text: // 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 "v8.h"
  
  #include "api.h"
  #include "arguments.h"
  #include "bootstrapper.h"
  #include "code-stubs.h"
  #include "codegen.h"
  #include "compilation-cache.h"
  #include "compiler.h"
  #include "debug.h"
  #include "deoptimizer.h"
  #include "execution.h"
  #include "full-codegen.h"
  #include "global-handles.h"
  #include "ic.h"
  #include "ic-inl.h"
  #include "isolate-inl.h"
  #include "list.h"
  #include "messages.h"
  #include "natives.h"
  #include "stub-cache.h"
  #include "log.h"
  
  #include "../include/v8-debug.h"
  
  namespace v8 {
  namespace internal {
  
  #ifdef ENABLE_DEBUGGER_SUPPORT
  
  
  Debug::Debug(Isolate* isolate)
      : has_break_points_(false),
        script_cache_(NULL),
        debug_info_list_(NULL),
        disable_break_(false),
        break_on_exception_(false),
        break_on_uncaught_exception_(false),
        debug_break_return_(NULL),
        debug_break_slot_(NULL),
        isolate_(isolate) {
    memset(registers_, 0, sizeof(JSCallerSavedBuffer));
  }
  
  
  Debug::~Debug() {
  }
  
  
  static void PrintLn(v8::Local<v8::Value> value) {
    v8::Local<v8::String> s = value->ToString();
    ScopedVector<char> data(s->Utf8Length() + 1);
    if (data.start() == NULL) {
      V8::FatalProcessOutOfMemory("PrintLn");
      return;
    }
    s->WriteUtf8(data.start());
    PrintF("%s\n", data.start());
  }
  
  
  static v8::Handle<v8::Context> GetDebugEventContext(Isolate* isolate) {
    Handle<Context> context = isolate->debug()->debugger_entry()->GetContext();
    // Isolate::context() may have been NULL when "script collected" event
    // occured.
    if (context.is_null()) return v8::Local<v8::Context>();
    Handle<Context> native_context(context->native_context());
    return v8::Utils::ToLocal(native_context);
  }
  
  
  BreakLocationIterator::BreakLocationIterator(Handle<DebugInfo> debug_info,
                                               BreakLocatorType type) {
    debug_info_ = debug_info;
    type_ = type;
    reloc_iterator_ = NULL;
    reloc_iterator_original_ = NULL;
    Reset();  // Initialize the rest of the member variables.
  }
  
  
  BreakLocationIterator::~BreakLocationIterator() {
    ASSERT(reloc_iterator_ != NULL);
    ASSERT(reloc_iterator_original_ != NULL);
    delete reloc_iterator_;
    delete reloc_iterator_original_;
  }
  
  
  void BreakLocationIterator::Next() {
    DisallowHeapAllocation no_gc;
    ASSERT(!RinfoDone());
  
    // Iterate through reloc info for code and original code stopping at each
    // breakable code target.
    bool first = break_point_ == -1;
    while (!RinfoDone()) {
      if (!first) RinfoNext();
      first = false;
      if (RinfoDone()) return;
  
      // Whenever a statement position or (plain) position is passed update the
      // current value of these.
      if (RelocInfo::IsPosition(rmode())) {
        if (RelocInfo::IsStatementPosition(rmode())) {
          statement_position_ = static_cast<int>(
              rinfo()->data() - debug_info_->shared()->start_position());
        }
        // Always update the position as we don't want that to be before the
        // statement position.
        position_ = static_cast<int>(
            rinfo()->data() - debug_info_->shared()->start_position());
        ASSERT(position_ >= 0);
        ASSERT(statement_position_ >= 0);
      }
  
      if (IsDebugBreakSlot()) {
        // There is always a possible break point at a debug break slot.
        break_point_++;
        return;
      } else if (RelocInfo::IsCodeTarget(rmode())) {
        // Check for breakable code target. Look in the original code as setting
        // break points can cause the code targets in the running (debugged) code
        // to be of a different kind than in the original code.
        Address target = original_rinfo()->target_address();
        Code* code = Code::GetCodeFromTargetAddress(target);
        if ((code->is_inline_cache_stub() &&
             !code->is_binary_op_stub() &&
             !code->is_compare_ic_stub() &&
             !code->is_to_boolean_ic_stub()) ||
            RelocInfo::IsConstructCall(rmode())) {
          break_point_++;
          return;
        }
        if (code->kind() == Code::STUB) {
          if (IsDebuggerStatement()) {
            break_point_++;
            return;
          }
          if (type_ == ALL_BREAK_LOCATIONS) {
            if (Debug::IsBreakStub(code)) {
              break_point_++;
              return;
            }
          } else {
            ASSERT(type_ == SOURCE_BREAK_LOCATIONS);
            if (Debug::IsSourceBreakStub(code)) {
              break_point_++;
              return;
            }
          }
        }
      }
  
      // Check for break at return.
      if (RelocInfo::IsJSReturn(rmode())) {
        // Set the positions to the end of the function.
        if (debug_info_->shared()->HasSourceCode()) {
          position_ = debug_info_->shared()->end_position() -
                      debug_info_->shared()->start_position() - 1;
        } else {
          position_ = 0;
        }
        statement_position_ = position_;
        break_point_++;
        return;
      }
    }
  }
  
  
  void BreakLocationIterator::Next(int count) {
    while (count > 0) {
      Next();
      count--;
    }
  }
  
  
  // Find the break point at the supplied address, or the closest one before
  // the address.
  void BreakLocationIterator::FindBreakLocationFromAddress(Address pc) {
    // Run through all break points to locate the one closest to the address.
    int closest_break_point = 0;
    int distance = kMaxInt;
    while (!Done()) {
      // Check if this break point is closer that what was previously found.
      if (this->pc() <= pc && pc - this->pc() < distance) {
        closest_break_point = break_point();
        distance = static_cast<int>(pc - this->pc());
        // Check whether we can't get any closer.
        if (distance == 0) break;
      }
      Next();
    }
  
    // Move to the break point found.
    Reset();
    Next(closest_break_point);
  }
  
  
  // Find the break point closest to the supplied source position.
  void BreakLocationIterator::FindBreakLocationFromPosition(int position,
      BreakPositionAlignment alignment) {
    // Run through all break points to locate the one closest to the source
    // position.
    int closest_break_point = 0;
    int distance = kMaxInt;
  
    while (!Done()) {
      int next_position;
      switch (alignment) {
      case STATEMENT_ALIGNED:
        next_position = this->statement_position();
        break;
      case BREAK_POSITION_ALIGNED:
        next_position = this->position();
        break;
      default:
        UNREACHABLE();
        next_position = this->statement_position();
      }
      // Check if this break point is closer that what was previously found.
      if (position <= next_position && next_position - position < distance) {
        closest_break_point = break_point();
        distance = next_position - position;
        // Check whether we can't get any closer.
        if (distance == 0) break;
      }
      Next();
    }
  
    // Move to the break point found.
    Reset();
    Next(closest_break_point);
  }
  
  
  void BreakLocationIterator::Reset() {
    // Create relocation iterators for the two code objects.
    if (reloc_iterator_ != NULL) delete reloc_iterator_;
    if (reloc_iterator_original_ != NULL) delete reloc_iterator_original_;
    reloc_iterator_ = new RelocIterator(
        debug_info_->code(),
        ~RelocInfo::ModeMask(RelocInfo::CODE_AGE_SEQUENCE));
    reloc_iterator_original_ = new RelocIterator(
        debug_info_->original_code(),
        ~RelocInfo::ModeMask(RelocInfo::CODE_AGE_SEQUENCE));
  
    // Position at the first break point.
    break_point_ = -1;
    position_ = 1;
    statement_position_ = 1;
    Next();
  }
  
  
  bool BreakLocationIterator::Done() const {
    return RinfoDone();
  }
  
  
  void BreakLocationIterator::SetBreakPoint(Handle<Object> break_point_object) {
    // If there is not already a real break point here patch code with debug
    // break.
    if (!HasBreakPoint()) {
      SetDebugBreak();
    }
    ASSERT(IsDebugBreak() || IsDebuggerStatement());
    // Set the break point information.
    DebugInfo::SetBreakPoint(debug_info_, code_position(),
                             position(), statement_position(),
                             break_point_object);
  }
  
  
  void BreakLocationIterator::ClearBreakPoint(Handle<Object> break_point_object) {
    // Clear the break point information.
    DebugInfo::ClearBreakPoint(debug_info_, code_position(), break_point_object);
    // If there are no more break points here remove the debug break.
    if (!HasBreakPoint()) {
      ClearDebugBreak();
      ASSERT(!IsDebugBreak());
    }
  }
  
  
  void BreakLocationIterator::SetOneShot() {
    // Debugger statement always calls debugger. No need to modify it.
    if (IsDebuggerStatement()) {
      return;
    }
  
    // If there is a real break point here no more to do.
    if (HasBreakPoint()) {
      ASSERT(IsDebugBreak());
      return;
    }
  
    // Patch code with debug break.
    SetDebugBreak();
  }
  
  
  void BreakLocationIterator::ClearOneShot() {
    // Debugger statement always calls debugger. No need to modify it.
    if (IsDebuggerStatement()) {
      return;
    }
  
    // If there is a real break point here no more to do.
    if (HasBreakPoint()) {
      ASSERT(IsDebugBreak());
      return;
    }
  
    // Patch code removing debug break.
    ClearDebugBreak();
    ASSERT(!IsDebugBreak());
  }
  
  
  void BreakLocationIterator::SetDebugBreak() {
    // Debugger statement always calls debugger. No need to modify it.
    if (IsDebuggerStatement()) {
      return;
    }
  
    // If there is already a break point here just return. This might happen if
    // the same code is flooded with break points twice. Flooding the same
    // function twice might happen when stepping in a function with an exception
    // handler as the handler and the function is the same.
    if (IsDebugBreak()) {
      return;
    }
  
    if (RelocInfo::IsJSReturn(rmode())) {
      // Patch the frame exit code with a break point.
      SetDebugBreakAtReturn();
    } else if (IsDebugBreakSlot()) {
      // Patch the code in the break slot.
      SetDebugBreakAtSlot();
    } else {
      // Patch the IC call.
      SetDebugBreakAtIC();
    }
    ASSERT(IsDebugBreak());
  }
  
  
  void BreakLocationIterator::ClearDebugBreak() {
    // Debugger statement always calls debugger. No need to modify it.
    if (IsDebuggerStatement()) {
      return;
    }
  
    if (RelocInfo::IsJSReturn(rmode())) {
      // Restore the frame exit code.
      ClearDebugBreakAtReturn();
    } else if (IsDebugBreakSlot()) {
      // Restore the code in the break slot.
      ClearDebugBreakAtSlot();
    } else {
      // Patch the IC call.
      ClearDebugBreakAtIC();
    }
    ASSERT(!IsDebugBreak());
  }
  
  
  bool BreakLocationIterator::IsStepInLocation(Isolate* isolate) {
    if (RelocInfo::IsConstructCall(original_rmode())) {
      return true;
    } else if (RelocInfo::IsCodeTarget(rmode())) {
      HandleScope scope(debug_info_->GetIsolate());
      Address target = original_rinfo()->target_address();
      Handle<Code> target_code(Code::GetCodeFromTargetAddress(target));
      if (target_code->kind() == Code::STUB) {
        return target_code->major_key() == CodeStub::CallFunction;
      }
    }
    return false;
  }
  
  
  void BreakLocationIterator::PrepareStepIn(Isolate* isolate) {
  #ifdef DEBUG
    HandleScope scope(isolate);
    // Step in can only be prepared if currently positioned on an IC call,
    // construct call or CallFunction stub call.
    Address target = rinfo()->target_address();
    Handle<Code> target_code(Code::GetCodeFromTargetAddress(target));
    // All the following stuff is needed only for assertion checks so the code
    // is wrapped in ifdef.
    Handle<Code> maybe_call_function_stub = target_code;
    if (IsDebugBreak()) {
      Address original_target = original_rinfo()->target_address();
      maybe_call_function_stub =
          Handle<Code>(Code::GetCodeFromTargetAddress(original_target));
    }
    bool is_call_function_stub =
        (maybe_call_function_stub->kind() == Code::STUB &&
         maybe_call_function_stub->major_key() == CodeStub::CallFunction);
  
    // Step in through construct call requires no changes to the running code.
    // Step in through getters/setters should already be prepared as well
    // because caller of this function (Debug::PrepareStep) is expected to
    // flood the top frame's function with one shot breakpoints.
    // Step in through CallFunction stub should also be prepared by caller of
    // this function (Debug::PrepareStep) which should flood target function
    // with breakpoints.
    ASSERT(RelocInfo::IsConstructCall(rmode()) ||
           target_code->is_inline_cache_stub() ||
           is_call_function_stub);
  #endif
  }
  
  
  // Check whether the break point is at a position which will exit the function.
  bool BreakLocationIterator::IsExit() const {
    return (RelocInfo::IsJSReturn(rmode()));
  }
  
  
  bool BreakLocationIterator::HasBreakPoint() {
    return debug_info_->HasBreakPoint(code_position());
  }
  
  
  // Check whether there is a debug break at the current position.
  bool BreakLocationIterator::IsDebugBreak() {
    if (RelocInfo::IsJSReturn(rmode())) {
      return IsDebugBreakAtReturn();
    } else if (IsDebugBreakSlot()) {
      return IsDebugBreakAtSlot();
    } else {
      return Debug::IsDebugBreak(rinfo()->target_address());
    }
  }
  
  
  void BreakLocationIterator::SetDebugBreakAtIC() {
    // Patch the original code with the current address as the current address
    // might have changed by the inline caching since the code was copied.
    original_rinfo()->set_target_address(rinfo()->target_address());
  
    RelocInfo::Mode mode = rmode();
    if (RelocInfo::IsCodeTarget(mode)) {
      Address target = rinfo()->target_address();
      Handle<Code> target_code(Code::GetCodeFromTargetAddress(target));
  
      // Patch the code to invoke the builtin debug break function matching the
      // calling convention used by the call site.
      Handle<Code> dbgbrk_code(Debug::FindDebugBreak(target_code, mode));
      rinfo()->set_target_address(dbgbrk_code->entry());
    }
  }
  
  
  void BreakLocationIterator::ClearDebugBreakAtIC() {
    // Patch the code to the original invoke.
    rinfo()->set_target_address(original_rinfo()->target_address());
  }
  
  
  bool BreakLocationIterator::IsDebuggerStatement() {
    return RelocInfo::DEBUG_BREAK == rmode();
  }
  
  
  bool BreakLocationIterator::IsDebugBreakSlot() {
    return RelocInfo::DEBUG_BREAK_SLOT == rmode();
  }
  
  
  Object* BreakLocationIterator::BreakPointObjects() {
    return debug_info_->GetBreakPointObjects(code_position());
  }
  
  
  // Clear out all the debug break code. This is ONLY supposed to be used when
  // shutting down the debugger as it will leave the break point information in
  // DebugInfo even though the code is patched back to the non break point state.
  void BreakLocationIterator::ClearAllDebugBreak() {
    while (!Done()) {
      ClearDebugBreak();
      Next();
    }
  }
  
  
  bool BreakLocationIterator::RinfoDone() const {
    ASSERT(reloc_iterator_->done() == reloc_iterator_original_->done());
    return reloc_iterator_->done();
  }
  
  
  void BreakLocationIterator::RinfoNext() {
    reloc_iterator_->next();
    reloc_iterator_original_->next();
  #ifdef DEBUG
    ASSERT(reloc_iterator_->done() == reloc_iterator_original_->done());
    if (!reloc_iterator_->done()) {
      ASSERT(rmode() == original_rmode());
    }
  #endif
  }
  
