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/shared/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() == name && super_method->signature() == 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() ==  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() == name && super_method->signature() == signature) {
 403 
 404       // get super_klass for method_holder for the found method
 405       InstanceKlass* super_klass =  super_method->method_holder();
 406 
 407       // private methods are also never overridden
 408       if (!super_method->is_private() &&
 409           (is_default
 410           || ((super_klass->is_override(super_method, target_loader, target_classname, THREAD))
 411           || ((klass->major_version() >= VTABLE_TRANSITIVE_OVERRIDE_VERSION)
 412           && ((super_klass = find_transitive_override(super_klass,
 413                              target_method, i, target_loader,
 414                              target_classname, THREAD))
 415                              != (InstanceKlass*)NULL)))))
 416         {
 417         // Package private methods always need a new entry to root their own
 418         // overriding. They may also override other methods.
 419         if (!target_method()->is_package_private()) {
 420           allocate_new = false;
 421         }
 422 
 423         if (checkconstraints) {
 424         // Override vtable entry if passes loader constraint check
 425         // if loader constraint checking requested
 426         // No need to visit his super, since he and his super
 427         // have already made any needed loader constraints.
 428         // Since loader constraints are transitive, it is enough
 429         // to link to the first super, and we get all the others.
 430           Handle super_loader(THREAD, super_klass->class_loader());
 431 
 432           if (target_loader() != super_loader()) {
 433             ResourceMark rm(THREAD);
 434             Symbol* failed_type_symbol =
 435               SystemDictionary::check_signature_loaders(signature, target_loader,
 436                                                         super_loader, true,
 437                                                         CHECK_(false));
 438             if (failed_type_symbol != NULL) {
 439               const char* msg = "loader constraint violation: when resolving "
 440                 "overridden method \"%s\" the class loader (instance"
 441                 " of %s) of the current class, %s, and its superclass loader "
 442                 "(instance of %s), have different Class objects for the type "
 443                 "%s used in the signature";
 444               char* sig = target_method()->name_and_sig_as_C_string();
 445               const char* loader1 = SystemDictionary::loader_name(target_loader());
 446               char* current = target_klass->name()->as_C_string();
 447               const char* loader2 = SystemDictionary::loader_name(super_loader());
 448               char* failed_type_name = failed_type_symbol->as_C_string();
 449               size_t buflen = strlen(msg) + strlen(sig) + strlen(loader1) +
 450                 strlen(current) + strlen(loader2) + strlen(failed_type_name);
 451               char* buf = NEW_RESOURCE_ARRAY_IN_THREAD(THREAD, char, buflen);
 452               jio_snprintf(buf, buflen, msg, sig, loader1, current, loader2,
 453                            failed_type_name);
 454               THROW_MSG_(vmSymbols::java_lang_LinkageError(), buf, false);
 455             }
 456           }
 457        }
 458 
 459        put_method_at(target_method(), i);
 460        if (!is_default) {
 461          target_method()->set_vtable_index(i);
 462        } else {
 463          if (def_vtable_indices != NULL) {
 464            def_vtable_indices->at_put(default_index, i);
 465          }
 466          assert(super_method->is_default_method() || super_method->is_overpass()
 467                 || super_method->is_abstract(), "default override error");
 468        }
 469 
 470 
 471 #ifndef PRODUCT
 472         if (PrintVtables && Verbose) {
 473           ResourceMark rm(THREAD);
 474           char* sig = target_method()->name_and_sig_as_C_string();
 475           tty->print("overriding with %s::%s index %d, original flags: ",
 476            target_klass->internal_name(), sig, i);
 477            super_method->access_flags().print_on(tty);
 478            if (super_method->is_default_method()) {
 479              tty->print("default ");
 480            }
 481            if (super_method->is_overpass()) {
 482              tty->print("overpass");
 483            }
 484            tty->print("overriders flags: ");
 485            target_method->access_flags().print_on(tty);
 486            if (target_method->is_default_method()) {
 487              tty->print("default ");
 488            }
 489            if (target_method->is_overpass()) {
 490              tty->print("overpass");
 491            }
 492            tty->cr();
 493         }
 494 #endif /*PRODUCT*/
 495       } else {
 496         // allocate_new = true; default. We might override one entry,
 497         // but not override another. Once we override one, not need new
 498 #ifndef PRODUCT
 499         if (PrintVtables && Verbose) {
 500           ResourceMark rm(THREAD);
 501           char* sig = target_method()->name_and_sig_as_C_string();
 502           tty->print("NOT overriding with %s::%s index %d, original flags: ",
 503            target_klass->internal_name(), sig,i);
 504            super_method->access_flags().print_on(tty);
 505            if (super_method->is_default_method()) {
 506              tty->print("default ");
 507            }
 508            if (super_method->is_overpass()) {
 509              tty->print("overpass");
 510            }
 511            tty->print("overriders flags: ");
 512            target_method->access_flags().print_on(tty);
 513            if (target_method->is_default_method()) {
 514              tty->print("default ");
 515            }
 516            if (target_method->is_overpass()) {
 517              tty->print("overpass");
 518            }
 519            tty->cr();
 520         }
 521 #endif /*PRODUCT*/
 522       }
 523     }
 524   }
 525   return allocate_new;
 526 }
 527 
 528 void klassVtable::put_method_at(Method* m, int index) {
 529 #ifndef PRODUCT
 530   if (PrintVtables && Verbose) {
 531     ResourceMark rm;
 532     const char* sig = (m != NULL) ? m->name_and_sig_as_C_string() : "<NULL>";
 533     tty->print("adding %s at index %d, flags: ", sig, index);
 534     if (m != NULL) {
 535       m->access_flags().print_on(tty);
 536       if (m->is_default_method()) {
 537         tty->print("default ");
 538       }
 539       if (m->is_overpass()) {
 540         tty->print("overpass");
 541       }
 542     }
 543     tty->cr();
 544   }
 545 #endif
 546   table()[index].set(m);
 547 }
 548 
 549 // Find out if a method "m" with superclass "super", loader "classloader" and
 550 // name "classname" needs a new vtable entry.  Let P be a class package defined
 551 // by "classloader" and "classname".
 552 // NOTE: The logic used here is very similar to the one used for computing
 553 // the vtables indices for a method. We cannot directly use that function because,
 554 // we allocate the InstanceKlass at load time, and that requires that the
 555 // superclass has been loaded.
