Replace kEmptyString wth OnceInit initialized string*

src/google/protobuf/compiler/cpp/cpp_string_field.cc

@@ -53,7 +53,7 @@ void SetStringVariables(const FieldDescriptor* descriptor,
   (*variables)["default_length"] =
       SimpleItoa(descriptor->default_value_string().length());
   (*variables)["default_variable"] = descriptor->default_value_string().empty()
-      ? "&::google::protobuf::internal::kEmptyString"
+      ? "&::google::protobuf::internal::GetEmptyString()"
       : "_default_" + FieldName(descriptor) + "_";
   (*variables)["pointer_type"] =
       descriptor->type() == FieldDescriptor::TYPE_BYTES ? "void" : "char";

src/google/protobuf/compiler/plugin.pb.cc

@@ -184,7 +184,7 @@ CodeGeneratorRequest::CodeGeneratorRequest(const CodeGeneratorRequest& from)
 
 void CodeGeneratorRequest::SharedCtor() {
   _cached_size_ = 0;
-  parameter_ = const_cast< ::std::string*>(&::google::protobuf::internal::kEmptyString);
+  parameter_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyString());
   ::memset(_has_bits_, 0, sizeof(_has_bits_));
 }
 
@@ -193,7 +193,7 @@ CodeGeneratorRequest::~CodeGeneratorRequest() {
 }
 
 void CodeGeneratorRequest::SharedDtor() {
-  if (parameter_ != &::google::protobuf::internal::kEmptyString) {
+  if (parameter_ != &::google::protobuf::internal::GetEmptyString()) {
     delete parameter_;
   }
   if (this != default_instance_) {
@@ -224,7 +224,7 @@ CodeGeneratorRequest* CodeGeneratorRequest::New() const {
 void CodeGeneratorRequest::Clear() {
   if (_has_bits_[1 / 32] & (0xffu << (1 % 32))) {
     if (has_parameter()) {
-      if (parameter_ != &::google::protobuf::internal::kEmptyString) {
+      if (parameter_ != &::google::protobuf::internal::GetEmptyString()) {
         parameter_->clear();
       }
     }
@@ -501,9 +501,9 @@ CodeGeneratorResponse_File::CodeGeneratorResponse_File(const CodeGeneratorRespon
 
 void CodeGeneratorResponse_File::SharedCtor() {
   _cached_size_ = 0;
-  name_ = const_cast< ::std::string*>(&::google::protobuf::internal::kEmptyString);
-  insertion_point_ = const_cast< ::std::string*>(&::google::protobuf::internal::kEmptyString);
-  content_ = const_cast< ::std::string*>(&::google::protobuf::internal::kEmptyString);
+  name_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyString());
+  insertion_point_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyString());
+  content_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyString());
   ::memset(_has_bits_, 0, sizeof(_has_bits_));
 }
 
@@ -512,13 +512,13 @@ CodeGeneratorResponse_File::~CodeGeneratorResponse_File() {
 }
 
 void CodeGeneratorResponse_File::SharedDtor() {
-  if (name_ != &::google::protobuf::internal::kEmptyString) {
+  if (name_ != &::google::protobuf::internal::GetEmptyString()) {
     delete name_;
   }
-  if (insertion_point_ != &::google::protobuf::internal::kEmptyString) {
+  if (insertion_point_ != &::google::protobuf::internal::GetEmptyString()) {
     delete insertion_point_;
   }
-  if (content_ != &::google::protobuf::internal::kEmptyString) {
+  if (content_ != &::google::protobuf::internal::GetEmptyString()) {
     delete content_;
   }
   if (this != default_instance_) {
@@ -549,17 +549,17 @@ CodeGeneratorResponse_File* CodeGeneratorResponse_File::New() const {
 void CodeGeneratorResponse_File::Clear() {
   if (_has_bits_[0 / 32] & (0xffu << (0 % 32))) {
     if (has_name()) {
-      if (name_ != &::google::protobuf::internal::kEmptyString) {
+      if (name_ != &::google::protobuf::internal::GetEmptyString()) {
         name_->clear();
       }
     }
     if (has_insertion_point()) {
-      if (insertion_point_ != &::google::protobuf::internal::kEmptyString) {
+      if (insertion_point_ != &::google::protobuf::internal::GetEmptyString()) {
         insertion_point_->clear();
       }
     }
     if (has_content()) {
-      if (content_ != &::google::protobuf::internal::kEmptyString) {
+      if (content_ != &::google::protobuf::internal::GetEmptyString()) {
         content_->clear();
       }
     }
@@ -839,7 +839,7 @@ CodeGeneratorResponse::CodeGeneratorResponse(const CodeGeneratorResponse& from)
 
 void CodeGeneratorResponse::SharedCtor() {
   _cached_size_ = 0;
-  error_ = const_cast< ::std::string*>(&::google::protobuf::internal::kEmptyString);
+  error_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyString());
   ::memset(_has_bits_, 0, sizeof(_has_bits_));
 }
 
@@ -848,7 +848,7 @@ CodeGeneratorResponse::~CodeGeneratorResponse() {
 }
 
 void CodeGeneratorResponse::SharedDtor() {
-  if (error_ != &::google::protobuf::internal::kEmptyString) {
+  if (error_ != &::google::protobuf::internal::GetEmptyString()) {
     delete error_;
   }
   if (this != default_instance_) {
@@ -879,7 +879,7 @@ CodeGeneratorResponse* CodeGeneratorResponse::New() const {
 void CodeGeneratorResponse::Clear() {
   if (_has_bits_[0 / 32] & (0xffu << (0 % 32))) {
     if (has_error()) {
-      if (error_ != &::google::protobuf::internal::kEmptyString) {
+      if (error_ != &::google::protobuf::internal::GetEmptyString()) {
         error_->clear();
       }
     }

