1 /*
   2  * Copyright (c) 2012, 2018, 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.
  18  *
  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.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "classfile/bytecodeAssembler.hpp"
  27 #include "classfile/defaultMethods.hpp"
  28 #include "classfile/symbolTable.hpp"
  29 #include "memory/allocation.hpp"
  30 #include "memory/metadataFactory.hpp"
  31 #include "memory/resourceArea.hpp"
  32 #include "runtime/signature.hpp"
  33 #include "runtime/thread.hpp"
  34 #include "oops/instanceKlass.hpp"
  35 #include "oops/klass.hpp"
  36 #include "oops/method.hpp"
  37 #include "utilities/accessFlags.hpp"
  38 #include "utilities/exceptions.hpp"
  39 #include "utilities/ostream.hpp"
  40 #include "utilities/pair.hpp"
  41 #include "utilities/resourceHash.hpp"
  42 
  43 typedef enum { QUALIFIED, DISQUALIFIED } QualifiedState;
  44 
  45 // Because we use an iterative algorithm when iterating over the type
  46 // hierarchy, we can't use traditional scoped objects which automatically do
  47 // cleanup in the destructor when the scope is exited.  PseudoScope (and
  48 // PseudoScopeMark) provides a similar functionality, but for when you want a
  49 // scoped object in non-stack memory (such as in resource memory, as we do
  50 // here).  You've just got to remember to call 'destroy()' on the scope when
  51 // leaving it (and marks have to be explicitly added).
  52 class PseudoScopeMark : public ResourceObj {
  53  public:
  54   virtual void destroy() = 0;
  55 };
  56 
  57 class PseudoScope : public ResourceObj {
  58  private:
  59   GrowableArray<PseudoScopeMark*> _marks;
  60  public:
  61 
  62   static PseudoScope* cast(void* data) {
  63     return static_cast<PseudoScope*>(data);
  64   }
  65 
  66   void add_mark(PseudoScopeMark* psm) {
  67    _marks.append(psm);
  68   }
  69 
  70   void destroy() {
  71     for (int i = 0; i < _marks.length(); ++i) {
  72       _marks.at(i)->destroy();
  73     }
  74   }
  75 };
  76 
  77 #ifndef PRODUCT
  78 static void print_slot(outputStream* str, Symbol* name, Symbol* signature) {
  79   ResourceMark rm;
  80   str->print("%s%s", name->as_C_string(), signature->as_C_string());
  81 }
  82 
  83 static void print_method(outputStream* str, Method* mo, bool with_class=true) {
  84   ResourceMark rm;
  85   if (with_class) {
  86     str->print("%s.", mo->klass_name()->as_C_string());
  87   }
  88   print_slot(str, mo->name(), mo->signature());
  89 }
  90 #endif // ndef PRODUCT
  91 
  92 /**
  93  * Perform a depth-first iteration over the class hierarchy, applying
  94  * algorithmic logic as it goes.
  95  *
  96  * This class is one half of the inheritance hierarchy analysis mechanism.
  97  * It is meant to be used in conjunction with another class, the algorithm,
  98  * which is indicated by the ALGO template parameter.  This class can be
  99  * paired with any algorithm class that provides the required methods.
 100  *
 101  * This class contains all the mechanics for iterating over the class hierarchy
 102  * starting at a particular root, without recursing (thus limiting stack growth
 103  * from this point).  It visits each superclass (if present) and superinterface
 104  * in a depth-first manner, with callbacks to the ALGO class as each class is
 105  * encountered (visit()), The algorithm can cut-off further exploration of a
 106  * particular branch by returning 'false' from a visit() call.
 107  *
 108  * The ALGO class, must provide a visit() method, which each of which will be
 109  * called once for each node in the inheritance tree during the iteration.  In
 110  * addition, it can provide a memory block via new_node_data(InstanceKlass*),
 111  * which it can use for node-specific storage (and access via the
 112  * current_data() and data_at_depth(int) methods).
 113  *
 114  * Bare minimum needed to be an ALGO class:
 115  * class Algo : public HierarchyVisitor<Algo> {
 116  *   void* new_node_data(InstanceKlass* cls) { return NULL; }
 117  *   void free_node_data(void* data) { return; }
 118  *   bool visit() { return true; }
 119  * };
 120  */
 121 template <class ALGO>
 122 class HierarchyVisitor : StackObj {
 123  private:
 124 
 125   class Node : public ResourceObj {
 126    public:
 127     InstanceKlass* _class;
 128     bool _super_was_visited;
 129     int _interface_index;
 130     void* _algorithm_data;
 131 
 132     Node(InstanceKlass* cls, void* data, bool visit_super)
 133         : _class(cls), _super_was_visited(!visit_super),
 134           _interface_index(0), _algorithm_data(data) {}
 135 
 136     int number_of_interfaces() { return _class->local_interfaces()->length(); }
 137     int interface_index() { return _interface_index; }
 138     void set_super_visited() { _super_was_visited = true; }
 139     void increment_visited_interface() { ++_interface_index; }
 140     void set_all_interfaces_visited() {
 141       _interface_index = number_of_interfaces();
 142     }
 143     bool has_visited_super() { return _super_was_visited; }
 144     bool has_visited_all_interfaces() {
 145       return interface_index() >= number_of_interfaces();
 146     }
 147     InstanceKlass* interface_at(int index) {
 148       return InstanceKlass::cast(_class->local_interfaces()->at(index));
 149     }
 150     InstanceKlass* next_super() { return _class->java_super(); }
 151     InstanceKlass* next_interface() {
 152       return interface_at(interface_index());
 153     }
 154   };
 155 
 156   bool _cancelled;
 157   GrowableArray<Node*> _path;
 158 
 159   Node* current_top() const { return _path.top(); }
 160   bool has_more_nodes() const { return !_path.is_empty(); }
 161   void push(InstanceKlass* cls, void* data) {
 162     assert(cls != NULL, "Requires a valid instance class");
 163     Node* node = new Node(cls, data, has_super(cls));
 164     _path.push(node);
 165   }
 166   void pop() { _path.pop(); }
 167 
 168   void reset_iteration() {
 169     _cancelled = false;
 170     _path.clear();
 171   }
 172   bool is_cancelled() const { return _cancelled; }
 173 
 174   // This code used to skip interface classes because their only
 175   // superclass was j.l.Object which would be also covered by class
 176   // superclass hierarchy walks. Now that the starting point can be
 177   // an interface, we must ensure we catch j.l.Object as the super.
