data;
163 
164   int _vtable_len;              // vtable length. This field may be read very often when we
165                                 // have lots of itable dispatches (e.g., lambdas and streams).
166                                 // Keep it away from the beginning of a Klass to avoid cacheline
167                                 // contention that may happen when a nearby object is modified.
168   AccessFlags _access_flags;    // Access flags. The class/interface distinction is stored here.
169 
170   JFR_ONLY(DEFINE_TRACE_ID_FIELD;)
171 
172   markWord _prototype_header;  // inline type and inline array mark patterns
173 private:
174   // This is an index into FileMapHeader::_shared_path_table[], to
175   // associate this class with the JAR file where it's loaded from during
176   // dump time. If a class is not loaded from the shared archive, this field is
177   // -1.
178   s2 _shared_class_path_index;
179 
180 #if INCLUDE_CDS
181   // Various attributes for shared classes. Should be zero for a non-shared class.
182   u2     _shared_class_flags;
183   enum CDSSharedClassFlags {
184     _is_shared_class                       = 1 << 0,  // shadows MetaspaceObj::is_shared
185     _archived_lambda_proxy_is_available    = 1 << 1,
186     _has_value_based_class_annotation      = 1 << 2,
187     _verified_at_dump_time                 = 1 << 3,
188     _has_archived_enum_objs                = 1 << 4,
189     // This class was not loaded from a classfile in the module image
190     // or classpath.
191     _is_generated_shared_class             = 1 << 5
192   };
193 #endif
194 
195   CDS_JAVA_HEAP_ONLY(int _archived_mirror_index;)
196 
197 protected:
198 
199   // Constructor
200   Klass(KlassKind kind);
201   Klass() : _kind(UnknownKlassKind) { assert(DumpSharedSpaces || UseSharedSpaces, "only for cds"); }
202 
203   void* operator new(size_t size, ClassLoaderData* loader_data, size_t word_size, TRAPS) throw();
204 
205  public:
206   int kind() { return _kind; }
207 
208   enum class DefaultsLookupMode { find, skip };
209   enum class OverpassLookupMode { find, skip };
210   enum class StaticLookupMode   { find, skip };
211   enum class PrivateLookupMode  { find, skip };
212 
213   virtual bool is_klass() const { return true; }
214 
215   // super() cannot be InstanceKlass* -- Java arrays are covariant, and _super is used
216   // to implement that. NB: the _super of "[Ljava/lang/Integer;" is "[Ljava/lang/Number;"
217   // If this is not what your code expects, you're probably looking for Klass::java_super().
218   Klass* super() const               { return _super; }
219   void set_super(Klass* k)           { _super = k; }
220 
221   // initializes _super link, _primary_supers & _secondary_supers arrays
222   void initialize_supers(Klass* k, Array<InstanceKlass*>* transitive_interfaces, TRAPS);
223 
224   // klass-specific helper for initializing _secondary_supers
225   virtual GrowableArray<Klass*>* compute_secondary_supers(int num_extra_slots,
226                                                           Array<InstanceKlass*>* transitive_interfaces);
227 
228   // java_super is the Java-level super type as specified by Class.getSuperClass.
229   virtual InstanceKlass* java_super() const  { return nullptr; }
230 
231   juint    super_check_offset() const  { return _super_check_offset; }
232   void set_super_check_offset(juint o) { _super_check_offset = o; }
233 
234   Klass* secondary_super_cache() const     { return _secondary_super_cache; }
235   void set_secondary_super_cache(Klass* k) { _secondary_super_cache = k; }
236 
237   Array<Klass*>* secondary_supers() const { return _secondary_supers; }
238   void set_secondary_supers(Array<Klass*>* k) { _secondary_supers = k; }
239 
240   // Return the element of the _super chain of the given depth.
241   // If there is no such element, return either null or this.
242   Klass* primary_super_of_depth(juint i) const {
243     assert(i < primary_super_limit(), "oob");
244     Klass* super = _primary_supers[i];
245     assert(super == nullptr || super->super_depth() == i, "correct display");
246     return super;
247   }
248 
249   // Can this klass be a primary super?  False for interfaces and arrays of
250   // interfaces.  False also for arrays or classes with long super chains.
