Merge 6168:6800 from bleeding_edge to experimental/gc branch.

include/v8.h

 // Copyright 2007-2009 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
@@ skipping 444 matching lines @@
     int level;
 
     inline void Initialize() {
       next = limit = NULL;
       level = 0;
     }
   };
 
   void Leave();
 
-
   internal::Object** prev_next_;
   internal::Object** prev_limit_;
 
   // Allow for the active closing of HandleScopes which allows to pass a handle
   // from the HandleScope being closed to the next top most HandleScope.
   bool is_closed_;
   internal::Object** RawClose(internal::Object** value);
 
   friend class ImplementationUtilities;
 };
@@ skipping 2032 matching lines @@
  *
  * Instances of this class can be passed to v8::V8::HeapStatistics to
  * get heap statistics from V8.
  */
 class V8EXPORT HeapStatistics {
  public:
   HeapStatistics();
   size_t total_heap_size() { return total_heap_size_; }
   size_t total_heap_size_executable() { return total_heap_size_executable_; }
   size_t used_heap_size() { return used_heap_size_; }
+  size_t heap_size_limit() { return heap_size_limit_; }
 
  private:
   void set_total_heap_size(size_t size) { total_heap_size_ = size; }
   void set_total_heap_size_executable(size_t size) {
     total_heap_size_executable_ = size;
   }
   void set_used_heap_size(size_t size) { used_heap_size_ = size; }
+  void set_heap_size_limit(size_t size) { heap_size_limit_ = size; }
 
   size_t total_heap_size_;
   size_t total_heap_size_executable_;
   size_t used_heap_size_;
+  size_t heap_size_limit_;
 
   friend class V8;
 };
 
 
 /**
  * Container class for static utility functions.
  */
 class V8EXPORT V8 {
  public:
@@ skipping 504 matching lines @@
   const char** names_;
 };
 
 
 /**
  * A sandboxed execution context with its own set of built-in objects
  * and functions.
  */
 class V8EXPORT Context {
  public:
-  /** Returns the global object of the context. */
+  /**
+   * Returns the global proxy object or global object itself for
+   * detached contexts.
+   *
+   * Global proxy object is a thin wrapper whose prototype points to
+   * actual context's global object with the properties like Object, etc.
+   * This is done that way for security reasons (for more details see
+   * https://wiki.mozilla.org/Gecko:SplitWindow).
+   *
+   * Please note that changes to global proxy object prototype most probably
+   * would break VM---v8 expects only global object as a prototype of
+   * global proxy object.
+   *
+   * If DetachGlobal() has been invoked, Global() would return actual global
+   * object until global is reattached with ReattachGlobal().
+   */
   Local<Object> Global();
 
   /**
    * Detaches the global object from its context before
    * the global object can be reused to create a new context.
    */
   void DetachGlobal();
 
   /**
    * Reattaches a global object to a context.  This can be used to
@@ skipping 279 matching lines @@
 // Tag information for HeapObject.
 const int kHeapObjectTag = 1;
 const int kHeapObjectTagSize = 2;
 const intptr_t kHeapObjectTagMask = (1 << kHeapObjectTagSize) - 1;
 
 // Tag information for Smi.
 const int kSmiTag = 0;
 const int kSmiTagSize = 1;
 const intptr_t kSmiTagMask = (1 << kSmiTagSize) - 1;
 
-template <size_t ptr_size> struct SmiConstants;
+template <size_t ptr_size> struct SmiTagging;
 
 // Smi constants for 32-bit systems.
-template <> struct SmiConstants<4> {
+template <> struct SmiTagging<4> {
   static const int kSmiShiftSize = 0;
   static const int kSmiValueSize = 31;
   static inline int SmiToInt(internal::Object* value) {
     int shift_bits = kSmiTagSize + kSmiShiftSize;
     // Throw away top 32 bits and shift down (requires >> to be sign extending).
     return static_cast<int>(reinterpret_cast<intptr_t>(value)) >> shift_bits;
   }
+
+  // For 32-bit systems any 2 bytes aligned pointer can be encoded as smi
+  // with a plain reinterpret_cast.
+  static const uintptr_t kEncodablePointerMask = 0x1;
+  static const int kPointerToSmiShift = 0;
 };
 