 556 // However, the vtable entries are filled in at link time, and therefore
 557 // the superclass' vtable may not yet have been filled in.
 558 bool klassVtable::needs_new_vtable_entry(methodHandle target_method,
 559                                          Klass* super,
 560                                          Handle classloader,
 561                                          Symbol* classname,
 562                                          AccessFlags class_flags,
 563                                          TRAPS) {
 564   if (class_flags.is_interface()) {
 565     // Interfaces do not use vtables, except for java.lang.Object methods,
 566     // so there is no point to assigning
 567     // a vtable index to any of their local methods.  If we refrain from doing this,
 568     // we can use Method::_vtable_index to hold the itable index
 569     return false;
 570   }
 571 
 572   if (target_method->is_final_method(class_flags) ||
 573       // a final method never needs a new entry; final methods can be statically
 574       // resolved and they have to be present in the vtable only if they override
 575       // a super's method, in which case they re-use its entry
 576       (target_method()->is_static()) ||
 577       // static methods don't need to be in vtable
 578       (target_method()->name() ==  vmSymbols::object_initializer_name())
 579       // <init> is never called dynamically-bound
 580       ) {
 581     return false;
 582   }
 583 
 584   // Concrete interface methods do not need new entries, they override
 585   // abstract method entries using default inheritance rules
 586   if (target_method()->method_holder() != NULL &&
 587       target_method()->method_holder()->is_interface()  &&
 588       !target_method()->is_abstract() ) {
 589     return false;
 590   }
 591 
 592   // we need a new entry if there is no superclass
 593   if (super == NULL) {
 594     return true;
 595   }
 596 
 597   // private methods in classes always have a new entry in the vtable
 598   // specification interpretation since classic has
 599   // private methods not overriding
 600   // JDK8 adds private  methods in interfaces which require invokespecial
 601   if (target_method()->is_private()) {
 602     return true;
 603   }
 604 
 605   // Package private methods always need a new entry to root their own
 606   // overriding. This allows transitive overriding to work.
 607   if (target_method()->is_package_private()) {
 608     return true;
 609   }
 610 
 611   // search through the super class hierarchy to see if we need
 612   // a new entry
 613   ResourceMark rm;
 614   Symbol* name = target_method()->name();
 615   Symbol* signature = target_method()->signature();
 616   Klass* k = super;
 617   Method* super_method = NULL;
 618   InstanceKlass *holder = NULL;
 619   Method* recheck_method =  NULL;
 620   while (k != NULL) {
 621     // lookup through the hierarchy for a method with matching name and sign.
 622     super_method = InstanceKlass::cast(k)->lookup_method(name, signature);
 623     if (super_method == NULL) {
 624       break; // we still have to search for a matching miranda method
 625     }
 626     // get the class holding the matching method
 627     // make sure you use that class for is_override
 628     InstanceKlass* superk = super_method->method_holder();
 629     // we want only instance method matches
 630     // pretend private methods are not in the super vtable
 631     // since we do override around them: e.g. a.m pub/b.m private/c.m pub,
 632     // ignore private, c.m pub does override a.m pub
 633     // For classes that were not javac'd together, we also do transitive overriding around
 634     // methods that have less accessibility
 635     if ((!super_method->is_static()) &&
 636        (!super_method->is_private())) {
 637       if (superk->is_override(super_method, classloader, classname, THREAD)) {
 638         return false;
 639       // else keep looking for transitive overrides
 640       }
 641     }
 642 
 643     // Start with lookup result and continue to search up
 644     k = superk->super(); // haven't found an override match yet; continue to look
 645   }
 646 
 647   // if the target method is public or protected it may have a matching
 648   // miranda method in the super, whose entry it should re-use.
 649   // Actually, to handle cases that javac would not generate, we need
 650   // this check for all access permissions.
 651   InstanceKlass *sk = InstanceKlass::cast(super);
 652   if (sk->has_miranda_methods()) {
 653     if (sk->lookup_method_in_all_interfaces(name, signature, Klass::find_defaults) != NULL) {
 654       return false;  // found a matching miranda; we do not need a new entry
 655     }
 656   }
 657   return true; // found no match; we need a new entry
 658 }
 659 
 660 // Support for miranda methods
 661 
 662 // get the vtable index of a miranda method with matching "name" and "signature"
 663 int klassVtable::index_of_miranda(Symbol* name, Symbol* signature) {
 664   // search from the bottom, might be faster
 665   for (int i = (length() - 1); i >= 0; i--) {
 666     Method* m = table()[i].method();
 667     if (is_miranda_entry_at(i) &&
 668         m->name() == name && m->signature() == signature) {
 669       return i;
 670     }
 671   }
 672   return Method::invalid_vtable_index;
 673 }
 674 
 675 // check if an entry at an index is miranda
 676 // requires that method m at entry be declared ("held") by an interface.
 677 bool klassVtable::is_miranda_entry_at(int i) {
 678   Method* m = method_at(i);
 679   Klass* method_holder = m->method_holder();
 680   InstanceKlass *mhk = InstanceKlass::cast(method_holder);
 681 
 682   // miranda methods are public abstract instance interface methods in a class's vtable
 683   if (mhk->is_interface()) {
 684     assert(m->is_public(), "should be public");
 685     assert(ik()->implements_interface(method_holder) , "this class should implement the interface");
 686     // the search could find a miranda or a default method
 687     if (is_miranda(m, ik()->methods(), ik()->default_methods(), ik()->super())) {
 688       return true;
 689     }
 690   }
 691   return false;
 692 }
 693 
 694 // check if a method is a miranda method, given a class's methods table,
 695 // its default_method table  and its super
 696 // Miranda methods are calculated twice:
 697 // first: before vtable size calculation: including abstract and superinterface default
 698 // We include potential default methods to give them space in the vtable.
 699 // During the first run, the default_methods list is empty
 700 // This is seen by default method creation
 701 // Second: recalculated during vtable initialization: only include abstract methods.
 702 // During the second run, default_methods is set up, so concrete methods from
 703 // superinterfaces with matching names/signatures to default_methods are already
 704 // in the default_methods list and do not need to be appended to the vtable
 705 // as mirandas
 706 // This is seen by link resolution and selection.
 707 // "miranda" means not static, not defined by this class.
