view src/share/vm/runtime/java.cpp @ 2682:eca1193ca245

4965777: GC changes to support use of discovered field for pending references Summary: If and when the reference handler thread is able to use the discovered field to link reference objects in its pending list, so will GC. In that case, GC will scan through this field once a reference object has been placed on the pending list, but not scan that field before that stage, as the field is used by the concurrent GC thread to link discovered objects. When ReferenceHandleR thread does not use the discovered field for the purpose of linking the elements in the pending list, as would be the case in older JDKs, the JVM will fall back to the old behaviour of using the next field for that purpose. Reviewed-by: jcoomes, mchung, stefank
author ysr
date Wed, 07 Sep 2011 13:55:42 -0700
parents 0f34fdee809e
children f08d439fab8c
line wrap: on
line source
/*
 * Copyright (c) 1997, 2011, 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/classLoader.hpp"
#include "classfile/symbolTable.hpp"
#include "classfile/systemDictionary.hpp"
#include "code/codeCache.hpp"
#include "compiler/compileBroker.hpp"
#include "compiler/compilerOracle.hpp"
#include "interpreter/bytecodeHistogram.hpp"
#include "memory/genCollectedHeap.hpp"
#include "memory/oopFactory.hpp"
#include "memory/universe.hpp"
#include "oops/constantPoolOop.hpp"
#include "oops/generateOopMap.hpp"
#include "oops/instanceKlass.hpp"
#include "oops/instanceKlassKlass.hpp"
#include "oops/instanceOop.hpp"
#include "oops/methodOop.hpp"
#include "oops/objArrayOop.hpp"
#include "oops/oop.inline.hpp"
#include "oops/symbol.hpp"
#include "prims/jvmtiExport.hpp"
#include "runtime/aprofiler.hpp"
#include "runtime/arguments.hpp"
#include "runtime/biasedLocking.hpp"
#include "runtime/compilationPolicy.hpp"
#include "runtime/fprofiler.hpp"
#include "runtime/init.hpp"
#include "runtime/interfaceSupport.hpp"
#include "runtime/java.hpp"
#include "runtime/memprofiler.hpp"
#include "runtime/sharedRuntime.hpp"
#include "runtime/statSampler.hpp"
#include "runtime/task.hpp"
#include "runtime/timer.hpp"
#include "runtime/vm_operations.hpp"
#include "utilities/dtrace.hpp"
#include "utilities/globalDefinitions.hpp"
#include "utilities/histogram.hpp"
#include "utilities/vmError.hpp"
#ifdef TARGET_ARCH_x86
# include "vm_version_x86.hpp"
#endif
#ifdef TARGET_ARCH_sparc
# include "vm_version_sparc.hpp"
#endif
#ifdef TARGET_ARCH_zero
# include "vm_version_zero.hpp"
#endif
#ifdef TARGET_ARCH_arm
# include "vm_version_arm.hpp"
#endif
#ifdef TARGET_ARCH_ppc
# include "vm_version_ppc.hpp"
#endif
#ifdef TARGET_OS_FAMILY_linux
# include "thread_linux.inline.hpp"
#endif
#ifdef TARGET_OS_FAMILY_solaris
# include "thread_solaris.inline.hpp"
#endif
#ifdef TARGET_OS_FAMILY_windows
# include "thread_windows.inline.hpp"
#endif
#ifndef SERIALGC
#include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp"
#include "gc_implementation/parallelScavenge/psScavenge.hpp"
#include "gc_implementation/parallelScavenge/psScavenge.inline.hpp"
#endif
#ifdef COMPILER1
#include "c1/c1_Compiler.hpp"
#include "c1/c1_Runtime1.hpp"
#endif
#ifdef COMPILER2
#include "code/compiledIC.hpp"
#include "compiler/methodLiveness.hpp"
#include "opto/compile.hpp"
#include "opto/indexSet.hpp"
#include "opto/runtime.hpp"
#endif

HS_DTRACE_PROBE_DECL(hotspot, vm__shutdown);

#ifndef PRODUCT

// Statistics printing (method invocation histogram)

GrowableArray<methodOop>* collected_invoked_methods;

void collect_invoked_methods(methodOop m) {
  if (m->invocation_count() + m->compiled_invocation_count() >= 1 ) {
    collected_invoked_methods->push(m);
  }
}


