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Java example source code file (klassVtable.cpp)

This example Java source code file (klassVtable.cpp) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

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Java - Java tags/keywords

array, check, handle, instanceklass, instanceklass\:\:cast, method, null, printvtables, product, resourcemark, symbol, thread, traps, verbose

The klassVtable.cpp Java example source code

/*
 * Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 *
 */

#include "precompiled.hpp"
#include "classfile/systemDictionary.hpp"
#include "classfile/vmSymbols.hpp"
#include "gc_implementation/shared/markSweep.inline.hpp"
#include "memory/gcLocker.hpp"
#include "memory/resourceArea.hpp"
#include "memory/universe.inline.hpp"
#include "oops/instanceKlass.hpp"
#include "oops/klassVtable.hpp"
#include "oops/method.hpp"
#include "oops/objArrayOop.hpp"
#include "oops/oop.inline.hpp"
#include "prims/jvmtiRedefineClassesTrace.hpp"
#include "runtime/arguments.hpp"
#include "runtime/handles.inline.hpp"
#include "utilities/copy.hpp"

inline InstanceKlass* klassVtable::ik() const {
  Klass* k = _klass();
  assert(k->oop_is_instance(), "not an InstanceKlass");
  return (InstanceKlass*)k;
}


// this function computes the vtable size (including the size needed for miranda
// methods) and the number of miranda methods in this class.
// Note on Miranda methods: Let's say there is a class C that implements
// interface I, and none of C's superclasses implements I.
// Let's say there is an abstract method m in I that neither C
// nor any of its super classes implement (i.e there is no method of any access,
// with the same name and signature as m), then m is a Miranda method which is
// entered as a public abstract method in C's vtable.  From then on it should
// treated as any other public method in C for method over-ride purposes.
void klassVtable::compute_vtable_size_and_num_mirandas(
    int* vtable_length_ret, int* num_new_mirandas,
    GrowableArray<Method*>* all_mirandas, Klass* super,
    Array<Method*>* methods, AccessFlags class_flags,
    Handle classloader, Symbol* classname, Array<Klass*>* local_interfaces,
    TRAPS) {
  No_Safepoint_Verifier nsv;

  // set up default result values
  int vtable_length = 0;

  // start off with super's vtable length
  InstanceKlass* sk = (InstanceKlass*)super;
  vtable_length = super == NULL ? 0 : sk->vtable_length();

  // go thru each method in the methods table to see if it needs a new entry
  int len = methods->length();
  for (int i = 0; i < len; i++) {
    assert(methods->at(i)->is_method(), "must be a Method*");
    methodHandle mh(THREAD, methods->at(i));

    if (needs_new_vtable_entry(mh, super, classloader, classname, class_flags, THREAD)) {
      vtable_length += vtableEntry::size(); // we need a new entry
    }
  }

  GrowableArray<Method*> new_mirandas(20);
  // compute the number of mirandas methods that must be added to the end
  get_mirandas(&new_mirandas, all_mirandas, super, methods, NULL, local_interfaces);
  *num_new_mirandas = new_mirandas.length();

  // Interfaces do not need interface methods in their vtables
  // This includes miranda methods and during later processing, default methods
  if (!class_flags.is_interface()) {
    vtable_length += *num_new_mirandas * vtableEntry::size();
  }

  if (Universe::is_bootstrapping() && vtable_length == 0) {
    // array classes don't have their superclass set correctly during
    // bootstrapping
    vtable_length = Universe::base_vtable_size();
  }

  if (super == NULL && !Universe::is_bootstrapping() &&
      vtable_length != Universe::base_vtable_size()) {
    // Someone is attempting to redefine java.lang.Object incorrectly.  The
    // only way this should happen is from
    // SystemDictionary::resolve_from_stream(), which will detect this later
    // and throw a security exception.  So don't assert here to let
    // the exception occur.
    vtable_length = Universe::base_vtable_size();
  }
  assert(super != NULL || vtable_length == Universe::base_vtable_size(),
         "bad vtable size for class Object");
  assert(vtable_length % vtableEntry::size() == 0, "bad vtable length");
  assert(vtable_length >= Universe::base_vtable_size(), "vtable too small");

  *vtable_length_ret = vtable_length;
}

int klassVtable::index_of(Method* m, int len) const {
  assert(m->has_vtable_index(), "do not ask this of non-vtable methods");
  return m->vtable_index();
}

// Copy super class's vtable to the first part (prefix) of this class's vtable,
// and return the number of entries copied.  Expects that 'super' is the Java
// super class (arrays can have "array" super classes that must be skipped).
int klassVtable::initialize_from_super(KlassHandle super) {
  if (super.is_null()) {
    return 0;
  } else {
    // copy methods from superKlass
    // can't inherit from array class, so must be InstanceKlass
    assert(super->oop_is_instance(), "must be instance klass");
    InstanceKlass* sk = (InstanceKlass*)super();
    klassVtable* superVtable = sk->vtable();
    assert(superVtable->length() <= _length, "vtable too short");
#ifdef ASSERT
    superVtable->verify(tty, true);
#endif
    superVtable->copy_vtable_to(table());
#ifndef PRODUCT
    if (PrintVtables && Verbose) {
      ResourceMark rm;
      tty->print_cr("copy vtable from %s to %s size %d", sk->internal_name(), klass()->internal_name(), _length);
    }
#endif
    return superVtable->length();
  }
}

//
// Revised lookup semantics   introduced 1.3 (Kestrel beta)
void klassVtable::initialize_vtable(bool checkconstraints, TRAPS) {

  // Note:  Arrays can have intermediate array supers.  Use java_super to skip them.
  KlassHandle super (THREAD, klass()->java_super());
  int nofNewEntries = 0;

  if (PrintVtables && !klass()->oop_is_array()) {
    ResourceMark rm(THREAD);
    tty->print_cr("Initializing: %s", _klass->name()->as_C_string());
  }

#ifdef ASSERT
  oop* end_of_obj = (oop*)_klass() + _klass()->size();
  oop* end_of_vtable = (oop*)&table()[_length];
  assert(end_of_vtable <= end_of_obj, "vtable extends beyond end");
#endif

  if (Universe::is_bootstrapping()) {
    // just clear everything
    for (int i = 0; i < _length; i++) table()[i].clear();
    return;
  }

  int super_vtable_len = initialize_from_super(super);
  if (klass()->oop_is_array()) {
    assert(super_vtable_len == _length, "arrays shouldn't introduce new methods");
  } else {
    assert(_klass->oop_is_instance(), "must be InstanceKlass");

    Array<Method*>* methods = ik()->methods();
    int len = methods->length();
    int initialized = super_vtable_len;

    // Check each of this class's methods against super;
    // if override, replace in copy of super vtable, otherwise append to end
    for (int i = 0; i < len; i++) {
      // update_inherited_vtable can stop for gc - ensure using handles
      HandleMark hm(THREAD);
      assert(methods->at(i)->is_method(), "must be a Method*");
      methodHandle mh(THREAD, methods->at(i));

      bool needs_new_entry = update_inherited_vtable(ik(), mh, super_vtable_len, -1, checkconstraints, CHECK);

      if (needs_new_entry) {
        put_method_at(mh(), initialized);
        mh()->set_vtable_index(initialized); // set primary vtable index
        initialized++;
      }
    }

