jdk8-mips64-public/hotspot: src/share/vm/prims/jvmtiRedefineClasses.cpp@da91efe96a93 (annotated)

src/share/vm/prims/jvmtiRedefineClasses.cpp@da91efe96a93 (annotated)

src/share/vm/prims/jvmtiRedefineClasses.cpp

Sat, 01 Sep 2012 13:25:18 -0400

author: coleenp
date: Sat, 01 Sep 2012 13:25:18 -0400
changeset 4037: da91efe96a93
parent 3921: e74da3c2b827
child 4142: d8ce2825b193
permissions: -rw-r--r--

6964458: Reimplement class meta-data storage to use native memory
Summary: Remove PermGen, allocate meta-data in metaspace linked to class loaders, rewrite GC walking, rewrite and rename metadata to be C++ classes
Reviewed-by: jmasa, stefank, never, coleenp, kvn, brutisso, mgerdin, dholmes, jrose, twisti, roland
Contributed-by: jmasa <jon.masamitsu@oracle.com>, stefank <stefan.karlsson@oracle.com>, mgerdin <mikael.gerdin@oracle.com>, never <tom.rodriguez@oracle.com>

 /*
  * Copyright (c) 2003, 2012, 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/verifier.hpp"
 #include "code/codeCache.hpp"
 #include "compiler/compileBroker.hpp"
 #include "interpreter/oopMapCache.hpp"
 #include "interpreter/rewriter.hpp"
 #include "memory/gcLocker.hpp"
 #include "memory/metadataFactory.hpp"
 #include "memory/metaspaceShared.hpp"
 #include "memory/universe.inline.hpp"
 #include "oops/fieldStreams.hpp"
 #include "oops/klassVtable.hpp"
 #include "prims/jvmtiImpl.hpp"
 #include "prims/jvmtiRedefineClasses.hpp"
 #include "prims/methodComparator.hpp"
 #include "runtime/deoptimization.hpp"
 #include "runtime/relocator.hpp"
 #include "utilities/bitMap.inline.hpp"
 Array<Method*>* VM_RedefineClasses::_old_methods = NULL;
 Array<Method*>* VM_RedefineClasses::_new_methods = NULL;
 Method**  VM_RedefineClasses::_matching_old_methods = NULL;
 Method**  VM_RedefineClasses::_matching_new_methods = NULL;
 Method**  VM_RedefineClasses::_deleted_methods      = NULL;
 Method**  VM_RedefineClasses::_added_methods        = NULL;
 int         VM_RedefineClasses::_matching_methods_length = 0;
 int         VM_RedefineClasses::_deleted_methods_length  = 0;
 int         VM_RedefineClasses::_added_methods_length    = 0;
 Klass*      VM_RedefineClasses::_the_class_oop = NULL;
 VM_RedefineClasses::VM_RedefineClasses(jint class_count,
                                        const jvmtiClassDefinition *class_defs,
                                        JvmtiClassLoadKind class_load_kind) {
   _class_count = class_count;
   _class_defs = class_defs;
   _class_load_kind = class_load_kind;
   _res = JVMTI_ERROR_NONE;
 }
 bool VM_RedefineClasses::doit_prologue() {
   if (_class_count == 0) {
     _res = JVMTI_ERROR_NONE;
     return false;
   }
   if (_class_defs == NULL) {
     _res = JVMTI_ERROR_NULL_POINTER;
     return false;
   }
   for (int i = 0; i < _class_count; i++) {
     if (_class_defs[i].klass == NULL) {
       _res = JVMTI_ERROR_INVALID_CLASS;
       return false;
     }
     if (_class_defs[i].class_byte_count == 0) {
       _res = JVMTI_ERROR_INVALID_CLASS_FORMAT;
       return false;
     }
     if (_class_defs[i].class_bytes == NULL) {
       _res = JVMTI_ERROR_NULL_POINTER;
       return false;
     }
   }
   // Start timer after all the sanity checks; not quite accurate, but
   // better than adding a bunch of stop() calls.
   RC_TIMER_START(_timer_vm_op_prologue);
   // We first load new class versions in the prologue, because somewhere down the
   // call chain it is required that the current thread is a Java thread.
   _res = load_new_class_versions(Thread::current());
   if (_res != JVMTI_ERROR_NONE) {
     // free any successfully created classes, since none are redefined
     for (int i = 0; i < _class_count; i++) {
       if (_scratch_classes[i] != NULL) {
         ClassLoaderData* cld = _scratch_classes[i]->class_loader_data();
         // Free the memory for this class at class unloading time.  Not before
         // because CMS might think this is still live.
         cld->add_to_deallocate_list((InstanceKlass*)_scratch_classes[i]);
       }
     }
     // Free os::malloc allocated memory in load_new_class_version.
     os::free(_scratch_classes);
     RC_TIMER_STOP(_timer_vm_op_prologue);
     return false;
   }
   RC_TIMER_STOP(_timer_vm_op_prologue);
   return true;
 }
 // Keep track of marked on-stack metadata so it can be cleared.
 GrowableArray<Metadata*>* _marked_objects = NULL;
 NOT_PRODUCT(bool MetadataOnStackMark::_is_active = false;)
 // Walk metadata on the stack and mark it so that redefinition doesn't delete
 // it.  Class unloading also walks the previous versions and might try to
 // delete it, so this class is used by class unloading also.
 MetadataOnStackMark::MetadataOnStackMark() {
   assert(SafepointSynchronize::is_at_safepoint(), "sanity check");
   NOT_PRODUCT(_is_active = true;)
   if (_marked_objects == NULL) {
     _marked_objects = new (ResourceObj::C_HEAP, mtClass) GrowableArray<Metadata*>(1000, true);
   }
   Threads::metadata_do(Metadata::mark_on_stack);
   CodeCache::alive_nmethods_do(nmethod::mark_on_stack);
   CompileBroker::mark_on_stack();
 }
 MetadataOnStackMark::~MetadataOnStackMark() {
   assert(SafepointSynchronize::is_at_safepoint(), "sanity check");
   // Unmark everything that was marked.   Can't do the same walk because
   // redefine classes messes up the code cache so the set of methods
   // might not be the same.
   for (int i = 0; i< _marked_objects->length(); i++) {
     _marked_objects->at(i)->set_on_stack(false);
   }
   _marked_objects->clear();   // reuse growable array for next time.
   NOT_PRODUCT(_is_active = false;)
 }
 // Record which objects are marked so we can unmark the same objects.
 void MetadataOnStackMark::record(Metadata* m) {
   assert(_is_active, "metadata on stack marking is active");
   _marked_objects->push(m);
 }
 void VM_RedefineClasses::doit() {
   Thread *thread = Thread::current();
   if (UseSharedSpaces) {
     // Sharing is enabled so we remap the shared readonly space to
     // shared readwrite, private just in case we need to redefine
     // a shared class. We do the remap during the doit() phase of
     // the safepoint to be safer.
     if (!MetaspaceShared::remap_shared_readonly_as_readwrite()) {
       RC_TRACE_WITH_THREAD(0x00000001, thread,
         ("failed to remap shared readonly space to readwrite, private"));
       _res = JVMTI_ERROR_INTERNAL;
       return;
     }
   }
   // Mark methods seen on stack and everywhere else so old methods are not
   // cleaned up if they're on the stack.
   MetadataOnStackMark md_on_stack;
   HandleMark hm(thread);   // make sure any handles created are deleted
                            // before the stack walk again.
   for (int i = 0; i < _class_count; i++) {
     redefine_single_class(_class_defs[i].klass, _scratch_classes[i], thread);
     ClassLoaderData* cld = _scratch_classes[i]->class_loader_data();
     // Free the memory for this class at class unloading time.  Not before
     // because CMS might think this is still live.
     cld->add_to_deallocate_list((InstanceKlass*)_scratch_classes[i]);
     _scratch_classes[i] = NULL;
   }
   // Disable any dependent concurrent compilations
   SystemDictionary::notice_modification();
   // Set flag indicating that some invariants are no longer true.
   // See jvmtiExport.hpp for detailed explanation.
   JvmtiExport::set_has_redefined_a_class();
 #ifdef ASSERT
   SystemDictionary::classes_do(check_class, thread);
 #endif
 }
 void VM_RedefineClasses::doit_epilogue() {
   // Free os::malloc allocated memory.
   os::free(_scratch_classes);
   if (RC_TRACE_ENABLED(0x00000004)) {
     // Used to have separate timers for "doit" and "all", but the timer
     // overhead skewed the measurements.
     jlong doit_time = _timer_rsc_phase1.milliseconds() +
                       _timer_rsc_phase2.milliseconds();
     jlong all_time = _timer_vm_op_prologue.milliseconds() + doit_time;
     RC_TRACE(0x00000004, ("vm_op: all=" UINT64_FORMAT
       "  prologue=" UINT64_FORMAT "  doit=" UINT64_FORMAT, all_time,
       _timer_vm_op_prologue.milliseconds(), doit_time));
     RC_TRACE(0x00000004,
       ("redefine_single_class: phase1=" UINT64_FORMAT "  phase2=" UINT64_FORMAT,
        _timer_rsc_phase1.milliseconds(), _timer_rsc_phase2.milliseconds()));
   }
 }
 bool VM_RedefineClasses::is_modifiable_class(oop klass_mirror) {
   // classes for primitives cannot be redefined
   if (java_lang_Class::is_primitive(klass_mirror)) {
     return false;
   }
   Klass* the_class_oop = java_lang_Class::as_Klass(klass_mirror);
   // classes for arrays cannot be redefined
   if (the_class_oop == NULL || !Klass::cast(the_class_oop)->oop_is_instance()) {
     return false;
   }
   return true;
 }
 // Append the current entry at scratch_i in scratch_cp to *merge_cp_p
 // where the end of *merge_cp_p is specified by *merge_cp_length_p. For
 // direct CP entries, there is just the current entry to append. For
 // indirect and double-indirect CP entries, there are zero or more
 // referenced CP entries along with the current entry to append.
 // Indirect and double-indirect CP entries are handled by recursive
 // calls to append_entry() as needed. The referenced CP entries are
 // always appended to *merge_cp_p before the referee CP entry. These
 // referenced CP entries may already exist in *merge_cp_p in which case
 // there is nothing extra to append and only the current entry is
 // appended.
 void VM_RedefineClasses::append_entry(constantPoolHandle scratch_cp,
        int scratch_i, constantPoolHandle *merge_cp_p, int *merge_cp_length_p,
        TRAPS) {
   // append is different depending on entry tag type
   switch (scratch_cp->tag_at(scratch_i).value()) {
     // The old verifier is implemented outside the VM. It loads classes,
     // but does not resolve constant pool entries directly so we never
     // see Class entries here with the old verifier. Similarly the old
     // verifier does not like Class entries in the input constant pool.
     // The split-verifier is implemented in the VM so it can optionally
     // and directly resolve constant pool entries to load classes. The
     // split-verifier can accept either Class entries or UnresolvedClass
     // entries in the input constant pool. We revert the appended copy
     // back to UnresolvedClass so that either verifier will be happy
     // with the constant pool entry.
     case JVM_CONSTANT_Class:
     {
       // revert the copy to JVM_CONSTANT_UnresolvedClass
       (*merge_cp_p)->unresolved_klass_at_put(*merge_cp_length_p,
         scratch_cp->klass_name_at(scratch_i));
       if (scratch_i != *merge_cp_length_p) {
         // The new entry in *merge_cp_p is at a different index than
         // the new entry in scratch_cp so we need to map the index values.
         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
       }
       (*merge_cp_length_p)++;
     } break;
     // these are direct CP entries so they can be directly appended,
     // but double and long take two constant pool entries
     case JVM_CONSTANT_Double:  // fall through
     case JVM_CONSTANT_Long:
     {
       ConstantPool::copy_entry_to(scratch_cp, scratch_i, *merge_cp_p, *merge_cp_length_p,
         THREAD);
       if (scratch_i != *merge_cp_length_p) {
         // The new entry in *merge_cp_p is at a different index than
         // the new entry in scratch_cp so we need to map the index values.
         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
       }
       (*merge_cp_length_p) += 2;
     } break;
     // these are direct CP entries so they can be directly appended
     case JVM_CONSTANT_Float:   // fall through
     case JVM_CONSTANT_Integer: // fall through
     case JVM_CONSTANT_Utf8:    // fall through
     // This was an indirect CP entry, but it has been changed into
     // Symbol*s so this entry can be directly appended.
     case JVM_CONSTANT_String:      // fall through
     // These were indirect CP entries, but they have been changed into
     // Symbol*s so these entries can be directly appended.
     case JVM_CONSTANT_UnresolvedClass:  // fall through
     {
       ConstantPool::copy_entry_to(scratch_cp, scratch_i, *merge_cp_p, *merge_cp_length_p,
         THREAD);
       if (scratch_i != *merge_cp_length_p) {
         // The new entry in *merge_cp_p is at a different index than
         // the new entry in scratch_cp so we need to map the index values.
         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
       }
       (*merge_cp_length_p)++;
     } break;
     // this is an indirect CP entry so it needs special handling
     case JVM_CONSTANT_NameAndType:
     {
       int name_ref_i = scratch_cp->name_ref_index_at(scratch_i);
       int new_name_ref_i = 0;
       bool match = (name_ref_i < *merge_cp_length_p) &&
         scratch_cp->compare_entry_to(name_ref_i, *merge_cp_p, name_ref_i,
           THREAD);
       if (!match) {
         // forward reference in *merge_cp_p or not a direct match
         int found_i = scratch_cp->find_matching_entry(name_ref_i, *merge_cp_p,
           THREAD);
         if (found_i != 0) {
           guarantee(found_i != name_ref_i,
             "compare_entry_to() and find_matching_entry() do not agree");
           // Found a matching entry somewhere else in *merge_cp_p so
           // just need a mapping entry.
           new_name_ref_i = found_i;
           map_index(scratch_cp, name_ref_i, found_i);
         } else {
           // no match found so we have to append this entry to *merge_cp_p
           append_entry(scratch_cp, name_ref_i, merge_cp_p, merge_cp_length_p,
             THREAD);
           // The above call to append_entry() can only append one entry
           // so the post call query of *merge_cp_length_p is only for
           // the sake of consistency.
           new_name_ref_i = *merge_cp_length_p - 1;
         }
       }
       int signature_ref_i = scratch_cp->signature_ref_index_at(scratch_i);
       int new_signature_ref_i = 0;
       match = (signature_ref_i < *merge_cp_length_p) &&
         scratch_cp->compare_entry_to(signature_ref_i, *merge_cp_p,
           signature_ref_i, THREAD);
       if (!match) {
         // forward reference in *merge_cp_p or not a direct match
         int found_i = scratch_cp->find_matching_entry(signature_ref_i,
           *merge_cp_p, THREAD);
         if (found_i != 0) {
           guarantee(found_i != signature_ref_i,
             "compare_entry_to() and find_matching_entry() do not agree");
           // Found a matching entry somewhere else in *merge_cp_p so
           // just need a mapping entry.
           new_signature_ref_i = found_i;
           map_index(scratch_cp, signature_ref_i, found_i);
         } else {
           // no match found so we have to append this entry to *merge_cp_p
           append_entry(scratch_cp, signature_ref_i, merge_cp_p,
             merge_cp_length_p, THREAD);
           // The above call to append_entry() can only append one entry
           // so the post call query of *merge_cp_length_p is only for
           // the sake of consistency.
           new_signature_ref_i = *merge_cp_length_p - 1;
         }
       }
       // If the referenced entries already exist in *merge_cp_p, then
       // both new_name_ref_i and new_signature_ref_i will both be 0.
       // In that case, all we are appending is the current entry.
       if (new_name_ref_i == 0) {
         new_name_ref_i = name_ref_i;
       } else {
         RC_TRACE(0x00080000,
           ("NameAndType entry@%d name_ref_index change: %d to %d",
           *merge_cp_length_p, name_ref_i, new_name_ref_i));
       }
       if (new_signature_ref_i == 0) {
         new_signature_ref_i = signature_ref_i;
       } else {
         RC_TRACE(0x00080000,
           ("NameAndType entry@%d signature_ref_index change: %d to %d",
           *merge_cp_length_p, signature_ref_i, new_signature_ref_i));
       }
       (*merge_cp_p)->name_and_type_at_put(*merge_cp_length_p,
         new_name_ref_i, new_signature_ref_i);
       if (scratch_i != *merge_cp_length_p) {
         // The new entry in *merge_cp_p is at a different index than
         // the new entry in scratch_cp so we need to map the index values.