GrowableArray<methodOop>* collected_profiled_methods;

void collect_profiled_methods(methodOop m) {
  methodHandle mh(Thread::current(), m);
  if ((m->method_data() != NULL) &&
      (PrintMethodData || CompilerOracle::should_print(mh))) {
    collected_profiled_methods->push(m);
  }
}


int compare_methods(methodOop* a, methodOop* b) {
  // %%% there can be 32-bit overflow here
  return ((*b)->invocation_count() + (*b)->compiled_invocation_count())
       - ((*a)->invocation_count() + (*a)->compiled_invocation_count());
}


void print_method_invocation_histogram() {
  ResourceMark rm;
  HandleMark hm;
  collected_invoked_methods = new GrowableArray<methodOop>(1024);
  SystemDictionary::methods_do(collect_invoked_methods);
  collected_invoked_methods->sort(&compare_methods);
  //
  tty->cr();
  tty->print_cr("Histogram Over MethodOop Invocation Counters (cutoff = %d):", MethodHistogramCutoff);
  tty->cr();
  tty->print_cr("____Count_(I+C)____Method________________________Module_________________");
  unsigned total = 0, int_total = 0, comp_total = 0, static_total = 0, final_total = 0,
      synch_total = 0, nativ_total = 0, acces_total = 0;
  for (int index = 0; index < collected_invoked_methods->length(); index++) {
    methodOop m = collected_invoked_methods->at(index);
    int c = m->invocation_count() + m->compiled_invocation_count();
    if (c >= MethodHistogramCutoff) m->print_invocation_count();
    int_total  += m->invocation_count();
    comp_total += m->compiled_invocation_count();
    if (m->is_final())        final_total  += c;
    if (m->is_static())       static_total += c;
    if (m->is_synchronized()) synch_total  += c;
    if (m->is_native())       nativ_total  += c;
    if (m->is_accessor())     acces_total  += c;
  }
  tty->cr();
  total = int_total + comp_total;
  tty->print_cr("Invocations summary:");
  tty->print_cr("\t%9d (%4.1f%%) interpreted",  int_total,    100.0 * int_total    / total);
  tty->print_cr("\t%9d (%4.1f%%) compiled",     comp_total,   100.0 * comp_total   / total);
  tty->print_cr("\t%9d (100%%)  total",         total);
  tty->print_cr("\t%9d (%4.1f%%) synchronized", synch_total,  100.0 * synch_total  / total);
  tty->print_cr("\t%9d (%4.1f%%) final",        final_total,  100.0 * final_total  / total);
  tty->print_cr("\t%9d (%4.1f%%) static",       static_total, 100.0 * static_total / total);
  tty->print_cr("\t%9d (%4.1f%%) native",       nativ_total,  100.0 * nativ_total  / total);
  tty->print_cr("\t%9d (%4.1f%%) accessor",     acces_total,  100.0 * acces_total  / total);
  tty->cr();
  SharedRuntime::print_call_statistics(comp_total);
}

void print_method_profiling_data() {
  ResourceMark rm;
  HandleMark hm;
  collected_profiled_methods = new GrowableArray<methodOop>(1024);
  SystemDictionary::methods_do(collect_profiled_methods);
  collected_profiled_methods->sort(&compare_methods);

  int count = collected_profiled_methods->length();
  if (count > 0) {
    for (int index = 0; index < count; index++) {
      methodOop m = collected_profiled_methods->at(index);
      ttyLocker ttyl;
      tty->print_cr("------------------------------------------------------------------------");
      //m->print_name(tty);
      m->print_invocation_count();
      tty->cr();
      m->print_codes();
    }
    tty->print_cr("------------------------------------------------------------------------");
  }
}

void print_bytecode_count() {
  if (CountBytecodes || TraceBytecodes || StopInterpreterAt) {
    tty->print_cr("[BytecodeCounter::counter_value = %d]", BytecodeCounter::counter_value());
  }
}

AllocStats alloc_stats;



// General statistics printing (profiling ...)

void print_statistics() {

#ifdef ASSERT

  if (CountRuntimeCalls) {
    extern Histogram *RuntimeHistogram;
    RuntimeHistogram->print();
  }

  if (CountJNICalls) {
    extern Histogram *JNIHistogram;
    JNIHistogram->print();
  }

  if (CountJVMCalls) {
    extern Histogram *JVMHistogram;
    JVMHistogram->print();
  }

