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 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
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23 */
24
25 #ifndef SHARE_OOPS_KLASS_HPP
26 #define SHARE_OOPS_KLASS_HPP
27
28 #include "memory/iterator.hpp"
29 #include "memory/memRegion.hpp"
30 #include "oops/markWord.hpp"
31 #include "oops/metadata.hpp"
32 #include "oops/oop.hpp"
33 #include "oops/oopHandle.hpp"
34 #include "utilities/accessFlags.hpp"
35 #include "utilities/macros.hpp"
36 #if INCLUDE_JFR
37 #include "jfr/support/jfrTraceIdExtension.hpp"
38 #endif
39
40 //
41 // A Klass provides:
42 // 1: language level class object (method dictionary etc.)
43 // 2: provide vm dispatch behavior for the object
44 // Both functions are combined into one C++ class.
45
46 // One reason for the oop/klass dichotomy in the implementation is
47 // that we don't want a C++ vtbl pointer in every object. Thus,
48 // normal oops don't have any virtual functions. Instead, they
49 // forward all "virtual" functions to their klass, which does have
50 // a vtbl and does the C++ dispatch depending on the object's
51 // actual type. (See oop.inline.hpp for some of the forwarding code.)
52 // ALL FUNCTIONS IMPLEMENTING THIS DISPATCH ARE PREFIXED WITH "oop_"!
53
54 // Forward declarations.
55 template <class T> class Array;
56 template <class T> class GrowableArray;
57 class ClassLoaderData;
58 class fieldDescriptor;
59 class klassVtable;
60 class ModuleEntry;
61 class PackageEntry;
62 class ParCompactionManager;
63 class PSPromotionManager;
64 class vtableEntry;
65
66 class Klass : public Metadata {
67 friend class VMStructs;
68 friend class JVMCIVMStructs;
69 public:
70 // Klass Kinds for all subclasses of Klass
71 enum KlassKind {
72 InstanceKlassKind,
73 InlineKlassKind,
74 InstanceRefKlassKind,
75 InstanceMirrorKlassKind,
76 InstanceClassLoaderKlassKind,
77 InstanceStackChunkKlassKind,
78 TypeArrayKlassKind,
79 FlatArrayKlassKind,
80 ObjArrayKlassKind,
81 UnknownKlassKind
82 };
83
84 static const uint KLASS_KIND_COUNT = ObjArrayKlassKind + 1;
85 protected:
86
87 // If you add a new field that points to any metaspace object, you
88 // must add this field to Klass::metaspace_pointers_do().
89
90 // note: put frequently-used fields together at start of klass structure
91 // for better cache behavior (may not make much of a difference but sure won't hurt)
92 enum { _primary_super_limit = 8 };
93
94 // The "layout helper" is a combined descriptor of object layout.
95 // For klasses which are neither instance nor array, the value is zero.
96 //
97 // For instances, layout helper is a positive number, the instance size.
98 // This size is already passed through align_object_size and scaled to bytes.
99 // The low order bit is set if instances of this class cannot be
100 // allocated using the fastpath.
101 //
102 // For arrays, layout helper is a negative number, containing four
103 // distinct bytes, as follows:
104 // MSB:[tag, hsz, ebt, log2(esz)]:LSB
105 // where:
106 // tag is 0x80 if the elements are oops, 0xC0 if non-oops, 0xA0 if value types
107 // hsz is array header size in bytes (i.e., offset of first element)
108 // ebt is the BasicType of the elements
109 // esz is the element size in bytes
110 // This packed word is arranged so as to be quickly unpacked by the
111 // various fast paths that use the various subfields.
112 //
113 // The esz bits can be used directly by a SLL instruction, without masking.
114 //
115 // Note that the array-kind tag looks like 0x00 for instance klasses,
116 // since their length in bytes is always less than 24Mb.
117 //
118 // Final note: This comes first, immediately after C++ vtable,
119 // because it is frequently queried.
120 jint _layout_helper;
121
122 // Klass kind used to resolve the runtime type of the instance.
123 // - Used to implement devirtualized oop closure dispatching.