         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
       }
       (*merge_cp_length_p)++;
     } break;
     // this is a double-indirect CP entry so it needs special handling
     case JVM_CONSTANT_Fieldref:           // fall through
     case JVM_CONSTANT_InterfaceMethodref: // fall through
     case JVM_CONSTANT_Methodref:
     {
       int klass_ref_i = scratch_cp->uncached_klass_ref_index_at(scratch_i);
       int new_klass_ref_i = 0;
       bool match = (klass_ref_i < *merge_cp_length_p) &&
         scratch_cp->compare_entry_to(klass_ref_i, *merge_cp_p, klass_ref_i,
           THREAD);
       if (!match) {
         // forward reference in *merge_cp_p or not a direct match
         int found_i = scratch_cp->find_matching_entry(klass_ref_i, *merge_cp_p,
           THREAD);
         if (found_i != 0) {
           guarantee(found_i != klass_ref_i,
             "compare_entry_to() and find_matching_entry() do not agree");
           // Found a matching entry somewhere else in *merge_cp_p so
           // just need a mapping entry.
           new_klass_ref_i = found_i;
           map_index(scratch_cp, klass_ref_i, found_i);
         } else {
           // no match found so we have to append this entry to *merge_cp_p
           append_entry(scratch_cp, klass_ref_i, merge_cp_p, merge_cp_length_p,
             THREAD);
           // The above call to append_entry() can only append one entry
           // so the post call query of *merge_cp_length_p is only for
           // the sake of consistency. Without the optimization where we
           // use JVM_CONSTANT_UnresolvedClass, then up to two entries
           // could be appended.
           new_klass_ref_i = *merge_cp_length_p - 1;
         }
       }
       int name_and_type_ref_i =
         scratch_cp->uncached_name_and_type_ref_index_at(scratch_i);
       int new_name_and_type_ref_i = 0;
       match = (name_and_type_ref_i < *merge_cp_length_p) &&
         scratch_cp->compare_entry_to(name_and_type_ref_i, *merge_cp_p,
           name_and_type_ref_i, THREAD);
       if (!match) {
         // forward reference in *merge_cp_p or not a direct match
         int found_i = scratch_cp->find_matching_entry(name_and_type_ref_i,
           *merge_cp_p, THREAD);
         if (found_i != 0) {
           guarantee(found_i != name_and_type_ref_i,
             "compare_entry_to() and find_matching_entry() do not agree");
           // Found a matching entry somewhere else in *merge_cp_p so
           // just need a mapping entry.
           new_name_and_type_ref_i = found_i;
           map_index(scratch_cp, name_and_type_ref_i, found_i);
         } else {
           // no match found so we have to append this entry to *merge_cp_p
           append_entry(scratch_cp, name_and_type_ref_i, merge_cp_p,
             merge_cp_length_p, THREAD);
           // The above call to append_entry() can append more than
           // one entry so the post call query of *merge_cp_length_p
           // is required in order to get the right index for the
           // JVM_CONSTANT_NameAndType entry.
           new_name_and_type_ref_i = *merge_cp_length_p - 1;
         }
       }
       // If the referenced entries already exist in *merge_cp_p, then
       // both new_klass_ref_i and new_name_and_type_ref_i will both be
       // 0. In that case, all we are appending is the current entry.
       if (new_klass_ref_i == 0) {
         new_klass_ref_i = klass_ref_i;
       }
       if (new_name_and_type_ref_i == 0) {
         new_name_and_type_ref_i = name_and_type_ref_i;
       }
       const char *entry_name;
       switch (scratch_cp->tag_at(scratch_i).value()) {
       case JVM_CONSTANT_Fieldref:
         entry_name = "Fieldref";
         (*merge_cp_p)->field_at_put(*merge_cp_length_p, new_klass_ref_i,
           new_name_and_type_ref_i);
         break;
       case JVM_CONSTANT_InterfaceMethodref:
         entry_name = "IFMethodref";
         (*merge_cp_p)->interface_method_at_put(*merge_cp_length_p,
           new_klass_ref_i, new_name_and_type_ref_i);
         break;
       case JVM_CONSTANT_Methodref:
         entry_name = "Methodref";
         (*merge_cp_p)->method_at_put(*merge_cp_length_p, new_klass_ref_i,
           new_name_and_type_ref_i);
         break;
       default:
         guarantee(false, "bad switch");
         break;
       }
       if (klass_ref_i != new_klass_ref_i) {
         RC_TRACE(0x00080000, ("%s entry@%d class_index changed: %d to %d",
           entry_name, *merge_cp_length_p, klass_ref_i, new_klass_ref_i));
       }
       if (name_and_type_ref_i != new_name_and_type_ref_i) {
         RC_TRACE(0x00080000,
           ("%s entry@%d name_and_type_index changed: %d to %d",
           entry_name, *merge_cp_length_p, name_and_type_ref_i,
           new_name_and_type_ref_i));
       }
       if (scratch_i != *merge_cp_length_p) {
         // The new entry in *merge_cp_p is at a different index than
         // the new entry in scratch_cp so we need to map the index values.
         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
       }
       (*merge_cp_length_p)++;
     } break;
     // At this stage, Class or UnresolvedClass could be here, but not
     // ClassIndex
     case JVM_CONSTANT_ClassIndex: // fall through
     // Invalid is used as the tag for the second constant pool entry
     // occupied by JVM_CONSTANT_Double or JVM_CONSTANT_Long. It should
     // not be seen by itself.
     case JVM_CONSTANT_Invalid: // fall through
     // At this stage, String could be here, but not StringIndex
     case JVM_CONSTANT_StringIndex: // fall through
     // At this stage JVM_CONSTANT_UnresolvedClassInError should not be
     // here
     case JVM_CONSTANT_UnresolvedClassInError: // fall through
     default:
     {
       // leave a breadcrumb
       jbyte bad_value = scratch_cp->tag_at(scratch_i).value();
       ShouldNotReachHere();
     } break;
   } // end switch tag value
 } // end append_entry()
 void VM_RedefineClasses::swap_all_method_annotations(int i, int j, instanceKlassHandle scratch_class, TRAPS) {
   AnnotationArray* save;
   Annotations* sca = scratch_class->annotations();
   if (sca == NULL) return;
   save = sca->get_method_annotations_of(i);
   sca->set_method_annotations_of(scratch_class, i, sca->get_method_annotations_of(j), CHECK);
   sca->set_method_annotations_of(scratch_class, j, save, CHECK);
   save = sca->get_method_parameter_annotations_of(i);
   sca->set_method_parameter_annotations_of(scratch_class, i, sca->get_method_parameter_annotations_of(j), CHECK);
   sca->set_method_parameter_annotations_of(scratch_class, j, save, CHECK);
   save = sca->get_method_default_annotations_of(i);
   sca->set_method_default_annotations_of(scratch_class, i, sca->get_method_default_annotations_of(j), CHECK);
   sca->set_method_default_annotations_of(scratch_class, j, save, CHECK);
 }
 jvmtiError VM_RedefineClasses::compare_and_normalize_class_versions(
              instanceKlassHandle the_class,
              instanceKlassHandle scratch_class) {
   int i;
   // Check superclasses, or rather their names, since superclasses themselves can be
   // requested to replace.
   // Check for NULL superclass first since this might be java.lang.Object
   if (the_class->super() != scratch_class->super() &&
       (the_class->super() == NULL || scratch_class->super() == NULL ||
        Klass::cast(the_class->super())->name() !=
        Klass::cast(scratch_class->super())->name())) {
     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_HIERARCHY_CHANGED;
   }
   // Check if the number, names and order of directly implemented interfaces are the same.
   // I think in principle we should just check if the sets of names of directly implemented
   // interfaces are the same, i.e. the order of declaration (which, however, if changed in the
   // .java file, also changes in .class file) should not matter. However, comparing sets is
   // technically a bit more difficult, and, more importantly, I am not sure at present that the
   // order of interfaces does not matter on the implementation level, i.e. that the VM does not
   // rely on it somewhere.
   Array<Klass*>* k_interfaces = the_class->local_interfaces();
   Array<Klass*>* k_new_interfaces = scratch_class->local_interfaces();
   int n_intfs = k_interfaces->length();
   if (n_intfs != k_new_interfaces->length()) {
     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_HIERARCHY_CHANGED;
   }
   for (i = 0; i < n_intfs; i++) {
     if (Klass::cast(k_interfaces->at(i))->name() !=
         Klass::cast(k_new_interfaces->at(i))->name()) {
       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_HIERARCHY_CHANGED;
     }
   }
   // Check whether class is in the error init state.
   if (the_class->is_in_error_state()) {
     // TBD #5057930: special error code is needed in 1.6
     return JVMTI_ERROR_INVALID_CLASS;
   }
   // Check whether class modifiers are the same.
   jushort old_flags = (jushort) the_class->access_flags().get_flags();
   jushort new_flags = (jushort) scratch_class->access_flags().get_flags();
   if (old_flags != new_flags) {
     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_MODIFIERS_CHANGED;
   }
   // Check if the number, names, types and order of fields declared in these classes
   // are the same.
   JavaFieldStream old_fs(the_class);
   JavaFieldStream new_fs(scratch_class);
   for (; !old_fs.done() && !new_fs.done(); old_fs.next(), new_fs.next()) {
     // access
     old_flags = old_fs.access_flags().as_short();
     new_flags = new_fs.access_flags().as_short();
     if ((old_flags ^ new_flags) & JVM_RECOGNIZED_FIELD_MODIFIERS) {
       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_SCHEMA_CHANGED;
     }
     // offset
     if (old_fs.offset() != new_fs.offset()) {
       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_SCHEMA_CHANGED;
     }
     // name and signature
     Symbol* name_sym1 = the_class->constants()->symbol_at(old_fs.name_index());
     Symbol* sig_sym1 = the_class->constants()->symbol_at(old_fs.signature_index());
     Symbol* name_sym2 = scratch_class->constants()->symbol_at(new_fs.name_index());
     Symbol* sig_sym2 = scratch_class->constants()->symbol_at(new_fs.signature_index());
     if (name_sym1 != name_sym2 || sig_sym1 != sig_sym2) {
       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_SCHEMA_CHANGED;
     }
   }
   // If both streams aren't done then we have a differing number of
   // fields.
   if (!old_fs.done() || !new_fs.done()) {
     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_SCHEMA_CHANGED;
   }
   // Do a parallel walk through the old and new methods. Detect
   // cases where they match (exist in both), have been added in
   // the new methods, or have been deleted (exist only in the
   // old methods).  The class file parser places methods in order
   // by method name, but does not order overloaded methods by
   // signature.  In order to determine what fate befell the methods,
   // this code places the overloaded new methods that have matching
   // old methods in the same order as the old methods and places
   // new overloaded methods at the end of overloaded methods of
   // that name. The code for this order normalization is adapted
   // from the algorithm used in InstanceKlass::find_method().
   // Since we are swapping out of order entries as we find them,
   // we only have to search forward through the overloaded methods.
   // Methods which are added and have the same name as an existing
   // method (but different signature) will be put at the end of
   // the methods with that name, and the name mismatch code will
   // handle them.
   Array<Method*>* k_old_methods(the_class->methods());
   Array<Method*>* k_new_methods(scratch_class->methods());
   int n_old_methods = k_old_methods->length();
   int n_new_methods = k_new_methods->length();
   Thread* thread = Thread::current();
   int ni = 0;
   int oi = 0;
   while (true) {
     Method* k_old_method;
     Method* k_new_method;
     enum { matched, added, deleted, undetermined } method_was = undetermined;
     if (oi >= n_old_methods) {
       if (ni >= n_new_methods) {
         break; // we've looked at everything, done
       }
       // New method at the end
       k_new_method = k_new_methods->at(ni);
       method_was = added;
     } else if (ni >= n_new_methods) {
       // Old method, at the end, is deleted
       k_old_method = k_old_methods->at(oi);
       method_was = deleted;
     } else {
       // There are more methods in both the old and new lists
       k_old_method = k_old_methods->at(oi);
       k_new_method = k_new_methods->at(ni);
       if (k_old_method->name() != k_new_method->name()) {
         // Methods are sorted by method name, so a mismatch means added
         // or deleted
         if (k_old_method->name()->fast_compare(k_new_method->name()) > 0) {
           method_was = added;
         } else {
           method_was = deleted;
         }
       } else if (k_old_method->signature() == k_new_method->signature()) {
         // Both the name and signature match
         method_was = matched;
       } else {
         // The name matches, but the signature doesn't, which means we have to
         // search forward through the new overloaded methods.
         int nj;  // outside the loop for post-loop check
         for (nj = ni + 1; nj < n_new_methods; nj++) {
           Method* m = k_new_methods->at(nj);
           if (k_old_method->name() != m->name()) {
             // reached another method name so no more overloaded methods
             method_was = deleted;
             break;
           }
           if (k_old_method->signature() == m->signature()) {
             // found a match so swap the methods
             k_new_methods->at_put(ni, m);
             k_new_methods->at_put(nj, k_new_method);
             k_new_method = m;
             method_was = matched;
             break;
           }
         }
         if (nj >= n_new_methods) {
           // reached the end without a match; so method was deleted
           method_was = deleted;
         }
       }
     }
     switch (method_was) {
     case matched:
       // methods match, be sure modifiers do too
       old_flags = (jushort) k_old_method->access_flags().get_flags();
       new_flags = (jushort) k_new_method->access_flags().get_flags();
       if ((old_flags ^ new_flags) & ~(JVM_ACC_NATIVE)) {
         return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_METHOD_MODIFIERS_CHANGED;
       }
       {
         u2 new_num = k_new_method->method_idnum();
         u2 old_num = k_old_method->method_idnum();
         if (new_num != old_num) {
           Method* idnum_owner = scratch_class->method_with_idnum(old_num);
           if (idnum_owner != NULL) {
             // There is already a method assigned this idnum -- switch them
             idnum_owner->set_method_idnum(new_num);
           }
           k_new_method->set_method_idnum(old_num);
           swap_all_method_annotations(old_num, new_num, scratch_class, thread);
            if (thread->has_pending_exception()) {
              return JVMTI_ERROR_OUT_OF_MEMORY;
            }
         }
       }
       RC_TRACE(0x00008000, ("Method matched: new: %s [%d] == old: %s [%d]",
                             k_new_method->name_and_sig_as_C_string(), ni,
                             k_old_method->name_and_sig_as_C_string(), oi));
       // advance to next pair of methods
       ++oi;
       ++ni;
       break;
     case added:
       // method added, see if it is OK
       new_flags = (jushort) k_new_method->access_flags().get_flags();
       if ((new_flags & JVM_ACC_PRIVATE) == 0
            // hack: private should be treated as final, but alas
           || (new_flags & (JVM_ACC_FINAL|JVM_ACC_STATIC)) == 0
          ) {
         // new methods must be private
         return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_METHOD_ADDED;
       }
       {
         u2 num = the_class->next_method_idnum();
         if (num == ConstMethod::UNSET_IDNUM) {
           // cannot add any more methods
           return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_METHOD_ADDED;
         }
         u2 new_num = k_new_method->method_idnum();
         Method* idnum_owner = scratch_class->method_with_idnum(num);
         if (idnum_owner != NULL) {
           // There is already a method assigned this idnum -- switch them
           idnum_owner->set_method_idnum(new_num);
         }
         k_new_method->set_method_idnum(num);
         swap_all_method_annotations(new_num, num, scratch_class, thread);
         if (thread->has_pending_exception()) {
           return JVMTI_ERROR_OUT_OF_MEMORY;
         }
       }
       RC_TRACE(0x00008000, ("Method added: new: %s [%d]",
                             k_new_method->name_and_sig_as_C_string(), ni));
       ++ni; // advance to next new method
       break;
     case deleted:
       // method deleted, see if it is OK
       old_flags = (jushort) k_old_method->access_flags().get_flags();
       if ((old_flags & JVM_ACC_PRIVATE) == 0
            // hack: private should be treated as final, but alas
           || (old_flags & (JVM_ACC_FINAL|JVM_ACC_STATIC)) == 0
          ) {
         // deleted methods must be private
         return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_METHOD_DELETED;
       }
       RC_TRACE(0x00008000, ("Method deleted: old: %s [%d]",
                             k_old_method->name_and_sig_as_C_string(), oi));
       ++oi; // advance to next old method
       break;
     default:
       ShouldNotReachHere();
     }
   }
   return JVMTI_ERROR_NONE;
 }
 // Find new constant pool index value for old constant pool index value
 // by seaching the index map. Returns zero (0) if there is no mapped
 // value for the old constant pool index.
 int VM_RedefineClasses::find_new_index(int old_index) {
   if (_index_map_count == 0) {
     // map is empty so nothing can be found
     return 0;
   }
   if (old_index < 1 || old_index >= _index_map_p->length()) {
     // The old_index is out of range so it is not mapped. This should
     // not happen in regular constant pool merging use, but it can
     // happen if a corrupt annotation is processed.
     return 0;
   }
   int value = _index_map_p->at(old_index);
   if (value == -1) {
     // the old_index is not mapped
     return 0;
   }
   return value;
 } // end find_new_index()
 // Returns true if the current mismatch is due to a resolved/unresolved
 // class pair. Otherwise, returns false.
 bool VM_RedefineClasses::is_unresolved_class_mismatch(constantPoolHandle cp1,
        int index1, constantPoolHandle cp2, int index2) {
   jbyte t1 = cp1->tag_at(index1).value();
   if (t1 != JVM_CONSTANT_Class && t1 != JVM_CONSTANT_UnresolvedClass) {
     return false;  // wrong entry type; not our special case
   }
   jbyte t2 = cp2->tag_at(index2).value();
   if (t2 != JVM_CONSTANT_Class && t2 != JVM_CONSTANT_UnresolvedClass) {
     return false;  // wrong entry type; not our special case
   }
   if (t1 == t2) {
     return false;  // not a mismatch; not our special case
   }
   char *s1 = cp1->klass_name_at(index1)->as_C_string();
   char *s2 = cp2->klass_name_at(index2)->as_C_string();
   if (strcmp(s1, s2) != 0) {
     return false;  // strings don't match; not our special case
   }
   return true;  // made it through the gauntlet; this is our special case
 } // end is_unresolved_class_mismatch()
 jvmtiError VM_RedefineClasses::load_new_class_versions(TRAPS) {
   // For consistency allocate memory using os::malloc wrapper.