#endif

  if (MemProfiling) {
    MemProfiler::disengage();
  }

  if (CITime) {
    CompileBroker::print_times();
  }

#ifdef COMPILER1
  if ((PrintC1Statistics || LogVMOutput || LogCompilation) && UseCompiler) {
    FlagSetting fs(DisplayVMOutput, DisplayVMOutput && PrintC1Statistics);
    Runtime1::print_statistics();
    Deoptimization::print_statistics();
    SharedRuntime::print_statistics();
    nmethod::print_statistics();
  }
#endif /* COMPILER1 */

#ifdef COMPILER2
  if ((PrintOptoStatistics || LogVMOutput || LogCompilation) && UseCompiler) {
    FlagSetting fs(DisplayVMOutput, DisplayVMOutput && PrintOptoStatistics);
    Compile::print_statistics();
#ifndef COMPILER1
    Deoptimization::print_statistics();
    nmethod::print_statistics();
    SharedRuntime::print_statistics();
#endif //COMPILER1
    os::print_statistics();
  }

  if (PrintLockStatistics || PrintPreciseBiasedLockingStatistics) {
    OptoRuntime::print_named_counters();
  }

  if (TimeLivenessAnalysis) {
    MethodLiveness::print_times();
  }
#ifdef ASSERT
  if (CollectIndexSetStatistics) {
    IndexSet::print_statistics();
  }
#endif // ASSERT
#endif // COMPILER2
  if (CountCompiledCalls) {
    print_method_invocation_histogram();
  }
  if (ProfileInterpreter COMPILER1_PRESENT(|| C1UpdateMethodData)) {
    print_method_profiling_data();
  }
  if (TimeCompiler) {
    COMPILER2_PRESENT(Compile::print_timers();)
  }
  if (TimeCompilationPolicy) {
    CompilationPolicy::policy()->print_time();
  }
  if (TimeOopMap) {
    GenerateOopMap::print_time();
  }
  if (ProfilerCheckIntervals) {
    PeriodicTask::print_intervals();
  }
  if (PrintSymbolTableSizeHistogram) {
    SymbolTable::print_histogram();
  }
  if (CountBytecodes || TraceBytecodes || StopInterpreterAt) {
    BytecodeCounter::print();
  }
  if (PrintBytecodePairHistogram) {
    BytecodePairHistogram::print();
  }

  if (PrintCodeCache) {
    MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
    CodeCache::print();
  }

  if (PrintCodeCache2) {
    MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
    CodeCache::print_internals();
  }

  if (PrintClassStatistics) {
    SystemDictionary::print_class_statistics();
  }
  if (PrintMethodStatistics) {
    SystemDictionary::print_method_statistics();
  }

  if (PrintVtableStats) {
    klassVtable::print_statistics();
    klassItable::print_statistics();
  }
  if (VerifyOops) {
    tty->print_cr("+VerifyOops count: %d", StubRoutines::verify_oop_count());
  }

  print_bytecode_count();
  if (PrintMallocStatistics) {
    tty->print("allocation stats: ");
    alloc_stats.print();
    tty->cr();
  }

  if (PrintSystemDictionaryAtExit) {
    SystemDictionary::print();
  }

  if (PrintBiasedLockingStatistics) {
    BiasedLocking::print_counters();
  }

#ifdef ENABLE_ZAP_DEAD_LOCALS
#ifdef COMPILER2
  if (ZapDeadCompiledLocals) {
    tty->print_cr("Compile::CompiledZap_count = %d", Compile::CompiledZap_count);
    tty->print_cr("OptoRuntime::ZapDeadCompiledLocals_count = %d", OptoRuntime::ZapDeadCompiledLocals_count);
  }
#endif // COMPILER2
#endif // ENABLE_ZAP_DEAD_LOCALS
}

#else // PRODUCT MODE STATISTICS

void print_statistics() {

  if (CITime) {
    CompileBroker::print_times();
  }
#ifdef COMPILER2
  if (PrintPreciseBiasedLockingStatistics) {
    OptoRuntime::print_named_counters();
  }
#endif
  if (PrintBiasedLockingStatistics) {
    BiasedLocking::print_counters();
  }
}