    // update vtable with default_methods
    Array<Method*>* default_methods = ik()->default_methods();
    if (default_methods != NULL) {
      len = default_methods->length();
      if (len > 0) {
        Array<int>* def_vtable_indices = NULL;
        if ((def_vtable_indices = ik()->default_vtable_indices()) == NULL) {
          def_vtable_indices = ik()->create_new_default_vtable_indices(len, CHECK);
        } else {
          assert(def_vtable_indices->length() == len, "reinit vtable len?");
        }
        for (int i = 0; i < len; i++) {
          HandleMark hm(THREAD);
          assert(default_methods->at(i)->is_method(), "must be a Method*");
          methodHandle mh(THREAD, default_methods->at(i));

          bool needs_new_entry = update_inherited_vtable(ik(), mh, super_vtable_len, i, checkconstraints, CHECK);

          // needs new entry
          if (needs_new_entry) {
            put_method_at(mh(), initialized);
            def_vtable_indices->at_put(i, initialized); //set vtable index
            initialized++;
          }
        }
      }
    }

    // add miranda methods; it will also return the updated initialized
    // Interfaces do not need interface methods in their vtables
    // This includes miranda methods and during later processing, default methods
    if (!ik()->is_interface()) {
      initialized = fill_in_mirandas(initialized);
    }

    // In class hierarchies where the accessibility is not increasing (i.e., going from private ->
    // package_private -> public/protected), the vtable might actually be smaller than our initial
    // calculation.
    assert(initialized <= _length, "vtable initialization failed");
    for(;initialized < _length; initialized++) {
      put_method_at(NULL, initialized);
    }
    NOT_PRODUCT(verify(tty, true));
  }
}

// Called for cases where a method does not override its superclass' vtable entry
// For bytecodes not produced by javac together it is possible that a method does not override
// the superclass's method, but might indirectly override a super-super class's vtable entry
// If none found, return a null superk, else return the superk of the method this does override
InstanceKlass* klassVtable::find_transitive_override(InstanceKlass* initialsuper, methodHandle target_method,
                            int vtable_index, Handle target_loader, Symbol* target_classname, Thread * THREAD) {
  InstanceKlass* superk = initialsuper;
  while (superk != NULL && superk->super() != NULL) {
    InstanceKlass* supersuperklass = InstanceKlass::cast(superk->super());
    klassVtable* ssVtable = supersuperklass->vtable();
    if (vtable_index < ssVtable->length()) {
      Method* super_method = ssVtable->method_at(vtable_index);
#ifndef PRODUCT
      Symbol* name= target_method()->name();
      Symbol* signature = target_method()->signature();
      assert(super_method->name() == name && super_method->signature() == signature, "vtable entry name/sig mismatch");
#endif
      if (supersuperklass->is_override(super_method, target_loader, target_classname, THREAD)) {
#ifndef PRODUCT
        if (PrintVtables && Verbose) {
          ResourceMark rm(THREAD);
          char* sig = target_method()->name_and_sig_as_C_string();
          tty->print("transitive overriding superclass %s with %s::%s index %d, original flags: ",
           supersuperklass->internal_name(),
           _klass->internal_name(), sig, vtable_index);
           super_method->access_flags().print_on(tty);
           if (super_method->is_default_method()) {
             tty->print("default ");
           }
           tty->print("overriders flags: ");
           target_method->access_flags().print_on(tty);
           if (target_method->is_default_method()) {
             tty->print("default ");
           }
        }
#endif /*PRODUCT*/
        break; // return found superk
      }
    } else  {
      // super class has no vtable entry here, stop transitive search
      superk = (InstanceKlass*)NULL;
      break;
    }
    // if no override found yet, continue to search up
    superk = InstanceKlass::cast(superk->super());
  }

  return superk;
}

// Update child's copy of super vtable for overrides
// OR return true if a new vtable entry is required.
// Only called for InstanceKlass's, i.e. not for arrays
// If that changed, could not use _klass as handle for klass
bool klassVtable::update_inherited_vtable(InstanceKlass* klass, methodHandle target_method,
                                          int super_vtable_len, int default_index,
                                          bool checkconstraints, TRAPS) {
  ResourceMark rm;
  bool allocate_new = true;
  assert(klass->oop_is_instance(), "must be InstanceKlass");

  Array<int>* def_vtable_indices = NULL;
  bool is_default = false;
  // default methods are concrete methods in superinterfaces which are added to the vtable
  // with their real method_holder
  // Since vtable and itable indices share the same storage, don't touch
  // the default method's real vtable/itable index
  // default_vtable_indices stores the vtable value relative to this inheritor
  if (default_index >= 0 ) {
    is_default = true;
    def_vtable_indices = klass->default_vtable_indices();
    assert(def_vtable_indices != NULL, "def vtable alloc?");
    assert(default_index <= def_vtable_indices->length(), "def vtable len?");
  } else {
    assert(klass == target_method()->method_holder(), "caller resp.");
    // Initialize the method's vtable index to "nonvirtual".
    // If we allocate a vtable entry, we will update it to a non-negative number.
    target_method()->set_vtable_index(Method::nonvirtual_vtable_index);
  }

  // Static and <init> methods are never in
  if (target_method()->is_static() || target_method()->name() ==  vmSymbols::object_initializer_name()) {
    return false;
  }

  if (target_method->is_final_method(klass->access_flags())) {
    // a final method never needs a new entry; final methods can be statically
    // resolved and they have to be present in the vtable only if they override
    // a super's method, in which case they re-use its entry
    allocate_new = false;
  } else if (klass->is_interface()) {
    allocate_new = false;  // see note below in needs_new_vtable_entry
    // An interface never allocates new vtable slots, only inherits old ones.
    // This method will either be assigned its own itable index later,
    // or be assigned an inherited vtable index in the loop below.
    // default methods inherited by classes store their vtable indices
    // in the inheritor's default_vtable_indices
    // default methods inherited by interfaces may already have a
    // valid itable index, if so, don't change it
    // overpass methods in an interface will be assigned an itable index later
    // by an inheriting class
    if (!is_default || !target_method()->has_itable_index()) {
      target_method()->set_vtable_index(Method::pending_itable_index);
    }
  }

  // we need a new entry if there is no superclass
  if (klass->super() == NULL) {
    return allocate_new;
  }

  // private methods in classes always have a new entry in the vtable
  // specification interpretation since classic has
  // private methods not overriding
  // JDK8 adds private methods in interfaces which require invokespecial
  if (target_method()->is_private()) {
    return allocate_new;
  }

  // search through the vtable and update overridden entries
  // Since check_signature_loaders acquires SystemDictionary_lock
  // which can block for gc, once we are in this loop, use handles
  // For classfiles built with >= jdk7, we now look for transitive overrides

  Symbol* name = target_method()->name();
  Symbol* signature = target_method()->signature();

  KlassHandle target_klass(THREAD, target_method()->method_holder());
  if (target_klass == NULL) {
    target_klass = _klass;
  }

