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 813 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;
     DCHECK(s->IsFlat());
     String::FlatContent flat = s->GetFlatContent();
@@ skipping 190 matching lines @@
     for (int index = index_to_first_unprocessed; index < length; ++index) {
       dest[index] = ToLatin1Lower(static_cast<uint16_t>(src[index]));
     }
   }
 
   return *result;
 }
 
 MUST_USE_RESULT Object* ConvertToUpper(Handle<String> s, Isolate* isolate) {
   int32_t length = s->length();
-  if (s->HasOnlyOneByteChars()) {
+  if (s->HasOnlyOneByteChars() && length > 0) {
     Handle<SeqOneByteString> result =
         isolate->factory()->NewRawOneByteString(length).ToHandleChecked();
 
     DCHECK(s->IsFlat());
     int sharp_s_count;
     bool is_result_single_byte;
     {
       DisallowHeapAllocation no_gc;
       String::FlatContent flat = s->GetFlatContent();
       uint8_t* dest = result->GetChars();
@@ skipping 123 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