1 /*
   2  * Copyright (c) 1997, 2015, 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/systemDictionary.hpp"
  27 #include "classfile/vmSymbols.hpp"
  28 #include "memory/gcLocker.hpp"
  29 #include "memory/resourceArea.hpp"
  30 #include "memory/universe.inline.hpp"
  31 #include "oops/instanceKlass.hpp"
  32 #include "oops/klassVtable.hpp"
  33 #include "oops/method.hpp"
  34 #include "oops/objArrayOop.hpp"
  35 #include "oops/oop.inline.hpp"
  36 #include "prims/jvmtiRedefineClassesTrace.hpp"
  37 #include "runtime/arguments.hpp"
  38 #include "runtime/handles.inline.hpp"
  39 #include "utilities/copy.hpp"
  40 
  41 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
  42 
  43 inline InstanceKlass* klassVtable::ik() const {
  44   Klass* k = _klass();
  45   assert(k->oop_is_instance(), "not an InstanceKlass");
  46   return (InstanceKlass*)k;
  47 }
  48 
  49 
  50 // this function computes the vtable size (including the size needed for miranda
  51 // methods) and the number of miranda methods in this class.
  52 // Note on Miranda methods: Let's say there is a class C that implements
  53 // interface I, and none of C's superclasses implements I.
  54 // Let's say there is an abstract method m in I that neither C
  55 // nor any of its super classes implement (i.e there is no method of any access,
  56 // with the same name and signature as m), then m is a Miranda method which is
  57 // entered as a public abstract method in C's vtable.  From then on it should
  58 // treated as any other public method in C for method over-ride purposes.
  59 void klassVtable::compute_vtable_size_and_num_mirandas(
  60     int* vtable_length_ret, int* num_new_mirandas,
  61     GrowableArray<Method*>* all_mirandas, Klass* super,
  62     Array<Method*>* methods, AccessFlags class_flags,
  63     Handle classloader, Symbol* classname, Array<Klass*>* local_interfaces,
  64     TRAPS) {
  65   No_Safepoint_Verifier nsv;
  66 
  67   // set up default result values
  68   int vtable_length = 0;
  69 
  70   // start off with super's vtable length
  71   InstanceKlass* sk = (InstanceKlass*)super;
  72   vtable_length = super == NULL ? 0 : sk->vtable_length();
  73 
  74   // go thru each method in the methods table to see if it needs a new entry
  75   int len = methods->length();
  76   for (int i = 0; i < len; i++) {
  77     assert(methods->at(i)->is_method(), "must be a Method*");
  78     methodHandle mh(THREAD, methods->at(i));
  79 
  80     if (needs_new_vtable_entry(mh, super, classloader, classname, class_flags, THREAD)) {
  81       vtable_length += vtableEntry::size(); // we need a new entry
  82     }
  83   }
  84 
  85   GrowableArray<Method*> new_mirandas(20);
  86   // compute the number of mirandas methods that must be added to the end
  87   get_mirandas(&new_mirandas, all_mirandas, super, methods, NULL, local_interfaces);
  88   *num_new_mirandas = new_mirandas.length();
  89 
  90   // Interfaces do not need interface methods in their vtables
  91   // This includes miranda methods and during later processing, default methods
  92   if (!class_flags.is_interface()) {
  93     vtable_length += *num_new_mirandas * vtableEntry::size();
  94   }
  95 
  96   if (Universe::is_bootstrapping() && vtable_length == 0) {
  97     // array classes don't have their superclass set correctly during
  98     // bootstrapping
  99     vtable_length = Universe::base_vtable_size();
 100   }
 101 
 102   if (super == NULL && vtable_length != Universe::base_vtable_size()) {
 103     if (Universe::is_bootstrapping()) {
 104       // Someone is attempting to override java.lang.Object incorrectly on the
 105       // bootclasspath.  The JVM cannot recover from this error including throwing
 106       // an exception
 107       vm_exit_during_initialization("Incompatible definition of java.lang.Object");
 108     } else {
 109       // Someone is attempting to redefine java.lang.Object incorrectly.  The
 110       // only way this should happen is from
 111       // SystemDictionary::resolve_from_stream(), which will detect this later
 112       // and throw a security exception.  So don't assert here to let
 113       // the exception occur.
 114       vtable_length = Universe::base_vtable_size();
 115     }
 116   }
 117   assert(vtable_length % vtableEntry::size() == 0, "bad vtable length");
 118   assert(vtable_length >= Universe::base_vtable_size(), "vtable too small");
 119 
 120   *vtable_length_ret = vtable_length;
 121 }
 122 
 123 int klassVtable::index_of(Method* m, int len) const {
 124   assert(m->has_vtable_index(), "do not ask this of non-vtable methods");
 125   return m->vtable_index();
 126 }
 127 
 128 // Copy super class's vtable to the first part (prefix) of this class's vtable,
 129 // and return the number of entries copied.  Expects that 'super' is the Java
 130 // super class (arrays can have "array" super classes that must be skipped).
 131 int klassVtable::initialize_from_super(KlassHandle super) {
 132   if (super.is_null()) {
 133     return 0;
 134   } else {
 135     // copy methods from superKlass
 136     // can't inherit from array class, so must be InstanceKlass
 137     assert(super->oop_is_instance(), "must be instance klass");
 138     InstanceKlass* sk = (InstanceKlass*)super();
 139     klassVtable* superVtable = sk->vtable();
 140     assert(superVtable->length() <= _length, "vtable too short");
 141 #ifdef ASSERT
 142     superVtable->verify(tty, true);
 143 #endif
 144     superVtable->copy_vtable_to(table());
 145 #ifndef PRODUCT
 146     if (PrintVtables && Verbose) {
 147       ResourceMark rm;
 148       tty->print_cr("copy vtable from %s to %s size %d", sk->internal_name(), klass()->internal_name(), _length);
 149     }
 150 #endif
 151     return superVtable->length();
 152   }
 153 }
 154 
 155 //
 156 // Revised lookup semantics   introduced 1.3 (Kestrel beta)
 157 void klassVtable::initialize_vtable(bool checkconstraints, TRAPS) {
 158 
 159   // Note:  Arrays can have intermediate array supers.  Use java_super to skip them.
 160   KlassHandle super (THREAD, klass()->java_super());
 161   int nofNewEntries = 0;
 162 
 163   if (PrintVtables && !klass()->oop_is_array()) {
 164     ResourceMark rm(THREAD);
 165     tty->print_cr("Initializing: %s", _klass->name()->as_C_string());
 166   }
 167 
 168 #ifdef ASSERT
 169   oop* end_of_obj = (oop*)_klass() + _klass()->size();
 170   oop* end_of_vtable = (oop*)&table()[_length];
 171   assert(end_of_vtable <= end_of_obj, "vtable extends beyond end");
 172 #endif
 173 
 174   if (Universe::is_bootstrapping()) {
 175     // just clear everything
 176     for (int i = 0; i < _length; i++) table()[i].clear();
 177     return;
 178   }
 179 
 180   int super_vtable_len = initialize_from_super(super);
 181   if (klass()->oop_is_array()) {
 182     assert(super_vtable_len == _length, "arrays shouldn't introduce new methods");
 183   } else {
 184     assert(_klass->oop_is_instance(), "must be InstanceKlass");
 185 
 186     Array<Method*>* methods = ik()->methods();
 187     int len = methods->length();
 188     int initialized = super_vtable_len;
 189 
 190     // Check each of this class's methods against super;
 191     // if override, replace in copy of super vtable, otherwise append to end
 192     for (int i = 0; i < len; i++) {
 193       // update_inherited_vtable can stop for gc - ensure using handles
 194       HandleMark hm(THREAD);
 195       assert(methods->at(i)->is_method(), "must be a Method*");
 196       methodHandle mh(THREAD, methods->at(i));
 197 
 198       bool needs_new_entry = update_inherited_vtable(ik(), mh, super_vtable_len, -1, checkconstraints, CHECK);
 199 
 200       if (needs_new_entry) {
 201         put_method_at(mh(), initialized);
 202         mh()->set_vtable_index(initialized); // set primary vtable index
 203         initialized++;
 204       }
 205     }
 206 
 207     // update vtable with default_methods
 208     Array<Method*>* default_methods = ik()->default_methods();
 209     if (default_methods != NULL) {
 210       len = default_methods->length();
 211       if (len > 0) {
 212         Array<int>* def_vtable_indices = NULL;
 213         if ((def_vtable_indices = ik()->default_vtable_indices()) == NULL) {
 214           def_vtable_indices = ik()->create_new_default_vtable_indices(len, CHECK);
 215         } else {
 216           assert(def_vtable_indices->length() == len, "reinit vtable len?");
 217         }
 218         for (int i = 0; i < len; i++) {
 219           HandleMark hm(THREAD);
 220           assert(default_methods->at(i)->is_method(), "must be a Method*");
 221           methodHandle mh(THREAD, default_methods->at(i));
 222 
 223           bool needs_new_entry = update_inherited_vtable(ik(), mh, super_vtable_len, i, checkconstraints, CHECK);
 224 
 225           // needs new entry
 226           if (needs_new_entry) {
 227             put_method_at(mh(), initialized);
 228             def_vtable_indices->at_put(i, initialized); //set vtable index
 229             initialized++;
 230           }
 231         }
 232       }
 233     }
 234 
 235     // add miranda methods; it will also return the updated initialized
 236     // Interfaces do not need interface methods in their vtables
 237     // This includes miranda methods and during later processing, default methods
 238     if (!ik()->is_interface()) {
 239       initialized = fill_in_mirandas(initialized);
 240     }
 241 
 242     // In class hierarchies where the accessibility is not increasing (i.e., going from private ->
 243     // package_private -> public/protected), the vtable might actually be smaller than our initial
 244     // calculation.
