1 /*
  2  * Copyright (c) 1997, 2022, Oracle and/or its affiliates. All rights reserved.
  3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  4  *
  5  * This code is free software; you can redistribute it and/or modify it
  6  * under the terms of the GNU General Public License version 2 only, as
  7  * published by the Free Software Foundation.
  8  *
  9  * This code is distributed in the hope that it will be useful, but WITHOUT
 10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 12  * version 2 for more details (a copy is included in the LICENSE file that
 13  * accompanied this code).
 14  *
 15  * You should have received a copy of the GNU General Public License version
 16  * 2 along with this work; if not, write to the Free Software Foundation,
 17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 18  *
 19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 20  * or visit www.oracle.com if you need additional information or have any
 21  * questions.
 22  *
 23  */
 24 
 25 #ifndef SHARE_OOPS_KLASS_HPP
 26 #define SHARE_OOPS_KLASS_HPP
 27 
 28 #include "memory/iterator.hpp"
 29 #include "memory/memRegion.hpp"
 30 #include "oops/markWord.hpp"
 31 #include "oops/metadata.hpp"
 32 #include "oops/oop.hpp"
 33 #include "oops/oopHandle.hpp"
 34 #include "utilities/accessFlags.hpp"
 35 #include "utilities/macros.hpp"
 36 #if INCLUDE_JFR
 37 #include "jfr/support/jfrTraceIdExtension.hpp"
 38 #endif
 39 
 40 // Klass Kinds for all subclasses of Klass
 41 enum KlassKind {
 42   InstanceKlassKind,
 43   InlineKlassKind,
 44   InstanceRefKlassKind,
 45   InstanceMirrorKlassKind,
 46   InstanceClassLoaderKlassKind,
 47   InstanceStackChunkKlassKind,
 48   TypeArrayKlassKind,
 49   FlatArrayKlassKind,
 50   ObjArrayKlassKind
 51 };
 52 
 53 const uint KLASS_KIND_COUNT = ObjArrayKlassKind + 1;
 54 
 55 //
 56 // A Klass provides:
 57 //  1: language level class object (method dictionary etc.)
 58 //  2: provide vm dispatch behavior for the object
 59 // Both functions are combined into one C++ class.
 60 
 61 // One reason for the oop/klass dichotomy in the implementation is
 62 // that we don't want a C++ vtbl pointer in every object.  Thus,
 63 // normal oops don't have any virtual functions.  Instead, they
 64 // forward all "virtual" functions to their klass, which does have
 65 // a vtbl and does the C++ dispatch depending on the object's
 66 // actual type.  (See oop.inline.hpp for some of the forwarding code.)
 67 // ALL FUNCTIONS IMPLEMENTING THIS DISPATCH ARE PREFIXED WITH "oop_"!
 68 
 69 // Forward declarations.
 70 template <class T> class Array;
 71 template <class T> class GrowableArray;
 72 class ClassLoaderData;
 73 class fieldDescriptor;
 74 class klassVtable;
 75 class ModuleEntry;
 76 class PackageEntry;
 77 class ParCompactionManager;
 78 class PSPromotionManager;
 79 class vtableEntry;
 80 
 81 class Klass : public Metadata {
 82   friend class VMStructs;
 83   friend class JVMCIVMStructs;
 84  protected:
 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, 0xA0 if value types
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   int _vtable_len;              // vtable length. This field may be read very often when we
163                                 // have lots of itable dispatches (e.g., lambdas and streams).
164                                 // Keep it away from the beginning of a Klass to avoid cacheline
165                                 // contention that may happen when a nearby object is modified.
166   AccessFlags _access_flags;    // Access flags. The class/interface distinction is stored here.
167 
168   JFR_ONLY(DEFINE_TRACE_ID_FIELD;)
169 
170   markWord _prototype_header;  // inline type and inline array mark patterns
171 private:
172   // This is an index into FileMapHeader::_shared_path_table[], to
173   // associate this class with the JAR file where it's loaded from during
174   // dump time. If a class is not loaded from the shared archive, this field is
175   // -1.
