1 /*
2 * Copyright (c) 1997, 2024, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
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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/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 {
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 // Processed access flags, for use by Class.getModifiers.
124 jint _modifier_flags;
125
126 // The fields _super_check_offset, _secondary_super_cache, _secondary_supers
127 // and _primary_supers all help make fast subtype checks. See big discussion
128 // in doc/server_compiler/checktype.txt
129 //
130 // Where to look to observe a supertype (it is &_secondary_super_cache for
131 // secondary supers, else is &_primary_supers[depth()].
132 juint _super_check_offset;
133
134 // Class name. Instance classes: java/lang/String, etc. Array classes: [I,
135 // [Ljava/lang/String;, etc. Set to zero for all other kinds of classes.
136 Symbol* _name;
137
138 // Cache of last observed secondary supertype
139 Klass* _secondary_super_cache;
140 // Array of all secondary supertypes
141 Array<Klass*>* _secondary_supers;
142 // Ordered list of all primary supertypes
143 Klass* _primary_supers[_primary_super_limit];
144 // java/lang/Class instance mirroring this class
145 OopHandle _java_mirror;
146 // Superclass
147 Klass* _super;
148 // First subclass (null if none); _subklass->next_sibling() is next one
149 Klass* volatile _subklass;
150 // Sibling link (or null); links all subklasses of a klass
151 Klass* volatile _next_sibling;
152
153 // All klasses loaded by a class loader are chained through these links
154 Klass* _next_link;
155
156 // The VM's representation of the ClassLoader used to load this class.
157 // Provide access the corresponding instance java.lang.ClassLoader.
158 ClassLoaderData* _class_loader_data;
159
160 // Bitmap and hash code used by hashed secondary supers.
161 uintx _secondary_supers_bitmap;
162 uint8_t _hash_slot;
163
164 markWord _prototype_header; // Used to initialize objects' header
165
166 int _vtable_len; // vtable length. This field may be read very often when we
167 // have lots of itable dispatches (e.g., lambdas and streams).
168 // Keep it away from the beginning of a Klass to avoid cacheline
169 // contention that may happen when a nearby object is modified.
170 AccessFlags _access_flags; // Access flags. The class/interface distinction is stored here.
171 // Some flags created by the JVM, not in the class file itself,
172 // are in _misc_flags below.
173
174 JFR_ONLY(DEFINE_TRACE_ID_FIELD;)
175
176 private:
177 // This is an index into FileMapHeader::_shared_path_table[], to
178 // associate this class with the JAR file where it's loaded from during
179 // dump time. If a class is not loaded from the shared archive, this field is
180 // -1.
181 s2 _shared_class_path_index;
182
183 #if INCLUDE_CDS
184 // Various attributes for shared classes. Should be zero for a non-shared class.
185 u2 _shared_class_flags;
186 enum CDSSharedClassFlags {
187 _is_shared_class = 1 << 0, // shadows MetaspaceObj::is_shared
188 _archived_lambda_proxy_is_available = 1 << 1,
189 _has_value_based_class_annotation = 1 << 2,
190 _verified_at_dump_time = 1 << 3,
191 _has_archived_enum_objs = 1 << 4,
192 // This class was not loaded from a classfile in the module image
193 // or classpath.
194 _is_generated_shared_class = 1 << 5,
195 // archived mirror already initialized by AOT-cache assembly: no further need to call <clinit>
196 _has_aot_initialized_mirror = 1 << 6,
197 // If this class has been aot-inititalized, do we need to call its runtimeSetup()
198 // method during the production run?
