CSE2410 Fall 2014 Bounce

// Copyright 2012 the V8 project authors. All rights reserved.

// Redistribution and use in source and binary forms, with or without

// modification, are permitted provided that the following conditions are

// met:

//

//     * Redistributions of source code must retain the above copyright

//       notice, this list of conditions and the following disclaimer.

//     * Redistributions in binary form must reproduce the above

//       copyright notice, this list of conditions and the following

//       disclaimer in the documentation and/or other materials provided

//       with the distribution.

//     * Neither the name of Google Inc. nor the names of its

//       contributors may be used to endorse or promote products derived

//       from this software without specific prior written permission.

//

// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR

// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT

// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,

// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT

// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,

// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY

// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE

// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

#include <stdlib.h>

#include "v8.h"

#include "allocation-inl.h"

#include "ast.h"

#include "bootstrapper.h"

#include "codegen.h"

#include "compilation-cache.h"

#include "cpu-profiler.h"

#include "debug.h"

#include "deoptimizer.h"

#include "heap-profiler.h"

#include "hydrogen.h"

#include "isolate-inl.h"

#include "lithium-allocator.h"

#include "log.h"

#include "messages.h"

#include "platform.h"

#include "regexp-stack.h"

#include "runtime-profiler.h"

#include "sampler.h"

#include "scopeinfo.h"

#include "serialize.h"

#include "simulator.h"

#include "spaces.h"

#include "stub-cache.h"

#include "sweeper-thread.h"

#include "utils/random-number-generator.h"

#include "version.h"

#include "vm-state-inl.h"

namespace v8 {

namespace internal {

Atomic32 ThreadId::highest_thread_id_ = 0;

int ThreadId::AllocateThreadId() {

  int new_id = NoBarrier_AtomicIncrement(&highest_thread_id_, 1);

  return new_id;

}

int ThreadId::GetCurrentThreadId() {

  int thread_id = Thread::GetThreadLocalInt(Isolate::thread_id_key_);

  if (thread_id == 0) {

    thread_id = AllocateThreadId();

    Thread::SetThreadLocalInt(Isolate::thread_id_key_, thread_id);

  }

  return thread_id;

}

ThreadLocalTop::ThreadLocalTop() {

  InitializeInternal();

  // This flag may be set using v8::V8::IgnoreOutOfMemoryException()

  // before an isolate is initialized. The initialize methods below do

  // not touch it to preserve its value.

  ignore_out_of_memory_ = false;

}

void ThreadLocalTop::InitializeInternal() {

  c_entry_fp_ = 0;

  handler_ = 0;

#ifdef USE_SIMULATOR

  simulator_ = NULL;

#endif

  js_entry_sp_ = NULL;

  external_callback_scope_ = NULL;

  current_vm_state_ = EXTERNAL;

  try_catch_handler_address_ = NULL;

  context_ = NULL;

  thread_id_ = ThreadId::Invalid();

  external_caught_exception_ = false;

  failed_access_check_callback_ = NULL;

  save_context_ = NULL;

  catcher_ = NULL;

  top_lookup_result_ = NULL;

  // These members are re-initialized later after deserialization

  // is complete.

  pending_exception_ = NULL;

  has_pending_message_ = false;

  rethrowing_message_ = false;

  pending_message_obj_ = NULL;

  pending_message_script_ = NULL;

  scheduled_exception_ = NULL;

}

void ThreadLocalTop::Initialize() {

  InitializeInternal();

#ifdef USE_SIMULATOR

  simulator_ = Simulator::current(isolate_);

#endif

  thread_id_ = ThreadId::Current();

}

v8::TryCatch* ThreadLocalTop::TryCatchHandler() {

  return TRY_CATCH_FROM_ADDRESS(try_catch_handler_address());

}

int SystemThreadManager::NumberOfParallelSystemThreads(

    ParallelSystemComponent type) {

  int number_of_threads = Min(CPU::NumberOfProcessorsOnline(), kMaxThreads);

  ASSERT(number_of_threads > 0);

  if (number_of_threads ==  1) {

    return 0;

  }

  if (type == PARALLEL_SWEEPING) {

    return number_of_threads;

  } else if (type == CONCURRENT_SWEEPING) {

    return number_of_threads - 1;

  }

  return 1;

}

// Create a dummy thread that will wait forever on a semaphore. The only

// purpose for this thread is to have some stack area to save essential data

// into for use by a stacks only core dump (aka minidump).

class PreallocatedMemoryThread: public Thread {

 public:

  char* data() {

    if (data_ready_semaphore_ != NULL) {

      // Initial access is guarded until the data has been published.

      data_ready_semaphore_->Wait();

      delete data_ready_semaphore_;

      data_ready_semaphore_ = NULL;

    }

    return data_;

  }

  unsigned length() {

    if (data_ready_semaphore_ != NULL) {

      // Initial access is guarded until the data has been published.

      data_ready_semaphore_->Wait();

      delete data_ready_semaphore_;

      data_ready_semaphore_ = NULL;

    }

    return length_;

  }

  // Stop the PreallocatedMemoryThread and release its resources.

  void StopThread() {

    keep_running_ = false;

    wait_for_ever_semaphore_->Signal();

    // Wait for the thread to terminate.

    Join();

    if (data_ready_semaphore_ != NULL) {

      delete data_ready_semaphore_;

      data_ready_semaphore_ = NULL;

    }

    delete wait_for_ever_semaphore_;

    wait_for_ever_semaphore_ = NULL;

  }

 protected:

  // When the thread starts running it will allocate a fixed number of bytes

  // on the stack and publish the location of this memory for others to use.

  void Run() {

    EmbeddedVector<char, 15 * 1024> local_buffer;

    // Initialize the buffer with a known good value.

    OS::StrNCpy(local_buffer, "Trace data was not generated.\n",

                local_buffer.length());

    // Publish the local buffer and signal its availability.

    data_ = local_buffer.start();

    length_ = local_buffer.length();

    data_ready_semaphore_->Signal();

    while (keep_running_) {

      // This thread will wait here until the end of time.

      wait_for_ever_semaphore_->Wait();

    }

    // Make sure we access the buffer after the wait to remove all possibility

    // of it being optimized away.

