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 "gc_implementation/shared/markSweep.inline.hpp"
  29 #include "memory/gcLocker.hpp"
  30 #include "memory/resourceArea.hpp"
  31 #include "memory/universe.inline.hpp"
  32 #include "oops/instanceKlass.hpp"
  33 #include "oops/klassVtable.hpp"
  34 #include "oops/method.hpp"
  35 #include "oops/objArrayOop.hpp"
  36 #include "oops/oop.inline.hpp"
  37 #include "prims/jvmtiRedefineClassesTrace.hpp"
  38 #include "runtime/arguments.hpp"
  39 #include "runtime/handles.inline.hpp"
  40 #include "utilities/copy.hpp"
  41 
  42 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
  43 
  44 inline InstanceKlass* klassVtable::ik() const {
  45   Klass* k = _klass();
  46   assert(k->oop_is_instance(), "not an InstanceKlass");
  47   return (InstanceKlass*)k;
  48 }
  49 
  50 
  51 // this function computes the vtable size (including the size needed for miranda
  52 // methods) and the number of miranda methods in this class.
  53 // Note on Miranda methods: Let's say there is a class C that implements
  54 // interface I, and none of C's superclasses implements I.
  55 // Let's say there is an abstract method m in I that neither C
  56 // nor any of its super classes implement (i.e there is no method of any access,
  57 // with the same name and signature as m), then m is a Miranda method which is
  58 // entered as a public abstract method in C's vtable.  From then on it should
  59 // treated as any other public method in C for method over-ride purposes.
  60 void klassVtable::compute_vtable_size_and_num_mirandas(
  61     int* vtable_length_ret, int* num_new_mirandas,
  62     GrowableArray<Method*>* all_mirandas, Klass* super,
  63     Array<Method*>* methods, AccessFlags class_flags,
  64     Handle classloader, Symbol* classname, Array<Klass*>* local_interfaces,
  65     TRAPS) {
  66   No_Safepoint_Verifier nsv;
  67 
  68   // set up default result values
  69   int vtable_length = 0;
  70 
  71   // start off with super's vtable length
  72   InstanceKlass* sk = (InstanceKlass*)super;
  73   vtable_length = super == NULL ? 0 : sk->vtable_length();
  74 
  75   // go thru each method in the methods table to see if it needs a new entry
  76   int len = methods->length();
  77   for (int i = 0; i < len; i++) {
  78     assert(methods->at(i)->is_method(), "must be a Method*");
  79     methodHandle mh(THREAD, methods->at(i));
  80 
  81     if (needs_new_vtable_entry(mh, super, classloader, classname, class_flags, THREAD)) {
  82       vtable_length += vtableEntry::size(); // we need a new entry
  83     }
  84   }
  85 
  86   GrowableArray<Method*> new_mirandas(20);
  87   // compute the number of mirandas methods that must be added to the end
  88   get_mirandas(&new_mirandas, all_mirandas, super, methods, NULL, local_interfaces);
  89   *num_new_mirandas = new_mirandas.length();
  90 
  91   // Interfaces do not need interface methods in their vtables
  92   // This includes miranda methods and during later processing, default methods
  93   if (!class_flags.is_interface()) {
  94     vtable_length += *num_new_mirandas * vtableEntry::size();
  95   }
  96 
  97   if (Universe::is_bootstrapping() && vtable_length == 0) {
  98     // array classes don't have their superclass set correctly during
  99     // bootstrapping
 100     vtable_length = Universe::base_vtable_size();
 101   }
 102 
 103   if (super == NULL && vtable_length != Universe::base_vtable_size()) {
 104     if (Universe::is_bootstrapping()) {
 105       // Someone is attempting to override java.lang.Object incorrectly on the
 106       // bootclasspath.  The JVM cannot recover from this error including throwing
 107       // an exception
 108       vm_exit_during_initialization("Incompatible definition of java.lang.Object");
 109     } else {
 110       // Someone is attempting to redefine java.lang.Object incorrectly.  The
 111       // only way this should happen is from
 112       // SystemDictionary::resolve_from_stream(), which will detect this later
 113       // and throw a security exception.  So don't assert here to let
 114       // the exception occur.
 115       vtable_length = Universe::base_vtable_size();
 116     }
 117   }
 118   assert(vtable_length % vtableEntry::size() == 0, "bad vtable length");
 119   assert(vtable_length >= Universe::base_vtable_size(), "vtable too small");
 120 
 121   *vtable_length_ret = vtable_length;
 122 }
 123 
 124 int klassVtable::index_of(Method* m, int len) const {
 125   assert(m->has_vtable_index(), "do not ask this of non-vtable methods");
 126   return m->vtable_index();
 127 }
 128 
 129 // Copy super class's vtable to the first part (prefix) of this class's vtable,
 130 // and return the number of entries copied.  Expects that 'super' is the Java
 131 // super class (arrays can have "array" super classes that must be skipped).
 132 int klassVtable::initialize_from_super(KlassHandle super) {
 133   if (super.is_null()) {
 134     return 0;
 135   } else {
 136     // copy methods from superKlass
 137     // can't inherit from array class, so must be InstanceKlass
 138     assert(super->oop_is_instance(), "must be instance klass");
 139     InstanceKlass* sk = (InstanceKlass*)super();
 140     klassVtable* superVtable = sk->vtable();
 141     assert(superVtable->length() <= _length, "vtable too short");
 142 #ifdef ASSERT
 143     superVtable->verify(tty, true);
 144 #endif
 145     superVtable->copy_vtable_to(table());
 146 #ifndef PRODUCT
 147     if (PrintVtables && Verbose) {
 148       ResourceMark rm;
 149       tty->print_cr("copy vtable from %s to %s size %d", sk->internal_name(), klass()->internal_name(), _length);
 150     }
 151 #endif
 152     return superVtable->length();
 153   }
 154 }
 155 
 156 //
 157 // Revised lookup semantics   introduced 1.3 (Kestrel beta)
 158 void klassVtable::initialize_vtable(bool checkconstraints, TRAPS) {
 159 
 160   // Note:  Arrays can have intermediate array supers.  Use java_super to skip them.
 161   KlassHandle super (THREAD, klass()->java_super());
 162   int nofNewEntries = 0;
 163 
 164   if (PrintVtables && !klass()->oop_is_array()) {
 165     ResourceMark rm(THREAD);
 166     tty->print_cr("Initializing: %s", _klass->name()->as_C_string());
 167   }
 168 
 169 #ifdef ASSERT
 170   oop* end_of_obj = (oop*)_klass() + _klass()->size();
 171   oop* end_of_vtable = (oop*)&table()[_length];
 172   assert(end_of_vtable <= end_of_obj, "vtable extends beyond end");
 173 #endif
 174 
 175   if (Universe::is_bootstrapping()) {
 176     // just clear everything
 177     for (int i = 0; i < _length; i++) table()[i].clear();
 178     return;
 179   }
 180 
 181   int super_vtable_len = initialize_from_super(super);
 182   if (klass()->oop_is_array()) {
 183     assert(super_vtable_len == _length, "arrays shouldn't introduce new methods");
 184   } else {
 185     assert(_klass->oop_is_instance(), "must be InstanceKlass");
 186 
 187     Array<Method*>* methods = ik()->methods();
 188     int len = methods->length();
 189     int initialized = super_vtable_len;
 190 
 191     // Check each of this class's methods against super;
 192     // if override, replace in copy of super vtable, otherwise append to end
 193     for (int i = 0; i < len; i++) {
 194       // update_inherited_vtable can stop for gc - ensure using handles
 195       HandleMark hm(THREAD);
 196       assert(methods->at(i)->is_method(), "must be a Method*");
 197       methodHandle mh(THREAD, methods->at(i));
 198 
 199       bool needs_new_entry = update_inherited_vtable(ik(), mh, super_vtable_len, -1, checkconstraints, CHECK);
 200 
 201       if (needs_new_entry) {
 202         put_method_at(mh(), initialized);
 203         mh()->set_vtable_index(initialized); // set primary vtable index
 204         initialized++;
 205       }
 206     }
 207 
 208     // update vtable with default_methods
 209     Array<Method*>* default_methods = ik()->default_methods();
 210     if (default_methods != NULL) {
 211       len = default_methods->length();
 212       if (len > 0) {
 213         Array<int>* def_vtable_indices = NULL;
 214         if ((def_vtable_indices = ik()->default_vtable_indices()) == NULL) {
 215           def_vtable_indices = ik()->create_new_default_vtable_indices(len, CHECK);
 216         } else {
 217           assert(def_vtable_indices->length() == len, "reinit vtable len?");
 218         }
 219         for (int i = 0; i < len; i++) {
 220           HandleMark hm(THREAD);
 221           assert(default_methods->at(i)->is_method(), "must be a Method*");
 222           methodHandle mh(THREAD, default_methods->at(i));
 223 
 224           bool needs_new_entry = update_inherited_vtable(ik(), mh, super_vtable_len, i, checkconstraints, CHECK);
 225 
 226           // needs new entry
 227           if (needs_new_entry) {
 228             put_method_at(mh(), initialized);
 229             def_vtable_indices->at_put(i, initialized); //set vtable index
 230             initialized++;
 231           }
 232         }
 233       }
 234     }
 235 
 236     // add miranda methods; it will also return the updated initialized
 237     // Interfaces do not need interface methods in their vtables
 238     // This includes miranda methods and during later processing, default methods
 239     if (!ik()->is_interface()) {
 240       initialized = fill_in_mirandas(initialized);
 241     }
 242 
 243     // In class hierarchies where the accessibility is not increasing (i.e., going from private ->
 244     // package_private -> public/protected), the vtable might actually be smaller than our initial
 245     // calculation.