251   bool can_be_primary_super() const {
252     const juint secondary_offset = in_bytes(secondary_super_cache_offset());
253     return super_check_offset() != secondary_offset;
254   }
255   virtual bool can_be_primary_super_slow() const;
256 
257   // Returns number of primary supers; may be a number in the inclusive range [0, primary_super_limit].
258   juint super_depth() const {
259     if (!can_be_primary_super()) {
260       return primary_super_limit();
261     } else {
262       juint d = (super_check_offset() - in_bytes(primary_supers_offset())) / sizeof(Klass*);
263       assert(d < primary_super_limit(), "oob");
264       assert(_primary_supers[d] == this, "proper init");
265       return d;
266     }
267   }
268 
269   // java mirror
270   oop java_mirror() const;
271   oop java_mirror_no_keepalive() const;
272   void set_java_mirror(Handle m);
273 
274   oop archived_java_mirror() NOT_CDS_JAVA_HEAP_RETURN_(nullptr);
275   void set_archived_java_mirror(int mirror_index) NOT_CDS_JAVA_HEAP_RETURN;
276 
277   // Temporary mirror switch used by RedefineClasses
278   OopHandle java_mirror_handle() const { return _java_mirror; }
279   void swap_java_mirror_handle(OopHandle& mirror) { _java_mirror.swap(mirror); }
280 
281   // Set java mirror OopHandle to null for CDS
282   // This leaves the OopHandle in the CLD, but that's ok, you can't release them.
283   void clear_java_mirror_handle() { _java_mirror = OopHandle(); }
284 
285   // modifier flags
286   jint modifier_flags() const          { return _modifier_flags; }
287   void set_modifier_flags(jint flags)  { _modifier_flags = flags; }
288 
289   // size helper
290   int layout_helper() const            { return _layout_helper; }
291   void set_layout_helper(int lh)       { _layout_helper = lh; }
292 
293   // Note: for instances layout_helper() may include padding.
294   // Use InstanceKlass::contains_field_offset to classify field offsets.
295 
296   // sub/superklass links
297   Klass* subklass(bool log = false) const;
298   Klass* next_sibling(bool log = false) const;
299 
300   InstanceKlass* superklass() const;
301   void append_to_sibling_list();           // add newly created receiver to superklass' subklass list
302 
303   void set_next_link(Klass* k) { _next_link = k; }
304   Klass* next_link() const { return _next_link; }   // The next klass defined by the class loader.
305   Klass** next_link_addr() { return &_next_link; }
306 
307   // class loader data
308   ClassLoaderData* class_loader_data() const               { return _class_loader_data; }
309   void set_class_loader_data(ClassLoaderData* loader_data) {  _class_loader_data = loader_data; }
310 
311   s2 shared_classpath_index() const   {
312     return _shared_class_path_index;
313   };
314 
315   void set_shared_classpath_index(s2 index) {
316     _shared_class_path_index = index;
317   };
318 
319   bool has_archived_mirror_index() const {
320     CDS_JAVA_HEAP_ONLY(return _archived_mirror_index >= 0;)
321     NOT_CDS_JAVA_HEAP(return false);
322   }
323 
324   void clear_archived_mirror_index() NOT_CDS_JAVA_HEAP_RETURN;
325 
326   void set_lambda_proxy_is_available() {
327     CDS_ONLY(_shared_class_flags |= _archived_lambda_proxy_is_available;)
328   }
329   void clear_lambda_proxy_is_available() {
330     CDS_ONLY(_shared_class_flags &= (u2)(~_archived_lambda_proxy_is_available);)
331   }
332   bool lambda_proxy_is_available() const {
333     CDS_ONLY(return (_shared_class_flags & _archived_lambda_proxy_is_available) != 0;)
