1 /*
2 * Copyright (c) 1997, 2026, 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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16 * 2 along with this work; if not, write to the Free Software Foundation,
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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/macros.hpp"
34 #if INCLUDE_JFR
35 #include "jfr/support/jfrTraceIdExtension.hpp"
36 #endif
37
38 //
39 // A Klass provides:
40 // 1: language level class object (method dictionary etc.)
41 // 2: provide vm dispatch behavior for the object
42 // Both functions are combined into one C++ class.
43
44 // One reason for the oop/klass dichotomy in the implementation is
45 // that we don't want a C++ vtbl pointer in every object. Thus,
46 // normal oops don't have any virtual functions. Instead, they
47 // forward all "virtual" functions to their klass, which does have
48 // a vtbl and does the C++ dispatch depending on the object's
49 // actual type. (See oop.inline.hpp for some of the forwarding code.)
50 // ALL FUNCTIONS IMPLEMENTING THIS DISPATCH ARE PREFIXED WITH "oop_"!
51
52 // Forward declarations.
53 template <class T> class Array;
54 template <class T> class GrowableArray;
55 class ClassLoaderData;
56 class fieldDescriptor;
57 class klassVtable;
58 class ModuleEntry;
59 class PackageEntry;
60 class vtableEntry;
61
62 class Klass : public Metadata {
63
64 friend class VMStructs;
65 public:
66 // Klass Kinds for all subclasses of Klass
67 enum KlassKind : u2 {
68 InstanceKlassKind,
69 InstanceRefKlassKind,
70 InstanceMirrorKlassKind,
71 InstanceClassLoaderKlassKind,
72 InstanceStackChunkKlassKind,
73 TypeArrayKlassKind,
74 ObjArrayKlassKind,
75 UnknownKlassKind
76 };
77
78 static const uint KLASS_KIND_COUNT = ObjArrayKlassKind + 1;
79 protected:
80
81 // If you add a new field that points to any metaspace object, you
82 // must add this field to Klass::metaspace_pointers_do().
83
84 // note: put frequently-used fields together at start of klass structure
85 // for better cache behavior (may not make much of a difference but sure won't hurt)
86 enum { _primary_super_limit = 8 };
87
88 // The "layout helper" is a combined descriptor of object layout.
89 // For klasses which are neither instance nor array, the value is zero.
90 //
91 // For instances, layout helper is a positive number, the instance size.
92 // This size is already passed through align_object_size and scaled to bytes.
93 // The low order bit is set if instances of this class cannot be
94 // allocated using the fastpath.
95 //
96 // For arrays, layout helper is a negative number, containing four
97 // distinct bytes, as follows:
98 // MSB:[tag, hsz, ebt, log2(esz)]:LSB
99 // where:
100 // tag is 0x80 if the elements are oops, 0xC0 if non-oops
101 // hsz is array header size in bytes (i.e., offset of first element)
102 // ebt is the BasicType of the elements
103 // esz is the element size in bytes
104 // This packed word is arranged so as to be quickly unpacked by the
105 // various fast paths that use the various subfields.
106 //
107 // The esz bits can be used directly by a SLL instruction, without masking.
108 //
109 // Note that the array-kind tag looks like 0x00 for instance klasses,
110 // since their length in bytes is always less than 24Mb.
111 //
112 // Final note: This comes first, immediately after C++ vtable,
113 // because it is frequently queried.
114 jint _layout_helper;
115
116 // Klass kind used to resolve the runtime type of the instance.
117 // - Used to implement devirtualized oop closure dispatching.
118 // - Various type checking in the JVM
119 const KlassKind _kind;
120
121 // Some flags created by the JVM, not in the class file itself,
122 // are in _misc_flags below.
123 KlassFlags _misc_flags;
124
125 // The fields _super_check_offset, _secondary_super_cache, _secondary_supers
126 // and _primary_supers all help make fast subtype checks. See big discussion
127 // in doc/server_compiler/checktype.txt
128 //
129 // Where to look to observe a supertype (it is &_secondary_super_cache for
130 // secondary supers, else is &_primary_supers[depth()].
