v8/src/execution.h

// 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.
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//       contributors may be used to endorse or promote products derived
//       from this software without specific prior written permission.
//
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#ifndef V8_EXECUTION_H_
#define V8_EXECUTION_H_

namespace v8 { namespace internal {


// Flag used to set the interrupt causes.
enum InterruptFlag {
  INTERRUPT = 1 << 0,
  DEBUGBREAK = 1 << 1,
  PREEMPT = 1 << 2
};

class Execution : public AllStatic {
 public:
  // Call a function, the caller supplies a receiver and an array
  // of arguments. Arguments are Object* type. After function returns,
  // pointers in 'args' might be invalid.
  //
  // *pending_exception tells whether the invoke resulted in
  // a pending exception.
  //
  static Handle<Object> Call(Handle<JSFunction> func,
                             Handle<Object> receiver,
                             int argc,
                             Object*** args,
                             bool* pending_exception);

  // Construct object from function, the caller supplies an array of
  // arguments. Arguments are Object* type. After function returns,
  // pointers in 'args' might be invalid.
  //
  // *pending_exception tells whether the invoke resulted in
  // a pending exception.
  //
  static Handle<Object> New(Handle<JSFunction> func,
                            int argc,
                            Object*** args,
                            bool* pending_exception);

  // Call a function, just like Call(), but make sure to silently catch
  // any thrown exceptions. The return value is either the result of
  // calling the function (if caught exception is false) or the exception
  // that occurred (if caught exception is true).
  static Handle<Object> TryCall(Handle<JSFunction> func,
                                Handle<Object> receiver,
                                int argc,
                                Object*** args,
                                bool* caught_exception);

  // ECMA-262 9.2
  static Handle<Object> ToBoolean(Handle<Object> obj);

  // ECMA-262 9.3
  static Handle<Object> ToNumber(Handle<Object> obj, bool* exc);

  // ECMA-262 9.4
  static Handle<Object> ToInteger(Handle<Object> obj, bool* exc);

  // ECMA-262 9.5
  static Handle<Object> ToInt32(Handle<Object> obj, bool* exc);

  // ECMA-262 9.6
  static Handle<Object> ToUint32(Handle<Object> obj, bool* exc);

  // ECMA-262 9.8
  static Handle<Object> ToString(Handle<Object> obj, bool* exc);

  // ECMA-262 9.8
  static Handle<Object> ToDetailString(Handle<Object> obj, bool* exc);

  // ECMA-262 9.9
  static Handle<Object> ToObject(Handle<Object> obj, bool* exc);

  // Create a new date object from 'time'.
  static Handle<Object> NewDate(double time, bool* exc);

  // Used to implement [] notation on strings (calls JS code)
  static Handle<Object> CharAt(Handle<String> str, uint32_t index);

  static Handle<Object> GetFunctionFor();
  static Handle<JSFunction> InstantiateFunction(
      Handle<FunctionTemplateInfo> data, bool* exc);
  static Handle<JSObject> InstantiateObject(Handle<ObjectTemplateInfo> data,
                                            bool* exc);
  static void ConfigureInstance(Handle<Object> instance,
                                Handle<Object> data,
                                bool* exc);
  static Handle<String> GetStackTraceLine(Handle<Object> recv,
                                          Handle<JSFunction> fun,
                                          Handle<Object> pos,
                                          Handle<Object> is_global);

  static Object* DebugBreakHelper();

  // If the stack guard is triggered, but it is not an actual
  // stack overflow, then handle the interruption accordingly.
  static Object* HandleStackGuardInterrupt();

  // Get a function delegate (or undefined) for the given non-function
  // object. Used for support calling objects as functions.
  static Handle<Object> GetFunctionDelegate(Handle<Object> object);
};


class ExecutionAccess;


// Stack guards are used to limit the number of nested invocations of
// JavaScript and the stack size used in each invocation.
class StackGuard BASE_EMBEDDED {
 public:
  StackGuard();

  ~StackGuard();

  static void SetStackLimit(uintptr_t limit);

  static Address address_of_jslimit() {
    return reinterpret_cast<Address>(&thread_local_.jslimit_);
  }

