Mercurial > jdk8-mips64-public > hotspot / file revision

 /*

  * Copyright (c) 1997, 2018, 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/javaClasses.hpp"

 #include "classfile/dictionary.hpp"

 #include "classfile/systemDictionary.hpp"

 #include "classfile/vmSymbols.hpp"

 #include "gc_implementation/shared/markSweep.inline.hpp"

 #include "gc_interface/collectedHeap.inline.hpp"

 #include "memory/heapInspection.hpp"

 #include "memory/metadataFactory.hpp"

 #include "memory/oopFactory.hpp"

 #include "memory/resourceArea.hpp"

 #include "oops/instanceKlass.hpp"

 #include "oops/klass.inline.hpp"

 #include "oops/oop.inline2.hpp"

 #include "runtime/atomic.inline.hpp"

 #include "runtime/orderAccess.inline.hpp"

 #include "trace/traceMacros.hpp"

 #include "utilities/stack.hpp"

 #include "utilities/macros.hpp"

 #if INCLUDE_ALL_GCS

 #include "gc_implementation/g1/g1SATBCardTableModRefBS.hpp"

 #include "gc_implementation/parallelScavenge/psParallelCompact.hpp"

 #include "gc_implementation/parallelScavenge/psPromotionManager.hpp"

 #include "gc_implementation/parallelScavenge/psScavenge.hpp"

 #endif // INCLUDE_ALL_GCS

 bool Klass::is_cloneable() const {

   return _access_flags.is_cloneable() ||

          is_subtype_of(SystemDictionary::Cloneable_klass());

 }

 void Klass::set_is_cloneable() {

   if (oop_is_instance() && InstanceKlass::cast(this)->reference_type() != REF_NONE) {

     // Reference cloning should not be intrinsified and always happen in JVM_Clone.

   } else {

     _access_flags.set_is_cloneable();

   }

 }

 void Klass::set_name(Symbol* n) {

   _name = n;

   if (_name != NULL) _name->increment_refcount();

 }

 bool Klass::is_subclass_of(const Klass* k) const {

   // Run up the super chain and check

   if (this == k) return true;

   Klass* t = const_cast<Klass*>(this)->super();

   while (t != NULL) {

     if (t == k) return true;

     t = t->super();

   }

   return false;

 }

 bool Klass::search_secondary_supers(Klass* k) const {

   // Put some extra logic here out-of-line, before the search proper.

   // This cuts down the size of the inline method.

   // This is necessary, since I am never in my own secondary_super list.

   if (this == k)

     return true;

   // Scan the array-of-objects for a match

   int cnt = secondary_supers()->length();

   for (int i = 0; i < cnt; i++) {

     if (secondary_supers()->at(i) == k) {

       ((Klass*)this)->set_secondary_super_cache(k);

       return true;

     }

   }

   return false;

 }

 // Return self, except for abstract classes with exactly 1

 // implementor.  Then return the 1 concrete implementation.

 Klass *Klass::up_cast_abstract() {

   Klass *r = this;

   while( r->is_abstract() ) {   // Receiver is abstract?

     Klass *s = r->subklass();   // Check for exactly 1 subklass

     if( !s || s->next_sibling() ) // Oops; wrong count; give up

       return this;              // Return 'this' as a no-progress flag

     r = s;                    // Loop till find concrete class

   }

   return r;                   // Return the 1 concrete class

 }

 // Find LCA in class hierarchy

 Klass *Klass::LCA( Klass *k2 ) {

   Klass *k1 = this;

   while( 1 ) {

     if( k1->is_subtype_of(k2) ) return k2;

     if( k2->is_subtype_of(k1) ) return k1;

     k1 = k1->super();

     k2 = k2->super();

   }

 }

 void Klass::check_valid_for_instantiation(bool throwError, TRAPS) {

   ResourceMark rm(THREAD);

   THROW_MSG(throwError ? vmSymbols::java_lang_InstantiationError()

             : vmSymbols::java_lang_InstantiationException(), external_name());

 }

 void Klass::copy_array(arrayOop s, int src_pos, arrayOop d, int dst_pos, int length, TRAPS) {

   THROW(vmSymbols::java_lang_ArrayStoreException());

 }

 void Klass::initialize(TRAPS) {

   ShouldNotReachHere();

 }

 bool Klass::compute_is_subtype_of(Klass* k) {

   assert(k->is_klass(), "argument must be a class");

   return is_subclass_of(k);

 }

 Klass* Klass::find_field(Symbol* name, Symbol* sig, fieldDescriptor* fd) const {

 #ifdef ASSERT

   tty->print_cr("Error: find_field called on a klass oop."