131 juint _super_check_offset;
132
133 // Class name. Instance classes: java/lang/String, etc. Array classes: [I,
134 // [Ljava/lang/String;, etc. Set to zero for all other kinds of classes.
135 Symbol* _name;
136
137 // Cache of last observed secondary supertype
138 Klass* _secondary_super_cache;
139 // Array of all secondary supertypes
140 Array<Klass*>* _secondary_supers;
141 // Ordered list of all primary supertypes
142 Klass* _primary_supers[_primary_super_limit];
143 // java/lang/Class instance mirroring this class
144 OopHandle _java_mirror;
145 // Superclass
146 Klass* _super;
147 // First subclass (null if none); _subklass->next_sibling() is next one
148 Klass* volatile _subklass;
149 // Sibling link (or null); links all subklasses of a klass
150 Klass* volatile _next_sibling;
151
152 // All klasses loaded by a class loader are chained through these links
153 Klass* _next_link;
154
155 // The VM's representation of the ClassLoader used to load this class.
156 // Provide access the corresponding instance java.lang.ClassLoader.
157 ClassLoaderData* _class_loader_data;
158
159 markWord _prototype_header; // Used to initialize objects' header
160
161 // Bitmap and hash code used by hashed secondary supers.
162 uintx _secondary_supers_bitmap;
163 uint8_t _hash_slot;
164
165 private:
166 // This is an index into AOTClassLocationConfig::class_locations(), to
167 // indicate the AOTClassLocation where this class is loaded from during
168 // dump time. If a class is not loaded from the AOT cache, this field is
169 // -1.
170 s2 _shared_class_path_index;
171
172 #if INCLUDE_CDS
173 // Various attributes for shared classes. Should be zero for a non-shared class.
174 u2 _aot_class_flags;
175 enum {
176 _in_aot_cache = 1 << 0,
177 _archived_lambda_proxy_is_available = 1 << 1,
178 _has_value_based_class_annotation = 1 << 2,
179 _verified_at_dump_time = 1 << 3,
180 _has_archived_enum_objs = 1 << 4,
181 _is_aot_generated_class = 1 << 5, // this class was not loaded from a classfile in the module image
182 // or classpath, but was generated during AOT cache assembly.
183 _has_aot_initialized_mirror = 1 << 6, // archived mirror already initialized by AOT cache assembly.
184 // no further need to call <clinit>
185 _has_aot_safe_initializer = 1 << 7, // has @AOTSafeClassInitializer annotation
186 _is_runtime_setup_required = 1 << 8, // has a runtimeSetup method to be called when
187 // this class is loaded from AOT cache
188 };
189 #endif
190
191 int _vtable_len; // vtable length. This field may be read very often when we
192 // have lots of itable dispatches (e.g., lambdas and streams).
193 // Keep it away from the beginning of a Klass to avoid cacheline
194 // contention that may happen when a nearby object is modified.
195
196 CDS_JAVA_HEAP_ONLY(int _archived_mirror_index;)
197
198 public:
199
200 JFR_ONLY(DEFINE_TRACE_ID_FIELD;)
201
202 protected:
203
204 Klass(KlassKind kind);
205 Klass();
206
207 void* operator new(size_t size, ClassLoaderData* loader_data, size_t word_size, TRAPS) throw();
208
209 public:
210 int kind() { return _kind; }
211
212 enum class DefaultsLookupMode { find, skip };
213 enum class OverpassLookupMode { find, skip };
214 enum class StaticLookupMode { find, skip };
215 enum class PrivateLookupMode { find, skip };
216
217 bool is_klass() const override { return true; }
218
219 // super() cannot be InstanceKlass* -- Java arrays are covariant, and _super is used
220 // to implement that. NB: the _super of "[Ljava/lang/Integer;" is "[Ljava/lang/Number;"
221 // If this is not what your code expects, you're probably looking for:
222 // - Klass::java_super() - if you have a Klass*
223 // - InstanceKlass::super() - if you have an InstanceKlass* ik, ik->super() returns InstanceKlass*.