  // Threading support.
  static char* ArchiveStackGuard(char* to);
  static char* RestoreStackGuard(char* from);
  static int ArchiveSpacePerThread();

  static bool IsStackOverflow();
  static bool IsPreempted();
  static void Preempt();
  static bool IsInterrupted();
  static void Interrupt();
  static bool IsDebugBreak();
  static void DebugBreak();
  static void Continue(InterruptFlag after_what);

 private:
  // You should hold the ExecutionAccess lock when calling this method.
  static bool IsSet(const ExecutionAccess& lock);

  // This provides an asynchronous read of the stack limit for the current
  // thread.  There are no locks protecting this, but it is assumed that you
  // have the global V8 lock if you are using multiple V8 threads.
  static uintptr_t climit() {
    return thread_local_.climit_;
  }

  // You should hold the ExecutionAccess lock when calling this method.
  static void set_limits(uintptr_t value, const ExecutionAccess& lock) {
    thread_local_.jslimit_ = value;
    thread_local_.climit_ = value;
  }

  // Reset limits to initial values. For example after handling interrupt.
  // You should hold the ExecutionAccess lock when calling this method.
  static void reset_limits(const ExecutionAccess& lock) {
    if (thread_local_.nesting_ == 0) {
      // No limits have been set yet.
      set_limits(kIllegalLimit, lock);
    } else {
      thread_local_.jslimit_ = thread_local_.initial_jslimit_;
      thread_local_.climit_ = thread_local_.initial_climit_;
    }
  }

  // Enable or disable interrupts.
  static void EnableInterrupts();
  static void DisableInterrupts();

  static const uintptr_t kLimitSize = 512 * KB;
  static const uintptr_t kInterruptLimit = 0xfffffffe;
  static const uintptr_t kIllegalLimit = 0xffffffff;

  class ThreadLocal {
   public:
    ThreadLocal()
     : initial_jslimit_(kIllegalLimit),
       jslimit_(kIllegalLimit),
       initial_climit_(kIllegalLimit),
       climit_(kIllegalLimit),
       nesting_(0),
       postpone_interrupts_nesting_(0),
       interrupt_flags_(0) {}
    uintptr_t initial_jslimit_;
    uintptr_t jslimit_;
    uintptr_t initial_climit_;
    uintptr_t climit_;
    int nesting_;
    int postpone_interrupts_nesting_;
    int interrupt_flags_;
  };

  static ThreadLocal thread_local_;

  friend class StackLimitCheck;
  friend class PostponeInterruptsScope;
};


// Support for checking for stack-overflows in C++ code.
class StackLimitCheck BASE_EMBEDDED {
 public:
  bool HasOverflowed() const {
    // Stack has overflowed in C++ code only if stack pointer exceeds the C++
    // stack guard and the limits are not set to interrupt values.
    // TODO(214): Stack overflows are ignored if a interrupt is pending. This
    // code should probably always use the initial C++ limit.
    return (reinterpret_cast<uintptr_t>(this) < StackGuard::climit()) &&
           StackGuard::IsStackOverflow();
  }
};


// Support for temporarily postponing interrupts. When the outermost
// postpone scope is left the interrupts will be re-enabled and any
// interrupts that occurred while in the scope will be taken into
// account.
class PostponeInterruptsScope BASE_EMBEDDED {
 public:
  PostponeInterruptsScope() {
    StackGuard::thread_local_.postpone_interrupts_nesting_++;
    StackGuard::DisableInterrupts();
  }

  ~PostponeInterruptsScope() {
    if (--StackGuard::thread_local_.postpone_interrupts_nesting_ == 0) {
      StackGuard::EnableInterrupts();
    }
  }
};


class GCExtension : public v8::Extension {
 public:
  GCExtension() : v8::Extension("v8/gc", kSource) {}
  virtual v8::Handle<v8::FunctionTemplate> GetNativeFunction(
      v8::Handle<v8::String> name);
  static v8::Handle<v8::Value> GC(const v8::Arguments& args);
 private:
  static const char* kSource;
};


} }  // namespace v8::internal

#endif  // V8_EXECUTION_H_