124 // - Various type checking in the JVM
125 const KlassKind _kind;
126
127 // Processed access flags, for use by Class.getModifiers.
128 jint _modifier_flags;
129
130 // The fields _super_check_offset, _secondary_super_cache, _secondary_supers
131 // and _primary_supers all help make fast subtype checks. See big discussion
132 // in doc/server_compiler/checktype.txt
133 //
134 // Where to look to observe a supertype (it is &_secondary_super_cache for
135 // secondary supers, else is &_primary_supers[depth()].
136 juint _super_check_offset;
137
138 // Class name. Instance classes: java/lang/String, etc. Array classes: [I,
139 // [Ljava/lang/String;, etc. Set to zero for all other kinds of classes.
140 Symbol* _name;
141
142 // Cache of last observed secondary supertype
143 Klass* _secondary_super_cache;
144 // Array of all secondary supertypes
145 Array<Klass*>* _secondary_supers;
146 // Ordered list of all primary supertypes
147 Klass* _primary_supers[_primary_super_limit];
148 // java/lang/Class instance mirroring this class
149 OopHandle _java_mirror;
150 // Superclass
151 Klass* _super;
152 // First subclass (null if none); _subklass->next_sibling() is next one
153 Klass* volatile _subklass;
154 // Sibling link (or null); links all subklasses of a klass
155 Klass* volatile _next_sibling;
156
157 // All klasses loaded by a class loader are chained through these links
158 Klass* _next_link;
159
160 // The VM's representation of the ClassLoader used to load this class.
161 // Provide access the corresponding instance java.lang.ClassLoader.
162 ClassLoaderData* _class_loader_data;
163
164 // Bitmap and hash code used by hashed secondary supers.
165 uintx _bitmap;
166 uint8_t _hash_slot;
167
168 static uint8_t compute_hash_slot(Symbol* s);
169
170 int _vtable_len; // vtable length. This field may be read very often when we
171 // have lots of itable dispatches (e.g., lambdas and streams).
172 // Keep it away from the beginning of a Klass to avoid cacheline
173 // contention that may happen when a nearby object is modified.
174 AccessFlags _access_flags; // Access flags. The class/interface distinction is stored here.
175
176 JFR_ONLY(DEFINE_TRACE_ID_FIELD;)
177
178 markWord _prototype_header; // inline type and inline array mark patterns
179 private:
180 // This is an index into FileMapHeader::_shared_path_table[], to
181 // associate this class with the JAR file where it's loaded from during
182 // dump time. If a class is not loaded from the shared archive, this field is
183 // -1.
184 s2 _shared_class_path_index;
185
186 #if INCLUDE_CDS
187 // Various attributes for shared classes. Should be zero for a non-shared class.
188 u2 _shared_class_flags;
189 enum CDSSharedClassFlags {
190 _is_shared_class = 1 << 0, // shadows MetaspaceObj::is_shared
191 _archived_lambda_proxy_is_available = 1 << 1,
192 _has_value_based_class_annotation = 1 << 2,
193 _verified_at_dump_time = 1 << 3,
194 _has_archived_enum_objs = 1 << 4,
195 // This class was not loaded from a classfile in the module image
196 // or classpath.
197 _is_generated_shared_class = 1 << 5
198 };
199 #endif
200
201 CDS_JAVA_HEAP_ONLY(int _archived_mirror_index;)
202
203 protected:
204
205 Klass(KlassKind kind);
206 Klass();
207
208 void* operator new(size_t size, ClassLoaderData* loader_data, size_t word_size, TRAPS) throw();
209
210 public:
211 int kind() { return _kind; }
212
213 enum class DefaultsLookupMode { find, skip };
214 enum class OverpassLookupMode { find, skip };
215 enum class StaticLookupMode { find, skip };
216 enum class PrivateLookupMode { find, skip };
217
218 virtual bool is_klass() const { return true; }
219
220 // super() cannot be InstanceKlass* -- Java arrays are covariant, and _super is used
221 // to implement that. NB: the _super of "[Ljava/lang/Integer;" is "[Ljava/lang/Number;"
222 // If this is not what your code expects, you're probably looking for Klass::java_super().
