1 /*
  2  * Copyright (c) 1997, 2024, 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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 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     InstanceRefKlassKind,
 74     InstanceMirrorKlassKind,
 75     InstanceClassLoaderKlassKind,
 76     InstanceStackChunkKlassKind,
 77     TypeArrayKlassKind,
 78     ObjArrayKlassKind,
 79     UnknownKlassKind
 80   };
 81 
 82   static const uint KLASS_KIND_COUNT = ObjArrayKlassKind + 1;
 83  protected:
 84 
 85   // If you add a new field that points to any metaspace object, you
 86   // must add this field to Klass::metaspace_pointers_do().
 87 
 88   // note: put frequently-used fields together at start of klass structure
 89   // for better cache behavior (may not make much of a difference but sure won't hurt)
 90   enum { _primary_super_limit = 8 };
 91 
 92   // The "layout helper" is a combined descriptor of object layout.
 93   // For klasses which are neither instance nor array, the value is zero.
 94   //
 95   // For instances, layout helper is a positive number, the instance size.
 96   // This size is already passed through align_object_size and scaled to bytes.
 97   // The low order bit is set if instances of this class cannot be
 98   // allocated using the fastpath.
 99   //
100   // For arrays, layout helper is a negative number, containing four
101   // distinct bytes, as follows:
102   //    MSB:[tag, hsz, ebt, log2(esz)]:LSB
103   // where:
104   //    tag is 0x80 if the elements are oops, 0xC0 if non-oops
105   //    hsz is array header size in bytes (i.e., offset of first element)
106   //    ebt is the BasicType of the elements
107   //    esz is the element size in bytes
108   // This packed word is arranged so as to be quickly unpacked by the
109   // various fast paths that use the various subfields.
110   //
111   // The esz bits can be used directly by a SLL instruction, without masking.
112   //
113   // Note that the array-kind tag looks like 0x00 for instance klasses,
114   // since their length in bytes is always less than 24Mb.
115   //
116   // Final note:  This comes first, immediately after C++ vtable,
117   // because it is frequently queried.
118   jint        _layout_helper;
119 
120   // Klass kind used to resolve the runtime type of the instance.
121   //  - Used to implement devirtualized oop closure dispatching.
122   //  - Various type checking in the JVM
123   const KlassKind _kind;
124 
125   // Processed access flags, for use by Class.getModifiers.
126   jint        _modifier_flags;
127 
128   // The fields _super_check_offset, _secondary_super_cache, _secondary_supers
129   // and _primary_supers all help make fast subtype checks.  See big discussion
130   // in doc/server_compiler/checktype.txt
131   //
132   // Where to look to observe a supertype (it is &_secondary_super_cache for
133   // secondary supers, else is &_primary_supers[depth()].
134   juint       _super_check_offset;
135 
136   // Class name.  Instance classes: java/lang/String, etc.  Array classes: [I,
137   // [Ljava/lang/String;, etc.  Set to zero for all other kinds of classes.
138   Symbol*     _name;
139 
140   // Cache of last observed secondary supertype
141   Klass*      _secondary_super_cache;
142   // Array of all secondary supertypes
143   Array<Klass*>* _secondary_supers;
144   // Ordered list of all primary supertypes
145   Klass*      _primary_supers[_primary_super_limit];
146   // java/lang/Class instance mirroring this class
147   OopHandle   _java_mirror;
148   // Superclass
149   Klass*      _super;
150   // First subclass (null if none); _subklass->next_sibling() is next one
151   Klass* volatile _subklass;
152   // Sibling link (or null); links all subklasses of a klass
153   Klass* volatile _next_sibling;
154 
155   // All klasses loaded by a class loader are chained through these links
156   Klass*      _next_link;
157 
158   // The VM's representation of the ClassLoader used to load this class.
159   // Provide access the corresponding instance java.lang.ClassLoader.
160   ClassLoaderData* _class_loader_data;
161 
162   // Bitmap and hash code used by hashed secondary supers.