  Handle target_loader(THREAD, target_klass->class_loader());

  Symbol* target_classname = target_klass->name();
  for(int i = 0; i < super_vtable_len; i++) {
    Method* super_method = method_at(i);
    // Check if method name matches
    if (super_method->name() == name && super_method->signature() == signature) {

      // get super_klass for method_holder for the found method
      InstanceKlass* super_klass =  super_method->method_holder();

      if (is_default
          || ((super_klass->is_override(super_method, target_loader, target_classname, THREAD))
          || ((klass->major_version() >= VTABLE_TRANSITIVE_OVERRIDE_VERSION)
          && ((super_klass = find_transitive_override(super_klass,
                             target_method, i, target_loader,
                             target_classname, THREAD))
                             != (InstanceKlass*)NULL))))
        {
        // overriding, so no new entry
        allocate_new = false;

        if (checkconstraints) {
        // Override vtable entry if passes loader constraint check
        // if loader constraint checking requested
        // No need to visit his super, since he and his super
        // have already made any needed loader constraints.
        // Since loader constraints are transitive, it is enough
        // to link to the first super, and we get all the others.
          Handle super_loader(THREAD, super_klass->class_loader());

          if (target_loader() != super_loader()) {
            ResourceMark rm(THREAD);
            Symbol* failed_type_symbol =
              SystemDictionary::check_signature_loaders(signature, target_loader,
                                                        super_loader, true,
                                                        CHECK_(false));
            if (failed_type_symbol != NULL) {
              const char* msg = "loader constraint violation: when resolving "
                "overridden method \"%s\" the class loader (instance"
                " of %s) of the current class, %s, and its superclass loader "
                "(instance of %s), have different Class objects for the type "
                "%s used in the signature";
              char* sig = target_method()->name_and_sig_as_C_string();
              const char* loader1 = SystemDictionary::loader_name(target_loader());
              char* current = target_klass->name()->as_C_string();
              const char* loader2 = SystemDictionary::loader_name(super_loader());
              char* failed_type_name = failed_type_symbol->as_C_string();
              size_t buflen = strlen(msg) + strlen(sig) + strlen(loader1) +
                strlen(current) + strlen(loader2) + strlen(failed_type_name);
              char* buf = NEW_RESOURCE_ARRAY_IN_THREAD(THREAD, char, buflen);
              jio_snprintf(buf, buflen, msg, sig, loader1, current, loader2,
                           failed_type_name);
              THROW_MSG_(vmSymbols::java_lang_LinkageError(), buf, false);
            }
          }
       }

       put_method_at(target_method(), i);
       if (!is_default) {
         target_method()->set_vtable_index(i);
       } else {
         if (def_vtable_indices != NULL) {
           def_vtable_indices->at_put(default_index, i);
         }
         assert(super_method->is_default_method() || super_method->is_overpass()
                || super_method->is_abstract(), "default override error");
       }


#ifndef PRODUCT
        if (PrintVtables && Verbose) {
          ResourceMark rm(THREAD);
          char* sig = target_method()->name_and_sig_as_C_string();
          tty->print("overriding with %s::%s index %d, original flags: ",
           target_klass->internal_name(), sig, i);
           super_method->access_flags().print_on(tty);
           if (super_method->is_default_method()) {
             tty->print("default ");
           }
           if (super_method->is_overpass()) {
             tty->print("overpass");
           }
           tty->print("overriders flags: ");
           target_method->access_flags().print_on(tty);
           if (target_method->is_default_method()) {
             tty->print("default ");
           }
           if (target_method->is_overpass()) {
             tty->print("overpass");
           }
           tty->cr();
        }
#endif /*PRODUCT*/
      } else {
        // allocate_new = true; default. We might override one entry,
        // but not override another. Once we override one, not need new
#ifndef PRODUCT
        if (PrintVtables && Verbose) {
          ResourceMark rm(THREAD);
          char* sig = target_method()->name_and_sig_as_C_string();
          tty->print("NOT overriding with %s::%s index %d, original flags: ",
           target_klass->internal_name(), sig,i);
           super_method->access_flags().print_on(tty);
           if (super_method->is_default_method()) {
             tty->print("default ");
           }
           if (super_method->is_overpass()) {
             tty->print("overpass");
           }
           tty->print("overriders flags: ");
           target_method->access_flags().print_on(tty);
           if (target_method->is_default_method()) {
             tty->print("default ");
           }
           if (target_method->is_overpass()) {
             tty->print("overpass");
           }
           tty->cr();
        }
#endif /*PRODUCT*/
      }
    }
  }
  return allocate_new;
}

void klassVtable::put_method_at(Method* m, int index) {
#ifndef PRODUCT
  if (PrintVtables && Verbose) {
    ResourceMark rm;
    const char* sig = (m != NULL) ? m->name_and_sig_as_C_string() : "<NULL>";
    tty->print("adding %s at index %d, flags: ", sig, index);
    if (m != NULL) {
      m->access_flags().print_on(tty);
      if (m->is_default_method()) {
        tty->print("default ");
      }
      if (m->is_overpass()) {
        tty->print("overpass");
      }
    }
    tty->cr();
  }
#endif
  table()[index].set(m);
}

// Find out if a method "m" with superclass "super", loader "classloader" and
// name "classname" needs a new vtable entry.  Let P be a class package defined
// by "classloader" and "classname".
// NOTE: The logic used here is very similar to the one used for computing
// the vtables indices for a method. We cannot directly use that function because,
// we allocate the InstanceKlass at load time, and that requires that the
// superclass has been loaded.
// However, the vtable entries are filled in at link time, and therefore
// the superclass' vtable may not yet have been filled in.
bool klassVtable::needs_new_vtable_entry(methodHandle target_method,
                                         Klass* super,
                                         Handle classloader,
                                         Symbol* classname,
                                         AccessFlags class_flags,
                                         TRAPS) {
  if (class_flags.is_interface()) {
    // Interfaces do not use vtables, so there is no point to assigning
    // a vtable index to any of their methods.  If we refrain from doing this,
    // we can use Method::_vtable_index to hold the itable index
    return false;
  }

  if (target_method->is_final_method(class_flags) ||
      // a final method never needs a new entry; final methods can be statically
      // resolved and they have to be present in the vtable only if they override
      // a super's method, in which case they re-use its entry
      (target_method()->is_static()) ||
      // static methods don't need to be in vtable
      (target_method()->name() ==  vmSymbols::object_initializer_name())
      // <init> is never called dynamically-bound
      ) {
    return false;
  }

  // Concrete interface methods do not need new entries, they override
  // abstract method entries using default inheritance rules
  if (target_method()->method_holder() != NULL &&
      target_method()->method_holder()->is_interface()  &&
      !target_method()->is_abstract() ) {
    return false;
  }

  // we need a new entry if there is no superclass
  if (super == NULL) {
    return true;
  }

  // private methods in classes always have a new entry in the vtable
  // specification interpretation since classic has
  // private methods not overriding
  // JDK8 adds private  methods in interfaces which require invokespecial
  if (target_method()->is_private()) {
    return true;
  }

