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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 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/klassFlags.hpp"
 31 #include "oops/markWord.hpp"
 32 #include "oops/metadata.hpp"
 33 #include "oops/oop.hpp"
 34 #include "oops/oopHandle.hpp"
 35 #include "utilities/accessFlags.hpp"
 36 #include "utilities/macros.hpp"
 37 #if INCLUDE_JFR
 38 #include "jfr/support/jfrTraceIdExtension.hpp"
 39 #endif
 40 
 41 //
 42 // A Klass provides:
 43 //  1: language level class object (method dictionary etc.)
 44 //  2: provide vm dispatch behavior for the object
 45 // Both functions are combined into one C++ class.
 46 
 47 // One reason for the oop/klass dichotomy in the implementation is
 48 // that we don't want a C++ vtbl pointer in every object.  Thus,
 49 // normal oops don't have any virtual functions.  Instead, they
 50 // forward all "virtual" functions to their klass, which does have
 51 // a vtbl and does the C++ dispatch depending on the object's
 52 // actual type.  (See oop.inline.hpp for some of the forwarding code.)
 53 // ALL FUNCTIONS IMPLEMENTING THIS DISPATCH ARE PREFIXED WITH "oop_"!
 54 
 55 // Forward declarations.
 56 template <class T> class Array;
 57 template <class T> class GrowableArray;
 58 class ClassLoaderData;
 59 class fieldDescriptor;
 60 class klassVtable;
 61 class ModuleEntry;
 62 class PackageEntry;
 63 class ParCompactionManager;
 64 class PSPromotionManager;
 65 class vtableEntry;
 66 
 67 class Klass : public Metadata {
 68   friend class VMStructs;
 69   friend class JVMCIVMStructs;
 70  public:
 71   // Klass Kinds for all subclasses of Klass
 72   enum KlassKind {
 73     InstanceKlassKind,
 74     InstanceRefKlassKind,
 75     InstanceMirrorKlassKind,
 76     InstanceClassLoaderKlassKind,
 77     InstanceStackChunkKlassKind,
 78     TypeArrayKlassKind,
 79     ObjArrayKlassKind,
 80     UnknownKlassKind
 81   };
 82 
 83   static const uint KLASS_KIND_COUNT = ObjArrayKlassKind + 1;
 84  protected:
 85 
 86   // If you add a new field that points to any metaspace object, you
 87   // must add this field to Klass::metaspace_pointers_do().
 88 
 89   // note: put frequently-used fields together at start of klass structure
 90   // for better cache behavior (may not make much of a difference but sure won't hurt)
 91   enum { _primary_super_limit = 8 };
 92 
 93   // The "layout helper" is a combined descriptor of object layout.
 94   // For klasses which are neither instance nor array, the value is zero.
 95   //
 96   // For instances, layout helper is a positive number, the instance size.
 97   // This size is already passed through align_object_size and scaled to bytes.
 98   // The low order bit is set if instances of this class cannot be
 99   // allocated using the fastpath.
100   //
101   // For arrays, layout helper is a negative number, containing four
102   // distinct bytes, as follows:
103   //    MSB:[tag, hsz, ebt, log2(esz)]:LSB
104   // where:
105   //    tag is 0x80 if the elements are oops, 0xC0 if non-oops
106   //    hsz is array header size in bytes (i.e., offset of first element)
107   //    ebt is the BasicType of the elements
108   //    esz is the element size in bytes
109   // This packed word is arranged so as to be quickly unpacked by the
110   // various fast paths that use the various subfields.
111   //
112   // The esz bits can be used directly by a SLL instruction, without masking.
113   //
114   // Note that the array-kind tag looks like 0x00 for instance klasses,
115   // since their length in bytes is always less than 24Mb.
116   //
117   // Final note:  This comes first, immediately after C++ vtable,
118   // because it is frequently queried.
119   jint        _layout_helper;
120 
121   // Klass kind used to resolve the runtime type of the instance.
122   //  - Used to implement devirtualized oop closure dispatching.
123   //  - Various type checking in the JVM
124   const KlassKind _kind;
125 
126   // Processed access flags, for use by Class.getModifiers.
