text: // Copyright 2006-2008 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.
  
  #ifndef V8_DEBUG_H_
  #define V8_DEBUG_H_
  
  #include "assembler.h"
  #include "code-stubs.h"
  #include "debug-agent.h"
  #include "execution.h"
  #include "factory.h"
  #include "platform.h"
  #include "string-stream.h"
  #include "v8threads.h"
  
  #ifdef ENABLE_DEBUGGER_SUPPORT
  #include "../include/v8-debug.h"
  
  namespace v8 { namespace internal {
  
  
  // Forward declarations.
  class EnterDebugger;
  
  
  // Step actions. NOTE: These values are in macros.py as well.
  enum StepAction {
    StepNone = -1,  // Stepping not prepared.
    StepOut = 0,   // Step out of the current function.
    StepNext = 1,  // Step to the next statement in the current function.
    StepIn = 2,    // Step into new functions invoked or the next statement
                   // in the current function.
    StepMin = 3,   // Perform a minimum step in the current function.
    StepInMin = 4  // Step into new functions invoked or perform a minimum step
                   // in the current function.
  };
  
  
  // Type of exception break. NOTE: These values are in macros.py as well.
  enum ExceptionBreakType {
    BreakException = 0,
    BreakUncaughtException = 1
  };
  
  
  // Type of exception break. NOTE: These values are in macros.py as well.
  enum BreakLocatorType {
    ALL_BREAK_LOCATIONS = 0,
    SOURCE_BREAK_LOCATIONS = 1
  };
  
  
  // Class for iterating through the break points in a function and changing
  // them.
  class BreakLocationIterator {
   public:
    explicit BreakLocationIterator(Handle<DebugInfo> debug_info,
                                   BreakLocatorType type);
    virtual ~BreakLocationIterator();
  
    void Next();
    void Next(int count);
    void FindBreakLocationFromAddress(Address pc);
    void FindBreakLocationFromPosition(int position);
    void Reset();
    bool Done() const;
    void SetBreakPoint(Handle<Object> break_point_object);
    void ClearBreakPoint(Handle<Object> break_point_object);
    void SetOneShot();
    void ClearOneShot();
    void PrepareStepIn();
    bool IsExit() const;
    bool HasBreakPoint();
    bool IsDebugBreak();
    Object* BreakPointObjects();
    void ClearAllDebugBreak();
  
  
    inline int code_position() { return pc() - debug_info_->code()->entry(); }
    inline int break_point() { return break_point_; }
    inline int position() { return position_; }
    inline int statement_position() { return statement_position_; }
    inline Address pc() { return reloc_iterator_->rinfo()->pc(); }
    inline Code* code() { return debug_info_->code(); }
    inline RelocInfo* rinfo() { return reloc_iterator_->rinfo(); }
    inline RelocInfo::Mode rmode() const {
      return reloc_iterator_->rinfo()->rmode();
    }
    inline RelocInfo* original_rinfo() {
      return reloc_iterator_original_->rinfo();
    }
    inline RelocInfo::Mode original_rmode() const {
      return reloc_iterator_original_->rinfo()->rmode();
    }
  
   protected:
    bool RinfoDone() const;
    void RinfoNext();
  
    BreakLocatorType type_;
    int break_point_;
    int position_;
    int statement_position_;
    Handle<DebugInfo> debug_info_;
    RelocIterator* reloc_iterator_;
    RelocIterator* reloc_iterator_original_;
  
   private:
    void SetDebugBreak();
    void ClearDebugBreak();
  
    void SetDebugBreakAtIC();
    void ClearDebugBreakAtIC();
  
    bool IsDebugBreakAtReturn();
    void SetDebugBreakAtReturn();
    void ClearDebugBreakAtReturn();
  
    DISALLOW_COPY_AND_ASSIGN(BreakLocationIterator);
  };
  
  
  // Linked list holding debug info objects. The debug info objects are kept as
  // weak handles to avoid a debug info object to keep a function alive.
  class DebugInfoListNode {
   public:
    explicit DebugInfoListNode(DebugInfo* debug_info);
    virtual ~DebugInfoListNode();
  
