1 /*
   2  * Copyright (c) 1997, 2018, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #ifndef SHARE_VM_OOPS_KLASS_HPP
  26 #define SHARE_VM_OOPS_KLASS_HPP
  27 
  28 #include "classfile/classLoaderData.hpp"
  29 #include "gc/shared/specialized_oop_closures.hpp"
  30 #include "memory/iterator.hpp"
  31 #include "memory/memRegion.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 fieldDescriptor;
  59 class KlassSizeStats;
  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  protected:
  71   // If you add a new field that points to any metaspace object, you
  72   // must add this field to Klass::metaspace_pointers_do().
  73 
  74   // note: put frequently-used fields together at start of klass structure
  75   // for better cache behavior (may not make much of a difference but sure won't hurt)
  76   enum { _primary_super_limit = 8 };
  77 
  78   // The "layout helper" is a combined descriptor of object layout.
  79   // For klasses which are neither instance nor array, the value is zero.
  80   //
  81   // For instances, layout helper is a positive number, the instance size.
  82   // This size is already passed through align_object_size and scaled to bytes.
  83   // The low order bit is set if instances of this class cannot be
  84   // allocated using the fastpath.
  85   //
  86   // For arrays, layout helper is a negative number, containing four
  87   // distinct bytes, as follows:
  88   //    MSB:[tag, hsz, ebt, log2(esz)]:LSB
  89   // where:
  90   //    tag is 0x80 if the elements are oops, 0xC0 if non-oops
  91   //    hsz is array header size in bytes (i.e., offset of first element)
  92   //    ebt is the BasicType of the elements
  93   //    esz is the element size in bytes
  94   // This packed word is arranged so as to be quickly unpacked by the
  95   // various fast paths that use the various subfields.
  96   //
  97   // The esz bits can be used directly by a SLL instruction, without masking.
  98   //
  99   // Note that the array-kind tag looks like 0x00 for instance klasses,
 100   // since their length in bytes is always less than 24Mb.
 101   //
 102   // Final note:  This comes first, immediately after C++ vtable,
 103   // because it is frequently queried.
 104   jint        _layout_helper;
 105 
 106   // The fields _super_check_offset, _secondary_super_cache, _secondary_supers
 107   // and _primary_supers all help make fast subtype checks.  See big discussion
 108   // in doc/server_compiler/checktype.txt
 109   //
 110   // Where to look to observe a supertype (it is &_secondary_super_cache for
 111   // secondary supers, else is &_primary_supers[depth()].
 112   juint       _super_check_offset;
 113 
 114   // Class name.  Instance classes: java/lang/String, etc.  Array classes: [I,
 115   // [Ljava/lang/String;, etc.  Set to zero for all other kinds of classes.
 116   Symbol*     _name;
 117 
 118   // Cache of last observed secondary supertype
 119   Klass*      _secondary_super_cache;
 120   // Array of all secondary supertypes
 121   Array<Klass*>* _secondary_supers;
 122   // Ordered list of all primary supertypes
 123   Klass*      _primary_supers[_primary_super_limit];
 124   // java/lang/Class instance mirroring this class
 125   OopHandle _java_mirror;
 126   // Superclass
 127   Klass*      _super;
 128   // First subclass (NULL if none); _subklass->next_sibling() is next one
 129   Klass*      _subklass;
 130   // Sibling link (or NULL); links all subklasses of a klass
 131   Klass*      _next_sibling;
 132 
 133   // All klasses loaded by a class loader are chained through these links
 134   Klass*      _next_link;
 135 
 136   // The VM's representation of the ClassLoader used to load this class.
 137   // Provide access the corresponding instance java.lang.ClassLoader.
 138   ClassLoaderData* _class_loader_data;
 139 
 140   jint        _modifier_flags;  // Processed access flags, for use by Class.getModifiers.
 141   AccessFlags _access_flags;    // Access flags. The class/interface distinction is stored here.
 142 
 143   JFR_ONLY(DEFINE_TRACE_ID_FIELD;)
 144 
 145   // Biased locking implementation and statistics
 146   // (the 64-bit chunk goes first, to avoid some fragmentation)
 147   jlong    _last_biased_lock_bulk_revocation_time;
 148   markOop  _prototype_header;   // Used when biased locking is both enabled and disabled for this type
 149   jint     _biased_lock_revocation_count;
 150 
 151   // vtable length
 152   int _vtable_len;
 153 
 154 private:
 155   // This is an index into FileMapHeader::_shared_path_table[], to
 156   // associate this class with the JAR file where it's loaded from during
 157   // dump time. If a class is not loaded from the shared archive, this field is
 158   // -1.