223 Klass* super() const { return _super; }
224 void set_super(Klass* k) { _super = k; }
225
226 // initializes _super link, _primary_supers & _secondary_supers arrays
227 void initialize_supers(Klass* k, Array<InstanceKlass*>* transitive_interfaces, TRAPS);
228
229 // klass-specific helper for initializing _secondary_supers
230 virtual GrowableArray<Klass*>* compute_secondary_supers(int num_extra_slots,
231 Array<InstanceKlass*>* transitive_interfaces);
232
233 // java_super is the Java-level super type as specified by Class.getSuperClass.
234 virtual InstanceKlass* java_super() const { return nullptr; }
235
236 juint super_check_offset() const { return _super_check_offset; }
237 void set_super_check_offset(juint o) { _super_check_offset = o; }
238
239 Klass* secondary_super_cache() const { return _secondary_super_cache; }
240 void set_secondary_super_cache(Klass* k) { _secondary_super_cache = k; }
241
242 Array<Klass*>* secondary_supers() const { return _secondary_supers; }
243 void set_secondary_supers(Array<Klass*>* k);
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 void set_archived_java_mirror(int mirror_index) NOT_CDS_JAVA_HEAP_RETURN;
284
285 // Temporary mirror switch used by RedefineClasses
286 OopHandle java_mirror_handle() const { return _java_mirror; }
287 void swap_java_mirror_handle(OopHandle& mirror) { _java_mirror.swap(mirror); }
288
289 // Set java mirror OopHandle to null for CDS
290 // This leaves the OopHandle in the CLD, but that's ok, you can't release them.
291 void clear_java_mirror_handle() { _java_mirror = OopHandle(); }
292
293 // modifier flags
294 jint modifier_flags() const { return _modifier_flags; }
295 void set_modifier_flags(jint flags) { _modifier_flags = flags; }
296
297 // size helper
298 int layout_helper() const { return _layout_helper; }
299 void set_layout_helper(int lh) { _layout_helper = lh; }
300
301 // Note: for instances layout_helper() may include padding.
302 // Use InstanceKlass::contains_field_offset to classify field offsets.
303
304 // sub/superklass links
305 Klass* subklass(bool log = false) const;
306 Klass* next_sibling(bool log = false) const;
307
308 InstanceKlass* superklass() const;
309 void append_to_sibling_list(); // add newly created receiver to superklass' subklass list
310
311 void set_next_link(Klass* k) { _next_link = k; }
312 Klass* next_link() const { return _next_link; } // The next klass defined by the class loader.
313 Klass** next_link_addr() { return &_next_link; }
314
315 // class loader data
316 ClassLoaderData* class_loader_data() const { return _class_loader_data; }
317 void set_class_loader_data(ClassLoaderData* loader_data) { _class_loader_data = loader_data; }
318
319 s2 shared_classpath_index() const {
320 return _shared_class_path_index;
321 };
322
323 void set_shared_classpath_index(s2 index) {
324 _shared_class_path_index = index;
325 };
326
327 bool has_archived_mirror_index() const {
328 CDS_JAVA_HEAP_ONLY(return _archived_mirror_index >= 0;)
329 NOT_CDS_JAVA_HEAP(return false);
330 }
331
332 void clear_archived_mirror_index() NOT_CDS_JAVA_HEAP_RETURN;
333
334 void set_lambda_proxy_is_available() {
335 CDS_ONLY(_shared_class_flags |= _archived_lambda_proxy_is_available;)
336 }
337 void clear_lambda_proxy_is_available() {
338 CDS_ONLY(_shared_class_flags &= (u2)(~_archived_lambda_proxy_is_available);)
339 }
340 bool lambda_proxy_is_available() const {
341 CDS_ONLY(return (_shared_class_flags & _archived_lambda_proxy_is_available) != 0;)
342 NOT_CDS(return false;)
343 }
344
345 void set_has_value_based_class_annotation() {