 708 // private methods in interfaces do not belong in the miranda list.
 709 // the caller must make sure that the method belongs to an interface implemented by the class
 710 // Miranda methods only include public interface instance methods
 711 // Not private methods, not static methods, not default == concrete abstract
 712 // Miranda methods also do not include overpass methods in interfaces
 713 bool klassVtable::is_miranda(Method* m, Array<Method*>* class_methods,
 714                              Array<Method*>* default_methods, Klass* super) {
 715   if (m->is_static() || m->is_private() || m->is_overpass()) {
 716     return false;
 717   }
 718   Symbol* name = m->name();
 719   Symbol* signature = m->signature();
 720   Method* mo;
 721 
 722   if ((mo = InstanceKlass::find_instance_method(class_methods, name, signature)) == NULL) {
 723     // did not find it in the method table of the current class
 724     if ((default_methods == NULL) ||
 725         InstanceKlass::find_method(default_methods, name, signature) == NULL) {
 726       if (super == NULL) {
 727         // super doesn't exist
 728         return true;
 729       }
 730 
 731       mo = InstanceKlass::cast(super)->lookup_method(name, signature);
 732       while (mo != NULL && mo->access_flags().is_static()
 733              && mo->method_holder() != NULL
 734              && mo->method_holder()->super() != NULL)
 735       {
 736          mo = mo->method_holder()->super()->uncached_lookup_method(name, signature, Klass::find_overpass);
 737       }
 738       if (mo == NULL || mo->access_flags().is_private() ) {
 739         // super class hierarchy does not implement it or protection is different
 740         return true;
 741       }
 742     }
 743   } else {
 744      // if the local class has a private method, the miranda will not
 745      // override it, so a vtable slot is needed
 746      if (mo->access_flags().is_private()) {
 747 
 748        // Second round, weed out any superinterface methods that turned
 749        // into default methods, i.e. were concrete not abstract in the end
 750        if ((default_methods == NULL) ||
 751          InstanceKlass::find_method(default_methods, name, signature) == NULL) {
 752          return true;
 753        }
 754     }
 755   }
 756 
 757   return false;
 758 }
 759 
 760 // Scans current_interface_methods for miranda methods that do not
 761 // already appear in new_mirandas, or default methods,  and are also not defined-and-non-private
 762 // in super (superclass).  These mirandas are added to all_mirandas if it is
 763 // not null; in addition, those that are not duplicates of miranda methods
 764 // inherited by super from its interfaces are added to new_mirandas.
 765 // Thus, new_mirandas will be the set of mirandas that this class introduces,
 766 // all_mirandas will be the set of all mirandas applicable to this class
 767 // including all defined in superclasses.
 768 void klassVtable::add_new_mirandas_to_lists(
 769     GrowableArray<Method*>* new_mirandas, GrowableArray<Method*>* all_mirandas,
 770     Array<Method*>* current_interface_methods, Array<Method*>* class_methods,
 771     Array<Method*>* default_methods, Klass* super) {
 772 
 773   // iterate thru the current interface's method to see if it a miranda
 774   int num_methods = current_interface_methods->length();
 775   for (int i = 0; i < num_methods; i++) {
 776     Method* im = current_interface_methods->at(i);
 777     bool is_duplicate = false;
 778     int num_of_current_mirandas = new_mirandas->length();
 779     // check for duplicate mirandas in different interfaces we implement
 780     for (int j = 0; j < num_of_current_mirandas; j++) {
 781       Method* miranda = new_mirandas->at(j);
 782       if ((im->name() == miranda->name()) &&
 783           (im->signature() == miranda->signature())) {
 784         is_duplicate = true;
 785         break;
 786       }
 787     }
 788 
 789     if (!is_duplicate) { // we don't want duplicate miranda entries in the vtable
 790       if (is_miranda(im, class_methods, default_methods, super)) { // is it a miranda at all?
 791         InstanceKlass *sk = InstanceKlass::cast(super);
 792         // check if it is a duplicate of a super's miranda
 793         if (sk->lookup_method_in_all_interfaces(im->name(), im->signature(), Klass::find_defaults) == NULL) {
 794           new_mirandas->append(im);
 795         }
 796         if (all_mirandas != NULL) {
 797           all_mirandas->append(im);
 798         }
 799       }
 800     }
 801   }
 802 }
 803 
 804 void klassVtable::get_mirandas(GrowableArray<Method*>* new_mirandas,
 805                                GrowableArray<Method*>* all_mirandas,
 806                                Klass* super, Array<Method*>* class_methods,
 807                                Array<Method*>* default_methods,
 808                                Array<Klass*>* local_interfaces) {
 809   assert((new_mirandas->length() == 0) , "current mirandas must be 0");
 810 
 811   // iterate thru the local interfaces looking for a miranda
 812   int num_local_ifs = local_interfaces->length();
 813   for (int i = 0; i < num_local_ifs; i++) {
 814     InstanceKlass *ik = InstanceKlass::cast(local_interfaces->at(i));
 815     add_new_mirandas_to_lists(new_mirandas, all_mirandas,
 816                               ik->methods(), class_methods,
 817                               default_methods, super);
 818     // iterate thru each local's super interfaces
 819     Array<Klass*>* super_ifs = ik->transitive_interfaces();
 820     int num_super_ifs = super_ifs->length();
 821     for (int j = 0; j < num_super_ifs; j++) {
 822       InstanceKlass *sik = InstanceKlass::cast(super_ifs->at(j));
 823       add_new_mirandas_to_lists(new_mirandas, all_mirandas,
 824                                 sik->methods(), class_methods,
 825                                 default_methods, super);
 826     }
 827   }
 828 }
 829 
 830 // Discover miranda methods ("miranda" = "interface abstract, no binding"),
 831 // and append them into the vtable starting at index initialized,
 832 // return the new value of initialized.