163   uintx    _bitmap;
164   uint8_t  _hash_slot;
165 
166   static uint8_t compute_hash_slot(Symbol* s);
167 
168   int _vtable_len;              // vtable length. This field may be read very often when we
169                                 // have lots of itable dispatches (e.g., lambdas and streams).
170                                 // Keep it away from the beginning of a Klass to avoid cacheline
171                                 // contention that may happen when a nearby object is modified.
172   AccessFlags _access_flags;    // Access flags. The class/interface distinction is stored here.
173 
174   JFR_ONLY(DEFINE_TRACE_ID_FIELD;)
175 
176 private:
177   // This is an index into FileMapHeader::_shared_path_table[], to
178   // associate this class with the JAR file where it's loaded from during
179   // dump time. If a class is not loaded from the shared archive, this field is
180   // -1.
181   s2 _shared_class_path_index;
182 
183 #if INCLUDE_CDS
184   // Various attributes for shared classes. Should be zero for a non-shared class.
185   u2     _shared_class_flags;
186   enum CDSSharedClassFlags {
187     _is_shared_class                       = 1 << 0,  // shadows MetaspaceObj::is_shared
188     _archived_lambda_proxy_is_available    = 1 << 1,
189     _has_value_based_class_annotation      = 1 << 2,
190     _verified_at_dump_time                 = 1 << 3,
191     _has_archived_enum_objs                = 1 << 4,
192     // This class was not loaded from a classfile in the module image
193     // or classpath.
194     _is_generated_shared_class             = 1 << 5,
195     // The archived mirror is already initialized. No need to call <clinit>
196     _has_preinitialized_mirror             = 1 << 6,
197   };
198 #endif
199 
200   CDS_JAVA_HEAP_ONLY(int _archived_mirror_index;)
201 
202 protected:
203 
204   Klass(KlassKind kind);
205   Klass();
206 
207   void* operator new(size_t size, ClassLoaderData* loader_data, size_t word_size, TRAPS) throw();
208 
209  public:
210   int kind() { return _kind; }
211 
212   enum class DefaultsLookupMode { find, skip };
213   enum class OverpassLookupMode { find, skip };
214   enum class StaticLookupMode   { find, skip };
215   enum class PrivateLookupMode  { find, skip };
216 
217   virtual bool is_klass() const { return true; }
218 
219   // super() cannot be InstanceKlass* -- Java arrays are covariant, and _super is used
220   // to implement that. NB: the _super of "[Ljava/lang/Integer;" is "[Ljava/lang/Number;"
221   // If this is not what your code expects, you're probably looking for Klass::java_super().
222   Klass* super() const               { return _super; }
223   void set_super(Klass* k)           { _super = k; }
224 
225   // initializes _super link, _primary_supers & _secondary_supers arrays
226   void initialize_supers(Klass* k, Array<InstanceKlass*>* transitive_interfaces, TRAPS);
227 
228   // klass-specific helper for initializing _secondary_supers
229   virtual GrowableArray<Klass*>* compute_secondary_supers(int num_extra_slots,
230                                                           Array<InstanceKlass*>* transitive_interfaces);
231 
232   // java_super is the Java-level super type as specified by Class.getSuperClass.
233   virtual InstanceKlass* java_super() const  { return nullptr; }
234 
235   juint    super_check_offset() const  { return _super_check_offset; }
236   void set_super_check_offset(juint o) { _super_check_offset = o; }
237 
238   Klass* secondary_super_cache() const     { return _secondary_super_cache; }
239   void set_secondary_super_cache(Klass* k) { _secondary_super_cache = k; }
240 
241   Array<Klass*>* secondary_supers() const { return _secondary_supers; }
242   void set_secondary_supers(Array<Klass*>* k);
243   void set_secondary_supers(Array<Klass*>* k, uintx bitmap);
244 
245   uint8_t hash_slot() const { return _hash_slot; }
246 
247   // Return the element of the _super chain of the given depth.
248   // If there is no such element, return either null or this.