  
  // Threading support.
  void Debug::ThreadInit() {
    thread_local_.break_count_ = 0;
    thread_local_.break_id_ = 0;
    thread_local_.break_frame_id_ = StackFrame::NO_ID;
    thread_local_.last_step_action_ = StepNone;
    thread_local_.last_statement_position_ = RelocInfo::kNoPosition;
    thread_local_.step_count_ = 0;
    thread_local_.last_fp_ = 0;
    thread_local_.queued_step_count_ = 0;
    thread_local_.step_into_fp_ = 0;
    thread_local_.step_out_fp_ = 0;
    thread_local_.after_break_target_ = 0;
    // TODO(isolates): frames_are_dropped_?
    thread_local_.debugger_entry_ = NULL;
    thread_local_.pending_interrupts_ = 0;
    thread_local_.restarter_frame_function_pointer_ = NULL;
  }
  
  
  char* Debug::ArchiveDebug(char* storage) {
    char* to = storage;
    OS::MemCopy(to, reinterpret_cast<char*>(&thread_local_), sizeof(ThreadLocal));
    to += sizeof(ThreadLocal);
    OS::MemCopy(to, reinterpret_cast<char*>(&registers_), sizeof(registers_));
    ThreadInit();
    ASSERT(to <= storage + ArchiveSpacePerThread());
    return storage + ArchiveSpacePerThread();
  }
  
  
  char* Debug::RestoreDebug(char* storage) {
    char* from = storage;
    OS::MemCopy(
        reinterpret_cast<char*>(&thread_local_), from, sizeof(ThreadLocal));
    from += sizeof(ThreadLocal);
    OS::MemCopy(reinterpret_cast<char*>(&registers_), from, sizeof(registers_));
    ASSERT(from <= storage + ArchiveSpacePerThread());
    return storage + ArchiveSpacePerThread();
  }
  
  
  int Debug::ArchiveSpacePerThread() {
    return sizeof(ThreadLocal) + sizeof(JSCallerSavedBuffer);
  }
  
  
  // Frame structure (conforms InternalFrame structure):
  //   -- code
  //   -- SMI maker
  //   -- function (slot is called "context")
  //   -- frame base
  Object** Debug::SetUpFrameDropperFrame(StackFrame* bottom_js_frame,
                                         Handle<Code> code) {
    ASSERT(bottom_js_frame->is_java_script());
  
    Address fp = bottom_js_frame->fp();
  
    // Move function pointer into "context" slot.
    Memory::Object_at(fp + StandardFrameConstants::kContextOffset) =
        Memory::Object_at(fp + JavaScriptFrameConstants::kFunctionOffset);
  
    Memory::Object_at(fp + InternalFrameConstants::kCodeOffset) = *code;
    Memory::Object_at(fp + StandardFrameConstants::kMarkerOffset) =
        Smi::FromInt(StackFrame::INTERNAL);
  
    return reinterpret_cast<Object**>(&Memory::Object_at(
        fp + StandardFrameConstants::kContextOffset));
  }
  
  const int Debug::kFrameDropperFrameSize = 4;
  
  
  void ScriptCache::Add(Handle<Script> script) {
    GlobalHandles* global_handles = isolate_->global_handles();
    // Create an entry in the hash map for the script.
    int id = script->id()->value();
    HashMap::Entry* entry =
        HashMap::Lookup(reinterpret_cast<void*>(id), Hash(id), true);
    if (entry->value != NULL) {
      ASSERT(*script == *reinterpret_cast<Script**>(entry->value));
      return;
    }
    // Globalize the script object, make it weak and use the location of the
    // global handle as the value in the hash map.
    Handle<Script> script_ =
        Handle<Script>::cast(global_handles->Create(*script));
    GlobalHandles::MakeWeak(reinterpret_cast<Object**>(script_.location()),
                            this,
                            ScriptCache::HandleWeakScript);
    entry->value = script_.location();
  }
  
  
  Handle<FixedArray> ScriptCache::GetScripts() {
    Factory* factory = isolate_->factory();
    Handle<FixedArray> instances = factory->NewFixedArray(occupancy());
    int count = 0;
    for (HashMap::Entry* entry = Start(); entry != NULL; entry = Next(entry)) {
      ASSERT(entry->value != NULL);
      if (entry->value != NULL) {
        instances->set(count, *reinterpret_cast<Script**>(entry->value));
        count++;
      }
    }
    return instances;
  }
  
  
  void ScriptCache::ProcessCollectedScripts() {
    Debugger* debugger = isolate_->debugger();
    for (int i = 0; i < collected_scripts_.length(); i++) {
      debugger->OnScriptCollected(collected_scripts_[i]);
    }
    collected_scripts_.Clear();
  }
  
  
  void ScriptCache::Clear() {
    // Iterate the script cache to get rid of all the weak handles.
    for (HashMap::Entry* entry = Start(); entry != NULL; entry = Next(entry)) {
      ASSERT(entry != NULL);
      Object** location = reinterpret_cast<Object**>(entry->value);
      ASSERT((*location)->IsScript());
      GlobalHandles::ClearWeakness(location);
      GlobalHandles::Destroy(location);
    }
    // Clear the content of the hash map.
    HashMap::Clear();
  }
  
  
  void ScriptCache::HandleWeakScript(
      const v8::WeakCallbackData<v8::Value, void>& data) {
    // Retrieve the script identifier.
    Handle<Object> object = Utils::OpenHandle(*data.GetValue());
    int id = Handle<Script>::cast(object)->id()->value();
    void* key = reinterpret_cast<void*>(id);
    uint32_t hash = Hash(id);
  
    // Remove the corresponding entry from the cache.
    ScriptCache* script_cache =
        reinterpret_cast<ScriptCache*>(data.GetParameter());
    HashMap::Entry* entry = script_cache->Lookup(key, hash, false);
    Object** location = reinterpret_cast<Object**>(entry->value);
    script_cache->Remove(key, hash);
    script_cache->collected_scripts_.Add(id);
  
    // Clear the weak handle.
    GlobalHandles::Destroy(location);
  }
  
  
  void Debug::SetUp(bool create_heap_objects) {
    ThreadInit();
    if (create_heap_objects) {
      // Get code to handle debug break on return.
      debug_break_return_ =
          isolate_->builtins()->builtin(Builtins::kReturn_DebugBreak);
      ASSERT(debug_break_return_->IsCode());
      // Get code to handle debug break in debug break slots.
      debug_break_slot_ =
          isolate_->builtins()->builtin(Builtins::kSlot_DebugBreak);
      ASSERT(debug_break_slot_->IsCode());
    }
  }
  
  
  void Debug::HandleWeakDebugInfo(
      const v8::WeakCallbackData<v8::Value, void>& data) {
    Debug* debug = reinterpret_cast<Isolate*>(data.GetIsolate())->debug();
    DebugInfoListNode* node =
        reinterpret_cast<DebugInfoListNode*>(data.GetParameter());
    // We need to clear all breakpoints associated with the function to restore
    // original code and avoid patching the code twice later because
    // the function will live in the heap until next gc, and can be found by
    // Debug::FindSharedFunctionInfoInScript.
    BreakLocationIterator it(node->debug_info(), ALL_BREAK_LOCATIONS);
    it.ClearAllDebugBreak();
    debug->RemoveDebugInfo(node->debug_info());
  #ifdef DEBUG
    for (DebugInfoListNode* n = debug->debug_info_list_;
         n != NULL;
         n = n->next()) {
      ASSERT(n != node);
    }
  #endif
  }
  
  
  DebugInfoListNode::DebugInfoListNode(DebugInfo* debug_info): next_(NULL) {
    // Globalize the request debug info object and make it weak.
    GlobalHandles* global_handles = debug_info->GetIsolate()->global_handles();
    debug_info_ = Handle<DebugInfo>::cast(global_handles->Create(debug_info));
    GlobalHandles::MakeWeak(reinterpret_cast<Object**>(debug_info_.location()),
                            this,
                            Debug::HandleWeakDebugInfo);
  }
  
  
  DebugInfoListNode::~DebugInfoListNode() {
    GlobalHandles::Destroy(reinterpret_cast<Object**>(debug_info_.location()));
  }
  
  
  bool Debug::CompileDebuggerScript(Isolate* isolate, int index) {
    Factory* factory = isolate->factory();
    HandleScope scope(isolate);
  
    // Bail out if the index is invalid.
    if (index == -1) {
      return false;
    }
  
    // Find source and name for the requested script.
    Handle<String> source_code =
        isolate->bootstrapper()->NativesSourceLookup(index);
    Vector<const char> name = Natives::GetScriptName(index);
    Handle<String> script_name = factory->NewStringFromAscii(name);
    Handle<Context> context = isolate->native_context();
  
    // Compile the script.
    Handle<SharedFunctionInfo> function_info;
    function_info = Compiler::CompileScript(source_code,
                                            script_name, 0, 0,
                                            false,
                                            context,
                                            NULL, NULL,
                                            Handle<String>::null(),
                                            NATIVES_CODE);
  
    // Silently ignore stack overflows during compilation.
    if (function_info.is_null()) {
      ASSERT(isolate->has_pending_exception());
      isolate->clear_pending_exception();
      return false;
    }
  
    // Execute the shared function in the debugger context.
    bool caught_exception;
    Handle<JSFunction> function =
        factory->NewFunctionFromSharedFunctionInfo(function_info, context);
  
    Handle<Object> exception =
        Execution::TryCall(function,
                           Handle<Object>(context->global_object(), isolate),
                           0,
                           NULL,
                           &caught_exception);
  
    // Check for caught exceptions.
    if (caught_exception) {
      ASSERT(!isolate->has_pending_exception());
      MessageLocation computed_location;
      isolate->ComputeLocation(&computed_location);
      Handle<Object> message = MessageHandler::MakeMessageObject(
          isolate, "error_loading_debugger", &computed_location,
          Vector<Handle<Object> >::empty(), Handle<JSArray>());
      ASSERT(!isolate->has_pending_exception());
      if (!exception.is_null()) {
        isolate->set_pending_exception(*exception);
        MessageHandler::ReportMessage(isolate, NULL, message);
        isolate->clear_pending_exception();
      }
      return false;
    }
  
    // Mark this script as native and return successfully.
    Handle<Script> script(Script::cast(function->shared()->script()));
    script->set_type(Smi::FromInt(Script::TYPE_NATIVE));
    return true;
  }
  
  
  bool Debug::Load() {
    // Return if debugger is already loaded.
    if (IsLoaded()) return true;
  
    Debugger* debugger = isolate_->debugger();
  
    // Bail out if we're already in the process of compiling the native
    // JavaScript source code for the debugger.
    if (debugger->compiling_natives() ||
        debugger->is_loading_debugger())
      return false;
    debugger->set_loading_debugger(true);
  
    // Disable breakpoints and interrupts while compiling and running the
    // debugger scripts including the context creation code.
    DisableBreak disable(isolate_, true);
    PostponeInterruptsScope postpone(isolate_);
  
    // Create the debugger context.
    HandleScope scope(isolate_);
    ExtensionConfiguration no_extensions;
    Handle<Context> context =
        isolate_->bootstrapper()->CreateEnvironment(
            Handle<Object>::null(),
            v8::Handle<ObjectTemplate>(),
            &no_extensions);
  
    // Fail if no context could be created.
    if (context.is_null()) return false;
  
    // Use the debugger context.
    SaveContext save(isolate_);
    isolate_->set_context(*context);
  
    // Expose the builtins object in the debugger context.
    Handle<String> key = isolate_->factory()->InternalizeOneByteString(
        STATIC_ASCII_VECTOR("builtins"));
    Handle<GlobalObject> global = Handle<GlobalObject>(context->global_object());
    RETURN_IF_EMPTY_HANDLE_VALUE(
        isolate_,
        JSReceiver::SetProperty(global,
                                key,
                                Handle<Object>(global->builtins(), isolate_),
                                NONE,
                                kNonStrictMode),
        false);
  
    // Compile the JavaScript for the debugger in the debugger context.
    debugger->set_compiling_natives(true);
    bool caught_exception =
        !CompileDebuggerScript(isolate_, Natives::GetIndex("mirror")) ||
        !CompileDebuggerScript(isolate_, Natives::GetIndex("debug"));
  
    if (FLAG_enable_liveedit) {
      caught_exception = caught_exception ||
          !CompileDebuggerScript(isolate_, Natives::GetIndex("liveedit"));
    }
  
    debugger->set_compiling_natives(false);
  
    // Make sure we mark the debugger as not loading before we might
    // return.
    debugger->set_loading_debugger(false);
  
    // Check for caught exceptions.
    if (caught_exception) return false;
  
    // Debugger loaded, create debugger context global handle.
    debug_context_ = Handle<Context>::cast(
        isolate_->global_handles()->Create(*context));
  
    return true;
  }
  
  
  void Debug::Unload() {
    // Return debugger is not loaded.
    if (!IsLoaded()) {
      return;
    }
  
    // Clear the script cache.
    DestroyScriptCache();
  
    // Clear debugger context global handle.
    GlobalHandles::Destroy(reinterpret_cast<Object**>(debug_context_.location()));
    debug_context_ = Handle<Context>();
  }
  
  
  // Set the flag indicating that preemption happened during debugging.
  void Debug::PreemptionWhileInDebugger() {
    ASSERT(InDebugger());
    Debug::set_interrupts_pending(PREEMPT);
  }
  
  
  void Debug::Iterate(ObjectVisitor* v) {
    v->VisitPointer(BitCast<Object**>(&(debug_break_return_)));
    v->VisitPointer(BitCast<Object**>(&(debug_break_slot_)));
  }
  
  
  Object* Debug::Break(Arguments args) {
    Heap* heap = isolate_->heap();
    HandleScope scope(isolate_);
    ASSERT(args.length() == 0);
  
    thread_local_.frame_drop_mode_ = FRAMES_UNTOUCHED;
  
    // Get the top-most JavaScript frame.
    JavaScriptFrameIterator it(isolate_);
    JavaScriptFrame* frame = it.frame();
  
    // Just continue if breaks are disabled or debugger cannot be loaded.
    if (disable_break() || !Load()) {
      SetAfterBreakTarget(frame);
      return heap->undefined_value();
    }
  
    // Enter the debugger.
    EnterDebugger debugger(isolate_);
    if (debugger.FailedToEnter()) {
      return heap->undefined_value();
    }
  
    // Postpone interrupt during breakpoint processing.
    PostponeInterruptsScope postpone(isolate_);
  
    // Get the debug info (create it if it does not exist).
    Handle<SharedFunctionInfo> shared =
        Handle<SharedFunctionInfo>(frame->function()->shared());
    Handle<DebugInfo> debug_info = GetDebugInfo(shared);
  
    // Find the break point where execution has stopped.
    BreakLocationIterator break_location_iterator(debug_info,
                                                  ALL_BREAK_LOCATIONS);
    // pc points to the instruction after the current one, possibly a break
    // location as well. So the "- 1" to exclude it from the search.
    break_location_iterator.FindBreakLocationFromAddress(frame->pc() - 1);
  
    // Check whether step next reached a new statement.
    if (!StepNextContinue(&break_location_iterator, frame)) {
      // Decrease steps left if performing multiple steps.
      if (thread_local_.step_count_ > 0) {
        thread_local_.step_count_--;
      }
    }
  
    // If there is one or more real break points check whether any of these are
    // triggered.
    Handle<Object> break_points_hit(heap->undefined_value(), isolate_);
    if (break_location_iterator.HasBreakPoint()) {
      Handle<Object> break_point_objects =
          Handle<Object>(break_location_iterator.BreakPointObjects(), isolate_);
      break_points_hit = CheckBreakPoints(break_point_objects);
    }
  
    // If step out is active skip everything until the frame where we need to step
    // out to is reached, unless real breakpoint is hit.
    if (StepOutActive() && frame->fp() != step_out_fp() &&
        break_points_hit->IsUndefined() ) {
        // Step count should always be 0 for StepOut.
        ASSERT(thread_local_.step_count_ == 0);
    } else if (!break_points_hit->IsUndefined() ||
               (thread_local_.last_step_action_ != StepNone &&
                thread_local_.step_count_ == 0)) {
      // Notify debugger if a real break point is triggered or if performing
      // single stepping with no more steps to perform. Otherwise do another step.
  