334     NOT_CDS(return false;)
335   }
336 
337   void set_has_value_based_class_annotation() {
338     CDS_ONLY(_shared_class_flags |= _has_value_based_class_annotation;)
339   }
340   void clear_has_value_based_class_annotation() {
341     CDS_ONLY(_shared_class_flags &= (u2)(~_has_value_based_class_annotation);)
342   }
343   bool has_value_based_class_annotation() const {
344     CDS_ONLY(return (_shared_class_flags & _has_value_based_class_annotation) != 0;)
345     NOT_CDS(return false;)
346   }
347 
348   void set_verified_at_dump_time() {
349     CDS_ONLY(_shared_class_flags |= _verified_at_dump_time;)
350   }
351   bool verified_at_dump_time() const {
352     CDS_ONLY(return (_shared_class_flags & _verified_at_dump_time) != 0;)
353     NOT_CDS(return false;)
354   }
355 
356   void set_has_archived_enum_objs() {
357     CDS_ONLY(_shared_class_flags |= _has_archived_enum_objs;)
358   }
359   bool has_archived_enum_objs() const {
360     CDS_ONLY(return (_shared_class_flags & _has_archived_enum_objs) != 0;)
361     NOT_CDS(return false;)
362   }
363 
364   void set_is_generated_shared_class() {
365     CDS_ONLY(_shared_class_flags |= _is_generated_shared_class;)
366   }
367   bool is_generated_shared_class() const {
368     CDS_ONLY(return (_shared_class_flags & _is_generated_shared_class) != 0;)
369     NOT_CDS(return false;)
370   }
371 
372   bool is_shared() const                { // shadows MetaspaceObj::is_shared)()
373     CDS_ONLY(return (_shared_class_flags & _is_shared_class) != 0;)
374     NOT_CDS(return false;)
375   }
376 
377   void set_is_shared() {
378     CDS_ONLY(_shared_class_flags |= _is_shared_class;)
379   }
380 
381   // Obtain the module or package for this class
382   virtual ModuleEntry* module() const = 0;
383   virtual PackageEntry* package() const = 0;
384 
385  protected:                                // internal accessors
386   void     set_subklass(Klass* s);
387   void     set_next_sibling(Klass* s);
388 
389  public:
390 
391   // Compiler support
392   static ByteSize super_offset()                 { return byte_offset_of(Klass, _super); }
393   static ByteSize super_check_offset_offset()    { return byte_offset_of(Klass, _super_check_offset); }
394   static ByteSize primary_supers_offset()        { return byte_offset_of(Klass, _primary_supers); }
395   static ByteSize secondary_super_cache_offset() { return byte_offset_of(Klass, _secondary_super_cache); }
396   static ByteSize secondary_supers_offset()      { return byte_offset_of(Klass, _secondary_supers); }
397   static ByteSize java_mirror_offset()           { return byte_offset_of(Klass, _java_mirror); }
398   static ByteSize class_loader_data_offset()     { return byte_offset_of(Klass, _class_loader_data); }
399   static ByteSize modifier_flags_offset()        { return byte_offset_of(Klass, _modifier_flags); }
400   static ByteSize layout_helper_offset()         { return byte_offset_of(Klass, _layout_helper); }
401   static ByteSize access_flags_offset()          { return byte_offset_of(Klass, _access_flags); }
402 #if INCLUDE_JVMCI
403   static ByteSize subklass_offset()              { return byte_offset_of(Klass, _subklass); }
404   static ByteSize next_sibling_offset()          { return byte_offset_of(Klass, _next_sibling); }
405 #endif
406 
407   // Unpacking layout_helper:
408   static const int _lh_neutral_value           = 0;  // neutral non-array non-instance value
409   static const int _lh_instance_slow_path_bit  = 0x01;