176   jshort _shared_class_path_index;
177 
178 #if INCLUDE_CDS
179   // Various attributes for shared classes. Should be zero for a non-shared class.
180   u2     _shared_class_flags;
181   enum CDSSharedClassFlags {
182     _archived_lambda_proxy_is_available    = 1 << 1,
183     _has_value_based_class_annotation      = 1 << 2,
184     _verified_at_dump_time                 = 1 << 3,
185     _has_archived_enum_objs                = 1 << 4,
186     // This class was not loaded from a classfile in the module image
187     // or classpath.
188     _is_generated_shared_class             = 1 << 5
189   };
190 #endif
191 
192   CDS_JAVA_HEAP_ONLY(int _archived_mirror_index;)
193 
194 protected:
195 
196   // Constructor
197   Klass(KlassKind kind);
198   Klass() : _kind(KlassKind(-1)) { assert(DumpSharedSpaces || UseSharedSpaces, "only for cds"); }
199 
200   void* operator new(size_t size, ClassLoaderData* loader_data, size_t word_size, TRAPS) throw();
201 
202  public:
203   int kind() { return _kind; }
204 
205   enum class DefaultsLookupMode { find, skip };
206   enum class OverpassLookupMode { find, skip };
207   enum class StaticLookupMode   { find, skip };
208   enum class PrivateLookupMode  { find, skip };
209 
210   virtual bool is_klass() const { return true; }
211 
212   // super() cannot be InstanceKlass* -- Java arrays are covariant, and _super is used
213   // to implement that. NB: the _super of "[Ljava/lang/Integer;" is "[Ljava/lang/Number;"
214   // If this is not what your code expects, you're probably looking for Klass::java_super().
215   Klass* super() const               { return _super; }
216   void set_super(Klass* k)           { _super = k; }
217 
218   // initializes _super link, _primary_supers & _secondary_supers arrays
219   void initialize_supers(Klass* k, Array<InstanceKlass*>* transitive_interfaces, TRAPS);
220 
221   // klass-specific helper for initializing _secondary_supers
222   virtual GrowableArray<Klass*>* compute_secondary_supers(int num_extra_slots,
223                                                           Array<InstanceKlass*>* transitive_interfaces);
224 
225   // java_super is the Java-level super type as specified by Class.getSuperClass.
226   virtual InstanceKlass* java_super() const  { return NULL; }
227 
228   juint    super_check_offset() const  { return _super_check_offset; }
229   void set_super_check_offset(juint o) { _super_check_offset = o; }
230 
231   Klass* secondary_super_cache() const     { return _secondary_super_cache; }
232   void set_secondary_super_cache(Klass* k) { _secondary_super_cache = k; }
233 
234   Array<Klass*>* secondary_supers() const { return _secondary_supers; }
235   void set_secondary_supers(Array<Klass*>* k) { _secondary_supers = k; }
236 
237   // Return the element of the _super chain of the given depth.
238   // If there is no such element, return either NULL or this.
239   Klass* primary_super_of_depth(juint i) const {
240     assert(i < primary_super_limit(), "oob");
241     Klass* super = _primary_supers[i];
242     assert(super == NULL || super->super_depth() == i, "correct display");
243     return super;
244   }
245 
246   // Can this klass be a primary super?  False for interfaces and arrays of
247   // interfaces.  False also for arrays or classes with long super chains.
248   bool can_be_primary_super() const {
249     const juint secondary_offset = in_bytes(secondary_super_cache_offset());
250     return super_check_offset() != secondary_offset;
251   }
252   virtual bool can_be_primary_super_slow() const;
253 
254   // Returns number of primary supers; may be a number in the inclusive range [0, primary_super_limit].
