1 /*
2 * Copyright (c) 1997, 2025, 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 *
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23 */
24
25 #ifndef SHARE_OOPS_KLASS_HPP
26 #define SHARE_OOPS_KLASS_HPP
27
28 #include "oops/klassFlags.hpp"
29 #include "oops/markWord.hpp"
30 #include "oops/metadata.hpp"
31 #include "oops/oop.hpp"
32 #include "oops/oopHandle.hpp"
33 #include "utilities/accessFlags.hpp"
34 #include "utilities/macros.hpp"
35 #if INCLUDE_JFR
36 #include "jfr/support/jfrTraceIdExtension.hpp"
37 #endif
38
39 //
40 // A Klass provides:
41 // 1: language level class object (method dictionary etc.)
42 // 2: provide vm dispatch behavior for the object
43 // Both functions are combined into one C++ class.
44
45 // One reason for the oop/klass dichotomy in the implementation is
46 // that we don't want a C++ vtbl pointer in every object. Thus,
47 // normal oops don't have any virtual functions. Instead, they
48 // forward all "virtual" functions to their klass, which does have
49 // a vtbl and does the C++ dispatch depending on the object's
50 // actual type. (See oop.inline.hpp for some of the forwarding code.)
51 // ALL FUNCTIONS IMPLEMENTING THIS DISPATCH ARE PREFIXED WITH "oop_"!
52
53 // Forward declarations.
54 template <class T> class Array;
55 template <class T> class GrowableArray;
56 class ClassLoaderData;
57 class fieldDescriptor;
58 class klassVtable;
59 class ModuleEntry;
60 class PackageEntry;
61 class vtableEntry;
62
63 class Klass : public Metadata {
64
65 friend class VMStructs;
66 friend class JVMCIVMStructs;
67 public:
68 // Klass Kinds for all subclasses of Klass
69 enum KlassKind : u2 {
70 InstanceKlassKind,
71 InstanceRefKlassKind,
72 InstanceMirrorKlassKind,
73 InstanceClassLoaderKlassKind,
74 InstanceStackChunkKlassKind,
75 TypeArrayKlassKind,
76 ObjArrayKlassKind,
77 UnknownKlassKind
78 };
79
80 static const uint KLASS_KIND_COUNT = ObjArrayKlassKind + 1;
81 protected:
82
83 // If you add a new field that points to any metaspace object, you
84 // must add this field to Klass::metaspace_pointers_do().
85
86 // note: put frequently-used fields together at start of klass structure
87 // for better cache behavior (may not make much of a difference but sure won't hurt)
88 enum { _primary_super_limit = 8 };
89
90 // The "layout helper" is a combined descriptor of object layout.
91 // For klasses which are neither instance nor array, the value is zero.
92 //
93 // For instances, layout helper is a positive number, the instance size.
94 // This size is already passed through align_object_size and scaled to bytes.
95 // The low order bit is set if instances of this class cannot be
96 // allocated using the fastpath.
97 //
98 // For arrays, layout helper is a negative number, containing four
99 // distinct bytes, as follows:
100 // MSB:[tag, hsz, ebt, log2(esz)]:LSB
101 // where:
102 // tag is 0x80 if the elements are oops, 0xC0 if non-oops
103 // hsz is array header size in bytes (i.e., offset of first element)
104 // ebt is the BasicType of the elements
105 // esz is the element size in bytes
106 // This packed word is arranged so as to be quickly unpacked by the
107 // various fast paths that use the various subfields.
108 //
109 // The esz bits can be used directly by a SLL instruction, without masking.
110 //
111 // Note that the array-kind tag looks like 0x00 for instance klasses,
112 // since their length in bytes is always less than 24Mb.
113 //
114 // Final note: This comes first, immediately after C++ vtable,
115 // because it is frequently queried.
116 jint _layout_helper;
117
118 // Klass kind used to resolve the runtime type of the instance.
119 // - Used to implement devirtualized oop closure dispatching.
120 // - Various type checking in the JVM
121 const KlassKind _kind;
122
123 AccessFlags _access_flags; // Access flags. The class/interface distinction is stored here.
124 // Some flags created by the JVM, not in the class file itself,
125 // are in _misc_flags below.
126 // Processed access flags, for use by Class.getModifiers.