      // Clear all current stepping setup.
      ClearStepping();
  
      if (thread_local_.queued_step_count_ > 0) {
        // Perform queued steps
        int step_count = thread_local_.queued_step_count_;
  
        // Clear queue
        thread_local_.queued_step_count_ = 0;
  
        PrepareStep(StepNext, step_count, StackFrame::NO_ID);
      } else {
        // Notify the debug event listeners.
        isolate_->debugger()->OnDebugBreak(break_points_hit, false);
      }
    } else if (thread_local_.last_step_action_ != StepNone) {
      // Hold on to last step action as it is cleared by the call to
      // ClearStepping.
      StepAction step_action = thread_local_.last_step_action_;
      int step_count = thread_local_.step_count_;
  
      // If StepNext goes deeper in code, StepOut until original frame
      // and keep step count queued up in the meantime.
      if (step_action == StepNext && frame->fp() < thread_local_.last_fp_) {
        // Count frames until target frame
        int count = 0;
        JavaScriptFrameIterator it(isolate_);
        while (!it.done() && it.frame()->fp() < thread_local_.last_fp_) {
          count++;
          it.Advance();
        }
  
        // Check that we indeed found the frame we are looking for.
        CHECK(!it.done() && (it.frame()->fp() == thread_local_.last_fp_));
        if (step_count > 1) {
          // Save old count and action to continue stepping after StepOut.
          thread_local_.queued_step_count_ = step_count - 1;
        }
  
        // Set up for StepOut to reach target frame.
        step_action = StepOut;
        step_count = count;
      }
  
      // Clear all current stepping setup.
      ClearStepping();
  
      // Set up for the remaining steps.
      PrepareStep(step_action, step_count, StackFrame::NO_ID);
    }
  
    if (thread_local_.frame_drop_mode_ == FRAMES_UNTOUCHED) {
      SetAfterBreakTarget(frame);
    } else if (thread_local_.frame_drop_mode_ ==
        FRAME_DROPPED_IN_IC_CALL) {
      // We must have been calling IC stub. Do not go there anymore.
      Code* plain_return = isolate_->builtins()->builtin(
          Builtins::kPlainReturn_LiveEdit);
      thread_local_.after_break_target_ = plain_return->entry();
    } else if (thread_local_.frame_drop_mode_ ==
        FRAME_DROPPED_IN_DEBUG_SLOT_CALL) {
      // Debug break slot stub does not return normally, instead it manually
      // cleans the stack and jumps. We should patch the jump address.
      Code* plain_return = isolate_->builtins()->builtin(
          Builtins::kFrameDropper_LiveEdit);
      thread_local_.after_break_target_ = plain_return->entry();
    } else if (thread_local_.frame_drop_mode_ ==
        FRAME_DROPPED_IN_DIRECT_CALL) {
      // Nothing to do, after_break_target is not used here.
    } else if (thread_local_.frame_drop_mode_ ==
        FRAME_DROPPED_IN_RETURN_CALL) {
      Code* plain_return = isolate_->builtins()->builtin(
          Builtins::kFrameDropper_LiveEdit);
      thread_local_.after_break_target_ = plain_return->entry();
    } else {
      UNREACHABLE();
    }
  
    return heap->undefined_value();
  }
  
  
  RUNTIME_FUNCTION(Object*, Debug_Break) {
    return isolate->debug()->Break(args);
  }
  
  
  // Check the break point objects for whether one or more are actually
  // triggered. This function returns a JSArray with the break point objects
  // which is triggered.
  Handle<Object> Debug::CheckBreakPoints(Handle<Object> break_point_objects) {
    Factory* factory = isolate_->factory();
  
    // Count the number of break points hit. If there are multiple break points
    // they are in a FixedArray.
    Handle<FixedArray> break_points_hit;
    int break_points_hit_count = 0;
    ASSERT(!break_point_objects->IsUndefined());
    if (break_point_objects->IsFixedArray()) {
      Handle<FixedArray> array(FixedArray::cast(*break_point_objects));
      break_points_hit = factory->NewFixedArray(array->length());
      for (int i = 0; i < array->length(); i++) {
        Handle<Object> o(array->get(i), isolate_);
        if (CheckBreakPoint(o)) {
          break_points_hit->set(break_points_hit_count++, *o);
        }
      }
    } else {
      break_points_hit = factory->NewFixedArray(1);
      if (CheckBreakPoint(break_point_objects)) {
        break_points_hit->set(break_points_hit_count++, *break_point_objects);
      }
    }
  
    // Return undefined if no break points were triggered.
    if (break_points_hit_count == 0) {
      return factory->undefined_value();
    }
    // Return break points hit as a JSArray.
    Handle<JSArray> result = factory->NewJSArrayWithElements(break_points_hit);
    result->set_length(Smi::FromInt(break_points_hit_count));
    return result;
  }
  
  
  // Check whether a single break point object is triggered.
  bool Debug::CheckBreakPoint(Handle<Object> break_point_object) {
    Factory* factory = isolate_->factory();
    HandleScope scope(isolate_);
  
    // Ignore check if break point object is not a JSObject.
    if (!break_point_object->IsJSObject()) return true;
  
    // Get the function IsBreakPointTriggered (defined in debug-debugger.js).
    Handle<String> is_break_point_triggered_string =
        factory->InternalizeOneByteString(
            STATIC_ASCII_VECTOR("IsBreakPointTriggered"));
    Handle<JSFunction> check_break_point =
      Handle<JSFunction>(JSFunction::cast(
          debug_context()->global_object()->GetPropertyNoExceptionThrown(
              *is_break_point_triggered_string)));
  
    // Get the break id as an object.
    Handle<Object> break_id = factory->NewNumberFromInt(Debug::break_id());
  
    // Call HandleBreakPointx.
    bool caught_exception;
    Handle<Object> argv[] = { break_id, break_point_object };
    Handle<Object> result = Execution::TryCall(check_break_point,
                                               isolate_->js_builtins_object(),
                                               ARRAY_SIZE(argv),
                                               argv,
                                               &caught_exception);
  
    // If exception or non boolean result handle as not triggered
    if (caught_exception || !result->IsBoolean()) {
      return false;
    }
  
    // Return whether the break point is triggered.
    ASSERT(!result.is_null());
    return (*result)->IsTrue();
  }
  
  
  // Check whether the function has debug information.
  bool Debug::HasDebugInfo(Handle<SharedFunctionInfo> shared) {
    return !shared->debug_info()->IsUndefined();
  }
  
  
  // Return the debug info for this function. EnsureDebugInfo must be called
  // prior to ensure the debug info has been generated for shared.
  Handle<DebugInfo> Debug::GetDebugInfo(Handle<SharedFunctionInfo> shared) {
    ASSERT(HasDebugInfo(shared));
    return Handle<DebugInfo>(DebugInfo::cast(shared->debug_info()));
  }
  
  
  void Debug::SetBreakPoint(Handle<JSFunction> function,
                            Handle<Object> break_point_object,
                            int* source_position) {
    HandleScope scope(isolate_);
  
    PrepareForBreakPoints();
  
    // Make sure the function is compiled and has set up the debug info.
    Handle<SharedFunctionInfo> shared(function->shared());
    if (!EnsureDebugInfo(shared, function)) {
      // Return if retrieving debug info failed.
      return;
    }
  
    Handle<DebugInfo> debug_info = GetDebugInfo(shared);
    // Source positions starts with zero.
    ASSERT(*source_position >= 0);
  
    // Find the break point and change it.
    BreakLocationIterator it(debug_info, SOURCE_BREAK_LOCATIONS);
    it.FindBreakLocationFromPosition(*source_position, STATEMENT_ALIGNED);
    it.SetBreakPoint(break_point_object);
  
    *source_position = it.position();
  
    // At least one active break point now.
    ASSERT(debug_info->GetBreakPointCount() > 0);
  }
  
  
  bool Debug::SetBreakPointForScript(Handle<Script> script,
                                     Handle<Object> break_point_object,
                                     int* source_position,
                                     BreakPositionAlignment alignment) {
    HandleScope scope(isolate_);
  
    PrepareForBreakPoints();
  
    // Obtain shared function info for the function.
    Object* result = FindSharedFunctionInfoInScript(script, *source_position);
    if (result->IsUndefined()) return false;
  
    // Make sure the function has set up the debug info.
    Handle<SharedFunctionInfo> shared(SharedFunctionInfo::cast(result));
    if (!EnsureDebugInfo(shared, Handle<JSFunction>::null())) {
      // Return if retrieving debug info failed.
      return false;
    }
  
    // Find position within function. The script position might be before the
    // source position of the first function.
    int position;
    if (shared->start_position() > *source_position) {
      position = 0;
    } else {
      position = *source_position - shared->start_position();
    }
  
    Handle<DebugInfo> debug_info = GetDebugInfo(shared);
    // Source positions starts with zero.
    ASSERT(position >= 0);
  
    // Find the break point and change it.
    BreakLocationIterator it(debug_info, SOURCE_BREAK_LOCATIONS);
    it.FindBreakLocationFromPosition(position, alignment);
    it.SetBreakPoint(break_point_object);
  
    *source_position = it.position() + shared->start_position();
  
    // At least one active break point now.
    ASSERT(debug_info->GetBreakPointCount() > 0);
    return true;
  }
  
  
  void Debug::ClearBreakPoint(Handle<Object> break_point_object) {
    HandleScope scope(isolate_);
  
    DebugInfoListNode* node = debug_info_list_;
    while (node != NULL) {
      Object* result = DebugInfo::FindBreakPointInfo(node->debug_info(),
                                                     break_point_object);
      if (!result->IsUndefined()) {
        // Get information in the break point.
        BreakPointInfo* break_point_info = BreakPointInfo::cast(result);
        Handle<DebugInfo> debug_info = node->debug_info();
  
        // Find the break point and clear it.
        BreakLocationIterator it(debug_info, SOURCE_BREAK_LOCATIONS);
        it.FindBreakLocationFromAddress(debug_info->code()->entry() +
            break_point_info->code_position()->value());
        it.ClearBreakPoint(break_point_object);
  
        // If there are no more break points left remove the debug info for this
        // function.
        if (debug_info->GetBreakPointCount() == 0) {
          RemoveDebugInfo(debug_info);
        }
  
        return;
      }
      node = node->next();
    }
  }
  
  
  void Debug::ClearAllBreakPoints() {
    DebugInfoListNode* node = debug_info_list_;
    while (node != NULL) {
      // Remove all debug break code.
      BreakLocationIterator it(node->debug_info(), ALL_BREAK_LOCATIONS);
      it.ClearAllDebugBreak();
      node = node->next();
    }
  
    // Remove all debug info.
    while (debug_info_list_ != NULL) {
      RemoveDebugInfo(debug_info_list_->debug_info());
    }
  }
  
  
  void Debug::FloodWithOneShot(Handle<JSFunction> function) {
    PrepareForBreakPoints();
  
    // Make sure the function is compiled and has set up the debug info.
    Handle<SharedFunctionInfo> shared(function->shared());
    if (!EnsureDebugInfo(shared, function)) {
      // Return if we failed to retrieve the debug info.
      return;
    }
  
    // Flood the function with break points.
    BreakLocationIterator it(GetDebugInfo(shared), ALL_BREAK_LOCATIONS);
    while (!it.Done()) {
      it.SetOneShot();
      it.Next();
    }
  }
  
  
  void Debug::FloodBoundFunctionWithOneShot(Handle<JSFunction> function) {
    Handle<FixedArray> new_bindings(function->function_bindings());
    Handle<Object> bindee(new_bindings->get(JSFunction::kBoundFunctionIndex),
                          isolate_);
  
    if (!bindee.is_null() && bindee->IsJSFunction() &&
        !JSFunction::cast(*bindee)->IsBuiltin()) {
      Handle<JSFunction> bindee_function(JSFunction::cast(*bindee));
      Debug::FloodWithOneShot(bindee_function);
    }
  }
  
  
  void Debug::FloodHandlerWithOneShot() {
    // Iterate through the JavaScript stack looking for handlers.
    StackFrame::Id id = break_frame_id();
    if (id == StackFrame::NO_ID) {
      // If there is no JavaScript stack don't do anything.
      return;
    }
    for (JavaScriptFrameIterator it(isolate_, id); !it.done(); it.Advance()) {
      JavaScriptFrame* frame = it.frame();
      if (frame->HasHandler()) {
        // Flood the function with the catch block with break points
        FloodWithOneShot(Handle<JSFunction>(frame->function()));
        return;
      }
    }
  }
  
  
  void Debug::ChangeBreakOnException(ExceptionBreakType type, bool enable) {
    if (type == BreakUncaughtException) {
      break_on_uncaught_exception_ = enable;
    } else {
      break_on_exception_ = enable;
    }
  }
  
  
  bool Debug::IsBreakOnException(ExceptionBreakType type) {
    if (type == BreakUncaughtException) {
      return break_on_uncaught_exception_;
    } else {
      return break_on_exception_;
    }
  }
  
  
  void Debug::PrepareStep(StepAction step_action,
                          int step_count,
                          StackFrame::Id frame_id) {
    HandleScope scope(isolate_);
  
    PrepareForBreakPoints();
  
    ASSERT(Debug::InDebugger());
  
    // Remember this step action and count.
    thread_local_.last_step_action_ = step_action;
    if (step_action == StepOut) {
      // For step out target frame will be found on the stack so there is no need
      // to set step counter for it. It's expected to always be 0 for StepOut.
      thread_local_.step_count_ = 0;
    } else {
      thread_local_.step_count_ = step_count;
    }
  
    // Get the frame where the execution has stopped and skip the debug frame if
    // any. The debug frame will only be present if execution was stopped due to
    // hitting a break point. In other situations (e.g. unhandled exception) the
    // debug frame is not present.
    StackFrame::Id id = break_frame_id();
    if (id == StackFrame::NO_ID) {
      // If there is no JavaScript stack don't do anything.
      return;
    }
    if (frame_id != StackFrame::NO_ID) {
      id = frame_id;
    }
    JavaScriptFrameIterator frames_it(isolate_, id);
    JavaScriptFrame* frame = frames_it.frame();
  
    // First of all ensure there is one-shot break points in the top handler
    // if any.
    FloodHandlerWithOneShot();
  
    // If the function on the top frame is unresolved perform step out. This will
    // be the case when calling unknown functions and having the debugger stopped
    // in an unhandled exception.
    if (!frame->function()->IsJSFunction()) {
      // Step out: Find the calling JavaScript frame and flood it with
      // breakpoints.
      frames_it.Advance();
      // Fill the function to return to with one-shot break points.
      JSFunction* function = frames_it.frame()->function();
      FloodWithOneShot(Handle<JSFunction>(function));
      return;
    }
  
    // Get the debug info (create it if it does not exist).
    Handle<JSFunction> function(frame->function());
    Handle<SharedFunctionInfo> shared(function->shared());
    if (!EnsureDebugInfo(shared, function)) {
      // Return if ensuring debug info failed.
      return;
    }
    Handle<DebugInfo> debug_info = GetDebugInfo(shared);
  
    // Find the break location where execution has stopped.
    BreakLocationIterator it(debug_info, ALL_BREAK_LOCATIONS);
    // pc points to the instruction after the current one, possibly a break
    // location as well. So the "- 1" to exclude it from the search.
    it.FindBreakLocationFromAddress(frame->pc() - 1);
  
    // Compute whether or not the target is a call target.
    bool is_load_or_store = false;
    bool is_inline_cache_stub = false;
    bool is_at_restarted_function = false;
    Handle<Code> call_function_stub;
  
    if (thread_local_.restarter_frame_function_pointer_ == NULL) {
      if (RelocInfo::IsCodeTarget(it.rinfo()->rmode())) {
        bool is_call_target = false;
        Address target = it.rinfo()->target_address();
        Code* code = Code::GetCodeFromTargetAddress(target);
        if (code->is_inline_cache_stub()) {
          is_inline_cache_stub = true;
          is_load_or_store = !is_call_target;
        }
  
        // Check if target code is CallFunction stub.
        Code* maybe_call_function_stub = code;
        // If there is a breakpoint at this line look at the original code to
        // check if it is a CallFunction stub.
        if (it.IsDebugBreak()) {
          Address original_target = it.original_rinfo()->target_address();
          maybe_call_function_stub =
              Code::GetCodeFromTargetAddress(original_target);
        }
        if (maybe_call_function_stub->kind() == Code::STUB &&
            maybe_call_function_stub->major_key() == CodeStub::CallFunction) {
          // Save reference to the code as we may need it to find out arguments
          // count for 'step in' later.
          call_function_stub = Handle<Code>(maybe_call_function_stub);
        }
      }
    } else {
      is_at_restarted_function = true;
    }
  
    // If this is the last break code target step out is the only possibility.
    if (it.IsExit() || step_action == StepOut) {
      if (step_action == StepOut) {
        // Skip step_count frames starting with the current one.
        while (step_count-- > 0 && !frames_it.done()) {
          frames_it.Advance();
        }
      } else {
        ASSERT(it.IsExit());
        frames_it.Advance();
      }
      // Skip builtin functions on the stack.
      while (!frames_it.done() && frames_it.frame()->function()->IsBuiltin()) {
        frames_it.Advance();
      }
      // Step out: If there is a JavaScript caller frame, we need to
      // flood it with breakpoints.
      if (!frames_it.done()) {
        // Fill the function to return to with one-shot break points.
        JSFunction* function = frames_it.frame()->function();
        FloodWithOneShot(Handle<JSFunction>(function));
        // Set target frame pointer.
        ActivateStepOut(frames_it.frame());
      }
    } else if (!(is_inline_cache_stub || RelocInfo::IsConstructCall(it.rmode()) ||
                 !call_function_stub.is_null() || is_at_restarted_function)
               || step_action == StepNext || step_action == StepMin) {
      // Step next or step min.
  
