1 /*
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24
25 #ifndef SHARE_PRIMS_JVMTIREDEFINECLASSES_HPP
26 #define SHARE_PRIMS_JVMTIREDEFINECLASSES_HPP
27
28 #include "jvmtifiles/jvmtiEnv.hpp"
29 #include "memory/oopFactory.hpp"
30 #include "memory/resourceArea.hpp"
31 #include "oops/objArrayKlass.hpp"
32 #include "oops/objArrayOop.hpp"
33 #include "runtime/vmOperation.hpp"
34
35 // Introduction:
36 //
37 // The RedefineClasses() API is used to change the definition of one or
38 // more classes. While the API supports redefining more than one class
39 // in a single call, in general, the API is discussed in the context of
40 // changing the definition of a single current class to a single new
41 // class. For clarity, the current class is will always be called
42 // "the_class" and the new class will always be called "scratch_class".
43 //
44 // The name "the_class" is used because there is only one structure
45 // that represents a specific class; redefinition does not replace the
46 // structure, but instead replaces parts of the structure. The name
47 // "scratch_class" is used because the structure that represents the
48 // new definition of a specific class is simply used to carry around
49 // the parts of the new definition until they are used to replace the
50 // appropriate parts in the_class. Once redefinition of a class is
51 // complete, scratch_class is thrown away.
52 //
53 //
54 // Implementation Overview:
55 //
56 // The RedefineClasses() API is mostly a wrapper around the VM op that
57 // does the real work. The work is split in varying degrees between
58 // doit_prologue(), doit() and doit_epilogue().
59 //
60 // 1) doit_prologue() is called by the JavaThread on the way to a
61 // safepoint. It does parameter verification and loads scratch_class
62 // which involves:
63 // - parsing the incoming class definition using the_class' class
64 // loader and security context
65 // - linking scratch_class
66 // - merging constant pools and rewriting bytecodes as needed
67 // for the merged constant pool
68 // - verifying the bytecodes in scratch_class
69 // - setting up the constant pool cache and rewriting bytecodes
70 // as needed to use the cache
71 // - finally, scratch_class is compared to the_class to verify
72 // that it is a valid replacement class
73 // - if everything is good, then scratch_class is saved in an
74 // instance field in the VM operation for the doit() call
75 //
76 // Note: A JavaThread must do the above work.
77 //
78 // 2) doit() is called by the VMThread during a safepoint. It installs
79 // the new class definition(s) which involves:
80 // - retrieving the scratch_class from the instance field in the
81 // VM operation
82 // - house keeping (flushing breakpoints and caches, deoptimizing
83 // dependent compiled code)
84 // - replacing parts in the_class with parts from scratch_class
85 // - adding weak reference(s) to track the obsolete but interesting
86 // parts of the_class
87 // - adjusting constant pool caches and vtables in other classes
88 // that refer to methods in the_class. These adjustments use the
89 // ClassLoaderDataGraph::classes_do() facility which only allows
90 // a helper method to be specified. The interesting parameters
91 // that we would like to pass to the helper method are saved in
92 // static global fields in the VM operation.
93 // - telling the SystemDictionary to notice our changes
94 //
95 // Note: the above work must be done by the VMThread to be safe.
96 //
97 // 3) doit_epilogue() is called by the JavaThread after the VM op
98 // is finished and the safepoint is done. It simply cleans up
99 // memory allocated in doit_prologue() and used in doit().
100 //
101 //
102 // Constant Pool Details:
103 //
104 // When the_class is redefined, we cannot just replace the constant
105 // pool in the_class with the constant pool from scratch_class because
106 // that could confuse obsolete methods that may still be running.
107 // Instead, the constant pool from the_class, old_cp, is merged with
108 // the constant pool from scratch_class, scratch_cp. The resulting
109 // constant pool, merge_cp, replaces old_cp in the_class.
110 //
111 // The key part of any merging algorithm is the entry comparison
112 // function so we have to know the types of entries in a constant pool
113 // in order to merge two of them together. Constant pools can contain
114 // up to 12 different kinds of entries; the JVM_CONSTANT_Unicode entry
115 // is not presently used so we only have to worry about the other 11
116 // entry types. For the purposes of constant pool merging, it is
117 // helpful to know that the 11 entry types fall into 3 different
118 // subtypes: "direct", "indirect" and "double-indirect".