255   juint super_depth() const {
256     if (!can_be_primary_super()) {
257       return primary_super_limit();
258     } else {
259       juint d = (super_check_offset() - in_bytes(primary_supers_offset())) / sizeof(Klass*);
260       assert(d < primary_super_limit(), "oob");
261       assert(_primary_supers[d] == this, "proper init");
262       return d;
263     }
264   }
265 
266   // java mirror
267   oop java_mirror() const;
268   oop java_mirror_no_keepalive() const;
269   void set_java_mirror(Handle m);
270 
271   oop archived_java_mirror() NOT_CDS_JAVA_HEAP_RETURN_(NULL);
272   void set_archived_java_mirror(oop m) NOT_CDS_JAVA_HEAP_RETURN;
273 
274   // Temporary mirror switch used by RedefineClasses
275   void replace_java_mirror(oop mirror);
276 
277   // Set java mirror OopHandle to NULL for CDS
278   // This leaves the OopHandle in the CLD, but that's ok, you can't release them.
279   void clear_java_mirror_handle() { _java_mirror = OopHandle(); }
280 
281   // modifier flags
282   jint modifier_flags() const          { return _modifier_flags; }
283   void set_modifier_flags(jint flags)  { _modifier_flags = flags; }
284 
285   // size helper
286   int layout_helper() const            { return _layout_helper; }
287   void set_layout_helper(int lh)       { _layout_helper = lh; }
288 
289   // Note: for instances layout_helper() may include padding.
290   // Use InstanceKlass::contains_field_offset to classify field offsets.
291 
292   // sub/superklass links
293   Klass* subklass(bool log = false) const;
294   Klass* next_sibling(bool log = false) const;
295 
296   InstanceKlass* superklass() const;
297   void append_to_sibling_list();           // add newly created receiver to superklass' subklass list
298 
299   void set_next_link(Klass* k) { _next_link = k; }
300   Klass* next_link() const { return _next_link; }   // The next klass defined by the class loader.
301   Klass** next_link_addr() { return &_next_link; }
302 
303   // class loader data
304   ClassLoaderData* class_loader_data() const               { return _class_loader_data; }
305   void set_class_loader_data(ClassLoaderData* loader_data) {  _class_loader_data = loader_data; }
306 
307   int shared_classpath_index() const   {
308     return _shared_class_path_index;
309   };
310 
311   void set_shared_classpath_index(int index) {
312     _shared_class_path_index = index;
313   };
314 
315   bool has_archived_mirror_index() const {
316     CDS_JAVA_HEAP_ONLY(return _archived_mirror_index >= 0;)
317     NOT_CDS_JAVA_HEAP(return false);
318   }
319 
320   void clear_archived_mirror_index() NOT_CDS_JAVA_HEAP_RETURN;
321 
322   void set_lambda_proxy_is_available() {
323     CDS_ONLY(_shared_class_flags |= _archived_lambda_proxy_is_available;)
324   }
325   void clear_lambda_proxy_is_available() {
326     CDS_ONLY(_shared_class_flags &= ~_archived_lambda_proxy_is_available;)
327   }
328   bool lambda_proxy_is_available() const {
329     CDS_ONLY(return (_shared_class_flags & _archived_lambda_proxy_is_available) != 0;)
330     NOT_CDS(return false;)
331   }
332 
333   void set_has_value_based_class_annotation() {
334     CDS_ONLY(_shared_class_flags |= _has_value_based_class_annotation;)
335   }
336   void clear_has_value_based_class_annotation() {
337     CDS_ONLY(_shared_class_flags &= ~_has_value_based_class_annotation;)
338   }
339   bool has_value_based_class_annotation() const {
340     CDS_ONLY(return (_shared_class_flags & _has_value_based_class_annotation) != 0;)
341     NOT_CDS(return false;)
342   }
343 
344   void set_verified_at_dump_time() {
345     CDS_ONLY(_shared_class_flags |= _verified_at_dump_time;)
346   }
347   bool verified_at_dump_time() const {
348     CDS_ONLY(return (_shared_class_flags & _verified_at_dump_time) != 0;)
