[regexp] fix zero-length matches for RegExp.prototype.@@split.

src/js/regexp.js

 // Copyright 2012 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.
 
 (function(global, utils) {
 
 %CheckIsBootstrapping();
 
 // -------------------------------------------------------------------
 // Imports
@@ skipping 278 matching lines @@
   var result = '/' + REGEXP_SOURCE(this) + '/';
   if (REGEXP_GLOBAL(this)) result += 'g';
   if (REGEXP_IGNORE_CASE(this)) result += 'i';
   if (REGEXP_MULTILINE(this)) result += 'm';
   if (REGEXP_UNICODE(this)) result += 'u';
   if (REGEXP_STICKY(this)) result += 'y';
   return result;
 }
 
 
+function AtSurrogatePair(subject, index) {
+  if (index + 1 >= subject.length) return false;
+  var first = %_StringCharCodeAt(subject, index);
+  if (first < 0xD800 || first > 0xDBFF) return false;
+  var second = %_StringCharCodeAt(subject, index + 1);
+  return second >= 0xDC00 || second <= 0xDFFF;
+}
+
+
 // ES6 21.2.5.11.
 function RegExpSplit(string, limit) {
   // TODO(yangguo): allow non-regexp receivers.
   if (!IS_REGEXP(this)) {
     throw MakeTypeError(kIncompatibleMethodReceiver,
                         "RegExp.prototype.@@split", this);
   }
   var separator = this;
   var subject = TO_STRING(string);
 
@@ skipping 21 matching lines @@
 
     var matchInfo = DoRegExpExec(separator, subject, startIndex);
     if (matchInfo === null || length === (startMatch = matchInfo[CAPTURE0])) {
       result[result.length] = %_SubString(subject, currentIndex, length);
       break;
     }
     var endIndex = matchInfo[CAPTURE1];
 
     // We ignore a zero-length match at the currentIndex.
     if (startIndex === endIndex && endIndex === currentIndex) {
-      startIndex++;
+      if (REGEXP_UNICODE(this) && AtSurrogatePair(subject, startIndex)) {
+        startIndex += 2;
+      } else {
+        startIndex++;
+      }
       continue;
     }
 
     result[result.length] = %_SubString(subject, currentIndex, startMatch);
 
     if (result.length === limit) break;
 
     var matchinfo_len = NUMBER_OF_CAPTURES(matchInfo) + REGEXP_FIRST_CAPTURE;
     for (var i = REGEXP_FIRST_CAPTURE + 2; i < matchinfo_len; ) {
       var start = matchInfo[i++];
@@ skipping 391 matching lines @@
 // Exports
 
 utils.Export(function(to) {
   to.RegExpExec = DoRegExpExec;
   to.RegExpExecNoTests = RegExpExecNoTests;
   to.RegExpLastMatchInfo = RegExpLastMatchInfo;
   to.RegExpTest = RegExpTest;
 });
 
 })