119 //
120 // Direct CP entries contain data and do not contain references to
121 // other CP entries. The following are direct CP entries:
122 // JVM_CONSTANT_{Double,Float,Integer,Long,Utf8}
123 //
124 // Indirect CP entries contain 1 or 2 references to a direct CP entry
125 // and no other data. The following are indirect CP entries:
126 // JVM_CONSTANT_{Class,NameAndType,String}
127 //
128 // Double-indirect CP entries contain two references to indirect CP
129 // entries and no other data. The following are double-indirect CP
130 // entries:
131 // JVM_CONSTANT_{Fieldref,InterfaceMethodref,Methodref}
132 //
133 // When comparing entries between two constant pools, the entry types
134 // are compared first and if they match, then further comparisons are
135 // made depending on the entry subtype. Comparing direct CP entries is
136 // simply a matter of comparing the data associated with each entry.
137 // Comparing both indirect and double-indirect CP entries requires
138 // recursion.
139 //
140 // Fortunately, the recursive combinations are limited because indirect
141 // CP entries can only refer to direct CP entries and double-indirect
142 // CP entries can only refer to indirect CP entries. The following is
143 // an example illustration of the deepest set of indirections needed to
144 // access the data associated with a JVM_CONSTANT_Fieldref entry:
145 //
146 // JVM_CONSTANT_Fieldref {
147 // class_index => JVM_CONSTANT_Class {
148 // name_index => JVM_CONSTANT_Utf8 {
149 // <data-1>
150 // }
151 // }
152 // name_and_type_index => JVM_CONSTANT_NameAndType {
153 // name_index => JVM_CONSTANT_Utf8 {
154 // <data-2>
155 // }
156 // descriptor_index => JVM_CONSTANT_Utf8 {
157 // <data-3>
158 // }
159 // }
160 // }
161 //
162 // The above illustration is not a data structure definition for any
163 // computer language. The curly braces ('{' and '}') are meant to
164 // delimit the context of the "fields" in the CP entry types shown.
165 // Each indirection from the JVM_CONSTANT_Fieldref entry is shown via
166 // "=>", e.g., the class_index is used to indirectly reference a
167 // JVM_CONSTANT_Class entry where the name_index is used to indirectly
168 // reference a JVM_CONSTANT_Utf8 entry which contains the interesting
169 // <data-1>. In order to understand a JVM_CONSTANT_Fieldref entry, we
170 // have to do a total of 5 indirections just to get to the CP entries
171 // that contain the interesting pieces of data and then we have to
172 // fetch the three pieces of data. This means we have to do a total of
173 // (5 + 3) * 2 == 16 dereferences to compare two JVM_CONSTANT_Fieldref
174 // entries.
175 //
176 // Here is the indirection, data and dereference count for each entry
177 // type:
178 //
179 // JVM_CONSTANT_Class 1 indir, 1 data, 2 derefs
180 // JVM_CONSTANT_Double 0 indir, 1 data, 1 deref
181 // JVM_CONSTANT_Fieldref 2 indir, 3 data, 8 derefs
182 // JVM_CONSTANT_Float 0 indir, 1 data, 1 deref
183 // JVM_CONSTANT_Integer 0 indir, 1 data, 1 deref
184 // JVM_CONSTANT_InterfaceMethodref 2 indir, 3 data, 8 derefs
185 // JVM_CONSTANT_Long 0 indir, 1 data, 1 deref
186 // JVM_CONSTANT_Methodref 2 indir, 3 data, 8 derefs
187 // JVM_CONSTANT_NameAndType 1 indir, 2 data, 4 derefs
188 // JVM_CONSTANT_String 1 indir, 1 data, 2 derefs
189 // JVM_CONSTANT_Utf8 0 indir, 1 data, 1 deref
190 //
191 // So different subtypes of CP entries require different amounts of
192 // work for a proper comparison.
193 //
194 // Now that we've talked about the different entry types and how to
195 // compare them we need to get back to merging. This is not a merge in
196 // the "sort -u" sense or even in the "sort" sense. When we merge two
197 // constant pools, we copy all the entries from old_cp to merge_cp,
198 // preserving entry order. Next we append all the unique entries from
199 // scratch_cp to merge_cp and we track the index changes from the
200 // location in scratch_cp to the possibly new location in merge_cp.