                 " Likely error: reflection method does not correctly"

                 " wrap return value in a mirror object.");

 #endif

   ShouldNotReachHere();

   return NULL;

 }

 Method* Klass::uncached_lookup_method(Symbol* name, Symbol* signature, OverpassLookupMode overpass_mode) const {

 #ifdef ASSERT

   tty->print_cr("Error: uncached_lookup_method called on a klass oop."

                 " Likely error: reflection method does not correctly"

                 " wrap return value in a mirror object.");

 #endif

   ShouldNotReachHere();

   return NULL;

 }

 void* Klass::operator new(size_t size, ClassLoaderData* loader_data, size_t word_size, TRAPS) throw() {

   return Metaspace::allocate(loader_data, word_size, /*read_only*/false,

                              MetaspaceObj::ClassType, THREAD);

 }

 Klass::Klass() {

   Klass* k = this;

   // Preinitialize supertype information.

   // A later call to initialize_supers() may update these settings:

   set_super(NULL);

   for (juint i = 0; i < Klass::primary_super_limit(); i++) {

     _primary_supers[i] = NULL;

   }

   set_secondary_supers(NULL);

   set_secondary_super_cache(NULL);

   _primary_supers[0] = k;

   set_super_check_offset(in_bytes(primary_supers_offset()));

   // The constructor is used from init_self_patching_vtbl_list,

   // which doesn't zero out the memory before calling the constructor.

   // Need to set the field explicitly to not hit an assert that the field

   // should be NULL before setting it.

   _java_mirror = NULL;

   set_modifier_flags(0);

   set_layout_helper(Klass::_lh_neutral_value);

   set_name(NULL);

   AccessFlags af;

   af.set_flags(0);

   set_access_flags(af);

   set_subklass(NULL);

   set_next_sibling(NULL);

   set_next_link(NULL);

   TRACE_INIT_ID(this);

   set_prototype_header(markOopDesc::prototype());

   set_biased_lock_revocation_count(0);

   set_last_biased_lock_bulk_revocation_time(0);

   // The klass doesn't have any references at this point.

   clear_modified_oops();

   clear_accumulated_modified_oops();

   _shared_class_path_index = -1;

 }

 jint Klass::array_layout_helper(BasicType etype) {

   assert(etype >= T_BOOLEAN && etype <= T_OBJECT, "valid etype");

   // Note that T_ARRAY is not allowed here.

   int  hsize = arrayOopDesc::base_offset_in_bytes(etype);

   int  esize = type2aelembytes(etype);

   bool isobj = (etype == T_OBJECT);

   int  tag   =  isobj ? _lh_array_tag_obj_value : _lh_array_tag_type_value;

   int lh = array_layout_helper(tag, hsize, etype, exact_log2(esize));

   assert(lh < (int)_lh_neutral_value, "must look like an array layout");

   assert(layout_helper_is_array(lh), "correct kind");

   assert(layout_helper_is_objArray(lh) == isobj, "correct kind");

   assert(layout_helper_is_typeArray(lh) == !isobj, "correct kind");

   assert(layout_helper_header_size(lh) == hsize, "correct decode");

   assert(layout_helper_element_type(lh) == etype, "correct decode");

   assert(1 << layout_helper_log2_element_size(lh) == esize, "correct decode");

   return lh;

 }

 bool Klass::can_be_primary_super_slow() const {

   if (super() == NULL)

     return true;

   else if (super()->super_depth() >= primary_super_limit()-1)

     return false;

   else

     return true;

 }

 void Klass::initialize_supers(Klass* k, TRAPS) {

   if (FastSuperclassLimit == 0) {

     // None of the other machinery matters.

     set_super(k);

     return;

   }

   if (k == NULL) {

     set_super(NULL);

     _primary_supers[0] = this;

     assert(super_depth() == 0, "Object must already be initialized properly");

   } else if (k != super() || k == SystemDictionary::Object_klass()) {

     assert(super() == NULL || super() == SystemDictionary::Object_klass(),

            "initialize this only once to a non-trivial value");

     set_super(k);