 245     assert(initialized <= _length, "vtable initialization failed");
 246     for(;initialized < _length; initialized++) {
 247       put_method_at(NULL, initialized);
 248     }
 249     NOT_PRODUCT(verify(tty, true));
 250   }
 251 }
 252 
 253 // Called for cases where a method does not override its superclass' vtable entry
 254 // For bytecodes not produced by javac together it is possible that a method does not override
 255 // the superclass's method, but might indirectly override a super-super class's vtable entry
 256 // If none found, return a null superk, else return the superk of the method this does override
 257 // For public and protected methods: if they override a superclass, they will
 258 // also be overridden themselves appropriately.
 259 // Private methods do not override and are not overridden.
 260 // Package Private methods are trickier:
 261 // e.g. P1.A, pub m
 262 // P2.B extends A, package private m
 263 // P1.C extends B, public m
 264 // P1.C.m needs to override P1.A.m and can not override P2.B.m
 265 // Therefore: all package private methods need their own vtable entries for
 266 // them to be the root of an inheritance overriding decision
 267 // Package private methods may also override other vtable entries
 268 InstanceKlass* klassVtable::find_transitive_override(InstanceKlass* initialsuper, methodHandle target_method,
 269                             int vtable_index, Handle target_loader, Symbol* target_classname, Thread * THREAD) {
 270   InstanceKlass* superk = initialsuper;
 271   while (superk != NULL && superk->super() != NULL) {
 272     InstanceKlass* supersuperklass = InstanceKlass::cast(superk->super());
 273     klassVtable* ssVtable = supersuperklass->vtable();
 274     if (vtable_index < ssVtable->length()) {
 275       Method* super_method = ssVtable->method_at(vtable_index);
 276 #ifndef PRODUCT
 277       Symbol* name= target_method()->name();
 278       Symbol* signature = target_method()->signature();
 279       assert(super_method->name()->equals(name) && super_method->signature()->equals(signature), "vtable entry name/sig mismatch");
 280 #endif
 281       if (supersuperklass->is_override(super_method, target_loader, target_classname, THREAD)) {
 282 #ifndef PRODUCT
 283         if (PrintVtables && Verbose) {
 284           ResourceMark rm(THREAD);
 285           char* sig = target_method()->name_and_sig_as_C_string();
 286           tty->print("transitive overriding superclass %s with %s::%s index %d, original flags: ",
 287            supersuperklass->internal_name(),
 288            _klass->internal_name(), sig, vtable_index);
 289            super_method->access_flags().print_on(tty);
 290            if (super_method->is_default_method()) {
 291              tty->print("default ");
 292            }
 293            tty->print("overriders flags: ");
 294            target_method->access_flags().print_on(tty);
 295            if (target_method->is_default_method()) {
 296              tty->print("default ");
 297            }
 298         }
 299 #endif /*PRODUCT*/
 300         break; // return found superk
 301       }
 302     } else  {
 303       // super class has no vtable entry here, stop transitive search
 304       superk = (InstanceKlass*)NULL;
 305       break;
 306     }
 307     // if no override found yet, continue to search up
 308     superk = InstanceKlass::cast(superk->super());
 309   }
 310 
 311   return superk;
 312 }
 313 
 314 // Update child's copy of super vtable for overrides
 315 // OR return true if a new vtable entry is required.
 316 // Only called for InstanceKlass's, i.e. not for arrays
 317 // If that changed, could not use _klass as handle for klass
 318 bool klassVtable::update_inherited_vtable(InstanceKlass* klass, methodHandle target_method,
 319                                           int super_vtable_len, int default_index,
 320                                           bool checkconstraints, TRAPS) {
 321   ResourceMark rm;
 322   bool allocate_new = true;
 323   assert(klass->oop_is_instance(), "must be InstanceKlass");
 324 
 325   Array<int>* def_vtable_indices = NULL;
 326   bool is_default = false;
 327   // default methods are concrete methods in superinterfaces which are added to the vtable
 328   // with their real method_holder
 329   // Since vtable and itable indices share the same storage, don't touch
 330   // the default method's real vtable/itable index
 331   // default_vtable_indices stores the vtable value relative to this inheritor
 332   if (default_index >= 0 ) {
 333     is_default = true;
 334     def_vtable_indices = klass->default_vtable_indices();
 335     assert(def_vtable_indices != NULL, "def vtable alloc?");
 336     assert(default_index <= def_vtable_indices->length(), "def vtable len?");
 337   } else {
 338     assert(klass == target_method()->method_holder(), "caller resp.");
 339     // Initialize the method's vtable index to "nonvirtual".
 340     // If we allocate a vtable entry, we will update it to a non-negative number.
 341     target_method()->set_vtable_index(Method::nonvirtual_vtable_index);
 342   }
 343 
 344   // Static and <init> methods are never in
 345   if (target_method()->is_static() || target_method()->name()->equals(vmSymbols::object_initializer_name())) {
 346     return false;
 347   }
 348 
 349   if (target_method->is_final_method(klass->access_flags())) {
 350     // a final method never needs a new entry; final methods can be statically
 351     // resolved and they have to be present in the vtable only if they override
 352     // a super's method, in which case they re-use its entry
 353     allocate_new = false;
 354   } else if (klass->is_interface()) {
 355     allocate_new = false;  // see note below in needs_new_vtable_entry
 356     // An interface never allocates new vtable slots, only inherits old ones.
 357     // This method will either be assigned its own itable index later,
 358     // or be assigned an inherited vtable index in the loop below.
 359     // default methods inherited by classes store their vtable indices
 360     // in the inheritor's default_vtable_indices
 361     // default methods inherited by interfaces may already have a
 362     // valid itable index, if so, don't change it
 363     // overpass methods in an interface will be assigned an itable index later
 364     // by an inheriting class
 365     if (!is_default || !target_method()->has_itable_index()) {
 366       target_method()->set_vtable_index(Method::pending_itable_index);
 367     }
 368   }
 369 
 370   // we need a new entry if there is no superclass
 371   if (klass->super() == NULL) {
 372     return allocate_new;
 373   }
 374 
 375   // private methods in classes always have a new entry in the vtable
 376   // specification interpretation since classic has
 377   // private methods not overriding
 378   // JDK8 adds private methods in interfaces which require invokespecial
 379   if (target_method()->is_private()) {
 380     return allocate_new;
 381   }
 382 
 383   // search through the vtable and update overridden entries
 384   // Since check_signature_loaders acquires SystemDictionary_lock
 385   // which can block for gc, once we are in this loop, use handles
 386   // For classfiles built with >= jdk7, we now look for transitive overrides
 387 
 388   Symbol* name = target_method()->name();
 389   Symbol* signature = target_method()->signature();
 390 
 391   KlassHandle target_klass(THREAD, target_method()->method_holder());
 392   if (target_klass == NULL) {
 393     target_klass = _klass;
 394   }
 395 
 396   Handle target_loader(THREAD, target_klass->class_loader());
 397 
 398   Symbol* target_classname = target_klass->name();
 399   for(int i = 0; i < super_vtable_len; i++) {
 400     Method* super_method = method_at(i);
 401     // Check if method name matches
 402     if (super_method->name()->equals(name) && super_method->signature()->equals(signature)) {
 403 
 404       // get super_klass for method_holder for the found method
 405       InstanceKlass* super_klass =  super_method->method_holder();
 406 
 407       if (is_default
 408           || ((super_klass->is_override(super_method, target_loader, target_classname, THREAD))
 409           || ((klass->major_version() >= VTABLE_TRANSITIVE_OVERRIDE_VERSION)
 410           && ((super_klass = find_transitive_override(super_klass,
 411                              target_method, i, target_loader,
 412                              target_classname, THREAD))
 413                              != (InstanceKlass*)NULL))))
 414         {
 415         // Package private methods always need a new entry to root their own
 416         // overriding. They may also override other methods.