 246     assert(initialized <= _length, "vtable initialization failed");
 247     for(;initialized < _length; initialized++) {
 248       put_method_at(NULL, initialized);
 249     }
 250     NOT_PRODUCT(verify(tty, true));
 251   }
 252 }
 253 
 254 // Called for cases where a method does not override its superclass' vtable entry
 255 // For bytecodes not produced by javac together it is possible that a method does not override
 256 // the superclass's method, but might indirectly override a super-super class's vtable entry
 257 // If none found, return a null superk, else return the superk of the method this does override
 258 // For public and protected methods: if they override a superclass, they will
 259 // also be overridden themselves appropriately.
 260 // Private methods do not override and are not overridden.
 261 // Package Private methods are trickier:
 262 // e.g. P1.A, pub m
 263 // P2.B extends A, package private m
 264 // P1.C extends B, public m
 265 // P1.C.m needs to override P1.A.m and can not override P2.B.m
 266 // Therefore: all package private methods need their own vtable entries for
 267 // them to be the root of an inheritance overriding decision
 268 // Package private methods may also override other vtable entries
 269 InstanceKlass* klassVtable::find_transitive_override(InstanceKlass* initialsuper, methodHandle target_method,
 270                             int vtable_index, Handle target_loader, Symbol* target_classname, Thread * THREAD) {
 271   InstanceKlass* superk = initialsuper;
 272   while (superk != NULL && superk->super() != NULL) {
 273     InstanceKlass* supersuperklass = InstanceKlass::cast(superk->super());
 274     klassVtable* ssVtable = supersuperklass->vtable();
 275     if (vtable_index < ssVtable->length()) {
 276       Method* super_method = ssVtable->method_at(vtable_index);
 277 #ifndef PRODUCT
 278       Symbol* name= target_method()->name();
 279       Symbol* signature = target_method()->signature();
 280       assert(super_method->name() == name && super_method->signature() == signature, "vtable entry name/sig mismatch");
 281 #endif
 282       if (supersuperklass->is_override(super_method, target_loader, target_classname, THREAD)) {
 283 #ifndef PRODUCT
 284         if (PrintVtables && Verbose) {
 285           ResourceMark rm(THREAD);
 286           char* sig = target_method()->name_and_sig_as_C_string();
 287           tty->print("transitive overriding superclass %s with %s::%s index %d, original flags: ",
 288            supersuperklass->internal_name(),
 289            _klass->internal_name(), sig, vtable_index);
 290            super_method->access_flags().print_on(tty);
 291            if (super_method->is_default_method()) {
 292              tty->print("default ");
 293            }
 294            tty->print("overriders flags: ");
 295            target_method->access_flags().print_on(tty);
 296            if (target_method->is_default_method()) {
 297              tty->print("default ");
 298            }
 299         }
 300 #endif /*PRODUCT*/
 301         break; // return found superk
 302       }
 303     } else  {
 304       // super class has no vtable entry here, stop transitive search
 305       superk = (InstanceKlass*)NULL;
 306       break;
 307     }
 308     // if no override found yet, continue to search up
 309     superk = InstanceKlass::cast(superk->super());
 310   }
 311 
 312   return superk;
 313 }
 314 
 315 // Update child's copy of super vtable for overrides
 316 // OR return true if a new vtable entry is required.
 317 // Only called for InstanceKlass's, i.e. not for arrays
 318 // If that changed, could not use _klass as handle for klass
 319 bool klassVtable::update_inherited_vtable(InstanceKlass* klass, methodHandle target_method,
 320                                           int super_vtable_len, int default_index,
 321                                           bool checkconstraints, TRAPS) {
 322   ResourceMark rm;
 323   bool allocate_new = true;
 324   assert(klass->oop_is_instance(), "must be InstanceKlass");
 325 
 326   Array<int>* def_vtable_indices = NULL;
 327   bool is_default = false;
 328   // default methods are concrete methods in superinterfaces which are added to the vtable
 329   // with their real method_holder
 330   // Since vtable and itable indices share the same storage, don't touch
 331   // the default method's real vtable/itable index
 332   // default_vtable_indices stores the vtable value relative to this inheritor
 333   if (default_index >= 0 ) {
 334     is_default = true;
 335     def_vtable_indices = klass->default_vtable_indices();
 336     assert(def_vtable_indices != NULL, "def vtable alloc?");
 337     assert(default_index <= def_vtable_indices->length(), "def vtable len?");
 338   } else {
 339     assert(klass == target_method()->method_holder(), "caller resp.");
 340     // Initialize the method's vtable index to "nonvirtual".
 341     // If we allocate a vtable entry, we will update it to a non-negative number.
 342     target_method()->set_vtable_index(Method::nonvirtual_vtable_index);
 343   }
 344 
 345   // Static and <init> methods are never in
 346   if (target_method()->is_static() || target_method()->name() ==  vmSymbols::object_initializer_name()) {
 347     return false;
 348   }
 349 
 350   if (target_method->is_final_method(klass->access_flags())) {
 351     // a final method never needs a new entry; final methods can be statically
 352     // resolved and they have to be present in the vtable only if they override
 353     // a super's method, in which case they re-use its entry
 354     allocate_new = false;
 355   } else if (klass->is_interface()) {
 356     allocate_new = false;  // see note below in needs_new_vtable_entry
 357     // An interface never allocates new vtable slots, only inherits old ones.
 358     // This method will either be assigned its own itable index later,
 359     // or be assigned an inherited vtable index in the loop below.
 360     // default methods inherited by classes store their vtable indices
 361     // in the inheritor's default_vtable_indices
 362     // default methods inherited by interfaces may already have a
 363     // valid itable index, if so, don't change it
 364     // overpass methods in an interface will be assigned an itable index later
 365     // by an inheriting class
 366     if (!is_default || !target_method()->has_itable_index()) {
 367       target_method()->set_vtable_index(Method::pending_itable_index);
 368     }
 369   }
 370 
 371   // we need a new entry if there is no superclass
 372   if (klass->super() == NULL) {
 373     return allocate_new;
 374   }
 375 
 376   // private methods in classes always have a new entry in the vtable
 377   // specification interpretation since classic has
 378   // private methods not overriding
 379   // JDK8 adds private methods in interfaces which require invokespecial
 380   if (target_method()->is_private()) {
 381     return allocate_new;
 382   }
 383 
 384   // search through the vtable and update overridden entries
 385   // Since check_signature_loaders acquires SystemDictionary_lock
 386   // which can block for gc, once we are in this loop, use handles
 387   // For classfiles built with >= jdk7, we now look for transitive overrides
 388 
 389   Symbol* name = target_method()->name();
 390   Symbol* signature = target_method()->signature();
 391 
 392   KlassHandle target_klass(THREAD, target_method()->method_holder());
 393   if (target_klass == NULL) {
 394     target_klass = _klass;
 395   }
 396 
 397   Handle target_loader(THREAD, target_klass->class_loader());
 398 
 399   Symbol* target_classname = target_klass->name();
 400   for(int i = 0; i < super_vtable_len; i++) {
 401     Method* super_method = method_at(i);
 402     // Check if method name matches
 403     if (super_method->name() == name && super_method->signature() == signature) {
 404 
 405       // get super_klass for method_holder for the found method
 406       InstanceKlass* super_klass =  super_method->method_holder();
 407 
 408       if (is_default
 409           || ((super_klass->is_override(super_method, target_loader, target_classname, THREAD))
 410           || ((klass->major_version() >= VTABLE_TRANSITIVE_OVERRIDE_VERSION)
 411           && ((super_klass = find_transitive_override(super_klass,
 412                              target_method, i, target_loader,
 413                              target_classname, THREAD))
 414                              != (InstanceKlass*)NULL))))
 415         {
 416         // Package private methods always need a new entry to root their own
 417         // overriding. They may also override other methods.