    OS::StrNCpy(local_buffer, "PreallocatedMemoryThread shutting down.\n",

                local_buffer.length());

  }

 private:

  PreallocatedMemoryThread()

      : Thread("v8:PreallocMem"),

        keep_running_(true),

        wait_for_ever_semaphore_(new Semaphore(0)),

        data_ready_semaphore_(new Semaphore(0)),

        data_(NULL),

        length_(0) {

  }

  // Used to make sure that the thread keeps looping even for spurious wakeups.

  bool keep_running_;

  // This semaphore is used by the PreallocatedMemoryThread to wait for ever.

  Semaphore* wait_for_ever_semaphore_;

  // Semaphore to signal that the data has been initialized.

  Semaphore* data_ready_semaphore_;

  // Location and size of the preallocated memory block.

  char* data_;

  unsigned length_;

  friend class Isolate;

  DISALLOW_COPY_AND_ASSIGN(PreallocatedMemoryThread);

};

void Isolate::PreallocatedMemoryThreadStart() {

  if (preallocated_memory_thread_ != NULL) return;

  preallocated_memory_thread_ = new PreallocatedMemoryThread();

  preallocated_memory_thread_->Start();

}

void Isolate::PreallocatedMemoryThreadStop() {

  if (preallocated_memory_thread_ == NULL) return;

  preallocated_memory_thread_->StopThread();

  // Done with the thread entirely.

  delete preallocated_memory_thread_;

  preallocated_memory_thread_ = NULL;

}

void Isolate::PreallocatedStorageInit(size_t size) {

  ASSERT(free_list_.next_ == &free_list_);

  ASSERT(free_list_.previous_ == &free_list_);

  PreallocatedStorage* free_chunk =

      reinterpret_cast<PreallocatedStorage*>(new char[size]);

  free_list_.next_ = free_list_.previous_ = free_chunk;

  free_chunk->next_ = free_chunk->previous_ = &free_list_;

  free_chunk->size_ = size - sizeof(PreallocatedStorage);

  preallocated_storage_preallocated_ = true;

}

void* Isolate::PreallocatedStorageNew(size_t size) {

  if (!preallocated_storage_preallocated_) {

    return FreeStoreAllocationPolicy().New(size);

  }

  ASSERT(free_list_.next_ != &free_list_);

  ASSERT(free_list_.previous_ != &free_list_);

  size = (size + kPointerSize - 1) & ~(kPointerSize - 1);

  // Search for exact fit.

  for (PreallocatedStorage* storage = free_list_.next_;

       storage != &free_list_;

       storage = storage->next_) {

    if (storage->size_ == size) {

      storage->Unlink();

      storage->LinkTo(&in_use_list_);

      return reinterpret_cast<void*>(storage + 1);

    }

  }

  // Search for first fit.

  for (PreallocatedStorage* storage = free_list_.next_;

       storage != &free_list_;

       storage = storage->next_) {

    if (storage->size_ >= size + sizeof(PreallocatedStorage)) {

      storage->Unlink();

      storage->LinkTo(&in_use_list_);

      PreallocatedStorage* left_over =

          reinterpret_cast<PreallocatedStorage*>(

              reinterpret_cast<char*>(storage + 1) + size);

      left_over->size_ = storage->size_ - size - sizeof(PreallocatedStorage);

      ASSERT(size + left_over->size_ + sizeof(PreallocatedStorage) ==

             storage->size_);

      storage->size_ = size;

      left_over->LinkTo(&free_list_);

      return reinterpret_cast<void*>(storage + 1);

    }

  }

  // Allocation failure.

  ASSERT(false);

  return NULL;

}

// We don't attempt to coalesce.

void Isolate::PreallocatedStorageDelete(void* p) {

  if (p == NULL) {

    return;

  }

  if (!preallocated_storage_preallocated_) {

    FreeStoreAllocationPolicy::Delete(p);

    return;

  }

  PreallocatedStorage* storage = reinterpret_cast<PreallocatedStorage*>(p) - 1;

  ASSERT(storage->next_->previous_ == storage);

  ASSERT(storage->previous_->next_ == storage);

  storage->Unlink();

  storage->LinkTo(&free_list_);

}

Isolate* Isolate::default_isolate_ = NULL;

Thread::LocalStorageKey Isolate::isolate_key_;

Thread::LocalStorageKey Isolate::thread_id_key_;

Thread::LocalStorageKey Isolate::per_isolate_thread_data_key_;

#ifdef DEBUG

Thread::LocalStorageKey PerThreadAssertScopeBase::thread_local_key;

#endif  // DEBUG

Mutex Isolate::process_wide_mutex_;

// TODO(dcarney): Remove with default isolate.

enum DefaultIsolateStatus {

  kDefaultIsolateUninitialized,

  kDefaultIsolateInitialized,

  kDefaultIsolateCrashIfInitialized

};

static DefaultIsolateStatus default_isolate_status_

    = kDefaultIsolateUninitialized;

Isolate::ThreadDataTable* Isolate::thread_data_table_ = NULL;

Atomic32 Isolate::isolate_counter_ = 0;

Isolate::PerIsolateThreadData*

    Isolate::FindOrAllocatePerThreadDataForThisThread() {

  ThreadId thread_id = ThreadId::Current();

  PerIsolateThreadData* per_thread = NULL;

  {

    LockGuard<Mutex> lock_guard(&process_wide_mutex_);

    per_thread = thread_data_table_->Lookup(this, thread_id);

    if (per_thread == NULL) {

      per_thread = new PerIsolateThreadData(this, thread_id);

      thread_data_table_->Insert(per_thread);

    }

  }

  ASSERT(thread_data_table_->Lookup(this, thread_id) == per_thread);

  return per_thread;

}

Isolate::PerIsolateThreadData* Isolate::FindPerThreadDataForThisThread() {

  ThreadId thread_id = ThreadId::Current();

  return FindPerThreadDataForThread(thread_id);

}

Isolate::PerIsolateThreadData* Isolate::FindPerThreadDataForThread(

    ThreadId thread_id) {

  PerIsolateThreadData* per_thread = NULL;

  {

    LockGuard<Mutex> lock_guard(&process_wide_mutex_);

    per_thread = thread_data_table_->Lookup(this, thread_id);

  }

  return per_thread;

}

void Isolate::SetCrashIfDefaultIsolateInitialized() {

  LockGuard<Mutex> lock_guard(&process_wide_mutex_);