#endif


// Helper class for registering on_exit calls through JVM_OnExit

extern "C" {
    typedef void (*__exit_proc)(void);
}

class ExitProc : public CHeapObj {
 private:
  __exit_proc _proc;
  // void (*_proc)(void);
  ExitProc* _next;
 public:
  // ExitProc(void (*proc)(void)) {
  ExitProc(__exit_proc proc) {
    _proc = proc;
    _next = NULL;
  }
  void evaluate()               { _proc(); }
  ExitProc* next() const        { return _next; }
  void set_next(ExitProc* next) { _next = next; }
};


// Linked list of registered on_exit procedures

static ExitProc* exit_procs = NULL;


extern "C" {
  void register_on_exit_function(void (*func)(void)) {
    ExitProc *entry = new ExitProc(func);
    // Classic vm does not throw an exception in case the allocation failed,
    if (entry != NULL) {
      entry->set_next(exit_procs);
      exit_procs = entry;
    }
  }
}

// Note: before_exit() can be executed only once, if more than one threads
//       are trying to shutdown the VM at the same time, only one thread
//       can run before_exit() and all other threads must wait.
void before_exit(JavaThread * thread) {
  #define BEFORE_EXIT_NOT_RUN 0
  #define BEFORE_EXIT_RUNNING 1
  #define BEFORE_EXIT_DONE    2
  static jint volatile _before_exit_status = BEFORE_EXIT_NOT_RUN;

  // Note: don't use a Mutex to guard the entire before_exit(), as
  // JVMTI post_thread_end_event and post_vm_death_event will run native code.
  // A CAS or OSMutex would work just fine but then we need to manipulate
  // thread state for Safepoint. Here we use Monitor wait() and notify_all()
  // for synchronization.
  { MutexLocker ml(BeforeExit_lock);
    switch (_before_exit_status) {
    case BEFORE_EXIT_NOT_RUN:
      _before_exit_status = BEFORE_EXIT_RUNNING;
      break;
    case BEFORE_EXIT_RUNNING:
      while (_before_exit_status == BEFORE_EXIT_RUNNING) {
        BeforeExit_lock->wait();
      }
      assert(_before_exit_status == BEFORE_EXIT_DONE, "invalid state");
      return;
    case BEFORE_EXIT_DONE:
      return;
    }
  }

  // The only difference between this and Win32's _onexit procs is that
  // this version is invoked before any threads get killed.
  ExitProc* current = exit_procs;
  while (current != NULL) {
    ExitProc* next = current->next();
    current->evaluate();
    delete current;
    current = next;
  }

  // Hang forever on exit if we're reporting an error.
  if (ShowMessageBoxOnError && is_error_reported()) {
    os::infinite_sleep();
  }

  // Terminate watcher thread - must before disenrolling any periodic task
  if (PeriodicTask::num_tasks() > 0)
    WatcherThread::stop();

  // Print statistics gathered (profiling ...)
  if (Arguments::has_profile()) {
    FlatProfiler::disengage();
    FlatProfiler::print(10);
  }

  // shut down the StatSampler task
  StatSampler::disengage();
  StatSampler::destroy();

  // We do not need to explicitly stop concurrent GC threads because the
  // JVM will be taken down at a safepoint when such threads are inactive --
  // except for some concurrent G1 threads, see (comment in)
  // Threads::destroy_vm().

  // Print GC/heap related information.
  if (PrintGCDetails) {
    Universe::print();
    AdaptiveSizePolicyOutput(0);
  }


  if (Arguments::has_alloc_profile()) {
    HandleMark hm;
    // Do one last collection to enumerate all the objects
    // allocated since the last one.
    Universe::heap()->collect(GCCause::_allocation_profiler);
    AllocationProfiler::disengage();
    AllocationProfiler::print(0);
  }

  if (PrintBytecodeHistogram) {
    BytecodeHistogram::print();
  }

  if (JvmtiExport::should_post_thread_life()) {
    JvmtiExport::post_thread_end(thread);
  }
  // Always call even when there are not JVMTI environments yet, since environments
  // may be attached late and JVMTI must track phases of VM execution
  JvmtiExport::post_vm_death();
  Threads::shutdown_vm_agents();

  // Terminate the signal thread
  // Note: we don't wait until it actually dies.
  os::terminate_signal_thread();

  print_statistics();
  Universe::heap()->print_tracing_info();