 418         if (!target_method()->is_package_private()) {
 419           allocate_new = false;
 420         }
 421 
 422         if (checkconstraints) {
 423         // Override vtable entry if passes loader constraint check
 424         // if loader constraint checking requested
 425         // No need to visit his super, since he and his super
 426         // have already made any needed loader constraints.
 427         // Since loader constraints are transitive, it is enough
 428         // to link to the first super, and we get all the others.
 429           Handle super_loader(THREAD, super_klass->class_loader());
 430 
 431           if (target_loader() != super_loader()) {
 432             ResourceMark rm(THREAD);
 433             Symbol* failed_type_symbol =
 434               SystemDictionary::check_signature_loaders(signature, target_loader,
 435                                                         super_loader, true,
 436                                                         CHECK_(false));
 437             if (failed_type_symbol != NULL) {
 438               const char* msg = "loader constraint violation: when resolving "
 439                 "overridden method \"%s\" the class loader (instance"
 440                 " of %s) of the current class, %s, and its superclass loader "
 441                 "(instance of %s), have different Class objects for the type "
 442                 "%s used in the signature";
 443               char* sig = target_method()->name_and_sig_as_C_string();
 444               const char* loader1 = SystemDictionary::loader_name(target_loader());
 445               char* current = target_klass->name()->as_C_string();
 446               const char* loader2 = SystemDictionary::loader_name(super_loader());
 447               char* failed_type_name = failed_type_symbol->as_C_string();
 448               size_t buflen = strlen(msg) + strlen(sig) + strlen(loader1) +
 449                 strlen(current) + strlen(loader2) + strlen(failed_type_name);
 450               char* buf = NEW_RESOURCE_ARRAY_IN_THREAD(THREAD, char, buflen);
 451               jio_snprintf(buf, buflen, msg, sig, loader1, current, loader2,
 452                            failed_type_name);
 453               THROW_MSG_(vmSymbols::java_lang_LinkageError(), buf, false);
 454             }
 455           }
 456        }
 457 
 458        put_method_at(target_method(), i);
 459        if (!is_default) {
 460          target_method()->set_vtable_index(i);
 461        } else {
 462          if (def_vtable_indices != NULL) {
 463            def_vtable_indices->at_put(default_index, i);
 464          }
 465          assert(super_method->is_default_method() || super_method->is_overpass()
 466                 || super_method->is_abstract(), "default override error");
 467        }
 468 
 469 
 470 #ifndef PRODUCT
 471         if (PrintVtables && Verbose) {
 472           ResourceMark rm(THREAD);
 473           char* sig = target_method()->name_and_sig_as_C_string();
 474           tty->print("overriding with %s::%s index %d, original flags: ",
 475            target_klass->internal_name(), sig, i);
 476            super_method->access_flags().print_on(tty);
 477            if (super_method->is_default_method()) {
 478              tty->print("default ");
 479            }
 480            if (super_method->is_overpass()) {
 481              tty->print("overpass");
 482            }
 483            tty->print("overriders flags: ");
 484            target_method->access_flags().print_on(tty);
 485            if (target_method->is_default_method()) {
 486              tty->print("default ");
 487            }
 488            if (target_method->is_overpass()) {
 489              tty->print("overpass");
 490            }
 491            tty->cr();
 492         }
 493 #endif /*PRODUCT*/
 494       } else {
 495         // allocate_new = true; default. We might override one entry,
 496         // but not override another. Once we override one, not need new
 497 #ifndef PRODUCT
 498         if (PrintVtables && Verbose) {
 499           ResourceMark rm(THREAD);
 500           char* sig = target_method()->name_and_sig_as_C_string();
 501           tty->print("NOT overriding with %s::%s index %d, original flags: ",
 502            target_klass->internal_name(), sig,i);
 503            super_method->access_flags().print_on(tty);
 504            if (super_method->is_default_method()) {
 505              tty->print("default ");
 506            }
 507            if (super_method->is_overpass()) {
 508              tty->print("overpass");
 509            }
 510            tty->print("overriders flags: ");
 511            target_method->access_flags().print_on(tty);
 512            if (target_method->is_default_method()) {
 513              tty->print("default ");
 514            }
 515            if (target_method->is_overpass()) {
 516              tty->print("overpass");
 517            }
 518            tty->cr();
 519         }
 520 #endif /*PRODUCT*/
 521       }
 522     }
 523   }
 524   return allocate_new;
 525 }
 526 
 527 void klassVtable::put_method_at(Method* m, int index) {
 528 #ifndef PRODUCT
 529   if (PrintVtables && Verbose) {
 530     ResourceMark rm;
 531     const char* sig = (m != NULL) ? m->name_and_sig_as_C_string() : "<NULL>";
 532     tty->print("adding %s at index %d, flags: ", sig, index);
 533     if (m != NULL) {
 534       m->access_flags().print_on(tty);
 535       if (m->is_default_method()) {
 536         tty->print("default ");
 537       }
 538       if (m->is_overpass()) {
 539         tty->print("overpass");
 540       }
 541     }
 542     tty->cr();
 543   }
 544 #endif
 545   table()[index].set(m);
 546 }
 547 
 548 // Find out if a method "m" with superclass "super", loader "classloader" and
 549 // name "classname" needs a new vtable entry.  Let P be a class package defined
 550 // by "classloader" and "classname".
 551 // NOTE: The logic used here is very similar to the one used for computing
 552 // the vtables indices for a method. We cannot directly use that function because,
 553 // we allocate the InstanceKlass at load time, and that requires that the
 554 // superclass has been loaded.
 555 // However, the vtable entries are filled in at link time, and therefore
 556 // the superclass' vtable may not yet have been filled in.
 557 bool klassVtable::needs_new_vtable_entry(methodHandle target_method,
 558                                          Klass* super,
 559                                          Handle classloader,
 560                                          Symbol* classname,
 561                                          AccessFlags class_flags,
 562                                          TRAPS) {
 563   if (class_flags.is_interface()) {
 564     // Interfaces do not use vtables, except for java.lang.Object methods,
 565     // so there is no point to assigning
 566     // a vtable index to any of their local methods.  If we refrain from doing this,
 567     // we can use Method::_vtable_index to hold the itable index
 568     return false;
 569   }
 570 
 571   if (target_method->is_final_method(class_flags) ||
 572       // a final method never needs a new entry; final methods can be statically
 573       // resolved and they have to be present in the vtable only if they override
 574       // a super's method, in which case they re-use its entry
 575       (target_method()->is_static()) ||
 576       // static methods don't need to be in vtable
 577       (target_method()->name() ==  vmSymbols::object_initializer_name())
 578       // <init> is never called dynamically-bound
 579       ) {
 580     return false;
 581   }
 582 
 583   // Concrete interface methods do not need new entries, they override
 584   // abstract method entries using default inheritance rules
 585   if (target_method()->method_holder() != NULL &&
 586       target_method()->method_holder()->is_interface()  &&
 587       !target_method()->is_abstract() ) {
 588     return false;
 589   }
 590 
 591   // we need a new entry if there is no superclass
 592   if (super == NULL) {
 593     return true;
 594   }
 595 
 596   // private methods in classes always have a new entry in the vtable
 597   // specification interpretation since classic has
 598   // private methods not overriding
 599   // JDK8 adds private  methods in interfaces which require invokespecial
 600   if (target_method()->is_private()) {
 601     return true;
 602   }
 603 
 604   // Package private methods always need a new entry to root their own
 605   // overriding. This allows transitive overriding to work.