 833 // Miranda methods use vtable entries, but do not get assigned a vtable_index
 834 // The vtable_index is discovered by searching from the end of the vtable
 835 int klassVtable::fill_in_mirandas(int initialized) {
 836   GrowableArray<Method*> mirandas(20);
 837   get_mirandas(&mirandas, NULL, ik()->super(), ik()->methods(),
 838                ik()->default_methods(), ik()->local_interfaces());
 839   for (int i = 0; i < mirandas.length(); i++) {
 840     if (PrintVtables && Verbose) {
 841       Method* meth = mirandas.at(i);
 842       ResourceMark rm(Thread::current());
 843       if (meth != NULL) {
 844         char* sig = meth->name_and_sig_as_C_string();
 845         tty->print("fill in mirandas with %s index %d, flags: ",
 846           sig, initialized);
 847         meth->access_flags().print_on(tty);
 848         if (meth->is_default_method()) {
 849           tty->print("default ");
 850         }
 851         tty->cr();
 852       }
 853     }
 854     put_method_at(mirandas.at(i), initialized);
 855     ++initialized;
 856   }
 857   return initialized;
 858 }
 859 
 860 // Copy this class's vtable to the vtable beginning at start.
 861 // Used to copy superclass vtable to prefix of subclass's vtable.
 862 void klassVtable::copy_vtable_to(vtableEntry* start) {
 863   Copy::disjoint_words((HeapWord*)table(), (HeapWord*)start, _length * vtableEntry::size());
 864 }
 865 
 866 #if INCLUDE_JVMTI
 867 bool klassVtable::adjust_default_method(int vtable_index, Method* old_method, Method* new_method) {
 868   // If old_method is default, find this vtable index in default_vtable_indices
 869   // and replace that method in the _default_methods list
 870   bool updated = false;
 871 
 872   Array<Method*>* default_methods = ik()->default_methods();
 873   if (default_methods != NULL) {
 874     int len = default_methods->length();
 875     for (int idx = 0; idx < len; idx++) {
 876       if (vtable_index == ik()->default_vtable_indices()->at(idx)) {
 877         if (default_methods->at(idx) == old_method) {
 878           default_methods->at_put(idx, new_method);
 879           updated = true;
 880         }
 881         break;
 882       }
 883     }
 884   }
 885   return updated;
 886 }
 887 
 888 // search the vtable for uses of either obsolete or EMCP methods
 889 void klassVtable::adjust_method_entries(InstanceKlass* holder, bool * trace_name_printed) {
 890   int prn_enabled = 0;
 891   for (int index = 0; index < length(); index++) {
 892     Method* old_method = unchecked_method_at(index);
 893     if (old_method == NULL || old_method->method_holder() != holder || !old_method->is_old()) {
 894       continue; // skip uninteresting entries
 895     }
 896     assert(!old_method->is_deleted(), "vtable methods may not be deleted");
 897 
 898     Method* new_method = holder->method_with_idnum(old_method->orig_method_idnum());
 899 
 900     assert(new_method != NULL, "method_with_idnum() should not be NULL");
 901     assert(old_method != new_method, "sanity check");
 902 
 903     put_method_at(new_method, index);
 904     // For default methods, need to update the _default_methods array
 905     // which can only have one method entry for a given signature
 906     bool updated_default = false;
 907     if (old_method->is_default_method()) {
 908       updated_default = adjust_default_method(index, old_method, new_method);
 909     }
 910 
 911     if (RC_TRACE_IN_RANGE(0x00100000, 0x00400000)) {
 912       if (!(*trace_name_printed)) {
 913         // RC_TRACE_MESG macro has an embedded ResourceMark
 914         RC_TRACE_MESG(("adjust: klassname=%s for methods from name=%s",
 915                        klass()->external_name(),
 916                        old_method->method_holder()->external_name()));
 917         *trace_name_printed = true;
 918       }
 919       // RC_TRACE macro has an embedded ResourceMark
 920       RC_TRACE(0x00100000, ("vtable method update: %s(%s), updated default = %s",
 921                             new_method->name()->as_C_string(),
 922                             new_method->signature()->as_C_string(),
 923                             updated_default ? "true" : "false"));
 924     }
 925   }
 926 }
 927 
 928 // a vtable should never contain old or obsolete methods
 929 bool klassVtable::check_no_old_or_obsolete_entries() {
 930   for (int i = 0; i < length(); i++) {
 931     Method* m = unchecked_method_at(i);
 932     if (m != NULL &&
 933         (NOT_PRODUCT(!m->is_valid() ||) m->is_old() || m->is_obsolete())) {
 934       return false;
 935     }
 936   }
 937   return true;
 938 }
 939 
 940 void klassVtable::dump_vtable() {
 941   tty->print_cr("vtable dump --");
 942   for (int i = 0; i < length(); i++) {
 943     Method* m = unchecked_method_at(i);
 944     if (m != NULL) {
 945       tty->print("      (%5d)  ", i);
 946       m->access_flags().print_on(tty);
 947       if (m->is_default_method()) {
 948         tty->print("default ");
 949       }
 950       if (m->is_overpass()) {
 951         tty->print("overpass");
 952       }
 953       tty->print(" --  ");
 954       m->print_name(tty);
 955       tty->cr();
 956     }
 957   }
 958 }
 959 #endif // INCLUDE_JVMTI
 960 
 961 // CDS/RedefineClasses support - clear vtables so they can be reinitialized
 962 void klassVtable::clear_vtable() {
 963   for (int i = 0; i < _length; i++) table()[i].clear();
 964 }
 965 
 966 bool klassVtable::is_initialized() {
 967   return _length == 0 || table()[0].method() != NULL;
 968 }
 969 
 970 //-----------------------------------------------------------------------------------------
 971 // Itable code
 972 
 973 // Initialize a itableMethodEntry
 974 void itableMethodEntry::initialize(Method* m) {
 975   if (m == NULL) return;
 976 
 977   _method = m;
 978 }
 979 
 980 klassItable::klassItable(instanceKlassHandle klass) {
 981   _klass = klass;
 982 
 983   if (klass->itable_length() > 0) {
 984     itableOffsetEntry* offset_entry = (itableOffsetEntry*)klass->start_of_itable();
 985     if (offset_entry  != NULL && offset_entry->interface_klass() != NULL) { // Check that itable is initialized
 986       // First offset entry points to the first method_entry
 987       intptr_t* method_entry  = (intptr_t *)(((address)klass()) + offset_entry->offset());
 988       intptr_t* end         = klass->end_of_itable();
 989 
 990       _table_offset      = (intptr_t*)offset_entry - (intptr_t*)klass();
 991       _size_offset_table = (method_entry - ((intptr_t*)offset_entry)) / itableOffsetEntry::size();
 992       _size_method_table = (end - method_entry)                  / itableMethodEntry::size();
 993       assert(_table_offset >= 0 && _size_offset_table >= 0 && _size_method_table >= 0, "wrong computation");
 994       return;
 995     }
 996   }
 997 
 998   // The length of the itable was either zero, or it has not yet been initialized.