src/google/protobuf/compiler/plugin.pb.h

@@ -438,7 +438,7 @@ inline void CodeGeneratorRequest::clear_has_parameter() {
   _has_bits_[0] &= ~0x00000002u;
 }
 inline void CodeGeneratorRequest::clear_parameter() {
-  if (parameter_ != &::google::protobuf::internal::kEmptyString) {
+  if (parameter_ != &::google::protobuf::internal::GetEmptyString()) {
     parameter_->clear();
   }
   clear_has_parameter();
@@ -448,44 +448,44 @@ inline const ::std::string& CodeGeneratorRequest::parameter() const {
 }
 inline void CodeGeneratorRequest::set_parameter(const ::std::string& value) {
   set_has_parameter();
-  if (parameter_ == &::google::protobuf::internal::kEmptyString) {
+  if (parameter_ == &::google::protobuf::internal::GetEmptyString()) {
     parameter_ = new ::std::string;
   }
   parameter_->assign(value);
 }
 inline void CodeGeneratorRequest::set_parameter(const char* value) {
   set_has_parameter();
-  if (parameter_ == &::google::protobuf::internal::kEmptyString) {
+  if (parameter_ == &::google::protobuf::internal::GetEmptyString()) {
     parameter_ = new ::std::string;
   }
   parameter_->assign(value);
 }
 inline void CodeGeneratorRequest::set_parameter(const char* value, size_t size) {
   set_has_parameter();
-  if (parameter_ == &::google::protobuf::internal::kEmptyString) {
+  if (parameter_ == &::google::protobuf::internal::GetEmptyString()) {
     parameter_ = new ::std::string;
   }
   parameter_->assign(reinterpret_cast<const char*>(value), size);
 }
 inline ::std::string* CodeGeneratorRequest::mutable_parameter() {
   set_has_parameter();
-  if (parameter_ == &::google::protobuf::internal::kEmptyString) {
+  if (parameter_ == &::google::protobuf::internal::GetEmptyString()) {
     parameter_ = new ::std::string;
   }
   return parameter_;
 }
 inline ::std::string* CodeGeneratorRequest::release_parameter() {
   clear_has_parameter();
-  if (parameter_ == &::google::protobuf::internal::kEmptyString) {
+  if (parameter_ == &::google::protobuf::internal::GetEmptyString()) {
     return NULL;
   } else {
     ::std::string* temp = parameter_;
-    parameter_ = const_cast< ::std::string*>(&::google::protobuf::internal::kEmptyString);
+    parameter_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyString());
     return temp;
   }
 }
 inline void CodeGeneratorRequest::set_allocated_parameter(::std::string* parameter) {
-  if (parameter_ != &::google::protobuf::internal::kEmptyString) {
+  if (parameter_ != &::google::protobuf::internal::GetEmptyString()) {
     delete parameter_;
   }
   if (parameter) {
@@ -493,7 +493,7 @@ inline void CodeGeneratorRequest::set_allocated_parameter(::std::string* paramet
     parameter_ = parameter;
   } else {
     clear_has_parameter();
-    parameter_ = const_cast< ::std::string*>(&::google::protobuf::internal::kEmptyString);
+    parameter_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyString());
   }
 }
 
@@ -537,7 +537,7 @@ inline void CodeGeneratorResponse_File::clear_has_name() {
   _has_bits_[0] &= ~0x00000001u;
 }
 inline void CodeGeneratorResponse_File::clear_name() {
-  if (name_ != &::google::protobuf::internal::kEmptyString) {
+  if (name_ != &::google::protobuf::internal::GetEmptyString()) {
     name_->clear();
   }
   clear_has_name();
@@ -547,44 +547,44 @@ inline const ::std::string& CodeGeneratorResponse_File::name() const {
 }
 inline void CodeGeneratorResponse_File::set_name(const ::std::string& value) {
   set_has_name();
-  if (name_ == &::google::protobuf::internal::kEmptyString) {
+  if (name_ == &::google::protobuf::internal::GetEmptyString()) {
     name_ = new ::std::string;
   }
   name_->assign(value);
 }
 inline void CodeGeneratorResponse_File::set_name(const char* value) {
   set_has_name();
-  if (name_ == &::google::protobuf::internal::kEmptyString) {
+  if (name_ == &::google::protobuf::internal::GetEmptyString()) {
     name_ = new ::std::string;
   }
   name_->assign(value);
 }
 inline void CodeGeneratorResponse_File::set_name(const char* value, size_t size) {
   set_has_name();
-  if (name_ == &::google::protobuf::internal::kEmptyString) {
+  if (name_ == &::google::protobuf::internal::GetEmptyString()) {
     name_ = new ::std::string;
   }
   name_->assign(reinterpret_cast<const char*>(value), size);
 }
 inline ::std::string* CodeGeneratorResponse_File::mutable_name() {
   set_has_name();
-  if (name_ == &::google::protobuf::internal::kEmptyString) {
+  if (name_ == &::google::protobuf::internal::GetEmptyString()) {
     name_ = new ::std::string;
   }
   return name_;
 }
 inline ::std::string* CodeGeneratorResponse_File::release_name() {
   clear_has_name();
-  if (name_ == &::google::protobuf::internal::kEmptyString) {
+  if (name_ == &::google::protobuf::internal::GetEmptyString()) {
     return NULL;
   } else {
     ::std::string* temp = name_;
-    name_ = const_cast< ::std::string*>(&::google::protobuf::internal::kEmptyString);
+    name_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyString());
     return temp;
   }
 }
 inline void CodeGeneratorResponse_File::set_allocated_name(::std::string* name) {
-  if (name_ != &::google::protobuf::internal::kEmptyString) {
+  if (name_ != &::google::protobuf::internal::GetEmptyString()) {
     delete name_;
   }
   if (name) {
@@ -592,7 +592,7 @@ inline void CodeGeneratorResponse_File::set_allocated_name(::std::string* name)
     name_ = name;
   } else {
     clear_has_name();
-    name_ = const_cast< ::std::string*>(&::google::protobuf::internal::kEmptyString);
+    name_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyString());
   }
 }
 