      // Fill the current function with one-shot break points.
      FloodWithOneShot(function);
  
      // Remember source position and frame to handle step next.
      thread_local_.last_statement_position_ =
          debug_info->code()->SourceStatementPosition(frame->pc());
      thread_local_.last_fp_ = frame->UnpaddedFP();
    } else {
      // If there's restarter frame on top of the stack, just get the pointer
      // to function which is going to be restarted.
      if (is_at_restarted_function) {
        Handle<JSFunction> restarted_function(
            JSFunction::cast(*thread_local_.restarter_frame_function_pointer_));
        FloodWithOneShot(restarted_function);
      } else if (!call_function_stub.is_null()) {
        // If it's CallFunction stub ensure target function is compiled and flood
        // it with one shot breakpoints.
  
        // Find out number of arguments from the stub minor key.
        // Reverse lookup required as the minor key cannot be retrieved
        // from the code object.
        Handle<Object> obj(
            isolate_->heap()->code_stubs()->SlowReverseLookup(
                *call_function_stub),
            isolate_);
        ASSERT(!obj.is_null());
        ASSERT(!(*obj)->IsUndefined());
        ASSERT(obj->IsSmi());
        // Get the STUB key and extract major and minor key.
        uint32_t key = Smi::cast(*obj)->value();
        // Argc in the stub is the number of arguments passed - not the
        // expected arguments of the called function.
        int call_function_arg_count =
            CallFunctionStub::ExtractArgcFromMinorKey(
                CodeStub::MinorKeyFromKey(key));
        ASSERT(call_function_stub->major_key() ==
               CodeStub::MajorKeyFromKey(key));
  
        // Find target function on the expression stack.
        // Expression stack looks like this (top to bottom):
        // argN
        // ...
        // arg0
        // Receiver
        // Function to call
        int expressions_count = frame->ComputeExpressionsCount();
        ASSERT(expressions_count - 2 - call_function_arg_count >= 0);
        Object* fun = frame->GetExpression(
            expressions_count - 2 - call_function_arg_count);
  
        // Flood the actual target of call/apply.
        if (fun->IsJSFunction()) {
          Isolate* isolate = JSFunction::cast(fun)->GetIsolate();
          Code* apply = isolate->builtins()->builtin(Builtins::kFunctionApply);
          Code* call = isolate->builtins()->builtin(Builtins::kFunctionCall);
          while (fun->IsJSFunction()) {
            Code* code = JSFunction::cast(fun)->shared()->code();
            if (code != apply && code != call) break;
            fun = frame->GetExpression(
                expressions_count - 1 - call_function_arg_count);
          }
        }
  
        if (fun->IsJSFunction()) {
          Handle<JSFunction> js_function(JSFunction::cast(fun));
          if (js_function->shared()->bound()) {
            Debug::FloodBoundFunctionWithOneShot(js_function);
          } else if (!js_function->IsBuiltin()) {
            // Don't step into builtins.
            // It will also compile target function if it's not compiled yet.
            FloodWithOneShot(js_function);
          }
        }
      }
  
      // Fill the current function with one-shot break points even for step in on
      // a call target as the function called might be a native function for
      // which step in will not stop. It also prepares for stepping in
      // getters/setters.
      FloodWithOneShot(function);
  
      if (is_load_or_store) {
        // Remember source position and frame to handle step in getter/setter. If
        // there is a custom getter/setter it will be handled in
        // Object::Get/SetPropertyWithCallback, otherwise the step action will be
        // propagated on the next Debug::Break.
        thread_local_.last_statement_position_ =
            debug_info->code()->SourceStatementPosition(frame->pc());
        thread_local_.last_fp_ = frame->UnpaddedFP();
      }
  
      // Step in or Step in min
      it.PrepareStepIn(isolate_);
      ActivateStepIn(frame);
    }
  }
  
  
  // Check whether the current debug break should be reported to the debugger. It
  // is used to have step next and step in only report break back to the debugger
  // if on a different frame or in a different statement. In some situations
  // there will be several break points in the same statement when the code is
  // flooded with one-shot break points. This function helps to perform several
  // steps before reporting break back to the debugger.
  bool Debug::StepNextContinue(BreakLocationIterator* break_location_iterator,
                               JavaScriptFrame* frame) {
    // StepNext and StepOut shouldn't bring us deeper in code, so last frame
    // shouldn't be a parent of current frame.
    if (thread_local_.last_step_action_ == StepNext ||
        thread_local_.last_step_action_ == StepOut) {
      if (frame->fp() < thread_local_.last_fp_) return true;
    }
  
    // If the step last action was step next or step in make sure that a new
    // statement is hit.
    if (thread_local_.last_step_action_ == StepNext ||
        thread_local_.last_step_action_ == StepIn) {
      // Never continue if returning from function.
      if (break_location_iterator->IsExit()) return false;
  
      // Continue if we are still on the same frame and in the same statement.
      int current_statement_position =
          break_location_iterator->code()->SourceStatementPosition(frame->pc());
      return thread_local_.last_fp_ == frame->UnpaddedFP() &&
          thread_local_.last_statement_position_ == current_statement_position;
    }
  
    // No step next action - don't continue.
    return false;
  }
  
  
  // Check whether the code object at the specified address is a debug break code
  // object.
  bool Debug::IsDebugBreak(Address addr) {
    Code* code = Code::GetCodeFromTargetAddress(addr);
    return code->is_debug_stub() && code->extra_ic_state() == DEBUG_BREAK;
  }
  
  
  // Check whether a code stub with the specified major key is a possible break
  // point location when looking for source break locations.
  bool Debug::IsSourceBreakStub(Code* code) {
    CodeStub::Major major_key = CodeStub::GetMajorKey(code);
    return major_key == CodeStub::CallFunction;
  }
  
  
  // Check whether a code stub with the specified major key is a possible break
  // location.
  bool Debug::IsBreakStub(Code* code) {
    CodeStub::Major major_key = CodeStub::GetMajorKey(code);
    return major_key == CodeStub::CallFunction;
  }
  
  
  // Find the builtin to use for invoking the debug break
  Handle<Code> Debug::FindDebugBreak(Handle<Code> code, RelocInfo::Mode mode) {
    Isolate* isolate = code->GetIsolate();
  
    // Find the builtin debug break function matching the calling convention
    // used by the call site.
    if (code->is_inline_cache_stub()) {
      switch (code->kind()) {
        case Code::LOAD_IC:
          return isolate->builtins()->LoadIC_DebugBreak();
  
        case Code::STORE_IC:
          return isolate->builtins()->StoreIC_DebugBreak();
  
        case Code::KEYED_LOAD_IC:
          return isolate->builtins()->KeyedLoadIC_DebugBreak();
  
        case Code::KEYED_STORE_IC:
          return isolate->builtins()->KeyedStoreIC_DebugBreak();
  
        case Code::COMPARE_NIL_IC:
          return isolate->builtins()->CompareNilIC_DebugBreak();
  
        default:
          UNREACHABLE();
      }
    }
    if (RelocInfo::IsConstructCall(mode)) {
      if (code->has_function_cache()) {
        return isolate->builtins()->CallConstructStub_Recording_DebugBreak();
      } else {
        return isolate->builtins()->CallConstructStub_DebugBreak();
      }
    }
    if (code->kind() == Code::STUB) {
      ASSERT(code->major_key() == CodeStub::CallFunction);
      if (code->has_function_cache()) {
        return isolate->builtins()->CallFunctionStub_Recording_DebugBreak();
      } else {
        return isolate->builtins()->CallFunctionStub_DebugBreak();
      }
    }
  
    UNREACHABLE();
    return Handle<Code>::null();
  }
  
  
  // Simple function for returning the source positions for active break points.
  Handle<Object> Debug::GetSourceBreakLocations(
      Handle<SharedFunctionInfo> shared,
      BreakPositionAlignment position_alignment) {
    Isolate* isolate = shared->GetIsolate();
    Heap* heap = isolate->heap();
    if (!HasDebugInfo(shared)) {
      return Handle<Object>(heap->undefined_value(), isolate);
    }
    Handle<DebugInfo> debug_info = GetDebugInfo(shared);
    if (debug_info->GetBreakPointCount() == 0) {
      return Handle<Object>(heap->undefined_value(), isolate);
    }
    Handle<FixedArray> locations =
        isolate->factory()->NewFixedArray(debug_info->GetBreakPointCount());
    int count = 0;
    for (int i = 0; i < debug_info->break_points()->length(); i++) {
      if (!debug_info->break_points()->get(i)->IsUndefined()) {
        BreakPointInfo* break_point_info =
            BreakPointInfo::cast(debug_info->break_points()->get(i));
        if (break_point_info->GetBreakPointCount() > 0) {
          Smi* position;
          switch (position_alignment) {
          case STATEMENT_ALIGNED:
            position = break_point_info->statement_position();
            break;
          case BREAK_POSITION_ALIGNED:
            position = break_point_info->source_position();
            break;
          default:
            UNREACHABLE();
            position = break_point_info->statement_position();
          }
  
          locations->set(count++, position);
        }
      }
    }
    return locations;
  }
  
  
  void Debug::NewBreak(StackFrame::Id break_frame_id) {
    thread_local_.break_frame_id_ = break_frame_id;
    thread_local_.break_id_ = ++thread_local_.break_count_;
  }
  
  
  void Debug::SetBreak(StackFrame::Id break_frame_id, int break_id) {
    thread_local_.break_frame_id_ = break_frame_id;
    thread_local_.break_id_ = break_id;
  }
  
  
  // Handle stepping into a function.
  void Debug::HandleStepIn(Handle<JSFunction> function,
                           Handle<Object> holder,
                           Address fp,
                           bool is_constructor) {
    Isolate* isolate = function->GetIsolate();
    // If the frame pointer is not supplied by the caller find it.
    if (fp == 0) {
      StackFrameIterator it(isolate);
      it.Advance();
      // For constructor functions skip another frame.
      if (is_constructor) {
        ASSERT(it.frame()->is_construct());
        it.Advance();
      }
      fp = it.frame()->fp();
    }
  
    // Flood the function with one-shot break points if it is called from where
    // step into was requested.
    if (fp == step_in_fp()) {
      if (function->shared()->bound()) {
        // Handle Function.prototype.bind
        Debug::FloodBoundFunctionWithOneShot(function);
      } else if (!function->IsBuiltin()) {
        // Don't allow step into functions in the native context.
        if (function->shared()->code() ==
            isolate->builtins()->builtin(Builtins::kFunctionApply) ||
            function->shared()->code() ==
            isolate->builtins()->builtin(Builtins::kFunctionCall)) {
          // Handle function.apply and function.call separately to flood the
          // function to be called and not the code for Builtins::FunctionApply or
          // Builtins::FunctionCall. The receiver of call/apply is the target
          // function.
          if (!holder.is_null() && holder->IsJSFunction()) {
            Handle<JSFunction> js_function = Handle<JSFunction>::cast(holder);
            if (!js_function->IsBuiltin()) {
              Debug::FloodWithOneShot(js_function);
            } else if (js_function->shared()->bound()) {
              // Handle Function.prototype.bind
              Debug::FloodBoundFunctionWithOneShot(js_function);
            }
          }
        } else {
          Debug::FloodWithOneShot(function);
        }
      }
    }
  }
  
  
  void Debug::ClearStepping() {
    // Clear the various stepping setup.
    ClearOneShot();
    ClearStepIn();
    ClearStepOut();
    ClearStepNext();
  
    // Clear multiple step counter.
    thread_local_.step_count_ = 0;
  }
  
  
  // Clears all the one-shot break points that are currently set. Normally this
  // function is called each time a break point is hit as one shot break points
  // are used to support stepping.
  void Debug::ClearOneShot() {
    // The current implementation just runs through all the breakpoints. When the
    // last break point for a function is removed that function is automatically
    // removed from the list.
  
    DebugInfoListNode* node = debug_info_list_;
    while (node != NULL) {
      BreakLocationIterator it(node->debug_info(), ALL_BREAK_LOCATIONS);
      while (!it.Done()) {
        it.ClearOneShot();
        it.Next();
      }
      node = node->next();
    }
  }
  
  
  void Debug::ActivateStepIn(StackFrame* frame) {
    ASSERT(!StepOutActive());
    thread_local_.step_into_fp_ = frame->UnpaddedFP();
  }
  
  
  void Debug::ClearStepIn() {
    thread_local_.step_into_fp_ = 0;
  }
  
  
  void Debug::ActivateStepOut(StackFrame* frame) {
    ASSERT(!StepInActive());
    thread_local_.step_out_fp_ = frame->UnpaddedFP();
  }
  
  
  void Debug::ClearStepOut() {
    thread_local_.step_out_fp_ = 0;
  }
  
  
  void Debug::ClearStepNext() {
    thread_local_.last_step_action_ = StepNone;
    thread_local_.last_statement_position_ = RelocInfo::kNoPosition;
    thread_local_.last_fp_ = 0;
  }
  
  
  static void CollectActiveFunctionsFromThread(
      Isolate* isolate,
      ThreadLocalTop* top,
      List<Handle<JSFunction> >* active_functions,
      Object* active_code_marker) {
    // Find all non-optimized code functions with activation frames
    // on the stack. This includes functions which have optimized
    // activations (including inlined functions) on the stack as the
    // non-optimized code is needed for the lazy deoptimization.
    for (JavaScriptFrameIterator it(isolate, top); !it.done(); it.Advance()) {
      JavaScriptFrame* frame = it.frame();
      if (frame->is_optimized()) {
        List<JSFunction*> functions(FLAG_max_inlining_levels + 1);
        frame->GetFunctions(&functions);
        for (int i = 0; i < functions.length(); i++) {
          JSFunction* function = functions[i];
          active_functions->Add(Handle<JSFunction>(function));
          function->shared()->code()->set_gc_metadata(active_code_marker);
        }
      } else if (frame->function()->IsJSFunction()) {
        JSFunction* function = frame->function();
        ASSERT(frame->LookupCode()->kind() == Code::FUNCTION);
        active_functions->Add(Handle<JSFunction>(function));
        function->shared()->code()->set_gc_metadata(active_code_marker);
      }
    }
  }
  
  
  static void RedirectActivationsToRecompiledCodeOnThread(
      Isolate* isolate,
      ThreadLocalTop* top) {
    for (JavaScriptFrameIterator it(isolate, top); !it.done(); it.Advance()) {
      JavaScriptFrame* frame = it.frame();
  
      if (frame->is_optimized() || !frame->function()->IsJSFunction()) continue;
  
      JSFunction* function = frame->function();
  