127   jint        _modifier_flags;
128 
129   // The fields _super_check_offset, _secondary_super_cache, _secondary_supers
130   // and _primary_supers all help make fast subtype checks.  See big discussion
131   // in doc/server_compiler/checktype.txt
132   //
133   // Where to look to observe a supertype (it is &_secondary_super_cache for
134   // secondary supers, else is &_primary_supers[depth()].
135   juint       _super_check_offset;
136 
137   // Class name.  Instance classes: java/lang/String, etc.  Array classes: [I,
138   // [Ljava/lang/String;, etc.  Set to zero for all other kinds of classes.
139   Symbol*     _name;
140 
141   // Cache of last observed secondary supertype
142   Klass*      _secondary_super_cache;
143   // Array of all secondary supertypes
144   Array<Klass*>* _secondary_supers;
145   // Ordered list of all primary supertypes
146   Klass*      _primary_supers[_primary_super_limit];
147   // java/lang/Class instance mirroring this class
148   OopHandle   _java_mirror;
149   // Superclass
150   Klass*      _super;
151   // First subclass (null if none); _subklass->next_sibling() is next one
152   Klass* volatile _subklass;
153   // Sibling link (or null); links all subklasses of a klass
154   Klass* volatile _next_sibling;
155 
156   // All klasses loaded by a class loader are chained through these links
157   Klass*      _next_link;
158 
159   // The VM's representation of the ClassLoader used to load this class.
160   // Provide access the corresponding instance java.lang.ClassLoader.
161   ClassLoaderData* _class_loader_data;
162 
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                                 // Some flags created by the JVM, not in the class file itself,
170                                 // are in _misc_flags below.
171 
172   JFR_ONLY(DEFINE_TRACE_ID_FIELD;)
173 
174   // Bitmap and hash code used by hashed secondary supers.
175   uintx    _bitmap;
176   uint8_t  _hash_slot;
177 
178 private:
179   // This is an index into FileMapHeader::_shared_path_table[], to
180   // associate this class with the JAR file where it's loaded from during
181   // dump time. If a class is not loaded from the shared archive, this field is
182   // -1.
183   s2 _shared_class_path_index;
184 
185 #if INCLUDE_CDS
186   // Various attributes for shared classes. Should be zero for a non-shared class.
187   u2     _shared_class_flags;
188   enum CDSSharedClassFlags {
189     _is_shared_class                       = 1 << 0,  // shadows MetaspaceObj::is_shared
190     _archived_lambda_proxy_is_available    = 1 << 1,
191     _has_value_based_class_annotation      = 1 << 2,
192     _verified_at_dump_time                 = 1 << 3,
193     _has_archived_enum_objs                = 1 << 4,
194     // This class was not loaded from a classfile in the module image
195     // or classpath.
196     _is_generated_shared_class             = 1 << 5,
197     // The archived mirror is already initialized. No need to call <clinit>
198     _has_preinitialized_mirror             = 1 << 6,
199   };
200 #endif
201 
202   KlassFlags  _misc_flags;
203 
204   CDS_JAVA_HEAP_ONLY(int _archived_mirror_index;)
205 
206 protected:
207 
208   Klass(KlassKind kind);
209   Klass();
210 
211  public:
212   int kind() { return _kind; }
213 
214   enum class DefaultsLookupMode { find, skip };
215   enum class OverpassLookupMode { find, skip };
216   enum class StaticLookupMode   { find, skip };
217   enum class PrivateLookupMode  { find, skip };
218 
219   virtual bool is_klass() const { return true; }
220 
221   // super() cannot be InstanceKlass* -- Java arrays are covariant, and _super is used
222   // to implement that. NB: the _super of "[Ljava/lang/Integer;" is "[Ljava/lang/Number;"
223   // If this is not what your code expects, you're probably looking for Klass::java_super().
224   Klass* super() const               { return _super; }
225   void set_super(Klass* k)           { _super = k; }
226 
227   // initializes _super link, _primary_supers & _secondary_supers arrays
228   void initialize_supers(Klass* k, Array<InstanceKlass*>* transitive_interfaces, TRAPS);
229 
230   // klass-specific helper for initializing _secondary_supers
231   virtual GrowableArray<Klass*>* compute_secondary_supers(int num_extra_slots,
232                                                           Array<InstanceKlass*>* transitive_interfaces);
233 
234   // java_super is the Java-level super type as specified by Class.getSuperClass.