 417         if (!target_method()->is_package_private()) {
 418           allocate_new = false;
 419         }
 420 
 421         if (checkconstraints) {
 422         // Override vtable entry if passes loader constraint check
 423         // if loader constraint checking requested
 424         // No need to visit his super, since he and his super
 425         // have already made any needed loader constraints.
 426         // Since loader constraints are transitive, it is enough
 427         // to link to the first super, and we get all the others.
 428           Handle super_loader(THREAD, super_klass->class_loader());
 429 
 430           if (target_loader() != super_loader()) {
 431             ResourceMark rm(THREAD);
 432             Symbol* failed_type_symbol =
 433               SystemDictionary::check_signature_loaders(signature, target_loader,
 434                                                         super_loader, true,
 435                                                         CHECK_(false));
 436             if (failed_type_symbol != NULL) {
 437               const char* msg = "loader constraint violation: when resolving "
 438                 "overridden method \"%s\" the class loader (instance"
 439                 " of %s) of the current class, %s, and its superclass loader "
 440                 "(instance of %s), have different Class objects for the type "
 441                 "%s used in the signature";
 442               char* sig = target_method()->name_and_sig_as_C_string();
 443               const char* loader1 = SystemDictionary::loader_name(target_loader());
 444               char* current = target_klass->name()->as_C_string();
 445               const char* loader2 = SystemDictionary::loader_name(super_loader());
 446               char* failed_type_name = failed_type_symbol->as_C_string();
 447               size_t buflen = strlen(msg) + strlen(sig) + strlen(loader1) +
 448                 strlen(current) + strlen(loader2) + strlen(failed_type_name);
 449               char* buf = NEW_RESOURCE_ARRAY_IN_THREAD(THREAD, char, buflen);
 450               jio_snprintf(buf, buflen, msg, sig, loader1, current, loader2,
 451                            failed_type_name);
 452               THROW_MSG_(vmSymbols::java_lang_LinkageError(), buf, false);
 453             }
 454           }
 455        }
 456 
 457        put_method_at(target_method(), i);
 458        if (!is_default) {
 459          target_method()->set_vtable_index(i);
 460        } else {
 461          if (def_vtable_indices != NULL) {
 462            def_vtable_indices->at_put(default_index, i);
 463          }
 464          assert(super_method->is_default_method() || super_method->is_overpass()
 465                 || super_method->is_abstract(), "default override error");
 466        }
 467 
 468 
 469 #ifndef PRODUCT
 470         if (PrintVtables && Verbose) {
 471           ResourceMark rm(THREAD);
 472           char* sig = target_method()->name_and_sig_as_C_string();
 473           tty->print("overriding with %s::%s index %d, original flags: ",
 474            target_klass->internal_name(), sig, i);
 475            super_method->access_flags().print_on(tty);
 476            if (super_method->is_default_method()) {
 477              tty->print("default ");
 478            }
 479            if (super_method->is_overpass()) {
 480              tty->print("overpass");
 481            }
 482            tty->print("overriders flags: ");
 483            target_method->access_flags().print_on(tty);
 484            if (target_method->is_default_method()) {
 485              tty->print("default ");
 486            }
 487            if (target_method->is_overpass()) {
 488              tty->print("overpass");
 489            }
 490            tty->cr();
 491         }
 492 #endif /*PRODUCT*/
 493       } else {
 494         // allocate_new = true; default. We might override one entry,
 495         // but not override another. Once we override one, not need new
 496 #ifndef PRODUCT
 497         if (PrintVtables && Verbose) {
 498           ResourceMark rm(THREAD);
 499           char* sig = target_method()->name_and_sig_as_C_string();
 500           tty->print("NOT overriding with %s::%s index %d, original flags: ",
 501            target_klass->internal_name(), sig,i);
 502            super_method->access_flags().print_on(tty);
 503            if (super_method->is_default_method()) {
 504              tty->print("default ");
 505            }
 506            if (super_method->is_overpass()) {
 507              tty->print("overpass");
 508            }
 509            tty->print("overriders flags: ");
 510            target_method->access_flags().print_on(tty);
 511            if (target_method->is_default_method()) {
 512              tty->print("default ");
 513            }
 514            if (target_method->is_overpass()) {
 515              tty->print("overpass");
 516            }
 517            tty->cr();
 518         }
 519 #endif /*PRODUCT*/
 520       }
 521     }
 522   }
 523   return allocate_new;
 524 }
 525 
 526 void klassVtable::put_method_at(Method* m, int index) {
 527 #ifndef PRODUCT
 528   if (PrintVtables && Verbose) {
 529     ResourceMark rm;
 530     const char* sig = (m != NULL) ? m->name_and_sig_as_C_string() : "<NULL>";
 531     tty->print("adding %s at index %d, flags: ", sig, index);
 532     if (m != NULL) {
 533       m->access_flags().print_on(tty);
 534       if (m->is_default_method()) {
 535         tty->print("default ");
 536       }
 537       if (m->is_overpass()) {
 538         tty->print("overpass");
 539       }
 540     }
 541     tty->cr();
 542   }
 543 #endif
 544   table()[index].set(m);
 545 }
 546 
 547 // Find out if a method "m" with superclass "super", loader "classloader" and
 548 // name "classname" needs a new vtable entry.  Let P be a class package defined
 549 // by "classloader" and "classname".
 550 // NOTE: The logic used here is very similar to the one used for computing
 551 // the vtables indices for a method. We cannot directly use that function because,
 552 // we allocate the InstanceKlass at load time, and that requires that the
 553 // superclass has been loaded.
 554 // However, the vtable entries are filled in at link time, and therefore
 555 // the superclass' vtable may not yet have been filled in.
 556 bool klassVtable::needs_new_vtable_entry(methodHandle target_method,
 557                                          Klass* super,
 558                                          Handle classloader,
 559                                          Symbol* classname,
 560                                          AccessFlags class_flags,
 561                                          TRAPS) {
 562   if (class_flags.is_interface()) {
 563     // Interfaces do not use vtables, except for java.lang.Object methods,
 564     // so there is no point to assigning
 565     // a vtable index to any of their local methods.  If we refrain from doing this,
 566     // we can use Method::_vtable_index to hold the itable index
 567     return false;
 568   }
 569 
 570   if (target_method->is_final_method(class_flags) ||
 571       // a final method never needs a new entry; final methods can be statically
 572       // resolved and they have to be present in the vtable only if they override
 573       // a super's method, in which case they re-use its entry
 574       (target_method()->is_static()) ||
 575       // static methods don't need to be in vtable
 576       (target_method()->name()->equals(vmSymbols::object_initializer_name()))
 577       // <init> is never called dynamically-bound
 578       ) {
 579     return false;
 580   }
 581 
 582   // Concrete interface methods do not need new entries, they override
 583   // abstract method entries using default inheritance rules
 584   if (target_method()->method_holder() != NULL &&
 585       target_method()->method_holder()->is_interface()  &&
 586       !target_method()->is_abstract() ) {
 587     return false;
 588   }
 589 
 590   // we need a new entry if there is no superclass
 591   if (super == NULL) {
 592     return true;
 593   }
 594 
 595   // private methods in classes always have a new entry in the vtable
 596   // specification interpretation since classic has
 597   // private methods not overriding
 598   // JDK8 adds private  methods in interfaces which require invokespecial
 599   if (target_method()->is_private()) {
 600     return true;
 601   }
 602 
 603   // Package private methods always need a new entry to root their own
 604   // overriding. This allows transitive overriding to work.