127 u2 _modifier_flags;
128
129 KlassFlags _misc_flags;
130
131 // The fields _super_check_offset, _secondary_super_cache, _secondary_supers
132 // and _primary_supers all help make fast subtype checks. See big discussion
133 // in doc/server_compiler/checktype.txt
134 //
135 // Where to look to observe a supertype (it is &_secondary_super_cache for
136 // secondary supers, else is &_primary_supers[depth()].
137 juint _super_check_offset;
138
139 // Class name. Instance classes: java/lang/String, etc. Array classes: [I,
140 // [Ljava/lang/String;, etc. Set to zero for all other kinds of classes.
141 Symbol* _name;
142
143 // Cache of last observed secondary supertype
144 Klass* _secondary_super_cache;
145 // Array of all secondary supertypes
146 Array<Klass*>* _secondary_supers;
147 // Ordered list of all primary supertypes
148 Klass* _primary_supers[_primary_super_limit];
149 // java/lang/Class instance mirroring this class
150 OopHandle _java_mirror;
151 // Superclass
152 Klass* _super;
153 // First subclass (null if none); _subklass->next_sibling() is next one
154 Klass* volatile _subklass;
155 // Sibling link (or null); links all subklasses of a klass
156 Klass* volatile _next_sibling;
157
158 // All klasses loaded by a class loader are chained through these links
159 Klass* _next_link;
160
161 // The VM's representation of the ClassLoader used to load this class.
162 // Provide access the corresponding instance java.lang.ClassLoader.
163 ClassLoaderData* _class_loader_data;
164
165 markWord _prototype_header; // Used to initialize objects' header
166
167 // Bitmap and hash code used by hashed secondary supers.
168 uintx _secondary_supers_bitmap;
169 uint8_t _hash_slot;
170
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 s2 _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 _is_shared_class = 1 << 0, // shadows MetaspaceObj::is_shared
183 _archived_lambda_proxy_is_available = 1 << 1,
184 _has_value_based_class_annotation = 1 << 2,
185 _verified_at_dump_time = 1 << 3,
186 _has_archived_enum_objs = 1 << 4,
187 // This class was not loaded from a classfile in the module image
188 // or classpath.
189 _is_generated_shared_class = 1 << 5,
190 // archived mirror already initialized by AOT-cache assembly: no further need to call <clinit>
191 _has_aot_initialized_mirror = 1 << 6,
192 // If this class has been aot-inititalized, do we need to call its runtimeSetup()
193 // method during the production run?
194 _is_runtime_setup_required = 1 << 7,
195 };
196 #endif
197
198 int _vtable_len; // vtable length. This field may be read very often when we
199 // have lots of itable dispatches (e.g., lambdas and streams).
200 // Keep it away from the beginning of a Klass to avoid cacheline
201 // contention that may happen when a nearby object is modified.
202
203 CDS_JAVA_HEAP_ONLY(int _archived_mirror_index;)
204
205 public:
206
207 JFR_ONLY(DEFINE_TRACE_ID_FIELD;)
208
209 protected:
210
211 Klass(KlassKind kind);
212 Klass();
213
214 public:
215 int kind() { return _kind; }
216
217 enum class DefaultsLookupMode { find, skip };
218 enum class OverpassLookupMode { find, skip };
219 enum class StaticLookupMode { find, skip };
220 enum class PrivateLookupMode { find, skip };
221
222 virtual bool is_klass() const { return true; }
223
224 // super() cannot be InstanceKlass* -- Java arrays are covariant, and _super is used
225 // to implement that. NB: the _super of "[Ljava/lang/Integer;" is "[Ljava/lang/Number;"
226 // If this is not what your code expects, you're probably looking for Klass::java_super().
227 Klass* super() const { return _super; }
228 void set_super(Klass* k) { _super = k; }
229
230 // initializes _super link, _primary_supers & _secondary_supers arrays
231 void initialize_supers(Klass* k, Array<InstanceKlass*>* transitive_interfaces, TRAPS);
232
233 // klass-specific helper for initializing _secondary_supers
234 virtual GrowableArray<Klass*>* compute_secondary_supers(int num_extra_slots,
235 Array<InstanceKlass*>* transitive_interfaces);
236
237 // java_super is the Java-level super type as specified by Class.getSuperClass.