     Klass* sup = k;

     int sup_depth = sup->super_depth();

     juint my_depth  = MIN2(sup_depth + 1, (int)primary_super_limit());

     if (!can_be_primary_super_slow())

       my_depth = primary_super_limit();

     for (juint i = 0; i < my_depth; i++) {

       _primary_supers[i] = sup->_primary_supers[i];

     }

     Klass* *super_check_cell;

     if (my_depth < primary_super_limit()) {

       _primary_supers[my_depth] = this;

       super_check_cell = &_primary_supers[my_depth];

     } else {

       // Overflow of the primary_supers array forces me to be secondary.

       super_check_cell = &_secondary_super_cache;

     }

     set_super_check_offset((address)super_check_cell - (address) this);

 #ifdef ASSERT

     {

       juint j = super_depth();

       assert(j == my_depth, "computed accessor gets right answer");

       Klass* t = this;

       while (!t->can_be_primary_super()) {

         t = t->super();

         j = t->super_depth();

       }

       for (juint j1 = j+1; j1 < primary_super_limit(); j1++) {

         assert(primary_super_of_depth(j1) == NULL, "super list padding");

       }

       while (t != NULL) {

         assert(primary_super_of_depth(j) == t, "super list initialization");

         t = t->super();

         --j;

       }

       assert(j == (juint)-1, "correct depth count");

     }

 #endif

   }

   if (secondary_supers() == NULL) {

     KlassHandle this_kh (THREAD, this);

     // Now compute the list of secondary supertypes.

     // Secondaries can occasionally be on the super chain,

     // if the inline "_primary_supers" array overflows.

     int extras = 0;

     Klass* p;

     for (p = super(); !(p == NULL || p->can_be_primary_super()); p = p->super()) {

       ++extras;

     }

     ResourceMark rm(THREAD);  // need to reclaim GrowableArrays allocated below

     // Compute the "real" non-extra secondaries.

     GrowableArray<Klass*>* secondaries = compute_secondary_supers(extras);

     if (secondaries == NULL) {

       // secondary_supers set by compute_secondary_supers

       return;

     }

     GrowableArray<Klass*>* primaries = new GrowableArray<Klass*>(extras);

     for (p = this_kh->super(); !(p == NULL || p->can_be_primary_super()); p = p->super()) {

       int i;                    // Scan for overflow primaries being duplicates of 2nd'arys

       // This happens frequently for very deeply nested arrays: the

       // primary superclass chain overflows into the secondary.  The

       // secondary list contains the element_klass's secondaries with

       // an extra array dimension added.  If the element_klass's

       // secondary list already contains some primary overflows, they

       // (with the extra level of array-ness) will collide with the

       // normal primary superclass overflows.

       for( i = 0; i < secondaries->length(); i++ ) {

         if( secondaries->at(i) == p )

           break;

       }

       if( i < secondaries->length() )

         continue;               // It's a dup, don't put it in

       primaries->push(p);

     }

     // Combine the two arrays into a metadata object to pack the array.

     // The primaries are added in the reverse order, then the secondaries.

     int new_length = primaries->length() + secondaries->length();

     Array<Klass*>* s2 = MetadataFactory::new_array<Klass*>(

                                        class_loader_data(), new_length, CHECK);

     int fill_p = primaries->length();

     for (int j = 0; j < fill_p; j++) {

       s2->at_put(j, primaries->pop());  // add primaries in reverse order.

     }

     for( int j = 0; j < secondaries->length(); j++ ) {

       s2->at_put(j+fill_p, secondaries->at(j));  // add secondaries on the end.

     }

   #ifdef ASSERT

       // We must not copy any NULL placeholders left over from bootstrap.

     for (int j = 0; j < s2->length(); j++) {

       assert(s2->at(j) != NULL, "correct bootstrapping order");

     }

   #endif

     this_kh->set_secondary_supers(s2);

   }

 }

 GrowableArray<Klass*>* Klass::compute_secondary_supers(int num_extra_slots) {

   assert(num_extra_slots == 0, "override for complex klasses");

   set_secondary_supers(Universe::the_empty_klass_array());

   return NULL;

 }

 Klass* Klass::subklass() const {

   return _subklass == NULL ? NULL : _subklass;

 }

 InstanceKlass* Klass::superklass() const {

   assert(super() == NULL || super()->oop_is_instance(), "must be instance klass");

   return _super == NULL ? NULL : InstanceKlass::cast(_super);