 178   static bool has_super(InstanceKlass* cls) {
 179     return cls->super() != NULL;
 180   }
 181 
 182   Node* node_at_depth(int i) const {
 183     return (i >= _path.length()) ? NULL : _path.at(_path.length() - i - 1);
 184   }
 185 
 186  protected:
 187 
 188   // Accessors available to the algorithm
 189   int current_depth() const { return _path.length() - 1; }
 190 
 191   InstanceKlass* class_at_depth(int i) {
 192     Node* n = node_at_depth(i);
 193     return n == NULL ? NULL : n->_class;
 194   }
 195   InstanceKlass* current_class() { return class_at_depth(0); }
 196 
 197   void* data_at_depth(int i) {
 198     Node* n = node_at_depth(i);
 199     return n == NULL ? NULL : n->_algorithm_data;
 200   }
 201   void* current_data() { return data_at_depth(0); }
 202 
 203   void cancel_iteration() { _cancelled = true; }
 204 
 205  public:
 206 
 207   void run(InstanceKlass* root) {
 208     ALGO* algo = static_cast<ALGO*>(this);
 209 
 210     reset_iteration();
 211 
 212     void* algo_data = algo->new_node_data(root);
 213     push(root, algo_data);
 214     bool top_needs_visit = true;
 215 
 216     do {
 217       Node* top = current_top();
 218       if (top_needs_visit) {
 219         if (algo->visit() == false) {
 220           // algorithm does not want to continue along this path.  Arrange
 221           // it so that this state is immediately popped off the stack
 222           top->set_super_visited();
 223           top->set_all_interfaces_visited();
 224         }
 225         top_needs_visit = false;
 226       }
 227 
 228       if (top->has_visited_super() && top->has_visited_all_interfaces()) {
 229         algo->free_node_data(top->_algorithm_data);
 230         pop();
 231       } else {
 232         InstanceKlass* next = NULL;
 233         if (top->has_visited_super() == false) {
 234           next = top->next_super();
 235           top->set_super_visited();
 236         } else {
 237           next = top->next_interface();
 238           top->increment_visited_interface();
 239         }
 240         assert(next != NULL, "Otherwise we shouldn't be here");
 241         algo_data = algo->new_node_data(next);
 242         push(next, algo_data);
 243         top_needs_visit = true;
 244       }
 245     } while (!is_cancelled() && has_more_nodes());
 246   }
 247 };
 248 
 249 #ifndef PRODUCT
 250 class PrintHierarchy : public HierarchyVisitor<PrintHierarchy> {
 251  public:
 252 
 253   bool visit() {
 254     InstanceKlass* cls = current_class();
 255     streamIndentor si(tty, current_depth() * 2);
 256     tty->indent().print_cr("%s", cls->name()->as_C_string());
 257     return true;
 258   }
 259 
 260   void* new_node_data(InstanceKlass* cls) { return NULL; }
 261   void free_node_data(void* data) { return; }
 262 };
 263 #endif // ndef PRODUCT
 264 
 265 // Used to register InstanceKlass objects and all related metadata structures
 266 // (Methods, ConstantPools) as "in-use" by the current thread so that they can't
 267 // be deallocated by class redefinition while we're using them.  The classes are
 268 // de-registered when this goes out of scope.
 269 //
 270 // Once a class is registered, we need not bother with methodHandles or
 271 // constantPoolHandles for it's associated metadata.
 272 class KeepAliveRegistrar : public StackObj {
 273  private:
 274   Thread* _thread;
 275   GrowableArray<ConstantPool*> _keep_alive;
 276 
 277  public:
 278   KeepAliveRegistrar(Thread* thread) : _thread(thread), _keep_alive(20) {
 279     assert(thread == Thread::current(), "Must be current thread");
 280   }
 281 
 282   ~KeepAliveRegistrar() {
 283     for (int i = _keep_alive.length() - 1; i >= 0; --i) {
 284       ConstantPool* cp = _keep_alive.at(i);
 285       int idx = _thread->metadata_handles()->find_from_end(cp);
 286       assert(idx > 0, "Must be in the list");
 287       _thread->metadata_handles()->remove_at(idx);
 288     }
 289   }
 290 
 291   // Register a class as 'in-use' by the thread.  It's fine to register a class
 292   // multiple times (though perhaps inefficient)
 293   void register_class(InstanceKlass* ik) {
 294     ConstantPool* cp = ik->constants();
 295     _keep_alive.push(cp);
 296     _thread->metadata_handles()->push(cp);
 297   }
 298 };
 299 
 300 class KeepAliveVisitor : public HierarchyVisitor<KeepAliveVisitor> {
 301  private:
 302   KeepAliveRegistrar* _registrar;
 303 
 304  public:
 305   KeepAliveVisitor(KeepAliveRegistrar* registrar) : _registrar(registrar) {}
 306 
 307   void* new_node_data(InstanceKlass* cls) { return NULL; }
 308   void free_node_data(void* data) { return; }
 309 
 310   bool visit() {
 311     _registrar->register_class(current_class());
 312     return true;
 313   }
 314 };
 315 
 316 
 317 // A method family contains a set of all methods that implement a single
 318 // erased method. As members of the set are collected while walking over the
 319 // hierarchy, they are tagged with a qualification state.  The qualification
 320 // state for an erased method is set to disqualified if there exists a path
 321 // from the root of hierarchy to the method that contains an interleaving
 322 // erased method defined in an interface.