  CHECK(default_isolate_status_ != kDefaultIsolateInitialized);

  default_isolate_status_ = kDefaultIsolateCrashIfInitialized;

}

void Isolate::EnsureDefaultIsolate() {

  LockGuard<Mutex> lock_guard(&process_wide_mutex_);

  CHECK(default_isolate_status_ != kDefaultIsolateCrashIfInitialized);

  if (default_isolate_ == NULL) {

    isolate_key_ = Thread::CreateThreadLocalKey();

    thread_id_key_ = Thread::CreateThreadLocalKey();

    per_isolate_thread_data_key_ = Thread::CreateThreadLocalKey();

#ifdef DEBUG

    PerThreadAssertScopeBase::thread_local_key = Thread::CreateThreadLocalKey();

#endif  // DEBUG

    thread_data_table_ = new Isolate::ThreadDataTable();

    default_isolate_ = new Isolate();

  }

  // Can't use SetIsolateThreadLocals(default_isolate_, NULL) here

  // because a non-null thread data may be already set.

  if (Thread::GetThreadLocal(isolate_key_) == NULL) {

    Thread::SetThreadLocal(isolate_key_, default_isolate_);

  }

}

struct StaticInitializer {

  StaticInitializer() {

    Isolate::EnsureDefaultIsolate();

  }

} static_initializer;

#ifdef ENABLE_DEBUGGER_SUPPORT

Debugger* Isolate::GetDefaultIsolateDebugger() {

  EnsureDefaultIsolate();

  return default_isolate_->debugger();

}

#endif

StackGuard* Isolate::GetDefaultIsolateStackGuard() {

  EnsureDefaultIsolate();

  return default_isolate_->stack_guard();

}

void Isolate::EnterDefaultIsolate() {

  EnsureDefaultIsolate();

  ASSERT(default_isolate_ != NULL);

  PerIsolateThreadData* data = CurrentPerIsolateThreadData();

  // If not yet in default isolate - enter it.

  if (data == NULL || data->isolate() != default_isolate_) {

    default_isolate_->Enter();

  }

}

v8::Isolate* Isolate::GetDefaultIsolateForLocking() {

  EnsureDefaultIsolate();

  return reinterpret_cast<v8::Isolate*>(default_isolate_);

}

Address Isolate::get_address_from_id(Isolate::AddressId id) {

  return isolate_addresses_[id];

}

char* Isolate::Iterate(ObjectVisitor* v, char* thread_storage) {

  ThreadLocalTop* thread = reinterpret_cast<ThreadLocalTop*>(thread_storage);

  Iterate(v, thread);

  return thread_storage + sizeof(ThreadLocalTop);

}

void Isolate::IterateThread(ThreadVisitor* v, char* t) {

  ThreadLocalTop* thread = reinterpret_cast<ThreadLocalTop*>(t);

  v->VisitThread(this, thread);

}

void Isolate::Iterate(ObjectVisitor* v, ThreadLocalTop* thread) {

  // Visit the roots from the top for a given thread.

  Object* pending;

  // The pending exception can sometimes be a failure.  We can't show

  // that to the GC, which only understands objects.

  if (thread->pending_exception_->ToObject(&pending)) {

    v->VisitPointer(&pending);

    thread->pending_exception_ = pending;  // In case GC updated it.

  }

  v->VisitPointer(&(thread->pending_message_obj_));

  v->VisitPointer(BitCast<Object**>(&(thread->pending_message_script_)));

  v->VisitPointer(BitCast<Object**>(&(thread->context_)));

  Object* scheduled;

  if (thread->scheduled_exception_->ToObject(&scheduled)) {

    v->VisitPointer(&scheduled);

    thread->scheduled_exception_ = scheduled;

  }

  for (v8::TryCatch* block = thread->TryCatchHandler();

       block != NULL;

       block = TRY_CATCH_FROM_ADDRESS(block->next_)) {

    v->VisitPointer(BitCast<Object**>(&(block->exception_)));

    v->VisitPointer(BitCast<Object**>(&(block->message_obj_)));

    v->VisitPointer(BitCast<Object**>(&(block->message_script_)));

  }

  // Iterate over pointers on native execution stack.

  for (StackFrameIterator it(this, thread); !it.done(); it.Advance()) {

    it.frame()->Iterate(v);

  }

  // Iterate pointers in live lookup results.

  thread->top_lookup_result_->Iterate(v);

}

void Isolate::Iterate(ObjectVisitor* v) {

  ThreadLocalTop* current_t = thread_local_top();

  Iterate(v, current_t);

}

void Isolate::IterateDeferredHandles(ObjectVisitor* visitor) {

  for (DeferredHandles* deferred = deferred_handles_head_;

       deferred != NULL;

       deferred = deferred->next_) {

    deferred->Iterate(visitor);

  }

}

#ifdef DEBUG

bool Isolate::IsDeferredHandle(Object** handle) {

  // Each DeferredHandles instance keeps the handles to one job in the

  // concurrent recompilation queue, containing a list of blocks.  Each block

  // contains kHandleBlockSize handles except for the first block, which may

  // not be fully filled.

  // We iterate through all the blocks to see whether the argument handle

  // belongs to one of the blocks.  If so, it is deferred.

  for (DeferredHandles* deferred = deferred_handles_head_;

       deferred != NULL;

       deferred = deferred->next_) {

    List<Object**>* blocks = &deferred->blocks_;

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

      Object** block_limit = (i == 0) ? deferred->first_block_limit_

                                      : blocks->at(i) + kHandleBlockSize;

      if (blocks->at(i) <= handle && handle < block_limit) return true;

    }

  }

  return false;

}

#endif  // DEBUG

void Isolate::RegisterTryCatchHandler(v8::TryCatch* that) {

  // The ARM simulator has a separate JS stack.  We therefore register

  // the C++ try catch handler with the simulator and get back an

  // address that can be used for comparisons with addresses into the

  // JS stack.  When running without the simulator, the address

  // returned will be the address of the C++ try catch handler itself.