249   Klass* primary_super_of_depth(juint i) const {
250     assert(i < primary_super_limit(), "oob");
251     Klass* super = _primary_supers[i];
252     assert(super == nullptr || super->super_depth() == i, "correct display");
253     return super;
254   }
255 
256   // Can this klass be a primary super?  False for interfaces and arrays of
257   // interfaces.  False also for arrays or classes with long super chains.
258   bool can_be_primary_super() const {
259     const juint secondary_offset = in_bytes(secondary_super_cache_offset());
260     return super_check_offset() != secondary_offset;
261   }
262   virtual bool can_be_primary_super_slow() const;
263 
264   // Returns number of primary supers; may be a number in the inclusive range [0, primary_super_limit].
265   juint super_depth() const {
266     if (!can_be_primary_super()) {
267       return primary_super_limit();
268     } else {
269       juint d = (super_check_offset() - in_bytes(primary_supers_offset())) / sizeof(Klass*);
270       assert(d < primary_super_limit(), "oob");
271       assert(_primary_supers[d] == this, "proper init");
272       return d;
273     }
274   }
275 
276   // java mirror
277   oop java_mirror() const;
278   oop java_mirror_no_keepalive() const;
279   void set_java_mirror(Handle m);
280 
281   oop archived_java_mirror() NOT_CDS_JAVA_HEAP_RETURN_(nullptr);
282   void set_archived_java_mirror(int mirror_index) NOT_CDS_JAVA_HEAP_RETURN;
283 
284   // Temporary mirror switch used by RedefineClasses
285   OopHandle java_mirror_handle() const { return _java_mirror; }
286   void swap_java_mirror_handle(OopHandle& mirror) { _java_mirror.swap(mirror); }
287 
288   // Set java mirror OopHandle to null for CDS
289   // This leaves the OopHandle in the CLD, but that's ok, you can't release them.
290   void clear_java_mirror_handle() { _java_mirror = OopHandle(); }
291 
292   // modifier flags
293   jint modifier_flags() const          { return _modifier_flags; }
294   void set_modifier_flags(jint flags)  { _modifier_flags = flags; }
295 
296   // size helper
297   int layout_helper() const            { return _layout_helper; }
298   void set_layout_helper(int lh)       { _layout_helper = lh; }
299 
300   // Note: for instances layout_helper() may include padding.
301   // Use InstanceKlass::contains_field_offset to classify field offsets.
302 
303   // sub/superklass links
304   Klass* subklass(bool log = false) const;
305   Klass* next_sibling(bool log = false) const;
306 
307   InstanceKlass* superklass() const;
308   void append_to_sibling_list();           // add newly created receiver to superklass' subklass list
309 
310   void set_next_link(Klass* k) { _next_link = k; }
311   Klass* next_link() const { return _next_link; }   // The next klass defined by the class loader.
312   Klass** next_link_addr() { return &_next_link; }
313 
314   // class loader data
315   ClassLoaderData* class_loader_data() const               { return _class_loader_data; }
316   void set_class_loader_data(ClassLoaderData* loader_data) {  _class_loader_data = loader_data; }
317 
318   s2 shared_classpath_index() const   {
319     return _shared_class_path_index;
320   };
321 
322   void set_shared_classpath_index(s2 index) {
323     _shared_class_path_index = index;
324   };
325 
326   bool has_archived_mirror_index() const {
327     CDS_JAVA_HEAP_ONLY(return _archived_mirror_index >= 0;)
328     NOT_CDS_JAVA_HEAP(return false);
329   }
330 
331   void clear_archived_mirror_index() NOT_CDS_JAVA_HEAP_RETURN;
332 
333   void set_lambda_proxy_is_available() {
334     CDS_ONLY(_shared_class_flags |= _archived_lambda_proxy_is_available;)
335   }
336   void clear_lambda_proxy_is_available() {
337     CDS_ONLY(_shared_class_flags &= (u2)(~_archived_lambda_proxy_is_available);)
338   }