235   virtual InstanceKlass* java_super() const  { return nullptr; }
236 
237   juint    super_check_offset() const  { return _super_check_offset; }
238   void set_super_check_offset(juint o) { _super_check_offset = o; }
239 
240   Klass* secondary_super_cache() const     { return _secondary_super_cache; }
241   void set_secondary_super_cache(Klass* k) { _secondary_super_cache = k; }
242 
243   Array<Klass*>* secondary_supers() const { return _secondary_supers; }
244   void set_secondary_supers(Array<Klass*>* k);
245   void set_secondary_supers(Array<Klass*>* k, uintx bitmap);
246 
247   uint8_t hash_slot() const { return _hash_slot; }
248 
249   // Return the element of the _super chain of the given depth.
250   // If there is no such element, return either null or this.
251   Klass* primary_super_of_depth(juint i) const {
252     assert(i < primary_super_limit(), "oob");
253     Klass* super = _primary_supers[i];
254     assert(super == nullptr || super->super_depth() == i, "correct display");
255     return super;
256   }
257 
258   // Can this klass be a primary super?  False for interfaces and arrays of
259   // interfaces.  False also for arrays or classes with long super chains.
260   bool can_be_primary_super() const {
261     const juint secondary_offset = in_bytes(secondary_super_cache_offset());
262     return super_check_offset() != secondary_offset;
263   }
264   virtual bool can_be_primary_super_slow() const;
265 
266   // Returns number of primary supers; may be a number in the inclusive range [0, primary_super_limit].
267   juint super_depth() const {
268     if (!can_be_primary_super()) {
269       return primary_super_limit();
270     } else {
271       juint d = (super_check_offset() - in_bytes(primary_supers_offset())) / sizeof(Klass*);
272       assert(d < primary_super_limit(), "oob");
273       assert(_primary_supers[d] == this, "proper init");
274       return d;
275     }
276   }
277 
278   // java mirror
279   oop java_mirror() const;
280   oop java_mirror_no_keepalive() const;
281   void set_java_mirror(Handle m);
282 
283   oop archived_java_mirror() NOT_CDS_JAVA_HEAP_RETURN_(nullptr);
284   void set_archived_java_mirror(int mirror_index) NOT_CDS_JAVA_HEAP_RETURN;
285 
286   // Temporary mirror switch used by RedefineClasses
287   OopHandle java_mirror_handle() const { return _java_mirror; }
288   void swap_java_mirror_handle(OopHandle& mirror) { _java_mirror.swap(mirror); }
289 
290   // Set java mirror OopHandle to null for CDS
291   // This leaves the OopHandle in the CLD, but that's ok, you can't release them.
292   void clear_java_mirror_handle() { _java_mirror = OopHandle(); }
293 
294   // modifier flags
295   jint modifier_flags() const          { return _modifier_flags; }
296   void set_modifier_flags(jint flags)  { _modifier_flags = flags; }
297 
298   // size helper
299   int layout_helper() const            { return _layout_helper; }
300   void set_layout_helper(int lh)       { _layout_helper = lh; }
301 
302   // Note: for instances layout_helper() may include padding.
303   // Use InstanceKlass::contains_field_offset to classify field offsets.
304 
305   // sub/superklass links
306   Klass* subklass(bool log = false) const;
307   Klass* next_sibling(bool log = false) const;
308 
309   InstanceKlass* superklass() const;
310   void append_to_sibling_list();           // add newly created receiver to superklass' subklass list