   _scratch_classes = (Klass**)
     os::malloc(sizeof(Klass*) * _class_count, mtClass);
   if (_scratch_classes == NULL) {
     return JVMTI_ERROR_OUT_OF_MEMORY;
   }
   // Zero initialize the _scratch_classes array.
   for (int i = 0; i < _class_count; i++) {
     _scratch_classes[i] = NULL;
   }
   ResourceMark rm(THREAD);
   JvmtiThreadState *state = JvmtiThreadState::state_for(JavaThread::current());
   // state can only be NULL if the current thread is exiting which
   // should not happen since we're trying to do a RedefineClasses
   guarantee(state != NULL, "exiting thread calling load_new_class_versions");
   for (int i = 0; i < _class_count; i++) {
     // Create HandleMark so that any handles created while loading new class
     // versions are deleted. Constant pools are deallocated while merging
     // constant pools
     HandleMark hm(THREAD);
     oop mirror = JNIHandles::resolve_non_null(_class_defs[i].klass);
     // classes for primitives cannot be redefined
     if (!is_modifiable_class(mirror)) {
       return JVMTI_ERROR_UNMODIFIABLE_CLASS;
     }
     Klass* the_class_oop = java_lang_Class::as_Klass(mirror);
     instanceKlassHandle the_class = instanceKlassHandle(THREAD, the_class_oop);
     Symbol*  the_class_sym = the_class->name();
     // RC_TRACE_WITH_THREAD macro has an embedded ResourceMark
     RC_TRACE_WITH_THREAD(0x00000001, THREAD,
       ("loading name=%s kind=%d (avail_mem=" UINT64_FORMAT "K)",
       the_class->external_name(), _class_load_kind,
       os::available_memory() >> 10));
     ClassFileStream st((u1*) _class_defs[i].class_bytes,
       _class_defs[i].class_byte_count, (char *)"__VM_RedefineClasses__");
     // Parse the stream.
     Handle the_class_loader(THREAD, the_class->class_loader());
     Handle protection_domain(THREAD, the_class->protection_domain());
     // Set redefined class handle in JvmtiThreadState class.
     // This redefined class is sent to agent event handler for class file
     // load hook event.
     state->set_class_being_redefined(&the_class, _class_load_kind);
     Klass* k = SystemDictionary::parse_stream(the_class_sym,
                                                 the_class_loader,
                                                 protection_domain,
                                                 &st,
                                                 THREAD);
     // Clear class_being_redefined just to be sure.
     state->clear_class_being_redefined();
     // TODO: if this is retransform, and nothing changed we can skip it
     instanceKlassHandle scratch_class (THREAD, k);
     // Need to clean up allocated InstanceKlass if there's an error so assign
     // the result here. Caller deallocates all the scratch classes in case of
     // an error.
     _scratch_classes[i] = k;
     if (HAS_PENDING_EXCEPTION) {
       Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
       // RC_TRACE_WITH_THREAD macro has an embedded ResourceMark
       RC_TRACE_WITH_THREAD(0x00000002, THREAD, ("parse_stream exception: '%s'",
         ex_name->as_C_string()));
       CLEAR_PENDING_EXCEPTION;
       if (ex_name == vmSymbols::java_lang_UnsupportedClassVersionError()) {
         return JVMTI_ERROR_UNSUPPORTED_VERSION;
       } else if (ex_name == vmSymbols::java_lang_ClassFormatError()) {
         return JVMTI_ERROR_INVALID_CLASS_FORMAT;
       } else if (ex_name == vmSymbols::java_lang_ClassCircularityError()) {
         return JVMTI_ERROR_CIRCULAR_CLASS_DEFINITION;
       } else if (ex_name == vmSymbols::java_lang_NoClassDefFoundError()) {
         // The message will be "XXX (wrong name: YYY)"
         return JVMTI_ERROR_NAMES_DONT_MATCH;
       } else if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
         return JVMTI_ERROR_OUT_OF_MEMORY;
       } else {  // Just in case more exceptions can be thrown..
         return JVMTI_ERROR_FAILS_VERIFICATION;
       }
     }
     // Ensure class is linked before redefine
     if (!the_class->is_linked()) {
       the_class->link_class(THREAD);
       if (HAS_PENDING_EXCEPTION) {
         Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
         // RC_TRACE_WITH_THREAD macro has an embedded ResourceMark
         RC_TRACE_WITH_THREAD(0x00000002, THREAD, ("link_class exception: '%s'",
           ex_name->as_C_string()));
         CLEAR_PENDING_EXCEPTION;
         if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
           return JVMTI_ERROR_OUT_OF_MEMORY;
         } else {
           return JVMTI_ERROR_INTERNAL;
         }
       }
     }
     // Do the validity checks in compare_and_normalize_class_versions()
     // before verifying the byte codes. By doing these checks first, we
     // limit the number of functions that require redirection from
     // the_class to scratch_class. In particular, we don't have to
     // modify JNI GetSuperclass() and thus won't change its performance.
     jvmtiError res = compare_and_normalize_class_versions(the_class,
                        scratch_class);
     if (res != JVMTI_ERROR_NONE) {
       return res;
     }
     // verify what the caller passed us
     {
       // The bug 6214132 caused the verification to fail.
       // Information about the_class and scratch_class is temporarily
       // recorded into jvmtiThreadState. This data is used to redirect
       // the_class to scratch_class in the JVM_* functions called by the
       // verifier. Please, refer to jvmtiThreadState.hpp for the detailed
       // description.
       RedefineVerifyMark rvm(&the_class, &scratch_class, state);
       Verifier::verify(
         scratch_class, Verifier::ThrowException, true, THREAD);
     }
     if (HAS_PENDING_EXCEPTION) {
       Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
       // RC_TRACE_WITH_THREAD macro has an embedded ResourceMark
       RC_TRACE_WITH_THREAD(0x00000002, THREAD,
         ("verify_byte_codes exception: '%s'", ex_name->as_C_string()));
       CLEAR_PENDING_EXCEPTION;
       if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
         return JVMTI_ERROR_OUT_OF_MEMORY;
       } else {
         // tell the caller the bytecodes are bad
         return JVMTI_ERROR_FAILS_VERIFICATION;
       }
     }
     res = merge_cp_and_rewrite(the_class, scratch_class, THREAD);
     if (res != JVMTI_ERROR_NONE) {
       return res;
     }
     if (VerifyMergedCPBytecodes) {
       // verify what we have done during constant pool merging
       {
         RedefineVerifyMark rvm(&the_class, &scratch_class, state);
         Verifier::verify(scratch_class, Verifier::ThrowException, true, THREAD);
       }
       if (HAS_PENDING_EXCEPTION) {
         Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
         // RC_TRACE_WITH_THREAD macro has an embedded ResourceMark
         RC_TRACE_WITH_THREAD(0x00000002, THREAD,
           ("verify_byte_codes post merge-CP exception: '%s'",
           ex_name->as_C_string()));
         CLEAR_PENDING_EXCEPTION;
         if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
           return JVMTI_ERROR_OUT_OF_MEMORY;
         } else {
           // tell the caller that constant pool merging screwed up
           return JVMTI_ERROR_INTERNAL;
         }
       }
     }
     Rewriter::rewrite(scratch_class, THREAD);
     if (!HAS_PENDING_EXCEPTION) {
       Rewriter::relocate_and_link(scratch_class, THREAD);
     }
     if (HAS_PENDING_EXCEPTION) {
       Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
       CLEAR_PENDING_EXCEPTION;
       if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
         return JVMTI_ERROR_OUT_OF_MEMORY;
       } else {
         return JVMTI_ERROR_INTERNAL;
       }
     }
     // RC_TRACE_WITH_THREAD macro has an embedded ResourceMark
     RC_TRACE_WITH_THREAD(0x00000001, THREAD,
       ("loaded name=%s (avail_mem=" UINT64_FORMAT "K)",
       the_class->external_name(), os::available_memory() >> 10));
   }
   return JVMTI_ERROR_NONE;
 }
 // Map old_index to new_index as needed. scratch_cp is only needed
 // for RC_TRACE() calls.
 void VM_RedefineClasses::map_index(constantPoolHandle scratch_cp,
        int old_index, int new_index) {
   if (find_new_index(old_index) != 0) {
     // old_index is already mapped
     return;
   }
   if (old_index == new_index) {
     // no mapping is needed
     return;
   }
   _index_map_p->at_put(old_index, new_index);
   _index_map_count++;
   RC_TRACE(0x00040000, ("mapped tag %d at index %d to %d",
     scratch_cp->tag_at(old_index).value(), old_index, new_index));
 } // end map_index()
 // Merge old_cp and scratch_cp and return the results of the merge via
 // merge_cp_p. The number of entries in *merge_cp_p is returned via
 // merge_cp_length_p. The entries in old_cp occupy the same locations
 // in *merge_cp_p. Also creates a map of indices from entries in
 // scratch_cp to the corresponding entry in *merge_cp_p. Index map
 // entries are only created for entries in scratch_cp that occupy a
 // different location in *merged_cp_p.
 bool VM_RedefineClasses::merge_constant_pools(constantPoolHandle old_cp,
        constantPoolHandle scratch_cp, constantPoolHandle *merge_cp_p,
        int *merge_cp_length_p, TRAPS) {
   if (merge_cp_p == NULL) {
     assert(false, "caller must provide scratch constantPool");
     return false; // robustness
   }
   if (merge_cp_length_p == NULL) {
     assert(false, "caller must provide scratch CP length");
     return false; // robustness
   }
   // Worst case we need old_cp->length() + scratch_cp()->length(),
   // but the caller might be smart so make sure we have at least
   // the minimum.
   if ((*merge_cp_p)->length() < old_cp->length()) {
     assert(false, "merge area too small");
     return false; // robustness
   }
   RC_TRACE_WITH_THREAD(0x00010000, THREAD,
     ("old_cp_len=%d, scratch_cp_len=%d", old_cp->length(),
     scratch_cp->length()));
   {
     // Pass 0:
     // The old_cp is copied to *merge_cp_p; this means that any code
     // using old_cp does not have to change. This work looks like a
     // perfect fit for ConstantPool*::copy_cp_to(), but we need to
     // handle one special case:
     // - revert JVM_CONSTANT_Class to JVM_CONSTANT_UnresolvedClass
     // This will make verification happy.
     int old_i;  // index into old_cp
     // index zero (0) is not used in constantPools
     for (old_i = 1; old_i < old_cp->length(); old_i++) {
       // leave debugging crumb
       jbyte old_tag = old_cp->tag_at(old_i).value();
       switch (old_tag) {
       case JVM_CONSTANT_Class:
       case JVM_CONSTANT_UnresolvedClass:
         // revert the copy to JVM_CONSTANT_UnresolvedClass
         // May be resolving while calling this so do the same for
         // JVM_CONSTANT_UnresolvedClass (klass_name_at() deals with transition)
         (*merge_cp_p)->unresolved_klass_at_put(old_i,
           old_cp->klass_name_at(old_i));
         break;
       case JVM_CONSTANT_Double:
       case JVM_CONSTANT_Long:
         // just copy the entry to *merge_cp_p, but double and long take
         // two constant pool entries
         ConstantPool::copy_entry_to(old_cp, old_i, *merge_cp_p, old_i, CHECK_0);
         old_i++;
         break;
       default:
         // just copy the entry to *merge_cp_p
         ConstantPool::copy_entry_to(old_cp, old_i, *merge_cp_p, old_i, CHECK_0);
         break;
       }
     } // end for each old_cp entry
     // We don't need to sanity check that *merge_cp_length_p is within
     // *merge_cp_p bounds since we have the minimum on-entry check above.
     (*merge_cp_length_p) = old_i;
   }
   // merge_cp_len should be the same as old_cp->length() at this point
   // so this trace message is really a "warm-and-breathing" message.
   RC_TRACE_WITH_THREAD(0x00020000, THREAD,
     ("after pass 0: merge_cp_len=%d", *merge_cp_length_p));
   int scratch_i;  // index into scratch_cp
   {
     // Pass 1a:
     // Compare scratch_cp entries to the old_cp entries that we have
     // already copied to *merge_cp_p. In this pass, we are eliminating
     // exact duplicates (matching entry at same index) so we only
     // compare entries in the common indice range.
     int increment = 1;
     int pass1a_length = MIN2(old_cp->length(), scratch_cp->length());
     for (scratch_i = 1; scratch_i < pass1a_length; scratch_i += increment) {
       switch (scratch_cp->tag_at(scratch_i).value()) {
       case JVM_CONSTANT_Double:
       case JVM_CONSTANT_Long:
         // double and long take two constant pool entries
         increment = 2;
         break;
       default:
         increment = 1;
         break;
       }
       bool match = scratch_cp->compare_entry_to(scratch_i, *merge_cp_p,
         scratch_i, CHECK_0);
       if (match) {
         // found a match at the same index so nothing more to do
         continue;
       } else if (is_unresolved_class_mismatch(scratch_cp, scratch_i,
                                               *merge_cp_p, scratch_i)) {
         // The mismatch in compare_entry_to() above is because of a
         // resolved versus unresolved class entry at the same index
         // with the same string value. Since Pass 0 reverted any
         // class entries to unresolved class entries in *merge_cp_p,
         // we go with the unresolved class entry.
         continue;
       }
       int found_i = scratch_cp->find_matching_entry(scratch_i, *merge_cp_p,
         CHECK_0);
       if (found_i != 0) {
         guarantee(found_i != scratch_i,
           "compare_entry_to() and find_matching_entry() do not agree");
         // Found a matching entry somewhere else in *merge_cp_p so
         // just need a mapping entry.
         map_index(scratch_cp, scratch_i, found_i);
         continue;
       }
       // The find_matching_entry() call above could fail to find a match
       // due to a resolved versus unresolved class or string entry situation
       // like we solved above with the is_unresolved_*_mismatch() calls.
       // However, we would have to call is_unresolved_*_mismatch() over
       // all of *merge_cp_p (potentially) and that doesn't seem to be
       // worth the time.
       // No match found so we have to append this entry and any unique
       // referenced entries to *merge_cp_p.
       append_entry(scratch_cp, scratch_i, merge_cp_p, merge_cp_length_p,
         CHECK_0);
     }
   }
   RC_TRACE_WITH_THREAD(0x00020000, THREAD,
     ("after pass 1a: merge_cp_len=%d, scratch_i=%d, index_map_len=%d",
     *merge_cp_length_p, scratch_i, _index_map_count));
   if (scratch_i < scratch_cp->length()) {
     // Pass 1b:
     // old_cp is smaller than scratch_cp so there are entries in
     // scratch_cp that we have not yet processed. We take care of
     // those now.
     int increment = 1;
     for (; scratch_i < scratch_cp->length(); scratch_i += increment) {
       switch (scratch_cp->tag_at(scratch_i).value()) {
       case JVM_CONSTANT_Double:
       case JVM_CONSTANT_Long:
         // double and long take two constant pool entries
         increment = 2;
         break;
       default:
         increment = 1;
         break;
       }
       int found_i =
         scratch_cp->find_matching_entry(scratch_i, *merge_cp_p, CHECK_0);
       if (found_i != 0) {
         // Found a matching entry somewhere else in *merge_cp_p so
         // just need a mapping entry.
         map_index(scratch_cp, scratch_i, found_i);
         continue;
       }
       // No match found so we have to append this entry and any unique
       // referenced entries to *merge_cp_p.
       append_entry(scratch_cp, scratch_i, merge_cp_p, merge_cp_length_p,
         CHECK_0);
     }
     RC_TRACE_WITH_THREAD(0x00020000, THREAD,
       ("after pass 1b: merge_cp_len=%d, scratch_i=%d, index_map_len=%d",
       *merge_cp_length_p, scratch_i, _index_map_count));
   }
   return true;
 } // end merge_constant_pools()
 // Scoped object to clean up the constant pool(s) created for merging
 class MergeCPCleaner {
   ClassLoaderData*   _loader_data;
   ConstantPool*      _cp;
   ConstantPool*      _scratch_cp;
  public:
   MergeCPCleaner(ClassLoaderData* loader_data, ConstantPool* merge_cp) :
                  _loader_data(loader_data), _cp(merge_cp), _scratch_cp(NULL) {}
   ~MergeCPCleaner() {
     _loader_data->add_to_deallocate_list(_cp);
     if (_scratch_cp != NULL) {
       _loader_data->add_to_deallocate_list(_scratch_cp);
     }
   }
   void add_scratch_cp(ConstantPool* scratch_cp) { _scratch_cp = scratch_cp; }
 };
 // Merge constant pools between the_class and scratch_class and
 // potentially rewrite bytecodes in scratch_class to use the merged
 // constant pool.
 jvmtiError VM_RedefineClasses::merge_cp_and_rewrite(
              instanceKlassHandle the_class, instanceKlassHandle scratch_class,
              TRAPS) {
   // worst case merged constant pool length is old and new combined
   int merge_cp_length = the_class->constants()->length()
         + scratch_class->constants()->length();
   // Constant pools are not easily reused so we allocate a new one
   // each time.