  { MutexLocker ml(BeforeExit_lock);
    _before_exit_status = BEFORE_EXIT_DONE;
    BeforeExit_lock->notify_all();
  }

  #undef BEFORE_EXIT_NOT_RUN
  #undef BEFORE_EXIT_RUNNING
  #undef BEFORE_EXIT_DONE
}

void vm_exit(int code) {
  Thread* thread = ThreadLocalStorage::is_initialized() ?
    ThreadLocalStorage::get_thread_slow() : NULL;
  if (thread == NULL) {
    // we have serious problems -- just exit
    vm_direct_exit(code);
  }

  if (VMThread::vm_thread() != NULL) {
    // Fire off a VM_Exit operation to bring VM to a safepoint and exit
    VM_Exit op(code);
    if (thread->is_Java_thread())
      ((JavaThread*)thread)->set_thread_state(_thread_in_vm);
    VMThread::execute(&op);
    // should never reach here; but in case something wrong with VM Thread.
    vm_direct_exit(code);
  } else {
    // VM thread is gone, just exit
    vm_direct_exit(code);
  }
  ShouldNotReachHere();
}

void notify_vm_shutdown() {
  // For now, just a dtrace probe.
  HS_DTRACE_PROBE(hotspot, vm__shutdown);
  HS_DTRACE_WORKAROUND_TAIL_CALL_BUG();
}

void vm_direct_exit(int code) {
  notify_vm_shutdown();
  os::wait_for_keypress_at_exit();
  ::exit(code);
}

void vm_perform_shutdown_actions() {
  // Warning: do not call 'exit_globals()' here. All threads are still running.
  // Calling 'exit_globals()' will disable thread-local-storage and cause all
  // kinds of assertions to trigger in debug mode.
  if (is_init_completed()) {
    Thread* thread = ThreadLocalStorage::is_initialized() ?
                     ThreadLocalStorage::get_thread_slow() : NULL;
    if (thread != NULL && thread->is_Java_thread()) {
      // We are leaving the VM, set state to native (in case any OS exit
      // handlers call back to the VM)
      JavaThread* jt = (JavaThread*)thread;
      // Must always be walkable or have no last_Java_frame when in
      // thread_in_native
      jt->frame_anchor()->make_walkable(jt);
      jt->set_thread_state(_thread_in_native);
    }
  }
  notify_vm_shutdown();
}

void vm_shutdown()
{
  vm_perform_shutdown_actions();
  os::wait_for_keypress_at_exit();
  os::shutdown();
}

void vm_abort(bool dump_core) {
  vm_perform_shutdown_actions();
  os::wait_for_keypress_at_exit();
  os::abort(dump_core);
  ShouldNotReachHere();
}

void vm_notify_during_shutdown(const char* error, const char* message) {
  if (error != NULL) {
    tty->print_cr("Error occurred during initialization of VM");
    tty->print("%s", error);
    if (message != NULL) {
      tty->print_cr(": %s", message);
    }
    else {
      tty->cr();
    }
  }
  if (ShowMessageBoxOnError && WizardMode) {
    fatal("Error occurred during initialization of VM");
  }
}

void vm_exit_during_initialization(Handle exception) {
  tty->print_cr("Error occurred during initialization of VM");
  // If there are exceptions on this thread it must be cleared
  // first and here. Any future calls to EXCEPTION_MARK requires
  // that no pending exceptions exist.
  Thread *THREAD = Thread::current();
  if (HAS_PENDING_EXCEPTION) {
    CLEAR_PENDING_EXCEPTION;
  }
  java_lang_Throwable::print(exception, tty);
  tty->cr();
  java_lang_Throwable::print_stack_trace(exception(), tty);
  tty->cr();
  vm_notify_during_shutdown(NULL, NULL);

  // Failure during initialization, we don't want to dump core
  vm_abort(false);
}

void vm_exit_during_initialization(Symbol* ex, const char* message) {
  ResourceMark rm;
  vm_notify_during_shutdown(ex->as_C_string(), message);

  // Failure during initialization, we don't want to dump core
  vm_abort(false);
}

void vm_exit_during_initialization(const char* error, const char* message) {
  vm_notify_during_shutdown(error, message);