311 
312   void set_next_link(Klass* k) { _next_link = k; }
313   Klass* next_link() const { return _next_link; }   // The next klass defined by the class loader.
314   Klass** next_link_addr() { return &_next_link; }
315 
316   // class loader data
317   ClassLoaderData* class_loader_data() const               { return _class_loader_data; }
318   void set_class_loader_data(ClassLoaderData* loader_data) {  _class_loader_data = loader_data; }
319 
320   s2 shared_classpath_index() const   {
321     return _shared_class_path_index;
322   };
323 
324   void set_shared_classpath_index(s2 index) {
325     _shared_class_path_index = index;
326   };
327 
328   bool has_archived_mirror_index() const {
329     CDS_JAVA_HEAP_ONLY(return _archived_mirror_index >= 0;)
330     NOT_CDS_JAVA_HEAP(return false);
331   }
332 
333   void clear_archived_mirror_index() NOT_CDS_JAVA_HEAP_RETURN;
334 
335   void set_lambda_proxy_is_available() {
336     CDS_ONLY(_shared_class_flags |= _archived_lambda_proxy_is_available;)
337   }
338   void clear_lambda_proxy_is_available() {
339     CDS_ONLY(_shared_class_flags &= (u2)(~_archived_lambda_proxy_is_available);)
340   }
341   bool lambda_proxy_is_available() const {
342     CDS_ONLY(return (_shared_class_flags & _archived_lambda_proxy_is_available) != 0;)
343     NOT_CDS(return false;)
344   }
345 
346   void set_has_value_based_class_annotation() {
347     CDS_ONLY(_shared_class_flags |= _has_value_based_class_annotation;)
348   }
349   void clear_has_value_based_class_annotation() {
350     CDS_ONLY(_shared_class_flags &= (u2)(~_has_value_based_class_annotation);)
351   }
352   bool has_value_based_class_annotation() const {
353     CDS_ONLY(return (_shared_class_flags & _has_value_based_class_annotation) != 0;)
354     NOT_CDS(return false;)
355   }
356 
357   void set_verified_at_dump_time() {
358     CDS_ONLY(_shared_class_flags |= _verified_at_dump_time;)
359   }
360   bool verified_at_dump_time() const {
361     CDS_ONLY(return (_shared_class_flags & _verified_at_dump_time) != 0;)
362     NOT_CDS(return false;)
363   }
364 
365   void set_has_archived_enum_objs() {
366     CDS_ONLY(_shared_class_flags |= _has_archived_enum_objs;)
367   }
368   bool has_archived_enum_objs() const {
369     CDS_ONLY(return (_shared_class_flags & _has_archived_enum_objs) != 0;)
370     NOT_CDS(return false;)
371   }
372 
373   void set_is_generated_shared_class() {
374     CDS_ONLY(_shared_class_flags |= _is_generated_shared_class;)
375   }
376   bool is_generated_shared_class() const {
377     CDS_ONLY(return (_shared_class_flags & _is_generated_shared_class) != 0;)
378     NOT_CDS(return false;)
379   }
380 
381   void set_has_preinitialized_mirror() {
382     CDS_ONLY(_shared_class_flags |= _has_preinitialized_mirror;)
383   }
384   bool has_preinitialized_mirror() const {
385     CDS_ONLY(return (_shared_class_flags & _has_preinitialized_mirror) != 0;)
386     NOT_CDS(return false;)
387   }
388 
389   bool is_shared() const                { // shadows MetaspaceObj::is_shared)()
390     CDS_ONLY(return (_shared_class_flags & _is_shared_class) != 0;)
391     NOT_CDS(return false;)
392   }
393 
394   void set_is_shared() {
395     CDS_ONLY(_shared_class_flags |= _is_shared_class;)
396   }
397 
398   // Obtain the module or package for this class
399   virtual ModuleEntry* module() const = 0;
400   virtual PackageEntry* package() const = 0;
401 
402  protected:                                // internal accessors
403   void     set_subklass(Klass* s);
404   void     set_next_sibling(Klass* s);
405 
406  private:
407   static uint8_t compute_hash_slot(Symbol* s);
408   static void  hash_insert(Klass* klass, GrowableArray<Klass*>* secondaries, uintx& bitmap);
409   static uintx hash_secondary_supers(Array<Klass*>* secondaries, bool rewrite);
410 
411  public:
412   // Secondary supers table support
413   static Array<Klass*>* pack_secondary_supers(ClassLoaderData* loader_data,
414                                               GrowableArray<Klass*>* primaries,
415                                               GrowableArray<Klass*>* secondaries,
416                                               uintx& bitmap,
417                                               TRAPS);
418 
419   static uintx   compute_secondary_supers_bitmap(Array<Klass*>* secondary_supers);
420   static uint8_t compute_home_slot(Klass* k, uintx bitmap);
421 
422   static constexpr int SECONDARY_SUPERS_TABLE_SIZE = sizeof(_bitmap) * 8;