224 Klass* super() const { return _super; }
225 void set_super(Klass* k) { _super = k; }
226
227 // initializes _super link, _primary_supers & _secondary_supers arrays
228 void initialize_supers(Klass* k, Array<InstanceKlass*>* transitive_interfaces, TRAPS);
229
230 // klass-specific helper for initializing _secondary_supers
231 virtual GrowableArray<Klass*>* compute_secondary_supers(int num_extra_slots,
232 Array<InstanceKlass*>* transitive_interfaces);
233
234 // java_super is the Java-level super type as specified by Class.getSuperClass.
235 virtual InstanceKlass* java_super() const { return nullptr; }
236
237 juint super_check_offset() const { return _super_check_offset; }
238 void set_super_check_offset(juint o) { _super_check_offset = o; }
239
240 Klass* secondary_super_cache() const { return _secondary_super_cache; }
241 void set_secondary_super_cache(Klass* k) { _secondary_super_cache = k; }
242
243 Array<Klass*>* secondary_supers() const { return _secondary_supers; }
244 void set_secondary_supers(Array<Klass*>* k, uintx bitmap);
245
246 uint8_t hash_slot() const { return _hash_slot; }
247
248 // Return the element of the _super chain of the given depth.
249 // If there is no such element, return either null or this.
250 Klass* primary_super_of_depth(juint i) const {
251 assert(i < primary_super_limit(), "oob");
252 Klass* super = _primary_supers[i];
253 assert(super == nullptr || super->super_depth() == i, "correct display");
254 return super;
255 }
256
257 // Can this klass be a primary super? False for interfaces and arrays of
258 // interfaces. False also for arrays or classes with long super chains.
259 bool can_be_primary_super() const {
260 const juint secondary_offset = in_bytes(secondary_super_cache_offset());
261 return super_check_offset() != secondary_offset;
262 }
263 virtual bool can_be_primary_super_slow() const;
264
265 // Returns number of primary supers; may be a number in the inclusive range [0, primary_super_limit].
266 juint super_depth() const {
267 if (!can_be_primary_super()) {
268 return primary_super_limit();
269 } else {
270 juint d = (super_check_offset() - in_bytes(primary_supers_offset())) / sizeof(Klass*);
271 assert(d < primary_super_limit(), "oob");
272 assert(_primary_supers[d] == this, "proper init");
273 return d;
274 }
275 }
276
277 // java mirror
278 oop java_mirror() const;
279 oop java_mirror_no_keepalive() const;
280 void set_java_mirror(Handle m);
281
282 oop archived_java_mirror() NOT_CDS_JAVA_HEAP_RETURN_(nullptr);
283
284 // Temporary mirror switch used by RedefineClasses
285 OopHandle java_mirror_handle() const { return _java_mirror; }
286 void swap_java_mirror_handle(OopHandle& mirror) { _java_mirror.swap(mirror); }
287
288 // Set java mirror OopHandle to null for CDS
289 // This leaves the OopHandle in the CLD, but that's ok, you can't release them.
290 void clear_java_mirror_handle() { _java_mirror = OopHandle(); }
291
292 // size helper
293 int layout_helper() const { return _layout_helper; }
294 void set_layout_helper(int lh) { _layout_helper = lh; }
295
296 // Note: for instances layout_helper() may include padding.
297 // Use InstanceKlass::contains_field_offset to classify field offsets.