 159   jshort _shared_class_path_index;
 160 
 161 #if INCLUDE_CDS
 162   // Flags of the current shared class.
 163   u2     _shared_class_flags;
 164   enum {
 165     _has_raw_archived_mirror = 1,
 166     _has_signer_and_not_archived = 1 << 2
 167   };
 168 #endif
 169   // The _archived_mirror is set at CDS dump time pointing to the cached mirror
 170   // in the open archive heap region when archiving java object is supported.
 171   CDS_JAVA_HEAP_ONLY(narrowOop _archived_mirror;)
 172 
 173 protected:
 174 
 175   // Constructor
 176   Klass();
 177 
 178   void* operator new(size_t size, ClassLoaderData* loader_data, size_t word_size, TRAPS) throw();
 179 
 180  public:
 181   enum DefaultsLookupMode { find_defaults, skip_defaults };
 182   enum OverpassLookupMode { find_overpass, skip_overpass };
 183   enum StaticLookupMode   { find_static,   skip_static };
 184   enum PrivateLookupMode  { find_private,  skip_private };
 185 
 186   bool is_klass() const volatile { return true; }
 187 
 188   // super
 189   Klass* super() const               { return _super; }
 190   void set_super(Klass* k)           { _super = k; }
 191 
 192   // initializes _super link, _primary_supers & _secondary_supers arrays
 193   void initialize_supers(Klass* k, Array<Klass*>* transitive_interfaces, TRAPS);
 194   void initialize_supers_impl1(Klass* k);
 195   void initialize_supers_impl2(Klass* k);
 196 
 197   // klass-specific helper for initializing _secondary_supers
 198   virtual GrowableArray<Klass*>* compute_secondary_supers(int num_extra_slots,
 199                                                           Array<Klass*>* transitive_interfaces);
 200 
 201   // java_super is the Java-level super type as specified by Class.getSuperClass.
 202   virtual Klass* java_super() const  { return NULL; }
 203 
 204   juint    super_check_offset() const  { return _super_check_offset; }
 205   void set_super_check_offset(juint o) { _super_check_offset = o; }
 206 
 207   Klass* secondary_super_cache() const     { return _secondary_super_cache; }
 208   void set_secondary_super_cache(Klass* k) { _secondary_super_cache = k; }
 209 
 210   Array<Klass*>* secondary_supers() const { return _secondary_supers; }
 211   void set_secondary_supers(Array<Klass*>* k) { _secondary_supers = k; }
 212 
 213   // Return the element of the _super chain of the given depth.
 214   // If there is no such element, return either NULL or this.
 215   Klass* primary_super_of_depth(juint i) const {
 216     assert(i < primary_super_limit(), "oob");
 217     Klass* super = _primary_supers[i];
 218     assert(super == NULL || super->super_depth() == i, "correct display");
 219     return super;
 220   }
 221 
 222   // Can this klass be a primary super?  False for interfaces and arrays of
 223   // interfaces.  False also for arrays or classes with long super chains.
 224   bool can_be_primary_super() const {
 225     const juint secondary_offset = in_bytes(secondary_super_cache_offset());
 226     return super_check_offset() != secondary_offset;
 227   }
 228   virtual bool can_be_primary_super_slow() const;
 229 
 230   // Returns number of primary supers; may be a number in the inclusive range [0, primary_super_limit].
 231   juint super_depth() const {
 232     if (!can_be_primary_super()) {
 233       return primary_super_limit();
 234     } else {
 235       juint d = (super_check_offset() - in_bytes(primary_supers_offset())) / sizeof(Klass*);
 236       assert(d < primary_super_limit(), "oob");
 237       assert(_primary_supers[d] == this, "proper init");
 238       return d;
 239     }
 240   }
 241 
 242   // java mirror
 243   oop java_mirror() const;
 244   void set_java_mirror(Handle m);
 245 
 246   oop archived_java_mirror_raw() NOT_CDS_JAVA_HEAP_RETURN_(NULL); // no GC barrier
 247   void set_archived_java_mirror_raw(oop m) NOT_CDS_JAVA_HEAP_RETURN; // no GC barrier
 248 
 249   // Temporary mirror switch used by RedefineClasses
 250   // Both mirrors are on the ClassLoaderData::_handles list already so no
 251   // barriers are needed.