   // merge_cp is created unsafe for concurrent GC processing.  It
   // should be marked safe before discarding it. Even though
   // garbage,  if it crosses a card boundary, it may be scanned
   // in order to find the start of the first complete object on the card.
   ClassLoaderData* loader_data = the_class->class_loader_data();
   ConstantPool* merge_cp_oop =
     ConstantPool::allocate(loader_data,
                                   merge_cp_length,
                                   THREAD);
   MergeCPCleaner cp_cleaner(loader_data, merge_cp_oop);
   HandleMark hm(THREAD);  // make sure handles are cleared before
                           // MergeCPCleaner clears out merge_cp_oop
   constantPoolHandle merge_cp(THREAD, merge_cp_oop);
   // Get constants() from the old class because it could have been rewritten
   // while we were at a safepoint allocating a new constant pool.
   constantPoolHandle old_cp(THREAD, the_class->constants());
   constantPoolHandle scratch_cp(THREAD, scratch_class->constants());
   // If the length changed, the class was redefined out from under us. Return
   // an error.
   if (merge_cp_length != the_class->constants()->length()
          + scratch_class->constants()->length()) {
     return JVMTI_ERROR_INTERNAL;
   }
   int orig_length = old_cp->orig_length();
   if (orig_length == 0) {
     // This old_cp is an actual original constant pool. We save
     // the original length in the merged constant pool so that
     // merge_constant_pools() can be more efficient. If a constant
     // pool has a non-zero orig_length() value, then that constant
     // pool was created by a merge operation in RedefineClasses.
     merge_cp->set_orig_length(old_cp->length());
   } else {
     // This old_cp is a merged constant pool from a previous
     // RedefineClasses() calls so just copy the orig_length()
     // value.
     merge_cp->set_orig_length(old_cp->orig_length());
   }
   ResourceMark rm(THREAD);
   _index_map_count = 0;
   _index_map_p = new intArray(scratch_cp->length(), -1);
   bool result = merge_constant_pools(old_cp, scratch_cp, &merge_cp,
                   &merge_cp_length, THREAD);
   if (!result) {
     // The merge can fail due to memory allocation failure or due
     // to robustness checks.
     return JVMTI_ERROR_INTERNAL;
   }
   RC_TRACE_WITH_THREAD(0x00010000, THREAD,
     ("merge_cp_len=%d, index_map_len=%d", merge_cp_length, _index_map_count));
   if (_index_map_count == 0) {
     // there is nothing to map between the new and merged constant pools
     if (old_cp->length() == scratch_cp->length()) {
       // The old and new constant pools are the same length and the
       // index map is empty. This means that the three constant pools
       // are equivalent (but not the same). Unfortunately, the new
       // constant pool has not gone through link resolution nor have
       // the new class bytecodes gone through constant pool cache
       // rewriting so we can't use the old constant pool with the new
       // class.
       // toss the merged constant pool at return
     } else if (old_cp->length() < scratch_cp->length()) {
       // The old constant pool has fewer entries than the new constant
       // pool and the index map is empty. This means the new constant
       // pool is a superset of the old constant pool. However, the old
       // class bytecodes have already gone through constant pool cache
       // rewriting so we can't use the new constant pool with the old
       // class.
       // toss the merged constant pool at return
     } else {
       // The old constant pool has more entries than the new constant
       // pool and the index map is empty. This means that both the old
       // and merged constant pools are supersets of the new constant
       // pool.
       // Replace the new constant pool with a shrunken copy of the
       // merged constant pool
       set_new_constant_pool(loader_data, scratch_class, merge_cp, merge_cp_length, THREAD);
       // The new constant pool replaces scratch_cp so have cleaner clean it up.
       // It can't be cleaned up while there are handles to it.
       cp_cleaner.add_scratch_cp(scratch_cp());
     }
   } else {
     if (RC_TRACE_ENABLED(0x00040000)) {
       // don't want to loop unless we are tracing
       int count = 0;
       for (int i = 1; i < _index_map_p->length(); i++) {
         int value = _index_map_p->at(i);
         if (value != -1) {
           RC_TRACE_WITH_THREAD(0x00040000, THREAD,
             ("index_map[%d]: old=%d new=%d", count, i, value));
           count++;
         }
       }
     }
     // We have entries mapped between the new and merged constant pools
     // so we have to rewrite some constant pool references.
     if (!rewrite_cp_refs(scratch_class, THREAD)) {
       return JVMTI_ERROR_INTERNAL;
     }
     // Replace the new constant pool with a shrunken copy of the
     // merged constant pool so now the rewritten bytecodes have
     // valid references; the previous new constant pool will get
     // GCed.
     set_new_constant_pool(loader_data, scratch_class, merge_cp, merge_cp_length, THREAD);
     // The new constant pool replaces scratch_cp so have cleaner clean it up.
     // It can't be cleaned up while there are handles to it.
     cp_cleaner.add_scratch_cp(scratch_cp());
   }
   return JVMTI_ERROR_NONE;
 } // end merge_cp_and_rewrite()
 // Rewrite constant pool references in klass scratch_class.
 bool VM_RedefineClasses::rewrite_cp_refs(instanceKlassHandle scratch_class,
        TRAPS) {
   // rewrite constant pool references in the methods:
   if (!rewrite_cp_refs_in_methods(scratch_class, THREAD)) {
     // propagate failure back to caller
     return false;
   }
   // rewrite constant pool references in the class_annotations:
   if (!rewrite_cp_refs_in_class_annotations(scratch_class, THREAD)) {
     // propagate failure back to caller
     return false;
   }
   // rewrite constant pool references in the fields_annotations:
   if (!rewrite_cp_refs_in_fields_annotations(scratch_class, THREAD)) {
     // propagate failure back to caller
     return false;
   }
   // rewrite constant pool references in the methods_annotations:
   if (!rewrite_cp_refs_in_methods_annotations(scratch_class, THREAD)) {
     // propagate failure back to caller
     return false;
   }
   // rewrite constant pool references in the methods_parameter_annotations:
   if (!rewrite_cp_refs_in_methods_parameter_annotations(scratch_class,
          THREAD)) {
     // propagate failure back to caller
     return false;
   }
   // rewrite constant pool references in the methods_default_annotations:
   if (!rewrite_cp_refs_in_methods_default_annotations(scratch_class,
          THREAD)) {
     // propagate failure back to caller
     return false;
   }
   return true;
 } // end rewrite_cp_refs()
 // Rewrite constant pool references in the methods.
 bool VM_RedefineClasses::rewrite_cp_refs_in_methods(
        instanceKlassHandle scratch_class, TRAPS) {
   Array<Method*>* methods = scratch_class->methods();
   if (methods == NULL || methods->length() == 0) {
     // no methods so nothing to do
     return true;
   }
   // rewrite constant pool references in the methods:
   for (int i = methods->length() - 1; i >= 0; i--) {
     methodHandle method(THREAD, methods->at(i));
     methodHandle new_method;
     rewrite_cp_refs_in_method(method, &new_method, CHECK_false);
     if (!new_method.is_null()) {
       // the method has been replaced so save the new method version
       methods->at_put(i, new_method());
     }
   }
   return true;
 }
 // Rewrite constant pool references in the specific method. This code
 // was adapted from Rewriter::rewrite_method().
 void VM_RedefineClasses::rewrite_cp_refs_in_method(methodHandle method,
        methodHandle *new_method_p, TRAPS) {
   *new_method_p = methodHandle();  // default is no new method
   // We cache a pointer to the bytecodes here in code_base. If GC
   // moves the Method*, then the bytecodes will also move which
   // will likely cause a crash. We create a No_Safepoint_Verifier
   // object to detect whether we pass a possible safepoint in this
   // code block.
   No_Safepoint_Verifier nsv;
   // Bytecodes and their length
   address code_base = method->code_base();
   int code_length = method->code_size();
   int bc_length;
   for (int bci = 0; bci < code_length; bci += bc_length) {
     address bcp = code_base + bci;
     Bytecodes::Code c = (Bytecodes::Code)(*bcp);
     bc_length = Bytecodes::length_for(c);
     if (bc_length == 0) {
       // More complicated bytecodes report a length of zero so
       // we have to try again a slightly different way.
       bc_length = Bytecodes::length_at(method(), bcp);
     }
     assert(bc_length != 0, "impossible bytecode length");
     switch (c) {
       case Bytecodes::_ldc:
       {
         int cp_index = *(bcp + 1);
         int new_index = find_new_index(cp_index);
         if (StressLdcRewrite && new_index == 0) {
           // If we are stressing ldc -> ldc_w rewriting, then we
           // always need a new_index value.
           new_index = cp_index;
         }
         if (new_index != 0) {
           // the original index is mapped so we have more work to do
           if (!StressLdcRewrite && new_index <= max_jubyte) {
             // The new value can still use ldc instead of ldc_w
             // unless we are trying to stress ldc -> ldc_w rewriting
             RC_TRACE_WITH_THREAD(0x00080000, THREAD,
               ("%s@" INTPTR_FORMAT " old=%d, new=%d", Bytecodes::name(c),
               bcp, cp_index, new_index));
             *(bcp + 1) = new_index;
           } else {
             RC_TRACE_WITH_THREAD(0x00080000, THREAD,
               ("%s->ldc_w@" INTPTR_FORMAT " old=%d, new=%d",
               Bytecodes::name(c), bcp, cp_index, new_index));
             // the new value needs ldc_w instead of ldc
             u_char inst_buffer[4]; // max instruction size is 4 bytes
             bcp = (address)inst_buffer;
             // construct new instruction sequence
             *bcp = Bytecodes::_ldc_w;
             bcp++;
             // Rewriter::rewrite_method() does not rewrite ldc -> ldc_w.
             // See comment below for difference between put_Java_u2()
             // and put_native_u2().
             Bytes::put_Java_u2(bcp, new_index);
             Relocator rc(method, NULL /* no RelocatorListener needed */);
             methodHandle m;
             {
               Pause_No_Safepoint_Verifier pnsv(&nsv);
               // ldc is 2 bytes and ldc_w is 3 bytes
               m = rc.insert_space_at(bci, 3, inst_buffer, THREAD);
               if (m.is_null() || HAS_PENDING_EXCEPTION) {
                 guarantee(false, "insert_space_at() failed");
               }
             }
             // return the new method so that the caller can update
             // the containing class
             *new_method_p = method = m;
             // switch our bytecode processing loop from the old method
             // to the new method
             code_base = method->code_base();
             code_length = method->code_size();
             bcp = code_base + bci;
             c = (Bytecodes::Code)(*bcp);
             bc_length = Bytecodes::length_for(c);
             assert(bc_length != 0, "sanity check");
           } // end we need ldc_w instead of ldc
         } // end if there is a mapped index
       } break;
       // these bytecodes have a two-byte constant pool index
       case Bytecodes::_anewarray      : // fall through
       case Bytecodes::_checkcast      : // fall through
       case Bytecodes::_getfield       : // fall through
       case Bytecodes::_getstatic      : // fall through
       case Bytecodes::_instanceof     : // fall through
       case Bytecodes::_invokeinterface: // fall through
       case Bytecodes::_invokespecial  : // fall through
       case Bytecodes::_invokestatic   : // fall through
       case Bytecodes::_invokevirtual  : // fall through
       case Bytecodes::_ldc_w          : // fall through
       case Bytecodes::_ldc2_w         : // fall through
       case Bytecodes::_multianewarray : // fall through
       case Bytecodes::_new            : // fall through
       case Bytecodes::_putfield       : // fall through
       case Bytecodes::_putstatic      :
       {
         address p = bcp + 1;
         int cp_index = Bytes::get_Java_u2(p);
         int new_index = find_new_index(cp_index);
         if (new_index != 0) {
           // the original index is mapped so update w/ new value
           RC_TRACE_WITH_THREAD(0x00080000, THREAD,
             ("%s@" INTPTR_FORMAT " old=%d, new=%d", Bytecodes::name(c),
             bcp, cp_index, new_index));
           // Rewriter::rewrite_method() uses put_native_u2() in this
           // situation because it is reusing the constant pool index
           // location for a native index into the constantPoolCache.
           // Since we are updating the constant pool index prior to
           // verification and constantPoolCache initialization, we
           // need to keep the new index in Java byte order.
           Bytes::put_Java_u2(p, new_index);
         }
       } break;
     }
   } // end for each bytecode
 } // end rewrite_cp_refs_in_method()
 // Rewrite constant pool references in the class_annotations field.
 bool VM_RedefineClasses::rewrite_cp_refs_in_class_annotations(
        instanceKlassHandle scratch_class, TRAPS) {
   AnnotationArray* class_annotations = scratch_class->class_annotations();
   if (class_annotations == NULL || class_annotations->length() == 0) {
     // no class_annotations so nothing to do
     return true;
   }
   RC_TRACE_WITH_THREAD(0x02000000, THREAD,
     ("class_annotations length=%d", class_annotations->length()));
   int byte_i = 0;  // byte index into class_annotations
   return rewrite_cp_refs_in_annotations_typeArray(class_annotations, byte_i,
            THREAD);
 }
 // Rewrite constant pool references in an annotations typeArray. This
 // "structure" is adapted from the RuntimeVisibleAnnotations_attribute
 // that is described in section 4.8.15 of the 2nd-edition of the VM spec:
 //
 // annotations_typeArray {
 //   u2 num_annotations;
 //   annotation annotations[num_annotations];
 // }
 //
 bool VM_RedefineClasses::rewrite_cp_refs_in_annotations_typeArray(
        AnnotationArray* annotations_typeArray, int &byte_i_ref, TRAPS) {
   if ((byte_i_ref + 2) > annotations_typeArray->length()) {
     // not enough room for num_annotations field
     RC_TRACE_WITH_THREAD(0x02000000, THREAD,
       ("length() is too small for num_annotations field"));
     return false;
   }
   u2 num_annotations = Bytes::get_Java_u2((address)
                          annotations_typeArray->adr_at(byte_i_ref));
   byte_i_ref += 2;
   RC_TRACE_WITH_THREAD(0x02000000, THREAD,
     ("num_annotations=%d", num_annotations));
   int calc_num_annotations = 0;
   for (; calc_num_annotations < num_annotations; calc_num_annotations++) {
     if (!rewrite_cp_refs_in_annotation_struct(annotations_typeArray,
            byte_i_ref, THREAD)) {
       RC_TRACE_WITH_THREAD(0x02000000, THREAD,
         ("bad annotation_struct at %d", calc_num_annotations));
       // propagate failure back to caller
       return false;
     }
   }
   assert(num_annotations == calc_num_annotations, "sanity check");
   return true;
 } // end rewrite_cp_refs_in_annotations_typeArray()
 // Rewrite constant pool references in the annotation struct portion of
 // an annotations_typeArray. This "structure" is from section 4.8.15 of
 // the 2nd-edition of the VM spec:
 //
 // struct annotation {
 //   u2 type_index;
 //   u2 num_element_value_pairs;
 //   {
 //     u2 element_name_index;
 //     element_value value;
 //   } element_value_pairs[num_element_value_pairs];
 // }
 //
 bool VM_RedefineClasses::rewrite_cp_refs_in_annotation_struct(
        AnnotationArray* annotations_typeArray, int &byte_i_ref, TRAPS) {
   if ((byte_i_ref + 2 + 2) > annotations_typeArray->length()) {
     // not enough room for smallest annotation_struct
     RC_TRACE_WITH_THREAD(0x02000000, THREAD,
       ("length() is too small for annotation_struct"));
     return false;
   }
   u2 type_index = rewrite_cp_ref_in_annotation_data(annotations_typeArray,
                     byte_i_ref, "mapped old type_index=%d", THREAD);
   u2 num_element_value_pairs = Bytes::get_Java_u2((address)
                                  annotations_typeArray->adr_at(byte_i_ref));
   byte_i_ref += 2;
   RC_TRACE_WITH_THREAD(0x02000000, THREAD,
     ("type_index=%d  num_element_value_pairs=%d", type_index,
     num_element_value_pairs));
   int calc_num_element_value_pairs = 0;
   for (; calc_num_element_value_pairs < num_element_value_pairs;
        calc_num_element_value_pairs++) {
     if ((byte_i_ref + 2) > annotations_typeArray->length()) {
       // not enough room for another element_name_index, let alone
       // the rest of another component
       RC_TRACE_WITH_THREAD(0x02000000, THREAD,
         ("length() is too small for element_name_index"));
       return false;
     }
     u2 element_name_index = rewrite_cp_ref_in_annotation_data(
                               annotations_typeArray, byte_i_ref,
                               "mapped old element_name_index=%d", THREAD);
     RC_TRACE_WITH_THREAD(0x02000000, THREAD,
       ("element_name_index=%d", element_name_index));
     if (!rewrite_cp_refs_in_element_value(annotations_typeArray,
            byte_i_ref, THREAD)) {
       RC_TRACE_WITH_THREAD(0x02000000, THREAD,
         ("bad element_value at %d", calc_num_element_value_pairs));
       // propagate failure back to caller
       return false;
     }
   } // end for each component
   assert(num_element_value_pairs == calc_num_element_value_pairs,
     "sanity check");
   return true;
 } // end rewrite_cp_refs_in_annotation_struct()
 // Rewrite a constant pool reference at the current position in
 // annotations_typeArray if needed. Returns the original constant
 // pool reference if a rewrite was not needed or the new constant
 // pool reference if a rewrite was needed.