298
299 // sub/superklass links
300 Klass* subklass() const;
301 Klass* next_sibling(bool log = false) const;
302
303 void append_to_sibling_list(); // add newly created receiver to superklass' subklass list
304
305 void set_next_link(Klass* k) { _next_link = k; }
306 Klass* next_link() const { return _next_link; } // The next klass defined by the class loader.
307 Klass** next_link_addr() { return &_next_link; }
308
309 // class loader data
310 ClassLoaderData* class_loader_data() const { return _class_loader_data; }
311 void set_class_loader_data(ClassLoaderData* loader_data) { _class_loader_data = loader_data; }
312
313 s2 shared_classpath_index() const {
314 return _shared_class_path_index;
315 };
316
317 void set_shared_classpath_index(s2 index) {
318 _shared_class_path_index = index;
319 };
320
321 bool has_archived_mirror_index() const {
322 CDS_JAVA_HEAP_ONLY(return _archived_mirror_index >= 0;)
323 NOT_CDS_JAVA_HEAP(return false);
324 }
325
326 void clear_archived_mirror_index() NOT_CDS_JAVA_HEAP_RETURN;
327
328 void set_lambda_proxy_is_available() {
329 CDS_ONLY(_aot_class_flags |= _archived_lambda_proxy_is_available;)
330 }
331 void clear_lambda_proxy_is_available() {
332 CDS_ONLY(_aot_class_flags &= (u2)(~_archived_lambda_proxy_is_available);)
333 }
334 bool lambda_proxy_is_available() const {
335 CDS_ONLY(return (_aot_class_flags & _archived_lambda_proxy_is_available) != 0;)
336 NOT_CDS(return false;)
337 }
338
339 void set_has_value_based_class_annotation() {
340 CDS_ONLY(_aot_class_flags |= _has_value_based_class_annotation;)
341 }
342 void clear_has_value_based_class_annotation() {
343 CDS_ONLY(_aot_class_flags &= (u2)(~_has_value_based_class_annotation);)
344 }
345 bool has_value_based_class_annotation() const {
346 CDS_ONLY(return (_aot_class_flags & _has_value_based_class_annotation) != 0;)
347 NOT_CDS(return false;)
348 }
349
350 void set_verified_at_dump_time() {
351 CDS_ONLY(_aot_class_flags |= _verified_at_dump_time;)
352 }
353 bool verified_at_dump_time() const {
354 CDS_ONLY(return (_aot_class_flags & _verified_at_dump_time) != 0;)
355 NOT_CDS(return false;)
356 }
357
358 void set_has_archived_enum_objs() {
359 CDS_ONLY(_aot_class_flags |= _has_archived_enum_objs;)
360 }
361 bool has_archived_enum_objs() const {
362 CDS_ONLY(return (_aot_class_flags & _has_archived_enum_objs) != 0;)
363 NOT_CDS(return false;)
364 }
365
366 void set_is_aot_generated_class() {
367 CDS_ONLY(_aot_class_flags |= _is_aot_generated_class;)
368 }
369 bool is_aot_generated_class() const {
370 CDS_ONLY(return (_aot_class_flags & _is_aot_generated_class) != 0;)
371 NOT_CDS(return false;)
372 }
373
374 void set_has_aot_initialized_mirror() {
375 CDS_ONLY(_aot_class_flags |= _has_aot_initialized_mirror;)
376 }
377 bool has_aot_initialized_mirror() const {
378 CDS_ONLY(return (_aot_class_flags & _has_aot_initialized_mirror) != 0;)
379 NOT_CDS(return false;)
380 }
381
382 // Indicates presence of @AOTSafeClassInitializer. Also see AOTClassInitializer for more details.
383 void set_has_aot_safe_initializer() {
384 CDS_ONLY(_aot_class_flags |= _has_aot_safe_initializer;)
385 }
386 bool has_aot_safe_initializer() const {
387 CDS_ONLY(return (_aot_class_flags & _has_aot_safe_initializer) != 0;)
388 NOT_CDS(return false;)
389 }
390
391 // Indicates @AOTRuntimeSetup private static void runtimeSetup() presence.