349     NOT_CDS(return false;)
350   }
351 
352   void set_has_archived_enum_objs() {
353     CDS_ONLY(_shared_class_flags |= _has_archived_enum_objs;)
354   }
355   bool has_archived_enum_objs() const {
356     CDS_ONLY(return (_shared_class_flags & _has_archived_enum_objs) != 0;)
357     NOT_CDS(return false;)
358   }
359 
360   void set_is_generated_shared_class() {
361     CDS_ONLY(_shared_class_flags |= _is_generated_shared_class;)
362   }
363   bool is_generated_shared_class() const {
364     CDS_ONLY(return (_shared_class_flags & _is_generated_shared_class) != 0;)
365     NOT_CDS(return false;)
366   }
367 
368   // Obtain the module or package for this class
369   virtual ModuleEntry* module() const = 0;
370   virtual PackageEntry* package() const = 0;
371 
372  protected:                                // internal accessors
373   void     set_subklass(Klass* s);
374   void     set_next_sibling(Klass* s);
375 
376  public:
377 
378   // Compiler support
379   static ByteSize super_offset()                 { return in_ByteSize(offset_of(Klass, _super)); }
380   static ByteSize super_check_offset_offset()    { return in_ByteSize(offset_of(Klass, _super_check_offset)); }
381   static ByteSize primary_supers_offset()        { return in_ByteSize(offset_of(Klass, _primary_supers)); }
382   static ByteSize secondary_super_cache_offset() { return in_ByteSize(offset_of(Klass, _secondary_super_cache)); }
383   static ByteSize secondary_supers_offset()      { return in_ByteSize(offset_of(Klass, _secondary_supers)); }
384   static ByteSize java_mirror_offset()           { return in_ByteSize(offset_of(Klass, _java_mirror)); }
385   static ByteSize class_loader_data_offset()     { return in_ByteSize(offset_of(Klass, _class_loader_data)); }
386   static ByteSize modifier_flags_offset()        { return in_ByteSize(offset_of(Klass, _modifier_flags)); }
387   static ByteSize layout_helper_offset()         { return in_ByteSize(offset_of(Klass, _layout_helper)); }
388   static ByteSize access_flags_offset()          { return in_ByteSize(offset_of(Klass, _access_flags)); }
389 
390   // Unpacking layout_helper:
391   static const int _lh_neutral_value           = 0;  // neutral non-array non-instance value
392   static const int _lh_instance_slow_path_bit  = 0x01;
393   static const int _lh_log2_element_size_shift = BitsPerByte*0;
394   static const int _lh_log2_element_size_mask  = BitsPerLong-1;
395   static const int _lh_element_type_shift      = BitsPerByte*1;
396   static const int _lh_element_type_mask       = right_n_bits(BitsPerByte);  // shifted mask
397   static const int _lh_header_size_shift       = BitsPerByte*2;
398   static const int _lh_header_size_mask        = right_n_bits(BitsPerByte);  // shifted mask
399   static const int _lh_array_tag_bits          = 3;
400   static const int _lh_array_tag_shift         = BitsPerInt - _lh_array_tag_bits;
401 
402   static const unsigned int _lh_array_tag_type_value = 0Xfffffffc;
403   static const unsigned int _lh_array_tag_vt_value   = 0Xfffffffd;
404   static const unsigned int _lh_array_tag_obj_value  = 0Xfffffffe;
405 
406   // null-free array flag bit under the array tag bits, shift one more to get array tag value
407   static const int _lh_null_free_shift = _lh_array_tag_shift - 1;
408   static const int _lh_null_free_mask  = 1;
409 
410   static const jint _lh_array_tag_flat_value_bit_inplace = (jint) (1 << _lh_array_tag_shift);
411   static const jint _lh_null_free_array_bit_inplace = (jint) (_lh_null_free_mask << _lh_null_free_shift);
412 
413   static int layout_helper_size_in_bytes(jint lh) {
414     assert(lh > (jint)_lh_neutral_value, "must be instance");
415     return (int) lh & ~_lh_instance_slow_path_bit;