 }

 Klass* Klass::next_sibling() const {

   return _next_sibling == NULL ? NULL : _next_sibling;

 }

 void Klass::set_subklass(Klass* s) {

   assert(s != this, "sanity check");

   _subklass = s;

 }

 void Klass::set_next_sibling(Klass* s) {

   assert(s != this, "sanity check");

   _next_sibling = s;

 }

 void Klass::append_to_sibling_list() {

   debug_only(verify();)

   // add ourselves to superklass' subklass list

   InstanceKlass* super = superklass();

   if (super == NULL) return;        // special case: class Object

   assert((!super->is_interface()    // interfaces cannot be supers

           && (super->superklass() == NULL || !is_interface())),

          "an interface can only be a subklass of Object");

   Klass* prev_first_subklass = super->subklass_oop();

   if (prev_first_subklass != NULL) {

     // set our sibling to be the superklass' previous first subklass

     set_next_sibling(prev_first_subklass);

   }

   // make ourselves the superklass' first subklass

   super->set_subklass(this);

   debug_only(verify();)

 }

 bool Klass::is_loader_alive(BoolObjectClosure* is_alive) {

 #ifdef ASSERT

   // The class is alive iff the class loader is alive.

   oop loader = class_loader();

   bool loader_alive = (loader == NULL) || is_alive->do_object_b(loader);

 #endif // ASSERT

   // The class is alive if it's mirror is alive (which should be marked if the

   // loader is alive) unless it's an anoymous class.

   bool mirror_alive = is_alive->do_object_b(java_mirror());

   assert(!mirror_alive || loader_alive, "loader must be alive if the mirror is"

                         " but not the other way around with anonymous classes");

   return mirror_alive;

 }

 void Klass::clean_weak_klass_links(BoolObjectClosure* is_alive, bool clean_alive_klasses) {

   if (!ClassUnloading) {

     return;

   }

   Klass* root = SystemDictionary::Object_klass();

   Stack<Klass*, mtGC> stack;

   stack.push(root);

   while (!stack.is_empty()) {

     Klass* current = stack.pop();

     assert(current->is_loader_alive(is_alive), "just checking, this should be live");

     // Find and set the first alive subklass

     Klass* sub = current->subklass_oop();

     while (sub != NULL && !sub->is_loader_alive(is_alive)) {

 #ifndef PRODUCT

       if (TraceClassUnloading && WizardMode) {

         ResourceMark rm;

         tty->print_cr("[Unlinking class (subclass) %s]", sub->external_name());

       }

 #endif

       sub = sub->next_sibling_oop();

     }

     current->set_subklass(sub);

     if (sub != NULL) {

       stack.push(sub);

     }

     // Find and set the first alive sibling

     Klass* sibling = current->next_sibling_oop();

     while (sibling != NULL && !sibling->is_loader_alive(is_alive)) {

       if (TraceClassUnloading && WizardMode) {

         ResourceMark rm;

         tty->print_cr("[Unlinking class (sibling) %s]", sibling->external_name());

       }

       sibling = sibling->next_sibling_oop();

     }

     current->set_next_sibling(sibling);

     if (sibling != NULL) {

       stack.push(sibling);

     }

     // Clean the implementors list and method data.

     if (clean_alive_klasses && current->oop_is_instance()) {

       InstanceKlass* ik = InstanceKlass::cast(current);

       ik->clean_weak_instanceklass_links(is_alive);

       // JVMTI RedefineClasses creates previous versions that are not in

       // the class hierarchy, so process them here.

       while ((ik = ik->previous_versions()) != NULL) {

         ik->clean_weak_instanceklass_links(is_alive);

       }

     }

   }

 }

 void Klass::klass_update_barrier_set(oop v) {

   record_modified_oops();

 }

 // This barrier is used by G1 to remember the old oop values, so

 // that we don't forget any objects that were live at the snapshot at

 // the beginning. This function is only used when we write oops into Klasses.

 void Klass::klass_update_barrier_set_pre(oop* p, oop v) {

 #if INCLUDE_ALL_GCS

   if (UseG1GC) {

     oop obj = *p;

     if (obj != NULL) {

       G1SATBCardTableModRefBS::enqueue(obj);