410   static const int _lh_log2_element_size_shift = BitsPerByte*0;
411   static const int _lh_log2_element_size_mask  = BitsPerLong-1;
412   static const int _lh_element_type_shift      = BitsPerByte*1;
413   static const int _lh_element_type_mask       = right_n_bits(BitsPerByte);  // shifted mask
414   static const int _lh_header_size_shift       = BitsPerByte*2;
415   static const int _lh_header_size_mask        = right_n_bits(BitsPerByte);  // shifted mask
416   static const int _lh_array_tag_bits          = 3;
417   static const int _lh_array_tag_shift         = BitsPerInt - _lh_array_tag_bits;
418 
419   static const unsigned int _lh_array_tag_type_value = 0Xfffffffc;
420   static const unsigned int _lh_array_tag_vt_value   = 0Xfffffffd;
421   static const unsigned int _lh_array_tag_obj_value  = 0Xfffffffe;
422 
423   // null-free array flag bit under the array tag bits, shift one more to get array tag value
424   static const int _lh_null_free_shift = _lh_array_tag_shift - 1;
425   static const int _lh_null_free_mask  = 1;
426 
427   static const jint _lh_array_tag_flat_value_bit_inplace = (jint) (1 << _lh_array_tag_shift);
428   static const jint _lh_null_free_array_bit_inplace = (jint) (_lh_null_free_mask << _lh_null_free_shift);
429 
430   static int layout_helper_size_in_bytes(jint lh) {
431     assert(lh > (jint)_lh_neutral_value, "must be instance");
432     return (int) lh & ~_lh_instance_slow_path_bit;
433   }
434   static bool layout_helper_needs_slow_path(jint lh) {
435     assert(lh > (jint)_lh_neutral_value, "must be instance");
436     return (lh & _lh_instance_slow_path_bit) != 0;
437   }
438   static bool layout_helper_is_instance(jint lh) {
439     return (jint)lh > (jint)_lh_neutral_value;
440   }
441   static bool layout_helper_is_array(jint lh) {
442     return (jint)lh < (jint)_lh_neutral_value;
443   }
444   static bool layout_helper_is_typeArray(jint lh) {
445     return (juint) _lh_array_tag_type_value == (juint)(lh >> _lh_array_tag_shift);
446   }
447   static bool layout_helper_is_objArray(jint lh) {
448     return (juint)_lh_array_tag_obj_value == (juint)(lh >> _lh_array_tag_shift);
449   }
450   static bool layout_helper_is_flatArray(jint lh) {
451     return (juint)_lh_array_tag_vt_value == (juint)(lh >> _lh_array_tag_shift);
452   }
453   static bool layout_helper_is_null_free(jint lh) {
454     assert(layout_helper_is_flatArray(lh) || layout_helper_is_objArray(lh), "must be array of inline types");
455     return ((lh >> _lh_null_free_shift) & _lh_null_free_mask);
456   }
457   static jint layout_helper_set_null_free(jint lh) {
458     lh |= (_lh_null_free_mask << _lh_null_free_shift);
459     assert(layout_helper_is_null_free(lh), "Bad encoding");
460     return lh;
461   }
462   static int layout_helper_header_size(jint lh) {
463     assert(lh < (jint)_lh_neutral_value, "must be array");
464     int hsize = (lh >> _lh_header_size_shift) & _lh_header_size_mask;
465     assert(hsize > 0 && hsize < (int)sizeof(oopDesc)*3, "sanity");
466     return hsize;
467   }
468   static BasicType layout_helper_element_type(jint lh) {
469     assert(lh < (jint)_lh_neutral_value, "must be array");
470     int btvalue = (lh >> _lh_element_type_shift) & _lh_element_type_mask;
471     assert((btvalue >= T_BOOLEAN && btvalue <= T_OBJECT) || btvalue == T_PRIMITIVE_OBJECT, "sanity");
472     return (BasicType) btvalue;
473   }
474 
475   // Want a pattern to quickly diff against layout header in register
476   // find something less clever!