    DebugInfoListNode* next() { return next_; }
    void set_next(DebugInfoListNode* next) { next_ = next; }
    Handle<DebugInfo> debug_info() { return debug_info_; }
  
   private:
    // Global (weak) handle to the debug info object.
    Handle<DebugInfo> debug_info_;
  
    // Next pointer for linked list.
    DebugInfoListNode* next_;
  };
  
  
  // This class contains the debugger support. The main purpose is to handle
  // setting break points in the code.
  //
  // This class controls the debug info for all functions which currently have
  // active breakpoints in them. This debug info is held in the heap root object
  // debug_info which is a FixedArray. Each entry in this list is of class
  // DebugInfo.
  class Debug {
   public:
    static void Setup(bool create_heap_objects);
    static bool Load();
    static void Unload();
    static bool IsLoaded() { return !debug_context_.is_null(); }
    static bool InDebugger() { return thread_local_.debugger_entry_ != NULL; }
    static void PreemptionWhileInDebugger();
    static void Iterate(ObjectVisitor* v);
  
    static Object* Break(Arguments args);
    static void SetBreakPoint(Handle<SharedFunctionInfo> shared,
                              int source_position,
                              Handle<Object> break_point_object);
    static void ClearBreakPoint(Handle<Object> break_point_object);
    static void ClearAllBreakPoints();
    static void FloodWithOneShot(Handle<SharedFunctionInfo> shared);
    static void FloodHandlerWithOneShot();
    static void ChangeBreakOnException(ExceptionBreakType type, bool enable);
    static void PrepareStep(StepAction step_action, int step_count);
    static void ClearStepping();
    static bool StepNextContinue(BreakLocationIterator* break_location_iterator,
                                 JavaScriptFrame* frame);
    static Handle<DebugInfo> GetDebugInfo(Handle<SharedFunctionInfo> shared);
    static bool HasDebugInfo(Handle<SharedFunctionInfo> shared);
  
    // Returns whether the operation succeeded.
    static bool EnsureDebugInfo(Handle<SharedFunctionInfo> shared);
  
    static bool IsDebugBreak(Address addr);
    static bool IsDebugBreakAtReturn(RelocInfo* rinfo);
  
    // Check whether a code stub with the specified major key is a possible break
    // point location.
    static bool IsSourceBreakStub(Code* code);
    static bool IsBreakStub(Code* code);
  
    // Find the builtin to use for invoking the debug break
    static Handle<Code> FindDebugBreak(Handle<Code> code, RelocInfo::Mode mode);
  
    static Handle<Object> GetSourceBreakLocations(
        Handle<SharedFunctionInfo> shared);
  
    // Getter for the debug_context.
    inline static Handle<Context> debug_context() { return debug_context_; }
  
    // Check whether a global object is the debug global object.
    static bool IsDebugGlobal(GlobalObject* global);
  
    // Fast check to see if any break points are active.
    inline static bool has_break_points() { return has_break_points_; }
  
    static void NewBreak(StackFrame::Id break_frame_id);
    static void SetBreak(StackFrame::Id break_frame_id, int break_id);
    static StackFrame::Id break_frame_id() {
      return thread_local_.break_frame_id_;
    }
    static int break_id() { return thread_local_.break_id_; }
  
  
  
  
    static bool StepInActive() { return thread_local_.step_into_fp_ != 0; }
    static void HandleStepIn(Handle<JSFunction> function,
                             Address fp,
                             bool is_constructor);
    static Address step_in_fp() { return thread_local_.step_into_fp_; }
    static Address* step_in_fp_addr() { return &thread_local_.step_into_fp_; }
  
    static EnterDebugger* debugger_entry() {
      return thread_local_.debugger_entry_;
    }
    static void set_debugger_entry(EnterDebugger* entry) {
      thread_local_.debugger_entry_ = entry;
    }
  
    static bool preemption_pending() {
      return thread_local_.preemption_pending_;
    }
    static void set_preemption_pending(bool preemption_pending) {
      thread_local_.preemption_pending_ = preemption_pending;
    }
  
    // Getter and setter for the disable break state.
    static bool disable_break() { return disable_break_; }
    static void set_disable_break(bool disable_break) {
      disable_break_ = disable_break;
    }
  
    // Getters for the current exception break state.
    static bool break_on_exception() { return break_on_exception_; }
    static bool break_on_uncaught_exception() {
      return break_on_uncaught_exception_;
    }
  
    enum AddressId {
      k_after_break_target_address,
      k_debug_break_return_address,
      k_register_address
    };
  