 u2 VM_RedefineClasses::rewrite_cp_ref_in_annotation_data(
      AnnotationArray* annotations_typeArray, int &byte_i_ref,
      const char * trace_mesg, TRAPS) {
   address cp_index_addr = (address)
     annotations_typeArray->adr_at(byte_i_ref);
   u2 old_cp_index = Bytes::get_Java_u2(cp_index_addr);
   u2 new_cp_index = find_new_index(old_cp_index);
   if (new_cp_index != 0) {
     RC_TRACE_WITH_THREAD(0x02000000, THREAD, (trace_mesg, old_cp_index));
     Bytes::put_Java_u2(cp_index_addr, new_cp_index);
     old_cp_index = new_cp_index;
   }
   byte_i_ref += 2;
   return old_cp_index;
 }
 // Rewrite constant pool references in the element_value portion of an
 // annotations_typeArray. This "structure" is from section 4.8.15.1 of
 // the 2nd-edition of the VM spec:
 //
 // struct element_value {
 //   u1 tag;
 //   union {
 //     u2 const_value_index;
 //     {
 //       u2 type_name_index;
 //       u2 const_name_index;
 //     } enum_const_value;
 //     u2 class_info_index;
 //     annotation annotation_value;
 //     struct {
 //       u2 num_values;
 //       element_value values[num_values];
 //     } array_value;
 //   } value;
 // }
 //
 bool VM_RedefineClasses::rewrite_cp_refs_in_element_value(
        AnnotationArray* annotations_typeArray, int &byte_i_ref, TRAPS) {
   if ((byte_i_ref + 1) > annotations_typeArray->length()) {
     // not enough room for a tag let alone the rest of an element_value
     RC_TRACE_WITH_THREAD(0x02000000, THREAD,
       ("length() is too small for a tag"));
     return false;
   }
   u1 tag = annotations_typeArray->at(byte_i_ref);
   byte_i_ref++;
   RC_TRACE_WITH_THREAD(0x02000000, THREAD, ("tag='%c'", tag));
   switch (tag) {
     // These BaseType tag values are from Table 4.2 in VM spec:
     case 'B':  // byte
     case 'C':  // char
     case 'D':  // double
     case 'F':  // float
     case 'I':  // int
     case 'J':  // long
     case 'S':  // short
     case 'Z':  // boolean
     // The remaining tag values are from Table 4.8 in the 2nd-edition of
     // the VM spec:
     case 's':
     {
       // For the above tag values (including the BaseType values),
       // value.const_value_index is right union field.
       if ((byte_i_ref + 2) > annotations_typeArray->length()) {
         // not enough room for a const_value_index
         RC_TRACE_WITH_THREAD(0x02000000, THREAD,
           ("length() is too small for a const_value_index"));
         return false;
       }
       u2 const_value_index = rewrite_cp_ref_in_annotation_data(
                                annotations_typeArray, byte_i_ref,
                                "mapped old const_value_index=%d", THREAD);
       RC_TRACE_WITH_THREAD(0x02000000, THREAD,
         ("const_value_index=%d", const_value_index));
     } break;
     case 'e':
     {
       // for the above tag value, value.enum_const_value is right union field
       if ((byte_i_ref + 4) > annotations_typeArray->length()) {
         // not enough room for a enum_const_value
         RC_TRACE_WITH_THREAD(0x02000000, THREAD,
           ("length() is too small for a enum_const_value"));
         return false;
       }
       u2 type_name_index = rewrite_cp_ref_in_annotation_data(
                              annotations_typeArray, byte_i_ref,
                              "mapped old type_name_index=%d", THREAD);
       u2 const_name_index = rewrite_cp_ref_in_annotation_data(
                               annotations_typeArray, byte_i_ref,
                               "mapped old const_name_index=%d", THREAD);
       RC_TRACE_WITH_THREAD(0x02000000, THREAD,
         ("type_name_index=%d  const_name_index=%d", type_name_index,
         const_name_index));
     } break;
     case 'c':
     {
       // for the above tag value, value.class_info_index is right union field
       if ((byte_i_ref + 2) > annotations_typeArray->length()) {
         // not enough room for a class_info_index
         RC_TRACE_WITH_THREAD(0x02000000, THREAD,
           ("length() is too small for a class_info_index"));
         return false;
       }
       u2 class_info_index = rewrite_cp_ref_in_annotation_data(
                               annotations_typeArray, byte_i_ref,
                               "mapped old class_info_index=%d", THREAD);
       RC_TRACE_WITH_THREAD(0x02000000, THREAD,
         ("class_info_index=%d", class_info_index));
     } break;
     case '@':
       // For the above tag value, value.attr_value is the right union
       // field. This is a nested annotation.
       if (!rewrite_cp_refs_in_annotation_struct(annotations_typeArray,
              byte_i_ref, THREAD)) {
         // propagate failure back to caller
         return false;
       }
       break;
     case '[':
     {
       if ((byte_i_ref + 2) > annotations_typeArray->length()) {
         // not enough room for a num_values field
         RC_TRACE_WITH_THREAD(0x02000000, THREAD,
           ("length() is too small for a num_values field"));
         return false;
       }
       // For the above tag value, value.array_value is the right union
       // field. This is an array of nested element_value.
       u2 num_values = Bytes::get_Java_u2((address)
                         annotations_typeArray->adr_at(byte_i_ref));
       byte_i_ref += 2;
       RC_TRACE_WITH_THREAD(0x02000000, THREAD, ("num_values=%d", num_values));
       int calc_num_values = 0;
       for (; calc_num_values < num_values; calc_num_values++) {
         if (!rewrite_cp_refs_in_element_value(
                annotations_typeArray, byte_i_ref, THREAD)) {
           RC_TRACE_WITH_THREAD(0x02000000, THREAD,
             ("bad nested element_value at %d", calc_num_values));
           // propagate failure back to caller
           return false;
         }
       }
       assert(num_values == calc_num_values, "sanity check");
     } break;
     default:
       RC_TRACE_WITH_THREAD(0x02000000, THREAD, ("bad tag=0x%x", tag));
       return false;
   } // end decode tag field
   return true;
 } // end rewrite_cp_refs_in_element_value()
 // Rewrite constant pool references in a fields_annotations field.
 bool VM_RedefineClasses::rewrite_cp_refs_in_fields_annotations(
        instanceKlassHandle scratch_class, TRAPS) {
   Annotations* sca = scratch_class->annotations();
   if (sca == NULL) return true;
   Array<AnnotationArray*>* fields_annotations = sca->fields_annotations();
   if (fields_annotations == NULL || fields_annotations->length() == 0) {
     // no fields_annotations so nothing to do
     return true;
   }
   RC_TRACE_WITH_THREAD(0x02000000, THREAD,
     ("fields_annotations length=%d", fields_annotations->length()));
   for (int i = 0; i < fields_annotations->length(); i++) {
     AnnotationArray* field_annotations = fields_annotations->at(i);
     if (field_annotations == NULL || field_annotations->length() == 0) {
       // this field does not have any annotations so skip it
       continue;
     }
     int byte_i = 0;  // byte index into field_annotations
     if (!rewrite_cp_refs_in_annotations_typeArray(field_annotations, byte_i,
            THREAD)) {
       RC_TRACE_WITH_THREAD(0x02000000, THREAD,
         ("bad field_annotations at %d", i));
       // propagate failure back to caller
       return false;
     }
   }
   return true;
 } // end rewrite_cp_refs_in_fields_annotations()
 // Rewrite constant pool references in a methods_annotations field.
 bool VM_RedefineClasses::rewrite_cp_refs_in_methods_annotations(
        instanceKlassHandle scratch_class, TRAPS) {
   Annotations* sca = scratch_class->annotations();
   if (sca == NULL) return true;
   Array<AnnotationArray*>* methods_annotations = sca->methods_annotations();
   if (methods_annotations == NULL || methods_annotations->length() == 0) {
     // no methods_annotations so nothing to do
     return true;
   }
   RC_TRACE_WITH_THREAD(0x02000000, THREAD,
     ("methods_annotations length=%d", methods_annotations->length()));
   for (int i = 0; i < methods_annotations->length(); i++) {
     AnnotationArray* method_annotations = methods_annotations->at(i);
     if (method_annotations == NULL || method_annotations->length() == 0) {
       // this method does not have any annotations so skip it
       continue;
     }
     int byte_i = 0;  // byte index into method_annotations
     if (!rewrite_cp_refs_in_annotations_typeArray(method_annotations, byte_i,
            THREAD)) {
       RC_TRACE_WITH_THREAD(0x02000000, THREAD,
         ("bad method_annotations at %d", i));
       // propagate failure back to caller
       return false;
     }
   }
   return true;
 } // end rewrite_cp_refs_in_methods_annotations()
 // Rewrite constant pool references in a methods_parameter_annotations
 // field. This "structure" is adapted from the
 // RuntimeVisibleParameterAnnotations_attribute described in section
 // 4.8.17 of the 2nd-edition of the VM spec:
 //
 // methods_parameter_annotations_typeArray {
 //   u1 num_parameters;
 //   {
 //     u2 num_annotations;
 //     annotation annotations[num_annotations];
 //   } parameter_annotations[num_parameters];
 // }
 //
 bool VM_RedefineClasses::rewrite_cp_refs_in_methods_parameter_annotations(
        instanceKlassHandle scratch_class, TRAPS) {
   Annotations* sca = scratch_class->annotations();
   if (sca == NULL) return true;
   Array<AnnotationArray*>* methods_parameter_annotations =
     sca->methods_parameter_annotations();
   if (methods_parameter_annotations == NULL
       || methods_parameter_annotations->length() == 0) {
     // no methods_parameter_annotations so nothing to do
     return true;
   }
   RC_TRACE_WITH_THREAD(0x02000000, THREAD,
     ("methods_parameter_annotations length=%d",
     methods_parameter_annotations->length()));
   for (int i = 0; i < methods_parameter_annotations->length(); i++) {
     AnnotationArray* method_parameter_annotations = methods_parameter_annotations->at(i);
     if (method_parameter_annotations == NULL
         || method_parameter_annotations->length() == 0) {
       // this method does not have any parameter annotations so skip it
       continue;
     }
     if (method_parameter_annotations->length() < 1) {
       // not enough room for a num_parameters field
       RC_TRACE_WITH_THREAD(0x02000000, THREAD,
         ("length() is too small for a num_parameters field at %d", i));
       return false;
     }
     int byte_i = 0;  // byte index into method_parameter_annotations
     u1 num_parameters = method_parameter_annotations->at(byte_i);
     byte_i++;
     RC_TRACE_WITH_THREAD(0x02000000, THREAD,
       ("num_parameters=%d", num_parameters));
     int calc_num_parameters = 0;
     for (; calc_num_parameters < num_parameters; calc_num_parameters++) {
       if (!rewrite_cp_refs_in_annotations_typeArray(
              method_parameter_annotations, byte_i, THREAD)) {
         RC_TRACE_WITH_THREAD(0x02000000, THREAD,
           ("bad method_parameter_annotations at %d", calc_num_parameters));
         // propagate failure back to caller
         return false;
       }
     }
     assert(num_parameters == calc_num_parameters, "sanity check");
   }
   return true;
 } // end rewrite_cp_refs_in_methods_parameter_annotations()
 // Rewrite constant pool references in a methods_default_annotations
 // field. This "structure" is adapted from the AnnotationDefault_attribute
 // that is described in section 4.8.19 of the 2nd-edition of the VM spec:
 //
 // methods_default_annotations_typeArray {
 //   element_value default_value;
 // }
 //
 bool VM_RedefineClasses::rewrite_cp_refs_in_methods_default_annotations(
        instanceKlassHandle scratch_class, TRAPS) {
   Annotations* sca = scratch_class->annotations();
   if (sca == NULL) return true;
   Array<AnnotationArray*>* methods_default_annotations =
     sca->methods_default_annotations();
   if (methods_default_annotations == NULL
       || methods_default_annotations->length() == 0) {
     // no methods_default_annotations so nothing to do
     return true;
   }
   RC_TRACE_WITH_THREAD(0x02000000, THREAD,
     ("methods_default_annotations length=%d",
     methods_default_annotations->length()));
   for (int i = 0; i < methods_default_annotations->length(); i++) {
     AnnotationArray* method_default_annotations = methods_default_annotations->at(i);
     if (method_default_annotations == NULL
         || method_default_annotations->length() == 0) {
       // this method does not have any default annotations so skip it
       continue;
     }
     int byte_i = 0;  // byte index into method_default_annotations
     if (!rewrite_cp_refs_in_element_value(
            method_default_annotations, byte_i, THREAD)) {
       RC_TRACE_WITH_THREAD(0x02000000, THREAD,
         ("bad default element_value at %d", i));
       // propagate failure back to caller
       return false;
     }
   }
   return true;
 } // end rewrite_cp_refs_in_methods_default_annotations()
 // Rewrite constant pool references in the method's stackmap table.