@@ -607,7 +607,7 @@ inline void CodeGeneratorResponse_File::clear_has_insertion_point() {
   _has_bits_[0] &= ~0x00000002u;
 }
 inline void CodeGeneratorResponse_File::clear_insertion_point() {
-  if (insertion_point_ != &::google::protobuf::internal::kEmptyString) {
+  if (insertion_point_ != &::google::protobuf::internal::GetEmptyString()) {
     insertion_point_->clear();
   }
   clear_has_insertion_point();
@@ -617,44 +617,44 @@ inline const ::std::string& CodeGeneratorResponse_File::insertion_point() const
 }
 inline void CodeGeneratorResponse_File::set_insertion_point(const ::std::string& value) {
   set_has_insertion_point();
-  if (insertion_point_ == &::google::protobuf::internal::kEmptyString) {
+  if (insertion_point_ == &::google::protobuf::internal::GetEmptyString()) {
     insertion_point_ = new ::std::string;
   }
   insertion_point_->assign(value);
 }
 inline void CodeGeneratorResponse_File::set_insertion_point(const char* value) {
   set_has_insertion_point();
-  if (insertion_point_ == &::google::protobuf::internal::kEmptyString) {
+  if (insertion_point_ == &::google::protobuf::internal::GetEmptyString()) {
     insertion_point_ = new ::std::string;
   }
   insertion_point_->assign(value);
 }
 inline void CodeGeneratorResponse_File::set_insertion_point(const char* value, size_t size) {
   set_has_insertion_point();
-  if (insertion_point_ == &::google::protobuf::internal::kEmptyString) {
+  if (insertion_point_ == &::google::protobuf::internal::GetEmptyString()) {
     insertion_point_ = new ::std::string;
   }
   insertion_point_->assign(reinterpret_cast<const char*>(value), size);
 }
 inline ::std::string* CodeGeneratorResponse_File::mutable_insertion_point() {
   set_has_insertion_point();
-  if (insertion_point_ == &::google::protobuf::internal::kEmptyString) {
+  if (insertion_point_ == &::google::protobuf::internal::GetEmptyString()) {
     insertion_point_ = new ::std::string;
   }
   return insertion_point_;
 }
 inline ::std::string* CodeGeneratorResponse_File::release_insertion_point() {
   clear_has_insertion_point();
-  if (insertion_point_ == &::google::protobuf::internal::kEmptyString) {
+  if (insertion_point_ == &::google::protobuf::internal::GetEmptyString()) {
     return NULL;
   } else {
     ::std::string* temp = insertion_point_;
-    insertion_point_ = const_cast< ::std::string*>(&::google::protobuf::internal::kEmptyString);
+    insertion_point_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyString());
     return temp;
   }
 }
 inline void CodeGeneratorResponse_File::set_allocated_insertion_point(::std::string* insertion_point) {
-  if (insertion_point_ != &::google::protobuf::internal::kEmptyString) {
+  if (insertion_point_ != &::google::protobuf::internal::GetEmptyString()) {
     delete insertion_point_;
   }
   if (insertion_point) {
@@ -662,7 +662,7 @@ inline void CodeGeneratorResponse_File::set_allocated_insertion_point(::std::str
     insertion_point_ = insertion_point;
   } else {
     clear_has_insertion_point();
-    insertion_point_ = const_cast< ::std::string*>(&::google::protobuf::internal::kEmptyString);
+    insertion_point_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyString());
   }
 }
 
@@ -677,7 +677,7 @@ inline void CodeGeneratorResponse_File::clear_has_content() {
   _has_bits_[0] &= ~0x00000004u;
 }
 inline void CodeGeneratorResponse_File::clear_content() {
-  if (content_ != &::google::protobuf::internal::kEmptyString) {
+  if (content_ != &::google::protobuf::internal::GetEmptyString()) {
     content_->clear();
   }
   clear_has_content();
@@ -687,44 +687,44 @@ inline const ::std::string& CodeGeneratorResponse_File::content() const {
 }
 inline void CodeGeneratorResponse_File::set_content(const ::std::string& value) {
   set_has_content();
-  if (content_ == &::google::protobuf::internal::kEmptyString) {
+  if (content_ == &::google::protobuf::internal::GetEmptyString()) {
     content_ = new ::std::string;
   }
   content_->assign(value);
 }
 inline void CodeGeneratorResponse_File::set_content(const char* value) {
   set_has_content();
-  if (content_ == &::google::protobuf::internal::kEmptyString) {
+  if (content_ == &::google::protobuf::internal::GetEmptyString()) {
     content_ = new ::std::string;
   }
   content_->assign(value);
 }
 inline void CodeGeneratorResponse_File::set_content(const char* value, size_t size) {
   set_has_content();
-  if (content_ == &::google::protobuf::internal::kEmptyString) {
+  if (content_ == &::google::protobuf::internal::GetEmptyString()) {
     content_ = new ::std::string;
   }
   content_->assign(reinterpret_cast<const char*>(value), size);
 }
 inline ::std::string* CodeGeneratorResponse_File::mutable_content() {
   set_has_content();
-  if (content_ == &::google::protobuf::internal::kEmptyString) {
+  if (content_ == &::google::protobuf::internal::GetEmptyString()) {
     content_ = new ::std::string;
   }
   return content_;
 }
 inline ::std::string* CodeGeneratorResponse_File::release_content() {
   clear_has_content();
-  if (content_ == &::google::protobuf::internal::kEmptyString) {
+  if (content_ == &::google::protobuf::internal::GetEmptyString()) {
     return NULL;
   } else {
     ::std::string* temp = content_;
-    content_ = const_cast< ::std::string*>(&::google::protobuf::internal::kEmptyString);
+    content_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyString());
     return temp;
   }
 }
 inline void CodeGeneratorResponse_File::set_allocated_content(::std::string* content) {
-  if (content_ != &::google::protobuf::internal::kEmptyString) {
+  if (content_ != &::google::protobuf::internal::GetEmptyString()) {
     delete content_;
   }
   if (content) {
@@ -732,7 +732,7 @@ inline void CodeGeneratorResponse_File::set_allocated_content(::std::string* con
     content_ = content;
   } else {
     clear_has_content();
-    content_ = const_cast< ::std::string*>(&::google::protobuf::internal::kEmptyString);
+    content_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyString());
   }
 }
 