 606   if (target_method()->is_package_private()) {
 607     return true;
 608   }
 609 
 610   // search through the super class hierarchy to see if we need
 611   // a new entry
 612   ResourceMark rm;
 613   Symbol* name = target_method()->name();
 614   Symbol* signature = target_method()->signature();
 615   Klass* k = super;
 616   Method* super_method = NULL;
 617   InstanceKlass *holder = NULL;
 618   Method* recheck_method =  NULL;
 619   while (k != NULL) {
 620     // lookup through the hierarchy for a method with matching name and sign.
 621     super_method = InstanceKlass::cast(k)->lookup_method(name, signature);
 622     if (super_method == NULL) {
 623       break; // we still have to search for a matching miranda method
 624     }
 625     // get the class holding the matching method
 626     // make sure you use that class for is_override
 627     InstanceKlass* superk = super_method->method_holder();
 628     // we want only instance method matches
 629     // pretend private methods are not in the super vtable
 630     // since we do override around them: e.g. a.m pub/b.m private/c.m pub,
 631     // ignore private, c.m pub does override a.m pub
 632     // For classes that were not javac'd together, we also do transitive overriding around
 633     // methods that have less accessibility
 634     if ((!super_method->is_static()) &&
 635        (!super_method->is_private())) {
 636       if (superk->is_override(super_method, classloader, classname, THREAD)) {
 637         return false;
 638       // else keep looking for transitive overrides
 639       }
 640     }
 641 
 642     // Start with lookup result and continue to search up
 643     k = superk->super(); // haven't found an override match yet; continue to look
 644   }
 645 
 646   // if the target method is public or protected it may have a matching
 647   // miranda method in the super, whose entry it should re-use.
 648   // Actually, to handle cases that javac would not generate, we need
 649   // this check for all access permissions.
 650   InstanceKlass *sk = InstanceKlass::cast(super);
 651   if (sk->has_miranda_methods()) {
 652     if (sk->lookup_method_in_all_interfaces(name, signature, Klass::find_defaults) != NULL) {
 653       return false;  // found a matching miranda; we do not need a new entry
 654     }
 655   }
 656   return true; // found no match; we need a new entry
 657 }
 658 
 659 // Support for miranda methods
 660 
 661 // get the vtable index of a miranda method with matching "name" and "signature"
 662 int klassVtable::index_of_miranda(Symbol* name, Symbol* signature) {
 663   // search from the bottom, might be faster
 664   for (int i = (length() - 1); i >= 0; i--) {
 665     Method* m = table()[i].method();
 666     if (is_miranda_entry_at(i) &&
 667         m->name() == name && m->signature() == signature) {
 668       return i;
 669     }
 670   }
 671   return Method::invalid_vtable_index;
 672 }
 673 
 674 // check if an entry at an index is miranda
 675 // requires that method m at entry be declared ("held") by an interface.
 676 bool klassVtable::is_miranda_entry_at(int i) {
 677   Method* m = method_at(i);
 678   Klass* method_holder = m->method_holder();
 679   InstanceKlass *mhk = InstanceKlass::cast(method_holder);
 680 
 681   // miranda methods are public abstract instance interface methods in a class's vtable
 682   if (mhk->is_interface()) {
 683     assert(m->is_public(), "should be public");
 684     assert(ik()->implements_interface(method_holder) , "this class should implement the interface");
 685     // the search could find a miranda or a default method
 686     if (is_miranda(m, ik()->methods(), ik()->default_methods(), ik()->super())) {
 687       return true;
 688     }
 689   }
 690   return false;
 691 }
 692 
 693 // check if a method is a miranda method, given a class's methods table,
 694 // its default_method table  and its super
 695 // Miranda methods are calculated twice:
 696 // first: before vtable size calculation: including abstract and default
 697 // This is seen by default method creation
 698 // Second: recalculated during vtable initialization: only abstract
 699 // This is seen by link resolution and selection.
 700 // "miranda" means not static, not defined by this class.
 701 // private methods in interfaces do not belong in the miranda list.
 702 // the caller must make sure that the method belongs to an interface implemented by the class
 703 // Miranda methods only include public interface instance methods
 704 // Not private methods, not static methods, not default == concrete abstract
 705 // Miranda methods also do not include overpass methods in interfaces
 706 bool klassVtable::is_miranda(Method* m, Array<Method*>* class_methods,
 707                              Array<Method*>* default_methods, Klass* super) {
 708   if (m->is_static() || m->is_private() || m->is_overpass()) {
 709     return false;
 710   }
 711   Symbol* name = m->name();
 712   Symbol* signature = m->signature();
 713 
 714   if (InstanceKlass::find_instance_method(class_methods, name, signature) == NULL) {
 715     // did not find it in the method table of the current class
 716     if ((default_methods == NULL) ||
 717         InstanceKlass::find_method(default_methods, name, signature) == NULL) {
 718       if (super == NULL) {
 719         // super doesn't exist
 720         return true;
 721       }
 722 
 723       Method* mo = InstanceKlass::cast(super)->lookup_method(name, signature);
 724       while (mo != NULL && mo->access_flags().is_static()
 725              && mo->method_holder() != NULL
 726              && mo->method_holder()->super() != NULL)
 727       {
 728          mo = mo->method_holder()->super()->uncached_lookup_method(name, signature, Klass::find_overpass);
 729       }
 730       if (mo == NULL || mo->access_flags().is_private() ) {
 731         // super class hierarchy does not implement it or protection is different
 732         return true;
 733       }
 734     }
 735   }
 736 
 737   return false;
 738 }
 739 
 740 // Scans current_interface_methods for miranda methods that do not
 741 // already appear in new_mirandas, or default methods,  and are also not defined-and-non-private
 742 // in super (superclass).  These mirandas are added to all_mirandas if it is
 743 // not null; in addition, those that are not duplicates of miranda methods
 744 // inherited by super from its interfaces are added to new_mirandas.
 745 // Thus, new_mirandas will be the set of mirandas that this class introduces,
 746 // all_mirandas will be the set of all mirandas applicable to this class
 747 // including all defined in superclasses.
 748 void klassVtable::add_new_mirandas_to_lists(
 749     GrowableArray<Method*>* new_mirandas, GrowableArray<Method*>* all_mirandas,
 750     Array<Method*>* current_interface_methods, Array<Method*>* class_methods,
 751     Array<Method*>* default_methods, Klass* super) {
 752 
 753   // iterate thru the current interface's method to see if it a miranda
 754   int num_methods = current_interface_methods->length();
 755   for (int i = 0; i < num_methods; i++) {
 756     Method* im = current_interface_methods->at(i);
 757     bool is_duplicate = false;
 758     int num_of_current_mirandas = new_mirandas->length();
 759     // check for duplicate mirandas in different interfaces we implement
 760     for (int j = 0; j < num_of_current_mirandas; j++) {
 761       Method* miranda = new_mirandas->at(j);
 762       if ((im->name() == miranda->name()) &&
 763           (im->signature() == miranda->signature())) {
 764         is_duplicate = true;
 765         break;
 766       }
 767     }
 768 
 769     if (!is_duplicate) { // we don't want duplicate miranda entries in the vtable
 770       if (is_miranda(im, class_methods, default_methods, super)) { // is it a miranda at all?