 252   void set_java_mirror_handle(OopHandle mirror) { _java_mirror = mirror; }
 253   OopHandle java_mirror_handle() const          {
 254     return _java_mirror;
 255   }
 256 
 257   // modifier flags
 258   jint modifier_flags() const          { return _modifier_flags; }
 259   void set_modifier_flags(jint flags)  { _modifier_flags = flags; }
 260 
 261   // size helper
 262   int layout_helper() const            { return _layout_helper; }
 263   void set_layout_helper(int lh)       { _layout_helper = lh; }
 264 
 265   // Note: for instances layout_helper() may include padding.
 266   // Use InstanceKlass::contains_field_offset to classify field offsets.
 267 
 268   // sub/superklass links
 269   Klass* subklass() const              { return _subklass; }
 270   Klass* next_sibling() const          { return _next_sibling; }
 271   InstanceKlass* superklass() const;
 272   void append_to_sibling_list();           // add newly created receiver to superklass' subklass list
 273 
 274   void set_next_link(Klass* k) { _next_link = k; }
 275   Klass* next_link() const { return _next_link; }   // The next klass defined by the class loader.
 276 
 277   // class loader data
 278   ClassLoaderData* class_loader_data() const               { return _class_loader_data; }
 279   void set_class_loader_data(ClassLoaderData* loader_data) {  _class_loader_data = loader_data; }
 280 
 281   int shared_classpath_index() const   {
 282     return _shared_class_path_index;
 283   };
 284 
 285   void set_shared_classpath_index(int index) {
 286     _shared_class_path_index = index;
 287   };
 288 
 289   void set_has_raw_archived_mirror() {
 290     CDS_ONLY(_shared_class_flags |= _has_raw_archived_mirror;)
 291   }
 292   void clear_has_raw_archived_mirror() {
 293     CDS_ONLY(_shared_class_flags &= ~_has_raw_archived_mirror;)
 294   }
 295   bool has_raw_archived_mirror() const {
 296     CDS_ONLY(return (_shared_class_flags & _has_raw_archived_mirror) != 0;)
 297     NOT_CDS(return false;)
 298   }
 299 #if INCLUDE_CDS
 300   void set_has_signer_and_not_archived() {
 301     _shared_class_flags |= _has_signer_and_not_archived;
 302   }
 303   bool has_signer_and_not_archived() const {
 304     assert(DumpSharedSpaces, "dump time only");
 305     return (_shared_class_flags & _has_signer_and_not_archived) != 0;
 306   }
 307 #endif // INCLUDE_CDS
 308 
 309   // Obtain the module or package for this class
 310   virtual ModuleEntry* module() const = 0;
 311   virtual PackageEntry* package() const = 0;
 312 
 313  protected:                                // internal accessors
 314   void     set_subklass(Klass* s);
 315   void     set_next_sibling(Klass* s);
 316 
 317  public:
 318 
 319   // Compiler support
 320   static ByteSize super_offset()                 { return in_ByteSize(offset_of(Klass, _super)); }
 321   static ByteSize super_check_offset_offset()    { return in_ByteSize(offset_of(Klass, _super_check_offset)); }
 322   static ByteSize primary_supers_offset()        { return in_ByteSize(offset_of(Klass, _primary_supers)); }
 323   static ByteSize secondary_super_cache_offset() { return in_ByteSize(offset_of(Klass, _secondary_super_cache)); }
 324   static ByteSize secondary_supers_offset()      { return in_ByteSize(offset_of(Klass, _secondary_supers)); }
 325   static ByteSize java_mirror_offset()           { return in_ByteSize(offset_of(Klass, _java_mirror)); }
 326   static ByteSize modifier_flags_offset()        { return in_ByteSize(offset_of(Klass, _modifier_flags)); }
 327   static ByteSize layout_helper_offset()         { return in_ByteSize(offset_of(Klass, _layout_helper)); }
 328   static ByteSize access_flags_offset()          { return in_ByteSize(offset_of(Klass, _access_flags)); }
 329 
 330   // Unpacking layout_helper:
 331   enum {
 332     _lh_neutral_value           = 0,  // neutral non-array non-instance value
 333     _lh_instance_slow_path_bit  = 0x01,
 334     _lh_log2_element_size_shift = BitsPerByte*0,