@@ -751,7 +751,7 @@ inline void CodeGeneratorResponse::clear_has_error() {
   _has_bits_[0] &= ~0x00000001u;
 }
 inline void CodeGeneratorResponse::clear_error() {
-  if (error_ != &::google::protobuf::internal::kEmptyString) {
+  if (error_ != &::google::protobuf::internal::GetEmptyString()) {
     error_->clear();
   }
   clear_has_error();
@@ -761,44 +761,44 @@ inline const ::std::string& CodeGeneratorResponse::error() const {
 }
 inline void CodeGeneratorResponse::set_error(const ::std::string& value) {
   set_has_error();
-  if (error_ == &::google::protobuf::internal::kEmptyString) {
+  if (error_ == &::google::protobuf::internal::GetEmptyString()) {
     error_ = new ::std::string;
   }
   error_->assign(value);
 }
 inline void CodeGeneratorResponse::set_error(const char* value) {
   set_has_error();
-  if (error_ == &::google::protobuf::internal::kEmptyString) {
+  if (error_ == &::google::protobuf::internal::GetEmptyString()) {
     error_ = new ::std::string;
   }
   error_->assign(value);
 }
 inline void CodeGeneratorResponse::set_error(const char* value, size_t size) {
   set_has_error();
-  if (error_ == &::google::protobuf::internal::kEmptyString) {
+  if (error_ == &::google::protobuf::internal::GetEmptyString()) {
     error_ = new ::std::string;
   }
   error_->assign(reinterpret_cast<const char*>(value), size);
 }
 inline ::std::string* CodeGeneratorResponse::mutable_error() {
   set_has_error();
-  if (error_ == &::google::protobuf::internal::kEmptyString) {
+  if (error_ == &::google::protobuf::internal::GetEmptyString()) {
     error_ = new ::std::string;
   }
   return error_;
 }
 inline ::std::string* CodeGeneratorResponse::release_error() {
   clear_has_error();
-  if (error_ == &::google::protobuf::internal::kEmptyString) {
+  if (error_ == &::google::protobuf::internal::GetEmptyString()) {
     return NULL;
   } else {
     ::std::string* temp = error_;
-    error_ = const_cast< ::std::string*>(&::google::protobuf::internal::kEmptyString);
+    error_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyString());
     return temp;
   }
 }
 inline void CodeGeneratorResponse::set_allocated_error(::std::string* error) {
-  if (error_ != &::google::protobuf::internal::kEmptyString) {
+  if (error_ != &::google::protobuf::internal::GetEmptyString()) {
     delete error_;
   }
   if (error) {
@@ -806,7 +806,7 @@ inline void CodeGeneratorResponse::set_allocated_error(::std::string* error) {
     error_ = error;
   } else {
     clear_has_error();
-    error_ = const_cast< ::std::string*>(&::google::protobuf::internal::kEmptyString);
+    error_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyString());
   }
 }
 

src/google/protobuf/descriptor.cc

@@ -139,8 +139,6 @@ const int FieldDescriptor::kLastReservedNumber;
 
 namespace {
 
-const string kEmptyString;
-
 string ToCamelCase(const string& input) {
   bool capitalize_next = false;
   string result;
@@ -2757,7 +2755,7 @@ Symbol DescriptorBuilder::NewPlaceholder(const string& name,
     placeholder_name = tables_->AllocateString(
       placeholder_full_name->substr(dotpos + 1));
   } else {
-    placeholder_package = &kEmptyString;
+    placeholder_package = &::google::protobuf::internal::GetEmptyString();
     placeholder_name = placeholder_full_name;
   }
 
@@ -2843,7 +2841,7 @@ const FileDescriptor* DescriptorBuilder::NewPlaceholderFile(
   memset(placeholder, 0, sizeof(*placeholder));
 
   placeholder->name_ = tables_->AllocateString(name);
-  placeholder->package_ = &kEmptyString;
+  placeholder->package_ = &::google::protobuf::internal::GetEmptyString();
   placeholder->pool_ = pool_;
   placeholder->options_ = &FileOptions::default_instance();
   placeholder->tables_ = &FileDescriptorTables::kEmpty;
@@ -3485,7 +3483,7 @@ void DescriptorBuilder::BuildFieldOrExtension(const FieldDescriptorProto& proto,
           result->default_value_enum_ = NULL;
           break;
         case FieldDescriptor::CPPTYPE_STRING:
-          result->default_value_string_ = &kEmptyString;
+          result->default_value_string_ = &::google::protobuf::internal::GetEmptyString();
           break;
         case FieldDescriptor::CPPTYPE_MESSAGE:
           break;

src/google/protobuf/descriptor.pb.cc

@@ -962,8 +962,8 @@ FileDescriptorProto::FileDescriptorProto(const FileDescriptorProto& from)
 
 void FileDescriptorProto::SharedCtor() {
   _cached_size_ = 0;
-  name_ = const_cast< ::std::string*>(&::google::protobuf::internal::kEmptyString);
-  package_ = const_cast< ::std::string*>(&::google::protobuf::internal::kEmptyString);
+  name_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyString());
+  package_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyString());
   options_ = NULL;
   source_code_info_ = NULL;
   ::memset(_has_bits_, 0, sizeof(_has_bits_));
@@ -974,10 +974,10 @@ FileDescriptorProto::~FileDescriptorProto() {
 }
 