 999   _table_offset      = 0;
1000   _size_offset_table = 0;
1001   _size_method_table = 0;
1002 }
1003 
1004 static int initialize_count = 0;
1005 
1006 // Initialization
1007 void klassItable::initialize_itable(bool checkconstraints, TRAPS) {
1008   if (_klass->is_interface()) {
1009     // This needs to go after vtable indices are assigned but
1010     // before implementors need to know the number of itable indices.
1011     assign_itable_indices_for_interface(_klass());
1012   }
1013 
1014   // Cannot be setup doing bootstrapping, interfaces don't have
1015   // itables, and klass with only ones entry have empty itables
1016   if (Universe::is_bootstrapping() ||
1017       _klass->is_interface() ||
1018       _klass->itable_length() == itableOffsetEntry::size()) return;
1019 
1020   // There's alway an extra itable entry so we can null-terminate it.
1021   guarantee(size_offset_table() >= 1, "too small");
1022   int num_interfaces = size_offset_table() - 1;
1023   if (num_interfaces > 0) {
1024     if (TraceItables) tty->print_cr("%3d: Initializing itables for %s", ++initialize_count,
1025                                     _klass->name()->as_C_string());
1026 
1027 
1028     // Iterate through all interfaces
1029     int i;
1030     for(i = 0; i < num_interfaces; i++) {
1031       itableOffsetEntry* ioe = offset_entry(i);
1032       HandleMark hm(THREAD);
1033       KlassHandle interf_h (THREAD, ioe->interface_klass());
1034       assert(interf_h() != NULL && ioe->offset() != 0, "bad offset entry in itable");
1035       initialize_itable_for_interface(ioe->offset(), interf_h, checkconstraints, CHECK);
1036     }
1037 
1038   }
1039   // Check that the last entry is empty
1040   itableOffsetEntry* ioe = offset_entry(size_offset_table() - 1);
1041   guarantee(ioe->interface_klass() == NULL && ioe->offset() == 0, "terminator entry missing");
1042 }
1043 
1044 
1045 inline bool interface_method_needs_itable_index(Method* m) {
1046   if (m->is_static())           return false;   // e.g., Stream.empty
1047   if (m->is_initializer())      return false;   // <init> or <clinit>
1048   // If an interface redeclares a method from java.lang.Object,
1049   // it should already have a vtable index, don't touch it.
1050   // e.g., CharSequence.toString (from initialize_vtable)
1051   // if (m->has_vtable_index())  return false; // NO!
1052   return true;
1053 }
1054 
1055 int klassItable::assign_itable_indices_for_interface(Klass* klass) {
1056   // an interface does not have an itable, but its methods need to be numbered
1057   if (TraceItables) tty->print_cr("%3d: Initializing itable for interface %s", ++initialize_count,
1058                                   klass->name()->as_C_string());
1059   Array<Method*>* methods = InstanceKlass::cast(klass)->methods();
1060   int nof_methods = methods->length();
1061   int ime_num = 0;
1062   for (int i = 0; i < nof_methods; i++) {
1063     Method* m = methods->at(i);
1064     if (interface_method_needs_itable_index(m)) {
1065       assert(!m->is_final_method(), "no final interface methods");
1066       // If m is already assigned a vtable index, do not disturb it.
1067       if (TraceItables && Verbose) {
1068         ResourceMark rm;
1069         const char* sig = (m != NULL) ? m->name_and_sig_as_C_string() : "<NULL>";
1070         if (m->has_vtable_index()) {
1071           tty->print("itable index %d for method: %s, flags: ", m->vtable_index(), sig);
1072         } else {
1073           tty->print("itable index %d for method: %s, flags: ", ime_num, sig);
1074         }
1075         if (m != NULL) {
1076           m->access_flags().print_on(tty);
1077           if (m->is_default_method()) {
1078             tty->print("default ");
1079           }
1080           if (m->is_overpass()) {
1081             tty->print("overpass");
1082           }
1083         }
1084         tty->cr();
1085       }
1086       if (!m->has_vtable_index()) {
1087         assert(m->vtable_index() == Method::pending_itable_index, "set by initialize_vtable");
1088         m->set_itable_index(ime_num);
1089         // Progress to next itable entry
1090         ime_num++;
1091       }
1092     }
1093   }
1094   assert(ime_num == method_count_for_interface(klass), "proper sizing");
1095   return ime_num;
1096 }
1097 
1098 int klassItable::method_count_for_interface(Klass* interf) {
1099   assert(interf->oop_is_instance(), "must be");
1100   assert(interf->is_interface(), "must be");
1101   Array<Method*>* methods = InstanceKlass::cast(interf)->methods();
1102   int nof_methods = methods->length();
1103   while (nof_methods > 0) {
1104     Method* m = methods->at(nof_methods-1);
1105     if (m->has_itable_index()) {
1106       int length = m->itable_index() + 1;
1107 #ifdef ASSERT
1108       while (nof_methods = 0) {
1109         m = methods->at(--nof_methods);
1110         assert(!m->has_itable_index() || m->itable_index() < length, "");
1111       }
1112 #endif //ASSERT
1113       return length;  // return the rightmost itable index, plus one
1114     }
1115     nof_methods -= 1;
1116   }
1117   // no methods have itable indices
1118   return 0;
1119 }
1120 
1121 
1122 void klassItable::initialize_itable_for_interface(int method_table_offset, KlassHandle interf_h, bool checkconstraints, TRAPS) {
1123   Array<Method*>* methods = InstanceKlass::cast(interf_h())->methods();
1124   int nof_methods = methods->length();
1125   HandleMark hm;
1126   assert(nof_methods > 0, "at least one method must exist for interface to be in vtable");
1127   Handle interface_loader (THREAD, InstanceKlass::cast(interf_h())->class_loader());
1128 
1129   int ime_count = method_count_for_interface(interf_h());
1130   for (int i = 0; i < nof_methods; i++) {
1131     Method* m = methods->at(i);
1132     methodHandle target;
1133     if (m->has_itable_index()) {
1134       // This search must match the runtime resolution, i.e. selection search for invokeinterface
1135       // to correctly enforce loader constraints for interface method inheritance
1136       LinkResolver::lookup_instance_method_in_klasses(target, _klass, m->name(), m->signature(), CHECK);
1137     }
1138     if (target == NULL || !target->is_public() || target->is_abstract()) {
1139       // Entry does not resolve. Leave it empty for AbstractMethodError.