392 void set_is_runtime_setup_required() {
393 CDS_ONLY(_aot_class_flags |= _is_runtime_setup_required;)
394 }
395 bool is_runtime_setup_required() const {
396 CDS_ONLY(return (_aot_class_flags & _is_runtime_setup_required) != 0;)
397 NOT_CDS(return false;)
398 }
399
400 bool in_aot_cache() const { // shadows MetaspaceObj::in_aot_cache)()
401 CDS_ONLY(return (_aot_class_flags & _in_aot_cache) != 0;)
402 NOT_CDS(return false;)
403 }
404
405 void set_in_aot_cache() {
406 CDS_ONLY(_aot_class_flags |= _in_aot_cache;)
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 void set_next_sibling(Klass* s);
414 protected: // internal accessors
415 void set_subklass(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 layout_helper_offset() { return byte_offset_of(Klass, _layout_helper); }
453 static ByteSize secondary_supers_bitmap_offset()
454 { return byte_offset_of(Klass, _secondary_supers_bitmap); }
455 static ByteSize hash_slot_offset() { return byte_offset_of(Klass, _hash_slot); }
456 static ByteSize misc_flags_offset() { return byte_offset_of(Klass, _misc_flags._flags); }
457
458 // Unpacking layout_helper:
459 static const int _lh_neutral_value = 0; // neutral non-array non-instance value
460 static const int _lh_instance_slow_path_bit = 0x01;
461 static const int _lh_log2_element_size_shift = BitsPerByte*0;
462 static const int _lh_log2_element_size_mask = BitsPerLong-1;
463 static const int _lh_element_type_shift = BitsPerByte*1;
464 static const int _lh_element_type_mask = right_n_bits<int>(BitsPerByte); // shifted mask
465 static const int _lh_header_size_shift = BitsPerByte*2;
466 static const int _lh_header_size_mask = right_n_bits<int>(BitsPerByte); // shifted mask
467 static const int _lh_array_tag_bits = 2;
468 static const int _lh_array_tag_shift = BitsPerInt - _lh_array_tag_bits;
469 static const int _lh_array_tag_obj_value = ~0x01; // 0x80000000 >> 30
470
471 static const unsigned int _lh_array_tag_type_value = 0Xffffffff; // ~0x00, // 0xC0000000 >> 30
472
473 static int layout_helper_size_in_bytes(jint lh) {
474 assert(lh > (jint)_lh_neutral_value, "must be instance");
475 return (int) lh & ~_lh_instance_slow_path_bit;
476 }
477 static bool layout_helper_needs_slow_path(jint lh) {
478 assert(lh > (jint)_lh_neutral_value, "must be instance");
479 return (lh & _lh_instance_slow_path_bit) != 0;
480 }
481 static bool layout_helper_is_instance(jint lh) {
482 return (jint)lh > (jint)_lh_neutral_value;
483 }
484 static bool layout_helper_is_array(jint lh) {
485 return (jint)lh < (jint)_lh_neutral_value;
486 }
487 static bool layout_helper_is_typeArray(jint lh) {
488 // _lh_array_tag_type_value == (lh >> _lh_array_tag_shift);
489 return (juint)lh >= (juint)(_lh_array_tag_type_value << _lh_array_tag_shift);
490 }
491 static bool layout_helper_is_objArray(jint lh) {
492 // _lh_array_tag_obj_value == (lh >> _lh_array_tag_shift);
493 return (jint)lh < (jint)(_lh_array_tag_type_value << _lh_array_tag_shift);
494 }
495 static int layout_helper_header_size(jint lh) {
496 assert(lh < (jint)_lh_neutral_value, "must be array");
497 int hsize = (lh >> _lh_header_size_shift) & _lh_header_size_mask;
498 assert(hsize > 0 && hsize < (int)sizeof(oopDesc)*3, "sanity");
499 return hsize;
500 }
501 static BasicType layout_helper_element_type(jint lh) {
502 assert(lh < (jint)_lh_neutral_value, "must be array");
503 int btvalue = (lh >> _lh_element_type_shift) & _lh_element_type_mask;
504 assert(btvalue >= T_BOOLEAN && btvalue <= T_OBJECT, "sanity");
505 return (BasicType) btvalue;
506 }
507
508 // Return a value containing a single set bit that is in the bitset difference between the
509 // layout helpers for array-of-boolean and array-of-byte.