199 _is_runtime_setup_required = 1 << 7,
200 };
201 #endif
202
203 KlassFlags _misc_flags;
204
205 CDS_JAVA_HEAP_ONLY(int _archived_mirror_index;)
206
207 protected:
208
209 Klass(KlassKind kind);
210 Klass();
211
212 public:
213 int kind() { return _kind; }
214
215 enum class DefaultsLookupMode { find, skip };
216 enum class OverpassLookupMode { find, skip };
217 enum class StaticLookupMode { find, skip };
218 enum class PrivateLookupMode { find, skip };
219
220 virtual bool is_klass() const { return true; }
221
222 // super() cannot be InstanceKlass* -- Java arrays are covariant, and _super is used
223 // to implement that. NB: the _super of "[Ljava/lang/Integer;" is "[Ljava/lang/Number;"
224 // If this is not what your code expects, you're probably looking for Klass::java_super().
225 Klass* super() const { return _super; }
226 void set_super(Klass* k) { _super = k; }
227
228 // initializes _super link, _primary_supers & _secondary_supers arrays
229 void initialize_supers(Klass* k, Array<InstanceKlass*>* transitive_interfaces, TRAPS);
230
231 // klass-specific helper for initializing _secondary_supers
232 virtual GrowableArray<Klass*>* compute_secondary_supers(int num_extra_slots,
233 Array<InstanceKlass*>* transitive_interfaces);
234
235 // java_super is the Java-level super type as specified by Class.getSuperClass.
236 virtual InstanceKlass* java_super() const { return nullptr; }
237
238 juint super_check_offset() const { return _super_check_offset; }
239 void set_super_check_offset(juint o) { _super_check_offset = o; }
240
241 Klass* secondary_super_cache() const { return _secondary_super_cache; }
242 void set_secondary_super_cache(Klass* k) { _secondary_super_cache = k; }
243
244 Array<Klass*>* secondary_supers() const { return _secondary_supers; }
245 void set_secondary_supers(Array<Klass*>* k, uintx bitmap);
246
247 uint8_t hash_slot() const { return _hash_slot; }
248
249 // Return the element of the _super chain of the given depth.
250 // If there is no such element, return either null or this.
251 Klass* primary_super_of_depth(juint i) const {
252 assert(i < primary_super_limit(), "oob");
253 Klass* super = _primary_supers[i];
254 assert(super == nullptr || super->super_depth() == i, "correct display");
255 return super;
256 }
257
258 // Can this klass be a primary super? False for interfaces and arrays of
259 // interfaces. False also for arrays or classes with long super chains.
260 bool can_be_primary_super() const {
261 const juint secondary_offset = in_bytes(secondary_super_cache_offset());
262 return super_check_offset() != secondary_offset;
263 }
264 virtual bool can_be_primary_super_slow() const;
265
266 // Returns number of primary supers; may be a number in the inclusive range [0, primary_super_limit].
267 juint super_depth() const {
268 if (!can_be_primary_super()) {
269 return primary_super_limit();
270 } else {
271 juint d = (super_check_offset() - in_bytes(primary_supers_offset())) / sizeof(Klass*);
272 assert(d < primary_super_limit(), "oob");
273 assert(_primary_supers[d] == this, "proper init");
274 return d;
275 }
276 }
277
278 // java mirror
279 oop java_mirror() const;
280 oop java_mirror_no_keepalive() const;
281 void set_java_mirror(Handle m);
282
283 oop archived_java_mirror() NOT_CDS_JAVA_HEAP_RETURN_(nullptr);
284 void set_archived_java_mirror(int mirror_index) NOT_CDS_JAVA_HEAP_RETURN;
285
286 // Temporary mirror switch used by RedefineClasses
287 OopHandle java_mirror_handle() const { return _java_mirror; }
288 void swap_java_mirror_handle(OopHandle& mirror) { _java_mirror.swap(mirror); }
289
290 // Set java mirror OopHandle to null for CDS
291 // This leaves the OopHandle in the CLD, but that's ok, you can't release them.