 323 
 324 class MethodFamily : public ResourceObj {
 325  private:
 326 
 327   GrowableArray<Pair<Method*,QualifiedState> > _members;
 328   ResourceHashtable<Method*, int> _member_index;
 329 
 330   Method* _selected_target;  // Filled in later, if a unique target exists
 331   Symbol* _exception_message; // If no unique target is found
 332   Symbol* _exception_name;    // If no unique target is found
 333 
 334   bool contains_method(Method* method) {
 335     int* lookup = _member_index.get(method);
 336     return lookup != NULL;
 337   }
 338 
 339   void add_method(Method* method, QualifiedState state) {
 340     Pair<Method*,QualifiedState> entry(method, state);
 341     _member_index.put(method, _members.length());
 342     _members.append(entry);
 343   }
 344 
 345   void disqualify_method(Method* method) {
 346     int* index = _member_index.get(method);
 347     guarantee(index != NULL && *index >= 0 && *index < _members.length(), "bad index");
 348     _members.at(*index).second = DISQUALIFIED;
 349   }
 350 
 351   Symbol* generate_no_defaults_message(TRAPS) const;
 352   Symbol* generate_method_message(Symbol *klass_name, Method* method, TRAPS) const;
 353   Symbol* generate_conflicts_message(GrowableArray<Method*>* methods, TRAPS) const;
 354 
 355  public:
 356 
 357   MethodFamily()
 358       : _selected_target(NULL), _exception_message(NULL), _exception_name(NULL) {}
 359 
 360   void set_target_if_empty(Method* m) {
 361     if (_selected_target == NULL && !m->is_overpass()) {
 362       _selected_target = m;
 363     }
 364   }
 365 
 366   void record_qualified_method(Method* m) {
 367     // If the method already exists in the set as qualified, this operation is
 368     // redundant.  If it already exists as disqualified, then we leave it as
 369     // disqualfied.  Thus we only add to the set if it's not already in the
 370     // set.
 371     if (!contains_method(m)) {
 372       add_method(m, QUALIFIED);
 373     }
 374   }
 375 
 376   void record_disqualified_method(Method* m) {
 377     // If not in the set, add it as disqualified.  If it's already in the set,
 378     // then set the state to disqualified no matter what the previous state was.
 379     if (!contains_method(m)) {
 380       add_method(m, DISQUALIFIED);
 381     } else {
 382       disqualify_method(m);
 383     }
 384   }
 385 
 386   bool has_target() const { return _selected_target != NULL; }
 387   bool throws_exception() { return _exception_message != NULL; }
 388 
 389   Method* get_selected_target() { return _selected_target; }
 390   Symbol* get_exception_message() { return _exception_message; }
 391   Symbol* get_exception_name() { return _exception_name; }
 392 
 393   // Either sets the target or the exception error message
 394   void determine_target(InstanceKlass* root, TRAPS) {
 395     if (has_target() || throws_exception()) {
 396       return;
 397     }
 398 
 399     // Qualified methods are maximally-specific methods
 400     // These include public, instance concrete (=default) and abstract methods
 401     GrowableArray<Method*> qualified_methods;
 402     int num_defaults = 0;
 403     int default_index = -1;
 404     int qualified_index = -1;
 405     for (int i = 0; i < _members.length(); ++i) {
 406       Pair<Method*,QualifiedState> entry = _members.at(i);
 407       if (entry.second == QUALIFIED) {
 408         qualified_methods.append(entry.first);
 409         qualified_index++;
 410         if (entry.first->is_default_method()) {
 411           num_defaults++;
 412           default_index = qualified_index;
 413 
 414         }
 415       }
 416     }
 417 
 418     if (num_defaults == 0) {
 419       // If the root klass has a static method with matching name and signature
 420       // then do not generate an overpass method because it will hide the
 421       // static method during resolution.
