Internalize strings in-place

src/runtime/runtime-i18n.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.
 
 
 #ifdef V8_I18N_SUPPORT
 #include "src/runtime/runtime-utils.h"
 
 #include <memory>
 
@@ skipping 930 matching lines @@
 namespace {
 MUST_USE_RESULT Object* LocaleConvertCase(Handle<String> s, Isolate* isolate,
                                           bool is_to_upper, const char* lang) {
   auto case_converter = is_to_upper ? u_strToUpper : u_strToLower;
   int32_t src_length = s->length();
   int32_t dest_length = src_length;
   UErrorCode status;
   Handle<SeqTwoByteString> result;
   std::unique_ptr<uc16[]> sap;
 
+  if (dest_length == 0) return isolate->heap()->empty_string();
+
   // This is not a real loop. It'll be executed only once (no overflow) or
   // twice (overflow).
   for (int i = 0; i < 2; ++i) {
     // Case conversion can increase the string length (e.g. sharp-S => SS) so
     // that we have to handle RangeError exceptions here.
     ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
         isolate, result, isolate->factory()->NewRawTwoByteString(dest_length));
     DisallowHeapAllocation no_gc;
     String::FlatContent flat = s->GetFlatContent();
     const UChar* src = GetUCharBufferFromFlat(flat, &sap, src_length);
@@ skipping 191 matching lines @@
   DCHECK_EQ(args.length(), 1);
   CONVERT_ARG_HANDLE_CHECKED(String, s, 0);
 
   // This function could be optimized for no-op cases the way lowercase
   // counterpart is, but in empirical testing, few actual calls to upper()
   // are no-ops. So, it wouldn't be worth the extra time for pre-scanning.
 
   int32_t length = s->length();
   s = String::Flatten(s);
 
-  if (s->HasOnlyOneByteChars()) {
+  if (s->HasOnlyOneByteChars() && length > 0) {
     Handle<SeqOneByteString> result;
     ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
         isolate, result, isolate->factory()->NewRawOneByteString(length));
 
     int sharp_s_count;
     bool is_result_single_byte;
     {
       DisallowHeapAllocation no_gc;
       String::FlatContent flat = s->GetFlatContent();
       // If it was ok to slow down ASCII-only input slightly, ToUpperFastASCII
@@ skipping 74 matching lines @@
   Handle<FixedArray> date_cache_version =
       Handle<FixedArray>::cast(isolate->eternal_handles()->GetSingleton(
           EternalHandles::DATE_CACHE_VERSION));
   return date_cache_version->get(0);
 }
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_I18N_SUPPORT