1140         if (!(target == NULL) && !target->is_public()) {
1141           // Stuff an IllegalAccessError throwing method in there instead.
1142           itableOffsetEntry::method_entry(_klass(), method_table_offset)[m->itable_index()].
1143               initialize(Universe::throw_illegal_access_error());
1144         }
1145     } else {
1146       // Entry did resolve, check loader constraints before initializing
1147       // if checkconstraints requested
1148       if (checkconstraints) {
1149         Handle method_holder_loader (THREAD, target->method_holder()->class_loader());
1150         if (method_holder_loader() != interface_loader()) {
1151           ResourceMark rm(THREAD);
1152           Symbol* failed_type_symbol =
1153             SystemDictionary::check_signature_loaders(m->signature(),
1154                                                       method_holder_loader,
1155                                                       interface_loader,
1156                                                       true, CHECK);
1157           if (failed_type_symbol != NULL) {
1158             const char* msg = "loader constraint violation in interface "
1159               "itable initialization: when resolving method \"%s\" the class"
1160               " loader (instance of %s) of the current class, %s, "
1161               "and the class loader (instance of %s) for interface "
1162               "%s have different Class objects for the type %s "
1163               "used in the signature";
1164             char* sig = target()->name_and_sig_as_C_string();
1165             const char* loader1 = SystemDictionary::loader_name(method_holder_loader());
1166             char* current = _klass->name()->as_C_string();
1167             const char* loader2 = SystemDictionary::loader_name(interface_loader());
1168             char* iface = InstanceKlass::cast(interf_h())->name()->as_C_string();
1169             char* failed_type_name = failed_type_symbol->as_C_string();
1170             size_t buflen = strlen(msg) + strlen(sig) + strlen(loader1) +
1171               strlen(current) + strlen(loader2) + strlen(iface) +
1172               strlen(failed_type_name);
1173             char* buf = NEW_RESOURCE_ARRAY_IN_THREAD(THREAD, char, buflen);
1174             jio_snprintf(buf, buflen, msg, sig, loader1, current, loader2,
1175                          iface, failed_type_name);
1176             THROW_MSG(vmSymbols::java_lang_LinkageError(), buf);
1177           }
1178         }
1179       }
1180 
1181       // ime may have moved during GC so recalculate address
1182       int ime_num = m->itable_index();
1183       assert(ime_num < ime_count, "oob");
1184       itableOffsetEntry::method_entry(_klass(), method_table_offset)[ime_num].initialize(target());
1185       if (TraceItables && Verbose) {
1186         ResourceMark rm(THREAD);
1187         if (target() != NULL) {
1188           char* sig = target()->name_and_sig_as_C_string();
1189           tty->print("interface: %s, ime_num: %d, target: %s, method_holder: %s ",
1190                     interf_h()->internal_name(), ime_num, sig,
1191                     target()->method_holder()->internal_name());
1192           tty->print("target_method flags: ");
1193           target()->access_flags().print_on(tty);
1194           if (target()->is_default_method()) {
1195             tty->print("default ");
1196           }
1197           tty->cr();
1198         }
1199       }
1200     }
1201   }
1202 }
1203 
1204 // Update entry for specific Method*
1205 void klassItable::initialize_with_method(Method* m) {
1206   itableMethodEntry* ime = method_entry(0);
1207   for(int i = 0; i < _size_method_table; i++) {
1208     if (ime->method() == m) {
1209       ime->initialize(m);
1210     }
1211     ime++;
1212   }
1213 }
1214 
1215 #if INCLUDE_JVMTI
1216 // search the itable for uses of either obsolete or EMCP methods
1217 void klassItable::adjust_method_entries(InstanceKlass* holder, bool * trace_name_printed) {
1218 
1219   itableMethodEntry* ime = method_entry(0);
1220   for (int i = 0; i < _size_method_table; i++, ime++) {
1221     Method* old_method = ime->method();
1222     if (old_method == NULL || old_method->method_holder() != holder || !old_method->is_old()) {
1223       continue; // skip uninteresting entries
1224     }
1225     assert(!old_method->is_deleted(), "itable methods may not be deleted");
1226 
1227     Method* new_method = holder->method_with_idnum(old_method->orig_method_idnum());
1228 
1229     assert(new_method != NULL, "method_with_idnum() should not be NULL");
1230     assert(old_method != new_method, "sanity check");
1231 
1232     ime->initialize(new_method);
1233 
1234     if (RC_TRACE_IN_RANGE(0x00100000, 0x00400000)) {
1235       if (!(*trace_name_printed)) {
1236         // RC_TRACE_MESG macro has an embedded ResourceMark
1237         RC_TRACE_MESG(("adjust: name=%s",
1238           old_method->method_holder()->external_name()));
1239         *trace_name_printed = true;
1240       }
1241       // RC_TRACE macro has an embedded ResourceMark
1242       RC_TRACE(0x00200000, ("itable method update: %s(%s)",
1243         new_method->name()->as_C_string(),
1244         new_method->signature()->as_C_string()));
1245     }
1246   }
1247 }
1248 
1249 // an itable should never contain old or obsolete methods
1250 bool klassItable::check_no_old_or_obsolete_entries() {
1251   itableMethodEntry* ime = method_entry(0);
1252   for (int i = 0; i < _size_method_table; i++) {
1253     Method* m = ime->method();
1254     if (m != NULL &&
1255         (NOT_PRODUCT(!m->is_valid() ||) m->is_old() || m->is_obsolete())) {
1256       return false;
1257     }
1258     ime++;
1259   }
1260   return true;
1261 }
1262 
1263 void klassItable::dump_itable() {
1264   itableMethodEntry* ime = method_entry(0);
1265   tty->print_cr("itable dump --");
1266   for (int i = 0; i < _size_method_table; i++) {