423   static constexpr int SECONDARY_SUPERS_TABLE_MASK = SECONDARY_SUPERS_TABLE_SIZE - 1;
424 
425   static constexpr uintx SECONDARY_SUPERS_BITMAP_EMPTY    = 0;
426   static constexpr uintx SECONDARY_SUPERS_BITMAP_FULL     = ~(uintx)0;
427 
428   // Compiler support
429   static ByteSize super_offset()                 { return byte_offset_of(Klass, _super); }
430   static ByteSize super_check_offset_offset()    { return byte_offset_of(Klass, _super_check_offset); }
431   static ByteSize primary_supers_offset()        { return byte_offset_of(Klass, _primary_supers); }
432   static ByteSize secondary_super_cache_offset() { return byte_offset_of(Klass, _secondary_super_cache); }
433   static ByteSize secondary_supers_offset()      { return byte_offset_of(Klass, _secondary_supers); }
434   static ByteSize java_mirror_offset()           { return byte_offset_of(Klass, _java_mirror); }
435   static ByteSize class_loader_data_offset()     { return byte_offset_of(Klass, _class_loader_data); }
436   static ByteSize modifier_flags_offset()        { return byte_offset_of(Klass, _modifier_flags); }
437   static ByteSize layout_helper_offset()         { return byte_offset_of(Klass, _layout_helper); }
438   static ByteSize access_flags_offset()          { return byte_offset_of(Klass, _access_flags); }
439 #if INCLUDE_JVMCI
440   static ByteSize subklass_offset()              { return byte_offset_of(Klass, _subklass); }
441   static ByteSize next_sibling_offset()          { return byte_offset_of(Klass, _next_sibling); }
442 #endif
443   static ByteSize bitmap_offset()                { return byte_offset_of(Klass, _bitmap); }
444   static ByteSize misc_flags_offset()            { return byte_offset_of(Klass, _misc_flags._flags); }
445 
446   // Unpacking layout_helper:
447   static const int _lh_neutral_value           = 0;  // neutral non-array non-instance value
448   static const int _lh_instance_slow_path_bit  = 0x01;
449   static const int _lh_log2_element_size_shift = BitsPerByte*0;
450   static const int _lh_log2_element_size_mask  = BitsPerLong-1;
451   static const int _lh_element_type_shift      = BitsPerByte*1;
452   static const int _lh_element_type_mask       = right_n_bits(BitsPerByte);  // shifted mask
453   static const int _lh_header_size_shift       = BitsPerByte*2;
454   static const int _lh_header_size_mask        = right_n_bits(BitsPerByte);  // shifted mask
455   static const int _lh_array_tag_bits          = 2;
456   static const int _lh_array_tag_shift         = BitsPerInt - _lh_array_tag_bits;
457   static const int _lh_array_tag_obj_value     = ~0x01;   // 0x80000000 >> 30
458 
459   static const unsigned int _lh_array_tag_type_value = 0Xffffffff; // ~0x00,  // 0xC0000000 >> 30
460 
461   static int layout_helper_size_in_bytes(jint lh) {
462     assert(lh > (jint)_lh_neutral_value, "must be instance");
463     return (int) lh & ~_lh_instance_slow_path_bit;
464   }
465   static bool layout_helper_needs_slow_path(jint lh) {
466     assert(lh > (jint)_lh_neutral_value, "must be instance");
467     return (lh & _lh_instance_slow_path_bit) != 0;
468   }
469   static bool layout_helper_is_instance(jint lh) {
470     return (jint)lh > (jint)_lh_neutral_value;
471   }
472   static bool layout_helper_is_array(jint lh) {
473     return (jint)lh < (jint)_lh_neutral_value;
474   }
475   static bool layout_helper_is_typeArray(jint lh) {
476     // _lh_array_tag_type_value == (lh >> _lh_array_tag_shift);
477     return (juint)lh >= (juint)(_lh_array_tag_type_value << _lh_array_tag_shift);
478   }
479   static bool layout_helper_is_objArray(jint lh) {
480     // _lh_array_tag_obj_value == (lh >> _lh_array_tag_shift);
481     return (jint)lh < (jint)(_lh_array_tag_type_value << _lh_array_tag_shift);
482   }
483   static int layout_helper_header_size(jint lh) {
484     assert(lh < (jint)_lh_neutral_value, "must be array");
485     int hsize = (lh >> _lh_header_size_shift) & _lh_header_size_mask;
486     assert(hsize > 0 && hsize < (int)sizeof(oopDesc)*3, "sanity");
487     return hsize;
488   }
489   static BasicType layout_helper_element_type(jint lh) {
490     assert(lh < (jint)_lh_neutral_value, "must be array");
491     int btvalue = (lh >> _lh_element_type_shift) & _lh_element_type_mask;
492     assert(btvalue >= T_BOOLEAN && btvalue <= T_OBJECT, "sanity");
493     return (BasicType) btvalue;
494   }
495 
496   // Want a pattern to quickly diff against layout header in register
497   // find something less clever!