  // search through the super class hierarchy to see if we need
  // a new entry
  ResourceMark rm;
  Symbol* name = target_method()->name();
  Symbol* signature = target_method()->signature();
  Klass* k = super;
  Method* super_method = NULL;
  InstanceKlass *holder = NULL;
  Method* recheck_method =  NULL;
  while (k != NULL) {
    // lookup through the hierarchy for a method with matching name and sign.
    super_method = InstanceKlass::cast(k)->lookup_method(name, signature);
    if (super_method == NULL) {
      break; // we still have to search for a matching miranda method
    }
    // get the class holding the matching method
    // make sure you use that class for is_override
    InstanceKlass* superk = super_method->method_holder();
    // we want only instance method matches
    // pretend private methods are not in the super vtable
    // since we do override around them: e.g. a.m pub/b.m private/c.m pub,
    // ignore private, c.m pub does override a.m pub
    // For classes that were not javac'd together, we also do transitive overriding around
    // methods that have less accessibility
    if ((!super_method->is_static()) &&
       (!super_method->is_private())) {
      if (superk->is_override(super_method, classloader, classname, THREAD)) {
        return false;
      // else keep looking for transitive overrides
      }
    }

    // Start with lookup result and continue to search up
    k = superk->super(); // haven't found an override match yet; continue to look
  }

  // if the target method is public or protected it may have a matching
  // miranda method in the super, whose entry it should re-use.
  // Actually, to handle cases that javac would not generate, we need
  // this check for all access permissions.
  InstanceKlass *sk = InstanceKlass::cast(super);
  if (sk->has_miranda_methods()) {
    if (sk->lookup_method_in_all_interfaces(name, signature, false) != NULL) {
      return false;  // found a matching miranda; we do not need a new entry
    }
  }
  return true; // found no match; we need a new entry
}

// Support for miranda methods

// get the vtable index of a miranda method with matching "name" and "signature"
int klassVtable::index_of_miranda(Symbol* name, Symbol* signature) {
  // search from the bottom, might be faster
  for (int i = (length() - 1); i >= 0; i--) {
    Method* m = table()[i].method();
    if (is_miranda_entry_at(i) &&
        m->name() == name && m->signature() == signature) {
      return i;
    }
  }
  return Method::invalid_vtable_index;
}

// check if an entry at an index is miranda
// requires that method m at entry be declared ("held") by an interface.
bool klassVtable::is_miranda_entry_at(int i) {
  Method* m = method_at(i);
  Klass* method_holder = m->method_holder();
  InstanceKlass *mhk = InstanceKlass::cast(method_holder);

  // miranda methods are public abstract instance interface methods in a class's vtable
  if (mhk->is_interface()) {
    assert(m->is_public(), "should be public");
    assert(ik()->implements_interface(method_holder) , "this class should implement the interface");
    // the search could find a miranda or a default method
    if (is_miranda(m, ik()->methods(), ik()->default_methods(), ik()->super())) {
      return true;
    }
  }
  return false;
}

// check if a method is a miranda method, given a class's methods table,
// its default_method table  and its super
// Miranda methods are calculated twice:
// first: before vtable size calculation: including abstract and default
// This is seen by default method creation
// Second: recalculated during vtable initialization: only abstract
// This is seen by link resolution and selection.
// "miranda" means not static, not defined by this class.
// private methods in interfaces do not belong in the miranda list.
// the caller must make sure that the method belongs to an interface implemented by the class
// Miranda methods only include public interface instance methods
// Not private methods, not static methods, not default == concrete abstract
// Miranda methods also do not include overpass methods in interfaces
bool klassVtable::is_miranda(Method* m, Array<Method*>* class_methods,
                             Array<Method*>* default_methods, Klass* super) {
  if (m->is_static() || m->is_private() || m->is_overpass()) {
    return false;
  }
  Symbol* name = m->name();
  Symbol* signature = m->signature();

  if (InstanceKlass::find_instance_method(class_methods, name, signature) == NULL) {
    // did not find it in the method table of the current class
    if ((default_methods == NULL) ||
        InstanceKlass::find_method(default_methods, name, signature) == NULL) {
      if (super == NULL) {
        // super doesn't exist
        return true;
      }

      Method* mo = InstanceKlass::cast(super)->lookup_method(name, signature);
      while (mo != NULL && mo->access_flags().is_static()
             && mo->method_holder() != NULL
             && mo->method_holder()->super() != NULL)
      {
         mo = mo->method_holder()->super()->uncached_lookup_method(name, signature);
      }
      if (mo == NULL || mo->access_flags().is_private() ) {
        // super class hierarchy does not implement it or protection is different
        return true;
      }
    }
  }

  return false;
}

// Scans current_interface_methods for miranda methods that do not
// already appear in new_mirandas, or default methods,  and are also not defined-and-non-private
// in super (superclass).  These mirandas are added to all_mirandas if it is
// not null; in addition, those that are not duplicates of miranda methods
// inherited by super from its interfaces are added to new_mirandas.
// Thus, new_mirandas will be the set of mirandas that this class introduces,
// all_mirandas will be the set of all mirandas applicable to this class
// including all defined in superclasses.
void klassVtable::add_new_mirandas_to_lists(
    GrowableArray<Method*>* new_mirandas, GrowableArray* all_mirandas,
    Array<Method*>* current_interface_methods, Array* class_methods,
    Array<Method*>* default_methods, Klass* super) {

  // iterate thru the current interface's method to see if it a miranda
  int num_methods = current_interface_methods->length();
  for (int i = 0; i < num_methods; i++) {
    Method* im = current_interface_methods->at(i);
    bool is_duplicate = false;
    int num_of_current_mirandas = new_mirandas->length();
    // check for duplicate mirandas in different interfaces we implement
    for (int j = 0; j < num_of_current_mirandas; j++) {
      Method* miranda = new_mirandas->at(j);
      if ((im->name() == miranda->name()) &&
          (im->signature() == miranda->signature())) {
        is_duplicate = true;
        break;
      }
    }

    if (!is_duplicate) { // we don't want duplicate miranda entries in the vtable
      if (is_miranda(im, class_methods, default_methods, super)) { // is it a miranda at all?
        InstanceKlass *sk = InstanceKlass::cast(super);
        // check if it is a duplicate of a super's miranda
        if (sk->lookup_method_in_all_interfaces(im->name(), im->signature(), false) == NULL) {
          new_mirandas->append(im);
        }
        if (all_mirandas != NULL) {
          all_mirandas->append(im);
        }
      }
    }
  }
}

void klassVtable::get_mirandas(GrowableArray<Method*>* new_mirandas,
                               GrowableArray<Method*>* all_mirandas,
                               Klass* super, Array<Method*>* class_methods,
                               Array<Method*>* default_methods,
                               Array<Klass*>* local_interfaces) {
  assert((new_mirandas->length() == 0) , "current mirandas must be 0");