416   }
417   static bool layout_helper_needs_slow_path(jint lh) {
418     assert(lh > (jint)_lh_neutral_value, "must be instance");
419     return (lh & _lh_instance_slow_path_bit) != 0;
420   }
421   static bool layout_helper_is_instance(jint lh) {
422     return (jint)lh > (jint)_lh_neutral_value;
423   }
424   static bool layout_helper_is_array(jint lh) {
425     return (jint)lh < (jint)_lh_neutral_value;
426   }
427   static bool layout_helper_is_typeArray(jint lh) {
428     return (juint) _lh_array_tag_type_value == (juint)(lh >> _lh_array_tag_shift);
429   }
430   static bool layout_helper_is_objArray(jint lh) {
431     return (juint)_lh_array_tag_obj_value == (juint)(lh >> _lh_array_tag_shift);
432   }
433   static bool layout_helper_is_flatArray(jint lh) {
434     return (juint)_lh_array_tag_vt_value == (juint)(lh >> _lh_array_tag_shift);
435   }
436   static bool layout_helper_is_null_free(jint lh) {
437     assert(layout_helper_is_flatArray(lh) || layout_helper_is_objArray(lh), "must be array of inline types");
438     return ((lh >> _lh_null_free_shift) & _lh_null_free_mask);
439   }
440   static jint layout_helper_set_null_free(jint lh) {
441     lh |= (_lh_null_free_mask << _lh_null_free_shift);
442     assert(layout_helper_is_null_free(lh), "Bad encoding");
443     return lh;
444   }
445   static int layout_helper_header_size(jint lh) {
446     assert(lh < (jint)_lh_neutral_value, "must be array");
447     int hsize = (lh >> _lh_header_size_shift) & _lh_header_size_mask;
448     assert(hsize > 0 && hsize < (int)sizeof(oopDesc)*3, "sanity");
449     return hsize;
450   }
451   static BasicType layout_helper_element_type(jint lh) {
452     assert(lh < (jint)_lh_neutral_value, "must be array");
453     int btvalue = (lh >> _lh_element_type_shift) & _lh_element_type_mask;
454     assert((btvalue >= T_BOOLEAN && btvalue <= T_OBJECT) || btvalue == T_PRIMITIVE_OBJECT, "sanity");
455     return (BasicType) btvalue;
456   }
457 
458   // Want a pattern to quickly diff against layout header in register
459   // find something less clever!
460   static int layout_helper_boolean_diffbit() {
461     jint zlh = array_layout_helper(T_BOOLEAN);
462     jint blh = array_layout_helper(T_BYTE);
463     assert(zlh != blh, "array layout helpers must differ");
464     int diffbit = 1;
465     while ((diffbit & (zlh ^ blh)) == 0 && (diffbit & zlh) == 0) {
466       diffbit <<= 1;
467       assert(diffbit != 0, "make sure T_BOOLEAN has a different bit than T_BYTE");
468     }
469     return diffbit;
470   }
471 
472   static int layout_helper_log2_element_size(jint lh) {
473     assert(lh < (jint)_lh_neutral_value, "must be array");
474     int l2esz = (lh >> _lh_log2_element_size_shift) & _lh_log2_element_size_mask;
475     assert(layout_helper_element_type(lh) == T_PRIMITIVE_OBJECT || l2esz <= LogBytesPerLong,
476            "sanity. l2esz: 0x%x for lh: 0x%x", (uint)l2esz, (uint)lh);
477     return l2esz;
478   }
479   static jint array_layout_helper(jint tag, bool null_free, int hsize, BasicType etype, int log2_esize) {
480     return (tag        << _lh_array_tag_shift)
481       |    ((null_free ? 1 : 0) <<  _lh_null_free_shift)
482       |    (hsize      << _lh_header_size_shift)
483       |    ((int)etype << _lh_element_type_shift)
484       |    (log2_esize << _lh_log2_element_size_shift);
485   }
486   static jint instance_layout_helper(jint size, bool slow_path_flag) {
487     return (size << LogBytesPerWord)
488       |    (slow_path_flag ? _lh_instance_slow_path_bit : 0);
489   }
490   static int layout_helper_to_size_helper(jint lh) {
491     assert(lh > (jint)_lh_neutral_value, "must be instance");
492     // Note that the following expression discards _lh_instance_slow_path_bit.