510 static int layout_helper_boolean_diffbit() {
511 uint zlh = static_cast<uint>(array_layout_helper(T_BOOLEAN));
512 uint blh = static_cast<uint>(array_layout_helper(T_BYTE));
513 // get all the bits that are set in zlh and clear in blh
514 uint candidates = (zlh & ~blh);
515 assert(candidates != 0, "must be"); // must be some if there is a solution.
516 // Use well known bit hack to isolate the low bit of candidates.
517 uint result = candidates & (-candidates);
518 assert(is_power_of_2(result), "must be power of 2");
519 assert((result & zlh) != 0, "must be set in alh of T_BOOLEAN");
520 assert((result & blh) == 0, "must be clear in alh of T_BYTE");
521 return static_cast<int>(result);
522 }
523
524 static int layout_helper_log2_element_size(jint lh) {
525 assert(lh < (jint)_lh_neutral_value, "must be array");
526 int l2esz = (lh >> _lh_log2_element_size_shift) & _lh_log2_element_size_mask;
527 assert(l2esz <= LogBytesPerLong,
528 "sanity. l2esz: 0x%x for lh: 0x%x", (uint)l2esz, (uint)lh);
529 return l2esz;
530 }
531 static jint array_layout_helper(jint tag, int hsize, BasicType etype, int log2_esize) {
532 return (tag << _lh_array_tag_shift)
533 | (hsize << _lh_header_size_shift)
534 | ((int)etype << _lh_element_type_shift)
535 | (log2_esize << _lh_log2_element_size_shift);
536 }
537 static jint instance_layout_helper(jint size, bool slow_path_flag) {
538 return (size << LogBytesPerWord)
539 | (slow_path_flag ? _lh_instance_slow_path_bit : 0);
540 }
541 static int layout_helper_to_size_helper(jint lh) {
542 assert(lh > (jint)_lh_neutral_value, "must be instance");
543 // Note that the following expression discards _lh_instance_slow_path_bit.
544 return lh >> LogBytesPerWord;
545 }
546 // Out-of-line version computes everything based on the etype:
547 static jint array_layout_helper(BasicType etype);
548
549 // What is the maximum number of primary superclasses any klass can have?
550 static juint primary_super_limit() { return _primary_super_limit; }
551
552 // vtables
553 klassVtable vtable() const;
554 int vtable_length() const { return _vtable_len; }
555
556 // subclass check
557 bool is_subclass_of(const Klass* k) const;
558
559 // subtype check: true if is_subclass_of, or if k is interface and receiver implements it
560 bool is_subtype_of(Klass* k) const;
561
562 public:
563 // Find LCA in class hierarchy
564 Klass *LCA( Klass *k );
565
566 // Check whether reflection/jni/jvm code is allowed to instantiate this class;
567 // if not, throw either an Error or an Exception.
568 virtual void check_valid_for_instantiation(bool throwError, TRAPS);
569
570 // array copying
571 virtual void copy_array(arrayOop s, int src_pos, arrayOop d, int dst_pos, int length, TRAPS);
572
573 // tells if the class should be initialized
574 virtual bool should_be_initialized() const { return false; }
575 // initializes the klass
576 virtual void initialize(TRAPS);
577 virtual void initialize_preemptable(TRAPS);
578 virtual Klass* find_field(Symbol* name, Symbol* signature, fieldDescriptor* fd) const;
579 virtual Method* uncached_lookup_method(const Symbol* name, const Symbol* signature,
580 OverpassLookupMode overpass_mode,
581 PrivateLookupMode = PrivateLookupMode::find) const;
582 public:
583 Method* lookup_method(const Symbol* name, const Symbol* signature) const {
584 return uncached_lookup_method(name, signature, OverpassLookupMode::find);
585 }
586
587 // array class with specific rank
588 virtual ArrayKlass* array_klass(int rank, TRAPS) = 0;
589
590 // array class with this klass as element type
591 virtual ArrayKlass* array_klass(TRAPS) = 0;
592
593 // These will return null instead of allocating on the heap:
594 virtual ArrayKlass* array_klass_or_null(int rank) = 0;
595 virtual ArrayKlass* array_klass_or_null() = 0;
596
597 virtual oop protection_domain() const = 0;
598
599 oop class_loader() const;
600
601 inline oop klass_holder() const;
602
603 inline void keep_alive() const;
604
605 protected:
606
607 // Error handling when length > max_length or length < 0
608 static void check_array_allocation_length(int length, int max_length, TRAPS);
609
610 void set_vtable_length(int len) { _vtable_len= len; }
611
612 vtableEntry* start_of_vtable() const;
613 #if INCLUDE_CDS
614 void restore_unshareable_info(ClassLoaderData* loader_data, Handle protection_domain, TRAPS);
615 #endif
616 public:
617 Method* method_at_vtable(int index);
618
619 static ByteSize vtable_start_offset();
620 static ByteSize vtable_length_offset() {
621 return byte_offset_of(Klass, _vtable_len);
622 }
623
624 #if INCLUDE_CDS
625 // CDS support - remove and restore oops from metadata. Oops are not shared.