 void FileDescriptorProto::SharedDtor() {
-  if (name_ != &::google::protobuf::internal::kEmptyString) {
+  if (name_ != &::google::protobuf::internal::GetEmptyString()) {
     delete name_;
   }
-  if (package_ != &::google::protobuf::internal::kEmptyString) {
+  if (package_ != &::google::protobuf::internal::GetEmptyString()) {
     delete package_;
   }
   if (this != default_instance_) {
@@ -1010,12 +1010,12 @@ FileDescriptorProto* FileDescriptorProto::New() const {
 void FileDescriptorProto::Clear() {
   if (_has_bits_[0 / 32] & (0xffu << (0 % 32))) {
     if (has_name()) {
-      if (name_ != &::google::protobuf::internal::kEmptyString) {
+      if (name_ != &::google::protobuf::internal::GetEmptyString()) {
         name_->clear();
       }
     }
     if (has_package()) {
-      if (package_ != &::google::protobuf::internal::kEmptyString) {
+      if (package_ != &::google::protobuf::internal::GetEmptyString()) {
         package_->clear();
       }
     }
@@ -1902,7 +1902,7 @@ DescriptorProto::DescriptorProto(const DescriptorProto& from)
 
 void DescriptorProto::SharedCtor() {
   _cached_size_ = 0;
-  name_ = const_cast< ::std::string*>(&::google::protobuf::internal::kEmptyString);
+  name_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyString());
   options_ = NULL;
   ::memset(_has_bits_, 0, sizeof(_has_bits_));
 }
@@ -1912,7 +1912,7 @@ DescriptorProto::~DescriptorProto() {
 }
 
 void DescriptorProto::SharedDtor() {
-  if (name_ != &::google::protobuf::internal::kEmptyString) {
+  if (name_ != &::google::protobuf::internal::GetEmptyString()) {
     delete name_;
   }
   if (this != default_instance_) {
@@ -1944,7 +1944,7 @@ DescriptorProto* DescriptorProto::New() const {
 void DescriptorProto::Clear() {
   if (_has_bits_[0 / 32] & (0xffu << (0 % 32))) {
     if (has_name()) {
-      if (name_ != &::google::protobuf::internal::kEmptyString) {
+      if (name_ != &::google::protobuf::internal::GetEmptyString()) {
         name_->clear();
       }
     }
@@ -2464,13 +2464,13 @@ FieldDescriptorProto::FieldDescriptorProto(const FieldDescriptorProto& from)
 
 void FieldDescriptorProto::SharedCtor() {
   _cached_size_ = 0;
-  name_ = const_cast< ::std::string*>(&::google::protobuf::internal::kEmptyString);
+  name_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyString());
   number_ = 0;
   label_ = 1;
   type_ = 1;
-  type_name_ = const_cast< ::std::string*>(&::google::protobuf::internal::kEmptyString);
-  extendee_ = const_cast< ::std::string*>(&::google::protobuf::internal::kEmptyString);
-  default_value_ = const_cast< ::std::string*>(&::google::protobuf::internal::kEmptyString);
+  type_name_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyString());
+  extendee_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyString());
+  default_value_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyString());
   options_ = NULL;
   ::memset(_has_bits_, 0, sizeof(_has_bits_));
 }
@@ -2480,16 +2480,16 @@ FieldDescriptorProto::~FieldDescriptorProto() {
 }
 
 void FieldDescriptorProto::SharedDtor() {
-  if (name_ != &::google::protobuf::internal::kEmptyString) {
+  if (name_ != &::google::protobuf::internal::GetEmptyString()) {
     delete name_;
   }
-  if (type_name_ != &::google::protobuf::internal::kEmptyString) {
+  if (type_name_ != &::google::protobuf::internal::GetEmptyString()) {
     delete type_name_;
   }
-  if (extendee_ != &::google::protobuf::internal::kEmptyString) {
+  if (extendee_ != &::google::protobuf::internal::GetEmptyString()) {
     delete extendee_;
   }
-  if (default_value_ != &::google::protobuf::internal::kEmptyString) {
+  if (default_value_ != &::google::protobuf::internal::GetEmptyString()) {
     delete default_value_;
   }
   if (this != default_instance_) {
@@ -2521,7 +2521,7 @@ FieldDescriptorProto* FieldDescriptorProto::New() const {
 void FieldDescriptorProto::Clear() {
   if (_has_bits_[0 / 32] & (0xffu << (0 % 32))) {
     if (has_name()) {
-      if (name_ != &::google::protobuf::internal::kEmptyString) {
+      if (name_ != &::google::protobuf::internal::GetEmptyString()) {
         name_->clear();
       }
     }
@@ -2529,17 +2529,17 @@ void FieldDescriptorProto::Clear() {
     label_ = 1;
     type_ = 1;
     if (has_type_name()) {
-      if (type_name_ != &::google::protobuf::internal::kEmptyString) {
+      if (type_name_ != &::google::protobuf::internal::GetEmptyString()) {
         type_name_->clear();
       }
     }
     if (has_extendee()) {
-      if (extendee_ != &::google::protobuf::internal::kEmptyString) {
+      if (extendee_ != &::google::protobuf::internal::GetEmptyString()) {
         extendee_->clear();
       }
     }
     if (has_default_value()) {
-      if (default_value_ != &::google::protobuf::internal::kEmptyString) {
+      if (default_value_ != &::google::protobuf::internal::GetEmptyString()) {
         default_value_->clear();
       }
     }
@@ -3035,7 +3035,7 @@ EnumDescriptorProto::EnumDescriptorProto(const EnumDescriptorProto& from)
 
 void EnumDescriptorProto::SharedCtor() {
   _cached_size_ = 0;
-  name_ = const_cast< ::std::string*>(&::google::protobuf::internal::kEmptyString);
+  name_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyString());
   options_ = NULL;
   ::memset(_has_bits_, 0, sizeof(_has_bits_));
 }
@@ -3045,7 +3045,7 @@ EnumDescriptorProto::~EnumDescriptorProto() {
 }
 