  // iterate thru the local interfaces looking for a miranda
  int num_local_ifs = local_interfaces->length();
  for (int i = 0; i < num_local_ifs; i++) {
    InstanceKlass *ik = InstanceKlass::cast(local_interfaces->at(i));
    add_new_mirandas_to_lists(new_mirandas, all_mirandas,
                              ik->methods(), class_methods,
                              default_methods, super);
    // iterate thru each local's super interfaces
    Array<Klass*>* super_ifs = ik->transitive_interfaces();
    int num_super_ifs = super_ifs->length();
    for (int j = 0; j < num_super_ifs; j++) {
      InstanceKlass *sik = InstanceKlass::cast(super_ifs->at(j));
      add_new_mirandas_to_lists(new_mirandas, all_mirandas,
                                sik->methods(), class_methods,
                                default_methods, super);
    }
  }
}

// Discover miranda methods ("miranda" = "interface abstract, no binding"),
// and append them into the vtable starting at index initialized,
// return the new value of initialized.
// Miranda methods use vtable entries, but do not get assigned a vtable_index
// The vtable_index is discovered by searching from the end of the vtable
int klassVtable::fill_in_mirandas(int initialized) {
  GrowableArray<Method*> mirandas(20);
  get_mirandas(&mirandas, NULL, ik()->super(), ik()->methods(),
               ik()->default_methods(), ik()->local_interfaces());
  for (int i = 0; i < mirandas.length(); i++) {
    if (PrintVtables && Verbose) {
      Method* meth = mirandas.at(i);
      ResourceMark rm(Thread::current());
      if (meth != NULL) {
        char* sig = meth->name_and_sig_as_C_string();
        tty->print("fill in mirandas with %s index %d, flags: ",
          sig, initialized);
        meth->access_flags().print_on(tty);
        if (meth->is_default_method()) {
          tty->print("default ");
        }
        tty->cr();
      }
    }
    put_method_at(mirandas.at(i), initialized);
    ++initialized;
  }
  return initialized;
}

// Copy this class's vtable to the vtable beginning at start.
// Used to copy superclass vtable to prefix of subclass's vtable.
void klassVtable::copy_vtable_to(vtableEntry* start) {
  Copy::disjoint_words((HeapWord*)table(), (HeapWord*)start, _length * vtableEntry::size());
}

#if INCLUDE_JVMTI
bool klassVtable::adjust_default_method(int vtable_index, Method* old_method, Method* new_method) {
  // If old_method is default, find this vtable index in default_vtable_indices
  // and replace that method in the _default_methods list
  bool updated = false;

  Array<Method*>* default_methods = ik()->default_methods();
  if (default_methods != NULL) {
    int len = default_methods->length();
    for (int idx = 0; idx < len; idx++) {
      if (vtable_index == ik()->default_vtable_indices()->at(idx)) {
        if (default_methods->at(idx) == old_method) {
          default_methods->at_put(idx, new_method);
          updated = true;
        }
        break;
      }
    }
  }
  return updated;
}
void klassVtable::adjust_method_entries(Method** old_methods, Method** new_methods,
                                        int methods_length, bool * trace_name_printed) {
  // search the vtable for uses of either obsolete or EMCP methods
  for (int j = 0; j < methods_length; j++) {
    Method* old_method = old_methods[j];
    Method* new_method = new_methods[j];

    // In the vast majority of cases we could get the vtable index
    // by using:  old_method->vtable_index()
    // However, there are rare cases, eg. sun.awt.X11.XDecoratedPeer.getX()
    // in sun.awt.X11.XFramePeer where methods occur more than once in the
    // vtable, so, alas, we must do an exhaustive search.
    for (int index = 0; index < length(); index++) {
      if (unchecked_method_at(index) == old_method) {
        put_method_at(new_method, index);
          // For default methods, need to update the _default_methods array
          // which can only have one method entry for a given signature
          bool updated_default = false;
          if (old_method->is_default_method()) {
            updated_default = adjust_default_method(index, old_method, new_method);
          }

        if (RC_TRACE_IN_RANGE(0x00100000, 0x00400000)) {
          if (!(*trace_name_printed)) {
            // RC_TRACE_MESG macro has an embedded ResourceMark
            RC_TRACE_MESG(("adjust: klassname=%s for methods from name=%s",
                           klass()->external_name(),
                           old_method->method_holder()->external_name()));
            *trace_name_printed = true;
          }
          // RC_TRACE macro has an embedded ResourceMark
          RC_TRACE(0x00100000, ("vtable method update: %s(%s), updated default = %s",
                                new_method->name()->as_C_string(),
                                new_method->signature()->as_C_string(),
                                updated_default ? "true" : "false"));
        }
        // cannot 'break' here; see for-loop comment above.
      }
    }
  }
}

// a vtable should never contain old or obsolete methods
bool klassVtable::check_no_old_or_obsolete_entries() {
  for (int i = 0; i < length(); i++) {
    Method* m = unchecked_method_at(i);
    if (m != NULL &&
        (NOT_PRODUCT(!m->is_valid() ||) m->is_old() || m->is_obsolete())) {
      return false;
    }
  }
  return true;
}

void klassVtable::dump_vtable() {
  tty->print_cr("vtable dump --");
  for (int i = 0; i < length(); i++) {
    Method* m = unchecked_method_at(i);
    if (m != NULL) {
      tty->print("      (%5d)  ", i);
      m->access_flags().print_on(tty);
      if (m->is_default_method()) {
        tty->print("default ");
      }
      if (m->is_overpass()) {
        tty->print("overpass");
      }
      tty->print(" --  ");
      m->print_name(tty);
      tty->cr();
    }
  }
}
#endif // INCLUDE_JVMTI

// CDS/RedefineClasses support - clear vtables so they can be reinitialized
void klassVtable::clear_vtable() {
  for (int i = 0; i < _length; i++) table()[i].clear();
}

bool klassVtable::is_initialized() {
  return _length == 0 || table()[0].method() != NULL;
}

//-----------------------------------------------------------------------------------------
// Itable code

// Initialize a itableMethodEntry
void itableMethodEntry::initialize(Method* m) {
  if (m == NULL) return;

  _method = m;
}

klassItable::klassItable(instanceKlassHandle klass) {
  _klass = klass;

  if (klass->itable_length() > 0) {
    itableOffsetEntry* offset_entry = (itableOffsetEntry*)klass->start_of_itable();
    if (offset_entry  != NULL && offset_entry->interface_klass() != NULL) { // Check that itable is initialized
      // First offset entry points to the first method_entry
      intptr_t* method_entry  = (intptr_t *)(((address)klass()) + offset_entry->offset());
      intptr_t* end         = klass->end_of_itable();

      _table_offset      = (intptr_t*)offset_entry - (intptr_t*)klass();
      _size_offset_table = (method_entry - ((intptr_t*)offset_entry)) / itableOffsetEntry::size();
      _size_method_table = (end - method_entry)                  / itableMethodEntry::size();
      assert(_table_offset >= 0 && _size_offset_table >= 0 && _size_method_table >= 0, "wrong computation");
      return;
    }
  }

  // The length of the itable was either zero, or it has not yet been initialized.
  _table_offset      = 0;
  _size_offset_table = 0;
  _size_method_table = 0;
}

static int initialize_count = 0;