201 // When we are done, any obsolete code that is still running that
202 // uses old_cp should not be able to observe any difference if it
203 // were to use merge_cp. As for the new code in scratch_class, it is
204 // modified to use the appropriate index values in merge_cp before it
205 // is used to replace the code in the_class.
206 //
207 // There is one small complication in copying the entries from old_cp
208 // to merge_cp. Two of the CP entry types are special in that they are
209 // lazily resolved. Before explaining the copying complication, we need
210 // to digress into CP entry resolution.
211 //
212 // JVM_CONSTANT_Class entries are present in the class file, but are not
213 // stored in memory as such until they are resolved. The entries are not
214 // resolved unless they are used because resolution is expensive. During class
215 // file parsing the entries are initially stored in memory as
216 // JVM_CONSTANT_ClassIndex and JVM_CONSTANT_StringIndex entries. These special
217 // CP entry types indicate that the JVM_CONSTANT_Class and JVM_CONSTANT_String
218 // entries have been parsed, but the index values in the entries have not been
219 // validated. After the entire constant pool has been parsed, the index
220 // values can be validated and then the entries are converted into
221 // JVM_CONSTANT_UnresolvedClass and JVM_CONSTANT_String
222 // entries. During this conversion process, the UTF8 values that are
223 // indirectly referenced by the JVM_CONSTANT_ClassIndex and
224 // JVM_CONSTANT_StringIndex entries are changed into Symbol*s and the
225 // entries are modified to refer to the Symbol*s. This optimization
226 // eliminates one level of indirection for those two CP entry types and
227 // gets the entries ready for verification. Verification expects to
228 // find JVM_CONSTANT_UnresolvedClass but not JVM_CONSTANT_Class entries.
229 //
230 // Now we can get back to the copying complication. When we copy
231 // entries from old_cp to merge_cp, we have to revert any
232 // JVM_CONSTANT_Class entries to JVM_CONSTANT_UnresolvedClass entries
233 // or verification will fail.
234 //
235 // It is important to explicitly state that the merging algorithm
236 // effectively unresolves JVM_CONSTANT_Class entries that were in the
237 // old_cp when they are changed into JVM_CONSTANT_UnresolvedClass
238 // entries in the merge_cp. This is done both to make verification
239 // happy and to avoid adding more brittleness between RedefineClasses
240 // and the constant pool cache. By allowing the constant pool cache
241 // implementation to (re)resolve JVM_CONSTANT_UnresolvedClass entries
242 // into JVM_CONSTANT_Class entries, we avoid having to embed knowledge
243 // about those algorithms in RedefineClasses.
244 //
245 // Appending unique entries from scratch_cp to merge_cp is straight
246 // forward for direct CP entries and most indirect CP entries. For the
247 // indirect CP entry type JVM_CONSTANT_NameAndType and for the double-
248 // indirect CP entry types, the presence of more than one piece of
249 // interesting data makes appending the entries more complicated.
250 //
251 // For the JVM_CONSTANT_{Double,Float,Integer,Long,Utf8} entry types,
252 // the entry is simply copied from scratch_cp to the end of merge_cp.
253 // If the index in scratch_cp is different than the destination index
254 // in merge_cp, then the change in index value is tracked.
255 //
256 // Note: the above discussion for the direct CP entries also applies
257 // to the JVM_CONSTANT_UnresolvedClass entry types.
258 //
259 // For the JVM_CONSTANT_Class entry types, since there is only
260 // one data element at the end of the recursion, we know that we have
261 // either one or two unique entries. If the JVM_CONSTANT_Utf8 entry is
262 // unique then it is appended to merge_cp before the current entry.
263 // If the JVM_CONSTANT_Utf8 entry is not unique, then the current entry
264 // is updated to refer to the duplicate entry in merge_cp before it is
265 // appended to merge_cp. Again, any changes in index values are tracked
266 // as needed.
267 //
268 // Note: the above discussion for JVM_CONSTANT_Class entry
269 // types is theoretical. Since those entry types have already been
270 // optimized into JVM_CONSTANT_UnresolvedClass entry types,
271 // they are handled as direct CP entries.
272 //
273 // For the JVM_CONSTANT_NameAndType entry type, since there are two
274 // data elements at the end of the recursions, we know that we have
275 // between one and three unique entries. Any unique JVM_CONSTANT_Utf8
276 // entries are appended to merge_cp before the current entry. For any
277 // JVM_CONSTANT_Utf8 entries that are not unique, the current entry is
278 // updated to refer to the duplicate entry in merge_cp before it is
279 // appended to merge_cp. Again, any changes in index values are tracked
280 // as needed.