 422       if (qualified_methods.length() == 0) {
 423         _exception_message = generate_no_defaults_message(CHECK);
 424       } else {
 425         assert(root != NULL, "Null root class");
 426         _exception_message = generate_method_message(root->name(), qualified_methods.at(0), CHECK);
 427       }
 428       _exception_name = vmSymbols::java_lang_AbstractMethodError();
 429 
 430     // If only one qualified method is default, select that
 431     } else if (num_defaults == 1) {
 432         _selected_target = qualified_methods.at(default_index);
 433 
 434     } else if (num_defaults > 1) {
 435       _exception_message = generate_conflicts_message(&qualified_methods,CHECK);
 436       _exception_name = vmSymbols::java_lang_IncompatibleClassChangeError();
 437       if (TraceDefaultMethods) {
 438         _exception_message->print_value_on(tty);
 439         tty->cr();
 440       }
 441     }
 442   }
 443 
 444   bool contains_signature(Symbol* query) {
 445     for (int i = 0; i < _members.length(); ++i) {
 446       if (query == _members.at(i).first->signature()) {
 447         return true;
 448       }
 449     }
 450     return false;
 451   }
 452 
 453 #ifndef PRODUCT
 454   void print_sig_on(outputStream* str, Symbol* signature, int indent) const {
 455     streamIndentor si(str, indent * 2);
 456 
 457     str->indent().print_cr("Logical Method %s:", signature->as_C_string());
 458 
 459     streamIndentor si2(str);
 460     for (int i = 0; i < _members.length(); ++i) {
 461       str->indent();
 462       print_method(str, _members.at(i).first);
 463       if (_members.at(i).second == DISQUALIFIED) {
 464         str->print(" (disqualified)");
 465       }
 466       str->cr();
 467     }
 468 
 469     if (_selected_target != NULL) {
 470       print_selected(str, 1);
 471     }
 472   }
 473 
 474   void print_selected(outputStream* str, int indent) const {
 475     assert(has_target(), "Should be called otherwise");
 476     streamIndentor si(str, indent * 2);
 477     str->indent().print("Selected method: ");
 478     print_method(str, _selected_target);
 479     Klass* method_holder = _selected_target->method_holder();
 480     if (!method_holder->is_interface()) {
 481       tty->print(" : in superclass");
 482     }
 483     str->cr();
 484   }
 485 
 486   void print_exception(outputStream* str, int indent) {
 487     assert(throws_exception(), "Should be called otherwise");
 488     assert(_exception_name != NULL, "exception_name should be set");
 489     streamIndentor si(str, indent * 2);
 490     str->indent().print_cr("%s: %s", _exception_name->as_C_string(), _exception_message->as_C_string());
 491   }
 492 #endif // ndef PRODUCT
 493 };
 494 
 495 Symbol* MethodFamily::generate_no_defaults_message(TRAPS) const {
 496   return SymbolTable::new_symbol("No qualifying defaults found", THREAD);
 497 }
 498 
 499 Symbol* MethodFamily::generate_method_message(Symbol *klass_name, Method* method, TRAPS) const {
 500   stringStream ss;
 501   ss.print("Method ");
 502   Symbol* name = method->name();
 503   Symbol* signature = method->signature();
 504   ss.write((const char*)klass_name->bytes(), klass_name->utf8_length());
 505   ss.print(".");
 506   ss.write((const char*)name->bytes(), name->utf8_length());
 507   ss.write((const char*)signature->bytes(), signature->utf8_length());
 508   ss.print(" is abstract");
 509   return SymbolTable::new_symbol(ss.base(), (int)ss.size(), CHECK_NULL);
 510 }
 511 
 512 Symbol* MethodFamily::generate_conflicts_message(GrowableArray<Method*>* methods, TRAPS) const {
 513   stringStream ss;
 514   ss.print("Conflicting default methods:");
 515   for (int i = 0; i < methods->length(); ++i) {
 516     Method* method = methods->at(i);
 517     Symbol* klass = method->klass_name();
 518     Symbol* name = method->name();
 519     ss.print(" ");
 520     ss.write((const char*)klass->bytes(), klass->utf8_length());
 521     ss.print(".");
 522     ss.write((const char*)name->bytes(), name->utf8_length());
 523   }
 524   return SymbolTable::new_symbol(ss.base(), (int)ss.size(), CHECK_NULL);
 525 }
 526 
 527 
 528 class StateRestorer;
 529 
 530 // StatefulMethodFamily is a wrapper around a MethodFamily that maintains the
 531 // qualification state during hierarchy visitation, and applies that state
 532 // when adding members to the MethodFamily
 533 class StatefulMethodFamily : public ResourceObj {
 534   friend class StateRestorer;
 535  private:
 536   QualifiedState _qualification_state;
 537 
 538   void set_qualification_state(QualifiedState state) {
 539     _qualification_state = state;
 540   }
 541 
 542  protected:
 543   MethodFamily* _method_family;
 544 
 545  public:
 546   StatefulMethodFamily() {
 547    _method_family = new MethodFamily();
 548    _qualification_state = QUALIFIED;
 549   }
 550 
 551   StatefulMethodFamily(MethodFamily* mf) {
 552    _method_family = mf;
 553    _qualification_state = QUALIFIED;
 554   }
 555 
 556   void set_target_if_empty(Method* m) { _method_family->set_target_if_empty(m); }
 557 
 558   MethodFamily* get_method_family() { return _method_family; }
 559 
 560   StateRestorer* record_method_and_dq_further(Method* mo);
 561 };
 562 
 563 class StateRestorer : public PseudoScopeMark {
 564  private:
 565   StatefulMethodFamily* _method;
 566   QualifiedState _state_to_restore;
 567  public:
 568   StateRestorer(StatefulMethodFamily* dm, QualifiedState state)
 569       : _method(dm), _state_to_restore(state) {}
 570   ~StateRestorer() { destroy(); }
 571   void restore_state() { _method->set_qualification_state(_state_to_restore); }
 572   virtual void destroy() { restore_state(); }
 573 };
 574 
 575 StateRestorer* StatefulMethodFamily::record_method_and_dq_further(Method* mo) {
 576   StateRestorer* mark = new StateRestorer(this, _qualification_state);
 577   if (_qualification_state == QUALIFIED) {
 578     _method_family->record_qualified_method(mo);
 579   } else {
 580     _method_family->record_disqualified_method(mo);
 581   }
 582   // Everything found "above"??? this method in the hierarchy walk is set to
 583   // disqualified
 584   set_qualification_state(DISQUALIFIED);
 585   return mark;
 586 }
 587 
 588 // Represents a location corresponding to a vtable slot for methods that
 589 // neither the class nor any of it's ancestors provide an implementaion.