 335     _lh_log2_element_size_mask  = BitsPerLong-1,
 336     _lh_element_type_shift      = BitsPerByte*1,
 337     _lh_element_type_mask       = right_n_bits(BitsPerByte),  // shifted mask
 338     _lh_header_size_shift       = BitsPerByte*2,
 339     _lh_header_size_mask        = right_n_bits(BitsPerByte),  // shifted mask
 340     _lh_array_tag_bits          = 2,
 341     _lh_array_tag_shift         = BitsPerInt - _lh_array_tag_bits,
 342     _lh_array_tag_obj_value     = ~0x01   // 0x80000000 >> 30
 343   };
 344 
 345   static const unsigned int _lh_array_tag_type_value = 0Xffffffff; // ~0x00,  // 0xC0000000 >> 30
 346 
 347   static int layout_helper_size_in_bytes(jint lh) {
 348     assert(lh > (jint)_lh_neutral_value, "must be instance");
 349     return (int) lh & ~_lh_instance_slow_path_bit;
 350   }
 351   static bool layout_helper_needs_slow_path(jint lh) {
 352     assert(lh > (jint)_lh_neutral_value, "must be instance");
 353     return (lh & _lh_instance_slow_path_bit) != 0;
 354   }
 355   static bool layout_helper_is_instance(jint lh) {
 356     return (jint)lh > (jint)_lh_neutral_value;
 357   }
 358   static bool layout_helper_is_array(jint lh) {
 359     return (jint)lh < (jint)_lh_neutral_value;
 360   }
 361   static bool layout_helper_is_typeArray(jint lh) {
 362     // _lh_array_tag_type_value == (lh >> _lh_array_tag_shift);
 363     return (juint)lh >= (juint)(_lh_array_tag_type_value << _lh_array_tag_shift);
 364   }
 365   static bool layout_helper_is_objArray(jint lh) {
 366     // _lh_array_tag_obj_value == (lh >> _lh_array_tag_shift);
 367     return (jint)lh < (jint)(_lh_array_tag_type_value << _lh_array_tag_shift);
 368   }
 369   static int layout_helper_header_size(jint lh) {
 370     assert(lh < (jint)_lh_neutral_value, "must be array");
 371     int hsize = (lh >> _lh_header_size_shift) & _lh_header_size_mask;
 372     assert(hsize > 0 && hsize < (int)sizeof(oopDesc)*3, "sanity");
 373     return hsize;
 374   }
 375   static BasicType layout_helper_element_type(jint lh) {
 376     assert(lh < (jint)_lh_neutral_value, "must be array");
 377     int btvalue = (lh >> _lh_element_type_shift) & _lh_element_type_mask;
 378     assert(btvalue >= T_BOOLEAN && btvalue <= T_OBJECT, "sanity");
 379     return (BasicType) btvalue;
 380   }
 381 
 382   // Want a pattern to quickly diff against layout header in register
 383   // find something less clever!
 384   static int layout_helper_boolean_diffbit() {
 385     jint zlh = array_layout_helper(T_BOOLEAN);
 386     jint blh = array_layout_helper(T_BYTE);
 387     assert(zlh != blh, "array layout helpers must differ");
 388     int diffbit = 1;
 389     while ((diffbit & (zlh ^ blh)) == 0 && (diffbit & zlh) == 0) {
 390       diffbit <<= 1;
 391       assert(diffbit != 0, "make sure T_BOOLEAN has a different bit than T_BYTE");
 392     }
 393     return diffbit;
 394   }
 395 
 396   static int layout_helper_log2_element_size(jint lh) {
 397     assert(lh < (jint)_lh_neutral_value, "must be array");
 398     int l2esz = (lh >> _lh_log2_element_size_shift) & _lh_log2_element_size_mask;
 399     assert(l2esz <= LogBytesPerLong,
 400            "sanity. l2esz: 0x%x for lh: 0x%x", (uint)l2esz, (uint)lh);
 401     return l2esz;
 402   }
 403   static jint array_layout_helper(jint tag, int hsize, BasicType etype, int log2_esize) {
 404     return (tag        << _lh_array_tag_shift)
 405       |    (hsize      << _lh_header_size_shift)
 406       |    ((int)etype << _lh_element_type_shift)
 407       |    (log2_esize << _lh_log2_element_size_shift);
 408   }
 409   static jint instance_layout_helper(jint size, bool slow_path_flag) {
 410     return (size << LogBytesPerWord)
 411       |    (slow_path_flag ? _lh_instance_slow_path_bit : 0);
 412   }
 413   static int layout_helper_to_size_helper(jint lh) {
 414     assert(lh > (jint)_lh_neutral_value, "must be instance");
 415     // Note that the following expression discards _lh_instance_slow_path_bit.