477   static int layout_helper_boolean_diffbit() {
478     jint zlh = array_layout_helper(T_BOOLEAN);
479     jint blh = array_layout_helper(T_BYTE);
480     assert(zlh != blh, "array layout helpers must differ");
481     int diffbit = 1;
482     while ((diffbit & (zlh ^ blh)) == 0 && (diffbit & zlh) == 0) {
483       diffbit <<= 1;
484       assert(diffbit != 0, "make sure T_BOOLEAN has a different bit than T_BYTE");
485     }
486     return diffbit;
487   }
488 
489   static int layout_helper_log2_element_size(jint lh) {
490     assert(lh < (jint)_lh_neutral_value, "must be array");
491     int l2esz = (lh >> _lh_log2_element_size_shift) & _lh_log2_element_size_mask;
492     assert(layout_helper_element_type(lh) == T_PRIMITIVE_OBJECT || l2esz <= LogBytesPerLong,
493            "sanity. l2esz: 0x%x for lh: 0x%x", (uint)l2esz, (uint)lh);
494     return l2esz;
495   }
496   static jint array_layout_helper(jint tag, bool null_free, int hsize, BasicType etype, int log2_esize) {
497     return (tag        << _lh_array_tag_shift)
498       |    ((null_free ? 1 : 0) <<  _lh_null_free_shift)
499       |    (hsize      << _lh_header_size_shift)
500       |    ((int)etype << _lh_element_type_shift)
501       |    (log2_esize << _lh_log2_element_size_shift);
502   }
503   static jint instance_layout_helper(jint size, bool slow_path_flag) {
504     return (size << LogBytesPerWord)
505       |    (slow_path_flag ? _lh_instance_slow_path_bit : 0);
506   }
507   static int layout_helper_to_size_helper(jint lh) {
508     assert(lh > (jint)_lh_neutral_value, "must be instance");
509     // Note that the following expression discards _lh_instance_slow_path_bit.
510     return lh >> LogBytesPerWord;
511   }
512   // Out-of-line version computes everything based on the etype:
513   static jint array_layout_helper(BasicType etype);
514 
515   // What is the maximum number of primary superclasses any klass can have?
516   static juint primary_super_limit()         { return _primary_super_limit; }
517 
518   // vtables
519   klassVtable vtable() const;
520   int vtable_length() const { return _vtable_len; }
521 
522   // subclass check
523   bool is_subclass_of(const Klass* k) const;
524   // subtype check: true if is_subclass_of, or if k is interface and receiver implements it
525   bool is_subtype_of(Klass* k) const {
526     juint    off = k->super_check_offset();
527     Klass* sup = *(Klass**)( (address)this + off );
528     const juint secondary_offset = in_bytes(secondary_super_cache_offset());
529     if (sup == k) {
530       return true;
531     } else if (off != secondary_offset) {
532       return false;
533     } else {
534       return search_secondary_supers(k);
535     }
536   }
537 
538   bool search_secondary_supers(Klass* k) const;
539 
540   // Find LCA in class hierarchy
541   Klass *LCA( Klass *k );
542 
543   // Check whether reflection/jni/jvm code is allowed to instantiate this class;
544   // if not, throw either an Error or an Exception.
545   virtual void check_valid_for_instantiation(bool throwError, TRAPS);
546 
547   // array copying
548   virtual void  copy_array(arrayOop s, int src_pos, arrayOop d, int dst_pos, int length, TRAPS);
549 
550   // tells if the class should be initialized
551   virtual bool should_be_initialized() const    { return false; }
552   // initializes the klass
553   virtual void initialize(TRAPS);
554   virtual Klass* find_field(Symbol* name, Symbol* signature, fieldDescriptor* fd) const;
555   virtual Method* uncached_lookup_method(const Symbol* name, const Symbol* signature,
556                                          OverpassLookupMode overpass_mode,
557                                          PrivateLookupMode = PrivateLookupMode::find) const;
558  public:
559   Method* lookup_method(const Symbol* name, const Symbol* signature) const {
560     return uncached_lookup_method(name, signature, OverpassLookupMode::find);
561   }
562 
563   // array class with specific rank
564   virtual Klass* array_klass(int rank, TRAPS) = 0;
565 
566   // array class with this klass as element type
567   virtual Klass* array_klass(TRAPS) = 0;
568 
569   // These will return null instead of allocating on the heap:
570   virtual Klass* array_klass_or_null(int rank) = 0;
571   virtual Klass* array_klass_or_null() = 0;
572 
573   virtual oop protection_domain() const = 0;
574 
575   oop class_loader() const;
576 
577   inline oop klass_holder() const;
578 
579  protected:
580 
581   // Error handling when length > max_length or length < 0
582   static void check_array_allocation_length(int length, int max_length, TRAPS);
583 
584   void set_vtable_length(int len) { _vtable_len= len; }
585 
586   vtableEntry* start_of_vtable() const;
587 #if INCLUDE_CDS
588   void restore_unshareable_info(ClassLoaderData* loader_data, Handle protection_domain, TRAPS);
589 #endif
590  public:
591   Method* method_at_vtable(int index);
592 
593   static ByteSize vtable_start_offset();
594   static ByteSize vtable_length_offset() {
595     return byte_offset_of(Klass, _vtable_len);
596   }
597 
598 #if INCLUDE_CDS
599   // CDS support - remove and restore oops from metadata. Oops are not shared.