    // Support for setting the address to jump to when returning from break point.
    static Address* after_break_target_address() {
      return reinterpret_cast<Address*>(&thread_local_.after_break_target_);
    }
  
    // Support for saving/restoring registers when handling debug break calls.
    static Object** register_address(int r) {
      return &registers_[r];
    }
  
    // Address of the debug break return entry code.
    static Code* debug_break_return_entry() { return debug_break_return_entry_; }
  
    // Support for getting the address of the debug break on return code.
    static Code** debug_break_return_address() {
      return &debug_break_return_;
    }
  
    static const int kEstimatedNofDebugInfoEntries = 16;
    static const int kEstimatedNofBreakPointsInFunction = 16;
  
    static void HandleWeakDebugInfo(v8::Persistent<v8::Value> obj, void* data);
  
    friend class Debugger;
    friend Handle<FixedArray> GetDebuggedFunctions();  // In test-debug.cc
    friend void CheckDebuggerUnloaded(bool check_functions);  // In test-debug.cc
  
    // Threading support.
    static char* ArchiveDebug(char* to);
    static char* RestoreDebug(char* from);
    static int ArchiveSpacePerThread();
  
    // Mirror cache handling.
    static void ClearMirrorCache();
  
    // Code generation assumptions.
    static const int kIa32CallInstructionLength = 5;
    static const int kIa32JSReturnSequenceLength = 6;
  
    // Code generator routines.
    static void GenerateLoadICDebugBreak(MacroAssembler* masm);
    static void GenerateStoreICDebugBreak(MacroAssembler* masm);
    static void GenerateKeyedLoadICDebugBreak(MacroAssembler* masm);
    static void GenerateKeyedStoreICDebugBreak(MacroAssembler* masm);
    static void GenerateConstructCallDebugBreak(MacroAssembler* masm);
    static void GenerateReturnDebugBreak(MacroAssembler* masm);
    static void GenerateReturnDebugBreakEntry(MacroAssembler* masm);
    static void GenerateStubNoRegistersDebugBreak(MacroAssembler* masm);
  
    // Called from stub-cache.cc.
    static void GenerateCallICDebugBreak(MacroAssembler* masm);
  
   private:
    static bool CompileDebuggerScript(int index);
    static void ClearOneShot();
    static void ActivateStepIn(StackFrame* frame);
    static void ClearStepIn();
    static void ClearStepNext();
    // Returns whether the compile succeeded.
    static bool EnsureCompiled(Handle<SharedFunctionInfo> shared);
    static void RemoveDebugInfo(Handle<DebugInfo> debug_info);
    static void SetAfterBreakTarget(JavaScriptFrame* frame);
    static Handle<Object> CheckBreakPoints(Handle<Object> break_point);
    static bool CheckBreakPoint(Handle<Object> break_point_object);
  
    // Global handle to debug context where all the debugger JavaScript code is
    // loaded.
    static Handle<Context> debug_context_;
  
    // Boolean state indicating whether any break points are set.
    static bool has_break_points_;
    static DebugInfoListNode* debug_info_list_;
  
    static bool disable_break_;
    static bool break_on_exception_;
    static bool break_on_uncaught_exception_;
  
    // Per-thread data.
    class ThreadLocal {
     public:
      // Counter for generating next break id.
      int break_count_;
  
      // Current break id.
      int break_id_;
  
      // Frame id for the frame of the current break.
      StackFrame::Id break_frame_id_;
  
      // Step action for last step performed.
      StepAction last_step_action_;
  
      // Source statement position from last step next action.
      int last_statement_position_;
  
      // Number of steps left to perform before debug event.
      int step_count_;
  
      // Frame pointer from last step next action.
      Address last_fp_;
  
      // Frame pointer for frame from which step in was performed.
      Address step_into_fp_;
  
      // Storage location for jump when exiting debug break calls.
      Address after_break_target_;
  
      // Top debugger entry.
      EnterDebugger* debugger_entry_;
  
      // Preemption happened while debugging.
      bool preemption_pending_;
    };
  
    // Storage location for registers when handling debug break calls
    static JSCallerSavedBuffer registers_;
    static ThreadLocal thread_local_;
    static void ThreadInit();
  