 416     return lh >> LogBytesPerWord;
 417   }
 418   // Out-of-line version computes everything based on the etype:
 419   static jint array_layout_helper(BasicType etype);
 420 
 421   // What is the maximum number of primary superclasses any klass can have?
 422 #ifdef PRODUCT
 423   static juint primary_super_limit()         { return _primary_super_limit; }
 424 #else
 425   static juint primary_super_limit() {
 426     assert(FastSuperclassLimit <= _primary_super_limit, "parameter oob");
 427     return FastSuperclassLimit;
 428   }
 429 #endif
 430 
 431   // vtables
 432   klassVtable vtable() const;
 433   int vtable_length() const { return _vtable_len; }
 434 
 435   // subclass check
 436   bool is_subclass_of(const Klass* k) const;
 437   // subtype check: true if is_subclass_of, or if k is interface and receiver implements it
 438   bool is_subtype_of(Klass* k) const {
 439     juint    off = k->super_check_offset();
 440     Klass* sup = *(Klass**)( (address)this + off );
 441     const juint secondary_offset = in_bytes(secondary_super_cache_offset());
 442     if (sup == k) {
 443       return true;
 444     } else if (off != secondary_offset) {
 445       return false;
 446     } else {
 447       return search_secondary_supers(k);
 448     }
 449   }
 450 
 451   bool search_secondary_supers(Klass* k) const;
 452 
 453   // Find LCA in class hierarchy
 454   Klass *LCA( Klass *k );
 455 
 456   // Check whether reflection/jni/jvm code is allowed to instantiate this class;
 457   // if not, throw either an Error or an Exception.
 458   virtual void check_valid_for_instantiation(bool throwError, TRAPS);
 459 
 460   // array copying
 461   virtual void  copy_array(arrayOop s, int src_pos, arrayOop d, int dst_pos, int length, TRAPS);
 462 
 463   // tells if the class should be initialized
 464   virtual bool should_be_initialized() const    { return false; }
 465   // initializes the klass
 466   virtual void initialize(TRAPS);
 467   // lookup operation for MethodLookupCache
 468   friend class MethodLookupCache;
 469   virtual Klass* find_field(Symbol* name, Symbol* signature, fieldDescriptor* fd) const;
 470   virtual Method* uncached_lookup_method(const Symbol* name, const Symbol* signature, OverpassLookupMode overpass_mode) const;
 471  public:
 472   Method* lookup_method(const Symbol* name, const Symbol* signature) const {
 473     return uncached_lookup_method(name, signature, find_overpass);
 474   }
 475 
 476   // array class with specific rank
 477   Klass* array_klass(int rank, TRAPS)         {  return array_klass_impl(false, rank, THREAD); }
 478 
 479   // array class with this klass as element type
 480   Klass* array_klass(TRAPS)                   {  return array_klass_impl(false, THREAD); }
 481 
 482   // These will return NULL instead of allocating on the heap:
 483   // NB: these can block for a mutex, like other functions with TRAPS arg.
 484   Klass* array_klass_or_null(int rank);
 485   Klass* array_klass_or_null();
 486 
 487   virtual oop protection_domain() const = 0;
 488 
 489   oop class_loader() const;
 490 
 491   virtual oop klass_holder() const      { return class_loader(); }
 492 
 493  protected:
 494   virtual Klass* array_klass_impl(bool or_null, int rank, TRAPS);
 495   virtual Klass* array_klass_impl(bool or_null, TRAPS);
 496 
 497   void set_vtable_length(int len) { _vtable_len= len; }
 498 
 499   vtableEntry* start_of_vtable() const;
 500  public:
 501   Method* method_at_vtable(int index);
 502 
 503   static ByteSize vtable_start_offset();
 504   static ByteSize vtable_length_offset() {
 505     return byte_offset_of(Klass, _vtable_len);
 506   }
 507 
 508   // CDS support - remove and restore oops from metadata. Oops are not shared.
 509   virtual void remove_unshareable_info();
 510   virtual void remove_java_mirror();
 511   virtual void restore_unshareable_info(ClassLoaderData* loader_data, Handle protection_domain, TRAPS);
 512 
 513  protected:
 514   // computes the subtype relationship
 515   virtual bool compute_is_subtype_of(Klass* k);
 516  public:
 517   // subclass accessor (here for convenience; undefined for non-klass objects)
 518   virtual bool is_leaf_class() const { fatal("not a class"); return false; }
 519  public:
 520   // ALL FUNCTIONS BELOW THIS POINT ARE DISPATCHED FROM AN OOP
 521   // These functions describe behavior for the oop not the KLASS.