292 void clear_java_mirror_handle() { _java_mirror = OopHandle(); }
293
294 // modifier flags
295 jint modifier_flags() const { return _modifier_flags; }
296 void set_modifier_flags(jint flags) { _modifier_flags = flags; }
297
298 // size helper
299 int layout_helper() const { return _layout_helper; }
300 void set_layout_helper(int lh) { _layout_helper = lh; }
301
302 // Note: for instances layout_helper() may include padding.
303 // Use InstanceKlass::contains_field_offset to classify field offsets.
304
305 // sub/superklass links
306 Klass* subklass(bool log = false) const;
307 Klass* next_sibling(bool log = false) const;
308
309 InstanceKlass* superklass() const;
310 void append_to_sibling_list(); // add newly created receiver to superklass' subklass list
311
312 void set_next_link(Klass* k) { _next_link = k; }
313 Klass* next_link() const { return _next_link; } // The next klass defined by the class loader.
314 Klass** next_link_addr() { return &_next_link; }
315
316 // class loader data
317 ClassLoaderData* class_loader_data() const { return _class_loader_data; }
318 void set_class_loader_data(ClassLoaderData* loader_data) { _class_loader_data = loader_data; }
319
320 s2 shared_classpath_index() const {
321 return _shared_class_path_index;
322 };
323
324 void set_shared_classpath_index(s2 index) {
325 _shared_class_path_index = index;
326 };
327
328 bool has_archived_mirror_index() const {
329 CDS_JAVA_HEAP_ONLY(return _archived_mirror_index >= 0;)
330 NOT_CDS_JAVA_HEAP(return false);
331 }
332
333 void clear_archived_mirror_index() NOT_CDS_JAVA_HEAP_RETURN;
334
335 void set_lambda_proxy_is_available() {
336 CDS_ONLY(_shared_class_flags |= _archived_lambda_proxy_is_available;)
337 }
338 void clear_lambda_proxy_is_available() {
339 CDS_ONLY(_shared_class_flags &= (u2)(~_archived_lambda_proxy_is_available);)
340 }
341 bool lambda_proxy_is_available() const {
342 CDS_ONLY(return (_shared_class_flags & _archived_lambda_proxy_is_available) != 0;)
343 NOT_CDS(return false;)
344 }
345
346 void set_has_value_based_class_annotation() {
347 CDS_ONLY(_shared_class_flags |= _has_value_based_class_annotation;)
348 }
349 void clear_has_value_based_class_annotation() {
350 CDS_ONLY(_shared_class_flags &= (u2)(~_has_value_based_class_annotation);)
351 }
352 bool has_value_based_class_annotation() const {
353 CDS_ONLY(return (_shared_class_flags & _has_value_based_class_annotation) != 0;)
354 NOT_CDS(return false;)
355 }
356
357 void set_verified_at_dump_time() {
358 CDS_ONLY(_shared_class_flags |= _verified_at_dump_time;)
359 }
360 bool verified_at_dump_time() const {
361 CDS_ONLY(return (_shared_class_flags & _verified_at_dump_time) != 0;)
362 NOT_CDS(return false;)
363 }
364
365 void set_has_archived_enum_objs() {
366 CDS_ONLY(_shared_class_flags |= _has_archived_enum_objs;)
367 }
368 bool has_archived_enum_objs() const {
369 CDS_ONLY(return (_shared_class_flags & _has_archived_enum_objs) != 0;)
370 NOT_CDS(return false;)
371 }
372
373 void set_is_generated_shared_class() {
374 CDS_ONLY(_shared_class_flags |= _is_generated_shared_class;)
375 }
376 bool is_generated_shared_class() const {
377 CDS_ONLY(return (_shared_class_flags & _is_generated_shared_class) != 0;)