600   virtual void remove_unshareable_info();
601   virtual void remove_java_mirror();
602 
603   bool is_unshareable_info_restored() const {
604     assert(is_shared(), "use this for shared classes only");
605     if (has_archived_mirror_index()) {
606       // _java_mirror is not a valid OopHandle but rather an encoded reference in the shared heap
607       return false;
608     } else if (_java_mirror.ptr_raw() == nullptr) {
609       return false;
610     } else {
611       return true;
612     }
613   }
614 #endif // INCLUDE_CDS
615 
616  public:
617   // ALL FUNCTIONS BELOW THIS POINT ARE DISPATCHED FROM AN OOP
618   // These functions describe behavior for the oop not the KLASS.
619 
620   // actual oop size of obj in memory in word size.
621   virtual size_t oop_size(oop obj) const = 0;
622 
623   // Size of klass in word size.
624   virtual int size() const = 0;
625 
626   // Returns the Java name for a class (Resource allocated)
627   // For arrays, this returns the name of the element with a leading '['.
628   // For classes, this returns the name with the package separators
629   //     turned into '.'s.
630   const char* external_name() const;
631   // Returns the name for a class (Resource allocated) as the class
632   // would appear in a signature.
633   // For arrays, this returns the name of the element with a leading '['.
634   // For classes, this returns the name with a leading 'L' and a trailing ';'
635   //     and the package separators as '/'.
636   virtual const char* signature_name() const;
637 
638   const char* joint_in_module_of_loader(const Klass* class2, bool include_parent_loader = false) const;
639   const char* class_in_module_of_loader(bool use_are = false, bool include_parent_loader = false) const;
640 
641   // Returns "interface", "abstract class" or "class".
642   const char* external_kind() const;
643 
644   // type testing operations
645 #ifdef ASSERT
646  protected:
647   virtual bool is_instance_klass_slow()     const { return false; }
648   virtual bool is_array_klass_slow()        const { return false; }
649   virtual bool is_objArray_klass_slow()     const { return false; }
650   virtual bool is_typeArray_klass_slow()    const { return false; }
651   virtual bool is_flatArray_klass_slow()    const { return false; }
652 #endif // ASSERT
653   // current implementation uses this method even in non debug builds
654   virtual bool is_inline_klass_slow()       const { return false; }
655  public:
656 
657   // Fast non-virtual versions
658   #ifndef ASSERT
659   #define assert_same_query(xval, xcheck) xval
660   #else
661  private:
662   static bool assert_same_query(bool xval, bool xslow) {
663     assert(xval == xslow, "slow and fast queries agree");
664     return xval;
665   }
666  public:
667   #endif
668 
669   bool is_instance_klass()              const { return assert_same_query(_kind <= InstanceStackChunkKlassKind, is_instance_klass_slow()); }
670   bool is_inline_klass()                const { return is_inline_klass_slow(); } //temporary hack
671   // Other is anything that is not one of the more specialized kinds of InstanceKlass.