    // Code object for debug break return entry code.
    static Code* debug_break_return_entry_;
  
    // Code to call for handling debug break on return.
    static Code* debug_break_return_;
  
    DISALLOW_COPY_AND_ASSIGN(Debug);
  };
  
  
  // Message delivered to the message handler callback. This is either a debugger
  // event or the response to a command.
  class MessageImpl: public v8::Debug::Message {
   public:
    // Create a message object for a debug event.
    static MessageImpl NewEvent(DebugEvent event,
                                bool running,
                                Handle<JSObject> exec_state,
                                Handle<JSObject> event_data);
  
    // Create a message object for the response to a debug command.
    static MessageImpl NewResponse(DebugEvent event,
                                   bool running,
                                   Handle<JSObject> exec_state,
                                   Handle<JSObject> event_data,
                                   Handle<String> response_json,
                                   v8::Debug::ClientData* client_data);
  
    // Implementation of interface v8::Debug::Message.
    virtual bool IsEvent() const;
    virtual bool IsResponse() const;
    virtual DebugEvent GetEvent() const;
    virtual bool WillStartRunning() const;
    virtual v8::Handle<v8::Object> GetExecutionState() const;
    virtual v8::Handle<v8::Object> GetEventData() const;
    virtual v8::Handle<v8::String> GetJSON() const;
    virtual v8::Handle<v8::Context> GetEventContext() const;
    virtual v8::Debug::ClientData* GetClientData() const;
  
   private:
    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);
  
    bool is_event_;  // Does this message represent a debug event?
    DebugEvent event_;  // Debug event causing the break.
    bool running_;  // Will the VM start running after this event?
    Handle<JSObject> exec_state_;  // Current execution state.
    Handle<JSObject> event_data_;  // Data associated with the event.
    Handle<String> response_json_;  // Response JSON if message holds a response.
    v8::Debug::ClientData* client_data_;  // Client data passed with the request.
  };
  
  
  // Message send by user to v8 debugger or debugger output message.
  // In addition to command text it may contain a pointer to some user data
  // which are expected to be passed along with the command reponse to message
  // handler.
  class CommandMessage {
   public:
    static CommandMessage New(const Vector<uint16_t>& command,
                              v8::Debug::ClientData* data);
    CommandMessage();
    ~CommandMessage();
  
    // Deletes user data and disposes of the text.
    void Dispose();
    Vector<uint16_t> text() const { return text_; }
    v8::Debug::ClientData* client_data() const { return client_data_; }
   private:
    CommandMessage(const Vector<uint16_t>& text,
                   v8::Debug::ClientData* data);
  
    Vector<uint16_t> text_;
    v8::Debug::ClientData* client_data_;
  };
  
  // A Queue of CommandMessage objects.  A thread-safe version is
  // LockingCommandMessageQueue, based on this class.
  class CommandMessageQueue BASE_EMBEDDED {
   public:
    explicit CommandMessageQueue(int size);
    ~CommandMessageQueue();
    bool IsEmpty() const { return start_ == end_; }
    CommandMessage Get();
    void Put(const CommandMessage& message);
    void Clear() { start_ = end_ = 0; }  // Queue is empty after Clear().
   private:
    // Doubles the size of the message queue, and copies the messages.
    void Expand();
  
    CommandMessage* messages_;
    int start_;
    int end_;
    int size_;  // The size of the queue buffer.  Queue can hold size-1 messages.
  };
  
  
  // LockingCommandMessageQueue is a thread-safe circular buffer of CommandMessage
  // messages.  The message data is not managed by LockingCommandMessageQueue.
  // Pointers to the data are passed in and out. Implemented by adding a
  // Mutex to CommandMessageQueue.  Includes logging of all puts and gets.
  class LockingCommandMessageQueue BASE_EMBEDDED {
   public:
    explicit LockingCommandMessageQueue(int size);
    ~LockingCommandMessageQueue();
    bool IsEmpty() const;
    CommandMessage Get();
    void Put(const CommandMessage& message);
    void Clear();
   private:
    CommandMessageQueue queue_;
    Mutex* lock_;
    DISALLOW_COPY_AND_ASSIGN(LockingCommandMessageQueue);
  };
  