 771         InstanceKlass *sk = InstanceKlass::cast(super);
 772         // check if it is a duplicate of a super's miranda
 773         if (sk->lookup_method_in_all_interfaces(im->name(), im->signature(), Klass::find_defaults) == NULL) {
 774           new_mirandas->append(im);
 775         }
 776         if (all_mirandas != NULL) {
 777           all_mirandas->append(im);
 778         }
 779       }
 780     }
 781   }
 782 }
 783 
 784 void klassVtable::get_mirandas(GrowableArray<Method*>* new_mirandas,
 785                                GrowableArray<Method*>* all_mirandas,
 786                                Klass* super, Array<Method*>* class_methods,
 787                                Array<Method*>* default_methods,
 788                                Array<Klass*>* local_interfaces) {
 789   assert((new_mirandas->length() == 0) , "current mirandas must be 0");
 790 
 791   // iterate thru the local interfaces looking for a miranda
 792   int num_local_ifs = local_interfaces->length();
 793   for (int i = 0; i < num_local_ifs; i++) {
 794     InstanceKlass *ik = InstanceKlass::cast(local_interfaces->at(i));
 795     add_new_mirandas_to_lists(new_mirandas, all_mirandas,
 796                               ik->methods(), class_methods,
 797                               default_methods, super);
 798     // iterate thru each local's super interfaces
 799     Array<Klass*>* super_ifs = ik->transitive_interfaces();
 800     int num_super_ifs = super_ifs->length();
 801     for (int j = 0; j < num_super_ifs; j++) {
 802       InstanceKlass *sik = InstanceKlass::cast(super_ifs->at(j));
 803       add_new_mirandas_to_lists(new_mirandas, all_mirandas,
 804                                 sik->methods(), class_methods,
 805                                 default_methods, super);
 806     }
 807   }
 808 }
 809 
 810 // Discover miranda methods ("miranda" = "interface abstract, no binding"),
 811 // and append them into the vtable starting at index initialized,
 812 // return the new value of initialized.
 813 // Miranda methods use vtable entries, but do not get assigned a vtable_index
 814 // The vtable_index is discovered by searching from the end of the vtable
 815 int klassVtable::fill_in_mirandas(int initialized) {
 816   GrowableArray<Method*> mirandas(20);
 817   get_mirandas(&mirandas, NULL, ik()->super(), ik()->methods(),
 818                ik()->default_methods(), ik()->local_interfaces());
 819   for (int i = 0; i < mirandas.length(); i++) {
 820     if (PrintVtables && Verbose) {
 821       Method* meth = mirandas.at(i);
 822       ResourceMark rm(Thread::current());
 823       if (meth != NULL) {
 824         char* sig = meth->name_and_sig_as_C_string();
 825         tty->print("fill in mirandas with %s index %d, flags: ",
 826           sig, initialized);
 827         meth->access_flags().print_on(tty);
 828         if (meth->is_default_method()) {
 829           tty->print("default ");
 830         }
 831         tty->cr();
 832       }
 833     }
 834     put_method_at(mirandas.at(i), initialized);
 835     ++initialized;
 836   }
 837   return initialized;
 838 }
 839 
 840 // Copy this class's vtable to the vtable beginning at start.
 841 // Used to copy superclass vtable to prefix of subclass's vtable.
 842 void klassVtable::copy_vtable_to(vtableEntry* start) {
 843   Copy::disjoint_words((HeapWord*)table(), (HeapWord*)start, _length * vtableEntry::size());
 844 }
 845 
 846 #if INCLUDE_JVMTI
 847 bool klassVtable::adjust_default_method(int vtable_index, Method* old_method, Method* new_method) {
 848   // If old_method is default, find this vtable index in default_vtable_indices
 849   // and replace that method in the _default_methods list
 850   bool updated = false;
 851 
 852   Array<Method*>* default_methods = ik()->default_methods();
 853   if (default_methods != NULL) {
 854     int len = default_methods->length();
 855     for (int idx = 0; idx < len; idx++) {
 856       if (vtable_index == ik()->default_vtable_indices()->at(idx)) {
 857         if (default_methods->at(idx) == old_method) {
 858           default_methods->at_put(idx, new_method);
 859           updated = true;
 860         }
 861         break;
 862       }
 863     }
 864   }
 865   return updated;
 866 }
 867 void klassVtable::adjust_method_entries(Method** old_methods, Method** new_methods,
 868                                         int methods_length, bool * trace_name_printed) {
 869   // search the vtable for uses of either obsolete or EMCP methods
 870   for (int j = 0; j < methods_length; j++) {
 871     Method* old_method = old_methods[j];
 872     Method* new_method = new_methods[j];
 873 
 874     // In the vast majority of cases we could get the vtable index
 875     // by using:  old_method->vtable_index()
 876     // However, there are rare cases, eg. sun.awt.X11.XDecoratedPeer.getX()
 877     // in sun.awt.X11.XFramePeer where methods occur more than once in the
 878     // vtable, so, alas, we must do an exhaustive search.
 879     for (int index = 0; index < length(); index++) {
 880       if (unchecked_method_at(index) == old_method) {
 881         put_method_at(new_method, index);
 882           // For default methods, need to update the _default_methods array
 883           // which can only have one method entry for a given signature
 884           bool updated_default = false;
 885           if (old_method->is_default_method()) {
 886             updated_default = adjust_default_method(index, old_method, new_method);
 887           }
 888 
 889         if (RC_TRACE_IN_RANGE(0x00100000, 0x00400000)) {
 890           if (!(*trace_name_printed)) {
 891             // RC_TRACE_MESG macro has an embedded ResourceMark
 892             RC_TRACE_MESG(("adjust: klassname=%s for methods from name=%s",
 893                            klass()->external_name(),
 894                            old_method->method_holder()->external_name()));
 895             *trace_name_printed = true;
 896           }
 897           // RC_TRACE macro has an embedded ResourceMark
 898           RC_TRACE(0x00100000, ("vtable method update: %s(%s), updated default = %s",
 899                                 new_method->name()->as_C_string(),
 900                                 new_method->signature()->as_C_string(),
 901                                 updated_default ? "true" : "false"));
 902         }
 903         // cannot 'break' here; see for-loop comment above.
 904       }
 905     }
 906   }
 907 }
 908 
 909 // a vtable should never contain old or obsolete methods
 910 bool klassVtable::check_no_old_or_obsolete_entries() {
 911   for (int i = 0; i < length(); i++) {
 912     Method* m = unchecked_method_at(i);
 913     if (m != NULL &&
 914         (NOT_PRODUCT(!m->is_valid() ||) m->is_old() || m->is_obsolete())) {
 915       return false;
 916     }
 917   }
 918   return true;
 919 }
 920 
 921 void klassVtable::dump_vtable() {
 922   tty->print_cr("vtable dump --");
 923   for (int i = 0; i < length(); i++) {
 924     Method* m = unchecked_method_at(i);
 925     if (m != NULL) {
 926       tty->print("      (%5d)  ", i);
 927       m->access_flags().print_on(tty);
 928       if (m->is_default_method()) {
 929         tty->print("default ");
 930       }
 931       if (m->is_overpass()) {
 932         tty->print("overpass");
 933       }
 934       tty->print(" --  ");
 935       m->print_name(tty);
 936       tty->cr();
 937     }
 938   }
 939 }
 940 #endif // INCLUDE_JVMTI
 941 
 942 // CDS/RedefineClasses support - clear vtables so they can be reinitialized
 943 void klassVtable::clear_vtable() {
 944   for (int i = 0; i < _length; i++) table()[i].clear();
 945 }
 946 
 947 bool klassVtable::is_initialized() {
 948   return _length == 0 || table()[0].method() != NULL;
 949 }
 950 
 951 //-----------------------------------------------------------------------------------------
 952 // Itable code
 953 
 954 // Initialize a itableMethodEntry
 955 void itableMethodEntry::initialize(Method* m) {
 956   if (m == NULL) return;
 957 
 958   _method = m;
 959 }
 960 
 961 klassItable::klassItable(instanceKlassHandle klass) {
 962   _klass = klass;
 963 
 964   if (klass->itable_length() > 0) {
 965     itableOffsetEntry* offset_entry = (itableOffsetEntry*)klass->start_of_itable();
 966     if (offset_entry  != NULL && offset_entry->interface_klass() != NULL) { // Check that itable is initialized
 967       // First offset entry points to the first method_entry
 968       intptr_t* method_entry  = (intptr_t *)(((address)klass()) + offset_entry->offset());
 969       intptr_t* end         = klass->end_of_itable();
 970 
 971       _table_offset      = (intptr_t*)offset_entry - (intptr_t*)klass();
 972       _size_offset_table = (method_entry - ((intptr_t*)offset_entry)) / itableOffsetEntry::size();
 973       _size_method_table = (end - method_entry)                  / itableMethodEntry::size();
 974       assert(_table_offset >= 0 && _size_offset_table >= 0 && _size_method_table >= 0, "wrong computation");
 975       return;
 976     }
 977   }
 978 
 979   // The length of the itable was either zero, or it has not yet been initialized.