  Address address = reinterpret_cast<Address>(

      SimulatorStack::RegisterCTryCatch(reinterpret_cast<uintptr_t>(that)));

  thread_local_top()->set_try_catch_handler_address(address);

}

void Isolate::UnregisterTryCatchHandler(v8::TryCatch* that) {

  ASSERT(thread_local_top()->TryCatchHandler() == that);

  thread_local_top()->set_try_catch_handler_address(

      reinterpret_cast<Address>(that->next_));

  thread_local_top()->catcher_ = NULL;

  SimulatorStack::UnregisterCTryCatch();

}

Handle<String> Isolate::StackTraceString() {

  if (stack_trace_nesting_level_ == 0) {

    stack_trace_nesting_level_++;

    HeapStringAllocator allocator;

    StringStream::ClearMentionedObjectCache(this);

    StringStream accumulator(&allocator);

    incomplete_message_ = &accumulator;

    PrintStack(&accumulator);

    Handle<String> stack_trace = accumulator.ToString(this);

    incomplete_message_ = NULL;

    stack_trace_nesting_level_ = 0;

    return stack_trace;

  } else if (stack_trace_nesting_level_ == 1) {

    stack_trace_nesting_level_++;

    OS::PrintError(

      "\n\nAttempt to print stack while printing stack (double fault)\n");

    OS::PrintError(

      "If you are lucky you may find a partial stack dump on stdout.\n\n");

    incomplete_message_->OutputToStdOut();

    return factory()->empty_string();

  } else {

    OS::Abort();

    // Unreachable

    return factory()->empty_string();

  }

}

void Isolate::PushStackTraceAndDie(unsigned int magic,

                                   Object* object,

                                   Map* map,

                                   unsigned int magic2) {

  const int kMaxStackTraceSize = 8192;

  Handle<String> trace = StackTraceString();

  uint8_t buffer[kMaxStackTraceSize];

  int length = Min(kMaxStackTraceSize - 1, trace->length());

  String::WriteToFlat(*trace, buffer, 0, length);

  buffer[length] = '\0';

  // TODO(dcarney): convert buffer to utf8?

  OS::PrintError("Stacktrace (%x-%x) %p %p: %s\n",

                 magic, magic2,

                 static_cast<void*>(object), static_cast<void*>(map),

                 reinterpret_cast<char*>(buffer));

  OS::Abort();

}

// Determines whether the given stack frame should be displayed in

// a stack trace.  The caller is the error constructor that asked

// for the stack trace to be collected.  The first time a construct

// call to this function is encountered it is skipped.  The seen_caller

// in/out parameter is used to remember if the caller has been seen

// yet.

static bool IsVisibleInStackTrace(StackFrame* raw_frame,

                                  Object* caller,

                                  bool* seen_caller) {

  // Only display JS frames.

  if (!raw_frame->is_java_script()) return false;

  JavaScriptFrame* frame = JavaScriptFrame::cast(raw_frame);

  JSFunction* fun = frame->function();

  if ((fun == caller) && !(*seen_caller)) {

    *seen_caller = true;

    return false;

  }

  // Skip all frames until we've seen the caller.

  if (!(*seen_caller)) return false;

  // Also, skip non-visible built-in functions and any call with the builtins

  // object as receiver, so as to not reveal either the builtins object or

  // an internal function.

  // The --builtins-in-stack-traces command line flag allows including

  // internal call sites in the stack trace for debugging purposes.

  if (!FLAG_builtins_in_stack_traces) {

    if (frame->receiver()->IsJSBuiltinsObject() ||

        (fun->IsBuiltin() && !fun->shared()->native())) {

      return false;

    }

  }

  return true;

}

Handle<JSArray> Isolate::CaptureSimpleStackTrace(Handle<JSObject> error_object,

                                                 Handle<Object> caller,

                                                 int limit) {

  limit = Max(limit, 0);  // Ensure that limit is not negative.

  int initial_size = Min(limit, 10);

  Handle<FixedArray> elements =

      factory()->NewFixedArrayWithHoles(initial_size * 4 + 1);

  // If the caller parameter is a function we skip frames until we're

  // under it before starting to collect.

  bool seen_caller = !caller->IsJSFunction();

  // First element is reserved to store the number of non-strict frames.

  int cursor = 1;

  int frames_seen = 0;

  int non_strict_frames = 0;

  bool encountered_strict_function = false;

  for (StackFrameIterator iter(this);

       !iter.done() && frames_seen < limit;

       iter.Advance()) {

    StackFrame* raw_frame = iter.frame();

    if (IsVisibleInStackTrace(raw_frame, *caller, &seen_caller)) {

      frames_seen++;

      JavaScriptFrame* frame = JavaScriptFrame::cast(raw_frame);

      // Set initial size to the maximum inlining level + 1 for the outermost

      // function.

      List<FrameSummary> frames(FLAG_max_inlining_levels + 1);

      frame->Summarize(&frames);

      for (int i = frames.length() - 1; i >= 0; i--) {

        if (cursor + 4 > elements->length()) {

          int new_capacity = JSObject::NewElementsCapacity(elements->length());

          Handle<FixedArray> new_elements =

              factory()->NewFixedArrayWithHoles(new_capacity);

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

            new_elements->set(i, elements->get(i));

          }

          elements = new_elements;

        }

        ASSERT(cursor + 4 <= elements->length());

        Handle<Object> recv = frames[i].receiver();

        Handle<JSFunction> fun = frames[i].function();

        Handle<Code> code = frames[i].code();

        Handle<Smi> offset(Smi::FromInt(frames[i].offset()), this);

        // The stack trace API should not expose receivers and function

        // objects on frames deeper than the top-most one with a strict

        // mode function.  The number of non-strict frames is stored as

        // first element in the result array.

        if (!encountered_strict_function) {

          if (!fun->shared()->is_classic_mode()) {

            encountered_strict_function = true;

          } else {

            non_strict_frames++;

          }

        }

        elements->set(cursor++, *recv);

        elements->set(cursor++, *fun);

        elements->set(cursor++, *code);

        elements->set(cursor++, *offset);

      }

    }

  }

  elements->set(0, Smi::FromInt(non_strict_frames));

  Handle<JSArray> result = factory()->NewJSArrayWithElements(elements);

  result->set_length(Smi::FromInt(cursor));

  return result;

}

void Isolate::CaptureAndSetDetailedStackTrace(Handle<JSObject> error_object) {

  if (capture_stack_trace_for_uncaught_exceptions_) {

    // Capture stack trace for a detailed exception message.