238 virtual InstanceKlass* java_super() const { return nullptr; }
239
240 juint super_check_offset() const { return _super_check_offset; }
241 void set_super_check_offset(juint o) { _super_check_offset = o; }
242
243 Klass* secondary_super_cache() const { return _secondary_super_cache; }
244 void set_secondary_super_cache(Klass* k) { _secondary_super_cache = k; }
245
246 Array<Klass*>* secondary_supers() const { return _secondary_supers; }
247 void set_secondary_supers(Array<Klass*>* k, uintx bitmap);
248
249 uint8_t hash_slot() const { return _hash_slot; }
250
251 // Return the element of the _super chain of the given depth.
252 // If there is no such element, return either null or this.
253 Klass* primary_super_of_depth(juint i) const {
254 assert(i < primary_super_limit(), "oob");
255 Klass* super = _primary_supers[i];
256 assert(super == nullptr || super->super_depth() == i, "correct display");
257 return super;
258 }
259
260 // Can this klass be a primary super? False for interfaces and arrays of
261 // interfaces. False also for arrays or classes with long super chains.
262 bool can_be_primary_super() const {
263 const juint secondary_offset = in_bytes(secondary_super_cache_offset());
264 return super_check_offset() != secondary_offset;
265 }
266 virtual bool can_be_primary_super_slow() const;
267
268 // Returns number of primary supers; may be a number in the inclusive range [0, primary_super_limit].
269 juint super_depth() const {
270 if (!can_be_primary_super()) {
271 return primary_super_limit();
272 } else {
273 juint d = (super_check_offset() - in_bytes(primary_supers_offset())) / sizeof(Klass*);
274 assert(d < primary_super_limit(), "oob");
275 assert(_primary_supers[d] == this, "proper init");
276 return d;
277 }
278 }
279
280 // java mirror
281 oop java_mirror() const;
282 oop java_mirror_no_keepalive() const;
283 void set_java_mirror(Handle m);
284
285 oop archived_java_mirror() NOT_CDS_JAVA_HEAP_RETURN_(nullptr);
286 void set_archived_java_mirror(int mirror_index) NOT_CDS_JAVA_HEAP_RETURN;
287
288 // Temporary mirror switch used by RedefineClasses
289 OopHandle java_mirror_handle() const { return _java_mirror; }
290 void swap_java_mirror_handle(OopHandle& mirror) { _java_mirror.swap(mirror); }
291
292 // Set java mirror OopHandle to null for CDS
293 // This leaves the OopHandle in the CLD, but that's ok, you can't release them.
294 void clear_java_mirror_handle() { _java_mirror = OopHandle(); }
295
296 // modifier flags
297 u2 modifier_flags() const { return _modifier_flags; }
298 void set_modifier_flags(u2 flags) { _modifier_flags = flags; }
299
300 // size helper
301 int layout_helper() const { return _layout_helper; }
302 void set_layout_helper(int lh) { _layout_helper = lh; }
303
304 // Note: for instances layout_helper() may include padding.
305 // Use InstanceKlass::contains_field_offset to classify field offsets.
306
307 // sub/superklass links
308 Klass* subklass(bool log = false) const;
309 Klass* next_sibling(bool log = false) const;
310
311 InstanceKlass* superklass() const;
312 void append_to_sibling_list(); // add newly created receiver to superklass' subklass list