 // These "structures" are adapted from the StackMapTable_attribute that
 // is described in section 4.8.4 of the 6.0 version of the VM spec
 // (dated 2005.10.26):
 // file:///net/quincunx.sfbay/export/gbracha/ClassFile-Java6.pdf
 //
 // stack_map {
 //   u2 number_of_entries;
 //   stack_map_frame entries[number_of_entries];
 // }
 //
 void VM_RedefineClasses::rewrite_cp_refs_in_stack_map_table(
        methodHandle method, TRAPS) {
   if (!method->has_stackmap_table()) {
     return;
   }
   AnnotationArray* stackmap_data = method->stackmap_data();
   address stackmap_p = (address)stackmap_data->adr_at(0);
   address stackmap_end = stackmap_p + stackmap_data->length();
   assert(stackmap_p + 2 <= stackmap_end, "no room for number_of_entries");
   u2 number_of_entries = Bytes::get_Java_u2(stackmap_p);
   stackmap_p += 2;
   RC_TRACE_WITH_THREAD(0x04000000, THREAD,
     ("number_of_entries=%u", number_of_entries));
   // walk through each stack_map_frame
   u2 calc_number_of_entries = 0;
   for (; calc_number_of_entries < number_of_entries; calc_number_of_entries++) {
     // The stack_map_frame structure is a u1 frame_type followed by
     // 0 or more bytes of data:
     //
     // union stack_map_frame {
     //   same_frame;
     //   same_locals_1_stack_item_frame;
     //   same_locals_1_stack_item_frame_extended;
     //   chop_frame;
     //   same_frame_extended;
     //   append_frame;
     //   full_frame;
     // }
     assert(stackmap_p + 1 <= stackmap_end, "no room for frame_type");
     // The Linux compiler does not like frame_type to be u1 or u2. It
     // issues the following warning for the first if-statement below:
     //
     // "warning: comparison is always true due to limited range of data type"
     //
     u4 frame_type = *stackmap_p;
     stackmap_p++;
     // same_frame {
     //   u1 frame_type = SAME; /* 0-63 */
     // }
     if (frame_type >= 0 && frame_type <= 63) {
       // nothing more to do for same_frame
     }
     // same_locals_1_stack_item_frame {
     //   u1 frame_type = SAME_LOCALS_1_STACK_ITEM; /* 64-127 */
     //   verification_type_info stack[1];
     // }
     else if (frame_type >= 64 && frame_type <= 127) {
       rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
         calc_number_of_entries, frame_type, THREAD);
     }
     // reserved for future use
     else if (frame_type >= 128 && frame_type <= 246) {
       // nothing more to do for reserved frame_types
     }
     // same_locals_1_stack_item_frame_extended {
     //   u1 frame_type = SAME_LOCALS_1_STACK_ITEM_EXTENDED; /* 247 */
     //   u2 offset_delta;
     //   verification_type_info stack[1];
     // }
     else if (frame_type == 247) {
       stackmap_p += 2;
       rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
         calc_number_of_entries, frame_type, THREAD);
     }
     // chop_frame {
     //   u1 frame_type = CHOP; /* 248-250 */
     //   u2 offset_delta;
     // }
     else if (frame_type >= 248 && frame_type <= 250) {
       stackmap_p += 2;
     }
     // same_frame_extended {
     //   u1 frame_type = SAME_FRAME_EXTENDED; /* 251*/
     //   u2 offset_delta;
     // }
     else if (frame_type == 251) {
       stackmap_p += 2;
     }
     // append_frame {
     //   u1 frame_type = APPEND; /* 252-254 */
     //   u2 offset_delta;
     //   verification_type_info locals[frame_type - 251];
     // }
     else if (frame_type >= 252 && frame_type <= 254) {
       assert(stackmap_p + 2 <= stackmap_end,
         "no room for offset_delta");
       stackmap_p += 2;
       u1 len = frame_type - 251;
       for (u1 i = 0; i < len; i++) {
         rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
           calc_number_of_entries, frame_type, THREAD);
       }
     }
     // full_frame {
     //   u1 frame_type = FULL_FRAME; /* 255 */
     //   u2 offset_delta;
     //   u2 number_of_locals;
     //   verification_type_info locals[number_of_locals];
     //   u2 number_of_stack_items;
     //   verification_type_info stack[number_of_stack_items];
     // }
     else if (frame_type == 255) {
       assert(stackmap_p + 2 + 2 <= stackmap_end,
         "no room for smallest full_frame");
       stackmap_p += 2;
       u2 number_of_locals = Bytes::get_Java_u2(stackmap_p);
       stackmap_p += 2;
       for (u2 locals_i = 0; locals_i < number_of_locals; locals_i++) {
         rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
           calc_number_of_entries, frame_type, THREAD);
       }
       // Use the largest size for the number_of_stack_items, but only get
       // the right number of bytes.
       u2 number_of_stack_items = Bytes::get_Java_u2(stackmap_p);
       stackmap_p += 2;
       for (u2 stack_i = 0; stack_i < number_of_stack_items; stack_i++) {
         rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
           calc_number_of_entries, frame_type, THREAD);
       }
     }
   } // end while there is a stack_map_frame
   assert(number_of_entries == calc_number_of_entries, "sanity check");
 } // end rewrite_cp_refs_in_stack_map_table()
 // Rewrite constant pool references in the verification type info
 // portion of the method's stackmap table. These "structures" are
 // adapted from the StackMapTable_attribute that is described in
 // section 4.8.4 of the 6.0 version of the VM spec (dated 2005.10.26):
 // file:///net/quincunx.sfbay/export/gbracha/ClassFile-Java6.pdf
 //
 // The verification_type_info structure is a u1 tag followed by 0 or
 // more bytes of data:
 //
 // union verification_type_info {
 //   Top_variable_info;
 //   Integer_variable_info;
 //   Float_variable_info;
 //   Long_variable_info;
 //   Double_variable_info;
 //   Null_variable_info;
 //   UninitializedThis_variable_info;
 //   Object_variable_info;
 //   Uninitialized_variable_info;
 // }
 //
 void VM_RedefineClasses::rewrite_cp_refs_in_verification_type_info(
        address& stackmap_p_ref, address stackmap_end, u2 frame_i,
        u1 frame_type, TRAPS) {
   assert(stackmap_p_ref + 1 <= stackmap_end, "no room for tag");
   u1 tag = *stackmap_p_ref;
   stackmap_p_ref++;
   switch (tag) {
   // Top_variable_info {
   //   u1 tag = ITEM_Top; /* 0 */
   // }
   // verificationType.hpp has zero as ITEM_Bogus instead of ITEM_Top
   case 0:  // fall through
   // Integer_variable_info {
   //   u1 tag = ITEM_Integer; /* 1 */
   // }
   case ITEM_Integer:  // fall through
   // Float_variable_info {
   //   u1 tag = ITEM_Float; /* 2 */
   // }
   case ITEM_Float:  // fall through
   // Double_variable_info {
   //   u1 tag = ITEM_Double; /* 3 */
   // }
   case ITEM_Double:  // fall through
   // Long_variable_info {
   //   u1 tag = ITEM_Long; /* 4 */
   // }
   case ITEM_Long:  // fall through
   // Null_variable_info {
   //   u1 tag = ITEM_Null; /* 5 */
   // }
   case ITEM_Null:  // fall through
   // UninitializedThis_variable_info {
   //   u1 tag = ITEM_UninitializedThis; /* 6 */
   // }
   case ITEM_UninitializedThis:
     // nothing more to do for the above tag types
     break;
   // Object_variable_info {
   //   u1 tag = ITEM_Object; /* 7 */
   //   u2 cpool_index;
   // }
   case ITEM_Object:
   {
     assert(stackmap_p_ref + 2 <= stackmap_end, "no room for cpool_index");
     u2 cpool_index = Bytes::get_Java_u2(stackmap_p_ref);
     u2 new_cp_index = find_new_index(cpool_index);
     if (new_cp_index != 0) {
       RC_TRACE_WITH_THREAD(0x04000000, THREAD,
         ("mapped old cpool_index=%d", cpool_index));
       Bytes::put_Java_u2(stackmap_p_ref, new_cp_index);
       cpool_index = new_cp_index;
     }
     stackmap_p_ref += 2;
     RC_TRACE_WITH_THREAD(0x04000000, THREAD,
       ("frame_i=%u, frame_type=%u, cpool_index=%d", frame_i,
       frame_type, cpool_index));
   } break;
   // Uninitialized_variable_info {
   //   u1 tag = ITEM_Uninitialized; /* 8 */
   //   u2 offset;
   // }
   case ITEM_Uninitialized:
     assert(stackmap_p_ref + 2 <= stackmap_end, "no room for offset");
     stackmap_p_ref += 2;
     break;
   default:
     RC_TRACE_WITH_THREAD(0x04000000, THREAD,
       ("frame_i=%u, frame_type=%u, bad tag=0x%x", frame_i, frame_type, tag));
     ShouldNotReachHere();
     break;
   } // end switch (tag)
 } // end rewrite_cp_refs_in_verification_type_info()
 // Change the constant pool associated with klass scratch_class to
 // scratch_cp. If shrink is true, then scratch_cp_length elements
 // are copied from scratch_cp to a smaller constant pool and the
 // smaller constant pool is associated with scratch_class.
 void VM_RedefineClasses::set_new_constant_pool(
        ClassLoaderData* loader_data,
        instanceKlassHandle scratch_class, constantPoolHandle scratch_cp,
        int scratch_cp_length, TRAPS) {
   assert(scratch_cp->length() >= scratch_cp_length, "sanity check");
     // scratch_cp is a merged constant pool and has enough space for a
     // worst case merge situation. We want to associate the minimum
     // sized constant pool with the klass to save space.
     constantPoolHandle smaller_cp(THREAD,
     ConstantPool::allocate(loader_data, scratch_cp_length,
                                    THREAD));
     // preserve orig_length() value in the smaller copy
     int orig_length = scratch_cp->orig_length();
     assert(orig_length != 0, "sanity check");
     smaller_cp->set_orig_length(orig_length);
     scratch_cp->copy_cp_to(1, scratch_cp_length - 1, smaller_cp, 1, THREAD);
     scratch_cp = smaller_cp;
   // attach new constant pool to klass
   scratch_cp->set_pool_holder(scratch_class());
   // attach klass to new constant pool
   scratch_class->set_constants(scratch_cp());
   int i;  // for portability
   // update each field in klass to use new constant pool indices as needed
   for (JavaFieldStream fs(scratch_class); !fs.done(); fs.next()) {
     jshort cur_index = fs.name_index();
     jshort new_index = find_new_index(cur_index);
     if (new_index != 0) {
       RC_TRACE_WITH_THREAD(0x00080000, THREAD,
         ("field-name_index change: %d to %d", cur_index, new_index));
       fs.set_name_index(new_index);
     }
     cur_index = fs.signature_index();
     new_index = find_new_index(cur_index);
     if (new_index != 0) {
       RC_TRACE_WITH_THREAD(0x00080000, THREAD,
         ("field-signature_index change: %d to %d", cur_index, new_index));
       fs.set_signature_index(new_index);
     }
     cur_index = fs.initval_index();
     new_index = find_new_index(cur_index);
     if (new_index != 0) {
       RC_TRACE_WITH_THREAD(0x00080000, THREAD,
         ("field-initval_index change: %d to %d", cur_index, new_index));
       fs.set_initval_index(new_index);
     }
     cur_index = fs.generic_signature_index();
     new_index = find_new_index(cur_index);
     if (new_index != 0) {
       RC_TRACE_WITH_THREAD(0x00080000, THREAD,
         ("field-generic_signature change: %d to %d", cur_index, new_index));
       fs.set_generic_signature_index(new_index);
     }
   } // end for each field
   // Update constant pool indices in the inner classes info to use
   // new constant indices as needed. The inner classes info is a
   // quadruple:
   // (inner_class_info, outer_class_info, inner_name, inner_access_flags)
   InnerClassesIterator iter(scratch_class);
   for (; !iter.done(); iter.next()) {
     int cur_index = iter.inner_class_info_index();
     if (cur_index == 0) {
       continue;  // JVM spec. allows null inner class refs so skip it
     }
     int new_index = find_new_index(cur_index);
     if (new_index != 0) {
       RC_TRACE_WITH_THREAD(0x00080000, THREAD,
         ("inner_class_info change: %d to %d", cur_index, new_index));
       iter.set_inner_class_info_index(new_index);
     }
     cur_index = iter.outer_class_info_index();
     new_index = find_new_index(cur_index);
     if (new_index != 0) {
       RC_TRACE_WITH_THREAD(0x00080000, THREAD,
         ("outer_class_info change: %d to %d", cur_index, new_index));
       iter.set_outer_class_info_index(new_index);
     }
     cur_index = iter.inner_name_index();
     new_index = find_new_index(cur_index);
     if (new_index != 0) {
       RC_TRACE_WITH_THREAD(0x00080000, THREAD,
         ("inner_name change: %d to %d", cur_index, new_index));
       iter.set_inner_name_index(new_index);
     }
   } // end for each inner class
   // Attach each method in klass to the new constant pool and update
   // to use new constant pool indices as needed:
   Array<Method*>* methods = scratch_class->methods();
   for (i = methods->length() - 1; i >= 0; i--) {
     methodHandle method(THREAD, methods->at(i));
     method->set_constants(scratch_cp());
     int new_index = find_new_index(method->name_index());
     if (new_index != 0) {
       RC_TRACE_WITH_THREAD(0x00080000, THREAD,
         ("method-name_index change: %d to %d", method->name_index(),
         new_index));
       method->set_name_index(new_index);
     }
     new_index = find_new_index(method->signature_index());
     if (new_index != 0) {
       RC_TRACE_WITH_THREAD(0x00080000, THREAD,
         ("method-signature_index change: %d to %d",
         method->signature_index(), new_index));
       method->set_signature_index(new_index);
     }
     new_index = find_new_index(method->generic_signature_index());
     if (new_index != 0) {
       RC_TRACE_WITH_THREAD(0x00080000, THREAD,
         ("method-generic_signature_index change: %d to %d",
         method->generic_signature_index(), new_index));
       method->set_generic_signature_index(new_index);
     }
     // Update constant pool indices in the method's checked exception
     // table to use new constant indices as needed.
     int cext_length = method->checked_exceptions_length();
     if (cext_length > 0) {
       CheckedExceptionElement * cext_table =
         method->checked_exceptions_start();
       for (int j = 0; j < cext_length; j++) {
         int cur_index = cext_table[j].class_cp_index;
         int new_index = find_new_index(cur_index);
         if (new_index != 0) {
           RC_TRACE_WITH_THREAD(0x00080000, THREAD,
             ("cext-class_cp_index change: %d to %d", cur_index, new_index));
           cext_table[j].class_cp_index = (u2)new_index;
         }
       } // end for each checked exception table entry
     } // end if there are checked exception table entries
     // Update each catch type index in the method's exception table
     // to use new constant pool indices as needed. The exception table
     // holds quadruple entries of the form:
     //   (beg_bci, end_bci, handler_bci, klass_index)
     ExceptionTable ex_table(method());
     int ext_length = ex_table.length();
     for (int j = 0; j < ext_length; j ++) {
       int cur_index = ex_table.catch_type_index(j);
       int new_index = find_new_index(cur_index);
       if (new_index != 0) {
         RC_TRACE_WITH_THREAD(0x00080000, THREAD,
           ("ext-klass_index change: %d to %d", cur_index, new_index));
         ex_table.set_catch_type_index(j, new_index);
       }
     } // end for each exception table entry
     // Update constant pool indices in the method's local variable
     // table to use new constant indices as needed. The local variable
     // table hold sextuple entries of the form:
     // (start_pc, length, name_index, descriptor_index, signature_index, slot)
     int lvt_length = method->localvariable_table_length();
     if (lvt_length > 0) {
       LocalVariableTableElement * lv_table =
         method->localvariable_table_start();
       for (int j = 0; j < lvt_length; j++) {
         int cur_index = lv_table[j].name_cp_index;
         int new_index = find_new_index(cur_index);
         if (new_index != 0) {
           RC_TRACE_WITH_THREAD(0x00080000, THREAD,
             ("lvt-name_cp_index change: %d to %d", cur_index, new_index));
           lv_table[j].name_cp_index = (u2)new_index;
         }
         cur_index = lv_table[j].descriptor_cp_index;
         new_index = find_new_index(cur_index);
         if (new_index != 0) {
           RC_TRACE_WITH_THREAD(0x00080000, THREAD,
             ("lvt-descriptor_cp_index change: %d to %d", cur_index,
             new_index));
           lv_table[j].descriptor_cp_index = (u2)new_index;
         }
         cur_index = lv_table[j].signature_cp_index;
         new_index = find_new_index(cur_index);
         if (new_index != 0) {
           RC_TRACE_WITH_THREAD(0x00080000, THREAD,
             ("lvt-signature_cp_index change: %d to %d", cur_index, new_index));
           lv_table[j].signature_cp_index = (u2)new_index;
         }
       } // end for each local variable table entry
     } // end if there are local variable table entries
     rewrite_cp_refs_in_stack_map_table(method, THREAD);
   } // end for each method
 } // end set_new_constant_pool()
 void VM_RedefineClasses::adjust_array_vtable(Klass* k_oop) {
   arrayKlass* ak = arrayKlass::cast(k_oop);
   bool trace_name_printed = false;
   ak->vtable()->adjust_method_entries(_matching_old_methods,
                                       _matching_new_methods,
                                       _matching_methods_length,
                                       &trace_name_printed);
 }
 // Unevolving classes may point to methods of the_class directly
 // from their constant pool caches, itables, and/or vtables. We
 // use the SystemDictionary::classes_do() facility and this helper
 // to fix up these pointers.
 //
 // Note: We currently don't support updating the vtable in
 // arrayKlassOops. See Open Issues in jvmtiRedefineClasses.hpp.
 void VM_RedefineClasses::adjust_cpool_cache_and_vtable(Klass* k_oop,
        ClassLoaderData* initiating_loader,
        TRAPS) {
   Klass *k = k_oop;
   if (k->oop_is_instance()) {
     HandleMark hm(THREAD);
     InstanceKlass *ik = (InstanceKlass *) k;
     // HotSpot specific optimization! HotSpot does not currently
     // support delegation from the bootstrap class loader to a
     // user-defined class loader. This means that if the bootstrap
     // class loader is the initiating class loader, then it will also
     // be the defining class loader. This also means that classes
     // loaded by the bootstrap class loader cannot refer to classes
     // loaded by a user-defined class loader. Note: a user-defined
     // class loader can delegate to the bootstrap class loader.
     //
     // If the current class being redefined has a user-defined class
     // loader as its defining class loader, then we can skip all
     // classes loaded by the bootstrap class loader.
     bool is_user_defined =
            InstanceKlass::cast(_the_class_oop)->class_loader() != NULL;
     if (is_user_defined && ik->class_loader() == NULL) {
       return;
     }
     // If the class being redefined is java.lang.Object, we need to fix all
     // array class vtables also
     if (_the_class_oop == SystemDictionary::Object_klass()) {
       ik->array_klasses_do(adjust_array_vtable);
     }
     // This is a very busy routine. We don't want too much tracing
     // printed out.
     bool trace_name_printed = false;
     // Very noisy: only enable this call if you are trying to determine
     // that a specific class gets found by this routine.