 605   if (target_method()->is_package_private()) {
 606     return true;
 607   }
 608 
 609   // search through the super class hierarchy to see if we need
 610   // a new entry
 611   ResourceMark rm;
 612   Symbol* name = target_method()->name();
 613   Symbol* signature = target_method()->signature();
 614   Klass* k = super;
 615   Method* super_method = NULL;
 616   InstanceKlass *holder = NULL;
 617   Method* recheck_method =  NULL;
 618   while (k != NULL) {
 619     // lookup through the hierarchy for a method with matching name and sign.
 620     super_method = InstanceKlass::cast(k)->lookup_method(name, signature);
 621     if (super_method == NULL) {
 622       break; // we still have to search for a matching miranda method
 623     }
 624     // get the class holding the matching method
 625     // make sure you use that class for is_override
 626     InstanceKlass* superk = super_method->method_holder();
 627     // we want only instance method matches
 628     // pretend private methods are not in the super vtable
 629     // since we do override around them: e.g. a.m pub/b.m private/c.m pub,
 630     // ignore private, c.m pub does override a.m pub
 631     // For classes that were not javac'd together, we also do transitive overriding around
 632     // methods that have less accessibility
 633     if ((!super_method->is_static()) &&
 634        (!super_method->is_private())) {
 635       if (superk->is_override(super_method, classloader, classname, THREAD)) {
 636         return false;
 637       // else keep looking for transitive overrides
 638       }
 639     }
 640 
 641     // Start with lookup result and continue to search up
 642     k = superk->super(); // haven't found an override match yet; continue to look
 643   }
 644 
 645   // if the target method is public or protected it may have a matching
 646   // miranda method in the super, whose entry it should re-use.
 647   // Actually, to handle cases that javac would not generate, we need
 648   // this check for all access permissions.
 649   InstanceKlass *sk = InstanceKlass::cast(super);
 650   if (sk->has_miranda_methods()) {
 651     if (sk->lookup_method_in_all_interfaces(name, signature, Klass::find_defaults) != NULL) {
 652       return false;  // found a matching miranda; we do not need a new entry
 653     }
 654   }
 655   return true; // found no match; we need a new entry
 656 }
 657 
 658 // Support for miranda methods
 659 
 660 // get the vtable index of a miranda method with matching "name" and "signature"
 661 int klassVtable::index_of_miranda(Symbol* name, Symbol* signature) {
 662   // search from the bottom, might be faster
 663   for (int i = (length() - 1); i >= 0; i--) {
 664     Method* m = table()[i].method();
 665     if (is_miranda_entry_at(i) &&
 666         m->name()->equals(name) && m->signature()->equals(signature)) {
 667       return i;
 668     }
 669   }
 670   return Method::invalid_vtable_index;
 671 }
 672 
 673 // check if an entry at an index is miranda
 674 // requires that method m at entry be declared ("held") by an interface.
 675 bool klassVtable::is_miranda_entry_at(int i) {
 676   Method* m = method_at(i);
 677   Klass* method_holder = m->method_holder();
 678   InstanceKlass *mhk = InstanceKlass::cast(method_holder);
 679 
 680   // miranda methods are public abstract instance interface methods in a class's vtable
 681   if (mhk->is_interface()) {
 682     assert(m->is_public(), "should be public");
 683     assert(ik()->implements_interface(method_holder) , "this class should implement the interface");
 684     // the search could find a miranda or a default method
 685     if (is_miranda(m, ik()->methods(), ik()->default_methods(), ik()->super())) {
 686       return true;
 687     }
 688   }
 689   return false;
 690 }
 691 
 692 // check if a method is a miranda method, given a class's methods table,
 693 // its default_method table  and its super
 694 // Miranda methods are calculated twice:
 695 // first: before vtable size calculation: including abstract and default
 696 // This is seen by default method creation
 697 // Second: recalculated during vtable initialization: only abstract
 698 // This is seen by link resolution and selection.
 699 // "miranda" means not static, not defined by this class.
 700 // private methods in interfaces do not belong in the miranda list.
 701 // the caller must make sure that the method belongs to an interface implemented by the class
 702 // Miranda methods only include public interface instance methods
 703 // Not private methods, not static methods, not default == concrete abstract
 704 // Miranda methods also do not include overpass methods in interfaces
 705 bool klassVtable::is_miranda(Method* m, Array<Method*>* class_methods,
 706                              Array<Method*>* default_methods, Klass* super) {
 707   if (m->is_static() || m->is_private() || m->is_overpass()) {
 708     return false;
 709   }
 710   Symbol* name = m->name();
 711   Symbol* signature = m->signature();
 712 
 713   if (InstanceKlass::find_instance_method(class_methods, name, signature) == NULL) {
 714     // did not find it in the method table of the current class
 715     if ((default_methods == NULL) ||
 716         InstanceKlass::find_method(default_methods, name, signature) == NULL) {
 717       if (super == NULL) {
 718         // super doesn't exist
 719         return true;
 720       }
 721 
 722       Method* mo = InstanceKlass::cast(super)->lookup_method(name, signature);
 723       while (mo != NULL && mo->access_flags().is_static()
 724              && mo->method_holder() != NULL
 725              && mo->method_holder()->super() != NULL)
 726       {
 727          mo = mo->method_holder()->super()->uncached_lookup_method(name, signature, Klass::find_overpass);
 728       }
 729       if (mo == NULL || mo->access_flags().is_private() ) {
 730         // super class hierarchy does not implement it or protection is different
 731         return true;
 732       }
 733     }
 734   }
 735 
 736   return false;
 737 }
 738 
 739 // Scans current_interface_methods for miranda methods that do not
 740 // already appear in new_mirandas, or default methods,  and are also not defined-and-non-private
 741 // in super (superclass).  These mirandas are added to all_mirandas if it is
 742 // not null; in addition, those that are not duplicates of miranda methods
 743 // inherited by super from its interfaces are added to new_mirandas.
 744 // Thus, new_mirandas will be the set of mirandas that this class introduces,
 745 // all_mirandas will be the set of all mirandas applicable to this class
 746 // including all defined in superclasses.
 747 void klassVtable::add_new_mirandas_to_lists(
 748     GrowableArray<Method*>* new_mirandas, GrowableArray<Method*>* all_mirandas,
 749     Array<Method*>* current_interface_methods, Array<Method*>* class_methods,
 750     Array<Method*>* default_methods, Klass* super) {
 751 
 752   // iterate thru the current interface's method to see if it a miranda
 753   int num_methods = current_interface_methods->length();
 754   for (int i = 0; i < num_methods; i++) {
 755     Method* im = current_interface_methods->at(i);
 756     bool is_duplicate = false;
 757     int num_of_current_mirandas = new_mirandas->length();
 758     // check for duplicate mirandas in different interfaces we implement
 759     for (int j = 0; j < num_of_current_mirandas; j++) {
 760       Method* miranda = new_mirandas->at(j);
 761       if ((im->name()->equals(miranda->name())) &&
 762           (im->signature()->equals(miranda->signature()))) {
 763         is_duplicate = true;
 764         break;
 765       }
 766     }
 767 
 768     if (!is_duplicate) { // we don't want duplicate miranda entries in the vtable
 769       if (is_miranda(im, class_methods, default_methods, super)) { // is it a miranda at all?
