Rewrite Object.prototype.toString in C++

src/objects.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/objects.h"
 
 #include <cmath>
 #include <iomanip>
 #include <sstream>
 
@@ skipping 16166 matching lines @@
       }
       break;
     }
   }
 
   DCHECK(!storage || storage->length() == counter);
   return counter;
 }
 
 
+MaybeHandle<String> JSObject::ObjectProtoToString(Isolate* isolate,
+                                                  Handle<Object> object) {
+  if (object->IsUndefined()) return isolate->factory()->undefined_to_string();
+  if (object->IsNull()) return isolate->factory()->null_to_string();
+
+  Handle<JSReceiver> receiver;
+  CHECK(Object::ToObject(isolate, object).ToHandle(&receiver));
+
+  Handle<String> tag;
+  if (FLAG_harmony_tostring) {
+    Handle<Object> to_string_tag;
+    ASSIGN_RETURN_ON_EXCEPTION(
+        isolate, to_string_tag,
+        GetProperty(receiver, isolate->factory()->to_string_tag_symbol()),
+        String);
+    if (to_string_tag->IsString()) {
+      tag = Handle<String>::cast(to_string_tag);
+    }
+  }
+
+  if (tag.is_null()) {
+    // TODO(adamk): class_name() is expensive, replace with instance type
+    // checks where possible.
+    tag = handle(receiver->class_name(), isolate);
+  }
+
+  IncrementalStringBuilder builder(isolate);
+  builder.AppendCString("[object ");
+  builder.AppendString(tag);
+  builder.AppendCharacter(']');
+  return builder.Finish();
+}
+
+
 const char* Symbol::PrivateSymbolToName() const {
   Heap* heap = GetIsolate()->heap();
 #define SYMBOL_CHECK_AND_PRINT(name) \
   if (this == heap->name()) return #name;
   PRIVATE_SYMBOL_LIST(SYMBOL_CHECK_AND_PRINT)
 #undef SYMBOL_CHECK_AND_PRINT
   return "UNKNOWN";
 }
 
 
@@ skipping 3028 matching lines @@
   if (cell->value() != *new_value) {
     cell->set_value(*new_value);
     Isolate* isolate = cell->GetIsolate();
     cell->dependent_code()->DeoptimizeDependentCodeGroup(
         isolate, DependentCode::kPropertyCellChangedGroup);
   }
 }
 
 }  // namespace internal
 }  // namespace v8