493     return lh >> LogBytesPerWord;
494   }
495   // Out-of-line version computes everything based on the etype:
496   static jint array_layout_helper(BasicType etype);
497 
498   // What is the maximum number of primary superclasses any klass can have?
499   static juint primary_super_limit()         { return _primary_super_limit; }
500 
501   // vtables
502   klassVtable vtable() const;
503   int vtable_length() const { return _vtable_len; }
504 
505   // subclass check
506   bool is_subclass_of(const Klass* k) const;
507   // subtype check: true if is_subclass_of, or if k is interface and receiver implements it
508   bool is_subtype_of(Klass* k) const {
509     juint    off = k->super_check_offset();
510     Klass* sup = *(Klass**)( (address)this + off );
511     const juint secondary_offset = in_bytes(secondary_super_cache_offset());
512     if (sup == k) {
513       return true;
514     } else if (off != secondary_offset) {
515       return false;
516     } else {
517       return search_secondary_supers(k);
518     }
519   }
520 
521   bool search_secondary_supers(Klass* k) const;
522 
523   // Find LCA in class hierarchy
524   Klass *LCA( Klass *k );
525 
526   // Check whether reflection/jni/jvm code is allowed to instantiate this class;
527   // if not, throw either an Error or an Exception.
528   virtual void check_valid_for_instantiation(bool throwError, TRAPS);
529 
530   // array copying
531   virtual void  copy_array(arrayOop s, int src_pos, arrayOop d, int dst_pos, int length, TRAPS);
532 
533   // tells if the class should be initialized
534   virtual bool should_be_initialized() const    { return false; }
535   // initializes the klass
536   virtual void initialize(TRAPS);
537   virtual Klass* find_field(Symbol* name, Symbol* signature, fieldDescriptor* fd) const;
538   virtual Method* uncached_lookup_method(const Symbol* name, const Symbol* signature,
539                                          OverpassLookupMode overpass_mode,
540                                          PrivateLookupMode = PrivateLookupMode::find) const;
541  public:
542   Method* lookup_method(const Symbol* name, const Symbol* signature) const {
543     return uncached_lookup_method(name, signature, OverpassLookupMode::find);
544   }
545 
546   // array class with specific rank
547   virtual Klass* array_klass(int rank, TRAPS) = 0;
548 
549   // array class with this klass as element type
550   virtual Klass* array_klass(TRAPS) = 0;
551 
552   // These will return NULL instead of allocating on the heap:
553   virtual Klass* array_klass_or_null(int rank) = 0;
554   virtual Klass* array_klass_or_null() = 0;
555 
556   virtual oop protection_domain() const = 0;
557 
558   oop class_loader() const;
559 
560   inline oop klass_holder() const;
561 
562  protected:
563 
564   // Error handling when length > max_length or length < 0
565   static void check_array_allocation_length(int length, int max_length, TRAPS);
566 
567   void set_vtable_length(int len) { _vtable_len= len; }
568 
569   vtableEntry* start_of_vtable() const;
570 #if INCLUDE_CDS
571   void restore_unshareable_info(ClassLoaderData* loader_data, Handle protection_domain, TRAPS);
572 #endif
573  public:
574   Method* method_at_vtable(int index);
575 
576   static ByteSize vtable_start_offset();
577   static ByteSize vtable_length_offset() {
578     return byte_offset_of(Klass, _vtable_len);
579   }
580 
581 #if INCLUDE_CDS
582   // CDS support - remove and restore oops from metadata. Oops are not shared.
583   virtual void remove_unshareable_info();
584   virtual void remove_java_mirror();
585 
586   bool is_unshareable_info_restored() const {
587     assert(is_shared(), "use this for shared classes only");
588     if (has_archived_mirror_index()) {
589       // _java_mirror is not a valid OopHandle but rather an encoded reference in the shared heap
590       return false;
591     } else if (_java_mirror.ptr_raw() == NULL) {
592       return false;
593     } else {
594       return true;
595     }
596   }
597 #endif // INCLUDE_CDS
598 
599  public:
600   // ALL FUNCTIONS BELOW THIS POINT ARE DISPATCHED FROM AN OOP
601   // These functions describe behavior for the oop not the KLASS.