 590 // Default methods may be present to fill this slot.
 591 class EmptyVtableSlot : public ResourceObj {
 592  private:
 593   Symbol* _name;
 594   Symbol* _signature;
 595   int _size_of_parameters;
 596   MethodFamily* _binding;
 597 
 598  public:
 599   EmptyVtableSlot(Method* method)
 600       : _name(method->name()), _signature(method->signature()),
 601         _size_of_parameters(method->size_of_parameters()), _binding(NULL) {}
 602 
 603   Symbol* name() const { return _name; }
 604   Symbol* signature() const { return _signature; }
 605   int size_of_parameters() const { return _size_of_parameters; }
 606 
 607   void bind_family(MethodFamily* lm) { _binding = lm; }
 608   bool is_bound() { return _binding != NULL; }
 609   MethodFamily* get_binding() { return _binding; }
 610 
 611 #ifndef PRODUCT
 612   void print_on(outputStream* str) const {
 613     print_slot(str, name(), signature());
 614   }
 615 #endif // ndef PRODUCT
 616 };
 617 
 618 static bool already_in_vtable_slots(GrowableArray<EmptyVtableSlot*>* slots, Method* m) {
 619   bool found = false;
 620   for (int j = 0; j < slots->length(); ++j) {
 621     if (slots->at(j)->name() == m->name() &&
 622         slots->at(j)->signature() == m->signature() ) {
 623       found = true;
 624       break;
 625     }
 626   }
 627   return found;
 628 }
 629 
 630 static GrowableArray<EmptyVtableSlot*>* find_empty_vtable_slots(
 631     InstanceKlass* klass, GrowableArray<Method*>* mirandas, TRAPS) {
 632 
 633   assert(klass != NULL, "Must be valid class");
 634 
 635   GrowableArray<EmptyVtableSlot*>* slots = new GrowableArray<EmptyVtableSlot*>();
 636 
 637   // All miranda methods are obvious candidates
 638   for (int i = 0; i < mirandas->length(); ++i) {
 639     Method* m = mirandas->at(i);
 640     if (!already_in_vtable_slots(slots, m)) {
 641       slots->append(new EmptyVtableSlot(m));
 642     }
 643   }
 644 
 645   // Also any overpasses in our superclasses, that we haven't implemented.
 646   // (can't use the vtable because it is not guaranteed to be initialized yet)
 647   InstanceKlass* super = klass->java_super();
 648   while (super != NULL) {
 649     for (int i = 0; i < super->methods()->length(); ++i) {
 650       Method* m = super->methods()->at(i);
 651       if (m->is_overpass() || m->is_static()) {
 652         // m is a method that would have been a miranda if not for the
 653         // default method processing that occurred on behalf of our superclass,
 654         // so it's a method we want to re-examine in this new context.  That is,
 655         // unless we have a real implementation of it in the current class.
 656         Method* impl = klass->lookup_method(m->name(), m->signature());
 657         if (impl == NULL || impl->is_overpass() || impl->is_static()) {
 658           if (!already_in_vtable_slots(slots, m)) {
 659             slots->append(new EmptyVtableSlot(m));
 660           }
 661         }
 662       }
 663     }
 664 
 665     // also any default methods in our superclasses
 666     if (super->default_methods() != NULL) {
 667       for (int i = 0; i < super->default_methods()->length(); ++i) {
 668         Method* m = super->default_methods()->at(i);
 669         // m is a method that would have been a miranda if not for the
 670         // default method processing that occurred on behalf of our superclass,
 671         // so it's a method we want to re-examine in this new context.  That is,
 672         // unless we have a real implementation of it in the current class.
 673         Method* impl = klass->lookup_method(m->name(), m->signature());
 674         if (impl == NULL || impl->is_overpass() || impl->is_static()) {
 675           if (!already_in_vtable_slots(slots, m)) {
 676             slots->append(new EmptyVtableSlot(m));
 677           }
 678         }
 679       }
 680     }
 681     super = super->java_super();
 682   }
 683 
 684 #ifndef PRODUCT
 685   if (TraceDefaultMethods) {
 686     tty->print_cr("Slots that need filling:");
 687     streamIndentor si(tty);
 688     for (int i = 0; i < slots->length(); ++i) {
 689       tty->indent();
 690       slots->at(i)->print_on(tty);
 691       tty->cr();
 692     }
 693   }
 694 #endif // ndef PRODUCT
 695   return slots;
 696 }
 697 
 698 // Iterates over the superinterface type hierarchy looking for all methods
 699 // with a specific erased signature.