  // Failure during initialization, we don't want to dump core
  vm_abort(false);
}

void vm_shutdown_during_initialization(const char* error, const char* message) {
  vm_notify_during_shutdown(error, message);
  vm_shutdown();
}

JDK_Version JDK_Version::_current;

void JDK_Version::initialize() {
  jdk_version_info info;
  assert(!_current.is_valid(), "Don't initialize twice");

  void *lib_handle = os::native_java_library();
  jdk_version_info_fn_t func = CAST_TO_FN_PTR(jdk_version_info_fn_t,
     os::dll_lookup(lib_handle, "JDK_GetVersionInfo0"));

  if (func == NULL) {
    // JDK older than 1.6
    _current._partially_initialized = true;
  } else {
    (*func)(&info, sizeof(info));

    int major = JDK_VERSION_MAJOR(info.jdk_version);
    int minor = JDK_VERSION_MINOR(info.jdk_version);
    int micro = JDK_VERSION_MICRO(info.jdk_version);
    int build = JDK_VERSION_BUILD(info.jdk_version);
    if (major == 1 && minor > 4) {
      // We represent "1.5.0" as "5.0", but 1.4.2 as itself.
      major = minor;
      minor = micro;
      micro = 0;
    }
    _current = JDK_Version(major, minor, micro, info.update_version,
                           info.special_update_version, build,
                           info.thread_park_blocker == 1,
                           info.post_vm_init_hook_enabled == 1,
                           info.pending_list_uses_discovered_field == 1);
  }
}

void JDK_Version::fully_initialize(
    uint8_t major, uint8_t minor, uint8_t micro, uint8_t update) {
  // This is only called when current is less than 1.6 and we've gotten
  // far enough in the initialization to determine the exact version.
  assert(major < 6, "not needed for JDK version >= 6");
  assert(is_partially_initialized(), "must not initialize");
  if (major < 5) {
    // JDK verison sequence: 1.2.x, 1.3.x, 1.4.x, 5.0.x, 6.0.x, etc.
    micro = minor;
    minor = major;
    major = 1;
  }
  _current = JDK_Version(major, minor, micro, update);
}

void JDK_Version_init() {
  JDK_Version::initialize();
}

static int64_t encode_jdk_version(const JDK_Version& v) {
  return
    ((int64_t)v.major_version()          << (BitsPerByte * 5)) |
    ((int64_t)v.minor_version()          << (BitsPerByte * 4)) |
    ((int64_t)v.micro_version()          << (BitsPerByte * 3)) |
    ((int64_t)v.update_version()         << (BitsPerByte * 2)) |
    ((int64_t)v.special_update_version() << (BitsPerByte * 1)) |
    ((int64_t)v.build_number()           << (BitsPerByte * 0));
}

int JDK_Version::compare(const JDK_Version& other) const {
  assert(is_valid() && other.is_valid(), "Invalid version (uninitialized?)");
  if (!is_partially_initialized() && other.is_partially_initialized()) {
    return -(other.compare(*this)); // flip the comparators
  }
  assert(!other.is_partially_initialized(), "Not initialized yet");
  if (is_partially_initialized()) {
    assert(other.major_version() >= 6,
           "Invalid JDK version comparison during initialization");
    return -1;
  } else {
    uint64_t e = encode_jdk_version(*this);
    uint64_t o = encode_jdk_version(other);
    return (e > o) ? 1 : ((e == o) ? 0 : -1);
  }
}

void JDK_Version::to_string(char* buffer, size_t buflen) const {
  size_t index = 0;
  if (!is_valid()) {
    jio_snprintf(buffer, buflen, "%s", "(uninitialized)");
  } else if (is_partially_initialized()) {
    jio_snprintf(buffer, buflen, "%s", "(uninitialized) pre-1.6.0");
  } else {
    index += jio_snprintf(
        &buffer[index], buflen - index, "%d.%d", _major, _minor);
    if (_micro > 0) {
      index += jio_snprintf(&buffer[index], buflen - index, ".%d", _micro);
    }
    if (_update > 0) {
      index += jio_snprintf(&buffer[index], buflen - index, "_%02d", _update);
    }
    if (_special > 0) {
      index += jio_snprintf(&buffer[index], buflen - index, "%c", _special);
    }
    if (_build > 0) {
      index += jio_snprintf(&buffer[index], buflen - index, "-b%02d", _build);
    }
  }
}