498   static int layout_helper_boolean_diffbit() {
499     jint zlh = array_layout_helper(T_BOOLEAN);
500     jint blh = array_layout_helper(T_BYTE);
501     assert(zlh != blh, "array layout helpers must differ");
502     int diffbit = 1;
503     while ((diffbit & (zlh ^ blh)) == 0 && (diffbit & zlh) == 0) {
504       diffbit <<= 1;
505       assert(diffbit != 0, "make sure T_BOOLEAN has a different bit than T_BYTE");
506     }
507     return diffbit;
508   }
509 
510   static int layout_helper_log2_element_size(jint lh) {
511     assert(lh < (jint)_lh_neutral_value, "must be array");
512     int l2esz = (lh >> _lh_log2_element_size_shift) & _lh_log2_element_size_mask;
513     assert(l2esz <= LogBytesPerLong,
514            "sanity. l2esz: 0x%x for lh: 0x%x", (uint)l2esz, (uint)lh);
515     return l2esz;
516   }
517   static jint array_layout_helper(jint tag, int hsize, BasicType etype, int log2_esize) {
518     return (tag        << _lh_array_tag_shift)
519       |    (hsize      << _lh_header_size_shift)
520       |    ((int)etype << _lh_element_type_shift)
521       |    (log2_esize << _lh_log2_element_size_shift);
522   }
523   static jint instance_layout_helper(jint size, bool slow_path_flag) {
524     return (size << LogBytesPerWord)
525       |    (slow_path_flag ? _lh_instance_slow_path_bit : 0);
526   }
527   static int layout_helper_to_size_helper(jint lh) {
528     assert(lh > (jint)_lh_neutral_value, "must be instance");
529     // Note that the following expression discards _lh_instance_slow_path_bit.
530     return lh >> LogBytesPerWord;
531   }
532   // Out-of-line version computes everything based on the etype:
533   static jint array_layout_helper(BasicType etype);
534 
535   // What is the maximum number of primary superclasses any klass can have?
536   static juint primary_super_limit()         { return _primary_super_limit; }
537 
538   // vtables
539   klassVtable vtable() const;
540   int vtable_length() const { return _vtable_len; }
541 
542   // subclass check
543   bool is_subclass_of(const Klass* k) const;
544   // subtype check: true if is_subclass_of, or if k is interface and receiver implements it
545   bool is_subtype_of(Klass* k) const {
546     juint    off = k->super_check_offset();
547     Klass* sup = *(Klass**)( (address)this + off );
548     const juint secondary_offset = in_bytes(secondary_super_cache_offset());
549     if (sup == k) {
550       return true;
551     } else if (off != secondary_offset) {
552       return false;
553     } else {
554       return search_secondary_supers(k);
555     }
556   }
557 
558   bool search_secondary_supers(Klass* k) const;
559 
560   // Find LCA in class hierarchy
561   Klass *LCA( Klass *k );
562 
563   // Check whether reflection/jni/jvm code is allowed to instantiate this class;
564   // if not, throw either an Error or an Exception.