 770         InstanceKlass *sk = InstanceKlass::cast(super);
 771         // check if it is a duplicate of a super's miranda
 772         if (sk->lookup_method_in_all_interfaces(im->name(), im->signature(), Klass::find_defaults) == NULL) {
 773           new_mirandas->append(im);
 774         }
 775         if (all_mirandas != NULL) {
 776           all_mirandas->append(im);
 777         }
 778       }
 779     }
 780   }
 781 }
 782 
 783 void klassVtable::get_mirandas(GrowableArray<Method*>* new_mirandas,
 784                                GrowableArray<Method*>* all_mirandas,
 785                                Klass* super, Array<Method*>* class_methods,
 786                                Array<Method*>* default_methods,
 787                                Array<Klass*>* local_interfaces) {
 788   assert((new_mirandas->length() == 0) , "current mirandas must be 0");
 789 
 790   // iterate thru the local interfaces looking for a miranda
 791   int num_local_ifs = local_interfaces->length();
 792   for (int i = 0; i < num_local_ifs; i++) {
 793     InstanceKlass *ik = InstanceKlass::cast(local_interfaces->at(i));
 794     add_new_mirandas_to_lists(new_mirandas, all_mirandas,
 795                               ik->methods(), class_methods,
 796                               default_methods, super);
 797     // iterate thru each local's super interfaces
 798     Array<Klass*>* super_ifs = ik->transitive_interfaces();
 799     int num_super_ifs = super_ifs->length();
 800     for (int j = 0; j < num_super_ifs; j++) {
 801       InstanceKlass *sik = InstanceKlass::cast(super_ifs->at(j));
 802       add_new_mirandas_to_lists(new_mirandas, all_mirandas,
 803                                 sik->methods(), class_methods,
 804                                 default_methods, super);
 805     }
 806   }
 807 }
 808 
 809 // Discover miranda methods ("miranda" = "interface abstract, no binding"),
 810 // and append them into the vtable starting at index initialized,
 811 // return the new value of initialized.
 812 // Miranda methods use vtable entries, but do not get assigned a vtable_index
 813 // The vtable_index is discovered by searching from the end of the vtable
 814 int klassVtable::fill_in_mirandas(int initialized) {
 815   GrowableArray<Method*> mirandas(20);
 816   get_mirandas(&mirandas, NULL, ik()->super(), ik()->methods(),
 817                ik()->default_methods(), ik()->local_interfaces());
 818   for (int i = 0; i < mirandas.length(); i++) {
 819     if (PrintVtables && Verbose) {
 820       Method* meth = mirandas.at(i);
 821       ResourceMark rm(Thread::current());
 822       if (meth != NULL) {
 823         char* sig = meth->name_and_sig_as_C_string();
 824         tty->print("fill in mirandas with %s index %d, flags: ",
 825           sig, initialized);
 826         meth->access_flags().print_on(tty);
 827         if (meth->is_default_method()) {
 828           tty->print("default ");
 829         }
 830         tty->cr();
 831       }
 832     }
 833     put_method_at(mirandas.at(i), initialized);
 834     ++initialized;
 835   }
 836   return initialized;
 837 }
 838 
 839 // Copy this class's vtable to the vtable beginning at start.
 840 // Used to copy superclass vtable to prefix of subclass's vtable.
 841 void klassVtable::copy_vtable_to(vtableEntry* start) {
 842   Copy::disjoint_words((HeapWord*)table(), (HeapWord*)start, _length * vtableEntry::size());
 843 }
 844 
 845 #if INCLUDE_JVMTI
 846 bool klassVtable::adjust_default_method(int vtable_index, Method* old_method, Method* new_method) {
 847   // If old_method is default, find this vtable index in default_vtable_indices
 848   // and replace that method in the _default_methods list
 849   bool updated = false;
 850 
 851   Array<Method*>* default_methods = ik()->default_methods();
 852   if (default_methods != NULL) {
 853     int len = default_methods->length();
 854     for (int idx = 0; idx < len; idx++) {
 855       if (vtable_index == ik()->default_vtable_indices()->at(idx)) {
 856         if (default_methods->at(idx) == old_method) {
 857           default_methods->at_put(idx, new_method);
 858           updated = true;
 859         }
 860         break;
 861       }
 862     }
 863   }
 864   return updated;
 865 }
 866 
 867 // search the vtable for uses of either obsolete or EMCP methods
 868 void klassVtable::adjust_method_entries(InstanceKlass* holder, bool * trace_name_printed) {
 869   int prn_enabled = 0;
 870   for (int index = 0; index < length(); index++) {
 871     Method* old_method = unchecked_method_at(index);
 872     if (old_method == NULL || old_method->method_holder() != holder || !old_method->is_old()) {
 873       continue; // skip uninteresting entries
 874     }
 875     assert(!old_method->is_deleted(), "vtable methods may not be deleted");
 876 
 877     Method* new_method = holder->method_with_idnum(old_method->orig_method_idnum());
 878 
 879     assert(new_method != NULL, "method_with_idnum() should not be NULL");
 880     assert(old_method != new_method, "sanity check");
 881 
 882     put_method_at(new_method, index);
 883     // For default methods, need to update the _default_methods array
 884     // which can only have one method entry for a given signature
 885     bool updated_default = false;
 886     if (old_method->is_default_method()) {
 887       updated_default = adjust_default_method(index, old_method, new_method);
 888     }
 889 
 890     if (RC_TRACE_IN_RANGE(0x00100000, 0x00400000)) {
 891       if (!(*trace_name_printed)) {
 892         // RC_TRACE_MESG macro has an embedded ResourceMark
 893         RC_TRACE_MESG(("adjust: klassname=%s for methods from name=%s",
 894                        klass()->external_name(),
 895                        old_method->method_holder()->external_name()));
 896         *trace_name_printed = true;
 897       }
 898       // RC_TRACE macro has an embedded ResourceMark
 899       RC_TRACE(0x00100000, ("vtable method update: %s(%s), updated default = %s",
 900                             new_method->name()->as_C_string(),
 901                             new_method->signature()->as_C_string(),
 902                             updated_default ? "true" : "false"));
 903     }
 904   }
 905 }
 906 
 907 // a vtable should never contain old or obsolete methods
 908 bool klassVtable::check_no_old_or_obsolete_entries() {
 909   for (int i = 0; i < length(); i++) {
 910     Method* m = unchecked_method_at(i);
 911     if (m != NULL &&
 912         (NOT_PRODUCT(!m->is_valid() ||) m->is_old() || m->is_obsolete())) {
 913       return false;
 914     }
 915   }
 916   return true;
 917 }
 918 
 919 void klassVtable::dump_vtable() {
 920   tty->print_cr("vtable dump --");
 921   for (int i = 0; i < length(); i++) {
 922     Method* m = unchecked_method_at(i);
 923     if (m != NULL) {
 924       tty->print("      (%5d)  ", i);
 925       m->access_flags().print_on(tty);
 926       if (m->is_default_method()) {
 927         tty->print("default ");
 928       }
 929       if (m->is_overpass()) {
 930         tty->print("overpass");
 931       }
 932       tty->print(" --  ");
 933       m->print_name(tty);
 934       tty->cr();
 935     }
 936   }
 937 }
 938 #endif // INCLUDE_JVMTI
 939 
 940 // CDS/RedefineClasses support - clear vtables so they can be reinitialized
 941 void klassVtable::clear_vtable() {
 942   for (int i = 0; i < _length; i++) table()[i].clear();
 943 }
 944 
 945 bool klassVtable::is_initialized() {
 946   return _length == 0 || table()[0].method() != NULL;
 947 }
 948 
 949 //-----------------------------------------------------------------------------------------
 950 // Itable code
 951 
 952 // Initialize a itableMethodEntry
 953 void itableMethodEntry::initialize(Method* m) {
 954   if (m == NULL) return;
 955 
 956   _method = m;
 957 }
 958 
 959 klassItable::klassItable(instanceKlassHandle klass) {
 960   _klass = klass;
 961 
 962   if (klass->itable_length() > 0) {
 963     itableOffsetEntry* offset_entry = (itableOffsetEntry*)klass->start_of_itable();
 964     if (offset_entry  != NULL && offset_entry->interface_klass() != NULL) { // Check that itable is initialized
 965       // First offset entry points to the first method_entry
 966       intptr_t* method_entry  = (intptr_t *)(((address)klass()) + offset_entry->offset());
 967       intptr_t* end         = klass->end_of_itable();
 968 
 969       _table_offset      = (intptr_t*)offset_entry - (intptr_t*)klass();
 970       _size_offset_table = (method_entry - ((intptr_t*)offset_entry)) / itableOffsetEntry::size();
 971       _size_method_table = (end - method_entry)                  / itableMethodEntry::size();
 972       assert(_table_offset >= 0 && _size_offset_table >= 0 && _size_method_table >= 0, "wrong computation");
 973       return;
 974     }
 975   }
 976 
 977   // The length of the itable was either zero, or it has not yet been initialized.
