Get rid of ZoneScope completely.

src/json-parser.h

 // Copyright 2011 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 25 matching lines @@
 #include "spaces-inl.h"
 #include "token.h"
 
 namespace v8 {
 namespace internal {
 
 // A simple json parser.
 template <bool seq_ascii>
 class JsonParser BASE_EMBEDDED {
  public:
-  static Handle<Object> Parse(Handle<String> source, Zone* zone) {
-    return JsonParser().ParseJson(source, zone);
+  static Handle<Object> Parse(Handle<String> source) {
+    return JsonParser(source).ParseJson();
   }
 
   static const int kEndOfString = -1;
 
  private:
+  explicit JsonParser(Handle<String> source)
+      : source_(source),
+        source_length_(source->length()),
+        isolate_(source->map()->GetHeap()->isolate()),
+        factory_(isolate_->factory()),
+        zone_(isolate_),
+        object_constructor_(isolate_->native_context()->object_function(),
+                            isolate_),
+        position_(-1) {
+    FlattenString(source_);
+    pretenure_ = (source_length_ >= kPretenureTreshold) ? TENURED : NOT_TENURED;
+
+    // Optimized fast case where we only have ASCII characters.
+    if (seq_ascii) {
+      seq_source_ = Handle<SeqOneByteString>::cast(source_);
+    }
+  }
+
   // Parse a string containing a single JSON value.
-  Handle<Object> ParseJson(Handle<String> source, Zone* zone);
+  Handle<Object> ParseJson();
 
   inline void Advance() {
     position_++;
     if (position_ >= source_length_) {
       c0_ = kEndOfString;
     } else if (seq_ascii) {
       c0_ = seq_source_->SeqOneByteStringGet(position_);
     } else {
       c0_ = source_->Get(position_);
     }
@@ skipping 107 matching lines @@
 
   // Mark that a parsing error has happened at the current token, and
   // return a null handle. Primarily for readability.
   inline Handle<Object> ReportUnexpectedCharacter() {
     return Handle<Object>::null();
   }
 
   inline Isolate* isolate() { return isolate_; }
   inline Factory* factory() { return factory_; }
   inline Handle<JSFunction> object_constructor() { return object_constructor_; }
-  inline Zone* zone() const { return zone_; }
 
   static const int kInitialSpecialStringLength = 1024;
   static const int kPretenureTreshold = 100 * 1024;
 
 
  private:
   Handle<String> source_;
   int source_length_;
   Handle<SeqOneByteString> seq_source_;
 
   PretenureFlag pretenure_;
   Isolate* isolate_;
   Factory* factory_;
+  Zone zone_;
   Handle<JSFunction> object_constructor_;
   uc32 c0_;
   int position_;
-  Zone* zone_;
 };
 
 template <bool seq_ascii>
-Handle<Object> JsonParser<seq_ascii>::ParseJson(Handle<String> source,
-                                                Zone* zone) {
-  isolate_ = source->map()->GetHeap()->isolate();
-  factory_ = isolate_->factory();
-  object_constructor_ = Handle<JSFunction>(
-      isolate()->native_context()->object_function(), isolate());
-  zone_ = zone;
-  FlattenString(source);
-  source_ = source;
-  source_length_ = source_->length();
-  pretenure_ = (source_length_ >= kPretenureTreshold) ? TENURED : NOT_TENURED;
-
-  // Optimized fast case where we only have ASCII characters.
-  if (seq_ascii) {
-    seq_source_ = Handle<SeqOneByteString>::cast(source_);
-  }
-
-  // Set initial position right before the string.
-  position_ = -1;
+Handle<Object> JsonParser<seq_ascii>::ParseJson() {
   // Advance to the first character (possibly EOS)
   AdvanceSkipWhitespace();
   Handle<Object> result = ParseJsonValue();
   if (result.is_null() || c0_ != kEndOfString) {
     // Some exception (for example stack overflow) is already pending.
     if (isolate_->has_pending_exception()) return Handle<Object>::null();
 