339   bool lambda_proxy_is_available() const {
340     CDS_ONLY(return (_shared_class_flags & _archived_lambda_proxy_is_available) != 0;)
341     NOT_CDS(return false;)
342   }
343 
344   void set_has_value_based_class_annotation() {
345     CDS_ONLY(_shared_class_flags |= _has_value_based_class_annotation;)
346   }
347   void clear_has_value_based_class_annotation() {
348     CDS_ONLY(_shared_class_flags &= (u2)(~_has_value_based_class_annotation);)
349   }
350   bool has_value_based_class_annotation() const {
351     CDS_ONLY(return (_shared_class_flags & _has_value_based_class_annotation) != 0;)
352     NOT_CDS(return false;)
353   }
354 
355   void set_verified_at_dump_time() {
356     CDS_ONLY(_shared_class_flags |= _verified_at_dump_time;)
357   }
358   bool verified_at_dump_time() const {
359     CDS_ONLY(return (_shared_class_flags & _verified_at_dump_time) != 0;)
360     NOT_CDS(return false;)
361   }
362 
363   void set_has_archived_enum_objs() {
364     CDS_ONLY(_shared_class_flags |= _has_archived_enum_objs;)
365   }
366   bool has_archived_enum_objs() const {
367     CDS_ONLY(return (_shared_class_flags & _has_archived_enum_objs) != 0;)
368     NOT_CDS(return false;)
369   }
370 
371   void set_is_generated_shared_class() {
372     CDS_ONLY(_shared_class_flags |= _is_generated_shared_class;)
373   }
374   bool is_generated_shared_class() const {
375     CDS_ONLY(return (_shared_class_flags & _is_generated_shared_class) != 0;)
376     NOT_CDS(return false;)
377   }
378 
379   void set_has_preinitialized_mirror() {
380     CDS_ONLY(_shared_class_flags |= _has_preinitialized_mirror;)
381   }
382   bool has_preinitialized_mirror() const {
383     CDS_ONLY(return (_shared_class_flags & _has_preinitialized_mirror) != 0;)
384     NOT_CDS(return false;)
385   }
386 
387   bool is_shared() const                { // shadows MetaspaceObj::is_shared)()
388     CDS_ONLY(return (_shared_class_flags & _is_shared_class) != 0;)
389     NOT_CDS(return false;)
390   }
391 
392   void set_is_shared() {
393     CDS_ONLY(_shared_class_flags |= _is_shared_class;)
394   }
395 
396   // Obtain the module or package for this class
397   virtual ModuleEntry* module() const = 0;
398   virtual PackageEntry* package() const = 0;
399 
400  protected:                                // internal accessors
401   void     set_subklass(Klass* s);
402   void     set_next_sibling(Klass* s);
403 
404  private:
405   static void  hash_insert(Klass* klass, GrowableArray<Klass*>* secondaries, uintx& bitmap);
406   static uintx hash_secondary_supers(Array<Klass*>* secondaries, bool rewrite);
407 
408  public:
409   // Secondary supers table support
410   static Array<Klass*>* pack_secondary_supers(ClassLoaderData* loader_data,
411                                               GrowableArray<Klass*>* primaries,
412                                               GrowableArray<Klass*>* secondaries,
413                                               uintx& bitmap,
414                                               TRAPS);
415 
416   static uintx   compute_secondary_supers_bitmap(Array<Klass*>* secondary_supers);
417   static uint8_t compute_home_slot(Klass* k, uintx bitmap);
418 
419   static constexpr int SECONDARY_SUPERS_TABLE_SIZE = sizeof(_bitmap) * 8;
420   static constexpr int SECONDARY_SUPERS_TABLE_MASK = SECONDARY_SUPERS_TABLE_SIZE - 1;
421 
422   static constexpr uintx SECONDARY_SUPERS_BITMAP_EMPTY    = 0;
423   static constexpr uintx SECONDARY_SUPERS_BITMAP_FULL     = ~(uintx)0;
424 
425   // Compiler support
426   static ByteSize super_offset()                 { return byte_offset_of(Klass, _super); }
427   static ByteSize super_check_offset_offset()    { return byte_offset_of(Klass, _super_check_offset); }
428   static ByteSize primary_supers_offset()        { return byte_offset_of(Klass, _primary_supers); }