 void EnumDescriptorProto::SharedDtor() {
-  if (name_ != &::google::protobuf::internal::kEmptyString) {
+  if (name_ != &::google::protobuf::internal::GetEmptyString()) {
     delete name_;
   }
   if (this != default_instance_) {
@@ -3077,7 +3077,7 @@ EnumDescriptorProto* EnumDescriptorProto::New() const {
 void EnumDescriptorProto::Clear() {
   if (_has_bits_[0 / 32] & (0xffu << (0 % 32))) {
     if (has_name()) {
-      if (name_ != &::google::protobuf::internal::kEmptyString) {
+      if (name_ != &::google::protobuf::internal::GetEmptyString()) {
         name_->clear();
       }
     }
@@ -3351,7 +3351,7 @@ EnumValueDescriptorProto::EnumValueDescriptorProto(const EnumValueDescriptorProt
 
 void EnumValueDescriptorProto::SharedCtor() {
   _cached_size_ = 0;
-  name_ = const_cast< ::std::string*>(&::google::protobuf::internal::kEmptyString);
+  name_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyString());
   number_ = 0;
   options_ = NULL;
   ::memset(_has_bits_, 0, sizeof(_has_bits_));
@@ -3362,7 +3362,7 @@ EnumValueDescriptorProto::~EnumValueDescriptorProto() {
 }
 
 void EnumValueDescriptorProto::SharedDtor() {
-  if (name_ != &::google::protobuf::internal::kEmptyString) {
+  if (name_ != &::google::protobuf::internal::GetEmptyString()) {
     delete name_;
   }
   if (this != default_instance_) {
@@ -3394,7 +3394,7 @@ EnumValueDescriptorProto* EnumValueDescriptorProto::New() const {
 void EnumValueDescriptorProto::Clear() {
   if (_has_bits_[0 / 32] & (0xffu << (0 % 32))) {
     if (has_name()) {
-      if (name_ != &::google::protobuf::internal::kEmptyString) {
+      if (name_ != &::google::protobuf::internal::GetEmptyString()) {
         name_->clear();
       }
     }
@@ -3664,7 +3664,7 @@ ServiceDescriptorProto::ServiceDescriptorProto(const ServiceDescriptorProto& fro
 
 void ServiceDescriptorProto::SharedCtor() {
   _cached_size_ = 0;
-  name_ = const_cast< ::std::string*>(&::google::protobuf::internal::kEmptyString);
+  name_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyString());
   options_ = NULL;
   ::memset(_has_bits_, 0, sizeof(_has_bits_));
 }
@@ -3674,7 +3674,7 @@ ServiceDescriptorProto::~ServiceDescriptorProto() {
 }
 
 void ServiceDescriptorProto::SharedDtor() {
-  if (name_ != &::google::protobuf::internal::kEmptyString) {
+  if (name_ != &::google::protobuf::internal::GetEmptyString()) {
     delete name_;
   }
   if (this != default_instance_) {
@@ -3706,7 +3706,7 @@ ServiceDescriptorProto* ServiceDescriptorProto::New() const {
 void ServiceDescriptorProto::Clear() {
   if (_has_bits_[0 / 32] & (0xffu << (0 % 32))) {
     if (has_name()) {
-      if (name_ != &::google::protobuf::internal::kEmptyString) {
+      if (name_ != &::google::protobuf::internal::GetEmptyString()) {
         name_->clear();
       }
     }
@@ -3981,9 +3981,9 @@ MethodDescriptorProto::MethodDescriptorProto(const MethodDescriptorProto& from)
 
 void MethodDescriptorProto::SharedCtor() {
   _cached_size_ = 0;
-  name_ = const_cast< ::std::string*>(&::google::protobuf::internal::kEmptyString);
-  input_type_ = const_cast< ::std::string*>(&::google::protobuf::internal::kEmptyString);
-  output_type_ = const_cast< ::std::string*>(&::google::protobuf::internal::kEmptyString);
+  name_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyString());
+  input_type_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyString());
+  output_type_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyString());
   options_ = NULL;
   ::memset(_has_bits_, 0, sizeof(_has_bits_));
 }
@@ -3993,13 +3993,13 @@ MethodDescriptorProto::~MethodDescriptorProto() {
 }
 
 void MethodDescriptorProto::SharedDtor() {
-  if (name_ != &::google::protobuf::internal::kEmptyString) {
+  if (name_ != &::google::protobuf::internal::GetEmptyString()) {
     delete name_;
   }
-  if (input_type_ != &::google::protobuf::internal::kEmptyString) {
+  if (input_type_ != &::google::protobuf::internal::GetEmptyString()) {
     delete input_type_;
   }
-  if (output_type_ != &::google::protobuf::internal::kEmptyString) {
+  if (output_type_ != &::google::protobuf::internal::GetEmptyString()) {
     delete output_type_;
   }
   if (this != default_instance_) {
@@ -4031,17 +4031,17 @@ MethodDescriptorProto* MethodDescriptorProto::New() const {
 void MethodDescriptorProto::Clear() {
   if (_has_bits_[0 / 32] & (0xffu << (0 % 32))) {
     if (has_name()) {
-      if (name_ != &::google::protobuf::internal::kEmptyString) {
+      if (name_ != &::google::protobuf::internal::GetEmptyString()) {
         name_->clear();
       }
     }
     if (has_input_type()) {
-      if (input_type_ != &::google::protobuf::internal::kEmptyString) {
+      if (input_type_ != &::google::protobuf::internal::GetEmptyString()) {
         input_type_->clear();
       }
     }
     if (has_output_type()) {
-      if (output_type_ != &::google::protobuf::internal::kEmptyString) {
+      if (output_type_ != &::google::protobuf::internal::GetEmptyString()) {
         output_type_->clear();
       }
     }
@@ -4396,12 +4396,12 @@ FileOptions::FileOptions(const FileOptions& from)
 