313
314 void set_next_link(Klass* k) { _next_link = k; }
315 Klass* next_link() const { return _next_link; } // The next klass defined by the class loader.
316 Klass** next_link_addr() { return &_next_link; }
317
318 // class loader data
319 ClassLoaderData* class_loader_data() const { return _class_loader_data; }
320 void set_class_loader_data(ClassLoaderData* loader_data) { _class_loader_data = loader_data; }
321
322 s2 shared_classpath_index() const {
323 return _shared_class_path_index;
324 };
325
326 void set_shared_classpath_index(s2 index) {
327 _shared_class_path_index = index;
328 };
329
330 bool has_archived_mirror_index() const {
331 CDS_JAVA_HEAP_ONLY(return _archived_mirror_index >= 0;)
332 NOT_CDS_JAVA_HEAP(return false);
333 }
334
335 void clear_archived_mirror_index() NOT_CDS_JAVA_HEAP_RETURN;
336
337 void set_lambda_proxy_is_available() {
338 CDS_ONLY(_shared_class_flags |= _archived_lambda_proxy_is_available;)
339 }
340 void clear_lambda_proxy_is_available() {
341 CDS_ONLY(_shared_class_flags &= (u2)(~_archived_lambda_proxy_is_available);)
342 }
343 bool lambda_proxy_is_available() const {
344 CDS_ONLY(return (_shared_class_flags & _archived_lambda_proxy_is_available) != 0;)
345 NOT_CDS(return false;)
346 }
347
348 void set_has_value_based_class_annotation() {
349 CDS_ONLY(_shared_class_flags |= _has_value_based_class_annotation;)
350 }
351 void clear_has_value_based_class_annotation() {
352 CDS_ONLY(_shared_class_flags &= (u2)(~_has_value_based_class_annotation);)
353 }
354 bool has_value_based_class_annotation() const {
355 CDS_ONLY(return (_shared_class_flags & _has_value_based_class_annotation) != 0;)
356 NOT_CDS(return false;)
357 }
358
359 void set_verified_at_dump_time() {
360 CDS_ONLY(_shared_class_flags |= _verified_at_dump_time;)
361 }
362 bool verified_at_dump_time() const {
363 CDS_ONLY(return (_shared_class_flags & _verified_at_dump_time) != 0;)
364 NOT_CDS(return false;)
365 }
366
367 void set_has_archived_enum_objs() {
368 CDS_ONLY(_shared_class_flags |= _has_archived_enum_objs;)
369 }
370 bool has_archived_enum_objs() const {
371 CDS_ONLY(return (_shared_class_flags & _has_archived_enum_objs) != 0;)
372 NOT_CDS(return false;)
373 }
374
375 void set_is_generated_shared_class() {
376 CDS_ONLY(_shared_class_flags |= _is_generated_shared_class;)
377 }
378 bool is_generated_shared_class() const {
379 CDS_ONLY(return (_shared_class_flags & _is_generated_shared_class) != 0;)
380 NOT_CDS(return false;)
381 }
382
383 void set_has_aot_initialized_mirror() {
384 CDS_ONLY(_shared_class_flags |= _has_aot_initialized_mirror;)
385 }
386 bool has_aot_initialized_mirror() const {
387 CDS_ONLY(return (_shared_class_flags & _has_aot_initialized_mirror) != 0;)
388 NOT_CDS(return false;)
389 }
390
391 void set_is_runtime_setup_required() {
392 assert(has_aot_initialized_mirror(), "sanity");
393 CDS_ONLY(_shared_class_flags |= _is_runtime_setup_required;)
394 }
395 bool is_runtime_setup_required() const {
396 CDS_ONLY(return (_shared_class_flags & _is_runtime_setup_required) != 0;)
397 NOT_CDS(return false;)
398 }
399
400 bool is_shared() const { // shadows MetaspaceObj::is_shared)()
401 CDS_ONLY(return (_shared_class_flags & _is_shared_class) != 0;)
402 NOT_CDS(return false;)
403 }
404
405 void set_is_shared() {
406 CDS_ONLY(_shared_class_flags |= _is_shared_class;)
407 }
408
409 // Obtain the module or package for this class
410 virtual ModuleEntry* module() const = 0;
411 virtual PackageEntry* package() const = 0;
412
413 protected: // internal accessors
414 void set_subklass(Klass* s);
415 void set_next_sibling(Klass* s);
416
417 private:
418 static uint8_t compute_hash_slot(Symbol* s);
419 static void hash_insert(Klass* klass, GrowableArray<Klass*>* secondaries, uintx& bitmap);
420 static uintx hash_secondary_supers(Array<Klass*>* secondaries, bool rewrite);
421
422 bool search_secondary_supers(Klass* k) const;
423 bool lookup_secondary_supers_table(Klass *k) const;
424 bool linear_search_secondary_supers(const Klass* k) const;
425 bool fallback_search_secondary_supers(const Klass* k, int index, uintx rotated_bitmap) const;
426
427 public:
428 // Secondary supers table support
429 static Array<Klass*>* pack_secondary_supers(ClassLoaderData* loader_data,
430 GrowableArray<Klass*>* primaries,
431 GrowableArray<Klass*>* secondaries,
432 uintx& bitmap,
433 TRAPS);
434
435 static uintx compute_secondary_supers_bitmap(Array<Klass*>* secondary_supers);