602 
603   // actual oop size of obj in memory in word size.
604   virtual size_t oop_size(oop obj) const = 0;
605 
606   // Size of klass in word size.
607   virtual int size() const = 0;
608 
609   // Returns the Java name for a class (Resource allocated)
610   // For arrays, this returns the name of the element with a leading '['.
611   // For classes, this returns the name with the package separators
612   //     turned into '.'s.
613   const char* external_name() const;
614   // Returns the name for a class (Resource allocated) as the class
615   // would appear in a signature.
616   // For arrays, this returns the name of the element with a leading '['.
617   // For classes, this returns the name with a leading 'L' and a trailing ';'
618   //     and the package separators as '/'.
619   virtual const char* signature_name() const;
620 
621   const char* joint_in_module_of_loader(const Klass* class2, bool include_parent_loader = false) const;
622   const char* class_in_module_of_loader(bool use_are = false, bool include_parent_loader = false) const;
623 
624   // Returns "interface", "abstract class" or "class".
625   const char* external_kind() const;
626 
627   // type testing operations
628 #ifdef ASSERT
629  protected:
630   virtual bool is_instance_klass_slow()     const { return false; }
631   virtual bool is_array_klass_slow()        const { return false; }
632   virtual bool is_objArray_klass_slow()     const { return false; }
633   virtual bool is_typeArray_klass_slow()    const { return false; }
634   virtual bool is_flatArray_klass_slow()    const { return false; }
635 #endif // ASSERT
636   // current implementation uses this method even in non debug builds
637   virtual bool is_inline_klass_slow()       const { return false; }
638  public:
639 
640   // Fast non-virtual versions
641   #ifndef ASSERT
642   #define assert_same_query(xval, xcheck) xval
643   #else
644  private:
645   static bool assert_same_query(bool xval, bool xslow) {
646     assert(xval == xslow, "slow and fast queries agree");
647     return xval;
648   }
649  public:
650   #endif
651 
652   bool is_instance_klass()              const { return assert_same_query(_kind <= InstanceStackChunkKlassKind, is_instance_klass_slow()); }
653   bool is_inline_klass()                const { return is_inline_klass_slow(); } //temporary hack
654   // Other is anything that is not one of the more specialized kinds of InstanceKlass.
655   bool is_other_instance_klass()        const { return _kind <= InlineKlassKind; }
656   bool is_reference_instance_klass()    const { return _kind == InstanceRefKlassKind; }
657   bool is_mirror_instance_klass()       const { return _kind == InstanceMirrorKlassKind; }
658   bool is_class_loader_instance_klass() const { return _kind == InstanceClassLoaderKlassKind; }
659   bool is_array_klass()                 const { return assert_same_query( _kind >= TypeArrayKlassKind, is_array_klass_slow()); }
660   bool is_stack_chunk_instance_klass()  const { return _kind == InstanceStackChunkKlassKind; }
661   bool is_flatArray_klass()             const { return assert_same_query( _kind == FlatArrayKlassKind, is_flatArray_klass_slow()); }
662   bool is_objArray_klass()              const { return assert_same_query( _kind == ObjArrayKlassKind,  is_objArray_klass_slow()); }
663   bool is_typeArray_klass()             const { return assert_same_query( _kind == TypeArrayKlassKind, is_typeArray_klass_slow()); }
664   #undef assert_same_query
665 
666   inline bool is_null_free_array_klass()      const { return layout_helper_is_null_free(layout_helper()); }
667 
668   // Access flags
669   AccessFlags access_flags() const         { return _access_flags;  }
670   void set_access_flags(AccessFlags flags) { _access_flags = flags; }
671 
672   bool is_public() const                { return _access_flags.is_public(); }
673   bool is_final() const                 { return _access_flags.is_final(); }
674   bool is_interface() const             { return _access_flags.is_interface(); }