 978   _table_offset      = 0;
 979   _size_offset_table = 0;
 980   _size_method_table = 0;
 981 }
 982 
 983 static int initialize_count = 0;
 984 
 985 // Initialization
 986 void klassItable::initialize_itable(bool checkconstraints, TRAPS) {
 987   if (_klass->is_interface()) {
 988     // This needs to go after vtable indices are assigned but
 989     // before implementors need to know the number of itable indices.
 990     assign_itable_indices_for_interface(_klass());
 991   }
 992 
 993   // Cannot be setup doing bootstrapping, interfaces don't have
 994   // itables, and klass with only ones entry have empty itables
 995   if (Universe::is_bootstrapping() ||
 996       _klass->is_interface() ||
 997       _klass->itable_length() == itableOffsetEntry::size()) return;
 998 
 999   // There's alway an extra itable entry so we can null-terminate it.
1000   guarantee(size_offset_table() >= 1, "too small");
1001   int num_interfaces = size_offset_table() - 1;
1002   if (num_interfaces > 0) {
1003     if (TraceItables) tty->print_cr("%3d: Initializing itables for %s", ++initialize_count,
1004                                     _klass->name()->as_C_string());
1005 
1006 
1007     // Iterate through all interfaces
1008     int i;
1009     for(i = 0; i < num_interfaces; i++) {
1010       itableOffsetEntry* ioe = offset_entry(i);
1011       HandleMark hm(THREAD);
1012       KlassHandle interf_h (THREAD, ioe->interface_klass());
1013       assert(interf_h() != NULL && ioe->offset() != 0, "bad offset entry in itable");
1014       initialize_itable_for_interface(ioe->offset(), interf_h, checkconstraints, CHECK);
1015     }
1016 
1017   }
1018   // Check that the last entry is empty
1019   itableOffsetEntry* ioe = offset_entry(size_offset_table() - 1);
1020   guarantee(ioe->interface_klass() == NULL && ioe->offset() == 0, "terminator entry missing");
1021 }
1022 
1023 
1024 inline bool interface_method_needs_itable_index(Method* m) {
1025   if (m->is_static())           return false;   // e.g., Stream.empty
1026   if (m->is_initializer())      return false;   // <init> or <clinit>
1027   // If an interface redeclares a method from java.lang.Object,
1028   // it should already have a vtable index, don't touch it.
1029   // e.g., CharSequence.toString (from initialize_vtable)
1030   // if (m->has_vtable_index())  return false; // NO!
1031   return true;
1032 }
1033 
1034 int klassItable::assign_itable_indices_for_interface(Klass* klass) {
1035   // an interface does not have an itable, but its methods need to be numbered
1036   if (TraceItables) tty->print_cr("%3d: Initializing itable for interface %s", ++initialize_count,
1037                                   klass->name()->as_C_string());
1038   Array<Method*>* methods = InstanceKlass::cast(klass)->methods();
1039   int nof_methods = methods->length();
1040   int ime_num = 0;
1041   for (int i = 0; i < nof_methods; i++) {
1042     Method* m = methods->at(i);
1043     if (interface_method_needs_itable_index(m)) {
1044       assert(!m->is_final_method(), "no final interface methods");
1045       // If m is already assigned a vtable index, do not disturb it.
1046       if (TraceItables && Verbose) {
1047         ResourceMark rm;
1048         const char* sig = (m != NULL) ? m->name_and_sig_as_C_string() : "<NULL>";
1049         if (m->has_vtable_index()) {
1050           tty->print("itable index %d for method: %s, flags: ", m->vtable_index(), sig);
1051         } else {
1052           tty->print("itable index %d for method: %s, flags: ", ime_num, sig);
1053         }
1054         if (m != NULL) {
1055           m->access_flags().print_on(tty);
1056           if (m->is_default_method()) {
1057             tty->print("default ");
1058           }
1059           if (m->is_overpass()) {
1060             tty->print("overpass");
1061           }
1062         }
1063         tty->cr();
1064       }
1065       if (!m->has_vtable_index()) {
1066         assert(m->vtable_index() == Method::pending_itable_index, "set by initialize_vtable");
1067         m->set_itable_index(ime_num);
1068         // Progress to next itable entry
1069         ime_num++;
1070       }
1071     }
1072   }
1073   assert(ime_num == method_count_for_interface(klass), "proper sizing");
1074   return ime_num;
1075 }
1076 
1077 int klassItable::method_count_for_interface(Klass* interf) {
1078   assert(interf->oop_is_instance(), "must be");
1079   assert(interf->is_interface(), "must be");
1080   Array<Method*>* methods = InstanceKlass::cast(interf)->methods();
1081   int nof_methods = methods->length();
1082   while (nof_methods > 0) {
1083     Method* m = methods->at(nof_methods-1);
1084     if (m->has_itable_index()) {
1085       int length = m->itable_index() + 1;
1086 #ifdef ASSERT
1087       while (nof_methods = 0) {
1088         m = methods->at(--nof_methods);
1089         assert(!m->has_itable_index() || m->itable_index() < length, "");
1090       }
1091 #endif //ASSERT
1092       return length;  // return the rightmost itable index, plus one
1093     }
1094     nof_methods -= 1;
1095   }
1096   // no methods have itable indices
1097   return 0;
1098 }
1099 
1100 
1101 void klassItable::initialize_itable_for_interface(int method_table_offset, KlassHandle interf_h, bool checkconstraints, TRAPS) {
1102   Array<Method*>* methods = InstanceKlass::cast(interf_h())->methods();
1103   int nof_methods = methods->length();
1104   HandleMark hm;
1105   assert(nof_methods > 0, "at least one method must exist for interface to be in vtable");
1106   Handle interface_loader (THREAD, InstanceKlass::cast(interf_h())->class_loader());
1107 
1108   int ime_count = method_count_for_interface(interf_h());
1109   for (int i = 0; i < nof_methods; i++) {
1110     Method* m = methods->at(i);
1111     methodHandle target;
1112     if (m->has_itable_index()) {
1113       // This search must match the runtime resolution, i.e. selection search for invokeinterface
1114       // to correctly enforce loader constraints for interface method inheritance
1115       LinkResolver::lookup_instance_method_in_klasses(target, _klass, m->name(), m->signature(), CHECK);
1116     }
1117     if (target == NULL || !target->is_public() || target->is_abstract()) {
1118       // Entry does not resolve. Leave it empty for AbstractMethodError.
1119         if (!(target == NULL) && !target->is_public()) {
1120           // Stuff an IllegalAccessError throwing method in there instead.
1121           itableOffsetEntry::method_entry(_klass(), method_table_offset)[m->itable_index()].