626 virtual void remove_unshareable_info();
627 virtual void remove_java_mirror();
628
629 bool is_unshareable_info_restored() const {
630 assert(in_aot_cache(), "use this for shared classes only");
631 if (has_archived_mirror_index()) {
632 // _java_mirror is not a valid OopHandle but rather an encoded reference in the shared heap
633 return false;
634 } else if (_java_mirror.is_empty()) {
635 return false;
636 } else {
637 return true;
638 }
639 }
640 #endif // INCLUDE_CDS
641
642 public:
643 // ALL FUNCTIONS BELOW THIS POINT ARE DISPATCHED FROM AN OOP
644 // These functions describe behavior for the oop not the KLASS.
645
646 // actual oop size of obj in memory in word size.
647 virtual size_t oop_size(oop obj) const = 0;
648
649 // Returns the Java name for a class (Resource allocated)
650 // For arrays, this returns the name of the element with a leading '['.
651 // For classes, this returns the name with the package separators
652 // turned into '.'s.
653 const char* external_name() const;
654 // Returns the name for a class (Resource allocated) as the class
655 // would appear in a signature.
656 // For arrays, this returns the name of the element with a leading '['.
657 // For classes, this returns the name with a leading 'L' and a trailing ';'
658 // and the package separators as '/'.
659 virtual const char* signature_name() const;
660
661 const char* joint_in_module_of_loader(const Klass* class2, bool include_parent_loader = false) const;
662 const char* class_in_module_of_loader(bool use_are = false, bool include_parent_loader = false) const;
663
664 // Returns "interface", "abstract class" or "class".
665 const char* external_kind() const;
666
667 // type testing operations
668 #ifdef ASSERT
669 protected:
670 virtual bool is_instance_klass_slow() const { return false; }
671 virtual bool is_array_klass_slow() const { return false; }
672 virtual bool is_objArray_klass_slow() const { return false; }
673 virtual bool is_typeArray_klass_slow() const { return false; }
674 #endif // ASSERT
675 public:
676
677 // Fast non-virtual versions
678 #ifndef ASSERT
679 #define assert_same_query(xval, xcheck) xval
680 #else
681 private:
682 static bool assert_same_query(bool xval, bool xslow) {
683 assert(xval == xslow, "slow and fast queries agree");
684 return xval;
685 }
686 public:
687 #endif
688
689 bool is_instance_klass() const { return assert_same_query(_kind <= InstanceStackChunkKlassKind, is_instance_klass_slow()); }
690 // Other is anything that is not one of the more specialized kinds of InstanceKlass.