      ASSERT(frame->LookupCode()->kind() == Code::FUNCTION);
  
      Handle<Code> frame_code(frame->LookupCode());
      if (frame_code->has_debug_break_slots()) continue;
  
      Handle<Code> new_code(function->shared()->code());
      if (new_code->kind() != Code::FUNCTION ||
          !new_code->has_debug_break_slots()) {
        continue;
      }
  
      // Iterate over the RelocInfo in the original code to compute the sum of the
      // constant pools sizes. (See Assembler::CheckConstPool())
      // Note that this is only useful for architectures using constant pools.
      int constpool_mask = RelocInfo::ModeMask(RelocInfo::CONST_POOL);
      int frame_const_pool_size = 0;
      for (RelocIterator it(*frame_code, constpool_mask); !it.done(); it.next()) {
        RelocInfo* info = it.rinfo();
        if (info->pc() >= frame->pc()) break;
        frame_const_pool_size += static_cast<int>(info->data());
      }
      intptr_t frame_offset =
        frame->pc() - frame_code->instruction_start() - frame_const_pool_size;
  
      // Iterate over the RelocInfo for new code to find the number of bytes
      // generated for debug slots and constant pools.
      int debug_break_slot_bytes = 0;
      int new_code_const_pool_size = 0;
      int mask = RelocInfo::ModeMask(RelocInfo::DEBUG_BREAK_SLOT) |
                 RelocInfo::ModeMask(RelocInfo::CONST_POOL);
      for (RelocIterator it(*new_code, mask); !it.done(); it.next()) {
        // Check if the pc in the new code with debug break
        // slots is before this slot.
        RelocInfo* info = it.rinfo();
        intptr_t new_offset = info->pc() - new_code->instruction_start() -
                              new_code_const_pool_size - debug_break_slot_bytes;
        if (new_offset >= frame_offset) {
          break;
        }
  
        if (RelocInfo::IsDebugBreakSlot(info->rmode())) {
          debug_break_slot_bytes += Assembler::kDebugBreakSlotLength;
        } else {
          ASSERT(RelocInfo::IsConstPool(info->rmode()));
          // The size of the constant pool is encoded in the data.
          new_code_const_pool_size += static_cast<int>(info->data());
        }
      }
  
      // Compute the equivalent pc in the new code.
      byte* new_pc = new_code->instruction_start() + frame_offset +
                     debug_break_slot_bytes + new_code_const_pool_size;
  
      if (FLAG_trace_deopt) {
        PrintF("Replacing code %08" V8PRIxPTR " - %08" V8PRIxPTR " (%d) "
               "with %08" V8PRIxPTR " - %08" V8PRIxPTR " (%d) "
               "for debugging, "
               "changing pc from %08" V8PRIxPTR " to %08" V8PRIxPTR "\n",
               reinterpret_cast<intptr_t>(
                   frame_code->instruction_start()),
               reinterpret_cast<intptr_t>(
                   frame_code->instruction_start()) +
               frame_code->instruction_size(),
               frame_code->instruction_size(),
               reinterpret_cast<intptr_t>(new_code->instruction_start()),
               reinterpret_cast<intptr_t>(new_code->instruction_start()) +
               new_code->instruction_size(),
               new_code->instruction_size(),
               reinterpret_cast<intptr_t>(frame->pc()),
               reinterpret_cast<intptr_t>(new_pc));
      }
  
      // Patch the return address to return into the code with
      // debug break slots.
      frame->set_pc(new_pc);
    }
  }
  
  
  class ActiveFunctionsCollector : public ThreadVisitor {
   public:
    explicit ActiveFunctionsCollector(List<Handle<JSFunction> >* active_functions,
                                      Object* active_code_marker)
        : active_functions_(active_functions),
          active_code_marker_(active_code_marker) { }
  
    void VisitThread(Isolate* isolate, ThreadLocalTop* top) {
      CollectActiveFunctionsFromThread(isolate,
                                       top,
                                       active_functions_,
                                       active_code_marker_);
    }
  
   private:
    List<Handle<JSFunction> >* active_functions_;
    Object* active_code_marker_;
  };
  
  
  class ActiveFunctionsRedirector : public ThreadVisitor {
   public:
    void VisitThread(Isolate* isolate, ThreadLocalTop* top) {
      RedirectActivationsToRecompiledCodeOnThread(isolate, top);
    }
  };
  
  
  void Debug::PrepareForBreakPoints() {
    // If preparing for the first break point make sure to deoptimize all
    // functions as debugging does not work with optimized code.
    if (!has_break_points_) {
      if (isolate_->concurrent_recompilation_enabled()) {
        isolate_->optimizing_compiler_thread()->Flush();
      }
  
      Deoptimizer::DeoptimizeAll(isolate_);
  
      Handle<Code> lazy_compile = isolate_->builtins()->CompileUnoptimized();
  
      // There will be at least one break point when we are done.
      has_break_points_ = true;
  
      // Keep the list of activated functions in a handlified list as it
      // is used both in GC and non-GC code.
      List<Handle<JSFunction> > active_functions(100);
  
      {
        // We are going to iterate heap to find all functions without
        // debug break slots.
        Heap* heap = isolate_->heap();
        heap->CollectAllGarbage(Heap::kMakeHeapIterableMask,
                                "preparing for breakpoints");
  
        // Ensure no GC in this scope as we are going to use gc_metadata
        // field in the Code object to mark active functions.
        DisallowHeapAllocation no_allocation;
  
        Object* active_code_marker = heap->the_hole_value();
  
        CollectActiveFunctionsFromThread(isolate_,
                                         isolate_->thread_local_top(),
                                         &active_functions,
                                         active_code_marker);
        ActiveFunctionsCollector active_functions_collector(&active_functions,
                                                            active_code_marker);
        isolate_->thread_manager()->IterateArchivedThreads(
            &active_functions_collector);
  
        // Scan the heap for all non-optimized functions which have no
        // debug break slots and are not active or inlined into an active
        // function and mark them for lazy compilation.
        HeapIterator iterator(heap);
        HeapObject* obj = NULL;
        while (((obj = iterator.next()) != NULL)) {
          if (obj->IsJSFunction()) {
            JSFunction* function = JSFunction::cast(obj);
            SharedFunctionInfo* shared = function->shared();
  
            if (!shared->allows_lazy_compilation()) continue;
            if (!shared->script()->IsScript()) continue;
            if (function->IsBuiltin()) continue;
            if (shared->code()->gc_metadata() == active_code_marker) continue;
  
            Code::Kind kind = function->code()->kind();
            if (kind == Code::FUNCTION &&
                !function->code()->has_debug_break_slots()) {
              function->set_code(*lazy_compile);
              function->shared()->set_code(*lazy_compile);
            } else if (kind == Code::BUILTIN &&
                (function->IsInOptimizationQueue() ||
                 function->IsMarkedForOptimization() ||
                 function->IsMarkedForConcurrentOptimization())) {
              // Abort in-flight compilation.
              Code* shared_code = function->shared()->code();
              if (shared_code->kind() == Code::FUNCTION &&
                  shared_code->has_debug_break_slots()) {
                function->set_code(shared_code);
              } else {
                function->set_code(*lazy_compile);
                function->shared()->set_code(*lazy_compile);
              }
            }
          }
        }
  
        // Clear gc_metadata field.
        for (int i = 0; i < active_functions.length(); i++) {
          Handle<JSFunction> function = active_functions[i];
          function->shared()->code()->set_gc_metadata(Smi::FromInt(0));
        }
      }
  
      // Now recompile all functions with activation frames and and
      // patch the return address to run in the new compiled code.
      for (int i = 0; i < active_functions.length(); i++) {
        Handle<JSFunction> function = active_functions[i];
        Handle<SharedFunctionInfo> shared(function->shared());
  
        if (function->code()->kind() == Code::FUNCTION &&
            function->code()->has_debug_break_slots()) {
          // Nothing to do. Function code already had debug break slots.
          continue;
        }
  
        // If recompilation is not possible just skip it.
        if (shared->is_toplevel() ||
            !shared->allows_lazy_compilation() ||
            shared->code()->kind() == Code::BUILTIN) {
          continue;
        }
  
        // Make sure that the shared full code is compiled with debug
        // break slots.
        if (!shared->code()->has_debug_break_slots()) {
          // Try to compile the full code with debug break slots. If it
          // fails just keep the current code.
          bool prev_force_debugger_active =
              isolate_->debugger()->force_debugger_active();
          isolate_->debugger()->set_force_debugger_active(true);
          Handle<Code> code = Compiler::GetCodeForDebugging(function);
          function->ReplaceCode(*code);
          isolate_->debugger()->set_force_debugger_active(
              prev_force_debugger_active);
        }
  
        // Keep function code in sync with shared function info.
        function->set_code(shared->code());
      }
  
      RedirectActivationsToRecompiledCodeOnThread(isolate_,
                                                  isolate_->thread_local_top());
  
      ActiveFunctionsRedirector active_functions_redirector;
      isolate_->thread_manager()->IterateArchivedThreads(
            &active_functions_redirector);
    }
  }
  
  
  Object* Debug::FindSharedFunctionInfoInScript(Handle<Script> script,
                                                int position) {
    // Iterate the heap looking for SharedFunctionInfo generated from the
    // script. The inner most SharedFunctionInfo containing the source position
    // for the requested break point is found.
    // NOTE: This might require several heap iterations. If the SharedFunctionInfo
    // which is found is not compiled it is compiled and the heap is iterated
    // again as the compilation might create inner functions from the newly
    // compiled function and the actual requested break point might be in one of
    // these functions.
    // NOTE: The below fix-point iteration depends on all functions that cannot be
    // compiled lazily without a context to not be compiled at all. Compilation
    // will be triggered at points where we do not need a context.
    bool done = false;
    // The current candidate for the source position:
    int target_start_position = RelocInfo::kNoPosition;
    Handle<JSFunction> target_function;
    Handle<SharedFunctionInfo> target;
    Heap* heap = isolate_->heap();
    while (!done) {
      { // Extra scope for iterator and no-allocation.
        heap->EnsureHeapIsIterable();
        DisallowHeapAllocation no_alloc_during_heap_iteration;
        HeapIterator iterator(heap);
        for (HeapObject* obj = iterator.next();
             obj != NULL; obj = iterator.next()) {
          bool found_next_candidate = false;
          Handle<JSFunction> function;
          Handle<SharedFunctionInfo> shared;
          if (obj->IsJSFunction()) {
            function = Handle<JSFunction>(JSFunction::cast(obj));
            shared = Handle<SharedFunctionInfo>(function->shared());
            ASSERT(shared->allows_lazy_compilation() || shared->is_compiled());
            found_next_candidate = true;
          } else if (obj->IsSharedFunctionInfo()) {
            shared = Handle<SharedFunctionInfo>(SharedFunctionInfo::cast(obj));
            // Skip functions that we cannot compile lazily without a context,
            // which is not available here, because there is no closure.
            found_next_candidate = shared->is_compiled() ||
                shared->allows_lazy_compilation_without_context();
          }
          if (!found_next_candidate) continue;
          if (shared->script() == *script) {
            // If the SharedFunctionInfo found has the requested script data and
            // contains the source position it is a candidate.
            int start_position = shared->function_token_position();
            if (start_position == RelocInfo::kNoPosition) {
              start_position = shared->start_position();
            }
            if (start_position <= position &&
                position <= shared->end_position()) {
              // If there is no candidate or this function is within the current
              // candidate this is the new candidate.
              if (target.is_null()) {
                target_start_position = start_position;
                target_function = function;
                target = shared;
              } else {
                if (target_start_position == start_position &&
                    shared->end_position() == target->end_position()) {
                  // If a top-level function contains only one function
                  // declaration the source for the top-level and the function
                  // is the same. In that case prefer the non top-level function.
                  if (!shared->is_toplevel()) {
                    target_start_position = start_position;
                    target_function = function;
                    target = shared;
                  }
                } else if (target_start_position <= start_position &&
                           shared->end_position() <= target->end_position()) {
                  // This containment check includes equality as a function
                  // inside a top-level function can share either start or end
                  // position with the top-level function.
                  target_start_position = start_position;
                  target_function = function;
                  target = shared;
                }
              }
            }
          }
        }  // End for loop.
      }  // End no-allocation scope.
  
      if (target.is_null()) return heap->undefined_value();
  
      // There will be at least one break point when we are done.
      has_break_points_ = true;
  
      // If the candidate found is compiled we are done.
      done = target->is_compiled();
      if (!done) {
        // If the candidate is not compiled, compile it to reveal any inner
        // functions which might contain the requested source position. This
        // will compile all inner functions that cannot be compiled without a
        // context, because Compiler::BuildFunctionInfo checks whether the
        // debugger is active.
        Handle<Code> result = target_function.is_null()
            ? Compiler::GetUnoptimizedCode(target)
            : Compiler::GetUnoptimizedCode(target_function);
        if (result.is_null()) return isolate_->heap()->undefined_value();
      }
    }  // End while loop.
  
    return *target;
  }
  
  
  // Ensures the debug information is present for shared.
  bool Debug::EnsureDebugInfo(Handle<SharedFunctionInfo> shared,
                              Handle<JSFunction> function) {
    Isolate* isolate = shared->GetIsolate();
  
    // Return if we already have the debug info for shared.
    if (HasDebugInfo(shared)) {
      ASSERT(shared->is_compiled());
      return true;
    }
  
    // There will be at least one break point when we are done.
    has_break_points_ = true;
  
    // Ensure function is compiled. Return false if this failed.
    if (!function.is_null() &&
        !Compiler::EnsureCompiled(function, CLEAR_EXCEPTION)) {
      return false;
    }
  
    // Create the debug info object.
    Handle<DebugInfo> debug_info = isolate->factory()->NewDebugInfo(shared);
  
    // Add debug info to the list.
    DebugInfoListNode* node = new DebugInfoListNode(*debug_info);
    node->set_next(debug_info_list_);
    debug_info_list_ = node;
  
    return true;
  }
  
  
  void Debug::RemoveDebugInfo(Handle<DebugInfo> debug_info) {
    ASSERT(debug_info_list_ != NULL);
    // Run through the debug info objects to find this one and remove it.
    DebugInfoListNode* prev = NULL;
    DebugInfoListNode* current = debug_info_list_;
    while (current != NULL) {
      if (*current->debug_info() == *debug_info) {
        // Unlink from list. If prev is NULL we are looking at the first element.
        if (prev == NULL) {
          debug_info_list_ = current->next();
        } else {
          prev->set_next(current->next());
        }
        current->debug_info()->shared()->set_debug_info(
                isolate_->heap()->undefined_value());
        delete current;
  
        // If there are no more debug info objects there are not more break
        // points.
        has_break_points_ = debug_info_list_ != NULL;
  
        return;
      }
      // Move to next in list.
      prev = current;
      current = current->next();
    }
    UNREACHABLE();
  }
  
  
  void Debug::SetAfterBreakTarget(JavaScriptFrame* frame) {
    HandleScope scope(isolate_);
  
    PrepareForBreakPoints();
  
    // Get the executing function in which the debug break occurred.
    Handle<JSFunction> function(JSFunction::cast(frame->function()));
    Handle<SharedFunctionInfo> shared(function->shared());
    if (!EnsureDebugInfo(shared, function)) {
      // Return if we failed to retrieve the debug info.
      return;
    }
    Handle<DebugInfo> debug_info = GetDebugInfo(shared);
    Handle<Code> code(debug_info->code());
    Handle<Code> original_code(debug_info->original_code());
  #ifdef DEBUG
    // Get the code which is actually executing.
    Handle<Code> frame_code(frame->LookupCode());
    ASSERT(frame_code.is_identical_to(code));
  #endif
  
    // Find the call address in the running code. This address holds the call to
    // either a DebugBreakXXX or to the debug break return entry code if the
    // break point is still active after processing the break point.
    Address addr = frame->pc() - Assembler::kPatchDebugBreakSlotReturnOffset;
  
    // Check if the location is at JS exit or debug break slot.
    bool at_js_return = false;
    bool break_at_js_return_active = false;
    bool at_debug_break_slot = false;
    RelocIterator it(debug_info->code());
    while (!it.done() && !at_js_return && !at_debug_break_slot) {
      if (RelocInfo::IsJSReturn(it.rinfo()->rmode())) {
        at_js_return = (it.rinfo()->pc() ==
            addr - Assembler::kPatchReturnSequenceAddressOffset);
        break_at_js_return_active = it.rinfo()->IsPatchedReturnSequence();
      }
      if (RelocInfo::IsDebugBreakSlot(it.rinfo()->rmode())) {
        at_debug_break_slot = (it.rinfo()->pc() ==
            addr - Assembler::kPatchDebugBreakSlotAddressOffset);
      }
      it.next();
    }
  
    // Handle the jump to continue execution after break point depending on the
    // break location.
    if (at_js_return) {
      // If the break point as return is still active jump to the corresponding
      // place in the original code. If not the break point was removed during
      // break point processing.
      if (break_at_js_return_active) {
        addr +=  original_code->instruction_start() - code->instruction_start();
      }
  
      // Move back to where the call instruction sequence started.
      thread_local_.after_break_target_ =
          addr - Assembler::kPatchReturnSequenceAddressOffset;
    } else if (at_debug_break_slot) {
      // Address of where the debug break slot starts.
      addr = addr - Assembler::kPatchDebugBreakSlotAddressOffset;
  
      // Continue just after the slot.
      thread_local_.after_break_target_ = addr + Assembler::kDebugBreakSlotLength;
    } else if (IsDebugBreak(Assembler::target_address_at(addr))) {
      // We now know that there is still a debug break call at the target address,
      // so the break point is still there and the original code will hold the
      // address to jump to in order to complete the call which is replaced by a
      // call to DebugBreakXXX.
  