 700 class FindMethodsByErasedSig : public HierarchyVisitor<FindMethodsByErasedSig> {
 701  private:
 702   // Context data
 703   Symbol* _method_name;
 704   Symbol* _method_signature;
 705   StatefulMethodFamily*  _family;
 706 
 707  public:
 708   FindMethodsByErasedSig(Symbol* name, Symbol* signature) :
 709       _method_name(name), _method_signature(signature),
 710       _family(NULL) {}
 711 
 712   void get_discovered_family(MethodFamily** family) {
 713       if (_family != NULL) {
 714         *family = _family->get_method_family();
 715       } else {
 716         *family = NULL;
 717       }
 718   }
 719 
 720   void* new_node_data(InstanceKlass* cls) { return new PseudoScope(); }
 721   void free_node_data(void* node_data) {
 722     PseudoScope::cast(node_data)->destroy();
 723   }
 724 
 725   // Find all methods on this hierarchy that match this
 726   // method's erased (name, signature)
 727   bool visit() {
 728     PseudoScope* scope = PseudoScope::cast(current_data());
 729     InstanceKlass* iklass = current_class();
 730 
 731     Method* m = iklass->find_method(_method_name, _method_signature);
 732     // private interface methods are not candidates for default methods
 733     // invokespecial to private interface methods doesn't use default method logic
 734     // private class methods are not candidates for default methods,
 735     // private methods do not override default methods, so need to perform
 736     // default method inheritance without including private methods
 737     // The overpasses are your supertypes' errors, we do not include them
 738     // future: take access controls into account for superclass methods
 739     if (m != NULL && !m->is_static() && !m->is_overpass() && !m->is_private()) {
 740       if (_family == NULL) {
 741         _family = new StatefulMethodFamily();
 742       }
 743 
 744       if (iklass->is_interface()) {
 745         StateRestorer* restorer = _family->record_method_and_dq_further(m);
 746         scope->add_mark(restorer);
 747       } else {
 748         // This is the rule that methods in classes "win" (bad word) over
 749         // methods in interfaces. This works because of single inheritance
 750         // private methods in classes do not "win", they will be found
 751         // first on searching, but overriding for invokevirtual needs
 752         // to find default method candidates for the same signature
 753         _family->set_target_if_empty(m);
 754       }
 755     }
 756     return true;
 757   }
 758 
 759 };
 760 
 761 
 762 
 763 static void create_defaults_and_exceptions(
 764     GrowableArray<EmptyVtableSlot*>* slots, InstanceKlass* klass, TRAPS);
 765 
 766 static void generate_erased_defaults(
 767      InstanceKlass* klass, GrowableArray<EmptyVtableSlot*>* empty_slots,
 768      EmptyVtableSlot* slot, TRAPS) {
 769 
 770   // sets up a set of methods with the same exact erased signature
 771   FindMethodsByErasedSig visitor(slot->name(), slot->signature());
 772   visitor.run(klass);
 773 
 774   MethodFamily* family;
 775   visitor.get_discovered_family(&family);
 776   if (family != NULL) {
 777     family->determine_target(klass, CHECK);
 778     slot->bind_family(family);
 779   }
 780 }
 781 
 782 static void merge_in_new_methods(InstanceKlass* klass,
 783     GrowableArray<Method*>* new_methods, TRAPS);
 784 static void create_default_methods( InstanceKlass* klass,
 785     GrowableArray<Method*>* new_methods, TRAPS);
 786 
 787 // This is the guts of the default methods implementation.  This is called just
 788 // after the classfile has been parsed if some ancestor has default methods.
 789 //
 790 // First if finds any name/signature slots that need any implementation (either
 791 // because they are miranda or a superclass's implementation is an overpass
 792 // itself).  For each slot, iterate over the hierarchy, to see if they contain a
 793 // signature that matches the slot we are looking at.
 794 //
 795 // For each slot filled, we generate an overpass method that either calls the
 796 // unique default method candidate using invokespecial, or throws an exception
 797 // (in the case of no default method candidates, or more than one valid
 798 // candidate).  These methods are then added to the class's method list.
 799 // The JVM does not create bridges nor handle generic signatures here.
 800 void DefaultMethods::generate_default_methods(
 801     InstanceKlass* klass, GrowableArray<Method*>* mirandas, TRAPS) {
 802 
 803   // This resource mark is the bound for all memory allocation that takes
 804   // place during default method processing.  After this goes out of scope,
 805   // all (Resource) objects' memory will be reclaimed.  Be careful if adding an
 806   // embedded resource mark under here as that memory can't be used outside
 807   // whatever scope it's in.
 808   ResourceMark rm(THREAD);
 809 
 810   // Keep entire hierarchy alive for the duration of the computation
 811   KeepAliveRegistrar keepAlive(THREAD);
 812   KeepAliveVisitor loadKeepAlive(&keepAlive);
 813   loadKeepAlive.run(klass);