     }

   }

 #endif

 }

 void Klass::klass_oop_store(oop* p, oop v) {

   assert(!Universe::heap()->is_in_reserved((void*)p), "Should store pointer into metadata");

   assert(v == NULL || Universe::heap()->is_in_reserved((void*)v), "Should store pointer to an object");

   // do the store

   if (always_do_update_barrier) {

     klass_oop_store((volatile oop*)p, v);

   } else {

     klass_update_barrier_set_pre(p, v);

     *p = v;

     klass_update_barrier_set(v);

   }

 }

 void Klass::klass_oop_store(volatile oop* p, oop v) {

   assert(!Universe::heap()->is_in_reserved((void*)p), "Should store pointer into metadata");

   assert(v == NULL || Universe::heap()->is_in_reserved((void*)v), "Should store pointer to an object");

   klass_update_barrier_set_pre((oop*)p, v); // Cast away volatile.

   OrderAccess::release_store_ptr(p, v);

   klass_update_barrier_set(v);

 }

 void Klass::oops_do(OopClosure* cl) {

   cl->do_oop(&_java_mirror);

 }

 void Klass::remove_unshareable_info() {

   assert (DumpSharedSpaces, "only called for DumpSharedSpaces");

   set_subklass(NULL);

   set_next_sibling(NULL);

   // Clear the java mirror

   set_java_mirror(NULL);

   set_next_link(NULL);

   // Null out class_loader_data because we don't share that yet.

   set_class_loader_data(NULL);

 }

 void Klass::restore_unshareable_info(ClassLoaderData* loader_data, Handle protection_domain, TRAPS) {

   TRACE_INIT_ID(this);

   // If an exception happened during CDS restore, some of these fields may already be

   // set.  We leave the class on the CLD list, even if incomplete so that we don't

   // modify the CLD list outside a safepoint.

   if (class_loader_data() == NULL) {

     // Restore class_loader_data

     set_class_loader_data(loader_data);

     // Add to class loader list first before creating the mirror

     // (same order as class file parsing)

     loader_data->add_class(this);

   }

   // Recreate the class mirror.

   // Only recreate it if not present.  A previous attempt to restore may have

   // gotten an OOM later but keep the mirror if it was created.

   if (java_mirror() == NULL) {

     java_lang_Class::create_mirror(this, class_loader(), protection_domain, CHECK);

   }

 }

 Klass* Klass::array_klass_or_null(int rank) {

   EXCEPTION_MARK;

   // No exception can be thrown by array_klass_impl when called with or_null == true.

   // (In anycase, the execption mark will fail if it do so)

   return array_klass_impl(true, rank, THREAD);

 }

 Klass* Klass::array_klass_or_null() {

   EXCEPTION_MARK;

   // No exception can be thrown by array_klass_impl when called with or_null == true.

   // (In anycase, the execption mark will fail if it do so)

   return array_klass_impl(true, THREAD);

 }

 Klass* Klass::array_klass_impl(bool or_null, int rank, TRAPS) {

   fatal("array_klass should be dispatched to InstanceKlass, ObjArrayKlass or TypeArrayKlass");

   return NULL;

 }

 Klass* Klass::array_klass_impl(bool or_null, TRAPS) {

   fatal("array_klass should be dispatched to InstanceKlass, ObjArrayKlass or TypeArrayKlass");

   return NULL;

 }

 oop Klass::class_loader() const { return class_loader_data()->class_loader(); }

 const char* Klass::external_name() const {

   if (oop_is_instance()) {

     InstanceKlass* ik = (InstanceKlass*) this;

     if (ik->is_anonymous()) {

       assert(EnableInvokeDynamic, "");

       intptr_t hash = 0;

       if (ik->java_mirror() != NULL) {

         // java_mirror might not be created yet, return 0 as hash.

         hash = ik->java_mirror()->identity_hash();

       }

       char     hash_buf[40];

       sprintf(hash_buf, "/" UINTX_FORMAT, (uintx)hash);

       size_t   hash_len = strlen(hash_buf);

       size_t result_len = name()->utf8_length();

       char*  result     = NEW_RESOURCE_ARRAY(char, result_len + hash_len + 1);

       name()->as_klass_external_name(result, (int) result_len + 1);

       assert(strlen(result) == result_len, "");

       strcpy(result + result_len, hash_buf);

       assert(strlen(result) == result_len + hash_len, "");

       return result;