346 CDS_ONLY(_shared_class_flags |= _has_value_based_class_annotation;)
347 }
348 void clear_has_value_based_class_annotation() {
349 CDS_ONLY(_shared_class_flags &= (u2)(~_has_value_based_class_annotation);)
350 }
351 bool has_value_based_class_annotation() const {
352 CDS_ONLY(return (_shared_class_flags & _has_value_based_class_annotation) != 0;)
353 NOT_CDS(return false;)
354 }
355
356 void set_verified_at_dump_time() {
357 CDS_ONLY(_shared_class_flags |= _verified_at_dump_time;)
358 }
359 bool verified_at_dump_time() const {
360 CDS_ONLY(return (_shared_class_flags & _verified_at_dump_time) != 0;)
361 NOT_CDS(return false;)
362 }
363
364 void set_has_archived_enum_objs() {
365 CDS_ONLY(_shared_class_flags |= _has_archived_enum_objs;)
366 }
367 bool has_archived_enum_objs() const {
368 CDS_ONLY(return (_shared_class_flags & _has_archived_enum_objs) != 0;)
369 NOT_CDS(return false;)
370 }
371
372 void set_is_generated_shared_class() {
373 CDS_ONLY(_shared_class_flags |= _is_generated_shared_class;)
374 }
375 bool is_generated_shared_class() const {
376 CDS_ONLY(return (_shared_class_flags & _is_generated_shared_class) != 0;)
377 NOT_CDS(return false;)
378 }
379
380 bool is_shared() const { // shadows MetaspaceObj::is_shared)()
381 CDS_ONLY(return (_shared_class_flags & _is_shared_class) != 0;)
382 NOT_CDS(return false;)
383 }
384
385 void set_is_shared() {
386 CDS_ONLY(_shared_class_flags |= _is_shared_class;)
387 }
388
389 // Obtain the module or package for this class
390 virtual ModuleEntry* module() const = 0;
391 virtual PackageEntry* package() const = 0;
392
393 protected: // internal accessors
394 void set_subklass(Klass* s);
395 void set_next_sibling(Klass* s);
396
397 private:
398 static void hash_insert(Klass* klass, GrowableArray<Klass*>* secondaries, uintx& bitmap);
399 static uintx hash_secondary_supers(Array<Klass*>* secondaries, bool rewrite);
400
401 public:
402 // Secondary supers table support
403 static Array<Klass*>* pack_secondary_supers(ClassLoaderData* loader_data,
404 GrowableArray<Klass*>* primaries,
405 GrowableArray<Klass*>* secondaries,
406 uintx& bitmap,
407 TRAPS);
408
409 static uintx compute_secondary_supers_bitmap(Array<Klass*>* secondary_supers);
410 static uint8_t compute_home_slot(Klass* k, uintx bitmap);
411
412 static constexpr int SECONDARY_SUPERS_TABLE_SIZE = sizeof(_bitmap) * 8;
413 static constexpr int SECONDARY_SUPERS_TABLE_MASK = SECONDARY_SUPERS_TABLE_SIZE - 1;
414
415 static constexpr uintx SECONDARY_SUPERS_BITMAP_EMPTY = 0;
416 static constexpr uintx SECONDARY_SUPERS_BITMAP_FULL = ~(uintx)0;
417
418 // Compiler support
419 static ByteSize super_offset() { return byte_offset_of(Klass, _super); }
420 static ByteSize super_check_offset_offset() { return byte_offset_of(Klass, _super_check_offset); }
421 static ByteSize primary_supers_offset() { return byte_offset_of(Klass, _primary_supers); }
422 static ByteSize secondary_super_cache_offset() { return byte_offset_of(Klass, _secondary_super_cache); }
423 static ByteSize secondary_supers_offset() { return byte_offset_of(Klass, _secondary_supers); }
424 static ByteSize java_mirror_offset() { return byte_offset_of(Klass, _java_mirror); }
425 static ByteSize class_loader_data_offset() { return byte_offset_of(Klass, _class_loader_data); }
426 static ByteSize modifier_flags_offset() { return byte_offset_of(Klass, _modifier_flags); }
427 static ByteSize layout_helper_offset() { return byte_offset_of(Klass, _layout_helper); }
428 static ByteSize access_flags_offset() { return byte_offset_of(Klass, _access_flags); }
429 #if INCLUDE_JVMCI