1122               initialize(Universe::throw_illegal_access_error());
1123         }
1124     } else {
1125       // Entry did resolve, check loader constraints before initializing
1126       // if checkconstraints requested
1127       if (checkconstraints) {
1128         Handle method_holder_loader (THREAD, target->method_holder()->class_loader());
1129         if (method_holder_loader() != interface_loader()) {
1130           ResourceMark rm(THREAD);
1131           Symbol* failed_type_symbol =
1132             SystemDictionary::check_signature_loaders(m->signature(),
1133                                                       method_holder_loader,
1134                                                       interface_loader,
1135                                                       true, CHECK);
1136           if (failed_type_symbol != NULL) {
1137             const char* msg = "loader constraint violation in interface "
1138               "itable initialization: when resolving method \"%s\" the class"
1139               " loader (instance of %s) of the current class, %s, "
1140               "and the class loader (instance of %s) for interface "
1141               "%s have different Class objects for the type %s "
1142               "used in the signature";
1143             char* sig = target()->name_and_sig_as_C_string();
1144             const char* loader1 = SystemDictionary::loader_name(method_holder_loader());
1145             char* current = _klass->name()->as_C_string();
1146             const char* loader2 = SystemDictionary::loader_name(interface_loader());
1147             char* iface = InstanceKlass::cast(interf_h())->name()->as_C_string();
1148             char* failed_type_name = failed_type_symbol->as_C_string();
1149             size_t buflen = strlen(msg) + strlen(sig) + strlen(loader1) +
1150               strlen(current) + strlen(loader2) + strlen(iface) +
1151               strlen(failed_type_name);
1152             char* buf = NEW_RESOURCE_ARRAY_IN_THREAD(THREAD, char, buflen);
1153             jio_snprintf(buf, buflen, msg, sig, loader1, current, loader2,
1154                          iface, failed_type_name);
1155             THROW_MSG(vmSymbols::java_lang_LinkageError(), buf);
1156           }
1157         }
1158       }
1159 
1160       // ime may have moved during GC so recalculate address
1161       int ime_num = m->itable_index();
1162       assert(ime_num < ime_count, "oob");
1163       itableOffsetEntry::method_entry(_klass(), method_table_offset)[ime_num].initialize(target());
1164       if (TraceItables && Verbose) {
1165         ResourceMark rm(THREAD);
1166         if (target() != NULL) {
1167           char* sig = target()->name_and_sig_as_C_string();
1168           tty->print("interface: %s, ime_num: %d, target: %s, method_holder: %s ",
1169                     interf_h()->internal_name(), ime_num, sig,
1170                     target()->method_holder()->internal_name());
1171           tty->print("target_method flags: ");
1172           target()->access_flags().print_on(tty);
1173           if (target()->is_default_method()) {
1174             tty->print("default ");
1175           }
1176           tty->cr();
1177         }
1178       }
1179     }
1180   }
1181 }
1182 
1183 // Update entry for specific Method*
1184 void klassItable::initialize_with_method(Method* m) {
1185   itableMethodEntry* ime = method_entry(0);
1186   for(int i = 0; i < _size_method_table; i++) {
1187     if (ime->method() == m) {
1188       ime->initialize(m);
1189     }
1190     ime++;
1191   }
1192 }
1193 
1194 #if INCLUDE_JVMTI
1195 // search the itable for uses of either obsolete or EMCP methods
1196 void klassItable::adjust_method_entries(InstanceKlass* holder, bool * trace_name_printed) {
1197 
1198   itableMethodEntry* ime = method_entry(0);
1199   for (int i = 0; i < _size_method_table; i++, ime++) {
1200     Method* old_method = ime->method();
1201     if (old_method == NULL || old_method->method_holder() != holder || !old_method->is_old()) {
1202       continue; // skip uninteresting entries
1203     }
1204     assert(!old_method->is_deleted(), "itable methods may not be deleted");
1205 
1206     Method* new_method = holder->method_with_idnum(old_method->orig_method_idnum());
1207 
1208     assert(new_method != NULL, "method_with_idnum() should not be NULL");
1209     assert(old_method != new_method, "sanity check");
1210 
1211     ime->initialize(new_method);
1212 
1213     if (RC_TRACE_IN_RANGE(0x00100000, 0x00400000)) {
1214       if (!(*trace_name_printed)) {
1215         // RC_TRACE_MESG macro has an embedded ResourceMark
1216         RC_TRACE_MESG(("adjust: name=%s",
1217           old_method->method_holder()->external_name()));
1218         *trace_name_printed = true;
1219       }
1220       // RC_TRACE macro has an embedded ResourceMark
1221       RC_TRACE(0x00200000, ("itable method update: %s(%s)",
1222         new_method->name()->as_C_string(),
1223         new_method->signature()->as_C_string()));
1224     }
1225   }
1226 }
1227 
1228 // an itable should never contain old or obsolete methods
1229 bool klassItable::check_no_old_or_obsolete_entries() {
1230   itableMethodEntry* ime = method_entry(0);
1231   for (int i = 0; i < _size_method_table; i++) {
1232     Method* m = ime->method();
1233     if (m != NULL &&
1234         (NOT_PRODUCT(!m->is_valid() ||) m->is_old() || m->is_obsolete())) {
1235       return false;
1236     }
1237     ime++;
1238   }
1239   return true;
1240 }
1241 
1242 void klassItable::dump_itable() {
1243   itableMethodEntry* ime = method_entry(0);
1244   tty->print_cr("itable dump --");
1245   for (int i = 0; i < _size_method_table; i++) {
1246     Method* m = ime->method();
1247     if (m != NULL) {
1248       tty->print("      (%5d)  ", i);
1249       m->access_flags().print_on(tty);
1250       if (m->is_default_method()) {
1251         tty->print("default ");
1252       }
1253       tty->print(" --  ");
1254       m->print_name(tty);
1255       tty->cr();
1256     }
1257     ime++;
1258   }
1259 }
1260 #endif // INCLUDE_JVMTI
1261 
1262 
1263 // Setup
1264 class InterfaceVisiterClosure : public StackObj {
1265  public:
1266   virtual void doit(Klass* intf, int method_count) = 0;
1267 };
1268 
1269 // Visit all interfaces with at least one itable method
1270 void visit_all_interfaces(Array<Klass*>* transitive_intf, InterfaceVisiterClosure *blk) {
1271   // Handle array argument
1272   for(int i = 0; i < transitive_intf->length(); i++) {
1273     Klass* intf = transitive_intf->at(i);
1274     assert(intf->is_interface(), "sanity check");
1275 
1276     // Find no. of itable methods
1277     int method_count = 0;
1278     // method_count = klassItable::method_count_for_interface(intf);
1279     Array<Method*>* methods = InstanceKlass::cast(intf)->methods();
1280     if (methods->length() > 0) {
1281       for (int i = methods->length(); --i >= 0; ) {
1282         if (interface_method_needs_itable_index(methods->at(i))) {
1283           method_count++;
1284         }
1285       }
1286     }
1287 
1288     // Only count interfaces with at least one method
1289     if (method_count > 0) {
1290       blk->doit(intf, method_count);
1291     }
1292   }
1293 }
1294 
1295 class CountInterfacesClosure : public InterfaceVisiterClosure {
1296  private:
1297   int _nof_methods;
1298   int _nof_interfaces;
1299  public:
1300    CountInterfacesClosure() { _nof_methods = 0; _nof_interfaces = 0; }
1301 
1302    int nof_methods() const    { return _nof_methods; }
1303    int nof_interfaces() const { return _nof_interfaces; }
1304 
1305    void doit(Klass* intf, int method_count) { _nof_methods += method_count; _nof_interfaces++; }
1306 };
1307 
1308 class SetupItableClosure : public InterfaceVisiterClosure  {
1309  private:
1310   itableOffsetEntry* _offset_entry;
1311   itableMethodEntry* _method_entry;
1312   address            _klass_begin;
1313  public:
1314   SetupItableClosure(address klass_begin, itableOffsetEntry* offset_entry, itableMethodEntry* method_entry) {
1315     _klass_begin  = klass_begin;
1316     _offset_entry = offset_entry;
1317     _method_entry = method_entry;
1318   }
1319 
1320   itableMethodEntry* method_entry() const { return _method_entry; }
1321 
1322   void doit(Klass* intf, int method_count) {
1323     int offset = ((address)_method_entry) - _klass_begin;
1324     _offset_entry->initialize(intf, offset);
1325     _offset_entry++;
1326     _method_entry += method_count;
1327   }
1328 };
1329 
1330 int klassItable::compute_itable_size(Array<Klass*>* transitive_interfaces) {
1331   // Count no of interfaces and total number of interface methods
1332   CountInterfacesClosure cic;
1333   visit_all_interfaces(transitive_interfaces, &cic);
1334 
1335   // There's alway an extra itable entry so we can null-terminate it.
