Internalize strings in-place

src/runtime/runtime-regexp.cc

 // Copyright 2014 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/runtime/runtime-utils.h"
 
 #include "src/arguments.h"
 #include "src/conversions-inl.h"
 #include "src/isolate-inl.h"
 #include "src/messages.h"
@@ skipping 413 matching lines @@
                            static_cast<int64_t>(pattern_len)) *
                               static_cast<int64_t>(matches) +
                           static_cast<int64_t>(subject_len);
   int result_len;
   if (result_len_64 > static_cast<int64_t>(String::kMaxLength)) {
     STATIC_ASSERT(String::kMaxLength < kMaxInt);
     result_len = kMaxInt;  // Provoke exception.
   } else {
     result_len = static_cast<int>(result_len_64);
   }
+  if (result_len == 0) {
+    return isolate->heap()->empty_string();
+  }
 
   int subject_pos = 0;
   int result_pos = 0;
 
   MaybeHandle<SeqString> maybe_res;
   if (ResultSeqString::kHasOneByteEncoding) {
     maybe_res = isolate->factory()->NewRawOneByteString(result_len);
   } else {
     maybe_res = isolate->factory()->NewRawTwoByteString(result_len);
   }
@@ skipping 1234 matching lines @@
 
 RUNTIME_FUNCTION(Runtime_IsRegExp) {
   SealHandleScope shs(isolate);
   DCHECK_EQ(1, args.length());
   CONVERT_ARG_CHECKED(Object, obj, 0);
   return isolate->heap()->ToBoolean(obj->IsJSRegExp());
 }
 
 }  // namespace internal
 }  // namespace v8