378 NOT_CDS(return false;)
379 }
380
381 void set_has_aot_initialized_mirror() {
382 CDS_ONLY(_shared_class_flags |= _has_aot_initialized_mirror;)
383 }
384 bool has_aot_initialized_mirror() const {
385 CDS_ONLY(return (_shared_class_flags & _has_aot_initialized_mirror) != 0;)
386 NOT_CDS(return false;)
387 }
388
389 void set_is_runtime_setup_required() {
390 assert(has_aot_initialized_mirror(), "sanity");
391 CDS_ONLY(_shared_class_flags |= _is_runtime_setup_required;)
392 }
393 bool is_runtime_setup_required() const {
394 CDS_ONLY(return (_shared_class_flags & _is_runtime_setup_required) != 0;)
395 NOT_CDS(return false;)
396 }
397
398 bool is_shared() const { // shadows MetaspaceObj::is_shared)()
399 CDS_ONLY(return (_shared_class_flags & _is_shared_class) != 0;)
400 NOT_CDS(return false;)
401 }
402
403 void set_is_shared() {
404 CDS_ONLY(_shared_class_flags |= _is_shared_class;)
405 }
406
407 // Obtain the module or package for this class
408 virtual ModuleEntry* module() const = 0;
409 virtual PackageEntry* package() const = 0;
410
411 protected: // internal accessors
412 void set_subklass(Klass* s);
413 void set_next_sibling(Klass* s);
414
415 private:
416 static uint8_t compute_hash_slot(Symbol* s);
417 static void hash_insert(Klass* klass, GrowableArray<Klass*>* secondaries, uintx& bitmap);
418 static uintx hash_secondary_supers(Array<Klass*>* secondaries, bool rewrite);
419
420 bool search_secondary_supers(Klass* k) const;
421 bool lookup_secondary_supers_table(Klass *k) const;
422 bool linear_search_secondary_supers(const Klass* k) const;
423 bool fallback_search_secondary_supers(const Klass* k, int index, uintx rotated_bitmap) const;
424
425 public:
426 // Secondary supers table support
427 static Array<Klass*>* pack_secondary_supers(ClassLoaderData* loader_data,
428 GrowableArray<Klass*>* primaries,
429 GrowableArray<Klass*>* secondaries,
430 uintx& bitmap,
431 TRAPS);
432
433 static uintx compute_secondary_supers_bitmap(Array<Klass*>* secondary_supers);
434 static uint8_t compute_home_slot(Klass* k, uintx bitmap);
435
436 static constexpr int SECONDARY_SUPERS_TABLE_SIZE = sizeof(_secondary_supers_bitmap) * 8;
437 static constexpr int SECONDARY_SUPERS_TABLE_MASK = SECONDARY_SUPERS_TABLE_SIZE - 1;
438
439 static constexpr uintx SECONDARY_SUPERS_BITMAP_EMPTY = 0;
440 static constexpr uintx SECONDARY_SUPERS_BITMAP_FULL = ~(uintx)0;
441
442 // Compiler support
443 static ByteSize super_offset() { return byte_offset_of(Klass, _super); }
444 static ByteSize super_check_offset_offset() { return byte_offset_of(Klass, _super_check_offset); }
445 static ByteSize primary_supers_offset() { return byte_offset_of(Klass, _primary_supers); }
446 static ByteSize secondary_super_cache_offset() { return byte_offset_of(Klass, _secondary_super_cache); }
447 static ByteSize secondary_supers_offset() { return byte_offset_of(Klass, _secondary_supers); }
448 static ByteSize java_mirror_offset() { return byte_offset_of(Klass, _java_mirror); }
449 static ByteSize class_loader_data_offset() { return byte_offset_of(Klass, _class_loader_data); }
450 static ByteSize modifier_flags_offset() { return byte_offset_of(Klass, _modifier_flags); }