281 //
282 // For the JVM_CONSTANT_{Fieldref,InterfaceMethodref,Methodref} entry
283 // types, since there are two indirect CP entries and three data
284 // elements at the end of the recursions, we know that we have between
285 // one and six unique entries. See the JVM_CONSTANT_Fieldref diagram
286 // above for an example of all six entries. The uniqueness algorithm
287 // for the JVM_CONSTANT_Class and JVM_CONSTANT_NameAndType entries is
288 // covered above. Any unique entries are appended to merge_cp before
289 // the current entry. For any entries that are not unique, the current
290 // entry is updated to refer to the duplicate entry in merge_cp before
291 // it is appended to merge_cp. Again, any changes in index values are
292 // tracked as needed.
293 //
294 //
295 // Other Details:
296 //
297 // Details for other parts of RedefineClasses need to be written.
298 // This is a placeholder section.
299 //
300 //
301 // Open Issues (in no particular order):
302 //
303 // - How do we serialize the RedefineClasses() API without deadlocking?
304 //
305 // - GenerateOopMap::rewrite_load_or_store() has a comment in its
306 // (indirect) use of the Relocator class that the max instruction
307 // size is 4 bytes. goto_w and jsr_w are 5 bytes and wide/iinc is
308 // 6 bytes. Perhaps Relocator only needs a 4 byte buffer to do
309 // what it does to the bytecodes. More investigation is needed.
310 //
311 // - How do we know if redefine_single_class() and the guts of
312 // InstanceKlass are out of sync? I don't think this can be
313 // automated, but we should probably order the work in
314 // redefine_single_class() to match the order of field
315 // definitions in InstanceKlass. We also need to add some
316 // comments about keeping things in sync.
317 //
318 // - set_new_constant_pool() is huge and we should consider refactoring
319 // it into smaller chunks of work.
320 //
321 // - The exception table update code in set_new_constant_pool() defines
322 // const values that are also defined in a local context elsewhere.
323 // The same literal values are also used in elsewhere. We need to
324 // coordinate a cleanup of these constants with Runtime.
325 //
326
327 struct JvmtiCachedClassFileData {
328 jint length;
329 unsigned char data[1];
330 };
331
332 class VM_RedefineClasses: public VM_Operation {
333 private:
334 // These static fields are needed by ClassLoaderDataGraph::classes_do()
335 // facility and the CheckClass and AdjustAndCleanMetadata helpers.
336 static Array<Method*>* _old_methods;
337 static Array<Method*>* _new_methods;
338 static Method** _matching_old_methods;
339 static Method** _matching_new_methods;
340 static Method** _deleted_methods;
341 static Method** _added_methods;
342 static int _matching_methods_length;
343 static int _deleted_methods_length;
344 static int _added_methods_length;
345 static bool _has_redefined_Object;
346 static bool _has_null_class_loader;
347
348 // Used by JFR to group class redefininition events together.
349 static u8 _id_counter;
350
351 // The instance fields are used to pass information from
352 // doit_prologue() to doit() and doit_epilogue().
353 Klass* _the_class;
354 jint _class_count;
355 const jvmtiClassDefinition *_class_defs; // ptr to _class_count defs
356
357 // This operation is used by both RedefineClasses and
358 // RetransformClasses. Indicate which.
359 JvmtiClassLoadKind _class_load_kind;
360
361 // _index_map_count is just an optimization for knowing if
362 // _index_map_p contains any entries.
363 int _index_map_count;
364 intArray * _index_map_p;
365
366 // _operands_index_map_count is just an optimization for knowing if
367 // _operands_index_map_p contains any entries.
368 int _operands_cur_length;
369 int _operands_index_map_count;
370 intArray * _operands_index_map_p;
371
372 // ptr to _class_count scratch_classes
373 InstanceKlass** _scratch_classes;
374 jvmtiError _res;
375
376 // Set if any of the InstanceKlasses have entries in the ResolvedMethodTable
377 // to avoid walking after redefinition if the redefined classes do not
378 // have any entries.