430 static ByteSize subklass_offset() { return byte_offset_of(Klass, _subklass); }
431 static ByteSize next_sibling_offset() { return byte_offset_of(Klass, _next_sibling); }
432 #endif
433 static ByteSize bitmap_offset() { return byte_offset_of(Klass, _bitmap); }
434
435 // Unpacking layout_helper:
436 static const int _lh_neutral_value = 0; // neutral non-array non-instance value
437 static const int _lh_instance_slow_path_bit = 0x01;
438 static const int _lh_log2_element_size_shift = BitsPerByte*0;
439 static const int _lh_log2_element_size_mask = BitsPerLong-1;
440 static const int _lh_element_type_shift = BitsPerByte*1;
441 static const int _lh_element_type_mask = right_n_bits(BitsPerByte); // shifted mask
442 static const int _lh_header_size_shift = BitsPerByte*2;
443 static const int _lh_header_size_mask = right_n_bits(BitsPerByte); // shifted mask
444 static const int _lh_array_tag_bits = 3;
445 static const int _lh_array_tag_shift = BitsPerInt - _lh_array_tag_bits;
446
447 static const unsigned int _lh_array_tag_type_value = 0Xfffffffc;
448 static const unsigned int _lh_array_tag_vt_value = 0Xfffffffd;
449 static const unsigned int _lh_array_tag_obj_value = 0Xfffffffe;
450
451 // null-free array flag bit under the array tag bits, shift one more to get array tag value
452 static const int _lh_null_free_shift = _lh_array_tag_shift - 1;
453 static const int _lh_null_free_mask = 1;
454
455 static const jint _lh_array_tag_flat_value_bit_inplace = (jint) (1 << _lh_array_tag_shift);
456
457 static int layout_helper_size_in_bytes(jint lh) {
458 assert(lh > (jint)_lh_neutral_value, "must be instance");
459 return (int) lh & ~_lh_instance_slow_path_bit;
460 }
461 static bool layout_helper_needs_slow_path(jint lh) {
462 assert(lh > (jint)_lh_neutral_value, "must be instance");
463 return (lh & _lh_instance_slow_path_bit) != 0;
464 }
465 static bool layout_helper_is_instance(jint lh) {
466 return (jint)lh > (jint)_lh_neutral_value;
467 }
468 static bool layout_helper_is_array(jint lh) {
469 return (jint)lh < (jint)_lh_neutral_value;
470 }
471 static bool layout_helper_is_typeArray(jint lh) {
472 return (juint) _lh_array_tag_type_value == (juint)(lh >> _lh_array_tag_shift);
473 }
474 static bool layout_helper_is_objArray(jint lh) {
475 return (juint)_lh_array_tag_obj_value == (juint)(lh >> _lh_array_tag_shift);
476 }
477 static bool layout_helper_is_flatArray(jint lh) {
478 return (juint)_lh_array_tag_vt_value == (juint)(lh >> _lh_array_tag_shift);
479 }
480 static bool layout_helper_is_null_free(jint lh) {
481 assert(layout_helper_is_flatArray(lh) || layout_helper_is_objArray(lh), "must be array of inline types");
482 return ((lh >> _lh_null_free_shift) & _lh_null_free_mask);
483 }
484 static jint layout_helper_set_null_free(jint lh) {
485 lh |= (_lh_null_free_mask << _lh_null_free_shift);
486 assert(layout_helper_is_null_free(lh), "Bad encoding");
487 return lh;
488 }
489 static int layout_helper_header_size(jint lh) {
490 assert(lh < (jint)_lh_neutral_value, "must be array");
491 int hsize = (lh >> _lh_header_size_shift) & _lh_header_size_mask;
492 assert(hsize > 0 && hsize < (int)sizeof(oopDesc)*3, "sanity");
493 return hsize;
494 }
495 static BasicType layout_helper_element_type(jint lh) {
496 assert(lh < (jint)_lh_neutral_value, "must be array");
497 int btvalue = (lh >> _lh_element_type_shift) & _lh_element_type_mask;
498 assert((btvalue >= T_BOOLEAN && btvalue <= T_OBJECT) || btvalue == T_PRIMITIVE_OBJECT, "sanity");
499 return (BasicType) btvalue;
500 }
501
502 // Want a pattern to quickly diff against layout header in register
503 // find something less clever!