429   static ByteSize secondary_super_cache_offset() { return byte_offset_of(Klass, _secondary_super_cache); }
430   static ByteSize secondary_supers_offset()      { return byte_offset_of(Klass, _secondary_supers); }
431   static ByteSize java_mirror_offset()           { return byte_offset_of(Klass, _java_mirror); }
432   static ByteSize class_loader_data_offset()     { return byte_offset_of(Klass, _class_loader_data); }
433   static ByteSize modifier_flags_offset()        { return byte_offset_of(Klass, _modifier_flags); }
434   static ByteSize layout_helper_offset()         { return byte_offset_of(Klass, _layout_helper); }
435   static ByteSize access_flags_offset()          { return byte_offset_of(Klass, _access_flags); }
436 #if INCLUDE_JVMCI
437   static ByteSize subklass_offset()              { return byte_offset_of(Klass, _subklass); }
438   static ByteSize next_sibling_offset()          { return byte_offset_of(Klass, _next_sibling); }
439 #endif
440   static ByteSize bitmap_offset()                { return byte_offset_of(Klass, _bitmap); }
441 
442   // Unpacking layout_helper:
443   static const int _lh_neutral_value           = 0;  // neutral non-array non-instance value
444   static const int _lh_instance_slow_path_bit  = 0x01;
445   static const int _lh_log2_element_size_shift = BitsPerByte*0;
446   static const int _lh_log2_element_size_mask  = BitsPerLong-1;
447   static const int _lh_element_type_shift      = BitsPerByte*1;
448   static const int _lh_element_type_mask       = right_n_bits(BitsPerByte);  // shifted mask
449   static const int _lh_header_size_shift       = BitsPerByte*2;
450   static const int _lh_header_size_mask        = right_n_bits(BitsPerByte);  // shifted mask
451   static const int _lh_array_tag_bits          = 2;
452   static const int _lh_array_tag_shift         = BitsPerInt - _lh_array_tag_bits;
453   static const int _lh_array_tag_obj_value     = ~0x01;   // 0x80000000 >> 30
454 
455   static const unsigned int _lh_array_tag_type_value = 0Xffffffff; // ~0x00,  // 0xC0000000 >> 30
456 
457   static int layout_helper_size_in_bytes(jint lh) {
458     assert(lh > (jint)_lh_neutral_value, "must be instance");
459     return (int) lh & ~_lh_instance_slow_path_bit;
460   }
461   static bool layout_helper_needs_slow_path(jint lh) {
462     assert(lh > (jint)_lh_neutral_value, "must be instance");
463     return (lh & _lh_instance_slow_path_bit) != 0;
464   }
465   static bool layout_helper_is_instance(jint lh) {
466     return (jint)lh > (jint)_lh_neutral_value;
467   }
468   static bool layout_helper_is_array(jint lh) {
469     return (jint)lh < (jint)_lh_neutral_value;
470   }
471   static bool layout_helper_is_typeArray(jint lh) {
472     // _lh_array_tag_type_value == (lh >> _lh_array_tag_shift);
473     return (juint)lh >= (juint)(_lh_array_tag_type_value << _lh_array_tag_shift);
474   }
475   static bool layout_helper_is_objArray(jint lh) {
476     // _lh_array_tag_obj_value == (lh >> _lh_array_tag_shift);
477     return (jint)lh < (jint)(_lh_array_tag_type_value << _lh_array_tag_shift);
478   }
479   static int layout_helper_header_size(jint lh) {
480     assert(lh < (jint)_lh_neutral_value, "must be array");
481     int hsize = (lh >> _lh_header_size_shift) & _lh_header_size_mask;
482     assert(hsize > 0 && hsize < (int)sizeof(oopDesc)*3, "sanity");
483     return hsize;
484   }
485   static BasicType layout_helper_element_type(jint lh) {
486     assert(lh < (jint)_lh_neutral_value, "must be array");
487     int btvalue = (lh >> _lh_element_type_shift) & _lh_element_type_mask;
488     assert(btvalue >= T_BOOLEAN && btvalue <= T_OBJECT, "sanity");
489     return (BasicType) btvalue;
490   }
491 
492   // Want a pattern to quickly diff against layout header in register
493   // find something less clever!