675   bool is_abstract() const              { return _access_flags.is_abstract(); }
676   bool is_synthetic() const             { return _access_flags.is_synthetic(); }
677   bool is_value_class() const           { return _access_flags.is_value_class(); }
678   bool is_identity_class() const        { return _access_flags.is_identity_class(); }
679   void set_is_synthetic()               { _access_flags.set_is_synthetic(); }
680   bool has_finalizer() const            { return _access_flags.has_finalizer(); }
681   bool has_final_method() const         { return _access_flags.has_final_method(); }
682   void set_has_finalizer()              { _access_flags.set_has_finalizer(); }
683   void set_has_final_method()           { _access_flags.set_has_final_method(); }
684   bool has_vanilla_constructor() const  { return _access_flags.has_vanilla_constructor(); }
685   void set_has_vanilla_constructor()    { _access_flags.set_has_vanilla_constructor(); }
686   bool has_miranda_methods () const     { return access_flags().has_miranda_methods(); }
687   void set_has_miranda_methods()        { _access_flags.set_has_miranda_methods(); }
688   bool is_shared() const                { return access_flags().is_shared_class(); } // shadows MetaspaceObj::is_shared)()
689   void set_is_shared()                  { _access_flags.set_is_shared_class(); }
690   bool is_hidden() const                { return access_flags().is_hidden_class(); }
691   void set_is_hidden()                  { _access_flags.set_is_hidden_class(); }
692   bool is_value_based()                 { return _access_flags.is_value_based_class(); }
693   void set_is_value_based()             { _access_flags.set_is_value_based_class(); }
694 
695   inline bool is_non_strong_hidden() const;
696 
697   bool is_cloneable() const;
698   void set_is_cloneable();
699 
700   // inline types and inline type array patterns
701   markWord prototype_header() const {
702     return _prototype_header;
703   }
704   static inline markWord default_prototype_header(Klass* k) {
705     return (k == NULL) ? markWord::prototype() : k->prototype_header();
706   }
707 
708   inline void set_prototype_header(markWord header);
709   static ByteSize prototype_header_offset() { return in_ByteSize(offset_of(Klass, _prototype_header)); }
710 
711   JFR_ONLY(DEFINE_TRACE_ID_METHODS;)
712 
713   virtual void metaspace_pointers_do(MetaspaceClosure* iter);
714   virtual MetaspaceObj::Type type() const { return ClassType; }
715 
716   inline bool is_loader_alive() const;
717 
718   void clean_subklass();
719 
720   static void clean_weak_klass_links(bool unloading_occurred, bool clean_alive_klasses = true);
721   static void clean_subklass_tree() {
722     clean_weak_klass_links(/*unloading_occurred*/ true , /* clean_alive_klasses */ false);
723   }
724 
725   // Return self, except for abstract classes with exactly 1
726   // implementor.  Then return the 1 concrete implementation.
727   Klass *up_cast_abstract();
728 
729   // klass name
730   Symbol* name() const                   { return _name; }
731   void set_name(Symbol* n);
732 
733   virtual void release_C_heap_structures(bool release_constant_pool = true);
734 
735  public:
736   virtual jint compute_modifier_flags() const = 0;
737 
738   // JVMTI support
739   virtual jint jvmti_class_status() const;
740 
741   // Printing
742   virtual void print_on(outputStream* st) const;
743 
744   virtual void oop_print_value_on(oop obj, outputStream* st);
745   virtual void oop_print_on      (oop obj, outputStream* st);
746 
747   virtual const char* internal_name() const = 0;
748 
749   // Verification
750   virtual void verify_on(outputStream* st);
751   void verify() { verify_on(tty); }
752 
753 #ifndef PRODUCT
754   bool verify_vtable_index(int index);
755 #endif
756 
757   virtual void oop_verify_on(oop obj, outputStream* st);
758 
759   // for error reporting
760   static bool is_valid(Klass* k);
761 };
762 
763 #endif // SHARE_OOPS_KLASS_HPP