504 static int layout_helper_boolean_diffbit() {
505 jint zlh = array_layout_helper(T_BOOLEAN);
506 jint blh = array_layout_helper(T_BYTE);
507 assert(zlh != blh, "array layout helpers must differ");
508 int diffbit = 1;
509 while ((diffbit & (zlh ^ blh)) == 0 && (diffbit & zlh) == 0) {
510 diffbit <<= 1;
511 assert(diffbit != 0, "make sure T_BOOLEAN has a different bit than T_BYTE");
512 }
513 return diffbit;
514 }
515
516 static int layout_helper_log2_element_size(jint lh) {
517 assert(lh < (jint)_lh_neutral_value, "must be array");
518 int l2esz = (lh >> _lh_log2_element_size_shift) & _lh_log2_element_size_mask;
519 assert(layout_helper_element_type(lh) == T_PRIMITIVE_OBJECT || l2esz <= LogBytesPerLong,
520 "sanity. l2esz: 0x%x for lh: 0x%x", (uint)l2esz, (uint)lh);
521 return l2esz;
522 }
523 static jint array_layout_helper(jint tag, bool null_free, int hsize, BasicType etype, int log2_esize) {
524 return (tag << _lh_array_tag_shift)
525 | ((null_free ? 1 : 0) << _lh_null_free_shift)
526 | (hsize << _lh_header_size_shift)
527 | ((int)etype << _lh_element_type_shift)
528 | (log2_esize << _lh_log2_element_size_shift);
529 }
530 static jint instance_layout_helper(jint size, bool slow_path_flag) {
531 return (size << LogBytesPerWord)
532 | (slow_path_flag ? _lh_instance_slow_path_bit : 0);
533 }
534 static int layout_helper_to_size_helper(jint lh) {
535 assert(lh > (jint)_lh_neutral_value, "must be instance");
536 // Note that the following expression discards _lh_instance_slow_path_bit.
537 return lh >> LogBytesPerWord;
538 }
539 // Out-of-line version computes everything based on the etype:
540 static jint array_layout_helper(BasicType etype);
541
542 // What is the maximum number of primary superclasses any klass can have?
543 static juint primary_super_limit() { return _primary_super_limit; }
544
545 // vtables
546 klassVtable vtable() const;
547 int vtable_length() const { return _vtable_len; }
548
549 // subclass check
550 bool is_subclass_of(const Klass* k) const;
551 // subtype check: true if is_subclass_of, or if k is interface and receiver implements it
552 bool is_subtype_of(Klass* k) const {
553 juint off = k->super_check_offset();
554 Klass* sup = *(Klass**)( (address)this + off );
555 const juint secondary_offset = in_bytes(secondary_super_cache_offset());
556 if (sup == k) {
557 return true;
558 } else if (off != secondary_offset) {
559 return false;
560 } else {
561 return search_secondary_supers(k);
562 }
563 }
564
565 bool search_secondary_supers(Klass* k) const;
566
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 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 virtual bool is_flatArray_klass_slow() const { return false; }
679 #endif // ASSERT
680 // current implementation uses this method even in non debug builds
681 virtual bool is_inline_klass_slow() const { return false; }
682 public:
683
684 // Fast non-virtual versions
685 #ifndef ASSERT
686 #define assert_same_query(xval, xcheck) xval
687 #else
688 private:
689 static bool assert_same_query(bool xval, bool xslow) {
690 assert(xval == xslow, "slow and fast queries agree");
691 return xval;
692 }
693 public:
694 #endif
695
696 bool is_instance_klass() const { return assert_same_query(_kind <= InstanceStackChunkKlassKind, is_instance_klass_slow()); }
697 bool is_inline_klass() const { return assert_same_query(_kind == InlineKlassKind, is_inline_klass_slow()); }
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_flatArray_klass() const { return assert_same_query( _kind == FlatArrayKlassKind, is_flatArray_klass_slow()); }
704 bool is_objArray_klass() const { return assert_same_query( _kind == ObjArrayKlassKind, is_objArray_klass_slow()); }