494   static int layout_helper_boolean_diffbit() {
495     jint zlh = array_layout_helper(T_BOOLEAN);
496     jint blh = array_layout_helper(T_BYTE);
497     assert(zlh != blh, "array layout helpers must differ");
498     int diffbit = 1;
499     while ((diffbit & (zlh ^ blh)) == 0 && (diffbit & zlh) == 0) {
500       diffbit <<= 1;
501       assert(diffbit != 0, "make sure T_BOOLEAN has a different bit than T_BYTE");
502     }
503     return diffbit;
504   }
505 
506   static int layout_helper_log2_element_size(jint lh) {
507     assert(lh < (jint)_lh_neutral_value, "must be array");
508     int l2esz = (lh >> _lh_log2_element_size_shift) & _lh_log2_element_size_mask;
509     assert(l2esz <= LogBytesPerLong,
510            "sanity. l2esz: 0x%x for lh: 0x%x", (uint)l2esz, (uint)lh);
511     return l2esz;
512   }
513   static jint array_layout_helper(jint tag, int hsize, BasicType etype, int log2_esize) {
514     return (tag        << _lh_array_tag_shift)
515       |    (hsize      << _lh_header_size_shift)
516       |    ((int)etype << _lh_element_type_shift)
517       |    (log2_esize << _lh_log2_element_size_shift);
518   }
519   static jint instance_layout_helper(jint size, bool slow_path_flag) {
520     return (size << LogBytesPerWord)
521       |    (slow_path_flag ? _lh_instance_slow_path_bit : 0);
522   }
523   static int layout_helper_to_size_helper(jint lh) {
524     assert(lh > (jint)_lh_neutral_value, "must be instance");
525     // Note that the following expression discards _lh_instance_slow_path_bit.
526     return lh >> LogBytesPerWord;
527   }
528   // Out-of-line version computes everything based on the etype:
529   static jint array_layout_helper(BasicType etype);
530 
531   // What is the maximum number of primary superclasses any klass can have?
532   static juint primary_super_limit()         { return _primary_super_limit; }
533 
534   // vtables
535   klassVtable vtable() const;
536   int vtable_length() const { return _vtable_len; }
537 
538   // subclass check
539   bool is_subclass_of(const Klass* k) const;
540   // subtype check: true if is_subclass_of, or if k is interface and receiver implements it
541   bool is_subtype_of(Klass* k) const {
542     juint    off = k->super_check_offset();
543     Klass* sup = *(Klass**)( (address)this + off );
544     const juint secondary_offset = in_bytes(secondary_super_cache_offset());
545     if (sup == k) {
546       return true;
547     } else if (off != secondary_offset) {
548       return false;
549     } else {
550       return search_secondary_supers(k);
551     }
552   }
553 
554   bool search_secondary_supers(Klass* k) const;
555 
556   // Find LCA in class hierarchy
557   Klass *LCA( Klass *k );
558 
559   // Check whether reflection/jni/jvm code is allowed to instantiate this class;
560   // if not, throw either an Error or an Exception.