// Initialization
void klassItable::initialize_itable(bool checkconstraints, TRAPS) {
  if (_klass->is_interface()) {
    // This needs to go after vtable indices are assigned but
    // before implementors need to know the number of itable indices.
    assign_itable_indices_for_interface(_klass());
  }

  // Cannot be setup doing bootstrapping, interfaces don't have
  // itables, and klass with only ones entry have empty itables
  if (Universe::is_bootstrapping() ||
      _klass->is_interface() ||
      _klass->itable_length() == itableOffsetEntry::size()) return;

  // There's alway an extra itable entry so we can null-terminate it.
  guarantee(size_offset_table() >= 1, "too small");
  int num_interfaces = size_offset_table() - 1;
  if (num_interfaces > 0) {
    if (TraceItables) tty->print_cr("%3d: Initializing itables for %s", ++initialize_count,
                                    _klass->name()->as_C_string());


    // Iterate through all interfaces
    int i;
    for(i = 0; i < num_interfaces; i++) {
      itableOffsetEntry* ioe = offset_entry(i);
      HandleMark hm(THREAD);
      KlassHandle interf_h (THREAD, ioe->interface_klass());
      assert(interf_h() != NULL && ioe->offset() != 0, "bad offset entry in itable");
      initialize_itable_for_interface(ioe->offset(), interf_h, checkconstraints, CHECK);
    }

  }
  // Check that the last entry is empty
  itableOffsetEntry* ioe = offset_entry(size_offset_table() - 1);
  guarantee(ioe->interface_klass() == NULL && ioe->offset() == 0, "terminator entry missing");
}


inline bool interface_method_needs_itable_index(Method* m) {
  if (m->is_static())           return false;   // e.g., Stream.empty
  if (m->is_initializer())      return false;   // <init> or 
  // If an interface redeclares a method from java.lang.Object,
  // it should already have a vtable index, don't touch it.
  // e.g., CharSequence.toString (from initialize_vtable)
  // if (m->has_vtable_index())  return false; // NO!
  return true;
}

int klassItable::assign_itable_indices_for_interface(Klass* klass) {
  // an interface does not have an itable, but its methods need to be numbered
  if (TraceItables) tty->print_cr("%3d: Initializing itable for interface %s", ++initialize_count,
                                  klass->name()->as_C_string());
  Array<Method*>* methods = InstanceKlass::cast(klass)->methods();
  int nof_methods = methods->length();
  int ime_num = 0;
  for (int i = 0; i < nof_methods; i++) {
    Method* m = methods->at(i);
    if (interface_method_needs_itable_index(m)) {
      assert(!m->is_final_method(), "no final interface methods");
      // If m is already assigned a vtable index, do not disturb it.
      if (TraceItables && Verbose) {
        ResourceMark rm;
        const char* sig = (m != NULL) ? m->name_and_sig_as_C_string() : "<NULL>";
        if (m->has_vtable_index()) {
          tty->print("itable index %d for method: %s, flags: ", m->vtable_index(), sig);
        } else {
          tty->print("itable index %d for method: %s, flags: ", ime_num, sig);
        }
        if (m != NULL) {
          m->access_flags().print_on(tty);
          if (m->is_default_method()) {
            tty->print("default ");
          }
          if (m->is_overpass()) {
            tty->print("overpass");
          }
        }
        tty->cr();
      }
      if (!m->has_vtable_index()) {
        assert(m->vtable_index() == Method::pending_itable_index, "set by initialize_vtable");
        m->set_itable_index(ime_num);
        // Progress to next itable entry
        ime_num++;
      }
    }
  }
  assert(ime_num == method_count_for_interface(klass), "proper sizing");
  return ime_num;
}

int klassItable::method_count_for_interface(Klass* interf) {
  assert(interf->oop_is_instance(), "must be");
  assert(interf->is_interface(), "must be");
  Array<Method*>* methods = InstanceKlass::cast(interf)->methods();
  int nof_methods = methods->length();
  while (nof_methods > 0) {
    Method* m = methods->at(nof_methods-1);
    if (m->has_itable_index()) {
      int length = m->itable_index() + 1;
#ifdef ASSERT
      while (nof_methods = 0) {
        m = methods->at(--nof_methods);
        assert(!m->has_itable_index() || m->itable_index() < length, "");
      }
#endif //ASSERT
      return length;  // return the rightmost itable index, plus one
    }
    nof_methods -= 1;
  }
  // no methods have itable indices
  return 0;
}


void klassItable::initialize_itable_for_interface(int method_table_offset, KlassHandle interf_h, bool checkconstraints, TRAPS) {
  Array<Method*>* methods = InstanceKlass::cast(interf_h())->methods();
  int nof_methods = methods->length();
  HandleMark hm;
  assert(nof_methods > 0, "at least one method must exist for interface to be in vtable");
  Handle interface_loader (THREAD, InstanceKlass::cast(interf_h())->class_loader());

  int ime_count = method_count_for_interface(interf_h());
  for (int i = 0; i < nof_methods; i++) {
    Method* m = methods->at(i);
    methodHandle target;
    if (m->has_itable_index()) {
      // This search must match the runtime resolution, i.e. selection search for invokeinterface
      // to correctly enforce loader constraints for interface method inheritance
      LinkResolver::lookup_instance_method_in_klasses(target, _klass, m->name(), m->signature(), CHECK);
    }
    if (target == NULL || !target->is_public() || target->is_abstract()) {
      // Entry does not resolve. Leave it empty for AbstractMethodError.
        if (!(target == NULL) && !target->is_public()) {
          // Stuff an IllegalAccessError throwing method in there instead.
          itableOffsetEntry::method_entry(_klass(), method_table_offset)[m->itable_index()].
              initialize(Universe::throw_illegal_access_error());
        }
    } else {
      // Entry did resolve, check loader constraints before initializing
      // if checkconstraints requested
      if (checkconstraints) {
        Handle method_holder_loader (THREAD, target->method_holder()->class_loader());
        if (method_holder_loader() != interface_loader()) {
          ResourceMark rm(THREAD);
          Symbol* failed_type_symbol =
            SystemDictionary::check_signature_loaders(m->signature(),
                                                      method_holder_loader,
                                                      interface_loader,
                                                      true, CHECK);
          if (failed_type_symbol != NULL) {
            const char* msg = "loader constraint violation in interface "
              "itable initialization: when resolving method \"%s\" the class"
              " loader (instance of %s) of the current class, %s, "
              "and the class loader (instance of %s) for interface "
              "%s have different Class objects for the type %s "
              "used in the signature";
            char* sig = target()->name_and_sig_as_C_string();
            const char* loader1 = SystemDictionary::loader_name(method_holder_loader());
            char* current = _klass->name()->as_C_string();
            const char* loader2 = SystemDictionary::loader_name(interface_loader());
            char* iface = InstanceKlass::cast(interf_h())->name()->as_C_string();
            char* failed_type_name = failed_type_symbol->as_C_string();
            size_t buflen = strlen(msg) + strlen(sig) + strlen(loader1) +
              strlen(current) + strlen(loader2) + strlen(iface) +
              strlen(failed_type_name);
            char* buf = NEW_RESOURCE_ARRAY_IN_THREAD(THREAD, char, buflen);
            jio_snprintf(buf, buflen, msg, sig, loader1, current, loader2,
                         iface, failed_type_name);
            THROW_MSG(vmSymbols::java_lang_LinkageError(), buf);
          }
        }
      }