 980   _table_offset      = 0;
 981   _size_offset_table = 0;
 982   _size_method_table = 0;
 983 }
 984 
 985 static int initialize_count = 0;
 986 
 987 // Initialization
 988 void klassItable::initialize_itable(bool checkconstraints, TRAPS) {
 989   if (_klass->is_interface()) {
 990     // This needs to go after vtable indices are assigned but
 991     // before implementors need to know the number of itable indices.
 992     assign_itable_indices_for_interface(_klass());
 993   }
 994 
 995   // Cannot be setup doing bootstrapping, interfaces don't have
 996   // itables, and klass with only ones entry have empty itables
 997   if (Universe::is_bootstrapping() ||
 998       _klass->is_interface() ||
 999       _klass->itable_length() == itableOffsetEntry::size()) return;
1000 
1001   // There's alway an extra itable entry so we can null-terminate it.
1002   guarantee(size_offset_table() >= 1, "too small");
1003   int num_interfaces = size_offset_table() - 1;
1004   if (num_interfaces > 0) {
1005     if (TraceItables) tty->print_cr("%3d: Initializing itables for %s", ++initialize_count,
1006                                     _klass->name()->as_C_string());
1007 
1008 
1009     // Iterate through all interfaces
1010     int i;
1011     for(i = 0; i < num_interfaces; i++) {
1012       itableOffsetEntry* ioe = offset_entry(i);
1013       HandleMark hm(THREAD);
1014       KlassHandle interf_h (THREAD, ioe->interface_klass());
1015       assert(interf_h() != NULL && ioe->offset() != 0, "bad offset entry in itable");
1016       initialize_itable_for_interface(ioe->offset(), interf_h, checkconstraints, CHECK);
1017     }
1018 
1019   }
1020   // Check that the last entry is empty
1021   itableOffsetEntry* ioe = offset_entry(size_offset_table() - 1);
1022   guarantee(ioe->interface_klass() == NULL && ioe->offset() == 0, "terminator entry missing");
1023 }
1024 
1025 
1026 inline bool interface_method_needs_itable_index(Method* m) {
1027   if (m->is_static())           return false;   // e.g., Stream.empty
1028   if (m->is_initializer())      return false;   // <init> or <clinit>
1029   // If an interface redeclares a method from java.lang.Object,
1030   // it should already have a vtable index, don't touch it.
1031   // e.g., CharSequence.toString (from initialize_vtable)
1032   // if (m->has_vtable_index())  return false; // NO!
1033   return true;
1034 }
1035 
1036 int klassItable::assign_itable_indices_for_interface(Klass* klass) {
1037   // an interface does not have an itable, but its methods need to be numbered
1038   if (TraceItables) tty->print_cr("%3d: Initializing itable for interface %s", ++initialize_count,
1039                                   klass->name()->as_C_string());
1040   Array<Method*>* methods = InstanceKlass::cast(klass)->methods();
1041   int nof_methods = methods->length();
1042   int ime_num = 0;
1043   for (int i = 0; i < nof_methods; i++) {
1044     Method* m = methods->at(i);
1045     if (interface_method_needs_itable_index(m)) {
1046       assert(!m->is_final_method(), "no final interface methods");
1047       // If m is already assigned a vtable index, do not disturb it.
1048       if (TraceItables && Verbose) {
1049         ResourceMark rm;
1050         const char* sig = (m != NULL) ? m->name_and_sig_as_C_string() : "<NULL>";
1051         if (m->has_vtable_index()) {
1052           tty->print("itable index %d for method: %s, flags: ", m->vtable_index(), sig);
1053         } else {
1054           tty->print("itable index %d for method: %s, flags: ", ime_num, sig);
1055         }
1056         if (m != NULL) {
1057           m->access_flags().print_on(tty);
1058           if (m->is_default_method()) {
1059             tty->print("default ");
1060           }
1061           if (m->is_overpass()) {
1062             tty->print("overpass");
1063           }
1064         }
1065         tty->cr();
1066       }
1067       if (!m->has_vtable_index()) {
1068         assert(m->vtable_index() == Method::pending_itable_index, "set by initialize_vtable");
1069         m->set_itable_index(ime_num);
1070         // Progress to next itable entry
1071         ime_num++;
1072       }
1073     }
1074   }
1075   assert(ime_num == method_count_for_interface(klass), "proper sizing");
1076   return ime_num;
1077 }
1078 
1079 int klassItable::method_count_for_interface(Klass* interf) {
1080   assert(interf->oop_is_instance(), "must be");
1081   assert(interf->is_interface(), "must be");
1082   Array<Method*>* methods = InstanceKlass::cast(interf)->methods();
1083   int nof_methods = methods->length();
1084   while (nof_methods > 0) {
1085     Method* m = methods->at(nof_methods-1);
1086     if (m->has_itable_index()) {
1087       int length = m->itable_index() + 1;
1088 #ifdef ASSERT
1089       while (nof_methods = 0) {
1090         m = methods->at(--nof_methods);
1091         assert(!m->has_itable_index() || m->itable_index() < length, "");
1092       }
1093 #endif //ASSERT
1094       return length;  // return the rightmost itable index, plus one
1095     }
1096     nof_methods -= 1;
1097   }
1098   // no methods have itable indices
1099   return 0;
1100 }
1101 
1102 
1103 void klassItable::initialize_itable_for_interface(int method_table_offset, KlassHandle interf_h, bool checkconstraints, TRAPS) {
1104   Array<Method*>* methods = InstanceKlass::cast(interf_h())->methods();
1105   int nof_methods = methods->length();
1106   HandleMark hm;
1107   assert(nof_methods > 0, "at least one method must exist for interface to be in vtable");
1108   Handle interface_loader (THREAD, InstanceKlass::cast(interf_h())->class_loader());
1109 
1110   int ime_count = method_count_for_interface(interf_h());
1111   for (int i = 0; i < nof_methods; i++) {
1112     Method* m = methods->at(i);
1113     methodHandle target;
1114     if (m->has_itable_index()) {
1115       // This search must match the runtime resolution, i.e. selection search for invokeinterface
1116       // to correctly enforce loader constraints for interface method inheritance
1117       LinkResolver::lookup_instance_method_in_klasses(target, _klass, m->name(), m->signature(), CHECK);
1118     }
1119     if (target == NULL || !target->is_public() || target->is_abstract()) {
1120       // Entry does not resolve. Leave it empty for AbstractMethodError.
1121         if (!(target == NULL) && !target->is_public()) {
1122           // Stuff an IllegalAccessError throwing method in there instead.
1123           itableOffsetEntry::method_entry(_klass(), method_table_offset)[m->itable_index()].
