Fix source property of empty RegExp objects.

src/runtime.cc

 // Copyright 2012 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 1762 matching lines @@
   array->InObjectPropertyAtPut(JSRegExpResult::kInputIndex, args[2]);
   return array;
 }
 
 
 RUNTIME_FUNCTION(MaybeObject*, Runtime_RegExpInitializeObject) {
   AssertNoAllocation no_alloc;
   ASSERT(args.length() == 5);
   CONVERT_ARG_CHECKED(JSRegExp, regexp, 0);
   CONVERT_ARG_CHECKED(String, source, 1);
+  // If source is the empty string we set it to "(?:)" instead as
+  // suggested by ECMA-262, 5th, section 15.10.4.1.
+  if (source->length() == 0) source = isolate->heap()->query_colon_symbol();
 
   Object* global = args[2];
   if (!global->IsTrue()) global = isolate->heap()->false_value();
 
   Object* ignoreCase = args[3];
   if (!ignoreCase->IsTrue()) ignoreCase = isolate->heap()->false_value();
 
   Object* multiline = args[4];
   if (!multiline->IsTrue()) multiline = isolate->heap()->false_value();
 
@@ skipping 11603 matching lines @@
     // Handle last resort GC and make sure to allow future allocations
     // to grow the heap without causing GCs (if possible).
     isolate->counters()->gc_last_resort_from_js()->Increment();
     isolate->heap()->CollectAllGarbage(Heap::kNoGCFlags,
                                        "Runtime::PerformGC");
   }
 }
 
 
 } }  // namespace v8::internal