 814 
 815 #ifndef PRODUCT
 816   if (TraceDefaultMethods) {
 817     ResourceMark rm;  // be careful with these!
 818     tty->print_cr("%s %s requires default method processing",
 819         klass->is_interface() ? "Interface" : "Class",
 820         klass->name()->as_klass_external_name());
 821     PrintHierarchy printer;
 822     printer.run(klass);
 823   }
 824 #endif // ndef PRODUCT
 825 
 826   GrowableArray<EmptyVtableSlot*>* empty_slots =
 827       find_empty_vtable_slots(klass, mirandas, CHECK);
 828 
 829   for (int i = 0; i < empty_slots->length(); ++i) {
 830     EmptyVtableSlot* slot = empty_slots->at(i);
 831 #ifndef PRODUCT
 832     if (TraceDefaultMethods) {
 833       streamIndentor si(tty, 2);
 834       tty->indent().print("Looking for default methods for slot ");
 835       slot->print_on(tty);
 836       tty->cr();
 837     }
 838 #endif // ndef PRODUCT
 839 
 840     generate_erased_defaults(klass, empty_slots, slot, CHECK);
 841  }
 842 #ifndef PRODUCT
 843   if (TraceDefaultMethods) {
 844     tty->print_cr("Creating defaults and overpasses...");
 845   }
 846 #endif // ndef PRODUCT
 847 
 848   create_defaults_and_exceptions(empty_slots, klass, CHECK);
 849 
 850 #ifndef PRODUCT
 851   if (TraceDefaultMethods) {
 852     tty->print_cr("Default method processing complete");
 853   }
 854 #endif // ndef PRODUCT
 855 }
 856 
 857 static int assemble_method_error(
 858     BytecodeConstantPool* cp, BytecodeBuffer* buffer, Symbol* errorName, Symbol* message, TRAPS) {
 859 
 860   Symbol* init = vmSymbols::object_initializer_name();
 861   Symbol* sig = vmSymbols::string_void_signature();
 862 
 863   BytecodeAssembler assem(buffer, cp);
 864 
 865   assem._new(errorName);
 866   assem.dup();
 867   assem.load_string(message);
 868   assem.invokespecial(errorName, init, sig);
 869   assem.athrow();
 870 
 871   return 3; // max stack size: [ exception, exception, string ]
 872 }
 873 
 874 static Method* new_method(
 875     BytecodeConstantPool* cp, BytecodeBuffer* bytecodes, Symbol* name,
 876     Symbol* sig, AccessFlags flags, int max_stack, int params,
 877     ConstMethod::MethodType mt, TRAPS) {
 878 
 879   address code_start = 0;
 880   int code_length = 0;
 881   InlineTableSizes sizes;
 882 
 883   if (bytecodes != NULL && bytecodes->length() > 0) {
 884     code_start = static_cast<address>(bytecodes->adr_at(0));
 885     code_length = bytecodes->length();
 886   }
 887 
 888   Method* m = Method::allocate(cp->pool_holder()->class_loader_data(),
 889                                code_length, flags, &sizes,
 890                                mt, CHECK_NULL);
 891 
 892   m->set_constants(NULL); // This will get filled in later
 893   m->set_name_index(cp->utf8(name));
 894   m->set_signature_index(cp->utf8(sig));
 895   ResultTypeFinder rtf(sig);
 896   m->constMethod()->set_result_type(rtf.type());
 897   m->set_size_of_parameters(params);
 898   m->set_max_stack(max_stack);
 899   m->set_max_locals(params);
 900   m->constMethod()->set_stackmap_data(NULL);
 901   m->set_code(code_start);
 902 
 903   return m;
 904 }
 905 
 906 static void switchover_constant_pool(BytecodeConstantPool* bpool,
 907     InstanceKlass* klass, GrowableArray<Method*>* new_methods, TRAPS) {
 908 
 909   if (new_methods->length() > 0) {
 910     ConstantPool* cp = bpool->create_constant_pool(CHECK);
 911     if (cp != klass->constants()) {
 912       klass->class_loader_data()->add_to_deallocate_list(klass->constants());
 913       klass->set_constants(cp);
 914       cp->set_pool_holder(klass);
 915 
 916       for (int i = 0; i < new_methods->length(); ++i) {
 917         new_methods->at(i)->set_constants(cp);
 918       }
 919       for (int i = 0; i < klass->methods()->length(); ++i) {
 920         Method* mo = klass->methods()->at(i);
 921         mo->set_constants(cp);
 922       }
 923     }
 924   }
 925 }
 926 
 927 // Create default_methods list for the current class.
 928 // With the VM only processing erased signatures, the VM only
 929 // creates an overpass in a conflict case or a case with no candidates.
 930 // This allows virtual methods to override the overpass, but ensures
 931 // that a local method search will find the exception rather than an abstract
 932 // or default method that is not a valid candidate.
 933 static void create_defaults_and_exceptions(
 934     GrowableArray<EmptyVtableSlot*>* slots,
 935     InstanceKlass* klass, TRAPS) {
 936 
 937   GrowableArray<Method*> overpasses;
 938   GrowableArray<Method*> defaults;
 939   BytecodeConstantPool bpool(klass->constants());
 940 
 941   for (int i = 0; i < slots->length(); ++i) {
 942     EmptyVtableSlot* slot = slots->at(i);
 943 
 944     if (slot->is_bound()) {
 945       MethodFamily* method = slot->get_binding();
 946       BytecodeBuffer buffer;
 947 
 948 #ifndef PRODUCT
 949       if (TraceDefaultMethods) {
 950         tty->print("for slot: ");
 951         slot->print_on(tty);
 952         tty->cr();
 953         if (method->has_target()) {
 954           method->print_selected(tty, 1);
 955         } else if (method->throws_exception()) {
 956           method->print_exception(tty, 1);
 957         }
 958       }
 959 #endif // ndef PRODUCT
 960 
 961       if (method->has_target()) {
 962         Method* selected = method->get_selected_target();
 963         if (selected->method_holder()->is_interface()) {
 964           defaults.push(selected);
 965         }
 966       } else if (method->throws_exception()) {
 967         int max_stack = assemble_method_error(&bpool, &buffer,
 968            method->get_exception_name(), method->get_exception_message(), CHECK);
 969         AccessFlags flags = accessFlags_from(
 970           JVM_ACC_PUBLIC | JVM_ACC_SYNTHETIC | JVM_ACC_BRIDGE);
 971          Method* m = new_method(&bpool, &buffer, slot->name(), slot->signature(),
 972           flags, max_stack, slot->size_of_parameters(),
 973           ConstMethod::OVERPASS, CHECK);
 974         // We push to the methods list:
 975         // overpass methods which are exception throwing methods
 976         if (m != NULL) {
 977           overpasses.push(m);
 978         }
 979       }
 980     }
 981   }
 982 
 983 #ifndef PRODUCT
 984   if (TraceDefaultMethods) {
 985     tty->print_cr("Created %d overpass methods", overpasses.length());
 986     tty->print_cr("Created %d default  methods", defaults.length());
 987   }
 988 #endif // ndef PRODUCT
 989 
 990   if (overpasses.length() > 0) {
 991     switchover_constant_pool(&bpool, klass, &overpasses, CHECK);
 992     merge_in_new_methods(klass, &overpasses, CHECK);
 993   }
 994   if (defaults.length() > 0) {
 995     create_default_methods(klass, &defaults, CHECK);
 996   }
 997 }
 998 
 999 static void create_default_methods( InstanceKlass* klass,
1000     GrowableArray<Method*>* new_methods, TRAPS) {
1001 
1002   int new_size = new_methods->length();
1003   Array<Method*>* total_default_methods = MetadataFactory::new_array<Method*>(
1004       klass->class_loader_data(), new_size, NULL, CHECK);
1005   for (int index = 0; index < new_size; index++ ) {
1006     total_default_methods->at_put(index, new_methods->at(index));
1007   }
1008   Method::sort_methods(total_default_methods, false, false);
1009 
1010   klass->set_default_methods(total_default_methods);
1011 }
1012 
1013 static void sort_methods(GrowableArray<Method*>* methods) {
1014   // Note that this must sort using the same key as is used for sorting
1015   // methods in InstanceKlass.