1124               initialize(Universe::throw_illegal_access_error());
1125         }
1126     } else {
1127       // Entry did resolve, check loader constraints before initializing
1128       // if checkconstraints requested
1129       if (checkconstraints) {
1130         Handle method_holder_loader (THREAD, target->method_holder()->class_loader());
1131         if (method_holder_loader() != interface_loader()) {
1132           ResourceMark rm(THREAD);
1133           Symbol* failed_type_symbol =
1134             SystemDictionary::check_signature_loaders(m->signature(),
1135                                                       method_holder_loader,
1136                                                       interface_loader,
1137                                                       true, CHECK);
1138           if (failed_type_symbol != NULL) {
1139             const char* msg = "loader constraint violation in interface "
1140               "itable initialization: when resolving method \"%s\" the class"
1141               " loader (instance of %s) of the current class, %s, "
1142               "and the class loader (instance of %s) for interface "
1143               "%s have different Class objects for the type %s "
1144               "used in the signature";
1145             char* sig = target()->name_and_sig_as_C_string();
1146             const char* loader1 = SystemDictionary::loader_name(method_holder_loader());
1147             char* current = _klass->name()->as_C_string();
1148             const char* loader2 = SystemDictionary::loader_name(interface_loader());
1149             char* iface = InstanceKlass::cast(interf_h())->name()->as_C_string();
1150             char* failed_type_name = failed_type_symbol->as_C_string();
1151             size_t buflen = strlen(msg) + strlen(sig) + strlen(loader1) +
1152               strlen(current) + strlen(loader2) + strlen(iface) +
1153               strlen(failed_type_name);
1154             char* buf = NEW_RESOURCE_ARRAY_IN_THREAD(THREAD, char, buflen);
1155             jio_snprintf(buf, buflen, msg, sig, loader1, current, loader2,
1156                          iface, failed_type_name);
1157             THROW_MSG(vmSymbols::java_lang_LinkageError(), buf);
1158           }
1159         }
1160       }
1161 
1162       // ime may have moved during GC so recalculate address
1163       int ime_num = m->itable_index();
1164       assert(ime_num < ime_count, "oob");
1165       itableOffsetEntry::method_entry(_klass(), method_table_offset)[ime_num].initialize(target());
1166       if (TraceItables && Verbose) {
1167         ResourceMark rm(THREAD);
1168         if (target() != NULL) {
1169           char* sig = target()->name_and_sig_as_C_string();
1170           tty->print("interface: %s, ime_num: %d, target: %s, method_holder: %s ",
1171                     interf_h()->internal_name(), ime_num, sig,
1172                     target()->method_holder()->internal_name());
1173           tty->print("target_method flags: ");
1174           target()->access_flags().print_on(tty);
1175           if (target()->is_default_method()) {
1176             tty->print("default ");
1177           }
1178           tty->cr();
1179         }
1180       }
1181     }
1182   }
1183 }
1184 
1185 // Update entry for specific Method*
1186 void klassItable::initialize_with_method(Method* m) {
1187   itableMethodEntry* ime = method_entry(0);
1188   for(int i = 0; i < _size_method_table; i++) {
1189     if (ime->method() == m) {
1190       ime->initialize(m);
1191     }
1192     ime++;
1193   }
1194 }
1195 
1196 #if INCLUDE_JVMTI
1197 void klassItable::adjust_method_entries(Method** old_methods, Method** new_methods,
1198                                         int methods_length, bool * trace_name_printed) {
1199   // search the itable for uses of either obsolete or EMCP methods
1200   for (int j = 0; j < methods_length; j++) {
1201     Method* old_method = old_methods[j];
1202     Method* new_method = new_methods[j];
1203     itableMethodEntry* ime = method_entry(0);
1204 
1205     // The itable can describe more than one interface and the same
1206     // method signature can be specified by more than one interface.
1207     // This means we have to do an exhaustive search to find all the
1208     // old_method references.
1209     for (int i = 0; i < _size_method_table; i++) {
1210       if (ime->method() == old_method) {
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         // cannot 'break' here; see for-loop comment above.
1226       }
1227       ime++;
1228     }
1229   }
1230 }
1231 
1232 // an itable should never contain old or obsolete methods
1233 bool klassItable::check_no_old_or_obsolete_entries() {
1234   itableMethodEntry* ime = method_entry(0);
1235   for (int i = 0; i < _size_method_table; i++) {
1236     Method* m = ime->method();
1237     if (m != NULL &&
1238         (NOT_PRODUCT(!m->is_valid() ||) m->is_old() || m->is_obsolete())) {
1239       return false;
1240     }
1241     ime++;
1242   }
1243   return true;
1244 }
1245 
1246 void klassItable::dump_itable() {
1247   itableMethodEntry* ime = method_entry(0);
1248   tty->print_cr("itable dump --");
1249   for (int i = 0; i < _size_method_table; i++) {
1250     Method* m = ime->method();
1251     if (m != NULL) {
1252       tty->print("      (%5d)  ", i);
1253       m->access_flags().print_on(tty);
1254       if (m->is_default_method()) {
1255         tty->print("default ");
1256       }
1257       tty->print(" --  ");
1258       m->print_name(tty);
1259       tty->cr();
1260     }
1261     ime++;
1262   }
1263 }
1264 #endif // INCLUDE_JVMTI
1265 
1266 
1267 // Setup
1268 class InterfaceVisiterClosure : public StackObj {
1269  public:
1270   virtual void doit(Klass* intf, int method_count) = 0;
1271 };
1272 
1273 // Visit all interfaces with at least one itable method
1274 void visit_all_interfaces(Array<Klass*>* transitive_intf, InterfaceVisiterClosure *blk) {
1275   // Handle array argument
1276   for(int i = 0; i < transitive_intf->length(); i++) {
1277     Klass* intf = transitive_intf->at(i);
1278     assert(intf->is_interface(), "sanity check");
1279 
1280     // Find no. of itable methods
1281     int method_count = 0;
1282     // method_count = klassItable::method_count_for_interface(intf);
1283     Array<Method*>* methods = InstanceKlass::cast(intf)->methods();
1284     if (methods->length() > 0) {
1285       for (int i = methods->length(); --i >= 0; ) {
1286         if (interface_method_needs_itable_index(methods->at(i))) {
1287           method_count++;
1288         }
1289       }
1290     }
1291 
1292     // Only count interfaces with at least one method
1293     if (method_count > 0) {
1294       blk->doit(intf, method_count);
1295     }
1296   }
1297 }
1298 
1299 class CountInterfacesClosure : public InterfaceVisiterClosure {
1300  private:
1301   int _nof_methods;
1302   int _nof_interfaces;
1303  public:
1304    CountInterfacesClosure() { _nof_methods = 0; _nof_interfaces = 0; }
1305 
1306    int nof_methods() const    { return _nof_methods; }
1307    int nof_interfaces() const { return _nof_interfaces; }
1308 
1309    void doit(Klass* intf, int method_count) { _nof_methods += method_count; _nof_interfaces++; }
1310 };
1311 
1312 class SetupItableClosure : public InterfaceVisiterClosure  {
1313  private:
1314   itableOffsetEntry* _offset_entry;
1315   itableMethodEntry* _method_entry;
1316   address            _klass_begin;
1317  public:
1318   SetupItableClosure(address klass_begin, itableOffsetEntry* offset_entry, itableMethodEntry* method_entry) {
1319     _klass_begin  = klass_begin;
1320     _offset_entry = offset_entry;
1321     _method_entry = method_entry;
1322   }
1323 
1324   itableMethodEntry* method_entry() const { return _method_entry; }
1325 
1326   void doit(Klass* intf, int method_count) {
1327     int offset = ((address)_method_entry) - _klass_begin;
1328     _offset_entry->initialize(intf, offset);
1329     _offset_entry++;
1330     _method_entry += method_count;
1331   }
1332 };
1333 
1334 int klassItable::compute_itable_size(Array<Klass*>* transitive_interfaces) {
1335   // Count no of interfaces and total number of interface methods
1336   CountInterfacesClosure cic;
1337   visit_all_interfaces(transitive_interfaces, &cic);
1338 
1339   // There's alway an extra itable entry so we can null-terminate it.