 522 
 523   // actual oop size of obj in memory
 524   virtual int oop_size(oop obj) const = 0;
 525 
 526   // Size of klass in word size.
 527   virtual int size() const = 0;
 528 #if INCLUDE_SERVICES
 529   virtual void collect_statistics(KlassSizeStats *sz) const;
 530 #endif
 531 
 532   // Returns the Java name for a class (Resource allocated)
 533   // For arrays, this returns the name of the element with a leading '['.
 534   // For classes, this returns the name with the package separators
 535   //     turned into '.'s.
 536   const char* external_name() const;
 537   // Returns the name for a class (Resource allocated) as the class
 538   // would appear in a signature.
 539   // For arrays, this returns the name of the element with a leading '['.
 540   // For classes, this returns the name with a leading 'L' and a trailing ';'
 541   //     and the package separators as '/'.
 542   virtual const char* signature_name() const;
 543 
 544   const char* class_loader_and_module_name() const;
 545 
 546   // Returns "interface", "abstract class" or "class".
 547   const char* external_kind() const;
 548 
 549   // type testing operations
 550 #ifdef ASSERT
 551  protected:
 552   virtual bool is_instance_klass_slow()     const { return false; }
 553   virtual bool is_array_klass_slow()        const { return false; }
 554   virtual bool is_objArray_klass_slow()     const { return false; }
 555   virtual bool is_typeArray_klass_slow()    const { return false; }
 556 #endif // ASSERT
 557  public:
 558 
 559   // Fast non-virtual versions
 560   #ifndef ASSERT
 561   #define assert_same_query(xval, xcheck) xval
 562   #else
 563  private:
 564   static bool assert_same_query(bool xval, bool xslow) {
 565     assert(xval == xslow, "slow and fast queries agree");
 566     return xval;
 567   }
 568  public:
 569   #endif
 570   inline  bool is_instance_klass()            const { return assert_same_query(
 571                                                       layout_helper_is_instance(layout_helper()),
 572                                                       is_instance_klass_slow()); }
 573   inline  bool is_array_klass()               const { return assert_same_query(
 574                                                     layout_helper_is_array(layout_helper()),
 575                                                     is_array_klass_slow()); }
 576   inline  bool is_objArray_klass()            const { return assert_same_query(
 577                                                     layout_helper_is_objArray(layout_helper()),
 578                                                     is_objArray_klass_slow()); }
 579   inline  bool is_typeArray_klass()           const { return assert_same_query(
 580                                                     layout_helper_is_typeArray(layout_helper()),
 581                                                     is_typeArray_klass_slow()); }
 582   #undef assert_same_query
 583 
 584   // Access flags
 585   AccessFlags access_flags() const         { return _access_flags;  }
 586   void set_access_flags(AccessFlags flags) { _access_flags = flags; }
 587 
 588   bool is_public() const                { return _access_flags.is_public(); }
 589   bool is_final() const                 { return _access_flags.is_final(); }
 590   bool is_interface() const             { return _access_flags.is_interface(); }
 591   bool is_abstract() const              { return _access_flags.is_abstract(); }
 592   bool is_super() const                 { return _access_flags.is_super(); }
 593   bool is_synthetic() const             { return _access_flags.is_synthetic(); }
 594   void set_is_synthetic()               { _access_flags.set_is_synthetic(); }
 595   bool has_finalizer() const            { return _access_flags.has_finalizer(); }
 596   bool has_final_method() const         { return _access_flags.has_final_method(); }
 597   void set_has_finalizer()              { _access_flags.set_has_finalizer(); }
 598   void set_has_final_method()           { _access_flags.set_has_final_method(); }
 599   bool has_vanilla_constructor() const  { return _access_flags.has_vanilla_constructor(); }
 600   void set_has_vanilla_constructor()    { _access_flags.set_has_vanilla_constructor(); }
 601   bool has_miranda_methods () const     { return access_flags().has_miranda_methods(); }
 602   void set_has_miranda_methods()        { _access_flags.set_has_miranda_methods(); }
 603   bool is_shared() const                { return access_flags().is_shared_class(); } // shadows MetaspaceObj::is_shared)()
 604   void set_is_shared()                  { _access_flags.set_is_shared_class(); }
 605 
 606   bool is_cloneable() const;
 607   void set_is_cloneable();
 608 
 609   // Biased locking support
 610   // Note: the prototype header is always set up to be at least the
 611   // prototype markOop. If biased locking is enabled it may further be
 612   // biasable and have an epoch.