      // Find the corresponding address in the original code.
      addr += original_code->instruction_start() - code->instruction_start();
  
      // Install jump to the call address in the original code. This will be the
      // call which was overwritten by the call to DebugBreakXXX.
      thread_local_.after_break_target_ = Assembler::target_address_at(addr);
    } else {
      // There is no longer a break point present. Don't try to look in the
      // original code as the running code will have the right address. This takes
      // care of the case where the last break point is removed from the function
      // and therefore no "original code" is available.
      thread_local_.after_break_target_ = Assembler::target_address_at(addr);
    }
  }
  
  
  bool Debug::IsBreakAtReturn(JavaScriptFrame* frame) {
    HandleScope scope(isolate_);
  
    // If there are no break points this cannot be break at return, as
    // the debugger statement and stack guard bebug break cannot be at
    // return.
    if (!has_break_points_) {
      return false;
    }
  
    PrepareForBreakPoints();
  
    // Get the executing function in which the debug break occurred.
    Handle<JSFunction> function(JSFunction::cast(frame->function()));
    Handle<SharedFunctionInfo> shared(function->shared());
    if (!EnsureDebugInfo(shared, function)) {
      // Return if we failed to retrieve the debug info.
      return false;
    }
    Handle<DebugInfo> debug_info = GetDebugInfo(shared);
    Handle<Code> code(debug_info->code());
  #ifdef DEBUG
    // Get the code which is actually executing.
    Handle<Code> frame_code(frame->LookupCode());
    ASSERT(frame_code.is_identical_to(code));
  #endif
  
    // Find the call address in the running code.
    Address addr = frame->pc() - Assembler::kPatchDebugBreakSlotReturnOffset;
  
    // Check if the location is at JS return.
    RelocIterator it(debug_info->code());
    while (!it.done()) {
      if (RelocInfo::IsJSReturn(it.rinfo()->rmode())) {
        return (it.rinfo()->pc() ==
            addr - Assembler::kPatchReturnSequenceAddressOffset);
      }
      it.next();
    }
    return false;
  }
  
  
  void Debug::FramesHaveBeenDropped(StackFrame::Id new_break_frame_id,
                                    FrameDropMode mode,
                                    Object** restarter_frame_function_pointer) {
    if (mode != CURRENTLY_SET_MODE) {
      thread_local_.frame_drop_mode_ = mode;
    }
    thread_local_.break_frame_id_ = new_break_frame_id;
    thread_local_.restarter_frame_function_pointer_ =
        restarter_frame_function_pointer;
  }
  
  
  const int Debug::FramePaddingLayout::kInitialSize = 1;
  
  
  // Any even value bigger than kInitialSize as needed for stack scanning.
  const int Debug::FramePaddingLayout::kPaddingValue = kInitialSize + 1;
  
  
  bool Debug::IsDebugGlobal(GlobalObject* global) {
    return IsLoaded() && global == debug_context()->global_object();
  }
  
  
  void Debug::ClearMirrorCache() {
    PostponeInterruptsScope postpone(isolate_);
    HandleScope scope(isolate_);
    ASSERT(isolate_->context() == *Debug::debug_context());
  
    // Clear the mirror cache.
    Handle<String> function_name = isolate_->factory()->InternalizeOneByteString(
        STATIC_ASCII_VECTOR("ClearMirrorCache"));
    Handle<Object> fun(
        isolate_->global_object()->GetPropertyNoExceptionThrown(*function_name),
        isolate_);
    ASSERT(fun->IsJSFunction());
    bool caught_exception;
    Execution::TryCall(Handle<JSFunction>::cast(fun),
        Handle<JSObject>(Debug::debug_context()->global_object()),
        0, NULL, &caught_exception);
  }
  
  
  void Debug::CreateScriptCache() {
    Heap* heap = isolate_->heap();
    HandleScope scope(isolate_);
  
    // Perform two GCs to get rid of all unreferenced scripts. The first GC gets
    // rid of all the cached script wrappers and the second gets rid of the
    // scripts which are no longer referenced.  The second also sweeps precisely,
    // which saves us doing yet another GC to make the heap iterable.
    heap->CollectAllGarbage(Heap::kNoGCFlags, "Debug::CreateScriptCache");
    heap->CollectAllGarbage(Heap::kMakeHeapIterableMask,
                            "Debug::CreateScriptCache");
  
    ASSERT(script_cache_ == NULL);
    script_cache_ = new ScriptCache(isolate_);
  
    // Scan heap for Script objects.
    int count = 0;
    HeapIterator iterator(heap);
    DisallowHeapAllocation no_allocation;
  
    for (HeapObject* obj = iterator.next(); obj != NULL; obj = iterator.next()) {
      if (obj->IsScript() && Script::cast(obj)->HasValidSource()) {
        script_cache_->Add(Handle<Script>(Script::cast(obj)));
        count++;
      }
    }
  }
  
  
  void Debug::DestroyScriptCache() {
    // Get rid of the script cache if it was created.
    if (script_cache_ != NULL) {
      delete script_cache_;
      script_cache_ = NULL;
    }
  }
  
  
  void Debug::AddScriptToScriptCache(Handle<Script> script) {
    if (script_cache_ != NULL) {
      script_cache_->Add(script);
    }
  }
  
  
  Handle<FixedArray> Debug::GetLoadedScripts() {
    // Create and fill the script cache when the loaded scripts is requested for
    // the first time.
    if (script_cache_ == NULL) {
      CreateScriptCache();
    }
  
    // If the script cache is not active just return an empty array.
    ASSERT(script_cache_ != NULL);
    if (script_cache_ == NULL) {
      isolate_->factory()->NewFixedArray(0);
    }
  
    // Perform GC to get unreferenced scripts evicted from the cache before
    // returning the content.
    isolate_->heap()->CollectAllGarbage(Heap::kNoGCFlags,
                                        "Debug::GetLoadedScripts");
  
    // Get the scripts from the cache.
    return script_cache_->GetScripts();
  }
  
  
  void Debug::RecordEvalCaller(Handle<Script> script) {
    script->set_compilation_type(Script::COMPILATION_TYPE_EVAL);
    // For eval scripts add information on the function from which eval was
    // called.
    StackTraceFrameIterator it(script->GetIsolate());
    if (!it.done()) {
      script->set_eval_from_shared(it.frame()->function()->shared());
      Code* code = it.frame()->LookupCode();
      int offset = static_cast<int>(
          it.frame()->pc() - code->instruction_start());
      script->set_eval_from_instructions_offset(Smi::FromInt(offset));
    }
  }
  
  
  void Debug::AfterGarbageCollection() {
    // Generate events for collected scripts.
    if (script_cache_ != NULL) {
      script_cache_->ProcessCollectedScripts();
    }
  }
  
  
  Debugger::Debugger(Isolate* isolate)
      : debugger_access_(isolate->debugger_access()),
        event_listener_(Handle<Object>()),
        event_listener_data_(Handle<Object>()),
        compiling_natives_(false),
        is_loading_debugger_(false),
        live_edit_enabled_(true),
        never_unload_debugger_(false),
        force_debugger_active_(false),
        message_handler_(NULL),
        debugger_unload_pending_(false),
        host_dispatch_handler_(NULL),
        debug_message_dispatch_handler_(NULL),
        message_dispatch_helper_thread_(NULL),
        host_dispatch_period_(TimeDelta::FromMilliseconds(100)),
        agent_(NULL),
        command_queue_(isolate->logger(), kQueueInitialSize),
        command_received_(0),
        event_command_queue_(isolate->logger(), kQueueInitialSize),
        isolate_(isolate) {
  }
  
  
  Debugger::~Debugger() {}
  
  
  Handle<Object> Debugger::MakeJSObject(Vector<const char> constructor_name,
                                        int argc,
                                        Handle<Object> argv[],
                                        bool* caught_exception) {
    ASSERT(isolate_->context() == *isolate_->debug()->debug_context());
  
    // Create the execution state object.
    Handle<String> constructor_str =
        isolate_->factory()->InternalizeUtf8String(constructor_name);
    Handle<Object> constructor(
        isolate_->global_object()->GetPropertyNoExceptionThrown(*constructor_str),
        isolate_);
    ASSERT(constructor->IsJSFunction());
    if (!constructor->IsJSFunction()) {
      *caught_exception = true;
      return isolate_->factory()->undefined_value();
    }
    Handle<Object> js_object = Execution::TryCall(
        Handle<JSFunction>::cast(constructor),
        Handle<JSObject>(isolate_->debug()->debug_context()->global_object()),
        argc,
        argv,
        caught_exception);
    return js_object;
  }
  
  
  Handle<Object> Debugger::MakeExecutionState(bool* caught_exception) {
    // Create the execution state object.
    Handle<Object> break_id = isolate_->factory()->NewNumberFromInt(
        isolate_->debug()->break_id());
    Handle<Object> argv[] = { break_id };
    return MakeJSObject(CStrVector("MakeExecutionState"),
                        ARRAY_SIZE(argv),
                        argv,
                        caught_exception);
  }
  
  
  Handle<Object> Debugger::MakeBreakEvent(Handle<Object> exec_state,
                                          Handle<Object> break_points_hit,
                                          bool* caught_exception) {
    // Create the new break event object.
    Handle<Object> argv[] = { exec_state, break_points_hit };
    return MakeJSObject(CStrVector("MakeBreakEvent"),
                        ARRAY_SIZE(argv),
                        argv,
                        caught_exception);
  }
  
  
  Handle<Object> Debugger::MakeExceptionEvent(Handle<Object> exec_state,
                                              Handle<Object> exception,
                                              bool uncaught,
                                              bool* caught_exception) {
    Factory* factory = isolate_->factory();
    // Create the new exception event object.
    Handle<Object> argv[] = { exec_state,
                              exception,
                              factory->ToBoolean(uncaught) };
    return MakeJSObject(CStrVector("MakeExceptionEvent"),
                        ARRAY_SIZE(argv),
                        argv,
                        caught_exception);
  }
  
  
  Handle<Object> Debugger::MakeNewFunctionEvent(Handle<Object> function,
                                                bool* caught_exception) {
    // Create the new function event object.
    Handle<Object> argv[] = { function };
    return MakeJSObject(CStrVector("MakeNewFunctionEvent"),
                        ARRAY_SIZE(argv),
                        argv,
                        caught_exception);
  }
  
  
  Handle<Object> Debugger::MakeCompileEvent(Handle<Script> script,
                                            bool before,
                                            bool* caught_exception) {
    Factory* factory = isolate_->factory();
    // Create the compile event object.
    Handle<Object> exec_state = MakeExecutionState(caught_exception);
    Handle<Object> script_wrapper = GetScriptWrapper(script);
    Handle<Object> argv[] = { exec_state,
                              script_wrapper,
                              factory->ToBoolean(before) };
    return MakeJSObject(CStrVector("MakeCompileEvent"),
                        ARRAY_SIZE(argv),
                        argv,
                        caught_exception);
  }
  
  
  Handle<Object> Debugger::MakeScriptCollectedEvent(int id,
                                                    bool* caught_exception) {
    // Create the script collected event object.
    Handle<Object> exec_state = MakeExecutionState(caught_exception);
    Handle<Object> id_object = Handle<Smi>(Smi::FromInt(id), isolate_);
    Handle<Object> argv[] = { exec_state, id_object };
  
    return MakeJSObject(CStrVector("MakeScriptCollectedEvent"),
                        ARRAY_SIZE(argv),
                        argv,
                        caught_exception);
  }
  
  
  void Debugger::OnException(Handle<Object> exception, bool uncaught) {
    HandleScope scope(isolate_);
    Debug* debug = isolate_->debug();
  
    // Bail out based on state or if there is no listener for this event
    if (debug->InDebugger()) return;
    if (!Debugger::EventActive(v8::Exception)) return;
  
    // Bail out if exception breaks are not active
    if (uncaught) {
      // Uncaught exceptions are reported by either flags.
      if (!(debug->break_on_uncaught_exception() ||
            debug->break_on_exception())) return;
    } else {
      // Caught exceptions are reported is activated.
      if (!debug->break_on_exception()) return;
    }
  
    // Enter the debugger.
    EnterDebugger debugger(isolate_);
    if (debugger.FailedToEnter()) return;
  
    // Clear all current stepping setup.
    debug->ClearStepping();
    // Create the event data object.
    bool caught_exception = false;
    Handle<Object> exec_state = MakeExecutionState(&caught_exception);
    Handle<Object> event_data;
    if (!caught_exception) {
      event_data = MakeExceptionEvent(exec_state, exception, uncaught,
                                      &caught_exception);
    }
    // Bail out and don't call debugger if exception.
    if (caught_exception) {
      return;
    }
  
    // Process debug event.
    ProcessDebugEvent(v8::Exception, Handle<JSObject>::cast(event_data), false);
    // Return to continue execution from where the exception was thrown.
  }
  
  
  void Debugger::OnDebugBreak(Handle<Object> break_points_hit,
                              bool auto_continue) {
    HandleScope scope(isolate_);
  
    // Debugger has already been entered by caller.
    ASSERT(isolate_->context() == *isolate_->debug()->debug_context());
  
    // Bail out if there is no listener for this event
    if (!Debugger::EventActive(v8::Break)) return;
  
    // Debugger must be entered in advance.
    ASSERT(isolate_->context() == *isolate_->debug()->debug_context());
  
    // Create the event data object.
    bool caught_exception = false;
    Handle<Object> exec_state = MakeExecutionState(&caught_exception);
    Handle<Object> event_data;
    if (!caught_exception) {
      event_data = MakeBreakEvent(exec_state, break_points_hit,
                                  &caught_exception);
    }
    // Bail out and don't call debugger if exception.
    if (caught_exception) {
      return;
    }
  
    // Process debug event.
    ProcessDebugEvent(v8::Break,
                      Handle<JSObject>::cast(event_data),
                      auto_continue);
  }
  
  
  void Debugger::OnBeforeCompile(Handle<Script> script) {
    HandleScope scope(isolate_);
  
    // Bail out based on state or if there is no listener for this event
    if (isolate_->debug()->InDebugger()) return;
    if (compiling_natives()) return;
    if (!EventActive(v8::BeforeCompile)) return;
  
    // Enter the debugger.
    EnterDebugger debugger(isolate_);
    if (debugger.FailedToEnter()) return;
  
    // Create the event data object.
    bool caught_exception = false;
    Handle<Object> event_data = MakeCompileEvent(script, true, &caught_exception);
    // Bail out and don't call debugger if exception.
    if (caught_exception) {
      return;
    }
  
    // Process debug event.
    ProcessDebugEvent(v8::BeforeCompile,
                      Handle<JSObject>::cast(event_data),
                      true);
  }
  
  
  // Handle debugger actions when a new script is compiled.
  void Debugger::OnAfterCompile(Handle<Script> script,
                                AfterCompileFlags after_compile_flags) {
    HandleScope scope(isolate_);
    Debug* debug = isolate_->debug();
  
    // Add the newly compiled script to the script cache.
    debug->AddScriptToScriptCache(script);
  
    // No more to do if not debugging.
    if (!IsDebuggerActive()) return;
  
    // No compile events while compiling natives.
    if (compiling_natives()) return;
  
    // Store whether in debugger before entering debugger.
    bool in_debugger = debug->InDebugger();
  
    // Enter the debugger.
    EnterDebugger debugger(isolate_);
    if (debugger.FailedToEnter()) return;
  
    // If debugging there might be script break points registered for this
    // script. Make sure that these break points are set.
  