     // Parse failed. Current character is the unexpected token.
     const char* message;
     Factory* factory = this->factory();
@@ skipping 25 matching lines @@
       default:
         message = "unexpected_token";
         Handle<Object> name =
             LookupSingleCharacterStringFromCode(isolate_, c0_);
         Handle<FixedArray> element = factory->NewFixedArray(1);
         element->set(0, *name);
         array = factory->NewJSArrayWithElements(element);
         break;
     }
 
-    MessageLocation location(factory->NewScript(source),
+    MessageLocation location(factory->NewScript(source_),
                              position_,
                              position_ + 1);
     Handle<Object> result = factory->NewSyntaxError(message, array);
     isolate()->Throw(*result, &location);
     return Handle<Object>::null();
   }
   return result;
 }
 
 
@@ skipping 38 matching lines @@
 }
 
 
 // Parse a JSON object. Position must be right at '{'.
 template <bool seq_ascii>
 Handle<Object> JsonParser<seq_ascii>::ParseJsonObject() {
   HandleScope scope(isolate());
   Handle<JSObject> json_object =
       factory()->NewJSObject(object_constructor(), pretenure_);
   Handle<Map> map(json_object->map());
-  ZoneScope zone_scope(zone());
-  ZoneList<Handle<Object> > properties(8, zone());
+  ZoneList<Handle<Object> > properties(8, &zone_);

[danno, 2013/06/26 13:06:58]

here an else where, does it make sense to wrap zone_ in a simple accessor
function zone()?

[Benedikt Meurer, 2013/06/26 13:34:39]

Done.

   ASSERT_EQ(c0_, '{');
 
   bool transitioning = true;
 
   AdvanceSkipWhitespace();
   if (c0_ != '}') {
     do {
       if (c0_ != '"') return ReportUnexpectedCharacter();
 
       int start_position = position_;
@@ skipping 75 matching lines @@
 
           if (value->FitsRepresentation(expected_representation)) {
             // If the target representation is double and the value is already
             // double, use the existing box.
             if (FLAG_track_double_fields &&
                 value->IsSmi() &&
                 expected_representation.IsDouble()) {
               value = factory()->NewHeapNumber(
                   Handle<Smi>::cast(value)->value());
             }
-            properties.Add(value, zone());
+            properties.Add(value, &zone_);
             map = target;
             continue;
           } else {
             transitioning = false;
           }
         }
 
         // Commit the intermediate state to the object and stop transitioning.
         JSObject::AllocateStorageForMap(json_object, map);
         int length = properties.length();
@@ skipping 28 matching lines @@
     }
   }
   AdvanceSkipWhitespace();
   return scope.CloseAndEscape(json_object);
 }
 
 // Parse a JSON array. Position must be right at '['.
 template <bool seq_ascii>
 Handle<Object> JsonParser<seq_ascii>::ParseJsonArray() {
   HandleScope scope(isolate());
-  ZoneScope zone_scope(zone());
-  ZoneList<Handle<Object> > elements(4, zone());
+  ZoneList<Handle<Object> > elements(4, &zone_);
   ASSERT_EQ(c0_, '[');
 
   AdvanceSkipWhitespace();
   if (c0_ != ']') {
     do {
       Handle<Object> element = ParseJsonValue();
       if (element.is_null()) return ReportUnexpectedCharacter();
-      elements.Add(element, zone());
+      elements.Add(element, &zone_);
     } while (MatchSkipWhiteSpace(','));
     if (c0_ != ']') {
       return ReportUnexpectedCharacter();
     }
   }
   AdvanceSkipWhitespace();
   // Allocate a fixed array with all the elements.
   Handle<FixedArray> fast_elements =
       factory()->NewFixedArray(elements.length(), pretenure_);
   for (int i = 0, n = elements.length(); i < n; i++) {
@@ skipping 309 matching lines @@
 
   ASSERT_EQ('"', c0_);
   // Advance past the last '"'.
   AdvanceSkipWhitespace();
   return result;
 }
 
 } }  // namespace v8::internal
 
 #endif  // V8_JSON_PARSER_H_