451 static ByteSize layout_helper_offset() { return byte_offset_of(Klass, _layout_helper); }
452 static ByteSize access_flags_offset() { return byte_offset_of(Klass, _access_flags); }
453 #if INCLUDE_JVMCI
454 static ByteSize subklass_offset() { return byte_offset_of(Klass, _subklass); }
455 static ByteSize next_sibling_offset() { return byte_offset_of(Klass, _next_sibling); }
456 #endif
457 static ByteSize secondary_supers_bitmap_offset()
458 { return byte_offset_of(Klass, _secondary_supers_bitmap); }
459 static ByteSize hash_slot_offset() { return byte_offset_of(Klass, _hash_slot); }
460 static ByteSize misc_flags_offset() { return byte_offset_of(Klass, _misc_flags._flags); }
461
462 // Unpacking layout_helper:
463 static const int _lh_neutral_value = 0; // neutral non-array non-instance value
464 static const int _lh_instance_slow_path_bit = 0x01;
465 static const int _lh_log2_element_size_shift = BitsPerByte*0;
466 static const int _lh_log2_element_size_mask = BitsPerLong-1;
467 static const int _lh_element_type_shift = BitsPerByte*1;
468 static const int _lh_element_type_mask = right_n_bits(BitsPerByte); // shifted mask
469 static const int _lh_header_size_shift = BitsPerByte*2;
470 static const int _lh_header_size_mask = right_n_bits(BitsPerByte); // shifted mask
471 static const int _lh_array_tag_bits = 2;
472 static const int _lh_array_tag_shift = BitsPerInt - _lh_array_tag_bits;
473 static const int _lh_array_tag_obj_value = ~0x01; // 0x80000000 >> 30
474
475 static const unsigned int _lh_array_tag_type_value = 0Xffffffff; // ~0x00, // 0xC0000000 >> 30
476
477 static int layout_helper_size_in_bytes(jint lh) {
478 assert(lh > (jint)_lh_neutral_value, "must be instance");
479 return (int) lh & ~_lh_instance_slow_path_bit;
480 }
481 static bool layout_helper_needs_slow_path(jint lh) {
482 assert(lh > (jint)_lh_neutral_value, "must be instance");
483 return (lh & _lh_instance_slow_path_bit) != 0;
484 }
485 static bool layout_helper_is_instance(jint lh) {
486 return (jint)lh > (jint)_lh_neutral_value;
487 }
488 static bool layout_helper_is_array(jint lh) {
489 return (jint)lh < (jint)_lh_neutral_value;
490 }
491 static bool layout_helper_is_typeArray(jint lh) {
492 // _lh_array_tag_type_value == (lh >> _lh_array_tag_shift);
493 return (juint)lh >= (juint)(_lh_array_tag_type_value << _lh_array_tag_shift);
494 }
495 static bool layout_helper_is_objArray(jint lh) {
496 // _lh_array_tag_obj_value == (lh >> _lh_array_tag_shift);
497 return (jint)lh < (jint)(_lh_array_tag_type_value << _lh_array_tag_shift);
498 }
499 static int layout_helper_header_size(jint lh) {
500 assert(lh < (jint)_lh_neutral_value, "must be array");
501 int hsize = (lh >> _lh_header_size_shift) & _lh_header_size_mask;
502 assert(hsize > 0 && hsize < (int)sizeof(oopDesc)*3, "sanity");
503 return hsize;
504 }
505 static BasicType layout_helper_element_type(jint lh) {
506 assert(lh < (jint)_lh_neutral_value, "must be array");
507 int btvalue = (lh >> _lh_element_type_shift) & _lh_element_type_mask;
508 assert(btvalue >= T_BOOLEAN && btvalue <= T_OBJECT, "sanity");
509 return (BasicType) btvalue;
510 }
511
512 // Want a pattern to quickly diff against layout header in register
513 // find something less clever!