565   virtual void check_valid_for_instantiation(bool throwError, TRAPS);
566 
567   // array copying
568   virtual void  copy_array(arrayOop s, int src_pos, arrayOop d, int dst_pos, int length, TRAPS);
569 
570   // tells if the class should be initialized
571   virtual bool should_be_initialized() const    { return false; }
572   // initializes the klass
573   virtual void initialize(TRAPS);
574   virtual Klass* find_field(Symbol* name, Symbol* signature, fieldDescriptor* fd) const;
575   virtual Method* uncached_lookup_method(const Symbol* name, const Symbol* signature,
576                                          OverpassLookupMode overpass_mode,
577                                          PrivateLookupMode = PrivateLookupMode::find) const;
578  public:
579   Method* lookup_method(const Symbol* name, const Symbol* signature) const {
580     return uncached_lookup_method(name, signature, OverpassLookupMode::find);
581   }
582 
583   // array class with specific rank
584   virtual ArrayKlass* array_klass(int rank, TRAPS) = 0;
585 
586   // array class with this klass as element type
587   virtual ArrayKlass* array_klass(TRAPS) = 0;
588 
589   // These will return null instead of allocating on the heap:
590   virtual ArrayKlass* array_klass_or_null(int rank) = 0;
591   virtual ArrayKlass* array_klass_or_null() = 0;
592 
593   virtual oop protection_domain() const = 0;
594 
595   oop class_loader() const;
596   Symbol* class_loader_name_and_id() const;
597 
598   inline oop klass_holder() const;
599 
600  protected:
601 
602   // Error handling when length > max_length or length < 0
603   static void check_array_allocation_length(int length, int max_length, TRAPS);
604 
605   void set_vtable_length(int len) { _vtable_len= len; }
606 
607   vtableEntry* start_of_vtable() const;
608 #if INCLUDE_CDS
609   void restore_unshareable_info(ClassLoaderData* loader_data, Handle protection_domain, TRAPS);
610 #endif
611  public:
612   Method* method_at_vtable(int index);
613 
614   static ByteSize vtable_start_offset();
615   static ByteSize vtable_length_offset() {
616     return byte_offset_of(Klass, _vtable_len);
617   }
618 
619 #if INCLUDE_CDS
620   // CDS support - remove and restore oops from metadata. Oops are not shared.
621   virtual void remove_unshareable_info();
622   virtual void remove_java_mirror();
623 
624   bool is_unshareable_info_restored() const {
625     assert(is_shared(), "use this for shared classes only");
626     if (has_archived_mirror_index()) {
627       // _java_mirror is not a valid OopHandle but rather an encoded reference in the shared heap
628       return false;
629     } else if (_java_mirror.is_empty()) {
630       return false;
631     } else {
632       return true;
633     }
634   }
635 #endif // INCLUDE_CDS
636 
637  public:
638   // ALL FUNCTIONS BELOW THIS POINT ARE DISPATCHED FROM AN OOP
639   // These functions describe behavior for the oop not the KLASS.
640 
641   // actual oop size of obj in memory in word size.
642   virtual size_t oop_size(oop obj) const = 0;
643 
644   // Size of klass in word size.
645   virtual int size() const = 0;
646 
647   // Returns the Java name for a class (Resource allocated)
648   // For arrays, this returns the name of the element with a leading '['.
649   // For classes, this returns the name with the package separators
650   //     turned into '.'s.
651   const char* external_name() const;
652   // Returns the name for a class (Resource allocated) as the class
653   // would appear in a signature.
654   // For arrays, this returns the name of the element with a leading '['.
655   // For classes, this returns the name with a leading 'L' and a trailing ';'
656   //     and the package separators as '/'.
657   virtual const char* signature_name() const;
658 
659   const char* joint_in_module_of_loader(const Klass* class2, bool include_parent_loader = false) const;
660   const char* class_in_module_of_loader(bool use_are = false, bool include_parent_loader = false) const;
661 
662   // Returns "interface", "abstract class" or "class".
663   const char* external_kind() const;
664 
665   // type testing operations
666 #ifdef ASSERT
667  protected:
668   virtual bool is_instance_klass_slow()     const { return false; }
669   virtual bool is_array_klass_slow()        const { return false; }
670   virtual bool is_objArray_klass_slow()     const { return false; }
671   virtual bool is_typeArray_klass_slow()    const { return false; }
672 #endif // ASSERT
673  public:
674 
675   // Fast non-virtual versions
676   #ifndef ASSERT
677   #define assert_same_query(xval, xcheck) xval
678   #else
679  private:
680   static bool assert_same_query(bool xval, bool xslow) {
681     assert(xval == xslow, "slow and fast queries agree");
682     return xval;
683   }
684  public:
685   #endif
686 
687   bool is_instance_klass()              const { return assert_same_query(_kind <= InstanceStackChunkKlassKind, is_instance_klass_slow()); }
688   // Other is anything that is not one of the more specialized kinds of InstanceKlass.