 void FileOptions::SharedCtor() {
   _cached_size_ = 0;
-  java_package_ = const_cast< ::std::string*>(&::google::protobuf::internal::kEmptyString);
-  java_outer_classname_ = const_cast< ::std::string*>(&::google::protobuf::internal::kEmptyString);
+  java_package_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyString());
+  java_outer_classname_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyString());
   java_multiple_files_ = false;
   java_generate_equals_and_hash_ = false;
   optimize_for_ = 1;
-  go_package_ = const_cast< ::std::string*>(&::google::protobuf::internal::kEmptyString);
+  go_package_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyString());
   cc_generic_services_ = false;
   java_generic_services_ = false;
   py_generic_services_ = false;
@@ -4413,13 +4413,13 @@ FileOptions::~FileOptions() {
 }
 
 void FileOptions::SharedDtor() {
-  if (java_package_ != &::google::protobuf::internal::kEmptyString) {
+  if (java_package_ != &::google::protobuf::internal::GetEmptyString()) {
     delete java_package_;
   }
-  if (java_outer_classname_ != &::google::protobuf::internal::kEmptyString) {
+  if (java_outer_classname_ != &::google::protobuf::internal::GetEmptyString()) {
     delete java_outer_classname_;
   }
-  if (go_package_ != &::google::protobuf::internal::kEmptyString) {
+  if (go_package_ != &::google::protobuf::internal::GetEmptyString()) {
     delete go_package_;
   }
   if (this != default_instance_) {
@@ -4451,12 +4451,12 @@ void FileOptions::Clear() {
   _extensions_.Clear();
   if (_has_bits_[0 / 32] & (0xffu << (0 % 32))) {
     if (has_java_package()) {
-      if (java_package_ != &::google::protobuf::internal::kEmptyString) {
+      if (java_package_ != &::google::protobuf::internal::GetEmptyString()) {
         java_package_->clear();
       }
     }
     if (has_java_outer_classname()) {
-      if (java_outer_classname_ != &::google::protobuf::internal::kEmptyString) {
+      if (java_outer_classname_ != &::google::protobuf::internal::GetEmptyString()) {
         java_outer_classname_->clear();
       }
     }
@@ -4464,7 +4464,7 @@ void FileOptions::Clear() {
     java_generate_equals_and_hash_ = false;
     optimize_for_ = 1;
     if (has_go_package()) {
-      if (go_package_ != &::google::protobuf::internal::kEmptyString) {
+      if (go_package_ != &::google::protobuf::internal::GetEmptyString()) {
         go_package_->clear();
       }
     }
@@ -5369,7 +5369,7 @@ void FieldOptions::SharedCtor() {
   packed_ = false;
   lazy_ = false;
   deprecated_ = false;
-  experimental_map_key_ = const_cast< ::std::string*>(&::google::protobuf::internal::kEmptyString);
+  experimental_map_key_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyString());
   weak_ = false;
   ::memset(_has_bits_, 0, sizeof(_has_bits_));
 }
@@ -5379,7 +5379,7 @@ FieldOptions::~FieldOptions() {
 }
 
 void FieldOptions::SharedDtor() {
-  if (experimental_map_key_ != &::google::protobuf::internal::kEmptyString) {
+  if (experimental_map_key_ != &::google::protobuf::internal::GetEmptyString()) {
     delete experimental_map_key_;
   }
   if (this != default_instance_) {
@@ -5415,7 +5415,7 @@ void FieldOptions::Clear() {
     lazy_ = false;
     deprecated_ = false;
     if (has_experimental_map_key()) {
-      if (experimental_map_key_ != &::google::protobuf::internal::kEmptyString) {
+      if (experimental_map_key_ != &::google::protobuf::internal::GetEmptyString()) {
         experimental_map_key_->clear();
       }
     }
@@ -6788,7 +6788,7 @@ UninterpretedOption_NamePart::UninterpretedOption_NamePart(const UninterpretedOp
 
 void UninterpretedOption_NamePart::SharedCtor() {
   _cached_size_ = 0;
-  name_part_ = const_cast< ::std::string*>(&::google::protobuf::internal::kEmptyString);
+  name_part_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyString());
   is_extension_ = false;
   ::memset(_has_bits_, 0, sizeof(_has_bits_));
 }
@@ -6798,7 +6798,7 @@ UninterpretedOption_NamePart::~UninterpretedOption_NamePart() {
 }
 
 void UninterpretedOption_NamePart::SharedDtor() {
-  if (name_part_ != &::google::protobuf::internal::kEmptyString) {
+  if (name_part_ != &::google::protobuf::internal::GetEmptyString()) {
     delete name_part_;
   }
   if (this != default_instance_) {
@@ -6829,7 +6829,7 @@ UninterpretedOption_NamePart* UninterpretedOption_NamePart::New() const {
 void UninterpretedOption_NamePart::Clear() {
   if (_has_bits_[0 / 32] & (0xffu << (0 % 32))) {
     if (has_name_part()) {
-      if (name_part_ != &::google::protobuf::internal::kEmptyString) {
+      if (name_part_ != &::google::protobuf::internal::GetEmptyString()) {
         name_part_->clear();
       }
     }
@@ -7057,12 +7057,12 @@ UninterpretedOption::UninterpretedOption(const UninterpretedOption& from)
 
 void UninterpretedOption::SharedCtor() {
   _cached_size_ = 0;
-  identifier_value_ = const_cast< ::std::string*>(&::google::protobuf::internal::kEmptyString);
+  identifier_value_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyString());
   positive_int_value_ = GOOGLE_ULONGLONG(0);
   negative_int_value_ = GOOGLE_LONGLONG(0);
   double_value_ = 0;
-  string_value_ = const_cast< ::std::string*>(&::google::protobuf::internal::kEmptyString);
-  aggregate_value_ = const_cast< ::std::string*>(&::google::protobuf::internal::kEmptyString);
+  string_value_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyString());
+  aggregate_value_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyString());
   ::memset(_has_bits_, 0, sizeof(_has_bits_));
 }
 