1336   int itable_size = calc_itable_size(cic.nof_interfaces() + 1, cic.nof_methods());
1337 
1338   // Statistics
1339   update_stats(itable_size * HeapWordSize);
1340 
1341   return itable_size;
1342 }
1343 
1344 
1345 // Fill out offset table and interface klasses into the itable space
1346 void klassItable::setup_itable_offset_table(instanceKlassHandle klass) {
1347   if (klass->itable_length() == 0) return;
1348   assert(!klass->is_interface(), "Should have zero length itable");
1349 
1350   // Count no of interfaces and total number of interface methods
1351   CountInterfacesClosure cic;
1352   visit_all_interfaces(klass->transitive_interfaces(), &cic);
1353   int nof_methods    = cic.nof_methods();
1354   int nof_interfaces = cic.nof_interfaces();
1355 
1356   // Add one extra entry so we can null-terminate the table
1357   nof_interfaces++;
1358 
1359   assert(compute_itable_size(klass->transitive_interfaces()) ==
1360          calc_itable_size(nof_interfaces, nof_methods),
1361          "mismatch calculation of itable size");
1362 
1363   // Fill-out offset table
1364   itableOffsetEntry* ioe = (itableOffsetEntry*)klass->start_of_itable();
1365   itableMethodEntry* ime = (itableMethodEntry*)(ioe + nof_interfaces);
1366   intptr_t* end               = klass->end_of_itable();
1367   assert((oop*)(ime + nof_methods) <= (oop*)klass->start_of_nonstatic_oop_maps(), "wrong offset calculation (1)");
1368   assert((oop*)(end) == (oop*)(ime + nof_methods),                      "wrong offset calculation (2)");
1369 
1370   // Visit all interfaces and initialize itable offset table
1371   SetupItableClosure sic((address)klass(), ioe, ime);
1372   visit_all_interfaces(klass->transitive_interfaces(), &sic);
1373 
1374 #ifdef ASSERT
1375   ime  = sic.method_entry();
1376   oop* v = (oop*) klass->end_of_itable();
1377   assert( (oop*)(ime) == v, "wrong offset calculation (2)");
1378 #endif
1379 }
1380 
1381 
1382 // inverse to itable_index
1383 Method* klassItable::method_for_itable_index(Klass* intf, int itable_index) {
1384   assert(InstanceKlass::cast(intf)->is_interface(), "sanity check");
1385   assert(intf->verify_itable_index(itable_index), "");
1386   Array<Method*>* methods = InstanceKlass::cast(intf)->methods();
1387 
1388   if (itable_index < 0 || itable_index >= method_count_for_interface(intf))
1389     return NULL;                // help caller defend against bad indices
1390 
1391   int index = itable_index;
1392   Method* m = methods->at(index);
1393   int index2 = -1;
1394   while (!m->has_itable_index() ||
1395          (index2 = m->itable_index()) != itable_index) {
1396     assert(index2 < itable_index, "monotonic");
1397     if (++index == methods->length())
1398       return NULL;
1399     m = methods->at(index);
1400   }
1401   assert(m->itable_index() == itable_index, "correct inverse");
1402 
1403   return m;
1404 }
1405 
1406 void klassVtable::verify(outputStream* st, bool forced) {
1407   // make sure table is initialized
1408   if (!Universe::is_fully_initialized()) return;
1409 #ifndef PRODUCT
1410   // avoid redundant verifies
1411   if (!forced && _verify_count == Universe::verify_count()) return;
1412   _verify_count = Universe::verify_count();
1413 #endif
1414   oop* end_of_obj = (oop*)_klass() + _klass()->size();
1415   oop* end_of_vtable = (oop *)&table()[_length];
1416   if (end_of_vtable > end_of_obj) {
1417     fatal(err_msg("klass %s: klass object too short (vtable extends beyond "
1418                   "end)", _klass->internal_name()));
1419   }
1420 
1421   for (int i = 0; i < _length; i++) table()[i].verify(this, st);
1422   // verify consistency with superKlass vtable
1423   Klass* super = _klass->super();
1424   if (super != NULL) {
1425     InstanceKlass* sk = InstanceKlass::cast(super);
1426     klassVtable* vt = sk->vtable();
1427     for (int i = 0; i < vt->length(); i++) {
1428       verify_against(st, vt, i);
1429     }
1430   }
1431 }
1432 
1433 void klassVtable::verify_against(outputStream* st, klassVtable* vt, int index) {
1434   vtableEntry* vte = &vt->table()[index];
1435   if (vte->method()->name()->not_equals(table()[index].method()->name()) ||
1436       vte->method()->signature()->not_equals(table()[index].method()->signature())) {
1437     fatal("mismatched name/signature of vtable entries");
1438   }
1439 }
1440 
1441 #ifndef PRODUCT
1442 void klassVtable::print() {
1443   ResourceMark rm;
1444   tty->print("klassVtable for klass %s (length %d):\n", _klass->internal_name(), length());
1445   for (int i = 0; i < length(); i++) {
1446     table()[i].print();
1447     tty->cr();
1448   }
1449 }
1450 #endif
1451 
1452 void vtableEntry::verify(klassVtable* vt, outputStream* st) {
1453   NOT_PRODUCT(FlagSetting fs(IgnoreLockingAssertions, true));
1454   assert(method() != NULL, "must have set method");
1455   method()->verify();
1456   // we sub_type, because it could be a miranda method
1457   if (!vt->klass()->is_subtype_of(method()->method_holder())) {
1458 #ifndef PRODUCT
1459     print();
1460 #endif
1461     fatal(err_msg("vtableEntry " PTR_FORMAT ": method is from subclass", this));
1462   }
1463 }
1464 
1465 #ifndef PRODUCT
1466 
1467 void vtableEntry::print() {
1468   ResourceMark rm;
1469   tty->print("vtableEntry %s: ", method()->name()->as_C_string());
1470   if (Verbose) {
1471     tty->print("m %#lx ", (address)method());
1472   }
1473 }
1474 
1475 class VtableStats : AllStatic {
1476  public:
1477   static int no_klasses;                // # classes with vtables
1478   static int no_array_klasses;          // # array classes
1479   static int no_instance_klasses;       // # instanceKlasses
1480   static int sum_of_vtable_len;         // total # of vtable entries
1481   static int sum_of_array_vtable_len;   // total # of vtable entries in array klasses only
1482   static int fixed;                     // total fixed overhead in bytes
1483   static int filler;                    // overhead caused by filler bytes
1484   static int entries;                   // total bytes consumed by vtable entries
1485   static int array_entries;             // total bytes consumed by array vtable entries
1486 
1487   static void do_class(Klass* k) {
1488     Klass* kl = k;
1489     klassVtable* vt = kl->vtable();
1490     if (vt == NULL) return;
1491     no_klasses++;
1492     if (kl->oop_is_instance()) {
1493       no_instance_klasses++;
1494       kl->array_klasses_do(do_class);
1495     }
1496     if (kl->oop_is_array()) {
1497       no_array_klasses++;
1498       sum_of_array_vtable_len += vt->length();
1499     }
1500     sum_of_vtable_len += vt->length();
1501   }
1502 
1503   static void compute() {
1504     SystemDictionary::classes_do(do_class);
1505     fixed  = no_klasses * oopSize;      // vtable length
1506     // filler size is a conservative approximation
1507     filler = oopSize * (no_klasses - no_instance_klasses) * (sizeof(InstanceKlass) - sizeof(ArrayKlass) - 1);
1508     entries = sizeof(vtableEntry) * sum_of_vtable_len;
1509     array_entries = sizeof(vtableEntry) * sum_of_array_vtable_len;
1510   }
1511 };
1512 
1513 int VtableStats::no_klasses = 0;
1514 int VtableStats::no_array_klasses = 0;
1515 int VtableStats::no_instance_klasses = 0;
1516 int VtableStats::sum_of_vtable_len = 0;
1517 int VtableStats::sum_of_array_vtable_len = 0;
1518 int VtableStats::fixed = 0;
1519 int VtableStats::filler = 0;
1520 int VtableStats::entries = 0;
1521 int VtableStats::array_entries = 0;
1522 
1523 void klassVtable::print_statistics() {
1524   ResourceMark rm;
1525   HandleMark hm;
1526   VtableStats::compute();
1527   tty->print_cr("vtable statistics:");
1528   tty->print_cr("%6d classes (%d instance, %d array)", VtableStats::no_klasses, VtableStats::no_instance_klasses, VtableStats::no_array_klasses);
1529   int total = VtableStats::fixed + VtableStats::filler + VtableStats::entries;
1530   tty->print_cr("%6d bytes fixed overhead (refs + vtable object header)", VtableStats::fixed);
1531   tty->print_cr("%6d bytes filler overhead", VtableStats::filler);
1532   tty->print_cr("%6d bytes for vtable entries (%d for arrays)", VtableStats::entries, VtableStats::array_entries);
1533   tty->print_cr("%6d bytes total", total);
1534 }
1535 
1536 int  klassItable::_total_classes;   // Total no. of classes with itables
1537 long klassItable::_total_size;      // Total no. of bytes used for itables
1538 
1539 void klassItable::print_statistics() {
1540  tty->print_cr("itable statistics:");
1541  tty->print_cr("%6d classes with itables", _total_classes);
1542  tty->print_cr("%6d K uses for itables (average by class: %d bytes)", _total_size / K, _total_size / _total_classes);
1543 }
1544 
1545 #endif // PRODUCT