 // Smi constants for 64-bit systems.
-template <> struct SmiConstants<8> {
+template <> struct SmiTagging<8> {
   static const int kSmiShiftSize = 31;
   static const int kSmiValueSize = 32;
   static inline int SmiToInt(internal::Object* value) {
     int shift_bits = kSmiTagSize + kSmiShiftSize;
     // Shift down and throw away top 32 bits.
     return static_cast<int>(reinterpret_cast<intptr_t>(value) >> shift_bits);
   }
+
+  // To maximize the range of pointers that can be encoded
+  // in the available 32 bits, we require them to be 8 bytes aligned.
+  // This gives 2 ^ (32 + 3) = 32G address space covered.
+  // It might be not enough to cover stack allocated objects on some platforms.
+  static const int kPointerAlignment = 3;
+
+  static const uintptr_t kEncodablePointerMask =
+      ~(uintptr_t(0xffffffff) << kPointerAlignment);
+
+  static const int kPointerToSmiShift =
+      kSmiTagSize + kSmiShiftSize - kPointerAlignment;
 };
 
-const int kSmiShiftSize = SmiConstants<kApiPointerSize>::kSmiShiftSize;
-const int kSmiValueSize = SmiConstants<kApiPointerSize>::kSmiValueSize;
+typedef SmiTagging<kApiPointerSize> PlatformSmiTagging;
+const int kSmiShiftSize = PlatformSmiTagging::kSmiShiftSize;
+const int kSmiValueSize = PlatformSmiTagging::kSmiValueSize;
+const uintptr_t kEncodablePointerMask =
+    PlatformSmiTagging::kEncodablePointerMask;
+const int kPointerToSmiShift = PlatformSmiTagging::kPointerToSmiShift;
 
 template <size_t ptr_size> struct InternalConstants;
 
 // Internal constants for 32-bit systems.
 template <> struct InternalConstants<4> {
   static const int kStringResourceOffset = 3 * kApiPointerSize;
 };
 
 // Internal constants for 64-bit systems.
 template <> struct InternalConstants<8> {
@@ skipping 13 matching lines @@
   static const int kHeapObjectMapOffset = 0;
   static const int kMapInstanceTypeOffset = kApiPointerSize + kApiIntSize;
   static const int kStringResourceOffset =
       InternalConstants<kApiPointerSize>::kStringResourceOffset;
 
   static const int kProxyProxyOffset = kApiPointerSize;
   static const int kJSObjectHeaderSize = 3 * kApiPointerSize;
   static const int kFullStringRepresentationMask = 0x07;
   static const int kExternalTwoByteRepresentationTag = 0x02;
 
-  static const int kJSObjectType = 0x9f;
+  static const int kJSObjectType = 0xa0;
   static const int kFirstNonstringType = 0x80;
   static const int kProxyType = 0x85;
 
   static inline bool HasHeapObjectTag(internal::Object* value) {
     return ((reinterpret_cast<intptr_t>(value) & kHeapObjectTagMask) ==
             kHeapObjectTag);
   }
 
   static inline bool HasSmiTag(internal::Object* value) {
     return ((reinterpret_cast<intptr_t>(value) & kSmiTagMask) == kSmiTag);
   }
 
   static inline int SmiValue(internal::Object* value) {
-    return SmiConstants<kApiPointerSize>::SmiToInt(value);
+    return PlatformSmiTagging::SmiToInt(value);
   }
 
   static inline int GetInstanceType(internal::Object* obj) {
     typedef internal::Object O;
     O* map = ReadField<O*>(obj, kHeapObjectMapOffset);
     return ReadField<uint8_t>(map, kMapInstanceTypeOffset);
   }
 
+  static inline void* GetExternalPointerFromSmi(internal::Object* value) {
+    const uintptr_t address = reinterpret_cast<uintptr_t>(value);
+    return reinterpret_cast<void*>(address >> kPointerToSmiShift);
+  }
+
   static inline void* GetExternalPointer(internal::Object* obj) {
     if (HasSmiTag(obj)) {
-      return obj;
+      return GetExternalPointerFromSmi(obj);
     } else if (GetInstanceType(obj) == kProxyType) {
       return ReadField<void*>(obj, kProxyProxyOffset);
     } else {
       return NULL;
     }
   }
 
   static inline bool IsExternalTwoByteString(int instance_type) {
     int representation = (instance_type & kFullStringRepresentationMask);
     return representation == kExternalTwoByteRepresentationTag;
@@ skipping 346 matching lines @@
 
 
 }  // namespace v8
 
 
 #undef V8EXPORT
 #undef TYPE_CHECK
 
 
 #endif  // V8_H_