514 static int layout_helper_boolean_diffbit() {
515 jint zlh = array_layout_helper(T_BOOLEAN);
516 jint blh = array_layout_helper(T_BYTE);
517 assert(zlh != blh, "array layout helpers must differ");
518 int diffbit = 1;
519 while ((diffbit & (zlh ^ blh)) == 0 && (diffbit & zlh) == 0) {
520 diffbit <<= 1;
521 assert(diffbit != 0, "make sure T_BOOLEAN has a different bit than T_BYTE");
522 }
523 return diffbit;
524 }
525
526 static int layout_helper_log2_element_size(jint lh) {
527 assert(lh < (jint)_lh_neutral_value, "must be array");
528 int l2esz = (lh >> _lh_log2_element_size_shift) & _lh_log2_element_size_mask;
529 assert(l2esz <= LogBytesPerLong,
530 "sanity. l2esz: 0x%x for lh: 0x%x", (uint)l2esz, (uint)lh);
531 return l2esz;
532 }
533 static jint array_layout_helper(jint tag, int hsize, BasicType etype, int log2_esize) {
534 return (tag << _lh_array_tag_shift)
535 | (hsize << _lh_header_size_shift)
536 | ((int)etype << _lh_element_type_shift)
537 | (log2_esize << _lh_log2_element_size_shift);
538 }
539 static jint instance_layout_helper(jint size, bool slow_path_flag) {
540 return (size << LogBytesPerWord)
541 | (slow_path_flag ? _lh_instance_slow_path_bit : 0);
542 }
543 static int layout_helper_to_size_helper(jint lh) {
544 assert(lh > (jint)_lh_neutral_value, "must be instance");
545 // Note that the following expression discards _lh_instance_slow_path_bit.
546 return lh >> LogBytesPerWord;
547 }
548 // Out-of-line version computes everything based on the etype:
549 static jint array_layout_helper(BasicType etype);
550
551 // What is the maximum number of primary superclasses any klass can have?
552 static juint primary_super_limit() { return _primary_super_limit; }
553
554 // vtables
555 klassVtable vtable() const;
556 int vtable_length() const { return _vtable_len; }
557
558 // subclass check
559 bool is_subclass_of(const Klass* k) const;
560
561 // subtype check: true if is_subclass_of, or if k is interface and receiver implements it
562 bool is_subtype_of(Klass* k) const;
563
564 public:
565 // Find LCA in class hierarchy
566 Klass *LCA( Klass *k );
567
568 // Check whether reflection/jni/jvm code is allowed to instantiate this class;
569 // if not, throw either an Error or an Exception.
570 virtual void check_valid_for_instantiation(bool throwError, TRAPS);
571
572 // array copying
573 virtual void copy_array(arrayOop s, int src_pos, arrayOop d, int dst_pos, int length, TRAPS);
574
575 // tells if the class should be initialized
576 virtual bool should_be_initialized() const { return false; }
577 // initializes the klass
578 virtual void initialize(TRAPS);
579 virtual Klass* find_field(Symbol* name, Symbol* signature, fieldDescriptor* fd) const;
580 virtual Method* uncached_lookup_method(const Symbol* name, const Symbol* signature,
581 OverpassLookupMode overpass_mode,
582 PrivateLookupMode = PrivateLookupMode::find) const;
583 public:
584 Method* lookup_method(const Symbol* name, const Symbol* signature) const {
585 return uncached_lookup_method(name, signature, OverpassLookupMode::find);
586 }
587
588 // array class with specific rank
589 virtual ArrayKlass* array_klass(int rank, TRAPS) = 0;
590
591 // array class with this klass as element type
592 virtual ArrayKlass* array_klass(TRAPS) = 0;
593
594 // These will return null instead of allocating on the heap:
595 virtual ArrayKlass* array_klass_or_null(int rank) = 0;
596 virtual ArrayKlass* array_klass_or_null() = 0;
597
598 virtual oop protection_domain() const = 0;
599
600 oop class_loader() const;
601
602 inline oop klass_holder() const;
603
604 inline void keep_alive() const;
605
606 protected:
607
608 // Error handling when length > max_length or length < 0
609 static void check_array_allocation_length(int length, int max_length, TRAPS);
610
611 void set_vtable_length(int len) { _vtable_len= len; }
612
613 vtableEntry* start_of_vtable() const;
614 #if INCLUDE_CDS
615 void restore_unshareable_info(ClassLoaderData* loader_data, Handle protection_domain, TRAPS);
616 #endif
617 public:
618 Method* method_at_vtable(int index);
619
620 static ByteSize vtable_start_offset();
621 static ByteSize vtable_length_offset() {
622 return byte_offset_of(Klass, _vtable_len);
623 }
624
625 #if INCLUDE_CDS
626 // CDS support - remove and restore oops from metadata. Oops are not shared.