689   bool is_other_instance_klass()        const { return _kind == InstanceKlassKind; }
690   bool is_reference_instance_klass()    const { return _kind == InstanceRefKlassKind; }
691   bool is_mirror_instance_klass()       const { return _kind == InstanceMirrorKlassKind; }
692   bool is_class_loader_instance_klass() const { return _kind == InstanceClassLoaderKlassKind; }
693   bool is_array_klass()                 const { return assert_same_query( _kind >= TypeArrayKlassKind, is_array_klass_slow()); }
694   bool is_stack_chunk_instance_klass()  const { return _kind == InstanceStackChunkKlassKind; }
695   bool is_objArray_klass()              const { return assert_same_query( _kind == ObjArrayKlassKind,  is_objArray_klass_slow()); }
696   bool is_typeArray_klass()             const { return assert_same_query( _kind == TypeArrayKlassKind, is_typeArray_klass_slow()); }
697   #undef assert_same_query
698 
699   // Access flags
700   AccessFlags access_flags() const         { return _access_flags;  }
701   void set_access_flags(AccessFlags flags) { _access_flags = flags; }
702 
703   bool is_public() const                { return _access_flags.is_public(); }
704   bool is_final() const                 { return _access_flags.is_final(); }
705   bool is_interface() const             { return _access_flags.is_interface(); }
706   bool is_abstract() const              { return _access_flags.is_abstract(); }
707   bool is_super() const                 { return _access_flags.is_super(); }
708   bool is_synthetic() const             { return _access_flags.is_synthetic(); }
709   void set_is_synthetic()               { _access_flags.set_is_synthetic(); }
710   bool has_finalizer() const            { return _misc_flags.has_finalizer(); }
711   void set_has_finalizer()              { _misc_flags.set_has_finalizer(true); }
712   bool is_hidden() const                { return _misc_flags.is_hidden_class(); }
713   void set_is_hidden()                  { _misc_flags.set_is_hidden_class(true); }
714   bool is_value_based() const           { return _misc_flags.is_value_based_class(); }
715   void set_is_value_based()             { _misc_flags.set_is_value_based_class(true); }
716 
717   klass_flags_t misc_flags() const      { return _misc_flags.value(); }
718 
719   inline bool is_non_strong_hidden() const;
720 
721   bool is_cloneable() const;
722   void set_is_cloneable();
723 
724   JFR_ONLY(DEFINE_TRACE_ID_METHODS;)
725 
726   virtual void metaspace_pointers_do(MetaspaceClosure* iter);
727   virtual MetaspaceObj::Type type() const { return ClassType; }
728 
729   inline bool is_loader_alive() const;
730 
731   void clean_subklass();
732 
733   static void clean_weak_klass_links(bool unloading_occurred, bool clean_alive_klasses = true);
734   static void clean_subklass_tree() {
735     clean_weak_klass_links(/*unloading_occurred*/ true , /* clean_alive_klasses */ false);
736   }
737 
738   // Return self, except for abstract classes with exactly 1
739   // implementor.  Then return the 1 concrete implementation.
740   Klass *up_cast_abstract();
741 
742   // klass name
743   Symbol* name() const                   { return _name; }
744   void set_name(Symbol* n);
745 
746   virtual void release_C_heap_structures(bool release_constant_pool = true);
747 
748  public:
749   virtual jint compute_modifier_flags() const = 0;
750 
751   // JVMTI support
752   virtual jint jvmti_class_status() const;
753 
754   // Printing
755   virtual void print_on(outputStream* st) const;
756 
757   virtual void oop_print_value_on(oop obj, outputStream* st);
758   virtual void oop_print_on      (oop obj, outputStream* st);
759 
760   void print_secondary_supers_on(outputStream* st) const;
761 
762   virtual const char* internal_name() const = 0;
763 
764   // Verification
765   virtual void verify_on(outputStream* st);
766   void verify() { verify_on(tty); }
767 
768 #ifndef PRODUCT
769   bool verify_vtable_index(int index);
770 #endif
771 
772   virtual void oop_verify_on(oop obj, outputStream* st);
773 
774   // for error reporting
775   static bool is_valid(Klass* k);
776 
777   static void on_secondary_supers_verification_failure(Klass* super, Klass* sub, bool linear_result, bool table_result, const char* msg);
778 };
779 
780 #endif // SHARE_OOPS_KLASS_HPP
--- EOF ---