 613   markOop prototype_header() const      { return _prototype_header; }
 614   // NOTE: once instances of this klass are floating around in the
 615   // system, this header must only be updated at a safepoint.
 616   // NOTE 2: currently we only ever set the prototype header to the
 617   // biasable prototype for instanceKlasses. There is no technical
 618   // reason why it could not be done for arrayKlasses aside from
 619   // wanting to reduce the initial scope of this optimization. There
 620   // are potential problems in setting the bias pattern for
 621   // JVM-internal oops.
 622   inline void set_prototype_header(markOop header);
 623   static ByteSize prototype_header_offset() { return in_ByteSize(offset_of(Klass, _prototype_header)); }
 624 
 625   int  biased_lock_revocation_count() const { return (int) _biased_lock_revocation_count; }
 626   // Atomically increments biased_lock_revocation_count and returns updated value
 627   int atomic_incr_biased_lock_revocation_count();
 628   void set_biased_lock_revocation_count(int val) { _biased_lock_revocation_count = (jint) val; }
 629   jlong last_biased_lock_bulk_revocation_time() { return _last_biased_lock_bulk_revocation_time; }
 630   void  set_last_biased_lock_bulk_revocation_time(jlong cur_time) { _last_biased_lock_bulk_revocation_time = cur_time; }
 631 
 632   JFR_ONLY(DEFINE_TRACE_ID_METHODS;)
 633 
 634   virtual void metaspace_pointers_do(MetaspaceClosure* iter);
 635   virtual MetaspaceObj::Type type() const { return ClassType; }
 636 
 637   // Iff the class loader (or mirror for anonymous classes) is alive the
 638   // Klass is considered alive.  Has already been marked as unloading.
 639   bool is_loader_alive() const { return !class_loader_data()->is_unloading(); }
 640 
 641   static void clean_weak_klass_links(bool unloading_occurred, bool clean_alive_klasses = true);
 642   static void clean_subklass_tree() {
 643     clean_weak_klass_links(/*unloading_occurred*/ true , /* clean_alive_klasses */ false);
 644   }
 645 
 646   // GC specific object visitors
 647   //
 648 #if INCLUDE_PARALLELGC
 649   // Parallel Scavenge
 650   virtual void oop_ps_push_contents(  oop obj, PSPromotionManager* pm)   = 0;
 651   // Parallel Compact
 652   virtual void oop_pc_follow_contents(oop obj, ParCompactionManager* cm) = 0;
 653   virtual void oop_pc_update_pointers(oop obj, ParCompactionManager* cm) = 0;
 654 #endif
 655 
 656   // Iterators specialized to particular subtypes
 657   // of ExtendedOopClosure, to avoid closure virtual calls.
 658 #define Klass_OOP_OOP_ITERATE_DECL(OopClosureType, nv_suffix)                                           \
 659   virtual void oop_oop_iterate##nv_suffix(oop obj, OopClosureType* closure) = 0;                        \
 660   /* Iterates "closure" over all the oops in "obj" (of type "this") within "mr". */                     \
 661   virtual void oop_oop_iterate_bounded##nv_suffix(oop obj, OopClosureType* closure, MemRegion mr) = 0;
 662 
 663   ALL_OOP_OOP_ITERATE_CLOSURES_1(Klass_OOP_OOP_ITERATE_DECL)
 664   ALL_OOP_OOP_ITERATE_CLOSURES_2(Klass_OOP_OOP_ITERATE_DECL)
 665 
 666 #if INCLUDE_OOP_OOP_ITERATE_BACKWARDS
 667 #define Klass_OOP_OOP_ITERATE_DECL_BACKWARDS(OopClosureType, nv_suffix)                     \
 668   virtual void oop_oop_iterate_backwards##nv_suffix(oop obj, OopClosureType* closure) = 0;
 669 
 670   ALL_OOP_OOP_ITERATE_CLOSURES_1(Klass_OOP_OOP_ITERATE_DECL_BACKWARDS)
 671   ALL_OOP_OOP_ITERATE_CLOSURES_2(Klass_OOP_OOP_ITERATE_DECL_BACKWARDS)
 672 #endif
 673 
 674   virtual void array_klasses_do(void f(Klass* k)) {}
 675 
 676   // Return self, except for abstract classes with exactly 1
 677   // implementor.  Then return the 1 concrete implementation.
