Rewrite Error.prototype.toString in C++.

src/messages.h

 // Copyright 2006-2008 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.
 
 // The infrastructure used for (localized) message reporting in V8.
 //
 // Note: there's a big unresolved issue about ownership of the data
 // structures used by this framework.
 
 #ifndef V8_MESSAGES_H_
@@ skipping 439 matching lines @@
   // Report a formatted message (needs JS allocation).
   static void ReportMessage(Isolate* isolate, MessageLocation* loc,
                             Handle<JSMessageObject> message);
 
   static void DefaultMessageReport(Isolate* isolate, const MessageLocation* loc,
                                    Handle<Object> message_obj);
   static Handle<String> GetMessage(Isolate* isolate, Handle<Object> data);
   static base::SmartArrayPointer<char> GetLocalizedMessage(Isolate* isolate,
                                                            Handle<Object> data);
 };
+
+
+class ErrorToStringHelper {
+ public:
+  ErrorToStringHelper() : visited_(0) {}
+
+  MUST_USE_RESULT MaybeHandle<String> Stringify(Isolate* isolate,
+                                                Handle<JSObject> error);
+
+ private:
+  class VisitedScope {
+   public:
+    VisitedScope(ErrorToStringHelper* helper, Handle<JSObject> error)
+        : helper_(helper), has_visited_(false) {
+      for (const auto& visited : helper->visited_) {

[Jakob Kummerow, 2015/08/08 21:56:09]

nit: I'd prefer the explicitness of s/auto/Handle<JSObject>/

+        if (visited.is_identical_to(error)) {
+          has_visited_ = true;
+          break;
+        }
+      }
+      helper->visited_.Add(error);
+    }
+    ~VisitedScope() { helper_->visited_.RemoveLast(); }
+    bool HasVisited() { return has_visited_; }

[Jakob Kummerow, 2015/08/08 21:56:09]

nit: unix_hacker_style() for simple getters

+
+   private:
+    ErrorToStringHelper* helper_;
+    bool has_visited_;
+  };
+
+

[Jakob Kummerow, 2015/08/08 21:56:09]

nit: one empty line is enough here

+  bool ShadowsInternalError(Isolate* isolate, LookupIterator* property_lookup,

[Jakob Kummerow, 2015/08/08 21:56:09]

this could be declared static, right?

+                            LookupIterator* internal_error_lookup);
+
+  MUST_USE_RESULT MaybeHandle<String> GetStringifiedProperty(

[Jakob Kummerow, 2015/08/08 21:56:09]

this could be declared static too, right?

+      Isolate* isolate, LookupIterator* property_lookup,
+      Handle<String> default_value);
+
+  List<Handle<JSObject> > visited_;
+};
 } }  // namespace v8::internal
 
 #endif  // V8_MESSAGES_H_