     // RC_TRACE macro has an embedded ResourceMark
     // RC_TRACE_WITH_THREAD(0x00100000, THREAD,
     //   ("adjust check: name=%s", ik->external_name()));
     // trace_name_printed = true;
     // Fix the vtable embedded in the_class and subclasses of the_class,
     // if one exists. We discard scratch_class and we don't keep an
     // InstanceKlass around to hold obsolete methods so we don't have
     // any other InstanceKlass embedded vtables to update. The vtable
     // holds the Method*s for virtual (but not final) methods.
     if (ik->vtable_length() > 0 && ik->is_subtype_of(_the_class_oop)) {
       // ik->vtable() creates a wrapper object; rm cleans it up
       ResourceMark rm(THREAD);
       ik->vtable()->adjust_method_entries(_matching_old_methods,
                                           _matching_new_methods,
                                           _matching_methods_length,
                                           &trace_name_printed);
     }
     // If the current class has an itable and we are either redefining an
     // interface or if the current class is a subclass of the_class, then
     // we potentially have to fix the itable. If we are redefining an
     // interface, then we have to call adjust_method_entries() for
     // every InstanceKlass that has an itable since there isn't a
     // subclass relationship between an interface and an InstanceKlass.
     if (ik->itable_length() > 0 && (Klass::cast(_the_class_oop)->is_interface()
         || ik->is_subclass_of(_the_class_oop))) {
       // ik->itable() creates a wrapper object; rm cleans it up
       ResourceMark rm(THREAD);
       ik->itable()->adjust_method_entries(_matching_old_methods,
                                           _matching_new_methods,
                                           _matching_methods_length,
                                           &trace_name_printed);
     }
     // The constant pools in other classes (other_cp) can refer to
     // methods in the_class. We have to update method information in
     // other_cp's cache. If other_cp has a previous version, then we
     // have to repeat the process for each previous version. The
     // constant pool cache holds the Method*s for non-virtual
     // methods and for virtual, final methods.
     //
     // Special case: if the current class is the_class, then new_cp
     // has already been attached to the_class and old_cp has already
     // been added as a previous version. The new_cp doesn't have any
     // cached references to old methods so it doesn't need to be
     // updated. We can simply start with the previous version(s) in
     // that case.
     constantPoolHandle other_cp;
     ConstantPoolCache* cp_cache;
     if (k_oop != _the_class_oop) {
       // this klass' constant pool cache may need adjustment
       other_cp = constantPoolHandle(ik->constants());
       cp_cache = other_cp->cache();
       if (cp_cache != NULL) {
         cp_cache->adjust_method_entries(_matching_old_methods,
                                         _matching_new_methods,
                                         _matching_methods_length,
                                         &trace_name_printed);
       }
     }
     {
       ResourceMark rm(THREAD);
       // PreviousVersionInfo objects returned via PreviousVersionWalker
       // contain a GrowableArray of handles. We have to clean up the
       // GrowableArray _after_ the PreviousVersionWalker destructor
       // has destroyed the handles.
       {
         // the previous versions' constant pool caches may need adjustment
         PreviousVersionWalker pvw(ik);
         for (PreviousVersionInfo * pv_info = pvw.next_previous_version();
              pv_info != NULL; pv_info = pvw.next_previous_version()) {
           other_cp = pv_info->prev_constant_pool_handle();
           cp_cache = other_cp->cache();
           if (cp_cache != NULL) {
             cp_cache->adjust_method_entries(_matching_old_methods,
                                             _matching_new_methods,
                                             _matching_methods_length,
                                             &trace_name_printed);
           }
         }
       } // pvw is cleaned up
     } // rm is cleaned up
   }
 }
 void VM_RedefineClasses::update_jmethod_ids() {
   for (int j = 0; j < _matching_methods_length; ++j) {
     Method* old_method = _matching_old_methods[j];
     jmethodID jmid = old_method->find_jmethod_id_or_null();
     if (jmid != NULL) {
       // There is a jmethodID, change it to point to the new method
       methodHandle new_method_h(_matching_new_methods[j]);
       Method::change_method_associated_with_jmethod_id(jmid, new_method_h());
       assert(Method::resolve_jmethod_id(jmid) == _matching_new_methods[j],
              "should be replaced");
     }
   }
 }
 void VM_RedefineClasses::check_methods_and_mark_as_obsolete(
        BitMap *emcp_methods, int * emcp_method_count_p) {
   *emcp_method_count_p = 0;
   int obsolete_count = 0;
   int old_index = 0;
   for (int j = 0; j < _matching_methods_length; ++j, ++old_index) {
     Method* old_method = _matching_old_methods[j];
     Method* new_method = _matching_new_methods[j];
     Method* old_array_method;
     // Maintain an old_index into the _old_methods array by skipping
     // deleted methods
     while ((old_array_method = _old_methods->at(old_index)) != old_method) {
       ++old_index;
     }
     if (MethodComparator::methods_EMCP(old_method, new_method)) {
       // The EMCP definition from JSR-163 requires the bytecodes to be
       // the same with the exception of constant pool indices which may
       // differ. However, the constants referred to by those indices
       // must be the same.
       //
       // We use methods_EMCP() for comparison since constant pool
       // merging can remove duplicate constant pool entries that were
       // present in the old method and removed from the rewritten new
       // method. A faster binary comparison function would consider the
       // old and new methods to be different when they are actually
       // EMCP.
       //
       // The old and new methods are EMCP and you would think that we
       // could get rid of one of them here and now and save some space.
       // However, the concept of EMCP only considers the bytecodes and
       // the constant pool entries in the comparison. Other things,
       // e.g., the line number table (LNT) or the local variable table
       // (LVT) don't count in the comparison. So the new (and EMCP)
       // method can have a new LNT that we need so we can't just
       // overwrite the new method with the old method.
       //
       // When this routine is called, we have already attached the new
       // methods to the_class so the old methods are effectively
       // overwritten. However, if an old method is still executing,
       // then the old method cannot be collected until sometime after
       // the old method call has returned. So the overwriting of old
       // methods by new methods will save us space except for those
       // (hopefully few) old methods that are still executing.
       //
       // A method refers to a ConstMethod* and this presents another
       // possible avenue to space savings. The ConstMethod* in the
       // new method contains possibly new attributes (LNT, LVT, etc).
       // At first glance, it seems possible to save space by replacing
       // the ConstMethod* in the old method with the ConstMethod*
       // from the new method. The old and new methods would share the
       // same ConstMethod* and we would save the space occupied by
       // the old ConstMethod*. However, the ConstMethod* contains
       // a back reference to the containing method. Sharing the
       // ConstMethod* between two methods could lead to confusion in
       // the code that uses the back reference. This would lead to
       // brittle code that could be broken in non-obvious ways now or
       // in the future.
       //
       // Another possibility is to copy the ConstMethod* from the new
       // method to the old method and then overwrite the new method with
       // the old method. Since the ConstMethod* contains the bytecodes
       // for the method embedded in the oop, this option would change
       // the bytecodes out from under any threads executing the old
       // method and make the thread's bcp invalid. Since EMCP requires
       // that the bytecodes be the same modulo constant pool indices, it
       // is straight forward to compute the correct new bcp in the new
       // ConstMethod* from the old bcp in the old ConstMethod*. The
       // time consuming part would be searching all the frames in all
       // of the threads to find all of the calls to the old method.
       //
       // It looks like we will have to live with the limited savings
       // that we get from effectively overwriting the old methods
       // when the new methods are attached to the_class.
       // track which methods are EMCP for add_previous_version() call
       emcp_methods->set_bit(old_index);
       (*emcp_method_count_p)++;
       // An EMCP method is _not_ obsolete. An obsolete method has a
       // different jmethodID than the current method. An EMCP method
       // has the same jmethodID as the current method. Having the
       // same jmethodID for all EMCP versions of a method allows for
       // a consistent view of the EMCP methods regardless of which
       // EMCP method you happen to have in hand. For example, a
       // breakpoint set in one EMCP method will work for all EMCP
       // versions of the method including the current one.
     } else {
       // mark obsolete methods as such
       old_method->set_is_obsolete();
       obsolete_count++;
       // obsolete methods need a unique idnum
       u2 num = InstanceKlass::cast(_the_class_oop)->next_method_idnum();
       if (num != ConstMethod::UNSET_IDNUM) {
 //      u2 old_num = old_method->method_idnum();
         old_method->set_method_idnum(num);
 // TO DO: attach obsolete annotations to obsolete method's new idnum
       }
       // With tracing we try not to "yack" too much. The position of
       // this trace assumes there are fewer obsolete methods than
       // EMCP methods.
       RC_TRACE(0x00000100, ("mark %s(%s) as obsolete",
         old_method->name()->as_C_string(),
         old_method->signature()->as_C_string()));
     }
     old_method->set_is_old();
   }
   for (int i = 0; i < _deleted_methods_length; ++i) {
     Method* old_method = _deleted_methods[i];
     assert(old_method->vtable_index() < 0,
            "cannot delete methods with vtable entries");;
     // Mark all deleted methods as old and obsolete
     old_method->set_is_old();
     old_method->set_is_obsolete();
     ++obsolete_count;
     // With tracing we try not to "yack" too much. The position of
     // this trace assumes there are fewer obsolete methods than
     // EMCP methods.
     RC_TRACE(0x00000100, ("mark deleted %s(%s) as obsolete",
                           old_method->name()->as_C_string(),
                           old_method->signature()->as_C_string()));
   }
   assert((*emcp_method_count_p + obsolete_count) == _old_methods->length(),
     "sanity check");
   RC_TRACE(0x00000100, ("EMCP_cnt=%d, obsolete_cnt=%d", *emcp_method_count_p,
     obsolete_count));
 }
 // This internal class transfers the native function registration from old methods
 // to new methods.  It is designed to handle both the simple case of unchanged
 // native methods and the complex cases of native method prefixes being added and/or
 // removed.
 // It expects only to be used during the VM_RedefineClasses op (a safepoint).
 //
 // This class is used after the new methods have been installed in "the_class".
 //
 // So, for example, the following must be handled.  Where 'm' is a method and
 // a number followed by an underscore is a prefix.
 //
 //                                      Old Name    New Name
 // Simple transfer to new method        m       ->  m
 // Add prefix                           m       ->  1_m
 // Remove prefix                        1_m     ->  m
 // Simultaneous add of prefixes         m       ->  3_2_1_m
 // Simultaneous removal of prefixes     3_2_1_m ->  m
 // Simultaneous add and remove          1_m     ->  2_m
 // Same, caused by prefix removal only  3_2_1_m ->  3_2_m
 //
 class TransferNativeFunctionRegistration {
  private:
   instanceKlassHandle the_class;
   int prefix_count;
   char** prefixes;
   // Recursively search the binary tree of possibly prefixed method names.
   // Iteration could be used if all agents were well behaved. Full tree walk is
   // more resilent to agents not cleaning up intermediate methods.
   // Branch at each depth in the binary tree is:
   //    (1) without the prefix.
   //    (2) with the prefix.
   // where 'prefix' is the prefix at that 'depth' (first prefix, second prefix,...)
   Method* search_prefix_name_space(int depth, char* name_str, size_t name_len,
                                      Symbol* signature) {
     TempNewSymbol name_symbol = SymbolTable::probe(name_str, (int)name_len);
     if (name_symbol != NULL) {
       Method* method = Klass::cast(the_class())->lookup_method(name_symbol, signature);
       if (method != NULL) {
         // Even if prefixed, intermediate methods must exist.
         if (method->is_native()) {
           // Wahoo, we found a (possibly prefixed) version of the method, return it.
           return method;
         }
         if (depth < prefix_count) {
           // Try applying further prefixes (other than this one).
           method = search_prefix_name_space(depth+1, name_str, name_len, signature);
           if (method != NULL) {
             return method; // found
           }
           // Try adding this prefix to the method name and see if it matches
           // another method name.
           char* prefix = prefixes[depth];
           size_t prefix_len = strlen(prefix);
           size_t trial_len = name_len + prefix_len;
           char* trial_name_str = NEW_RESOURCE_ARRAY(char, trial_len + 1);
           strcpy(trial_name_str, prefix);
           strcat(trial_name_str, name_str);
           method = search_prefix_name_space(depth+1, trial_name_str, trial_len,
                                             signature);
           if (method != NULL) {
             // If found along this branch, it was prefixed, mark as such
             method->set_is_prefixed_native();
             return method; // found
           }
         }
       }
     }
     return NULL;  // This whole branch bore nothing
   }
   // Return the method name with old prefixes stripped away.
   char* method_name_without_prefixes(Method* method) {
     Symbol* name = method->name();
     char* name_str = name->as_utf8();
     // Old prefixing may be defunct, strip prefixes, if any.
     for (int i = prefix_count-1; i >= 0; i--) {
       char* prefix = prefixes[i];
       size_t prefix_len = strlen(prefix);
       if (strncmp(prefix, name_str, prefix_len) == 0) {
         name_str += prefix_len;
       }
     }
     return name_str;
   }
   // Strip any prefixes off the old native method, then try to find a
   // (possibly prefixed) new native that matches it.
   Method* strip_and_search_for_new_native(Method* method) {
     ResourceMark rm;
     char* name_str = method_name_without_prefixes(method);
     return search_prefix_name_space(0, name_str, strlen(name_str),
                                     method->signature());
   }
  public:
   // Construct a native method transfer processor for this class.
   TransferNativeFunctionRegistration(instanceKlassHandle _the_class) {
     assert(SafepointSynchronize::is_at_safepoint(), "sanity check");
     the_class = _the_class;
     prefixes = JvmtiExport::get_all_native_method_prefixes(&prefix_count);
   }
   // Attempt to transfer any of the old or deleted methods that are native
   void transfer_registrations(Method** old_methods, int methods_length) {
     for (int j = 0; j < methods_length; j++) {
       Method* old_method = old_methods[j];
       if (old_method->is_native() && old_method->has_native_function()) {
         Method* new_method = strip_and_search_for_new_native(old_method);
         if (new_method != NULL) {
           // Actually set the native function in the new method.
           // Redefine does not send events (except CFLH), certainly not this
           // behind the scenes re-registration.
           new_method->set_native_function(old_method->native_function(),
                               !Method::native_bind_event_is_interesting);
         }
       }
     }
   }
 };
 // Don't lose the association between a native method and its JNI function.
 void VM_RedefineClasses::transfer_old_native_function_registrations(instanceKlassHandle the_class) {
   TransferNativeFunctionRegistration transfer(the_class);
   transfer.transfer_registrations(_deleted_methods, _deleted_methods_length);
   transfer.transfer_registrations(_matching_old_methods, _matching_methods_length);
 }
 // Deoptimize all compiled code that depends on this class.
 //
 // If the can_redefine_classes capability is obtained in the onload
 // phase then the compiler has recorded all dependencies from startup.
 // In that case we need only deoptimize and throw away all compiled code
 // that depends on the class.
 //
 // If can_redefine_classes is obtained sometime after the onload
 // phase then the dependency information may be incomplete. In that case
 // the first call to RedefineClasses causes all compiled code to be
 // thrown away. As can_redefine_classes has been obtained then
 // all future compilations will record dependencies so second and
 // subsequent calls to RedefineClasses need only throw away code
 // that depends on the class.