561   virtual void check_valid_for_instantiation(bool throwError, TRAPS);
562 
563   // array copying
564   virtual void  copy_array(arrayOop s, int src_pos, arrayOop d, int dst_pos, int length, TRAPS);
565 
566   // tells if the class should be initialized
567   virtual bool should_be_initialized() const    { return false; }
568   // initializes the klass
569   virtual void initialize(TRAPS);
570   virtual Klass* find_field(Symbol* name, Symbol* signature, fieldDescriptor* fd) const;
571   virtual Method* uncached_lookup_method(const Symbol* name, const Symbol* signature,
572                                          OverpassLookupMode overpass_mode,
573                                          PrivateLookupMode = PrivateLookupMode::find) const;
574  public:
575   Method* lookup_method(const Symbol* name, const Symbol* signature) const {
576     return uncached_lookup_method(name, signature, OverpassLookupMode::find);
577   }
578 
579   // array class with specific rank
580   virtual ArrayKlass* array_klass(int rank, TRAPS) = 0;
581 
582   // array class with this klass as element type
583   virtual ArrayKlass* array_klass(TRAPS) = 0;
584 
585   // These will return null instead of allocating on the heap:
586   virtual ArrayKlass* array_klass_or_null(int rank) = 0;
587   virtual ArrayKlass* array_klass_or_null() = 0;
588 
589   virtual oop protection_domain() const = 0;
590 
591   oop class_loader() const;
592   Symbol* class_loader_name_and_id() const;
593 
594   inline oop klass_holder() const;
595 
596  protected:
597 
598   // Error handling when length > max_length or length < 0
599   static void check_array_allocation_length(int length, int max_length, TRAPS);
600 
601   void set_vtable_length(int len) { _vtable_len= len; }
602 
603   vtableEntry* start_of_vtable() const;
604 #if INCLUDE_CDS
605   void restore_unshareable_info(ClassLoaderData* loader_data, Handle protection_domain, TRAPS);
606 #endif
607  public:
608   Method* method_at_vtable(int index);
609 
610   static ByteSize vtable_start_offset();
611   static ByteSize vtable_length_offset() {
612     return byte_offset_of(Klass, _vtable_len);
613   }
614 
615 #if INCLUDE_CDS
616   // CDS support - remove and restore oops from metadata. Oops are not shared.
617   virtual void remove_unshareable_info();
618   virtual void remove_java_mirror();
619 
620   bool is_unshareable_info_restored() const {
621     assert(is_shared(), "use this for shared classes only");
622     if (has_archived_mirror_index()) {
623       // _java_mirror is not a valid OopHandle but rather an encoded reference in the shared heap
624       return false;
625     } else if (_java_mirror.is_empty()) {
626       return false;
627     } else {
628       return true;
629     }
630   }
631 #endif // INCLUDE_CDS
632 
633  public:
634   // ALL FUNCTIONS BELOW THIS POINT ARE DISPATCHED FROM AN OOP
635   // These functions describe behavior for the oop not the KLASS.
636 
637   // actual oop size of obj in memory in word size.
638   virtual size_t oop_size(oop obj) const = 0;
639 
640   // Size of klass in word size.
641   virtual int size() const = 0;
642 
643   // Returns the Java name for a class (Resource allocated)
644   // For arrays, this returns the name of the element with a leading '['.
645   // For classes, this returns the name with the package separators
646   //     turned into '.'s.
647   const char* external_name() const;
648   // Returns the name for a class (Resource allocated) as the class
649   // would appear in a signature.
650   // For arrays, this returns the name of the element with a leading '['.
651   // For classes, this returns the name with a leading 'L' and a trailing ';'
652   //     and the package separators as '/'.
653   virtual const char* signature_name() const;
654 
655   const char* joint_in_module_of_loader(const Klass* class2, bool include_parent_loader = false) const;
656   const char* class_in_module_of_loader(bool use_are = false, bool include_parent_loader = false) const;
657 
658   // Returns "interface", "abstract class" or "class".
659   const char* external_kind() const;
660 
661   // type testing operations
662 #ifdef ASSERT
663  protected:
664   virtual bool is_instance_klass_slow()     const { return false; }
665   virtual bool is_array_klass_slow()        const { return false; }
666   virtual bool is_objArray_klass_slow()     const { return false; }
667   virtual bool is_typeArray_klass_slow()    const { return false; }
668 #endif // ASSERT
669  public:
670 
671   // Fast non-virtual versions
672   #ifndef ASSERT
673   #define assert_same_query(xval, xcheck) xval
674   #else
675  private:
676   static bool assert_same_query(bool xval, bool xslow) {
677     assert(xval == xslow, "slow and fast queries agree");
678     return xval;
679   }
680  public:
681   #endif
682 
683   bool is_instance_klass()              const { return assert_same_query(_kind <= InstanceStackChunkKlassKind, is_instance_klass_slow()); }
684   // Other is anything that is not one of the more specialized kinds of InstanceKlass.