691 bool is_other_instance_klass() const { return _kind == InstanceKlassKind; }
692 bool is_reference_instance_klass() const { return _kind == InstanceRefKlassKind; }
693 bool is_mirror_instance_klass() const { return _kind == InstanceMirrorKlassKind; }
694 bool is_class_loader_instance_klass() const { return _kind == InstanceClassLoaderKlassKind; }
695 bool is_array_klass() const { return assert_same_query( _kind >= TypeArrayKlassKind, is_array_klass_slow()); }
696 bool is_stack_chunk_instance_klass() const { return _kind == InstanceStackChunkKlassKind; }
697 bool is_objArray_klass() const { return assert_same_query( _kind == ObjArrayKlassKind, is_objArray_klass_slow()); }
698 bool is_typeArray_klass() const { return assert_same_query( _kind == TypeArrayKlassKind, is_typeArray_klass_slow()); }
699 #undef assert_same_query
700
701
702 virtual bool is_interface() const { return false; }
703 virtual bool is_abstract() const { return false; }
704
705 bool has_finalizer() const { return _misc_flags.has_finalizer(); }
706 void set_has_finalizer() { _misc_flags.set_has_finalizer(true); }
707 bool is_hidden() const { return _misc_flags.is_hidden_class(); }
708 void set_is_hidden() { _misc_flags.set_is_hidden_class(true); }
709 bool is_value_based() const { return _misc_flags.is_value_based_class(); }
710 void set_is_value_based() { _misc_flags.set_is_value_based_class(true); }
711
712 klass_flags_t misc_flags() const { return _misc_flags.value(); }
713
714 inline bool is_non_strong_hidden() const;
715
716 bool is_cloneable() const;
717 void set_is_cloneable_fast() { _misc_flags.set_is_cloneable_fast(true); }
718
719 inline markWord prototype_header() const;
720 inline void set_prototype_header(markWord header);
721 static ByteSize prototype_header_offset() { return in_ByteSize(offset_of(Klass, _prototype_header)); }
722
723 JFR_ONLY(DEFINE_TRACE_ID_METHODS;)
724
725 void metaspace_pointers_do(MetaspaceClosure* iter) override;
726 MetaspaceObj::Type type() const override { return ClassType; }
727
728 inline bool is_loader_alive() const;
729 inline bool is_loader_present_and_alive() const;
730
731 Klass* clean_subklass(bool log = false);
732
733 // Clean out unnecessary weak klass links from the whole klass hierarchy.
734 static void clean_weak_klass_links(bool unloading_occurred, bool clean_alive_klasses = true);
735 // Clean out unnecessary weak klass links from the given InstanceKlass.
736 static void clean_weak_instanceklass_links(InstanceKlass* ik);
737
738 // Return self, except for abstract classes with exactly 1
739 // implementor. Then return the 1 concrete implementation.
740 Klass *up_cast_abstract();
741
742 // klass name
743 Symbol* name() const { return _name; }
744 void set_name(Symbol* n);
745
746 virtual void release_C_heap_structures(bool release_constant_pool = true);
747
748 public:
749 // Get modifier flags from Java mirror cache.
750 int modifier_flags() const;
751
752 // Compute modifier flags from the original data. This also allows
753 // accessing flags when Java mirror is already dead, e.g. during class
754 // unloading.
755 virtual u2 compute_modifier_flags() const = 0;
756
757 // JVMTI support
758 virtual jint jvmti_class_status() const;
759
760 // Printing
761 void print_on(outputStream* st) const override;
762
763 virtual void oop_print_value_on(oop obj, outputStream* st);
764 virtual void oop_print_on (oop obj, outputStream* st);
765
766 void print_secondary_supers_on(outputStream* st) const;
767
768 // Verification
769 virtual void verify_on(outputStream* st);
770 void verify() { verify_on(tty); }
771
772 #ifndef PRODUCT
773 bool verify_vtable_index(int index);
774 #endif
775
776 virtual void oop_verify_on(oop obj, outputStream* st);
777
778 // for error reporting
779 static bool is_valid(Klass* k);
780
781 static void on_secondary_supers_verification_failure(Klass* super, Klass* sub, bool linear_result, bool table_result, const char* msg);
782 };
783
784 #endif // SHARE_OOPS_KLASS_HPP