      // ime may have moved during GC so recalculate address
      int ime_num = m->itable_index();
      assert(ime_num < ime_count, "oob");
      itableOffsetEntry::method_entry(_klass(), method_table_offset)[ime_num].initialize(target());
      if (TraceItables && Verbose) {
        ResourceMark rm(THREAD);
        if (target() != NULL) {
          char* sig = target()->name_and_sig_as_C_string();
          tty->print("interface: %s, ime_num: %d, target: %s, method_holder: %s ",
                    interf_h()->internal_name(), ime_num, sig,
                    target()->method_holder()->internal_name());
          tty->print("target_method flags: ");
          target()->access_flags().print_on(tty);
          if (target()->is_default_method()) {
            tty->print("default ");
          }
          tty->cr();
        }
      }
    }
  }
}

// Update entry for specific Method*
void klassItable::initialize_with_method(Method* m) {
  itableMethodEntry* ime = method_entry(0);
  for(int i = 0; i < _size_method_table; i++) {
    if (ime->method() == m) {
      ime->initialize(m);
    }
    ime++;
  }
}

#if INCLUDE_JVMTI
void klassItable::adjust_method_entries(Method** old_methods, Method** new_methods,
                                        int methods_length, bool * trace_name_printed) {
  // search the itable for uses of either obsolete or EMCP methods
  for (int j = 0; j < methods_length; j++) {
    Method* old_method = old_methods[j];
    Method* new_method = new_methods[j];
    itableMethodEntry* ime = method_entry(0);

    // The itable can describe more than one interface and the same
    // method signature can be specified by more than one interface.
    // This means we have to do an exhaustive search to find all the
    // old_method references.
    for (int i = 0; i < _size_method_table; i++) {
      if (ime->method() == old_method) {
        ime->initialize(new_method);

        if (RC_TRACE_IN_RANGE(0x00100000, 0x00400000)) {
          if (!(*trace_name_printed)) {
            // RC_TRACE_MESG macro has an embedded ResourceMark
            RC_TRACE_MESG(("adjust: name=%s",
              old_method->method_holder()->external_name()));
            *trace_name_printed = true;
          }
          // RC_TRACE macro has an embedded ResourceMark
          RC_TRACE(0x00200000, ("itable method update: %s(%s)",
            new_method->name()->as_C_string(),
            new_method->signature()->as_C_string()));
        }
        // cannot 'break' here; see for-loop comment above.
      }
      ime++;
    }
  }
}

// an itable should never contain old or obsolete methods
bool klassItable::check_no_old_or_obsolete_entries() {
  itableMethodEntry* ime = method_entry(0);
  for (int i = 0; i < _size_method_table; i++) {
    Method* m = ime->method();
    if (m != NULL &&
        (NOT_PRODUCT(!m->is_valid() ||) m->is_old() || m->is_obsolete())) {
      return false;
    }
    ime++;
  }
  return true;
}

void klassItable::dump_itable() {
  itableMethodEntry* ime = method_entry(0);
  tty->print_cr("itable dump --");
  for (int i = 0; i < _size_method_table; i++) {
    Method* m = ime->method();
    if (m != NULL) {
      tty->print("      (%5d)  ", i);
      m->access_flags().print_on(tty);
      if (m->is_default_method()) {
        tty->print("default ");
      }
      tty->print(" --  ");
      m->print_name(tty);
      tty->cr();
    }
    ime++;
  }
}
#endif // INCLUDE_JVMTI


// Setup
class InterfaceVisiterClosure : public StackObj {
 public:
  virtual void doit(Klass* intf, int method_count) = 0;
};

// Visit all interfaces with at least one itable method
void visit_all_interfaces(Array<Klass*>* transitive_intf, InterfaceVisiterClosure *blk) {
  // Handle array argument
  for(int i = 0; i < transitive_intf->length(); i++) {
    Klass* intf = transitive_intf->at(i);
    assert(intf->is_interface(), "sanity check");

    // Find no. of itable methods
    int method_count = 0;
    // method_count = klassItable::method_count_for_interface(intf);
    Array<Method*>* methods = InstanceKlass::cast(intf)->methods();
    if (methods->length() > 0) {
      for (int i = methods->length(); --i >= 0; ) {
        if (interface_method_needs_itable_index(methods->at(i))) {
          method_count++;
        }
      }
    }

    // Only count interfaces with at least one method
    if (method_count > 0) {
      blk->doit(intf, method_count);
    }
  }
}

class CountInterfacesClosure : public InterfaceVisiterClosure {
 private:
  int _nof_methods;
  int _nof_interfaces;
 public:
   CountInterfacesClosure() { _nof_methods = 0; _nof_interfaces = 0; }

   int nof_methods() const    { return _nof_methods; }
   int nof_interfaces() const { return _nof_interfaces; }

   void doit(Klass* intf, int method_count) { _nof_methods += method_count; _nof_interfaces++; }
};

class SetupItableClosure : public InterfaceVisiterClosure  {
 private:
  itableOffsetEntry* _offset_entry;
  itableMethodEntry* _method_entry;
  address            _klass_begin;
 public:
  SetupItableClosure(address klass_begin, itableOffsetEntry* offset_entry, itableMethodEntry* method_entry) {
    _klass_begin  = klass_begin;
    _offset_entry = offset_entry;
    _method_entry = method_entry;
  }

  itableMethodEntry* method_entry() const { return _method_entry; }

  void doit(Klass* intf, int method_count) {
    int offset = ((address)_method_entry) - _klass_begin;
    _offset_entry->initialize(intf, offset);
    _offset_entry++;
    _method_entry += method_count;
  }
};

int klassItable::compute_itable_size(Array<Klass*>* transitive_interfaces) {
  // Count no of interfaces and total number of interface methods
  CountInterfacesClosure cic;
  visit_all_interfaces(transitive_interfaces, &cic);

  // There's alway an extra itable entry so we can null-terminate it.
  int itable_size = calc_itable_size(cic.nof_interfaces() + 1, cic.nof_methods());

  // Statistics
  update_stats(itable_size * HeapWordSize);

  return itable_size;
}


// Fill out offset table and interface klasses into the itable space
void klassItable::setup_itable_offset_table(instanceKlassHandle klass) {
  if (klass->itable_length() == 0) return;
  assert(!klass->is_interface(), "Should have zero length itable");

  // Count no of interfaces and total number of interface methods
  CountInterfacesClosure cic;
  visit_all_interfaces(klass->transitive_interfaces(), &cic);
  int nof_methods    = cic.nof_methods();
  int nof_interfaces = cic.nof_interfaces();

  // Add one extra entry so we can null-terminate the table
  nof_interfaces++;

  assert(compute_itable_size(klass->transitive_interfaces()) ==
         calc_itable_size(nof_interfaces, nof_methods),
         "mismatch calculation of itable size");