    // Get the function UpdateScriptBreakPoints (defined in debug-debugger.js).
    Handle<String> update_script_break_points_string =
        isolate_->factory()->InternalizeOneByteString(
            STATIC_ASCII_VECTOR("UpdateScriptBreakPoints"));
    Handle<Object> update_script_break_points =
        Handle<Object>(
            debug->debug_context()->global_object()->GetPropertyNoExceptionThrown(
                *update_script_break_points_string),
            isolate_);
    if (!update_script_break_points->IsJSFunction()) {
      return;
    }
    ASSERT(update_script_break_points->IsJSFunction());
  
    // Wrap the script object in a proper JS object before passing it
    // to JavaScript.
    Handle<JSValue> wrapper = GetScriptWrapper(script);
  
    // Call UpdateScriptBreakPoints expect no exceptions.
    bool caught_exception;
    Handle<Object> argv[] = { wrapper };
    Execution::TryCall(Handle<JSFunction>::cast(update_script_break_points),
                       isolate_->js_builtins_object(),
                       ARRAY_SIZE(argv),
                       argv,
                       &caught_exception);
    if (caught_exception) {
      return;
    }
    // Bail out based on state or if there is no listener for this event
    if (in_debugger && (after_compile_flags & SEND_WHEN_DEBUGGING) == 0) return;
    if (!Debugger::EventActive(v8::AfterCompile)) return;
  
    // Create the compile state object.
    Handle<Object> event_data = MakeCompileEvent(script,
                                                 false,
                                                 &caught_exception);
    // Bail out and don't call debugger if exception.
    if (caught_exception) {
      return;
    }
    // Process debug event.
    ProcessDebugEvent(v8::AfterCompile,
                      Handle<JSObject>::cast(event_data),
                      true);
  }
  
  
  void Debugger::OnScriptCollected(int id) {
    HandleScope scope(isolate_);
  
    // No more to do if not debugging.
    if (isolate_->debug()->InDebugger()) return;
    if (!IsDebuggerActive()) return;
    if (!Debugger::EventActive(v8::ScriptCollected)) return;
  
    // Enter the debugger.
    EnterDebugger debugger(isolate_);
    if (debugger.FailedToEnter()) return;
  
    // Create the script collected state object.
    bool caught_exception = false;
    Handle<Object> event_data = MakeScriptCollectedEvent(id,
                                                         &caught_exception);
    // Bail out and don't call debugger if exception.
    if (caught_exception) {
      return;
    }
  
    // Process debug event.
    ProcessDebugEvent(v8::ScriptCollected,
                      Handle<JSObject>::cast(event_data),
                      true);
  }
  
  
  void Debugger::ProcessDebugEvent(v8::DebugEvent event,
                                   Handle<JSObject> event_data,
                                   bool auto_continue) {
    HandleScope scope(isolate_);
  
    // Clear any pending debug break if this is a real break.
    if (!auto_continue) {
      isolate_->debug()->clear_interrupt_pending(DEBUGBREAK);
    }
  
    // Create the execution state.
    bool caught_exception = false;
    Handle<Object> exec_state = MakeExecutionState(&caught_exception);
    if (caught_exception) {
      return;
    }
    // First notify the message handler if any.
    if (message_handler_ != NULL) {
      NotifyMessageHandler(event,
                           Handle<JSObject>::cast(exec_state),
                           event_data,
                           auto_continue);
    }
    // Notify registered debug event listener. This can be either a C or
    // a JavaScript function. Don't call event listener for v8::Break
    // here, if it's only a debug command -- they will be processed later.
    if ((event != v8::Break || !auto_continue) && !event_listener_.is_null()) {
      CallEventCallback(event, exec_state, event_data, NULL);
    }
    // Process pending debug commands.
    if (event == v8::Break) {
      while (!event_command_queue_.IsEmpty()) {
        CommandMessage command = event_command_queue_.Get();
        if (!event_listener_.is_null()) {
          CallEventCallback(v8::BreakForCommand,
                            exec_state,
                            event_data,
                            command.client_data());
        }
        command.Dispose();
      }
    }
  }
  
  
  void Debugger::CallEventCallback(v8::DebugEvent event,
                                   Handle<Object> exec_state,
                                   Handle<Object> event_data,
                                   v8::Debug::ClientData* client_data) {
    if (event_listener_->IsForeign()) {
      CallCEventCallback(event, exec_state, event_data, client_data);
    } else {
      CallJSEventCallback(event, exec_state, event_data);
    }
  }
  
  
  void Debugger::CallCEventCallback(v8::DebugEvent event,
                                    Handle<Object> exec_state,
                                    Handle<Object> event_data,
                                    v8::Debug::ClientData* client_data) {
    Handle<Foreign> callback_obj(Handle<Foreign>::cast(event_listener_));
    v8::Debug::EventCallback2 callback =
        FUNCTION_CAST<v8::Debug::EventCallback2>(
            callback_obj->foreign_address());
    EventDetailsImpl event_details(
        event,
        Handle<JSObject>::cast(exec_state),
        Handle<JSObject>::cast(event_data),
        event_listener_data_,
        client_data);
    callback(event_details);
  }
  
  
  void Debugger::CallJSEventCallback(v8::DebugEvent event,
                                     Handle<Object> exec_state,
                                     Handle<Object> event_data) {
    ASSERT(event_listener_->IsJSFunction());
    Handle<JSFunction> fun(Handle<JSFunction>::cast(event_listener_));
  
    // Invoke the JavaScript debug event listener.
    Handle<Object> argv[] = { Handle<Object>(Smi::FromInt(event), isolate_),
                              exec_state,
                              event_data,
                              event_listener_data_ };
    bool caught_exception;
    Execution::TryCall(fun,
                       isolate_->global_object(),
                       ARRAY_SIZE(argv),
                       argv,
                       &caught_exception);
    // Silently ignore exceptions from debug event listeners.
  }
  
  
  Handle<Context> Debugger::GetDebugContext() {
    never_unload_debugger_ = true;
    EnterDebugger debugger(isolate_);
    return isolate_->debug()->debug_context();
  }
  
  
  void Debugger::UnloadDebugger() {
    Debug* debug = isolate_->debug();
  
    // Make sure that there are no breakpoints left.
    debug->ClearAllBreakPoints();
  
    // Unload the debugger if feasible.
    if (!never_unload_debugger_) {
      debug->Unload();
    }
  
    // Clear the flag indicating that the debugger should be unloaded.
    debugger_unload_pending_ = false;
  }
  
  
  void Debugger::NotifyMessageHandler(v8::DebugEvent event,
                                      Handle<JSObject> exec_state,
                                      Handle<JSObject> event_data,
                                      bool auto_continue) {
    v8::Isolate* isolate = reinterpret_cast<v8::Isolate*>(isolate_);
    HandleScope scope(isolate_);
  
    if (!isolate_->debug()->Load()) return;
  
    // Process the individual events.
    bool sendEventMessage = false;
    switch (event) {
      case v8::Break:
      case v8::BreakForCommand:
        sendEventMessage = !auto_continue;
        break;
      case v8::Exception:
        sendEventMessage = true;
        break;
      case v8::BeforeCompile:
        break;
      case v8::AfterCompile:
        sendEventMessage = true;
        break;
      case v8::ScriptCollected:
        sendEventMessage = true;
        break;
      case v8::NewFunction:
        break;
      default:
        UNREACHABLE();
    }
  
    // The debug command interrupt flag might have been set when the command was
    // added. It should be enough to clear the flag only once while we are in the
    // debugger.
    ASSERT(isolate_->debug()->InDebugger());
    isolate_->stack_guard()->Continue(DEBUGCOMMAND);
  
    // Notify the debugger that a debug event has occurred unless auto continue is
    // active in which case no event is send.
    if (sendEventMessage) {
      MessageImpl message = MessageImpl::NewEvent(
          event,
          auto_continue,
          Handle<JSObject>::cast(exec_state),
          Handle<JSObject>::cast(event_data));
      InvokeMessageHandler(message);
    }
  
    // If auto continue don't make the event cause a break, but process messages
    // in the queue if any. For script collected events don't even process
    // messages in the queue as the execution state might not be what is expected
    // by the client.
    if ((auto_continue && !HasCommands()) || event == v8::ScriptCollected) {
      return;
    }
  
    v8::TryCatch try_catch;
  
    // DebugCommandProcessor goes here.
    v8::Local<v8::Object> cmd_processor;
    {
      v8::Local<v8::Object> api_exec_state =
          v8::Utils::ToLocal(Handle<JSObject>::cast(exec_state));
      v8::Local<v8::String> fun_name = v8::String::NewFromUtf8(
          isolate, "debugCommandProcessor");
      v8::Local<v8::Function> fun =
          v8::Local<v8::Function>::Cast(api_exec_state->Get(fun_name));
  
      v8::Handle<v8::Boolean> running = v8::Boolean::New(isolate, auto_continue);
      static const int kArgc = 1;
      v8::Handle<Value> argv[kArgc] = { running };
      cmd_processor = v8::Local<v8::Object>::Cast(
          fun->Call(api_exec_state, kArgc, argv));
      if (try_catch.HasCaught()) {
        PrintLn(try_catch.Exception());
        return;
      }
    }
  
    bool running = auto_continue;
  
    // Process requests from the debugger.
    while (true) {
      // Wait for new command in the queue.
      if (Debugger::host_dispatch_handler_) {
        // In case there is a host dispatch - do periodic dispatches.
        if (!command_received_.WaitFor(host_dispatch_period_)) {
          // Timout expired, do the dispatch.
          Debugger::host_dispatch_handler_();
          continue;
        }
      } else {
        // In case there is no host dispatch - just wait.
        command_received_.Wait();
      }
  
      // Get the command from the queue.
      CommandMessage command = command_queue_.Get();
      isolate_->logger()->DebugTag(
          "Got request from command queue, in interactive loop.");
      if (!Debugger::IsDebuggerActive()) {
        // Delete command text and user data.
        command.Dispose();
        return;
      }
  
      // Invoke JavaScript to process the debug request.
      v8::Local<v8::String> fun_name;
      v8::Local<v8::Function> fun;
      v8::Local<v8::Value> request;
      v8::TryCatch try_catch;
      fun_name = v8::String::NewFromUtf8(isolate, "processDebugRequest");
      fun = v8::Local<v8::Function>::Cast(cmd_processor->Get(fun_name));
  
      request = v8::String::NewFromTwoByte(isolate, command.text().start(),
                                           v8::String::kNormalString,
                                           command.text().length());
      static const int kArgc = 1;
      v8::Handle<Value> argv[kArgc] = { request };
      v8::Local<v8::Value> response_val = fun->Call(cmd_processor, kArgc, argv);
  
      // Get the response.
      v8::Local<v8::String> response;
      if (!try_catch.HasCaught()) {
        // Get response string.
        if (!response_val->IsUndefined()) {
          response = v8::Local<v8::String>::Cast(response_val);
        } else {
          response = v8::String::NewFromUtf8(isolate, "");
        }
  
        // Log the JSON request/response.
        if (FLAG_trace_debug_json) {
          PrintLn(request);
          PrintLn(response);
        }
  
        // Get the running state.
        fun_name = v8::String::NewFromUtf8(isolate, "isRunning");
        fun = v8::Local<v8::Function>::Cast(cmd_processor->Get(fun_name));
        static const int kArgc = 1;
        v8::Handle<Value> argv[kArgc] = { response };
        v8::Local<v8::Value> running_val = fun->Call(cmd_processor, kArgc, argv);
        if (!try_catch.HasCaught()) {
          running = running_val->ToBoolean()->Value();
        }
      } else {
        // In case of failure the result text is the exception text.
        response = try_catch.Exception()->ToString();
      }
  
      // Return the result.
      MessageImpl message = MessageImpl::NewResponse(
          event,
          running,
          Handle<JSObject>::cast(exec_state),
          Handle<JSObject>::cast(event_data),
          Handle<String>(Utils::OpenHandle(*response)),
          command.client_data());
      InvokeMessageHandler(message);
      command.Dispose();
  
      // Return from debug event processing if either the VM is put into the
      // running state (through a continue command) or auto continue is active
      // and there are no more commands queued.
      if (running && !HasCommands()) {
        return;
      }
    }
  }
  
  
  void Debugger::SetEventListener(Handle<Object> callback,
                                  Handle<Object> data) {
    HandleScope scope(isolate_);
    GlobalHandles* global_handles = isolate_->global_handles();
  
    // Clear the global handles for the event listener and the event listener data
    // object.
    if (!event_listener_.is_null()) {
      GlobalHandles::Destroy(
          reinterpret_cast<Object**>(event_listener_.location()));
      event_listener_ = Handle<Object>();
    }
    if (!event_listener_data_.is_null()) {
      GlobalHandles::Destroy(
          reinterpret_cast<Object**>(event_listener_data_.location()));
      event_listener_data_ = Handle<Object>();
    }
  
    // If there is a new debug event listener register it together with its data
    // object.
    if (!callback->IsUndefined() && !callback->IsNull()) {
      event_listener_ = Handle<Object>::cast(
          global_handles->Create(*callback));
      if (data.is_null()) {
        data = isolate_->factory()->undefined_value();
      }
      event_listener_data_ = Handle<Object>::cast(
          global_handles->Create(*data));
    }
  
    ListenersChanged();
  }
  
  
  void Debugger::SetMessageHandler(v8::Debug::MessageHandler2 handler) {
    LockGuard<RecursiveMutex> with(debugger_access_);
  
    message_handler_ = handler;
    ListenersChanged();
    if (handler == NULL) {
      // Send an empty command to the debugger if in a break to make JavaScript
      // run again if the debugger is closed.
      if (isolate_->debug()->InDebugger()) {
        ProcessCommand(Vector<const uint16_t>::empty());
      }
    }
  }
  
  
  void Debugger::ListenersChanged() {
    if (IsDebuggerActive()) {
      // Disable the compilation cache when the debugger is active.
      isolate_->compilation_cache()->Disable();
      debugger_unload_pending_ = false;
    } else {
      isolate_->compilation_cache()->Enable();
      // Unload the debugger if event listener and message handler cleared.
      // Schedule this for later, because we may be in non-V8 thread.
      debugger_unload_pending_ = true;
    }
  }
  
  
  void Debugger::SetHostDispatchHandler(v8::Debug::HostDispatchHandler handler,
                                        TimeDelta period) {
    host_dispatch_handler_ = handler;
    host_dispatch_period_ = period;
  }
  
  
  void Debugger::SetDebugMessageDispatchHandler(
      v8::Debug::DebugMessageDispatchHandler handler, bool provide_locker) {
    LockGuard<Mutex> lock_guard(&dispatch_handler_access_);
    debug_message_dispatch_handler_ = handler;
  
    if (provide_locker && message_dispatch_helper_thread_ == NULL) {
      message_dispatch_helper_thread_ = new MessageDispatchHelperThread(isolate_);
      message_dispatch_helper_thread_->Start();
    }
  }
  