1016   bool sorted = true;
1017   for (int i = methods->length() - 1; i > 0; --i) {
1018     for (int j = 0; j < i; ++j) {
1019       Method* m1 = methods->at(j);
1020       Method* m2 = methods->at(j + 1);
1021       if ((uintptr_t)m1->name() > (uintptr_t)m2->name()) {
1022         methods->at_put(j, m2);
1023         methods->at_put(j + 1, m1);
1024         sorted = false;
1025       }
1026     }
1027     if (sorted) break;
1028     sorted = true;
1029   }
1030 #ifdef ASSERT
1031   uintptr_t prev = 0;
1032   for (int i = 0; i < methods->length(); ++i) {
1033     Method* mh = methods->at(i);
1034     uintptr_t nv = (uintptr_t)mh->name();
1035     assert(nv >= prev, "Incorrect overpass method ordering");
1036     prev = nv;
1037   }
1038 #endif
1039 }
1040 
1041 static void merge_in_new_methods(InstanceKlass* klass,
1042     GrowableArray<Method*>* new_methods, TRAPS) {
1043 
1044   enum { ANNOTATIONS, PARAMETERS, DEFAULTS, NUM_ARRAYS };
1045 
1046   Array<Method*>* original_methods = klass->methods();
1047   Array<int>* original_ordering = klass->method_ordering();
1048   Array<int>* merged_ordering = Universe::the_empty_int_array();
1049 
1050   int new_size = klass->methods()->length() + new_methods->length();
1051 
1052   Array<Method*>* merged_methods = MetadataFactory::new_array<Method*>(
1053       klass->class_loader_data(), new_size, NULL, CHECK);
1054 
1055   // original_ordering might be empty if this class has no methods of its own
1056   if (JvmtiExport::can_maintain_original_method_order() || DumpSharedSpaces) {
1057     merged_ordering = MetadataFactory::new_array<int>(
1058         klass->class_loader_data(), new_size, CHECK);
1059   }
1060   int method_order_index = klass->methods()->length();
1061 
1062   sort_methods(new_methods);
1063 
1064   // Perform grand merge of existing methods and new methods
1065   int orig_idx = 0;
1066   int new_idx = 0;
1067 
1068   for (int i = 0; i < new_size; ++i) {
1069     Method* orig_method = NULL;
1070     Method* new_method = NULL;
1071     if (orig_idx < original_methods->length()) {
1072       orig_method = original_methods->at(orig_idx);
1073     }
1074     if (new_idx < new_methods->length()) {
1075       new_method = new_methods->at(new_idx);
1076     }
1077 
1078     if (orig_method != NULL &&
1079         (new_method == NULL || orig_method->name() < new_method->name())) {
1080       merged_methods->at_put(i, orig_method);
1081       original_methods->at_put(orig_idx, NULL);
1082       if (merged_ordering->length() > 0) {
1083         assert(original_ordering != NULL && original_ordering->length() > 0,
1084                "should have original order information for this method");
1085         merged_ordering->at_put(i, original_ordering->at(orig_idx));
1086       }
1087       ++orig_idx;
1088     } else {
1089       merged_methods->at_put(i, new_method);
1090       if (merged_ordering->length() > 0) {
1091         merged_ordering->at_put(i, method_order_index++);
1092       }
1093       ++new_idx;
1094     }
1095     // update idnum for new location
1096     merged_methods->at(i)->set_method_idnum(i);
1097     merged_methods->at(i)->set_orig_method_idnum(i);
1098   }
1099 
1100   // Verify correct order
1101 #ifdef ASSERT
1102   uintptr_t prev = 0;
1103   for (int i = 0; i < merged_methods->length(); ++i) {
1104     Method* mo = merged_methods->at(i);
1105     uintptr_t nv = (uintptr_t)mo->name();
1106     assert(nv >= prev, "Incorrect method ordering");
1107     prev = nv;
1108   }
1109 #endif
1110 
1111   // Replace klass methods with new merged lists
1112   klass->set_methods(merged_methods);
1113   klass->set_initial_method_idnum(new_size);
1114   klass->set_method_ordering(merged_ordering);
1115 
1116   // Free metadata
1117   ClassLoaderData* cld = klass->class_loader_data();
1118   if (original_methods->length() > 0) {
1119     MetadataFactory::free_array(cld, original_methods);
1120   }
1121   if (original_ordering != NULL && original_ordering->length() > 0) {
1122     MetadataFactory::free_array(cld, original_ordering);
1123   }
1124 }