    Handle<String> key = factory()->hidden_stack_trace_string();

    Handle<JSArray> stack_trace = CaptureCurrentStackTrace(

        stack_trace_for_uncaught_exceptions_frame_limit_,

        stack_trace_for_uncaught_exceptions_options_);

    JSObject::SetHiddenProperty(error_object, key, stack_trace);

  }

}

Handle<JSArray> Isolate::CaptureCurrentStackTrace(

    int frame_limit, StackTrace::StackTraceOptions options) {

  // Ensure no negative values.

  int limit = Max(frame_limit, 0);

  Handle<JSArray> stack_trace = factory()->NewJSArray(frame_limit);

  Handle<String> column_key =

      factory()->InternalizeOneByteString(STATIC_ASCII_VECTOR("column"));

  Handle<String> line_key =

      factory()->InternalizeOneByteString(STATIC_ASCII_VECTOR("lineNumber"));

  Handle<String> script_id_key =

      factory()->InternalizeOneByteString(STATIC_ASCII_VECTOR("scriptId"));

  Handle<String> script_name_key =

      factory()->InternalizeOneByteString(STATIC_ASCII_VECTOR("scriptName"));

  Handle<String> script_name_or_source_url_key =

      factory()->InternalizeOneByteString(

          STATIC_ASCII_VECTOR("scriptNameOrSourceURL"));

  Handle<String> function_key =

      factory()->InternalizeOneByteString(STATIC_ASCII_VECTOR("functionName"));

  Handle<String> eval_key =

      factory()->InternalizeOneByteString(STATIC_ASCII_VECTOR("isEval"));

  Handle<String> constructor_key =

      factory()->InternalizeOneByteString(STATIC_ASCII_VECTOR("isConstructor"));

  StackTraceFrameIterator it(this);

  int frames_seen = 0;

  while (!it.done() && (frames_seen < limit)) {

    JavaScriptFrame* frame = it.frame();

    // Set initial size to the maximum inlining level + 1 for the outermost

    // function.

    List<FrameSummary> frames(FLAG_max_inlining_levels + 1);

    frame->Summarize(&frames);

    for (int i = frames.length() - 1; i >= 0 && frames_seen < limit; i--) {

      // Create a JSObject to hold the information for the StackFrame.

      Handle<JSObject> stack_frame = factory()->NewJSObject(object_function());

      Handle<JSFunction> fun = frames[i].function();

      Handle<Script> script(Script::cast(fun->shared()->script()));

      if (options & StackTrace::kLineNumber) {

        int script_line_offset = script->line_offset()->value();

        int position = frames[i].code()->SourcePosition(frames[i].pc());

        int line_number = GetScriptLineNumber(script, position);

        // line_number is already shifted by the script_line_offset.

        int relative_line_number = line_number - script_line_offset;

        if (options & StackTrace::kColumnOffset && relative_line_number >= 0) {

          Handle<FixedArray> line_ends(FixedArray::cast(script->line_ends()));

          int start = (relative_line_number == 0) ? 0 :

              Smi::cast(line_ends->get(relative_line_number - 1))->value() + 1;

          int column_offset = position - start;

          if (relative_line_number == 0) {

            // For the case where the code is on the same line as the script

            // tag.

            column_offset += script->column_offset()->value();

          }

          CHECK_NOT_EMPTY_HANDLE(

              this,

              JSObject::SetLocalPropertyIgnoreAttributes(

                  stack_frame, column_key,

                  Handle<Smi>(Smi::FromInt(column_offset + 1), this), NONE));

        }

        CHECK_NOT_EMPTY_HANDLE(

            this,

            JSObject::SetLocalPropertyIgnoreAttributes(

                stack_frame, line_key,

                Handle<Smi>(Smi::FromInt(line_number + 1), this), NONE));

      }

      if (options & StackTrace::kScriptId) {

        Handle<Smi> script_id(script->id(), this);

        CHECK_NOT_EMPTY_HANDLE(this,

                               JSObject::SetLocalPropertyIgnoreAttributes(

                                   stack_frame, script_id_key, script_id,

                                   NONE));

      }

      if (options & StackTrace::kScriptName) {

        Handle<Object> script_name(script->name(), this);

        CHECK_NOT_EMPTY_HANDLE(this,

                               JSObject::SetLocalPropertyIgnoreAttributes(

                                   stack_frame, script_name_key, script_name,

                                   NONE));

      }

      if (options & StackTrace::kScriptNameOrSourceURL) {

        Handle<Object> result = GetScriptNameOrSourceURL(script);

        CHECK_NOT_EMPTY_HANDLE(this,

                               JSObject::SetLocalPropertyIgnoreAttributes(

                                   stack_frame, script_name_or_source_url_key,

                                   result, NONE));

      }

      if (options & StackTrace::kFunctionName) {

        Handle<Object> fun_name(fun->shared()->name(), this);

        if (!fun_name->BooleanValue()) {

          fun_name = Handle<Object>(fun->shared()->inferred_name(), this);

        }

        CHECK_NOT_EMPTY_HANDLE(this,

                               JSObject::SetLocalPropertyIgnoreAttributes(

                                   stack_frame, function_key, fun_name, NONE));

      }

      if (options & StackTrace::kIsEval) {

        Handle<Object> is_eval =

            script->compilation_type() == Script::COMPILATION_TYPE_EVAL ?

                factory()->true_value() : factory()->false_value();

        CHECK_NOT_EMPTY_HANDLE(this,

                               JSObject::SetLocalPropertyIgnoreAttributes(

                                   stack_frame, eval_key, is_eval, NONE));

      }

      if (options & StackTrace::kIsConstructor) {

        Handle<Object> is_constructor = (frames[i].is_constructor()) ?

            factory()->true_value() : factory()->false_value();

        CHECK_NOT_EMPTY_HANDLE(this,

                               JSObject::SetLocalPropertyIgnoreAttributes(

                                   stack_frame, constructor_key,

                                   is_constructor, NONE));

      }

      FixedArray::cast(stack_trace->elements())->set(frames_seen, *stack_frame);

      frames_seen++;

    }

    it.Advance();

  }

  stack_trace->set_length(Smi::FromInt(frames_seen));

  return stack_trace;

}

void Isolate::PrintStack() {

  PrintStack(stdout);

}

void Isolate::PrintStack(FILE* out) {

  if (stack_trace_nesting_level_ == 0) {

    stack_trace_nesting_level_++;

    StringAllocator* allocator;

    if (preallocated_message_space_ == NULL) {

      allocator = new HeapStringAllocator();