672   bool is_other_instance_klass()        const { return _kind <= InlineKlassKind; }
673   bool is_reference_instance_klass()    const { return _kind == InstanceRefKlassKind; }
674   bool is_mirror_instance_klass()       const { return _kind == InstanceMirrorKlassKind; }
675   bool is_class_loader_instance_klass() const { return _kind == InstanceClassLoaderKlassKind; }
676   bool is_array_klass()                 const { return assert_same_query( _kind >= TypeArrayKlassKind, is_array_klass_slow()); }
677   bool is_stack_chunk_instance_klass()  const { return _kind == InstanceStackChunkKlassKind; }
678   bool is_flatArray_klass()             const { return assert_same_query( _kind == FlatArrayKlassKind, is_flatArray_klass_slow()); }
679   bool is_objArray_klass()              const { return assert_same_query( _kind == ObjArrayKlassKind,  is_objArray_klass_slow()); }
680   bool is_typeArray_klass()             const { return assert_same_query( _kind == TypeArrayKlassKind, is_typeArray_klass_slow()); }
681   #undef assert_same_query
682 
683   inline bool is_null_free_array_klass()      const { return layout_helper_is_null_free(layout_helper()); }
684 
685   // Access flags
686   AccessFlags access_flags() const         { return _access_flags;  }
687   void set_access_flags(AccessFlags flags) { _access_flags = flags; }
688 
689   bool is_public() const                { return _access_flags.is_public(); }
690   bool is_final() const                 { return _access_flags.is_final(); }
691   bool is_interface() const             { return _access_flags.is_interface(); }
692   bool is_abstract() const              { return _access_flags.is_abstract(); }
693   bool is_synthetic() const             { return _access_flags.is_synthetic(); }
694   bool is_value_class() const           { return _access_flags.is_value_class(); }
695   bool is_identity_class() const        { return _access_flags.is_identity_class(); }
696   void set_is_synthetic()               { _access_flags.set_is_synthetic(); }
697   bool has_finalizer() const            { return _access_flags.has_finalizer(); }
698   void set_has_finalizer()              { _access_flags.set_has_finalizer(); }
699   bool is_hidden() const                { return access_flags().is_hidden_class(); }
700   void set_is_hidden()                  { _access_flags.set_is_hidden_class(); }
701   bool is_value_based()                 { return _access_flags.is_value_based_class(); }
702   void set_is_value_based()             { _access_flags.set_is_value_based_class(); }
703 
704   inline bool is_non_strong_hidden() const;
705 
706   bool is_cloneable() const;
707   void set_is_cloneable();
708 
709   // inline types and inline type array patterns
710   markWord prototype_header() const {
711     return _prototype_header;
712   }
713   static inline markWord default_prototype_header(Klass* k) {
714     return (k == nullptr) ? markWord::prototype() : k->prototype_header();
715   }
716 
717   inline void set_prototype_header(markWord header);
718   static ByteSize prototype_header_offset() { return in_ByteSize(offset_of(Klass, _prototype_header)); }
719 
720   JFR_ONLY(DEFINE_TRACE_ID_METHODS;)
721 
722   virtual void metaspace_pointers_do(MetaspaceClosure* iter);
723   virtual MetaspaceObj::Type type() const { return ClassType; }
724 
725   inline bool is_loader_alive() const;
726 
727   void clean_subklass();
728 
729   static void clean_weak_klass_links(bool unloading_occurred, bool clean_alive_klasses = true);
730   static void clean_subklass_tree() {
731     clean_weak_klass_links(/*unloading_occurred*/ true , /* clean_alive_klasses */ false);
732   }
733 
734   // Return self, except for abstract classes with exactly 1
735   // implementor.  Then return the 1 concrete implementation.
736   Klass *up_cast_abstract();
737 
738   // klass name
739   Symbol* name() const                   { return _name; }
740   void set_name(Symbol* n);
741 
742   virtual void release_C_heap_structures(bool release_constant_pool = true);
743 
744  public:
745   virtual jint compute_modifier_flags() const = 0;
746 
747   // JVMTI support
748   virtual jint jvmti_class_status() const;
749 
750   // Printing
751   virtual void print_on(outputStream* st) const;
752 
753   virtual void oop_print_value_on(oop obj, outputStream* st);
754   virtual void oop_print_on      (oop obj, outputStream* st);
755 
756   virtual const char* internal_name() const = 0;
757 
758   // Verification
759   virtual void verify_on(outputStream* st);
760   void verify() { verify_on(tty); }
761 
762 #ifndef PRODUCT
763   bool verify_vtable_index(int index);
764 #endif
765 
766   virtual void oop_verify_on(oop obj, outputStream* st);
767 
768   // for error reporting
769   static bool is_valid(Klass* k);
770 };
771 
772 #endif // SHARE_OOPS_KLASS_HPP