  
  // Calls the registered debug message handler. This callback is part of the
  // public API.
  void Debugger::InvokeMessageHandler(MessageImpl message) {
    LockGuard<RecursiveMutex> with(debugger_access_);
  
    if (message_handler_ != NULL) {
      message_handler_(message);
    }
  }
  
  
  // Puts a command coming from the public API on the queue.  Creates
  // a copy of the command string managed by the debugger.  Up to this
  // point, the command data was managed by the API client.  Called
  // by the API client thread.
  void Debugger::ProcessCommand(Vector<const uint16_t> command,
                                v8::Debug::ClientData* client_data) {
    // Need to cast away const.
    CommandMessage message = CommandMessage::New(
        Vector<uint16_t>(const_cast<uint16_t*>(command.start()),
                         command.length()),
        client_data);
    isolate_->logger()->DebugTag("Put command on command_queue.");
    command_queue_.Put(message);
    command_received_.Signal();
  
    // Set the debug command break flag to have the command processed.
    if (!isolate_->debug()->InDebugger()) {
      isolate_->stack_guard()->DebugCommand();
    }
  
    MessageDispatchHelperThread* dispatch_thread;
    {
      LockGuard<Mutex> lock_guard(&dispatch_handler_access_);
      dispatch_thread = message_dispatch_helper_thread_;
    }
  
    if (dispatch_thread == NULL) {
      CallMessageDispatchHandler();
    } else {
      dispatch_thread->Schedule();
    }
  }
  
  
  bool Debugger::HasCommands() {
    return !command_queue_.IsEmpty();
  }
  
  
  void Debugger::EnqueueDebugCommand(v8::Debug::ClientData* client_data) {
    CommandMessage message = CommandMessage::New(Vector<uint16_t>(), client_data);
    event_command_queue_.Put(message);
  
    // Set the debug command break flag to have the command processed.
    if (!isolate_->debug()->InDebugger()) {
      isolate_->stack_guard()->DebugCommand();
    }
  }
  
  
  bool Debugger::IsDebuggerActive() {
    LockGuard<RecursiveMutex> with(debugger_access_);
  
    return message_handler_ != NULL ||
        !event_listener_.is_null() ||
        force_debugger_active_;
  }
  
  
  Handle<Object> Debugger::Call(Handle<JSFunction> fun,
                                Handle<Object> data,
                                bool* pending_exception) {
    // When calling functions in the debugger prevent it from beeing unloaded.
    Debugger::never_unload_debugger_ = true;
  
    // Enter the debugger.
    EnterDebugger debugger(isolate_);
    if (debugger.FailedToEnter()) {
      return isolate_->factory()->undefined_value();
    }
  
    // Create the execution state.
    bool caught_exception = false;
    Handle<Object> exec_state = MakeExecutionState(&caught_exception);
    if (caught_exception) {
      return isolate_->factory()->undefined_value();
    }
  
    Handle<Object> argv[] = { exec_state, data };
    Handle<Object> result = Execution::Call(
        isolate_,
        fun,
        Handle<Object>(isolate_->debug()->debug_context_->global_proxy(),
                       isolate_),
        ARRAY_SIZE(argv),
        argv,
        pending_exception);
    return result;
  }
  
  
  static void StubMessageHandler2(const v8::Debug::Message& message) {
    // Simply ignore message.
  }
  
  
  bool Debugger::StartAgent(const char* name, int port,
                            bool wait_for_connection) {
    if (wait_for_connection) {
      // Suspend V8 if it is already running or set V8 to suspend whenever
      // it starts.
      // Provide stub message handler; V8 auto-continues each suspend
      // when there is no message handler; we doesn't need it.
      // Once become suspended, V8 will stay so indefinitely long, until remote
      // debugger connects and issues "continue" command.
      Debugger::message_handler_ = StubMessageHandler2;
      v8::Debug::DebugBreak();
    }
  
    if (agent_ == NULL) {
      agent_ = new DebuggerAgent(isolate_, name, port);
      agent_->Start();
    }
    return true;
  }
  
  
  void Debugger::StopAgent() {
    if (agent_ != NULL) {
      agent_->Shutdown();
      agent_->Join();
      delete agent_;
      agent_ = NULL;
    }
  }
  
  
  void Debugger::WaitForAgent() {
    if (agent_ != NULL)
      agent_->WaitUntilListening();
  }
  
  
  void Debugger::CallMessageDispatchHandler() {
    v8::Debug::DebugMessageDispatchHandler handler;
    {
      LockGuard<Mutex> lock_guard(&dispatch_handler_access_);
      handler = Debugger::debug_message_dispatch_handler_;
    }
    if (handler != NULL) {
      handler();
    }
  }
  
  
  EnterDebugger::EnterDebugger(Isolate* isolate)
      : isolate_(isolate),
        prev_(isolate_->debug()->debugger_entry()),
        it_(isolate_),
        has_js_frames_(!it_.done()),
        save_(isolate_) {
    Debug* debug = isolate_->debug();
    ASSERT(prev_ != NULL || !debug->is_interrupt_pending(PREEMPT));
    ASSERT(prev_ != NULL || !debug->is_interrupt_pending(DEBUGBREAK));
  
    // Link recursive debugger entry.
    debug->set_debugger_entry(this);
  
    // Store the previous break id and frame id.
    break_id_ = debug->break_id();
    break_frame_id_ = debug->break_frame_id();
  
    // Create the new break info. If there is no JavaScript frames there is no
    // break frame id.
    if (has_js_frames_) {
      debug->NewBreak(it_.frame()->id());
    } else {
      debug->NewBreak(StackFrame::NO_ID);
    }
  
    // Make sure that debugger is loaded and enter the debugger context.
    load_failed_ = !debug->Load();
    if (!load_failed_) {
      // NOTE the member variable save which saves the previous context before
      // this change.
      isolate_->set_context(*debug->debug_context());
    }
  }
  
  
  EnterDebugger::~EnterDebugger() {
    Debug* debug = isolate_->debug();
  
    // Restore to the previous break state.
    debug->SetBreak(break_frame_id_, break_id_);
  
    // Check for leaving the debugger.
    if (!load_failed_ && prev_ == NULL) {
      // Clear mirror cache when leaving the debugger. Skip this if there is a
      // pending exception as clearing the mirror cache calls back into
      // JavaScript. This can happen if the v8::Debug::Call is used in which
      // case the exception should end up in the calling code.
      if (!isolate_->has_pending_exception()) {
        // Try to avoid any pending debug break breaking in the clear mirror
        // cache JavaScript code.
        if (isolate_->stack_guard()->IsDebugBreak()) {
          debug->set_interrupts_pending(DEBUGBREAK);
          isolate_->stack_guard()->Continue(DEBUGBREAK);
        }
        debug->ClearMirrorCache();
      }
  
      // Request preemption and debug break when leaving the last debugger entry
      // if any of these where recorded while debugging.
      if (debug->is_interrupt_pending(PREEMPT)) {
        // This re-scheduling of preemption is to avoid starvation in some
        // debugging scenarios.
        debug->clear_interrupt_pending(PREEMPT);
        isolate_->stack_guard()->Preempt();
      }
      if (debug->is_interrupt_pending(DEBUGBREAK)) {
        debug->clear_interrupt_pending(DEBUGBREAK);
        isolate_->stack_guard()->DebugBreak();
      }
  
      // If there are commands in the queue when leaving the debugger request
      // that these commands are processed.
      if (isolate_->debugger()->HasCommands()) {
        isolate_->stack_guard()->DebugCommand();
      }
  
      // If leaving the debugger with the debugger no longer active unload it.
      if (!isolate_->debugger()->IsDebuggerActive()) {
        isolate_->debugger()->UnloadDebugger();
      }
    }
  
    // Leaving this debugger entry.
    debug->set_debugger_entry(prev_);
  }
  
  
  MessageImpl MessageImpl::NewEvent(DebugEvent event,
                                    bool running,
                                    Handle<JSObject> exec_state,
                                    Handle<JSObject> event_data) {
    MessageImpl message(true, event, running,
                        exec_state, event_data, Handle<String>(), NULL);
    return message;
  }
  
  
  MessageImpl MessageImpl::NewResponse(DebugEvent event,
                                       bool running,
                                       Handle<JSObject> exec_state,
                                       Handle<JSObject> event_data,
                                       Handle<String> response_json,
                                       v8::Debug::ClientData* client_data) {
    MessageImpl message(false, event, running,
                        exec_state, event_data, response_json, client_data);
    return message;
  }
  
  
  MessageImpl::MessageImpl(bool is_event,
                           DebugEvent event,
                           bool running,
                           Handle<JSObject> exec_state,
                           Handle<JSObject> event_data,
                           Handle<String> response_json,
                           v8::Debug::ClientData* client_data)
      : is_event_(is_event),
        event_(event),
        running_(running),
        exec_state_(exec_state),
        event_data_(event_data),
        response_json_(response_json),
        client_data_(client_data) {}
  
  
  bool MessageImpl::IsEvent() const {
    return is_event_;
  }
  
  
  bool MessageImpl::IsResponse() const {
    return !is_event_;
  }
  
  
  DebugEvent MessageImpl::GetEvent() const {
    return event_;
  }
  
  
  bool MessageImpl::WillStartRunning() const {
    return running_;
  }
  
  
  v8::Handle<v8::Object> MessageImpl::GetExecutionState() const {
    return v8::Utils::ToLocal(exec_state_);
  }
  
  
  v8::Isolate* MessageImpl::GetIsolate() const {
    return reinterpret_cast<v8::Isolate*>(exec_state_->GetIsolate());
  }
  
  
  v8::Handle<v8::Object> MessageImpl::GetEventData() const {
    return v8::Utils::ToLocal(event_data_);
  }
  
  
  v8::Handle<v8::String> MessageImpl::GetJSON() const {
    v8::EscapableHandleScope scope(
        reinterpret_cast<v8::Isolate*>(event_data_->GetIsolate()));
  
    if (IsEvent()) {
      // Call toJSONProtocol on the debug event object.
      Handle<Object> fun = GetProperty(event_data_, "toJSONProtocol");
      if (!fun->IsJSFunction()) {
        return v8::Handle<v8::String>();
      }
      bool caught_exception;
      Handle<Object> json = Execution::TryCall(Handle<JSFunction>::cast(fun),
                                               event_data_,
                                               0, NULL, &caught_exception);
      if (caught_exception || !json->IsString()) {
        return v8::Handle<v8::String>();
      }
      return scope.Escape(v8::Utils::ToLocal(Handle<String>::cast(json)));
    } else {
      return v8::Utils::ToLocal(response_json_);
    }
  }
  
  
  v8::Handle<v8::Context> MessageImpl::GetEventContext() const {
    Isolate* isolate = event_data_->GetIsolate();
    v8::Handle<v8::Context> context = GetDebugEventContext(isolate);
    // Isolate::context() may be NULL when "script collected" event occures.
    ASSERT(!context.IsEmpty() || event_ == v8::ScriptCollected);
    return context;
  }
  
  
  v8::Debug::ClientData* MessageImpl::GetClientData() const {
    return client_data_;
  }
  
  
  EventDetailsImpl::EventDetailsImpl(DebugEvent event,
                                     Handle<JSObject> exec_state,
                                     Handle<JSObject> event_data,
                                     Handle<Object> callback_data,
                                     v8::Debug::ClientData* client_data)
      : event_(event),
        exec_state_(exec_state),
        event_data_(event_data),
        callback_data_(callback_data),
        client_data_(client_data) {}
  
  
  DebugEvent EventDetailsImpl::GetEvent() const {
    return event_;
  }
  
  
  v8::Handle<v8::Object> EventDetailsImpl::GetExecutionState() const {
    return v8::Utils::ToLocal(exec_state_);
  }
  
  
  v8::Handle<v8::Object> EventDetailsImpl::GetEventData() const {
    return v8::Utils::ToLocal(event_data_);
  }
  
  
  v8::Handle<v8::Context> EventDetailsImpl::GetEventContext() const {
    return GetDebugEventContext(exec_state_->GetIsolate());
  }
  
  
  v8::Handle<v8::Value> EventDetailsImpl::GetCallbackData() const {
    return v8::Utils::ToLocal(callback_data_);
  }
  
  
  v8::Debug::ClientData* EventDetailsImpl::GetClientData() const {
    return client_data_;
  }
  
  
  CommandMessage::CommandMessage() : text_(Vector<uint16_t>::empty()),
                                     client_data_(NULL) {
  }
  
  
  CommandMessage::CommandMessage(const Vector<uint16_t>& text,
                                 v8::Debug::ClientData* data)
      : text_(text),
        client_data_(data) {
  }
  
  
  CommandMessage::~CommandMessage() {
  }
  
  
  void CommandMessage::Dispose() {
    text_.Dispose();
    delete client_data_;
    client_data_ = NULL;
  }
  
  
  CommandMessage CommandMessage::New(const Vector<uint16_t>& command,
                                     v8::Debug::ClientData* data) {
    return CommandMessage(command.Clone(), data);
  }
  
  
  CommandMessageQueue::CommandMessageQueue(int size) : start_(0), end_(0),
                                                       size_(size) {
    messages_ = NewArray<CommandMessage>(size);
  }
  
  
  CommandMessageQueue::~CommandMessageQueue() {
    while (!IsEmpty()) {
      CommandMessage m = Get();
      m.Dispose();
    }
    DeleteArray(messages_);
  }
  
  
  CommandMessage CommandMessageQueue::Get() {
    ASSERT(!IsEmpty());
    int result = start_;
    start_ = (start_ + 1) % size_;
    return messages_[result];
  }
  
  
  void CommandMessageQueue::Put(const CommandMessage& message) {
    if ((end_ + 1) % size_ == start_) {
      Expand();
    }
    messages_[end_] = message;
    end_ = (end_ + 1) % size_;
  }
  
  
  void CommandMessageQueue::Expand() {
    CommandMessageQueue new_queue(size_ * 2);
    while (!IsEmpty()) {
      new_queue.Put(Get());
    }
    CommandMessage* array_to_free = messages_;
    *this = new_queue;
    new_queue.messages_ = array_to_free;
    // Make the new_queue empty so that it doesn't call Dispose on any messages.
    new_queue.start_ = new_queue.end_;
    // Automatic destructor called on new_queue, freeing array_to_free.
  }
  
  
  LockingCommandMessageQueue::LockingCommandMessageQueue(Logger* logger, int size)
      : logger_(logger), queue_(size) {}
  
  
  bool LockingCommandMessageQueue::IsEmpty() const {
    LockGuard<Mutex> lock_guard(&mutex_);
    return queue_.IsEmpty();
  }
  
  
  CommandMessage LockingCommandMessageQueue::Get() {
    LockGuard<Mutex> lock_guard(&mutex_);
    CommandMessage result = queue_.Get();
    logger_->DebugEvent("Get", result.text());
    return result;
  }
  
  
  void LockingCommandMessageQueue::Put(const CommandMessage& message) {
    LockGuard<Mutex> lock_guard(&mutex_);
    queue_.Put(message);
    logger_->DebugEvent("Put", message.text());
  }
  
  
  void LockingCommandMessageQueue::Clear() {
    LockGuard<Mutex> lock_guard(&mutex_);
    queue_.Clear();
  }
  
  
  MessageDispatchHelperThread::MessageDispatchHelperThread(Isolate* isolate)
      : Thread("v8:MsgDispHelpr"),
        isolate_(isolate), sem_(0),
        already_signalled_(false) {
  }
  
  
  void MessageDispatchHelperThread::Schedule() {
    {
      LockGuard<Mutex> lock_guard(&mutex_);
      if (already_signalled_) {
        return;
      }
      already_signalled_ = true;
    }
    sem_.Signal();
  }
  
  
  void MessageDispatchHelperThread::Run() {
    while (true) {
      sem_.Wait();
      {
        LockGuard<Mutex> lock_guard(&mutex_);
        already_signalled_ = false;
      }
      {
        Locker locker(reinterpret_cast<v8::Isolate*>(isolate_));
        isolate_->debugger()->CallMessageDispatchHandler();
      }
    }
  }
  
  #endif  // ENABLE_DEBUGGER_SUPPORT
  
  } }  // namespace v8::internal
  