 //
 void VM_RedefineClasses::flush_dependent_code(instanceKlassHandle k_h, TRAPS) {
   assert_locked_or_safepoint(Compile_lock);
   // All dependencies have been recorded from startup or this is a second or
   // subsequent use of RedefineClasses
   if (JvmtiExport::all_dependencies_are_recorded()) {
     Universe::flush_evol_dependents_on(k_h);
   } else {
     CodeCache::mark_all_nmethods_for_deoptimization();
     ResourceMark rm(THREAD);
     DeoptimizationMarker dm;
     // Deoptimize all activations depending on marked nmethods
     Deoptimization::deoptimize_dependents();
     // Make the dependent methods not entrant (in VM_Deoptimize they are made zombies)
     CodeCache::make_marked_nmethods_not_entrant();
     // From now on we know that the dependency information is complete
     JvmtiExport::set_all_dependencies_are_recorded(true);
   }
 }
 void VM_RedefineClasses::compute_added_deleted_matching_methods() {
   Method* old_method;
   Method* new_method;
   _matching_old_methods = NEW_RESOURCE_ARRAY(Method*, _old_methods->length());
   _matching_new_methods = NEW_RESOURCE_ARRAY(Method*, _old_methods->length());
   _added_methods        = NEW_RESOURCE_ARRAY(Method*, _new_methods->length());
   _deleted_methods      = NEW_RESOURCE_ARRAY(Method*, _old_methods->length());
   _matching_methods_length = 0;
   _deleted_methods_length  = 0;
   _added_methods_length    = 0;
   int nj = 0;
   int oj = 0;
   while (true) {
     if (oj >= _old_methods->length()) {
       if (nj >= _new_methods->length()) {
         break; // we've looked at everything, done
       }
       // New method at the end
       new_method = _new_methods->at(nj);
       _added_methods[_added_methods_length++] = new_method;
       ++nj;
     } else if (nj >= _new_methods->length()) {
       // Old method, at the end, is deleted
       old_method = _old_methods->at(oj);
       _deleted_methods[_deleted_methods_length++] = old_method;
       ++oj;
     } else {
       old_method = _old_methods->at(oj);
       new_method = _new_methods->at(nj);
       if (old_method->name() == new_method->name()) {
         if (old_method->signature() == new_method->signature()) {
           _matching_old_methods[_matching_methods_length  ] = old_method;
           _matching_new_methods[_matching_methods_length++] = new_method;
           ++nj;
           ++oj;
         } else {
           // added overloaded have already been moved to the end,
           // so this is a deleted overloaded method
           _deleted_methods[_deleted_methods_length++] = old_method;
           ++oj;
         }
       } else { // names don't match
         if (old_method->name()->fast_compare(new_method->name()) > 0) {
           // new method
           _added_methods[_added_methods_length++] = new_method;
           ++nj;
         } else {
           // deleted method
           _deleted_methods[_deleted_methods_length++] = old_method;
           ++oj;
         }
       }
     }
   }
   assert(_matching_methods_length + _deleted_methods_length == _old_methods->length(), "sanity");
   assert(_matching_methods_length + _added_methods_length == _new_methods->length(), "sanity");
 }
 // Install the redefinition of a class:
 //    - house keeping (flushing breakpoints and caches, deoptimizing
 //      dependent compiled code)
 //    - replacing parts in the_class with parts from scratch_class
 //    - adding a weak reference to track the obsolete but interesting
 //      parts of the_class
 //    - adjusting constant pool caches and vtables in other classes
 //      that refer to methods in the_class. These adjustments use the
 //      SystemDictionary::classes_do() facility which only allows
 //      a helper method to be specified. The interesting parameters
 //      that we would like to pass to the helper method are saved in
 //      static global fields in the VM operation.
 void VM_RedefineClasses::redefine_single_class(jclass the_jclass,
        Klass* scratch_class_oop, TRAPS) {
   HandleMark hm(THREAD);   // make sure handles from this call are freed
   RC_TIMER_START(_timer_rsc_phase1);
   instanceKlassHandle scratch_class(scratch_class_oop);
   oop the_class_mirror = JNIHandles::resolve_non_null(the_jclass);
   Klass* the_class_oop = java_lang_Class::as_Klass(the_class_mirror);
   instanceKlassHandle the_class = instanceKlassHandle(THREAD, the_class_oop);
 #ifndef JVMTI_KERNEL
   // Remove all breakpoints in methods of this class
   JvmtiBreakpoints& jvmti_breakpoints = JvmtiCurrentBreakpoints::get_jvmti_breakpoints();
   jvmti_breakpoints.clearall_in_class_at_safepoint(the_class_oop);
 #endif // !JVMTI_KERNEL
   if (the_class_oop == Universe::reflect_invoke_cache()->klass()) {
     // We are redefining java.lang.reflect.Method. Method.invoke() is
     // cached and users of the cache care about each active version of
     // the method so we have to track this previous version.
     // Do this before methods get switched
     Universe::reflect_invoke_cache()->add_previous_version(
       the_class->method_with_idnum(Universe::reflect_invoke_cache()->method_idnum()));
   }
   // Deoptimize all compiled code that depends on this class
   flush_dependent_code(the_class, THREAD);
   _old_methods = the_class->methods();
   _new_methods = scratch_class->methods();
   _the_class_oop = the_class_oop;
   compute_added_deleted_matching_methods();
   update_jmethod_ids();
   // Attach new constant pool to the original klass. The original
   // klass still refers to the old constant pool (for now).
   scratch_class->constants()->set_pool_holder(the_class());
 #if 0
   // In theory, with constant pool merging in place we should be able
   // to save space by using the new, merged constant pool in place of
   // the old constant pool(s). By "pool(s)" I mean the constant pool in
   // the klass version we are replacing now and any constant pool(s) in
   // previous versions of klass. Nice theory, doesn't work in practice.
   // When this code is enabled, even simple programs throw NullPointer
   // exceptions. I'm guessing that this is caused by some constant pool
   // cache difference between the new, merged constant pool and the
   // constant pool that was just being used by the klass. I'm keeping
   // this code around to archive the idea, but the code has to remain
   // disabled for now.
   // Attach each old method to the new constant pool. This can be
   // done here since we are past the bytecode verification and
   // constant pool optimization phases.
   for (int i = _old_methods->length() - 1; i >= 0; i--) {
     Method* method = _old_methods->at(i);
     method->set_constants(scratch_class->constants());
   }
   {
     // walk all previous versions of the klass
     InstanceKlass *ik = (InstanceKlass *)the_class();
     PreviousVersionWalker pvw(ik);
     instanceKlassHandle ikh;
     do {
       ikh = pvw.next_previous_version();
       if (!ikh.is_null()) {
         ik = ikh();
         // attach previous version of klass to the new constant pool
         ik->set_constants(scratch_class->constants());
         // Attach each method in the previous version of klass to the
         // new constant pool
         Array<Method*>* prev_methods = ik->methods();
         for (int i = prev_methods->length() - 1; i >= 0; i--) {
           Method* method = prev_methods->at(i);
           method->set_constants(scratch_class->constants());
         }
       }
     } while (!ikh.is_null());
   }
 #endif
   // Replace methods and constantpool
   the_class->set_methods(_new_methods);
   scratch_class->set_methods(_old_methods);     // To prevent potential GCing of the old methods,
                                           // and to be able to undo operation easily.
   ConstantPool* old_constants = the_class->constants();
   the_class->set_constants(scratch_class->constants());
   scratch_class->set_constants(old_constants);  // See the previous comment.
 #if 0
   // We are swapping the guts of "the new class" with the guts of "the
   // class". Since the old constant pool has just been attached to "the
   // new class", it seems logical to set the pool holder in the old
   // constant pool also. However, doing this will change the observable
   // class hierarchy for any old methods that are still executing. A
   // method can query the identity of its "holder" and this query uses
   // the method's constant pool link to find the holder. The change in
   // holding class from "the class" to "the new class" can confuse
   // things.
   //
   // Setting the old constant pool's holder will also cause
   // verification done during vtable initialization below to fail.
   // During vtable initialization, the vtable's class is verified to be
   // a subtype of the method's holder. The vtable's class is "the
   // class" and the method's holder is gotten from the constant pool
   // link in the method itself. For "the class"'s directly implemented
   // methods, the method holder is "the class" itself (as gotten from
   // the new constant pool). The check works fine in this case. The
   // check also works fine for methods inherited from super classes.
   //
   // Miranda methods are a little more complicated. A miranda method is
   // provided by an interface when the class implementing the interface
   // does not provide its own method.  These interfaces are implemented
   // internally as an InstanceKlass. These special instanceKlasses
   // share the constant pool of the class that "implements" the
   // interface. By sharing the constant pool, the method holder of a
   // miranda method is the class that "implements" the interface. In a
   // non-redefine situation, the subtype check works fine. However, if
   // the old constant pool's pool holder is modified, then the check
   // fails because there is no class hierarchy relationship between the
   // vtable's class and "the new class".
   old_constants->set_pool_holder(scratch_class());
 #endif
   // track which methods are EMCP for add_previous_version() call below
   BitMap emcp_methods(_old_methods->length());
   int emcp_method_count = 0;
   emcp_methods.clear();  // clears 0..(length() - 1)
   check_methods_and_mark_as_obsolete(&emcp_methods, &emcp_method_count);
   transfer_old_native_function_registrations(the_class);
   // The class file bytes from before any retransformable agents mucked
   // with them was cached on the scratch class, move to the_class.
   // Note: we still want to do this if nothing needed caching since it
   // should get cleared in the_class too.
   if (the_class->get_cached_class_file_bytes() == 0) {
     // the_class doesn't have a cache yet so copy it
     the_class->set_cached_class_file(
       scratch_class->get_cached_class_file_bytes(),
       scratch_class->get_cached_class_file_len());
   }
 #ifndef PRODUCT
   else {
     assert(the_class->get_cached_class_file_bytes() ==
       scratch_class->get_cached_class_file_bytes(), "cache ptrs must match");
     assert(the_class->get_cached_class_file_len() ==
       scratch_class->get_cached_class_file_len(), "cache lens must match");
   }
 #endif
   // Replace inner_classes
   Array<u2>* old_inner_classes = the_class->inner_classes();
   the_class->set_inner_classes(scratch_class->inner_classes());
   scratch_class->set_inner_classes(old_inner_classes);
   // Initialize the vtable and interface table after
   // methods have been rewritten
   {
     ResourceMark rm(THREAD);
     // no exception should happen here since we explicitly
     // do not check loader constraints.
     // compare_and_normalize_class_versions has already checked:
     //  - classloaders unchanged, signatures unchanged
     //  - all instanceKlasses for redefined classes reused & contents updated
     the_class->vtable()->initialize_vtable(false, THREAD);
     the_class->itable()->initialize_itable(false, THREAD);
     assert(!HAS_PENDING_EXCEPTION || (THREAD->pending_exception()->is_a(SystemDictionary::ThreadDeath_klass())), "redefine exception");
   }
   // Leave arrays of jmethodIDs and itable index cache unchanged
   // Copy the "source file name" attribute from new class version
   the_class->set_source_file_name(scratch_class->source_file_name());
   // Copy the "source debug extension" attribute from new class version
   the_class->set_source_debug_extension(
     scratch_class->source_debug_extension(),
     scratch_class->source_debug_extension() == NULL ? 0 :
     (int)strlen(scratch_class->source_debug_extension()));
   // Use of javac -g could be different in the old and the new
   if (scratch_class->access_flags().has_localvariable_table() !=
       the_class->access_flags().has_localvariable_table()) {
     AccessFlags flags = the_class->access_flags();
     if (scratch_class->access_flags().has_localvariable_table()) {
       flags.set_has_localvariable_table();
     } else {
       flags.clear_has_localvariable_table();
     }
     the_class->set_access_flags(flags);
   }
   // Replace annotation fields value
   Annotations* old_annotations = the_class->annotations();
   the_class->set_annotations(scratch_class->annotations());
   scratch_class->set_annotations(old_annotations);
   // Replace minor version number of class file
   u2 old_minor_version = the_class->minor_version();
   the_class->set_minor_version(scratch_class->minor_version());
   scratch_class->set_minor_version(old_minor_version);
   // Replace major version number of class file
   u2 old_major_version = the_class->major_version();
   the_class->set_major_version(scratch_class->major_version());
   scratch_class->set_major_version(old_major_version);
   // Replace CP indexes for class and name+type of enclosing method
   u2 old_class_idx  = the_class->enclosing_method_class_index();
   u2 old_method_idx = the_class->enclosing_method_method_index();
   the_class->set_enclosing_method_indices(
     scratch_class->enclosing_method_class_index(),
     scratch_class->enclosing_method_method_index());
   scratch_class->set_enclosing_method_indices(old_class_idx, old_method_idx);
   // keep track of previous versions of this class
   the_class->add_previous_version(scratch_class, &emcp_methods,
     emcp_method_count);
   RC_TIMER_STOP(_timer_rsc_phase1);
   RC_TIMER_START(_timer_rsc_phase2);
   // Adjust constantpool caches and vtables for all classes
   // that reference methods of the evolved class.
   SystemDictionary::classes_do(adjust_cpool_cache_and_vtable, THREAD);
   // Fix Resolution Error table also to remove old constant pools
   SystemDictionary::delete_resolution_error(old_constants);
   if (the_class->oop_map_cache() != NULL) {
     // Flush references to any obsolete methods from the oop map cache
     // so that obsolete methods are not pinned.
     the_class->oop_map_cache()->flush_obsolete_entries();
   }
   // increment the classRedefinedCount field in the_class and in any
   // direct and indirect subclasses of the_class
   increment_class_counter((InstanceKlass *)the_class(), THREAD);
   // RC_TRACE macro has an embedded ResourceMark
   RC_TRACE_WITH_THREAD(0x00000001, THREAD,
     ("redefined name=%s, count=%d (avail_mem=" UINT64_FORMAT "K)",
     the_class->external_name(),
     java_lang_Class::classRedefinedCount(the_class_mirror),
     os::available_memory() >> 10));
   RC_TIMER_STOP(_timer_rsc_phase2);
 } // end redefine_single_class()
 // Increment the classRedefinedCount field in the specific InstanceKlass
 // and in all direct and indirect subclasses.
 void VM_RedefineClasses::increment_class_counter(InstanceKlass *ik, TRAPS) {
   oop class_mirror = ik->java_mirror();
   Klass* class_oop = java_lang_Class::as_Klass(class_mirror);
   int new_count = java_lang_Class::classRedefinedCount(class_mirror) + 1;
   java_lang_Class::set_classRedefinedCount(class_mirror, new_count);
   if (class_oop != _the_class_oop) {
     // _the_class_oop count is printed at end of redefine_single_class()
     RC_TRACE_WITH_THREAD(0x00000008, THREAD,
       ("updated count in subclass=%s to %d", ik->external_name(), new_count));
   }
   for (Klass *subk = ik->subklass(); subk != NULL;
        subk = subk->next_sibling()) {
     if (subk->oop_is_instance()) {
       // Only update instanceKlasses
       InstanceKlass *subik = (InstanceKlass*)subk;
       // recursively do subclasses of the current subclass
       increment_class_counter(subik, THREAD);
     }
   }
 }
 #ifndef PRODUCT
 void VM_RedefineClasses::check_class(Klass* k_oop,
                                      ClassLoaderData* initiating_loader,
                                      TRAPS) {
   Klass *k = k_oop;
   if (k->oop_is_instance()) {
     HandleMark hm(THREAD);
     InstanceKlass *ik = (InstanceKlass *) k;
     if (ik->vtable_length() > 0) {
       ResourceMark rm(THREAD);
       if (!ik->vtable()->check_no_old_entries()) {
         tty->print_cr("klassVtable::check_no_old_entries failure -- OLD method found -- class: %s", ik->signature_name());
         ik->vtable()->dump_vtable();
         assert(false, "OLD method found");
       }
     }
     if (ik->itable_length() > 0) {
       ResourceMark rm(THREAD);
       if (!ik->itable()->check_no_old_entries()) {
         tty->print_cr("klassItable::check_no_old_entries failure -- OLD method found -- class: %s", ik->signature_name());
         assert(false, "OLD method found");
       }
     }
     // Check that the constant pool cache has no deleted entries.
     if (ik->constants() != NULL &&
         ik->constants()->cache() != NULL &&
        !ik->constants()->cache()->check_no_old_entries()) {
       tty->print_cr("klassVtable::check_no_old_entries failure -- OLD method found -- class: %s", ik->signature_name());
       assert(false, "OLD method found");
     }
   }
 }
 void VM_RedefineClasses::dump_methods() {
         int j;
         tty->print_cr("_old_methods --");
         for (j = 0; j < _old_methods->length(); ++j) {
           Method* m = _old_methods->at(j);
           tty->print("%4d  (%5d)  ", j, m->vtable_index());
           m->access_flags().print_on(tty);
           tty->print(" --  ");
           m->print_name(tty);
           tty->cr();
         }
         tty->print_cr("_new_methods --");
         for (j = 0; j < _new_methods->length(); ++j) {
           Method* m = _new_methods->at(j);
           tty->print("%4d  (%5d)  ", j, m->vtable_index());
           m->access_flags().print_on(tty);
           tty->print(" --  ");
           m->print_name(tty);
           tty->cr();
         }
         tty->print_cr("_matching_(old/new)_methods --");
         for (j = 0; j < _matching_methods_length; ++j) {
           Method* m = _matching_old_methods[j];
           tty->print("%4d  (%5d)  ", j, m->vtable_index());
           m->access_flags().print_on(tty);
           tty->print(" --  ");
           m->print_name(tty);
           tty->cr();
           m = _matching_new_methods[j];
           tty->print("      (%5d)  ", m->vtable_index());
           m->access_flags().print_on(tty);
           tty->cr();
         }
         tty->print_cr("_deleted_methods --");
         for (j = 0; j < _deleted_methods_length; ++j) {
           Method* m = _deleted_methods[j];
           tty->print("%4d  (%5d)  ", j, m->vtable_index());
           m->access_flags().print_on(tty);
           tty->print(" --  ");
           m->print_name(tty);
           tty->cr();
         }
         tty->print_cr("_added_methods --");
         for (j = 0; j < _added_methods_length; ++j) {
           Method* m = _added_methods[j];
           tty->print("%4d  (%5d)  ", j, m->vtable_index());
           m->access_flags().print_on(tty);
           tty->print(" --  ");
           m->print_name(tty);
           tty->cr();
         }
 }
 #endif

Mercurial > jdk8-mips64-public > hotspot / annotate

src/share/vm/prims/jvmtiRedefineClasses.cpp@da91efe96a93 (annotated)

src/share/vm/prims/jvmtiRedefineClasses.cpp