379 bool _any_class_has_resolved_methods;
380
381 // Performance measurement support. These timers do not cover all
382 // the work done for JVM/TI RedefineClasses() but they do cover
383 // the heavy lifting.
384 elapsedTimer _timer_rsc_phase1;
385 elapsedTimer _timer_rsc_phase2;
386 elapsedTimer _timer_vm_op_doit;
387 elapsedTimer _timer_vm_op_prologue;
388
389 // Redefinition id used by JFR
390 u8 _id;
391
392 // These routines are roughly in call order unless otherwise noted.
393
394 // Load the caller's new class definition(s) into _scratch_classes.
395 // Constant pool merging work is done here as needed. Also calls
396 // compare_and_normalize_class_versions() to verify the class
397 // definition(s).
398 jvmtiError load_new_class_versions();
399
400 // Verify that the caller provided class definition(s) that meet
401 // the restrictions of RedefineClasses. Normalize the order of
402 // overloaded methods as needed.
403 jvmtiError compare_and_normalize_class_versions(
404 InstanceKlass* the_class, InstanceKlass* scratch_class);
405
406 // Figure out which new methods match old methods in name and signature,
407 // which methods have been added, and which are no longer present
408 void compute_added_deleted_matching_methods();
409
410 // Change jmethodIDs to point to the new methods
411 void update_jmethod_ids();
412
413 // In addition to marking methods as old and/or obsolete, this routine
414 // counts the number of methods that are EMCP (Equivalent Module Constant Pool).
415 int check_methods_and_mark_as_obsolete();
416 void transfer_old_native_function_registrations(InstanceKlass* the_class);
417
418 // Install the redefinition of a class
419 void redefine_single_class(Thread* current, jclass the_jclass,
420 InstanceKlass* scratch_class_oop);
421
422 void swap_annotations(InstanceKlass* new_class,
423 InstanceKlass* scratch_class);
424
425 // Increment the classRedefinedCount field in the specific InstanceKlass
426 // and in all direct and indirect subclasses.
427 void increment_class_counter(InstanceKlass* ik);
428
429 // Support for constant pool merging (these routines are in alpha order):
430 void append_entry(const constantPoolHandle& scratch_cp, int scratch_i,
431 constantPoolHandle *merge_cp_p, int *merge_cp_length_p);
432 void append_operand(const constantPoolHandle& scratch_cp, int scratch_bootstrap_spec_index,
433 constantPoolHandle *merge_cp_p, int *merge_cp_length_p);
434 void finalize_operands_merge(const constantPoolHandle& merge_cp, TRAPS);
435 u2 find_or_append_indirect_entry(const constantPoolHandle& scratch_cp, int scratch_i,
436 constantPoolHandle *merge_cp_p, int *merge_cp_length_p);
437 int find_or_append_operand(const constantPoolHandle& scratch_cp, int scratch_bootstrap_spec_index,
438 constantPoolHandle *merge_cp_p, int *merge_cp_length_p);
439 u2 find_new_index(int old_index);
440 int find_new_operand_index(int old_bootstrap_spec_index);
441 void map_index(const constantPoolHandle& scratch_cp, int old_index, int new_index);
442 void map_operand_index(int old_bootstrap_spec_index, int new_bootstrap_spec_index);
443 bool merge_constant_pools(const constantPoolHandle& old_cp,
444 const constantPoolHandle& scratch_cp, constantPoolHandle *merge_cp_p,
445 int *merge_cp_length_p, TRAPS);
446 jvmtiError merge_cp_and_rewrite(InstanceKlass* the_class,
447 InstanceKlass* scratch_class, TRAPS);
448 u2 rewrite_cp_ref_in_annotation_data(
449 AnnotationArray* annotations_typeArray, int &byte_i_ref,
450 const char * trace_mesg);
451 bool rewrite_cp_refs(InstanceKlass* scratch_class);
452 bool rewrite_cp_refs_in_annotation_struct(
453 AnnotationArray* class_annotations, int &byte_i_ref);
454 bool rewrite_cp_refs_in_annotations_typeArray(
455 AnnotationArray* annotations_typeArray, int &byte_i_ref);
456 bool rewrite_cp_refs_in_class_annotations(InstanceKlass* scratch_class);
457 bool rewrite_cp_refs_in_element_value(