 678   Klass *up_cast_abstract();
 679 
 680   // klass name
 681   Symbol* name() const                   { return _name; }
 682   void set_name(Symbol* n);
 683 
 684  public:
 685   // jvm support
 686   virtual jint compute_modifier_flags(TRAPS) const;
 687 
 688   // JVMTI support
 689   virtual jint jvmti_class_status() const;
 690 
 691   // Printing
 692   virtual void print_on(outputStream* st) const;
 693 
 694   virtual void oop_print_value_on(oop obj, outputStream* st);
 695   virtual void oop_print_on      (oop obj, outputStream* st);
 696 
 697   virtual const char* internal_name() const = 0;
 698 
 699   // Verification
 700   virtual void verify_on(outputStream* st);
 701   void verify() { verify_on(tty); }
 702 
 703 #ifndef PRODUCT
 704   bool verify_vtable_index(int index);
 705   bool verify_itable_index(int index);
 706 #endif
 707 
 708   virtual void oop_verify_on(oop obj, outputStream* st);
 709 
 710   static bool is_null(narrowKlass obj);
 711   static bool is_null(Klass* obj);
 712 
 713   // klass encoding for klass pointer in objects.
 714   static narrowKlass encode_klass_not_null(Klass* v);
 715   static narrowKlass encode_klass(Klass* v);
 716 
 717   static Klass* decode_klass_not_null(narrowKlass v);
 718   static Klass* decode_klass(narrowKlass v);
 719 };
 720 
 721 // Helper to convert the oop iterate macro suffixes into bool values that can be used by template functions.
 722 #define nvs_nv_to_bool true
 723 #define nvs_v_to_bool  false
 724 #define nvs_to_bool(nv_suffix) nvs##nv_suffix##_to_bool
 725 
 726 // Oop iteration macros for declarations.
 727 // Used to generate declarations in the *Klass header files.
 728 
 729 #define OOP_OOP_ITERATE_DECL(OopClosureType, nv_suffix)                                    \
 730   void oop_oop_iterate##nv_suffix(oop obj, OopClosureType* closure);                        \
 731   void oop_oop_iterate_bounded##nv_suffix(oop obj, OopClosureType* closure, MemRegion mr);
 732 
 733 #if INCLUDE_OOP_OOP_ITERATE_BACKWARDS
 734 #define OOP_OOP_ITERATE_DECL_BACKWARDS(OopClosureType, nv_suffix)               \
 735   void oop_oop_iterate_backwards##nv_suffix(oop obj, OopClosureType* closure);
 736 #endif
 737 
 738 
 739 // Oop iteration macros for definitions.
 740 // Used to generate definitions in the *Klass.inline.hpp files.
 741 
 742 #define OOP_OOP_ITERATE_DEFN(KlassType, OopClosureType, nv_suffix)              \
 743 void KlassType::oop_oop_iterate##nv_suffix(oop obj, OopClosureType* closure) {  \
 744   oop_oop_iterate<nvs_to_bool(nv_suffix)>(obj, closure);                        \
 745 }
 746 
 747 #if INCLUDE_OOP_OOP_ITERATE_BACKWARDS
 748 #define OOP_OOP_ITERATE_DEFN_BACKWARDS(KlassType, OopClosureType, nv_suffix)              \
 749 void KlassType::oop_oop_iterate_backwards##nv_suffix(oop obj, OopClosureType* closure) {  \
 750   oop_oop_iterate_reverse<nvs_to_bool(nv_suffix)>(obj, closure);                          \
 751 }
 752 #else
 753 #define OOP_OOP_ITERATE_DEFN_BACKWARDS(KlassType, OopClosureType, nv_suffix)
 754 #endif
 755 
 756 #define OOP_OOP_ITERATE_DEFN_BOUNDED(KlassType, OopClosureType, nv_suffix)                            \
 757 void KlassType::oop_oop_iterate_bounded##nv_suffix(oop obj, OopClosureType* closure, MemRegion mr) {  \
 758   oop_oop_iterate_bounded<nvs_to_bool(nv_suffix)>(obj, closure, mr);                                  \
 759 }
 760 
 761 #endif // SHARE_VM_OOPS_KLASS_HPP