  
  class Debugger {
   public:
    static void DebugRequest(const uint16_t* json_request, int length);
  
    static Handle<Object> MakeJSObject(Vector<const char> constructor_name,
                                       int argc, Object*** argv,
                                       bool* caught_exception);
    static Handle<Object> MakeExecutionState(bool* caught_exception);
    static Handle<Object> MakeBreakEvent(Handle<Object> exec_state,
                                         Handle<Object> break_points_hit,
                                         bool* caught_exception);
    static Handle<Object> MakeExceptionEvent(Handle<Object> exec_state,
                                             Handle<Object> exception,
                                             bool uncaught,
                                             bool* caught_exception);
    static Handle<Object> MakeNewFunctionEvent(Handle<Object> func,
                                               bool* caught_exception);
    static Handle<Object> MakeCompileEvent(Handle<Script> script,
                                           bool before,
                                           bool* caught_exception);
    static void OnDebugBreak(Handle<Object> break_points_hit, bool auto_continue);
    static void OnException(Handle<Object> exception, bool uncaught);
    static void OnBeforeCompile(Handle<Script> script);
    static void OnAfterCompile(Handle<Script> script,
                             Handle<JSFunction> fun);
    static void OnNewFunction(Handle<JSFunction> fun);
    static void ProcessDebugEvent(v8::DebugEvent event,
                                  Handle<JSObject> event_data,
                                  bool auto_continue);
    static void NotifyMessageHandler(v8::DebugEvent event,
                                     Handle<JSObject> exec_state,
                                     Handle<JSObject> event_data,
                                     bool auto_continue);
    static void SetEventListener(Handle<Object> callback, Handle<Object> data);
    static void SetMessageHandler(v8::Debug::MessageHandler2 handler);
    static void SetHostDispatchHandler(v8::Debug::HostDispatchHandler handler,
                                       int period);
  
    // Invoke the message handler function.
    static void InvokeMessageHandler(MessageImpl message);
  
    // Add a debugger command to the command queue.
    static void ProcessCommand(Vector<const uint16_t> command,
                               v8::Debug::ClientData* client_data = NULL);
  
    // Check whether there are commands in the command queue.
    static bool HasCommands();
  
    static Handle<Object> Call(Handle<JSFunction> fun,
                               Handle<Object> data,
                               bool* pending_exception);
  
    // Start the debugger agent listening on the provided port.
    static bool StartAgent(const char* name, int port);
  
    // Stop the debugger agent.
    static void StopAgent();
  
    // Unload the debugger if possible. Only called when no debugger is currently
    // active.
    static void UnloadDebugger();
  
    inline static bool EventActive(v8::DebugEvent event) {
      ScopedLock with(debugger_access_);
  
      // Check whether the message handler was been cleared.
      if (message_handler_cleared_) {
        UnloadDebugger();
      }
  
      // Currently argument event is not used.
      return !compiling_natives_ && Debugger::IsDebuggerActive();
    }
  
    static void set_compiling_natives(bool compiling_natives) {
      Debugger::compiling_natives_ = compiling_natives;
    }
    static bool compiling_natives() { return Debugger::compiling_natives_; }
    static void set_loading_debugger(bool v) { is_loading_debugger_ = v; }
    static bool is_loading_debugger() { return Debugger::is_loading_debugger_; }
  
   private:
    static bool IsDebuggerActive();
  
    static Mutex* debugger_access_;  // Mutex guarding debugger variables.
    static Handle<Object> event_listener_;  // Global handle to listener.
    static Handle<Object> event_listener_data_;
    static bool compiling_natives_;  // Are we compiling natives?
    static bool is_loading_debugger_;  // Are we loading the debugger?
    static bool never_unload_debugger_;  // Can we unload the debugger?
    static v8::Debug::MessageHandler2 message_handler_;
    static bool message_handler_cleared_;  // Was message handler cleared?
    static v8::Debug::HostDispatchHandler host_dispatch_handler_;
    static int host_dispatch_micros_;
  
    static DebuggerAgent* agent_;
  
    static const int kQueueInitialSize = 4;
    static LockingCommandMessageQueue command_queue_;
    static Semaphore* command_received_;  // Signaled for each command received.
  
    friend class EnterDebugger;
  };
  