436 static uint8_t compute_home_slot(Klass* k, uintx bitmap);
437
438 static constexpr int SECONDARY_SUPERS_TABLE_SIZE = sizeof(_secondary_supers_bitmap) * 8;
439 static constexpr int SECONDARY_SUPERS_TABLE_MASK = SECONDARY_SUPERS_TABLE_SIZE - 1;
440
441 static constexpr uintx SECONDARY_SUPERS_BITMAP_EMPTY = 0;
442 static constexpr uintx SECONDARY_SUPERS_BITMAP_FULL = ~(uintx)0;
443
444 // Compiler support
445 static ByteSize super_offset() { return byte_offset_of(Klass, _super); }
446 static ByteSize super_check_offset_offset() { return byte_offset_of(Klass, _super_check_offset); }
447 static ByteSize primary_supers_offset() { return byte_offset_of(Klass, _primary_supers); }
448 static ByteSize secondary_super_cache_offset() { return byte_offset_of(Klass, _secondary_super_cache); }
449 static ByteSize secondary_supers_offset() { return byte_offset_of(Klass, _secondary_supers); }
450 static ByteSize java_mirror_offset() { return byte_offset_of(Klass, _java_mirror); }
451 static ByteSize class_loader_data_offset() { return byte_offset_of(Klass, _class_loader_data); }
452 static ByteSize modifier_flags_offset() { return byte_offset_of(Klass, _modifier_flags); }
453 static ByteSize layout_helper_offset() { return byte_offset_of(Klass, _layout_helper); }
454 static ByteSize access_flags_offset() { return byte_offset_of(Klass, _access_flags); }
455 #if INCLUDE_JVMCI
456 static ByteSize subklass_offset() { return byte_offset_of(Klass, _subklass); }
457 static ByteSize next_sibling_offset() { return byte_offset_of(Klass, _next_sibling); }
458 #endif
459 static ByteSize secondary_supers_bitmap_offset()
460 { return byte_offset_of(Klass, _secondary_supers_bitmap); }
461 static ByteSize hash_slot_offset() { return byte_offset_of(Klass, _hash_slot); }
462 static ByteSize misc_flags_offset() { return byte_offset_of(Klass, _misc_flags._flags); }
463
464 // Unpacking layout_helper:
465 static const int _lh_neutral_value = 0; // neutral non-array non-instance value
466 static const int _lh_instance_slow_path_bit = 0x01;
467 static const int _lh_log2_element_size_shift = BitsPerByte*0;
468 static const int _lh_log2_element_size_mask = BitsPerLong-1;
469 static const int _lh_element_type_shift = BitsPerByte*1;
470 static const int _lh_element_type_mask = right_n_bits(BitsPerByte); // shifted mask
471 static const int _lh_header_size_shift = BitsPerByte*2;
472 static const int _lh_header_size_mask = right_n_bits(BitsPerByte); // shifted mask
473 static const int _lh_array_tag_bits = 2;
474 static const int _lh_array_tag_shift = BitsPerInt - _lh_array_tag_bits;
475 static const int _lh_array_tag_obj_value = ~0x01; // 0x80000000 >> 30
476
477 static const unsigned int _lh_array_tag_type_value = 0Xffffffff; // ~0x00, // 0xC0000000 >> 30
478
479 static int layout_helper_size_in_bytes(jint lh) {
480 assert(lh > (jint)_lh_neutral_value, "must be instance");
481 return (int) lh & ~_lh_instance_slow_path_bit;
482 }
483 static bool layout_helper_needs_slow_path(jint lh) {
484 assert(lh > (jint)_lh_neutral_value, "must be instance");
485 return (lh & _lh_instance_slow_path_bit) != 0;
486 }
487 static bool layout_helper_is_instance(jint lh) {
488 return (jint)lh > (jint)_lh_neutral_value;
489 }
490 static bool layout_helper_is_array(jint lh) {
491 return (jint)lh < (jint)_lh_neutral_value;
492 }
493 static bool layout_helper_is_typeArray(jint lh) {
494 // _lh_array_tag_type_value == (lh >> _lh_array_tag_shift);
495 return (juint)lh >= (juint)(_lh_array_tag_type_value << _lh_array_tag_shift);
496 }
497 static bool layout_helper_is_objArray(jint lh) {
498 // _lh_array_tag_obj_value == (lh >> _lh_array_tag_shift);
499 return (jint)lh < (jint)(_lh_array_tag_type_value << _lh_array_tag_shift);
500 }
501 static int layout_helper_header_size(jint lh) {
502 assert(lh < (jint)_lh_neutral_value, "must be array");
503 int hsize = (lh >> _lh_header_size_shift) & _lh_header_size_mask;
504 assert(hsize > 0 && hsize < (int)sizeof(oopDesc)*3, "sanity");
505 return hsize;
506 }
507 static BasicType layout_helper_element_type(jint lh) {
508 assert(lh < (jint)_lh_neutral_value, "must be array");
509 int btvalue = (lh >> _lh_element_type_shift) & _lh_element_type_mask;
510 assert(btvalue >= T_BOOLEAN && btvalue <= T_OBJECT, "sanity");
511 return (BasicType) btvalue;
512 }
513
514 // Want a pattern to quickly diff against layout header in register
515 // find something less clever!