627 virtual void remove_unshareable_info();
628 virtual void remove_java_mirror();
629
630 bool is_unshareable_info_restored() const {
631 assert(is_shared(), "use this for shared classes only");
632 if (has_archived_mirror_index()) {
633 // _java_mirror is not a valid OopHandle but rather an encoded reference in the shared heap
634 return false;
635 } else if (_java_mirror.is_empty()) {
636 return false;
637 } else {
638 return true;
639 }
640 }
641 #endif // INCLUDE_CDS
642
643 public:
644 // ALL FUNCTIONS BELOW THIS POINT ARE DISPATCHED FROM AN OOP
645 // These functions describe behavior for the oop not the KLASS.
646
647 // actual oop size of obj in memory in word size.
648 virtual size_t oop_size(oop obj) const = 0;
649
650 // Size of klass in word size.
651 virtual int size() const = 0;
652
653 // Returns the Java name for a class (Resource allocated)
654 // For arrays, this returns the name of the element with a leading '['.
655 // For classes, this returns the name with the package separators
656 // turned into '.'s.
657 const char* external_name() const;
658 // Returns the name for a class (Resource allocated) as the class
659 // would appear in a signature.
660 // For arrays, this returns the name of the element with a leading '['.
661 // For classes, this returns the name with a leading 'L' and a trailing ';'
662 // and the package separators as '/'.
663 virtual const char* signature_name() const;
664
665 const char* joint_in_module_of_loader(const Klass* class2, bool include_parent_loader = false) const;
666 const char* class_in_module_of_loader(bool use_are = false, bool include_parent_loader = false) const;
667
668 // Returns "interface", "abstract class" or "class".
669 const char* external_kind() const;
670
671 // type testing operations
672 #ifdef ASSERT
673 protected:
674 virtual bool is_instance_klass_slow() const { return false; }
675 virtual bool is_array_klass_slow() const { return false; }
676 virtual bool is_objArray_klass_slow() const { return false; }
677 virtual bool is_typeArray_klass_slow() const { return false; }
678 #endif // ASSERT
679 public:
680
681 // Fast non-virtual versions
682 #ifndef ASSERT
683 #define assert_same_query(xval, xcheck) xval
684 #else
685 private:
686 static bool assert_same_query(bool xval, bool xslow) {
687 assert(xval == xslow, "slow and fast queries agree");
688 return xval;
689 }
690 public:
691 #endif
692
693 bool is_instance_klass() const { return assert_same_query(_kind <= InstanceStackChunkKlassKind, is_instance_klass_slow()); }
694 // Other is anything that is not one of the more specialized kinds of InstanceKlass.