1267     Method* m = ime->method();
1268     if (m != NULL) {
1269       tty->print("      (%5d)  ", i);
1270       m->access_flags().print_on(tty);
1271       if (m->is_default_method()) {
1272         tty->print("default ");
1273       }
1274       tty->print(" --  ");
1275       m->print_name(tty);
1276       tty->cr();
1277     }
1278     ime++;
1279   }
1280 }
1281 #endif // INCLUDE_JVMTI
1282 
1283 
1284 // Setup
1285 class InterfaceVisiterClosure : public StackObj {
1286  public:
1287   virtual void doit(Klass* intf, int method_count) = 0;
1288 };
1289 
1290 // Visit all interfaces with at least one itable method
1291 void visit_all_interfaces(Array<Klass*>* transitive_intf, InterfaceVisiterClosure *blk) {
1292   // Handle array argument
1293   for(int i = 0; i < transitive_intf->length(); i++) {
1294     Klass* intf = transitive_intf->at(i);
1295     assert(intf->is_interface(), "sanity check");
1296 
1297     // Find no. of itable methods
1298     int method_count = 0;
1299     // method_count = klassItable::method_count_for_interface(intf);
1300     Array<Method*>* methods = InstanceKlass::cast(intf)->methods();
1301     if (methods->length() > 0) {
1302       for (int i = methods->length(); --i >= 0; ) {
1303         if (interface_method_needs_itable_index(methods->at(i))) {
1304           method_count++;
1305         }
1306       }
1307     }
1308 
1309     // Only count interfaces with at least one method
1310     if (method_count > 0) {
1311       blk->doit(intf, method_count);
1312     }
1313   }
1314 }
1315 
1316 class CountInterfacesClosure : public InterfaceVisiterClosure {
1317  private:
1318   int _nof_methods;
1319   int _nof_interfaces;
1320  public:
1321    CountInterfacesClosure() { _nof_methods = 0; _nof_interfaces = 0; }
1322 
1323    int nof_methods() const    { return _nof_methods; }
1324    int nof_interfaces() const { return _nof_interfaces; }
1325 
1326    void doit(Klass* intf, int method_count) { _nof_methods += method_count; _nof_interfaces++; }
1327 };
1328 
1329 class SetupItableClosure : public InterfaceVisiterClosure  {
1330  private:
1331   itableOffsetEntry* _offset_entry;
1332   itableMethodEntry* _method_entry;
1333   address            _klass_begin;
1334  public:
1335   SetupItableClosure(address klass_begin, itableOffsetEntry* offset_entry, itableMethodEntry* method_entry) {
1336     _klass_begin  = klass_begin;
1337     _offset_entry = offset_entry;
1338     _method_entry = method_entry;
1339   }
1340 
1341   itableMethodEntry* method_entry() const { return _method_entry; }
1342 
1343   void doit(Klass* intf, int method_count) {
1344     int offset = ((address)_method_entry) - _klass_begin;
1345     _offset_entry->initialize(intf, offset);
1346     _offset_entry++;
1347     _method_entry += method_count;
1348   }
1349 };
1350 
1351 int klassItable::compute_itable_size(Array<Klass*>* transitive_interfaces) {
1352   // Count no of interfaces and total number of interface methods
1353   CountInterfacesClosure cic;
1354   visit_all_interfaces(transitive_interfaces, &cic);
1355 
1356   // There's alway an extra itable entry so we can null-terminate it.
1357   int itable_size = calc_itable_size(cic.nof_interfaces() + 1, cic.nof_methods());
1358 
1359   // Statistics
1360   update_stats(itable_size * HeapWordSize);
1361 
1362   return itable_size;
1363 }
1364 
1365 
1366 // Fill out offset table and interface klasses into the itable space
1367 void klassItable::setup_itable_offset_table(instanceKlassHandle klass) {
1368   if (klass->itable_length() == 0) return;
1369   assert(!klass->is_interface(), "Should have zero length itable");
1370 
1371   // Count no of interfaces and total number of interface methods
1372   CountInterfacesClosure cic;
1373   visit_all_interfaces(klass->transitive_interfaces(), &cic);
1374   int nof_methods    = cic.nof_methods();
1375   int nof_interfaces = cic.nof_interfaces();
1376 
1377   // Add one extra entry so we can null-terminate the table
1378   nof_interfaces++;
1379 
1380   assert(compute_itable_size(klass->transitive_interfaces()) ==
1381          calc_itable_size(nof_interfaces, nof_methods),
1382          "mismatch calculation of itable size");
1383 
1384   // Fill-out offset table
1385   itableOffsetEntry* ioe = (itableOffsetEntry*)klass->start_of_itable();
1386   itableMethodEntry* ime = (itableMethodEntry*)(ioe + nof_interfaces);
1387   intptr_t* end               = klass->end_of_itable();
1388   assert((oop*)(ime + nof_methods) <= (oop*)klass->start_of_nonstatic_oop_maps(), "wrong offset calculation (1)");
1389   assert((oop*)(end) == (oop*)(ime + nof_methods),                      "wrong offset calculation (2)");
1390 
1391   // Visit all interfaces and initialize itable offset table
1392   SetupItableClosure sic((address)klass(), ioe, ime);
1393   visit_all_interfaces(klass->transitive_interfaces(), &sic);
1394 
1395 #ifdef ASSERT
1396   ime  = sic.method_entry();
1397   oop* v = (oop*) klass->end_of_itable();
1398   assert( (oop*)(ime) == v, "wrong offset calculation (2)");
1399 #endif
1400 }
1401 
1402 
1403 // inverse to itable_index
1404 Method* klassItable::method_for_itable_index(Klass* intf, int itable_index) {
1405   assert(InstanceKlass::cast(intf)->is_interface(), "sanity check");
1406   assert(intf->verify_itable_index(itable_index), "");
1407   Array<Method*>* methods = InstanceKlass::cast(intf)->methods();
1408 
1409   if (itable_index < 0 || itable_index >= method_count_for_interface(intf))
1410     return NULL;                // help caller defend against bad indices
1411 
1412   int index = itable_index;
1413   Method* m = methods->at(index);
1414   int index2 = -1;
1415   while (!m->has_itable_index() ||
1416          (index2 = m->itable_index()) != itable_index) {
1417     assert(index2 < itable_index, "monotonic");
1418     if (++index == methods->length())
1419       return NULL;
1420     m = methods->at(index);