685   bool is_other_instance_klass()        const { return _kind == InstanceKlassKind; }
686   bool is_reference_instance_klass()    const { return _kind == InstanceRefKlassKind; }
687   bool is_mirror_instance_klass()       const { return _kind == InstanceMirrorKlassKind; }
688   bool is_class_loader_instance_klass() const { return _kind == InstanceClassLoaderKlassKind; }
689   bool is_array_klass()                 const { return assert_same_query( _kind >= TypeArrayKlassKind, is_array_klass_slow()); }
690   bool is_stack_chunk_instance_klass()  const { return _kind == InstanceStackChunkKlassKind; }
691   bool is_objArray_klass()              const { return assert_same_query( _kind == ObjArrayKlassKind,  is_objArray_klass_slow()); }
692   bool is_typeArray_klass()             const { return assert_same_query( _kind == TypeArrayKlassKind, is_typeArray_klass_slow()); }
693   #undef assert_same_query
694 
695   // Access flags
696   AccessFlags access_flags() const         { return _access_flags;  }
697   void set_access_flags(AccessFlags flags) { _access_flags = flags; }
698 
699   bool is_public() const                { return _access_flags.is_public(); }
700   bool is_final() const                 { return _access_flags.is_final(); }
701   bool is_interface() const             { return _access_flags.is_interface(); }
702   bool is_abstract() const              { return _access_flags.is_abstract(); }
703   bool is_super() const                 { return _access_flags.is_super(); }
704   bool is_synthetic() const             { return _access_flags.is_synthetic(); }
705   void set_is_synthetic()               { _access_flags.set_is_synthetic(); }
706   bool has_finalizer() const            { return _access_flags.has_finalizer(); }
707   void set_has_finalizer()              { _access_flags.set_has_finalizer(); }
708   bool is_hidden() const                { return access_flags().is_hidden_class(); }
709   void set_is_hidden()                  { _access_flags.set_is_hidden_class(); }
710   bool is_value_based()                 { return _access_flags.is_value_based_class(); }
711   void set_is_value_based()             { _access_flags.set_is_value_based_class(); }
712 
713   inline bool is_non_strong_hidden() const;
714 
715   bool is_cloneable() const;
716   void set_is_cloneable();
717 
718   JFR_ONLY(DEFINE_TRACE_ID_METHODS;)
719 
720   virtual void metaspace_pointers_do(MetaspaceClosure* iter);
721   virtual MetaspaceObj::Type type() const { return ClassType; }
722 
723   inline bool is_loader_alive() const;
724 
725   void clean_subklass();
726 
727   static void clean_weak_klass_links(bool unloading_occurred, bool clean_alive_klasses = true);
728   static void clean_subklass_tree() {
729     clean_weak_klass_links(/*unloading_occurred*/ true , /* clean_alive_klasses */ false);
730   }
731 
732   // Return self, except for abstract classes with exactly 1
733   // implementor.  Then return the 1 concrete implementation.
734   Klass *up_cast_abstract();
735 
736   // klass name
737   Symbol* name() const                   { return _name; }
738   void set_name(Symbol* n);
739 
740   virtual void release_C_heap_structures(bool release_constant_pool = true);
741 
742  public:
743   virtual jint compute_modifier_flags() const = 0;
744 
745   // JVMTI support
746   virtual jint jvmti_class_status() const;
747 
748   // Printing
749   virtual void print_on(outputStream* st) const;
750 
751   virtual void oop_print_value_on(oop obj, outputStream* st);
752   virtual void oop_print_on      (oop obj, outputStream* st);
753 
754   void print_secondary_supers_on(outputStream* st) const;
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   static void on_secondary_supers_verification_failure(Klass* super, Klass* sub, bool linear_result, bool table_result, const char* msg);
772 };
773 
774 #endif // SHARE_OOPS_KLASS_HPP
--- EOF ---