705 bool is_typeArray_klass() const { return assert_same_query( _kind == TypeArrayKlassKind, is_typeArray_klass_slow()); }
706 #undef assert_same_query
707
708 inline bool is_null_free_array_klass() const { return layout_helper_is_null_free(layout_helper()); }
709
710 // Access flags
711 AccessFlags access_flags() const { return _access_flags; }
712 void set_access_flags(AccessFlags flags) { _access_flags = flags; }
713
714 bool is_public() const { return _access_flags.is_public(); }
715 bool is_final() const { return _access_flags.is_final(); }
716 bool is_interface() const { return _access_flags.is_interface(); }
717 bool is_abstract() const { return _access_flags.is_abstract(); }
718 bool is_synthetic() const { return _access_flags.is_synthetic(); }
719 bool is_identity_class() const { return _access_flags.is_identity_class(); }
720 void set_is_synthetic() { _access_flags.set_is_synthetic(); }
721 bool has_finalizer() const { return _access_flags.has_finalizer(); }
722 void set_has_finalizer() { _access_flags.set_has_finalizer(); }
723 bool is_hidden() const { return access_flags().is_hidden_class(); }
724 void set_is_hidden() { _access_flags.set_is_hidden_class(); }
725 bool is_value_based() { return _access_flags.is_value_based_class(); }
726 void set_is_value_based() { _access_flags.set_is_value_based_class(); }
727
728 inline bool is_non_strong_hidden() const;
729
730 bool is_cloneable() const;
731 void set_is_cloneable();
732
733 // inline types and inline type array patterns
734 markWord prototype_header() const {
735 return _prototype_header;
736 }
737 static inline markWord default_prototype_header(Klass* k) {
738 return (k == nullptr) ? markWord::prototype() : k->prototype_header();
739 }
740
741 inline void set_prototype_header(markWord header);
742 static ByteSize prototype_header_offset() { return in_ByteSize(offset_of(Klass, _prototype_header)); }
743
744 JFR_ONLY(DEFINE_TRACE_ID_METHODS;)
745
746 virtual void metaspace_pointers_do(MetaspaceClosure* iter);
747 virtual MetaspaceObj::Type type() const { return ClassType; }
748
749 inline bool is_loader_alive() const;
750
751 void clean_subklass();
752
753 static void clean_weak_klass_links(bool unloading_occurred, bool clean_alive_klasses = true);
754 static void clean_subklass_tree() {
755 clean_weak_klass_links(/*unloading_occurred*/ true , /* clean_alive_klasses */ false);
756 }
757
758 // Return self, except for abstract classes with exactly 1
759 // implementor. Then return the 1 concrete implementation.
760 Klass *up_cast_abstract();
761
762 // klass name
763 Symbol* name() const { return _name; }
764 void set_name(Symbol* n);
765
766 virtual void release_C_heap_structures(bool release_constant_pool = true);
767
768 public:
769 virtual jint compute_modifier_flags() const = 0;
770
771 // JVMTI support
772 virtual jint jvmti_class_status() const;
773
774 // Printing
775 virtual void print_on(outputStream* st) const;
776
777 virtual void oop_print_value_on(oop obj, outputStream* st);
778 virtual void oop_print_on (oop obj, outputStream* st);
779
780 void print_secondary_supers_on(outputStream* st) const;
781
782 virtual const char* internal_name() const = 0;
783
784 // Verification
785 virtual void verify_on(outputStream* st);
786 void verify() { verify_on(tty); }
787
788 #ifndef PRODUCT
789 bool verify_vtable_index(int index);
790 #endif
791
792 virtual void oop_verify_on(oop obj, outputStream* st);
793
794 // for error reporting
795 static bool is_valid(Klass* k);
796
797 static void on_secondary_supers_verification_failure(Klass* super, Klass* sub, bool linear_result, bool table_result, const char* msg);
798 };
799
800 #endif // SHARE_OOPS_KLASS_HPP