695 bool is_other_instance_klass() const { return _kind == InstanceKlassKind; }
696 bool is_reference_instance_klass() const { return _kind == InstanceRefKlassKind; }
697 bool is_mirror_instance_klass() const { return _kind == InstanceMirrorKlassKind; }
698 bool is_class_loader_instance_klass() const { return _kind == InstanceClassLoaderKlassKind; }
699 bool is_array_klass() const { return assert_same_query( _kind >= TypeArrayKlassKind, is_array_klass_slow()); }
700 bool is_stack_chunk_instance_klass() const { return _kind == InstanceStackChunkKlassKind; }
701 bool is_objArray_klass() const { return assert_same_query( _kind == ObjArrayKlassKind, is_objArray_klass_slow()); }
702 bool is_typeArray_klass() const { return assert_same_query( _kind == TypeArrayKlassKind, is_typeArray_klass_slow()); }
703 #undef assert_same_query
704
705 // Access flags
706 AccessFlags access_flags() const { return _access_flags; }
707 void set_access_flags(AccessFlags flags) { _access_flags = flags; }
708
709 bool is_public() const { return _access_flags.is_public(); }
710 bool is_final() const { return _access_flags.is_final(); }
711 bool is_interface() const { return _access_flags.is_interface(); }
712 bool is_abstract() const { return _access_flags.is_abstract(); }
713 bool is_super() const { return _access_flags.is_super(); }
714 bool is_synthetic() const { return _access_flags.is_synthetic(); }
715 void set_is_synthetic() { _access_flags.set_is_synthetic(); }
716 bool has_finalizer() const { return _misc_flags.has_finalizer(); }
717 void set_has_finalizer() { _misc_flags.set_has_finalizer(true); }
718 bool is_hidden() const { return _misc_flags.is_hidden_class(); }
719 void set_is_hidden() { _misc_flags.set_is_hidden_class(true); }
720 bool is_value_based() const { return _misc_flags.is_value_based_class(); }
721 void set_is_value_based() { _misc_flags.set_is_value_based_class(true); }
722
723 klass_flags_t misc_flags() const { return _misc_flags.value(); }
724
725 inline bool is_non_strong_hidden() const;
726
727 bool is_cloneable() const;
728 void set_is_cloneable();
729
730 inline markWord prototype_header() const;
731 inline void set_prototype_header(markWord header);
732 static ByteSize prototype_header_offset() { return in_ByteSize(offset_of(Klass, _prototype_header)); }
733
734 JFR_ONLY(DEFINE_TRACE_ID_METHODS;)
735
736 virtual void metaspace_pointers_do(MetaspaceClosure* iter);
737 virtual MetaspaceObj::Type type() const { return ClassType; }
738
739 inline bool is_loader_alive() const;
740
741 void clean_subklass();
742
743 static void clean_weak_klass_links(bool unloading_occurred, bool clean_alive_klasses = true);
744 static void clean_subklass_tree() {
745 clean_weak_klass_links(/*unloading_occurred*/ true , /* clean_alive_klasses */ false);
746 }
747
748 // Return self, except for abstract classes with exactly 1
749 // implementor. Then return the 1 concrete implementation.
750 Klass *up_cast_abstract();
751
752 // klass name
753 Symbol* name() const { return _name; }
754 void set_name(Symbol* n);
755
756 virtual void release_C_heap_structures(bool release_constant_pool = true);
757
758 public:
759 virtual jint compute_modifier_flags() const = 0;
760
761 // JVMTI support
762 virtual jint jvmti_class_status() const;
763
764 // Printing
765 virtual void print_on(outputStream* st) const;
766
767 virtual void oop_print_value_on(oop obj, outputStream* st);
768 virtual void oop_print_on (oop obj, outputStream* st);
769
770 void print_secondary_supers_on(outputStream* st) const;
771
772 virtual const char* internal_name() const = 0;
773
774 // Verification
775 virtual void verify_on(outputStream* st);
776 void verify() { verify_on(tty); }
777
778 #ifndef PRODUCT
779 bool verify_vtable_index(int index);
780 #endif
781
782 virtual void oop_verify_on(oop obj, outputStream* st);
783
784 // for error reporting
785 static bool is_valid(Klass* k);
786
787 static void on_secondary_supers_verification_failure(Klass* super, Klass* sub, bool linear_result, bool table_result, const char* msg);
788
789 // Returns true if this Klass needs to be addressable via narrow Klass ID.
790 inline bool needs_narrow_id() const;
791
792 };
793
794 #endif // SHARE_OOPS_KLASS_HPP