516 static int layout_helper_boolean_diffbit() {
517 jint zlh = array_layout_helper(T_BOOLEAN);
518 jint blh = array_layout_helper(T_BYTE);
519 assert(zlh != blh, "array layout helpers must differ");
520 int diffbit = 1;
521 while ((diffbit & (zlh ^ blh)) == 0 && (diffbit & zlh) == 0) {
522 diffbit <<= 1;
523 assert(diffbit != 0, "make sure T_BOOLEAN has a different bit than T_BYTE");
524 }
525 return diffbit;
526 }
527
528 static int layout_helper_log2_element_size(jint lh) {
529 assert(lh < (jint)_lh_neutral_value, "must be array");
530 int l2esz = (lh >> _lh_log2_element_size_shift) & _lh_log2_element_size_mask;
531 assert(l2esz <= LogBytesPerLong,
532 "sanity. l2esz: 0x%x for lh: 0x%x", (uint)l2esz, (uint)lh);
533 return l2esz;
534 }
535 static jint array_layout_helper(jint tag, int hsize, BasicType etype, int log2_esize) {
536 return (tag << _lh_array_tag_shift)
537 | (hsize << _lh_header_size_shift)
538 | ((int)etype << _lh_element_type_shift)
539 | (log2_esize << _lh_log2_element_size_shift);
540 }
541 static jint instance_layout_helper(jint size, bool slow_path_flag) {
542 return (size << LogBytesPerWord)
543 | (slow_path_flag ? _lh_instance_slow_path_bit : 0);
544 }
545 static int layout_helper_to_size_helper(jint lh) {
546 assert(lh > (jint)_lh_neutral_value, "must be instance");
547 // Note that the following expression discards _lh_instance_slow_path_bit.
548 return lh >> LogBytesPerWord;
549 }
550 // Out-of-line version computes everything based on the etype:
551 static jint array_layout_helper(BasicType etype);
552
553 // What is the maximum number of primary superclasses any klass can have?
554 static juint primary_super_limit() { return _primary_super_limit; }
555
556 // vtables
557 klassVtable vtable() const;
558 int vtable_length() const { return _vtable_len; }
559
560 // subclass check
561 bool is_subclass_of(const Klass* k) const;
562
563 // subtype check: true if is_subclass_of, or if k is interface and receiver implements it
564 bool is_subtype_of(Klass* k) const;
565
566 public:
567 // Find LCA in class hierarchy
568 Klass *LCA( Klass *k );
569
570 // Check whether reflection/jni/jvm code is allowed to instantiate this class;
571 // if not, throw either an Error or an Exception.