     }

   }

   if (name() == NULL)  return "<unknown>";

   return name()->as_klass_external_name();

 }

 const char* Klass::signature_name() const {

   if (name() == NULL)  return "<unknown>";

   return name()->as_C_string();

 }

 // Unless overridden, modifier_flags is 0.

 jint Klass::compute_modifier_flags(TRAPS) const {

   return 0;

 }

 int Klass::atomic_incr_biased_lock_revocation_count() {

   return (int) Atomic::add(1, &_biased_lock_revocation_count);

 }

 // Unless overridden, jvmti_class_status has no flags set.

 jint Klass::jvmti_class_status() const {

   return 0;

 }

 // Printing

 void Klass::print_on(outputStream* st) const {

   ResourceMark rm;

   // print title

   st->print("%s", internal_name());

   print_address_on(st);

   st->cr();

 }

 void Klass::oop_print_on(oop obj, outputStream* st) {

   ResourceMark rm;

   // print title

   st->print_cr("%s ", internal_name());

   obj->print_address_on(st);

   if (WizardMode) {

      // print header

      obj->mark()->print_on(st);

   }

   // print class

   st->print(" - klass: ");

   obj->klass()->print_value_on(st);

   st->cr();

 }

 void Klass::oop_print_value_on(oop obj, outputStream* st) {

   // print title

   ResourceMark rm;              // Cannot print in debug mode without this

   st->print("%s", internal_name());

   obj->print_address_on(st);

 }

 #if INCLUDE_SERVICES

 // Size Statistics

 void Klass::collect_statistics(KlassSizeStats *sz) const {

   sz->_klass_bytes = sz->count(this);

   sz->_mirror_bytes = sz->count(java_mirror());

   sz->_secondary_supers_bytes = sz->count_array(secondary_supers());

   sz->_ro_bytes += sz->_secondary_supers_bytes;

   sz->_rw_bytes += sz->_klass_bytes + sz->_mirror_bytes;

 }

 #endif // INCLUDE_SERVICES

 // Verification

 void Klass::verify_on(outputStream* st) {

   // This can be expensive, but it is worth checking that this klass is actually

   // in the CLD graph but not in production.

   assert(Metaspace::contains((address)this), "Should be");

   guarantee(this->is_klass(),"should be klass");

   if (super() != NULL) {

     guarantee(super()->is_klass(), "should be klass");

   }

   if (secondary_super_cache() != NULL) {

     Klass* ko = secondary_super_cache();

     guarantee(ko->is_klass(), "should be klass");

   }

   for ( uint i = 0; i < primary_super_limit(); i++ ) {

     Klass* ko = _primary_supers[i];

     if (ko != NULL) {

       guarantee(ko->is_klass(), "should be klass");

     }

   }

   if (java_mirror() != NULL) {

     guarantee(java_mirror()->is_oop(), "should be instance");

   }

 }

 void Klass::oop_verify_on(oop obj, outputStream* st) {

   guarantee(obj->is_oop(),  "should be oop");

   guarantee(obj->klass()->is_klass(), "klass field is not a klass");

 }

 #ifndef PRODUCT

 bool Klass::verify_vtable_index(int i) {

   if (oop_is_instance()) {

     int limit = ((InstanceKlass*)this)->vtable_length()/vtableEntry::size();

     assert(i >= 0 && i < limit, err_msg("index %d out of bounds %d", i, limit));

   } else {

     assert(oop_is_array(), "Must be");

     int limit = ((ArrayKlass*)this)->vtable_length()/vtableEntry::size();

     assert(i >= 0 && i < limit, err_msg("index %d out of bounds %d", i, limit));

   }

   return true;

 }

 bool Klass::verify_itable_index(int i) {

   assert(oop_is_instance(), "");

   int method_count = klassItable::method_count_for_interface(this);

   assert(i >= 0 && i < method_count, "index out of bounds");

   return true;

 }

 #endif

 /////////////// Unit tests ///////////////

 #ifndef PRODUCT

 class TestKlass {

  public:

   static void test_oop_is_instanceClassLoader() {

     assert(SystemDictionary::ClassLoader_klass()->oop_is_instanceClassLoader(), "assert");

     assert(!SystemDictionary::String_klass()->oop_is_instanceClassLoader(), "assert");

   }

 };

 void TestKlass_test() {

   TestKlass::test_oop_is_instanceClassLoader();

 }

 #endif