  // Fill-out offset table
  itableOffsetEntry* ioe = (itableOffsetEntry*)klass->start_of_itable();
  itableMethodEntry* ime = (itableMethodEntry*)(ioe + nof_interfaces);
  intptr_t* end               = klass->end_of_itable();
  assert((oop*)(ime + nof_methods) <= (oop*)klass->start_of_nonstatic_oop_maps(), "wrong offset calculation (1)");
  assert((oop*)(end) == (oop*)(ime + nof_methods),                      "wrong offset calculation (2)");

  // Visit all interfaces and initialize itable offset table
  SetupItableClosure sic((address)klass(), ioe, ime);
  visit_all_interfaces(klass->transitive_interfaces(), &sic);

#ifdef ASSERT
  ime  = sic.method_entry();
  oop* v = (oop*) klass->end_of_itable();
  assert( (oop*)(ime) == v, "wrong offset calculation (2)");
#endif
}


// inverse to itable_index
Method* klassItable::method_for_itable_index(Klass* intf, int itable_index) {
  assert(InstanceKlass::cast(intf)->is_interface(), "sanity check");
  assert(intf->verify_itable_index(itable_index), "");
  Array<Method*>* methods = InstanceKlass::cast(intf)->methods();

  if (itable_index < 0 || itable_index >= method_count_for_interface(intf))
    return NULL;                // help caller defend against bad indices

  int index = itable_index;
  Method* m = methods->at(index);
  int index2 = -1;
  while (!m->has_itable_index() ||
         (index2 = m->itable_index()) != itable_index) {
    assert(index2 < itable_index, "monotonic");
    if (++index == methods->length())
      return NULL;
    m = methods->at(index);
  }
  assert(m->itable_index() == itable_index, "correct inverse");

  return m;
}

void klassVtable::verify(outputStream* st, bool forced) {
  // make sure table is initialized
  if (!Universe::is_fully_initialized()) return;
#ifndef PRODUCT
  // avoid redundant verifies
  if (!forced && _verify_count == Universe::verify_count()) return;
  _verify_count = Universe::verify_count();
#endif
  oop* end_of_obj = (oop*)_klass() + _klass()->size();
  oop* end_of_vtable = (oop *)&table()[_length];
  if (end_of_vtable > end_of_obj) {
    fatal(err_msg("klass %s: klass object too short (vtable extends beyond "
                  "end)", _klass->internal_name()));
  }

  for (int i = 0; i < _length; i++) table()[i].verify(this, st);
  // verify consistency with superKlass vtable
  Klass* super = _klass->super();
  if (super != NULL) {
    InstanceKlass* sk = InstanceKlass::cast(super);
    klassVtable* vt = sk->vtable();
    for (int i = 0; i < vt->length(); i++) {
      verify_against(st, vt, i);
    }
  }
}

void klassVtable::verify_against(outputStream* st, klassVtable* vt, int index) {
  vtableEntry* vte = &vt->table()[index];
  if (vte->method()->name()      != table()[index].method()->name() ||
      vte->method()->signature() != table()[index].method()->signature()) {
    fatal("mismatched name/signature of vtable entries");
  }
}

#ifndef PRODUCT
void klassVtable::print() {
  ResourceMark rm;
  tty->print("klassVtable for klass %s (length %d):\n", _klass->internal_name(), length());
  for (int i = 0; i < length(); i++) {
    table()[i].print();
    tty->cr();
  }
}
#endif

void vtableEntry::verify(klassVtable* vt, outputStream* st) {
  NOT_PRODUCT(FlagSetting fs(IgnoreLockingAssertions, true));
  assert(method() != NULL, "must have set method");
  method()->verify();
  // we sub_type, because it could be a miranda method
  if (!vt->klass()->is_subtype_of(method()->method_holder())) {
#ifndef PRODUCT
    print();
#endif
    fatal(err_msg("vtableEntry " PTR_FORMAT ": method is from subclass", this));
  }
}

#ifndef PRODUCT

void vtableEntry::print() {
  ResourceMark rm;
  tty->print("vtableEntry %s: ", method()->name()->as_C_string());
  if (Verbose) {
    tty->print("m %#lx ", (address)method());
  }
}

class VtableStats : AllStatic {
 public:
  static int no_klasses;                // # classes with vtables
  static int no_array_klasses;          // # array classes
  static int no_instance_klasses;       // # instanceKlasses
  static int sum_of_vtable_len;         // total # of vtable entries
  static int sum_of_array_vtable_len;   // total # of vtable entries in array klasses only
  static int fixed;                     // total fixed overhead in bytes
  static int filler;                    // overhead caused by filler bytes
  static int entries;                   // total bytes consumed by vtable entries
  static int array_entries;             // total bytes consumed by array vtable entries

  static void do_class(Klass* k) {
    Klass* kl = k;
    klassVtable* vt = kl->vtable();
    if (vt == NULL) return;
    no_klasses++;
    if (kl->oop_is_instance()) {
      no_instance_klasses++;
      kl->array_klasses_do(do_class);
    }
    if (kl->oop_is_array()) {
      no_array_klasses++;
      sum_of_array_vtable_len += vt->length();
    }
    sum_of_vtable_len += vt->length();
  }

  static void compute() {
    SystemDictionary::classes_do(do_class);
    fixed  = no_klasses * oopSize;      // vtable length
    // filler size is a conservative approximation
    filler = oopSize * (no_klasses - no_instance_klasses) * (sizeof(InstanceKlass) - sizeof(ArrayKlass) - 1);
    entries = sizeof(vtableEntry) * sum_of_vtable_len;
    array_entries = sizeof(vtableEntry) * sum_of_array_vtable_len;
  }
};

int VtableStats::no_klasses = 0;
int VtableStats::no_array_klasses = 0;
int VtableStats::no_instance_klasses = 0;
int VtableStats::sum_of_vtable_len = 0;
int VtableStats::sum_of_array_vtable_len = 0;
int VtableStats::fixed = 0;
int VtableStats::filler = 0;
int VtableStats::entries = 0;
int VtableStats::array_entries = 0;

void klassVtable::print_statistics() {
  ResourceMark rm;
  HandleMark hm;
  VtableStats::compute();
  tty->print_cr("vtable statistics:");
  tty->print_cr("%6d classes (%d instance, %d array)", VtableStats::no_klasses, VtableStats::no_instance_klasses, VtableStats::no_array_klasses);
  int total = VtableStats::fixed + VtableStats::filler + VtableStats::entries;
  tty->print_cr("%6d bytes fixed overhead (refs + vtable object header)", VtableStats::fixed);
  tty->print_cr("%6d bytes filler overhead", VtableStats::filler);
  tty->print_cr("%6d bytes for vtable entries (%d for arrays)", VtableStats::entries, VtableStats::array_entries);
  tty->print_cr("%6d bytes total", total);
}

int  klassItable::_total_classes;   // Total no. of classes with itables
long klassItable::_total_size;      // Total no. of bytes used for itables

void klassItable::print_statistics() {
 tty->print_cr("itable statistics:");
 tty->print_cr("%6d classes with itables", _total_classes);
 tty->print_cr("%6d K uses for itables (average by class: %d bytes)", _total_size / K, _total_size / _total_classes);
}

#endif // PRODUCT

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