458 AnnotationArray* class_annotations, int &byte_i_ref);
459 bool rewrite_cp_refs_in_type_annotations_typeArray(
460 AnnotationArray* type_annotations_typeArray, int &byte_i_ref,
461 const char * location_mesg);
462 bool rewrite_cp_refs_in_type_annotation_struct(
463 AnnotationArray* type_annotations_typeArray, int &byte_i_ref,
464 const char * location_mesg);
465 bool skip_type_annotation_target(
466 AnnotationArray* type_annotations_typeArray, int &byte_i_ref,
467 const char * location_mesg);
468 bool skip_type_annotation_type_path(
469 AnnotationArray* type_annotations_typeArray, int &byte_i_ref);
470 bool rewrite_cp_refs_in_fields_annotations(InstanceKlass* scratch_class);
471 bool rewrite_cp_refs_in_nest_attributes(InstanceKlass* scratch_class);
472 bool rewrite_cp_refs_in_record_attribute(InstanceKlass* scratch_class);
473 bool rewrite_cp_refs_in_permitted_subclasses_attribute(InstanceKlass* scratch_class);
474
475 void rewrite_cp_refs_in_method(methodHandle method,
476 methodHandle * new_method_p, TRAPS);
477 bool rewrite_cp_refs_in_methods(InstanceKlass* scratch_class);
478
479 bool rewrite_cp_refs_in_methods_annotations(InstanceKlass* scratch_class);
480 bool rewrite_cp_refs_in_methods_default_annotations(InstanceKlass* scratch_class);
481 bool rewrite_cp_refs_in_methods_parameter_annotations(InstanceKlass* scratch_class);
482 bool rewrite_cp_refs_in_class_type_annotations(InstanceKlass* scratch_class);
483 bool rewrite_cp_refs_in_fields_type_annotations(InstanceKlass* scratch_class);
484 bool rewrite_cp_refs_in_methods_type_annotations(InstanceKlass* scratch_class);
485
486 void rewrite_cp_refs_in_stack_map_table(const methodHandle& method);
487 void rewrite_cp_refs_in_verification_type_info(
488 address& stackmap_addr_ref, address stackmap_end, u2 frame_i,
489 u1 frame_size);
490 void set_new_constant_pool(ClassLoaderData* loader_data,
491 InstanceKlass* scratch_class,
492 constantPoolHandle scratch_cp, int scratch_cp_length, TRAPS);
493
494 void flush_dependent_code();
495
496 // lock classes to redefine since constant pool merging isn't thread safe.
497 void lock_classes();
498 void unlock_classes();
499
500 u8 next_id();
501
502 static void dump_methods();
503
504 // Check that there are no old or obsolete methods
505 class CheckClass : public KlassClosure {
506 Thread* _thread;
507 public:
508 CheckClass(Thread* t) : _thread(t) {}
509 void do_klass(Klass* k);
510 };
511
512 // Unevolving classes may point to methods of the_class directly
513 // from their constant pool caches, itables, and/or vtables. We
514 // use the ClassLoaderDataGraph::classes_do() facility and this helper
515 // to fix up these pointers and clean MethodData out.
516 class AdjustAndCleanMetadata : public KlassClosure {
517 Thread* _thread;
518 public:
519 AdjustAndCleanMetadata(Thread* t) : _thread(t) {}
520 void do_klass(Klass* k);
521 };
522
523 public:
524 VM_RedefineClasses(jint class_count,
525 const jvmtiClassDefinition *class_defs,
526 JvmtiClassLoadKind class_load_kind);
527 VMOp_Type type() const { return VMOp_RedefineClasses; }
528 bool doit_prologue();
529 void doit();
530 void doit_epilogue();
531
532 bool allow_nested_vm_operations() const { return true; }
533 jvmtiError check_error() { return _res; }
534 u8 id() { return _id; }
535
536 // Modifiable test must be shared between IsModifiableClass query
537 // and redefine implementation
538 static bool is_modifiable_class(oop klass_mirror);
539
540 static jint get_cached_class_file_len(JvmtiCachedClassFileData *cache) {
541 return cache == nullptr ? 0 : cache->length;
542 }
543 static unsigned char * get_cached_class_file_bytes(JvmtiCachedClassFileData *cache) {
544 return cache == nullptr ? nullptr : cache->data;
545 }
546
547 // Error printing
548 void print_on_error(outputStream* st) const;
549 };
550 #endif // SHARE_PRIMS_JVMTIREDEFINECLASSES_HPP