    } else {

      allocator = preallocated_message_space_;

    }

    StringStream::ClearMentionedObjectCache(this);

    StringStream accumulator(allocator);

    incomplete_message_ = &accumulator;

    PrintStack(&accumulator);

    accumulator.OutputToFile(out);

    InitializeLoggingAndCounters();

    accumulator.Log(this);

    incomplete_message_ = NULL;

    stack_trace_nesting_level_ = 0;

    if (preallocated_message_space_ == NULL) {

      // Remove the HeapStringAllocator created above.

      delete allocator;

    }

  } else if (stack_trace_nesting_level_ == 1) {

    stack_trace_nesting_level_++;

    OS::PrintError(

      "\n\nAttempt to print stack while printing stack (double fault)\n");

    OS::PrintError(

      "If you are lucky you may find a partial stack dump on stdout.\n\n");

    incomplete_message_->OutputToFile(out);

  }

}

static void PrintFrames(Isolate* isolate,

                        StringStream* accumulator,

                        StackFrame::PrintMode mode) {

  StackFrameIterator it(isolate);

  for (int i = 0; !it.done(); it.Advance()) {

    it.frame()->Print(accumulator, mode, i++);

  }

}

void Isolate::PrintStack(StringStream* accumulator) {

  if (!IsInitialized()) {

    accumulator->Add(

        "\n==== JS stack trace is not available =======================\n\n");

    accumulator->Add(

        "\n==== Isolate for the thread is not initialized =============\n\n");

    return;

  }

  // The MentionedObjectCache is not GC-proof at the moment.

  DisallowHeapAllocation no_gc;

  ASSERT(StringStream::IsMentionedObjectCacheClear(this));

  // Avoid printing anything if there are no frames.

  if (c_entry_fp(thread_local_top()) == 0) return;

  accumulator->Add(

      "\n==== JS stack trace =========================================\n\n");

  PrintFrames(this, accumulator, StackFrame::OVERVIEW);

  accumulator->Add(

      "\n==== Details ================================================\n\n");

  PrintFrames(this, accumulator, StackFrame::DETAILS);

  accumulator->PrintMentionedObjectCache(this);

  accumulator->Add("=====================\n\n");

}

void Isolate::SetFailedAccessCheckCallback(

    v8::FailedAccessCheckCallback callback) {

  thread_local_top()->failed_access_check_callback_ = callback;

}

void Isolate::ReportFailedAccessCheck(JSObject* receiver, v8::AccessType type) {

  if (!thread_local_top()->failed_access_check_callback_) return;

  ASSERT(receiver->IsAccessCheckNeeded());

  ASSERT(context());

  // Get the data object from access check info.

  JSFunction* constructor = JSFunction::cast(receiver->map()->constructor());

  if (!constructor->shared()->IsApiFunction()) return;

  Object* data_obj =

      constructor->shared()->get_api_func_data()->access_check_info();

  if (data_obj == heap_.undefined_value()) return;

  HandleScope scope(this);

  Handle<JSObject> receiver_handle(receiver);

  Handle<Object> data(AccessCheckInfo::cast(data_obj)->data(), this);

  { VMState<EXTERNAL> state(this);

    thread_local_top()->failed_access_check_callback_(

      v8::Utils::ToLocal(receiver_handle),

      type,

      v8::Utils::ToLocal(data));

  }

}

enum MayAccessDecision {

  YES, NO, UNKNOWN

};

static MayAccessDecision MayAccessPreCheck(Isolate* isolate,

                                           JSObject* receiver,

                                           v8::AccessType type) {

  // During bootstrapping, callback functions are not enabled yet.

  if (isolate->bootstrapper()->IsActive()) return YES;

  if (receiver->IsJSGlobalProxy()) {

    Object* receiver_context = JSGlobalProxy::cast(receiver)->native_context();

    if (!receiver_context->IsContext()) return NO;

    // Get the native context of current top context.

    // avoid using Isolate::native_context() because it uses Handle.

    Context* native_context =

        isolate->context()->global_object()->native_context();

    if (receiver_context == native_context) return YES;

    if (Context::cast(receiver_context)->security_token() ==

        native_context->security_token())

      return YES;

  }

  return UNKNOWN;

}

bool Isolate::MayNamedAccess(JSObject* receiver, Object* key,

                             v8::AccessType type) {

  ASSERT(receiver->IsAccessCheckNeeded());

  // The callers of this method are not expecting a GC.

  DisallowHeapAllocation no_gc;

  // Skip checks for hidden properties access.  Note, we do not

  // require existence of a context in this case.

  if (key == heap_.hidden_string()) return true;

  // Check for compatibility between the security tokens in the

  // current lexical context and the accessed object.

  ASSERT(context());

  MayAccessDecision decision = MayAccessPreCheck(this, receiver, type);

  if (decision != UNKNOWN) return decision == YES;

  // Get named access check callback

  JSFunction* constructor = JSFunction::cast(receiver->map()->constructor());

  if (!constructor->shared()->IsApiFunction()) return false;

  Object* data_obj =

     constructor->shared()->get_api_func_data()->access_check_info();

  if (data_obj == heap_.undefined_value()) return false;

  Object* fun_obj = AccessCheckInfo::cast(data_obj)->named_callback();

  v8::NamedSecurityCallback callback =

      v8::ToCData<v8::NamedSecurityCallback>(fun_obj);

  if (!callback) return false;

  HandleScope scope(this);

  Handle<JSObject> receiver_handle(receiver, this);

  Handle<Object> key_handle(key, this);

  Handle<Object> data(AccessCheckInfo::cast(data_obj)->data(), this);

  LOG(this, ApiNamedSecurityCheck(key));

  bool result = false;

  {

    // Leaving JavaScript.

    VMState<EXTERNAL> state(this);

    result = callback(v8::Utils::ToLocal(receiver_handle),

                      v8::Utils::ToLocal(key_handle),

                      type,

                      v8::Utils::ToLocal(data));

  }

  return result;

}

bool Isolate::MayIndexedAccess(JSObject* receiver,

                               uint32_t index,

                               v8::AccessType type) {

  ASSERT(receiver->IsAccessCheckNeeded());

  // Check for compatibility between the security tokens in the

  // current lexical context and the accessed object.