  
  // This class is used for entering the debugger. Create an instance in the stack
  // to enter the debugger. This will set the current break state, make sure the
  // debugger is loaded and switch to the debugger context. If the debugger for
  // some reason could not be entered FailedToEnter will return true.
  class EnterDebugger BASE_EMBEDDED {
   public:
    EnterDebugger()
        : prev_(Debug::debugger_entry()),
          has_js_frames_(!it_.done()) {
      ASSERT(prev_ == NULL ? !Debug::preemption_pending() : true);
  
      // 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.
        Top::set_context(*Debug::debug_context());
      }
    }
  
    ~EnterDebugger() {
      // Restore to the previous break state.
      Debug::SetBreak(break_frame_id_, break_id_);
  
      // Request preemption when leaving the last debugger entry and a preemption
      // had been recorded while debugging. This is to avoid starvation in some
      // debugging scenarios.
      if (prev_ == NULL && Debug::preemption_pending()) {
        StackGuard::Preempt();
        Debug::set_preemption_pending(false);
      }
  
      // If there are commands in the queue when leaving the debugger request that
      // these commands are processed.
      if (prev_ == NULL && Debugger::HasCommands()) {
        StackGuard::DebugCommand();
      }
  
      // If leaving the debugger with the debugger no longer active unload it.
      if (prev_ == NULL) {
        if (!Debugger::IsDebuggerActive()) {
          Debugger::UnloadDebugger();
        }
      }
  
      // Leaving this debugger entry.
      Debug::set_debugger_entry(prev_);
    }
  
    // Check whether the debugger could be entered.
    inline bool FailedToEnter() { return load_failed_; }
  
    // Check whether there are any JavaScript frames on the stack.
    inline bool HasJavaScriptFrames() { return has_js_frames_; }
  
    // Get the active context from before entering the debugger.
    inline Handle<Context> GetContext() { return save_.context(); }
  
   private:
    EnterDebugger* prev_;  // Previous debugger entry if entered recursively.
    JavaScriptFrameIterator it_;
    const bool has_js_frames_;  // Were there any JavaScript frames?
    StackFrame::Id break_frame_id_;  // Previous break frame id.
    int break_id_;  // Previous break id.
    bool load_failed_;  // Did the debugger fail to load?
    SaveContext save_;  // Saves previous context.
  };
  
  
  // Stack allocated class for disabling break.
  class DisableBreak BASE_EMBEDDED {
   public:
    // Enter the debugger by storing the previous top context and setting the
    // current top context to the debugger context.
    explicit DisableBreak(bool disable_break)  {
      prev_disable_break_ = Debug::disable_break();
      Debug::set_disable_break(disable_break);
    }
    ~DisableBreak() {
      Debug::set_disable_break(prev_disable_break_);
    }
  
   private:
    // The previous state of the disable break used to restore the value when this
    // object is destructed.
    bool prev_disable_break_;
  };
  
  
  // Debug_Address encapsulates the Address pointers used in generating debug
  // code.
  class Debug_Address {
   public:
    Debug_Address(Debug::AddressId id, int reg = 0)
      : id_(id), reg_(reg) {
      ASSERT(reg == 0 || id == Debug::k_register_address);
    }
  
    static Debug_Address AfterBreakTarget() {
      return Debug_Address(Debug::k_after_break_target_address);
    }
  
    static Debug_Address DebugBreakReturn() {
      return Debug_Address(Debug::k_debug_break_return_address);
    }
  
    static Debug_Address Register(int reg) {
      return Debug_Address(Debug::k_register_address, reg);
    }
  
    Address address() const {
      switch (id_) {
        case Debug::k_after_break_target_address:
          return reinterpret_cast<Address>(Debug::after_break_target_address());
        case Debug::k_debug_break_return_address:
          return reinterpret_cast<Address>(Debug::debug_break_return_address());
        case Debug::k_register_address:
          return reinterpret_cast<Address>(Debug::register_address(reg_));
        default:
          UNREACHABLE();
          return NULL;
      }
    }
   private:
    Debug::AddressId id_;
    int reg_;
  };
  
  
  } }  // namespace v8::internal
  
  #endif  // ENABLE_DEBUGGER_SUPPORT
  
  #endif  // V8_DEBUG_H_
  