1421   }
1422   assert(m->itable_index() == itable_index, "correct inverse");
1423 
1424   return m;
1425 }
1426 
1427 void klassVtable::verify(outputStream* st, bool forced) {
1428   // make sure table is initialized
1429   if (!Universe::is_fully_initialized()) return;
1430 #ifndef PRODUCT
1431   // avoid redundant verifies
1432   if (!forced && _verify_count == Universe::verify_count()) return;
1433   _verify_count = Universe::verify_count();
1434 #endif
1435   oop* end_of_obj = (oop*)_klass() + _klass()->size();
1436   oop* end_of_vtable = (oop *)&table()[_length];
1437   if (end_of_vtable > end_of_obj) {
1438     fatal(err_msg("klass %s: klass object too short (vtable extends beyond "
1439                   "end)", _klass->internal_name()));
1440   }
1441 
1442   for (int i = 0; i < _length; i++) table()[i].verify(this, st);
1443   // verify consistency with superKlass vtable
1444   Klass* super = _klass->super();
1445   if (super != NULL) {
1446     InstanceKlass* sk = InstanceKlass::cast(super);
1447     klassVtable* vt = sk->vtable();
1448     for (int i = 0; i < vt->length(); i++) {
1449       verify_against(st, vt, i);
1450     }
1451   }
1452 }
1453 
1454 void klassVtable::verify_against(outputStream* st, klassVtable* vt, int index) {
1455   vtableEntry* vte = &vt->table()[index];
1456   if (vte->method()->name()      != table()[index].method()->name() ||
1457       vte->method()->signature() != table()[index].method()->signature()) {
1458     fatal("mismatched name/signature of vtable entries");
1459   }
1460 }
1461 
1462 #ifndef PRODUCT
1463 void klassVtable::print() {
1464   ResourceMark rm;
1465   tty->print("klassVtable for klass %s (length %d):\n", _klass->internal_name(), length());
1466   for (int i = 0; i < length(); i++) {
1467     table()[i].print();
1468     tty->cr();
1469   }
1470 }
1471 #endif
1472 
1473 void vtableEntry::verify(klassVtable* vt, outputStream* st) {
1474   NOT_PRODUCT(FlagSetting fs(IgnoreLockingAssertions, true));
1475   assert(method() != NULL, "must have set method");
1476   method()->verify();
1477   // we sub_type, because it could be a miranda method
1478   if (!vt->klass()->is_subtype_of(method()->method_holder())) {
1479 #ifndef PRODUCT
1480     print();
1481 #endif
1482     fatal(err_msg("vtableEntry " PTR_FORMAT ": method is from subclass", this));
1483   }
1484 }
1485 
1486 #ifndef PRODUCT
1487 
1488 void vtableEntry::print() {
1489   ResourceMark rm;
1490   tty->print("vtableEntry %s: ", method()->name()->as_C_string());
1491   if (Verbose) {
1492     tty->print("m %#lx ", (address)method());
1493   }
1494 }
1495 
1496 class VtableStats : AllStatic {
1497  public:
1498   static int no_klasses;                // # classes with vtables
1499   static int no_array_klasses;          // # array classes
1500   static int no_instance_klasses;       // # instanceKlasses
1501   static int sum_of_vtable_len;         // total # of vtable entries
1502   static int sum_of_array_vtable_len;   // total # of vtable entries in array klasses only
1503   static int fixed;                     // total fixed overhead in bytes
1504   static int filler;                    // overhead caused by filler bytes
1505   static int entries;                   // total bytes consumed by vtable entries
1506   static int array_entries;             // total bytes consumed by array vtable entries
1507 
1508   static void do_class(Klass* k) {
1509     Klass* kl = k;
1510     klassVtable* vt = kl->vtable();
1511     if (vt == NULL) return;
1512     no_klasses++;
1513     if (kl->oop_is_instance()) {
1514       no_instance_klasses++;
1515       kl->array_klasses_do(do_class);
1516     }
1517     if (kl->oop_is_array()) {
1518       no_array_klasses++;
1519       sum_of_array_vtable_len += vt->length();
1520     }
1521     sum_of_vtable_len += vt->length();
1522   }
1523 
1524   static void compute() {
1525     SystemDictionary::classes_do(do_class);
1526     fixed  = no_klasses * oopSize;      // vtable length
1527     // filler size is a conservative approximation
1528     filler = oopSize * (no_klasses - no_instance_klasses) * (sizeof(InstanceKlass) - sizeof(ArrayKlass) - 1);
1529     entries = sizeof(vtableEntry) * sum_of_vtable_len;
1530     array_entries = sizeof(vtableEntry) * sum_of_array_vtable_len;
1531   }
1532 };
1533 
1534 int VtableStats::no_klasses = 0;
1535 int VtableStats::no_array_klasses = 0;
1536 int VtableStats::no_instance_klasses = 0;
1537 int VtableStats::sum_of_vtable_len = 0;
1538 int VtableStats::sum_of_array_vtable_len = 0;
1539 int VtableStats::fixed = 0;
1540 int VtableStats::filler = 0;
1541 int VtableStats::entries = 0;
1542 int VtableStats::array_entries = 0;
1543 
1544 void klassVtable::print_statistics() {
1545   ResourceMark rm;
1546   HandleMark hm;
1547   VtableStats::compute();
1548   tty->print_cr("vtable statistics:");
1549   tty->print_cr("%6d classes (%d instance, %d array)", VtableStats::no_klasses, VtableStats::no_instance_klasses, VtableStats::no_array_klasses);
1550   int total = VtableStats::fixed + VtableStats::filler + VtableStats::entries;
1551   tty->print_cr("%6d bytes fixed overhead (refs + vtable object header)", VtableStats::fixed);
1552   tty->print_cr("%6d bytes filler overhead", VtableStats::filler);
1553   tty->print_cr("%6d bytes for vtable entries (%d for arrays)", VtableStats::entries, VtableStats::array_entries);
1554   tty->print_cr("%6d bytes total", total);
1555 }
1556 
1557 int  klassItable::_total_classes;   // Total no. of classes with itables
1558 long klassItable::_total_size;      // Total no. of bytes used for itables
1559 
1560 void klassItable::print_statistics() {
1561  tty->print_cr("itable statistics:");
1562  tty->print_cr("%6d classes with itables", _total_classes);
1563  tty->print_cr("%6d K uses for itables (average by class: %d bytes)", _total_size / K, _total_size / _total_classes);
1564 }
1565 
1566 #endif // PRODUCT