  ASSERT(context());

  MayAccessDecision decision = MayAccessPreCheck(this, receiver, type);

  if (decision != UNKNOWN) return decision == YES;

  // Get indexed access check callback

  JSFunction* constructor = JSFunction::cast(receiver->map()->constructor());

  if (!constructor->shared()->IsApiFunction()) return false;

  Object* data_obj =

      constructor->shared()->get_api_func_data()->access_check_info();

  if (data_obj == heap_.undefined_value()) return false;

  Object* fun_obj = AccessCheckInfo::cast(data_obj)->indexed_callback();

  v8::IndexedSecurityCallback callback =

      v8::ToCData<v8::IndexedSecurityCallback>(fun_obj);

  if (!callback) return false;

  HandleScope scope(this);

  Handle<JSObject> receiver_handle(receiver, this);

  Handle<Object> data(AccessCheckInfo::cast(data_obj)->data(), this);

  LOG(this, ApiIndexedSecurityCheck(index));

  bool result = false;

  {

    // Leaving JavaScript.

    VMState<EXTERNAL> state(this);

    result = callback(v8::Utils::ToLocal(receiver_handle),

                      index,

                      type,

                      v8::Utils::ToLocal(data));

  }

  return result;

}

const char* const Isolate::kStackOverflowMessage =

  "Uncaught RangeError: Maximum call stack size exceeded";

Failure* Isolate::StackOverflow() {

  HandleScope scope(this);

  // At this point we cannot create an Error object using its javascript

  // constructor.  Instead, we copy the pre-constructed boilerplate and

  // attach the stack trace as a hidden property.

  Handle<String> key = factory()->stack_overflow_string();

  Handle<JSObject> boilerplate =

      Handle<JSObject>::cast(GetProperty(this, js_builtins_object(), key));

  Handle<JSObject> exception = JSObject::Copy(boilerplate);

  DoThrow(*exception, NULL);

  // Get stack trace limit.

  Handle<Object> error = GetProperty(js_builtins_object(), "$Error");

  if (!error->IsJSObject()) return Failure::Exception();

  Handle<Object> stack_trace_limit =

      GetProperty(Handle<JSObject>::cast(error), "stackTraceLimit");

  if (!stack_trace_limit->IsNumber()) return Failure::Exception();

  double dlimit = stack_trace_limit->Number();

  int limit = std::isnan(dlimit) ? 0 : static_cast<int>(dlimit);

  Handle<JSArray> stack_trace = CaptureSimpleStackTrace(

      exception, factory()->undefined_value(), limit);

  JSObject::SetHiddenProperty(exception,

                              factory()->hidden_stack_trace_string(),

                              stack_trace);

  return Failure::Exception();

}

Failure* Isolate::TerminateExecution() {

  DoThrow(heap_.termination_exception(), NULL);

  return Failure::Exception();

}

void Isolate::CancelTerminateExecution() {

  if (try_catch_handler()) {

    try_catch_handler()->has_terminated_ = false;

  }

  if (has_pending_exception() &&

      pending_exception() == heap_.termination_exception()) {

    thread_local_top()->external_caught_exception_ = false;

    clear_pending_exception();

  }

  if (has_scheduled_exception() &&

      scheduled_exception() == heap_.termination_exception()) {

    thread_local_top()->external_caught_exception_ = false;

    clear_scheduled_exception();

  }

}

Failure* Isolate::Throw(Object* exception, MessageLocation* location) {

  DoThrow(exception, location);

  return Failure::Exception();

}

Failure* Isolate::ReThrow(MaybeObject* exception) {

  bool can_be_caught_externally = false;

  bool catchable_by_javascript = is_catchable_by_javascript(exception);

  ShouldReportException(&can_be_caught_externally, catchable_by_javascript);

  thread_local_top()->catcher_ = can_be_caught_externally ?

      try_catch_handler() : NULL;

  // Set the exception being re-thrown.

  set_pending_exception(exception);

  if (exception->IsFailure()) return exception->ToFailureUnchecked();

  return Failure::Exception();

}

Failure* Isolate::ThrowIllegalOperation() {

  return Throw(heap_.illegal_access_string());

}

void Isolate::ScheduleThrow(Object* exception) {

  // When scheduling a throw we first throw the exception to get the

  // error reporting if it is uncaught before rescheduling it.

  Throw(exception);

  PropagatePendingExceptionToExternalTryCatch();

  if (has_pending_exception()) {

    thread_local_top()->scheduled_exception_ = pending_exception();

    thread_local_top()->external_caught_exception_ = false;

    clear_pending_exception();

  }

}

void Isolate::RestorePendingMessageFromTryCatch(v8::TryCatch* handler) {

  ASSERT(handler == try_catch_handler());

  ASSERT(handler->HasCaught());

  ASSERT(handler->rethrow_);

  ASSERT(handler->capture_message_);

  Object* message = reinterpret_cast<Object*>(handler->message_obj_);

  Object* script = reinterpret_cast<Object*>(handler->message_script_);

  ASSERT(message->IsJSMessageObject() || message->IsTheHole());

  ASSERT(script->IsScript() || script->IsTheHole());

  thread_local_top()->pending_message_obj_ = message;

  thread_local_top()->pending_message_script_ = script;

  thread_local_top()->pending_message_start_pos_ = handler->message_start_pos_;

  thread_local_top()->pending_message_end_pos_ = handler->message_end_pos_;

}

Failure* Isolate::PromoteScheduledException() {

  MaybeObject* thrown = scheduled_exception();

  clear_scheduled_exception();

  // Re-throw the exception to avoid getting repeated error reporting.

  return ReThrow(thrown);

}

void Isolate::PrintCurrentStackTrace(FILE* out) {

  StackTraceFrameIterator it(this);

  while (!it.done()) {

    HandleScope scope(this);

    // Find code position if recorded in relocation info.

    JavaScriptFrame* frame = it.frame();

    int pos = frame->LookupCode()->SourcePosition(frame->pc());

    Handle<Object> pos_obj(Smi::FromInt(pos), this);

    // Fetch function and receiver.

    Handle<JSFunction> fun(frame->function());

    Handle<Object> recv(frame->receiver(), this);

    // Advance to the next JavaScript frame and determine if the

    // current frame is the top-level frame.

    it.Advance();

    Handle<Object> is_top_level = it.done()

        ? factory()->true_value()

        : factory()->false_value();

    // Generate and print stack trace line.

