Move V8 to external/v8

Change-Id: If68025d67453785a651c5dfb34fad298c16676a4

1 files changed, 869 insertions, 0 deletions

diff --git a/src/debug.h b/src/debug.h
new file mode 100644
index 00000000..29c2bc20
--- /dev/null
+++ b/src/debug.h
@@ -0,0 +1,869 @@
+// 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 "hashmap.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();
+  }
+
+  bool IsDebuggerStatement();
+
+ protected:
+  bool RinfoDone() const;
+  void RinfoNext();
+
+  BreakLocatorType type_;
+  int break_point_;
+  int position_;
+  int statement_position_;
+  Handle<DebugInfo> debug_info_;
+  Handle<Code> debug_break_stub_;
+  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);
+};
+
+
+// Cache of all script objects in the heap. When a script is added a weak handle
+// to it is created and that weak handle is stored in the cache. The weak handle
+// callback takes care of removing the script from the cache. The key used in
+// the cache is the script id.
+class ScriptCache : private HashMap {
+ public:
+  ScriptCache() : HashMap(ScriptMatch), collected_scripts_(10) {}
+  virtual ~ScriptCache() { Clear(); }
+
+  // Add script to the cache.
+  void Add(Handle<Script> script);
+
+  // Return the scripts in the cache.
+  Handle<FixedArray> GetScripts();
+
+  // Generate debugger events for collected scripts.
+  void ProcessCollectedScripts();
+
+ private:
+  // Calculate the hash value from the key (script id).
+  static uint32_t Hash(int key) { return ComputeIntegerHash(key); }
+
+  // Scripts match if their keys (script id) match.
+  static bool ScriptMatch(void* key1, void* key2) { return key1 == key2; }
+
+  // Clear the cache releasing all the weak handles.
+  void Clear();
+
+  // Weak handle callback for scripts in the cache.
+  static void HandleWeakScript(v8::Persistent<v8::Value> obj, void* data);
+
+  // List used during GC to temporarily store id's of collected scripts.
+  List<int> collected_scripts_;
+};
+
+
+// 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);
+
+  // Returns true if the current stub call is patched to call the debugger.
+  static bool IsDebugBreak(Address addr);
+  // Returns true if the current return statement has been patched to be
+  // a debugger breakpoint.
+  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,
+                           Handle<Object> holder,
+                           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 bool StepOutActive() { return thread_local_.step_out_fp_ != 0; }
+  static Address step_out_fp() { return thread_local_.step_out_fp_; }
+
+  static EnterDebugger* debugger_entry() {
+    return thread_local_.debugger_entry_;
+  }
+  static void set_debugger_entry(EnterDebugger* entry) {
+    thread_local_.debugger_entry_ = entry;
+  }
+
+  // Check whether any of the specified interrupts are pending.
+  static bool is_interrupt_pending(InterruptFlag what) {
+    return (thread_local_.pending_interrupts_ & what) != 0;
+  }
+
+  // Set specified interrupts as pending.
+  static void set_interrupts_pending(InterruptFlag what) {
+    thread_local_.pending_interrupts_ |= what;
+  }
+
+  // Clear specified interrupts from pending.
+  static void clear_interrupt_pending(InterruptFlag what) {
+    thread_local_.pending_interrupts_ &= ~static_cast<int>(what);
+  }
+
+  // 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];
+  }
+
+  // Access to the debug break on return code.
+  static Code* debug_break_return() { return debug_break_return_; }
+  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();
+  static void FreeThreadResources() { }
+
+  // Mirror cache handling.
+  static void ClearMirrorCache();
+
+  // Script cache handling.
+  static void CreateScriptCache();
+  static void DestroyScriptCache();
+  static void AddScriptToScriptCache(Handle<Script> script);
+  static Handle<FixedArray> GetLoadedScripts();
+
+  // Garbage collection notifications.
+  static void AfterGarbageCollection();
+
+  // Code generation assumptions.
+  static const int kIa32CallInstructionLength = 5;
+  static const int kIa32JSReturnSequenceLength = 6;
+
+  // The x64 JS return sequence is padded with int3 to make it large
+  // enough to hold a call instruction when the debugger patches it.
+  static const int kX64CallInstructionLength = 13;
+  static const int kX64JSReturnSequenceLength = 13;
+
+  // 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 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 ActivateStepOut(StackFrame* frame);
+  static void ClearStepOut();
+  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_;
+
+  // Cache of all scripts in the heap.
+  static ScriptCache* script_cache_;
+
+  // List of active debug info objects.
+  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_;
+
+    // Frame pointer for the frame where debugger should be called when current
+    // step out action is completed.
+    Address step_out_fp_;
+
+    // Storage location for jump when exiting debug break calls.
+    Address after_break_target_;
+
+    // Top debugger entry.
+    EnterDebugger* debugger_entry_;
+
+    // Pending interrupts scheduled while debugging.
+    int pending_interrupts_;
+  };
+
+  // Storage location for registers when handling debug break calls
+  static JSCallerSavedBuffer registers_;
+  static ThreadLocal thread_local_;
+  static void ThreadInit();
+
+  // 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 Handle<Object> MakeScriptCollectedEvent(int id,
+                                                 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 OnScriptCollected(int id);
+  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();
+
+  // Blocks until the agent has started listening for connections
+  static void WaitForAgent();
+
+  // 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 (debugger_unload_pending_) {
+      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 void ListenersChanged();
+
+  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 debugger_unload_pending_;  // 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::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.
+      Top::set_context(*Debug::debug_context());
+    }
+  }
+
+  ~EnterDebugger() {
+    // Restore to the previous break state.
+    Debug::SetBreak(break_frame_id_, break_id_);
+
+    // Check for leaving the debugger.
+    if (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 (!Top::has_pending_exception()) {
+        // Try to avoid any pending debug break breaking in the clear mirror
+        // cache JavaScript code.
+        if (StackGuard::IsDebugBreak()) {
+          Debug::set_interrupts_pending(DEBUGBREAK);
+          StackGuard::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);
+        StackGuard::Preempt();
+      }
+      if (Debug::is_interrupt_pending(DEBUGBREAK)) {
+        Debug::clear_interrupt_pending(DEBUGBREAK);
+        StackGuard::DebugBreak();
+      }
+
+      // If there are commands in the queue when leaving the debugger request
+      // that these commands are processed.
+      if (Debugger::HasCommands()) {
+        StackGuard::DebugCommand();
+      }
+
+      // If leaving the debugger with the debugger no longer active unload it.
+      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_