572 virtual void check_valid_for_instantiation(bool throwError, TRAPS);
573
574 // array copying
575 virtual void copy_array(arrayOop s, int src_pos, arrayOop d, int dst_pos, int length, TRAPS);
576
577 // tells if the class should be initialized
578 virtual bool should_be_initialized() const { return false; }
579 // initializes the klass
580 virtual void initialize(TRAPS);
581 virtual Klass* find_field(Symbol* name, Symbol* signature, fieldDescriptor* fd) const;
582 virtual Method* uncached_lookup_method(const Symbol* name, const Symbol* signature,
583 OverpassLookupMode overpass_mode,
584 PrivateLookupMode = PrivateLookupMode::find) const;
585 public:
586 Method* lookup_method(const Symbol* name, const Symbol* signature) const {
587 return uncached_lookup_method(name, signature, OverpassLookupMode::find);
588 }
589
590 // array class with specific rank
591 virtual ArrayKlass* array_klass(int rank, TRAPS) = 0;
592
593 // array class with this klass as element type
594 virtual ArrayKlass* array_klass(TRAPS) = 0;
595
596 // These will return null instead of allocating on the heap:
597 virtual ArrayKlass* array_klass_or_null(int rank) = 0;
598 virtual ArrayKlass* array_klass_or_null() = 0;
599
600 virtual oop protection_domain() const = 0;
601
602 oop class_loader() const;
603
604 inline oop klass_holder() const;
605
606 inline void keep_alive() const;
607
608 protected:
609
610 // Error handling when length > max_length or length < 0
611 static void check_array_allocation_length(int length, int max_length, TRAPS);
612
613 void set_vtable_length(int len) { _vtable_len= len; }
614
615 vtableEntry* start_of_vtable() const;
616 #if INCLUDE_CDS
617 void restore_unshareable_info(ClassLoaderData* loader_data, Handle protection_domain, TRAPS);
618 #endif
619 public:
620 Method* method_at_vtable(int index);
621
622 static ByteSize vtable_start_offset();
623 static ByteSize vtable_length_offset() {
624 return byte_offset_of(Klass, _vtable_len);
625 }
626
627 #if INCLUDE_CDS
628 // CDS support - remove and restore oops from metadata. Oops are not shared.
629 virtual void remove_unshareable_info();
630 virtual void remove_java_mirror();
631
632 bool is_unshareable_info_restored() const {
633 assert(is_shared(), "use this for shared classes only");
634 if (has_archived_mirror_index()) {
635 // _java_mirror is not a valid OopHandle but rather an encoded reference in the shared heap
636 return false;
637 } else if (_java_mirror.is_empty()) {
638 return false;
639 } else {
640 return true;
641 }
642 }
643 #endif // INCLUDE_CDS
644
645 public:
646 // ALL FUNCTIONS BELOW THIS POINT ARE DISPATCHED FROM AN OOP
647 // These functions describe behavior for the oop not the KLASS.
648
649 // actual oop size of obj in memory in word size.
650 virtual size_t oop_size(oop obj) const = 0;
651
652 // Size of klass in word size.
653 virtual int size() const = 0;
654
655 // Returns the Java name for a class (Resource allocated)
656 // For arrays, this returns the name of the element with a leading '['.
657 // For classes, this returns the name with the package separators
658 // turned into '.'s.
659 const char* external_name() const;
660 // Returns the name for a class (Resource allocated) as the class
661 // would appear in a signature.
662 // For arrays, this returns the name of the element with a leading '['.
663 // For classes, this returns the name with a leading 'L' and a trailing ';'
664 // and the package separators as '/'.
665 virtual const char* signature_name() const;
666
667 const char* joint_in_module_of_loader(const Klass* class2, bool include_parent_loader = false) const;
668 const char* class_in_module_of_loader(bool use_are = false, bool include_parent_loader = false) const;
669
670 // Returns "interface", "abstract class" or "class".
671 const char* external_kind() const;
672
673 // type testing operations
674 #ifdef ASSERT
675 protected:
676 virtual bool is_instance_klass_slow() const { return false; }
677 virtual bool is_array_klass_slow() const { return false; }
678 virtual bool is_objArray_klass_slow() const { return false; }
679 virtual bool is_typeArray_klass_slow() const { return false; }
680 #endif // ASSERT
681 public:
682
683 // Fast non-virtual versions
684 #ifndef ASSERT
685 #define assert_same_query(xval, xcheck) xval
686 #else
687 private:
688 static bool assert_same_query(bool xval, bool xslow) {
689 assert(xval == xslow, "slow and fast queries agree");
690 return xval;
691 }
692 public:
693 #endif
694
695 bool is_instance_klass() const { return assert_same_query(_kind <= InstanceStackChunkKlassKind, is_instance_klass_slow()); }
696 // Other is anything that is not one of the more specialized kinds of InstanceKlass.
