A MessageObject is a purely internal object to hold information about

src/messages.js

 // 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
@@ skipping 37 matching lines @@
 // If this object gets passed to an error constructor the error will
 // get an accessor for .message that constructs a descriptive error
 // message on access.
 var kAddMessageAccessorsMarker = { };
 
 var kMessages = 0;
 
 var kReplacementMarkers =
     [ "%0", "%1", "%2", "%3" ]
 
-function FormatString(format, args) {
+function FormatString(format, message) {
+  var args = %MessageGetArguments(message);
   var result = "";
   var arg_num = 0;
   for (var i = 0; i < format.length; i++) {
     var str = format[i];
     for (arg_num = 0; arg_num < kReplacementMarkers.length; arg_num++) {
       if (format[i] !== kReplacementMarkers[arg_num]) continue;
       try {
         str = ToDetailString(args[arg_num]);
       } catch (e) {
         str = "#<error>";
@@ skipping 151 matching lines @@
       strict_function_name:         ["Function name may not be eval or arguments in strict mode"],
       strict_octal_literal:         ["Octal literals are not allowed in strict mode."],
       strict_duplicate_property:    ["Duplicate data property in object literal not allowed in strict mode"],
       accessor_data_property:       ["Object literal may not have data and accessor property with the same name"],
       accessor_get_set:             ["Object literal may not have multiple get/set accessors with the same name"],
       strict_lhs_assignment:        ["Assignment to eval or arguments is not allowed in strict mode"],
       strict_lhs_postfix:           ["Postfix increment/decrement may not have eval or arguments operand in strict mode"],
       strict_lhs_prefix:            ["Prefix increment/decrement may not have eval or arguments operand in strict mode"],
     };
   }
-  var format = kMessages[message.type];
-  if (!format) return "<unknown message " + message.type + ">";
-  return FormatString(format, message.args);
+  var message_type = %MessageGetType(message);
+  var format = kMessages[message_type];
+  if (!format) return "<unknown message " + message_type + ">";
+  return FormatString(format, message);
 }
 
 
 function GetLineNumber(message) {
-  if (message.startPos == -1) return kNoLineNumberInfo;
-  var location = message.script.locationFromPosition(message.startPos, true);
+  var start_position = %MessageGetStartPosition(message);
+  if (start_position == -1) return kNoLineNumberInfo;
+  var script = %MessageGetScript(message);
+  var location = script.locationFromPosition(start_position, true);
   if (location == null) return kNoLineNumberInfo;
   return location.line + 1;
 }
 
 
 // Returns the source code line containing the given source
 // position, or the empty string if the position is invalid.
 function GetSourceLine(message) {
-  var location = message.script.locationFromPosition(message.startPos, true);
+  var script = %MessageGetScript(message);
+  var start_position = %MessageGetStartPosition(message);
+  var location = script.locationFromPosition(start_position, true);
   if (location == null) return "";
   location.restrict();
   return location.sourceText();
 }
 
 
 function MakeTypeError(type, args) {
   return MakeGenericError($TypeError, type, args);
 }
 
@@ skipping 358 matching lines @@
   return %_CallFunction(this.script.source,
                         this.from_position,
                         this.to_position,
                         StringSubstring);
 };
 
 
 // Returns the offset of the given position within the containing
 // line.
 function GetPositionInLine(message) {
-  var location = message.script.locationFromPosition(message.startPos, false);
+  var script = %MessageGetScript(message);
+  var start_position = %MessageGetStartPosition(message);
+  var location = script.locationFromPosition(start_position, false);
   if (location == null) return -1;
   location.restrict();
-  return message.startPos - location.start;
+  return start_position - location.start;
 }
 