    Handle<String> line =

        Execution::GetStackTraceLine(recv, fun, pos_obj, is_top_level);

    if (line->length() > 0) {

      line->PrintOn(out);

      PrintF(out, "\n");

    }

  }

}

void Isolate::ComputeLocation(MessageLocation* target) {

  *target = MessageLocation(Handle<Script>(heap_.empty_script()), -1, -1);

  StackTraceFrameIterator it(this);

  if (!it.done()) {

    JavaScriptFrame* frame = it.frame();

    JSFunction* fun = frame->function();

    Object* script = fun->shared()->script();

    if (script->IsScript() &&

        !(Script::cast(script)->source()->IsUndefined())) {

      int pos = frame->LookupCode()->SourcePosition(frame->pc());

      // Compute the location from the function and the reloc info.

      Handle<Script> casted_script(Script::cast(script));

      *target = MessageLocation(casted_script, pos, pos + 1);

    }

  }

}

bool Isolate::ShouldReportException(bool* can_be_caught_externally,

                                    bool catchable_by_javascript) {

  // Find the top-most try-catch handler.

  StackHandler* handler =

      StackHandler::FromAddress(Isolate::handler(thread_local_top()));

  while (handler != NULL && !handler->is_catch()) {

    handler = handler->next();

  }

  // Get the address of the external handler so we can compare the address to

  // determine which one is closer to the top of the stack.

  Address external_handler_address =

      thread_local_top()->try_catch_handler_address();

  // The exception has been externally caught if and only if there is

  // an external handler which is on top of the top-most try-catch

  // handler.

  *can_be_caught_externally = external_handler_address != NULL &&

      (handler == NULL || handler->address() > external_handler_address ||

       !catchable_by_javascript);

  if (*can_be_caught_externally) {

    // Only report the exception if the external handler is verbose.

    return try_catch_handler()->is_verbose_;

  } else {

    // Report the exception if it isn't caught by JavaScript code.

    return handler == NULL;

  }

}

bool Isolate::IsErrorObject(Handle<Object> obj) {

  if (!obj->IsJSObject()) return false;

  String* error_key =

      *(factory()->InternalizeOneByteString(STATIC_ASCII_VECTOR("$Error")));

  Object* error_constructor =

      js_builtins_object()->GetPropertyNoExceptionThrown(error_key);

  for (Object* prototype = *obj; !prototype->IsNull();

       prototype = prototype->GetPrototype(this)) {

    if (!prototype->IsJSObject()) return false;

    if (JSObject::cast(prototype)->map()->constructor() == error_constructor) {

      return true;

    }

  }

  return false;

}

static int fatal_exception_depth = 0;

void Isolate::DoThrow(Object* exception, MessageLocation* location) {

  ASSERT(!has_pending_exception());

  HandleScope scope(this);

  Handle<Object> exception_handle(exception, this);

  // Determine reporting and whether the exception is caught externally.

  bool catchable_by_javascript = is_catchable_by_javascript(exception);

  bool can_be_caught_externally = false;

  bool should_report_exception =

      ShouldReportException(&can_be_caught_externally, catchable_by_javascript);

  bool report_exception = catchable_by_javascript && should_report_exception;

  bool try_catch_needs_message =

      can_be_caught_externally && try_catch_handler()->capture_message_ &&

      !thread_local_top()->rethrowing_message_;

  bool bootstrapping = bootstrapper()->IsActive();

  thread_local_top()->rethrowing_message_ = false;

#ifdef ENABLE_DEBUGGER_SUPPORT

  // Notify debugger of exception.

  if (catchable_by_javascript) {

    debugger_->OnException(exception_handle, report_exception);

  }

#endif

  // Generate the message if required.

  if (report_exception || try_catch_needs_message) {

    MessageLocation potential_computed_location;

    if (location == NULL) {

      // If no location was specified we use a computed one instead.

      ComputeLocation(&potential_computed_location);

      location = &potential_computed_location;

    }

    // It's not safe to try to make message objects or collect stack traces

    // while the bootstrapper is active since the infrastructure may not have

    // been properly initialized.

    if (!bootstrapping) {

      Handle<String> stack_trace;

      if (FLAG_trace_exception) stack_trace = StackTraceString();

      Handle<JSArray> stack_trace_object;

      if (capture_stack_trace_for_uncaught_exceptions_) {

        if (IsErrorObject(exception_handle)) {

          // We fetch the stack trace that corresponds to this error object.

          String* key = heap()->hidden_stack_trace_string();

          Object* stack_property =

              JSObject::cast(*exception_handle)->GetHiddenProperty(key);

          // Property lookup may have failed.  In this case it's probably not

          // a valid Error object.

          if (stack_property->IsJSArray()) {

            stack_trace_object = Handle<JSArray>(JSArray::cast(stack_property));

          }

        }

        if (stack_trace_object.is_null()) {

          // Not an error object, we capture at throw site.

          stack_trace_object = CaptureCurrentStackTrace(

              stack_trace_for_uncaught_exceptions_frame_limit_,

              stack_trace_for_uncaught_exceptions_options_);

        }

      }

      Handle<Object> exception_arg = exception_handle;

      // If the exception argument is a custom object, turn it into a string

      // before throwing as uncaught exception.  Note that the pending

      // exception object to be set later must not be turned into a string.

      if (exception_arg->IsJSObject() && !IsErrorObject(exception_arg)) {

        bool failed = false;

        exception_arg =

            Execution::ToDetailString(this, exception_arg, &failed);

        if (failed) {

          exception_arg = factory()->InternalizeOneByteString(

              STATIC_ASCII_VECTOR("exception"));

        }

      }

      Handle<Object> message_obj = MessageHandler::MakeMessageObject(

          this,

          "uncaught_exception",

          location,

          HandleVector<Object>(&exception_arg, 1),

          stack_trace,

          stack_trace_object);

      thread_local_top()->pending_message_obj_ = *message_obj;

      if (location != NULL) {

        thread_local_top()->pending_message_script_ = *location->script();

        thread_local_top()->pending_message_start_pos_ = location->start_pos();

        thread_local_top()->pending_message_end_pos_ = location->end_pos();

      }

      // If the abort-on-uncaught-exception flag is specified, abort on any

      // exception not caught by JavaScript, even when an external handler is

      // present.  This flag is intended for use by JavaScript developers, so