697 bool is_other_instance_klass() const { return _kind == InstanceKlassKind; }
698 bool is_reference_instance_klass() const { return _kind == InstanceRefKlassKind; }
699 bool is_mirror_instance_klass() const { return _kind == InstanceMirrorKlassKind; }
700 bool is_class_loader_instance_klass() const { return _kind == InstanceClassLoaderKlassKind; }
701 bool is_array_klass() const { return assert_same_query( _kind >= TypeArrayKlassKind, is_array_klass_slow()); }
702 bool is_stack_chunk_instance_klass() const { return _kind == InstanceStackChunkKlassKind; }
703 bool is_objArray_klass() const { return assert_same_query( _kind == ObjArrayKlassKind, is_objArray_klass_slow()); }
704 bool is_typeArray_klass() const { return assert_same_query( _kind == TypeArrayKlassKind, is_typeArray_klass_slow()); }
705 #undef assert_same_query
706
707 // Access flags
708 AccessFlags access_flags() const { return _access_flags; }
709 void set_access_flags(AccessFlags flags) { _access_flags = flags; }
710
711 bool is_public() const { return _access_flags.is_public(); }
712 bool is_final() const { return _access_flags.is_final(); }
713 bool is_interface() const { return _access_flags.is_interface(); }
714 bool is_abstract() const { return _access_flags.is_abstract(); }
715 bool is_super() const { return _access_flags.is_super(); }
716 bool is_synthetic() const { return _access_flags.is_synthetic(); }
717 void set_is_synthetic() { _access_flags.set_is_synthetic(); }
718 bool has_finalizer() const { return _misc_flags.has_finalizer(); }
719 void set_has_finalizer() { _misc_flags.set_has_finalizer(true); }
720 bool is_hidden() const { return _misc_flags.is_hidden_class(); }
721 void set_is_hidden() { _misc_flags.set_is_hidden_class(true); }
722 bool is_value_based() const { return _misc_flags.is_value_based_class(); }
723 void set_is_value_based() { _misc_flags.set_is_value_based_class(true); }
724
725 klass_flags_t misc_flags() const { return _misc_flags.value(); }
726
727 inline bool is_non_strong_hidden() const;
728
729 bool is_cloneable() const;
730 void set_is_cloneable();
731
732 inline markWord prototype_header() const;
733 inline void set_prototype_header(markWord header);
734 static ByteSize prototype_header_offset() { return in_ByteSize(offset_of(Klass, _prototype_header)); }
735
736 JFR_ONLY(DEFINE_TRACE_ID_METHODS;)
737
738 virtual void metaspace_pointers_do(MetaspaceClosure* iter);
739 virtual MetaspaceObj::Type type() const { return ClassType; }
740
741 inline bool is_loader_alive() const;
742
743 void clean_subklass();
744
745 static void clean_weak_klass_links(bool unloading_occurred, bool clean_alive_klasses = true);
746 static void clean_subklass_tree() {
747 clean_weak_klass_links(/*unloading_occurred*/ true , /* clean_alive_klasses */ false);
748 }
749
750 // Return self, except for abstract classes with exactly 1
751 // implementor. Then return the 1 concrete implementation.
752 Klass *up_cast_abstract();
753
754 // klass name
755 Symbol* name() const { return _name; }
756 void set_name(Symbol* n);
757
758 virtual void release_C_heap_structures(bool release_constant_pool = true);
759
760 public:
761 virtual u2 compute_modifier_flags() const = 0;
762
763 // JVMTI support
764 virtual jint jvmti_class_status() const;
765
766 // Printing
767 virtual void print_on(outputStream* st) const;
768
769 virtual void oop_print_value_on(oop obj, outputStream* st);
770 virtual void oop_print_on (oop obj, outputStream* st);
771
772 void print_secondary_supers_on(outputStream* st) const;
773
774 virtual const char* internal_name() const = 0;
775
776 // Verification
777 virtual void verify_on(outputStream* st);
778 void verify() { verify_on(tty); }
779
780 #ifndef PRODUCT
781 bool verify_vtable_index(int index);
782 #endif
783
784 virtual void oop_verify_on(oop obj, outputStream* st);
785
786 // for error reporting
787 static bool is_valid(Klass* k);
788
789 static void on_secondary_supers_verification_failure(Klass* super, Klass* sub, bool linear_result, bool table_result, const char* msg);
790
791 // Returns true if this Klass needs to be addressable via narrow Klass ID.
792 inline bool needs_narrow_id() const;
793
794 };
795
796 #endif // SHARE_OOPS_KLASS_HPP