1340   int itable_size = calc_itable_size(cic.nof_interfaces() + 1, cic.nof_methods());
1341 
1342   // Statistics
1343   update_stats(itable_size * HeapWordSize);
1344 
1345   return itable_size;
1346 }
1347 
1348 
1349 // Fill out offset table and interface klasses into the itable space
1350 void klassItable::setup_itable_offset_table(instanceKlassHandle klass) {
1351   if (klass->itable_length() == 0) return;
1352   assert(!klass->is_interface(), "Should have zero length itable");
1353 
1354   // Count no of interfaces and total number of interface methods
1355   CountInterfacesClosure cic;
1356   visit_all_interfaces(klass->transitive_interfaces(), &cic);
1357   int nof_methods    = cic.nof_methods();
1358   int nof_interfaces = cic.nof_interfaces();
1359 
1360   // Add one extra entry so we can null-terminate the table
1361   nof_interfaces++;
1362 
1363   assert(compute_itable_size(klass->transitive_interfaces()) ==
1364          calc_itable_size(nof_interfaces, nof_methods),
1365          "mismatch calculation of itable size");
1366 
1367   // Fill-out offset table
1368   itableOffsetEntry* ioe = (itableOffsetEntry*)klass->start_of_itable();
1369   itableMethodEntry* ime = (itableMethodEntry*)(ioe + nof_interfaces);
1370   intptr_t* end               = klass->end_of_itable();
1371   assert((oop*)(ime + nof_methods) <= (oop*)klass->start_of_nonstatic_oop_maps(), "wrong offset calculation (1)");
1372   assert((oop*)(end) == (oop*)(ime + nof_methods),                      "wrong offset calculation (2)");
1373 
1374   // Visit all interfaces and initialize itable offset table
1375   SetupItableClosure sic((address)klass(), ioe, ime);
1376   visit_all_interfaces(klass->transitive_interfaces(), &sic);
1377 
1378 #ifdef ASSERT
1379   ime  = sic.method_entry();
1380   oop* v = (oop*) klass->end_of_itable();
1381   assert( (oop*)(ime) == v, "wrong offset calculation (2)");
1382 #endif
1383 }
1384 
1385 
1386 // inverse to itable_index
1387 Method* klassItable::method_for_itable_index(Klass* intf, int itable_index) {
1388   assert(InstanceKlass::cast(intf)->is_interface(), "sanity check");
1389   assert(intf->verify_itable_index(itable_index), "");
1390   Array<Method*>* methods = InstanceKlass::cast(intf)->methods();
1391 
1392   if (itable_index < 0 || itable_index >= method_count_for_interface(intf))
1393     return NULL;                // help caller defend against bad indices
1394 
1395   int index = itable_index;
1396   Method* m = methods->at(index);
1397   int index2 = -1;
1398   while (!m->has_itable_index() ||
1399          (index2 = m->itable_index()) != itable_index) {
1400     assert(index2 < itable_index, "monotonic");
1401     if (++index == methods->length())
1402       return NULL;
1403     m = methods->at(index);
1404   }
1405   assert(m->itable_index() == itable_index, "correct inverse");
1406 
1407   return m;
1408 }
1409 
1410 void klassVtable::verify(outputStream* st, bool forced) {
1411   // make sure table is initialized
1412   if (!Universe::is_fully_initialized()) return;
1413 #ifndef PRODUCT
1414   // avoid redundant verifies
1415   if (!forced && _verify_count == Universe::verify_count()) return;
1416   _verify_count = Universe::verify_count();
1417 #endif
1418   oop* end_of_obj = (oop*)_klass() + _klass()->size();
1419   oop* end_of_vtable = (oop *)&table()[_length];
1420   if (end_of_vtable > end_of_obj) {
1421     fatal(err_msg("klass %s: klass object too short (vtable extends beyond "
1422                   "end)", _klass->internal_name()));
1423   }
1424 
1425   for (int i = 0; i < _length; i++) table()[i].verify(this, st);
1426   // verify consistency with superKlass vtable
1427   Klass* super = _klass->super();
1428   if (super != NULL) {
1429     InstanceKlass* sk = InstanceKlass::cast(super);
1430     klassVtable* vt = sk->vtable();
1431     for (int i = 0; i < vt->length(); i++) {
1432       verify_against(st, vt, i);
1433     }
1434   }
1435 }
1436 
1437 void klassVtable::verify_against(outputStream* st, klassVtable* vt, int index) {
1438   vtableEntry* vte = &vt->table()[index];
1439   if (vte->method()->name()      != table()[index].method()->name() ||
1440       vte->method()->signature() != table()[index].method()->signature()) {
1441     fatal("mismatched name/signature of vtable entries");
1442   }
1443 }
1444 
1445 #ifndef PRODUCT
1446 void klassVtable::print() {
1447   ResourceMark rm;
1448   tty->print("klassVtable for klass %s (length %d):\n", _klass->internal_name(), length());
1449   for (int i = 0; i < length(); i++) {
1450     table()[i].print();
1451     tty->cr();
1452   }
1453 }
1454 #endif
1455 
1456 void vtableEntry::verify(klassVtable* vt, outputStream* st) {
1457   NOT_PRODUCT(FlagSetting fs(IgnoreLockingAssertions, true));
1458   assert(method() != NULL, "must have set method");
1459   method()->verify();
1460   // we sub_type, because it could be a miranda method
1461   if (!vt->klass()->is_subtype_of(method()->method_holder())) {
1462 #ifndef PRODUCT
1463     print();
1464 #endif
1465     fatal(err_msg("vtableEntry " PTR_FORMAT ": method is from subclass", this));
1466   }
1467 }
1468 
1469 #ifndef PRODUCT
1470 
1471 void vtableEntry::print() {
1472   ResourceMark rm;
1473   tty->print("vtableEntry %s: ", method()->name()->as_C_string());
1474   if (Verbose) {
1475     tty->print("m %#lx ", (address)method());
1476   }
1477 }
1478 
1479 class VtableStats : AllStatic {
1480  public:
1481   static int no_klasses;                // # classes with vtables
1482   static int no_array_klasses;          // # array classes
1483   static int no_instance_klasses;       // # instanceKlasses
1484   static int sum_of_vtable_len;         // total # of vtable entries
1485   static int sum_of_array_vtable_len;   // total # of vtable entries in array klasses only
1486   static int fixed;                     // total fixed overhead in bytes
1487   static int filler;                    // overhead caused by filler bytes
1488   static int entries;                   // total bytes consumed by vtable entries
1489   static int array_entries;             // total bytes consumed by array vtable entries
1490 
1491   static void do_class(Klass* k) {
1492     Klass* kl = k;
1493     klassVtable* vt = kl->vtable();
1494     if (vt == NULL) return;
1495     no_klasses++;
1496     if (kl->oop_is_instance()) {
1497       no_instance_klasses++;
1498       kl->array_klasses_do(do_class);
1499     }
1500     if (kl->oop_is_array()) {
1501       no_array_klasses++;
1502       sum_of_array_vtable_len += vt->length();
1503     }
1504     sum_of_vtable_len += vt->length();
1505   }
1506 
1507   static void compute() {
1508     SystemDictionary::classes_do(do_class);
1509     fixed  = no_klasses * oopSize;      // vtable length
1510     // filler size is a conservative approximation
1511     filler = oopSize * (no_klasses - no_instance_klasses) * (sizeof(InstanceKlass) - sizeof(ArrayKlass) - 1);
1512     entries = sizeof(vtableEntry) * sum_of_vtable_len;
1513     array_entries = sizeof(vtableEntry) * sum_of_array_vtable_len;
1514   }
1515 };
1516 
1517 int VtableStats::no_klasses = 0;
1518 int VtableStats::no_array_klasses = 0;
1519 int VtableStats::no_instance_klasses = 0;
1520 int VtableStats::sum_of_vtable_len = 0;
1521 int VtableStats::sum_of_array_vtable_len = 0;
1522 int VtableStats::fixed = 0;
1523 int VtableStats::filler = 0;
1524 int VtableStats::entries = 0;
1525 int VtableStats::array_entries = 0;
1526 
1527 void klassVtable::print_statistics() {
1528   ResourceMark rm;
1529   HandleMark hm;
1530   VtableStats::compute();
1531   tty->print_cr("vtable statistics:");
1532   tty->print_cr("%6d classes (%d instance, %d array)", VtableStats::no_klasses, VtableStats::no_instance_klasses, VtableStats::no_array_klasses);
1533   int total = VtableStats::fixed + VtableStats::filler + VtableStats::entries;
1534   tty->print_cr("%6d bytes fixed overhead (refs + vtable object header)", VtableStats::fixed);
1535   tty->print_cr("%6d bytes filler overhead", VtableStats::filler);
1536   tty->print_cr("%6d bytes for vtable entries (%d for arrays)", VtableStats::entries, VtableStats::array_entries);
1537   tty->print_cr("%6d bytes total", total);
1538 }
1539 
1540 int  klassItable::_total_classes;   // Total no. of classes with itables
1541 long klassItable::_total_size;      // Total no. of bytes used for itables
1542 
1543 void klassItable::print_statistics() {
1544  tty->print_cr("itable statistics:");
1545  tty->print_cr("%6d classes with itables", _total_classes);
1546  tty->print_cr("%6d K uses for itables (average by class: %d bytes)", _total_size / K, _total_size / _total_classes);
1547 }
1548 
1549 #endif // PRODUCT