 
-function ErrorMessage(type, args, startPos, endPos, script, stackTrace,
-                      stackFrames) {
-  this.startPos = startPos;
-  this.endPos = endPos;
-  this.type = type;
-  this.args = args;
-  this.script = script;
-  this.stackTrace = stackTrace;
-  this.stackFrames = stackFrames;
-}
-
-
-function MakeMessage(type, args, startPos, endPos, script, stackTrace,
-                     stackFrames) {
-  return new ErrorMessage(type, args, startPos, endPos, script, stackTrace,
-                          stackFrames);
-}
-
-
 function GetStackTraceLine(recv, fun, pos, isGlobal) {
   return FormatSourcePosition(new CallSite(recv, fun, pos));
 }
 
 // ----------------------------------------------------------------------------
 // Error implementation
 
 // Defines accessors for a property that is calculated the first time
 // the property is read.
 function DefineOneShotAccessor(obj, name, fun) {
@@ skipping 323 matching lines @@
       // Define all the expected properties directly on the error
       // object. This avoids going through getters and setters defined
       // on prototype objects.
       %IgnoreAttributesAndSetProperty(this, 'stack', void 0);
       %IgnoreAttributesAndSetProperty(this, 'arguments', void 0);
       %IgnoreAttributesAndSetProperty(this, 'type', void 0);
       if (m === kAddMessageAccessorsMarker) {
         // DefineOneShotAccessor always inserts a message property and
         // ignores setters.
         DefineOneShotAccessor(this, 'message', function (obj) {
-          return FormatMessage({type: obj.type, args: obj.arguments});
+            return FormatMessage(%NewMessageObject(obj.type, obj.arguments));
         });
       } else if (!IS_UNDEFINED(m)) {
         %IgnoreAttributesAndSetProperty(this, 'message', ToString(m));
       }
       captureStackTrace(this, f);
     } else {
       return new f(m);
     }
   });
 }
 
 function captureStackTrace(obj, cons_opt) {
   var stackTraceLimit = $Error.stackTraceLimit;
-  if (!stackTraceLimit) return;
+  if (!stackTraceLimit || !IS_NUMBER(stackTraceLimit)) return;
   if (stackTraceLimit < 0 || stackTraceLimit > 10000)
     stackTraceLimit = 10000;
-  var raw_stack = %CollectStackTrace(cons_opt ? cons_opt : captureStackTrace,
-      stackTraceLimit);
+  var raw_stack = %CollectStackTrace(cons_opt
+                                     ? cons_opt
+                                     : captureStackTrace, stackTraceLimit);
   DefineOneShotAccessor(obj, 'stack', function (obj) {
     return FormatRawStackTrace(obj, raw_stack);
   });
 };
 
 $Math.__proto__ = global.Object.prototype;
 
 DefineError(function Error() { });
 DefineError(function TypeError() { });
 DefineError(function RangeError() { });
@@ skipping 10 matching lines @@
 // Global list of error objects visited during errorToString. This is
 // used to detect cycles in error toString formatting.
 var visited_errors = new $Array();
 var cyclic_error_marker = new $Object();
 
 function errorToStringDetectCycle() {
   if (!%PushIfAbsent(visited_errors, this)) throw cyclic_error_marker;
   try {
     var type = this.type;
     if (type && !%_CallFunction(this, "message", ObjectHasOwnProperty)) {
-      var formatted = FormatMessage({ type: type, args: this.arguments });
+      var formatted = FormatMessage(%NewMessageObject(type, this.arguments));
       return this.name + ": " + formatted;
     }
     var message = %_CallFunction(this, "message", ObjectHasOwnProperty)
         ? (": " + this.message)
         : "";
     return this.name + message;
   } finally {
     visited_errors.length = visited_errors.length - 1;
   }
 }
@@ skipping 12 matching lines @@
     else throw e;
   }
 }
 
 %FunctionSetName(errorToString, 'toString');
 %SetProperty($Error.prototype, 'toString', errorToString, DONT_ENUM);
 
 // Boilerplate for exceptions for stack overflows. Used from
 // Top::StackOverflow().
 const kStackOverflowBoilerplate = MakeRangeError('stack_overflow', []);