@@ -7071,13 +7071,13 @@ UninterpretedOption::~UninterpretedOption() {
 }
 
 void UninterpretedOption::SharedDtor() {
-  if (identifier_value_ != &::google::protobuf::internal::kEmptyString) {
+  if (identifier_value_ != &::google::protobuf::internal::GetEmptyString()) {
     delete identifier_value_;
   }
-  if (string_value_ != &::google::protobuf::internal::kEmptyString) {
+  if (string_value_ != &::google::protobuf::internal::GetEmptyString()) {
     delete string_value_;
   }
-  if (aggregate_value_ != &::google::protobuf::internal::kEmptyString) {
+  if (aggregate_value_ != &::google::protobuf::internal::GetEmptyString()) {
     delete aggregate_value_;
   }
   if (this != default_instance_) {
@@ -7108,7 +7108,7 @@ UninterpretedOption* UninterpretedOption::New() const {
 void UninterpretedOption::Clear() {
   if (_has_bits_[1 / 32] & (0xffu << (1 % 32))) {
     if (has_identifier_value()) {
-      if (identifier_value_ != &::google::protobuf::internal::kEmptyString) {
+      if (identifier_value_ != &::google::protobuf::internal::GetEmptyString()) {
         identifier_value_->clear();
       }
     }
@@ -7116,12 +7116,12 @@ void UninterpretedOption::Clear() {
     negative_int_value_ = GOOGLE_LONGLONG(0);
     double_value_ = 0;
     if (has_string_value()) {
-      if (string_value_ != &::google::protobuf::internal::kEmptyString) {
+      if (string_value_ != &::google::protobuf::internal::GetEmptyString()) {
         string_value_->clear();
       }
     }
     if (has_aggregate_value()) {
-      if (aggregate_value_ != &::google::protobuf::internal::kEmptyString) {
+      if (aggregate_value_ != &::google::protobuf::internal::GetEmptyString()) {
         aggregate_value_->clear();
       }
     }
@@ -7546,8 +7546,8 @@ SourceCodeInfo_Location::SourceCodeInfo_Location(const SourceCodeInfo_Location&
 
 void SourceCodeInfo_Location::SharedCtor() {
   _cached_size_ = 0;
-  leading_comments_ = const_cast< ::std::string*>(&::google::protobuf::internal::kEmptyString);
-  trailing_comments_ = const_cast< ::std::string*>(&::google::protobuf::internal::kEmptyString);
+  leading_comments_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyString());
+  trailing_comments_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyString());
   ::memset(_has_bits_, 0, sizeof(_has_bits_));
 }
 
@@ -7556,10 +7556,10 @@ SourceCodeInfo_Location::~SourceCodeInfo_Location() {
 }
 
 void SourceCodeInfo_Location::SharedDtor() {
-  if (leading_comments_ != &::google::protobuf::internal::kEmptyString) {
+  if (leading_comments_ != &::google::protobuf::internal::GetEmptyString()) {
     delete leading_comments_;
   }
-  if (trailing_comments_ != &::google::protobuf::internal::kEmptyString) {
+  if (trailing_comments_ != &::google::protobuf::internal::GetEmptyString()) {
     delete trailing_comments_;
   }
   if (this != default_instance_) {
@@ -7590,12 +7590,12 @@ SourceCodeInfo_Location* SourceCodeInfo_Location::New() const {
 void SourceCodeInfo_Location::Clear() {
   if (_has_bits_[2 / 32] & (0xffu << (2 % 32))) {
     if (has_leading_comments()) {
-      if (leading_comments_ != &::google::protobuf::internal::kEmptyString) {
+      if (leading_comments_ != &::google::protobuf::internal::GetEmptyString()) {
         leading_comments_->clear();
       }
     }
     if (has_trailing_comments()) {
-      if (trailing_comments_ != &::google::protobuf::internal::kEmptyString) {
+      if (trailing_comments_ != &::google::protobuf::internal::GetEmptyString()) {
         trailing_comments_->clear();
       }
     }

src/google/protobuf/generated_message_reflection.cc

@@ -68,7 +68,7 @@ bool ParseNamedEnum(const EnumDescriptor* descriptor,
 
 const string& NameOfEnum(const EnumDescriptor* descriptor, int value) {
   const EnumValueDescriptor* d = descriptor->FindValueByNumber(value);
-  return (d == NULL ? kEmptyString : d->name());
+  return (d == NULL ? GetEmptyString() : d->name());
 }
 
 // ===================================================================
@@ -771,7 +771,7 @@ string GeneratedMessageReflection::GetString(
     }
 
     GOOGLE_LOG(FATAL) << "Can't get here.";
-    return kEmptyString;  // Make compiler happy.
+    return GetEmptyString();  // Make compiler happy.
   }
 }
 
@@ -790,7 +790,7 @@ const string& GeneratedMessageReflection::GetStringReference(
     }
 
     GOOGLE_LOG(FATAL) << "Can't get here.";
-    return kEmptyString;  // Make compiler happy.
+    return GetEmptyString();  // Make compiler happy.
   }
 }
 
@@ -832,7 +832,7 @@ string GeneratedMessageReflection::GetRepeatedString(
     }
 
     GOOGLE_LOG(FATAL) << "Can't get here.";
-    return kEmptyString;  // Make compiler happy.
+    return GetEmptyString();  // Make compiler happy.
   }
 }
 
@@ -850,7 +850,7 @@ const string& GeneratedMessageReflection::GetRepeatedStringReference(
     }
 
     GOOGLE_LOG(FATAL) << "Can't get here.";
-    return kEmptyString;  // Make compiler happy.
+    return GetEmptyString();  // Make compiler happy.
   }
 }
 

src/google/protobuf/generated_message_util.cc

@@ -47,7 +47,12 @@ double NaN() {
   return std::numeric_limits<double>::quiet_NaN();
 }
 
-const ::std::string kEmptyString;
+const ::std::string* empty_string_;
+ProtobufOnceType empty_string_once_init_;
+
+void InitEmptyString() {
+  empty_string_ = new std::string;
+}
 
 }  // namespace internal
 }  // namespace protobuf

src/google/protobuf/generated_message_util.h

@@ -41,6 +41,7 @@
 #include <string>
 
 #include <google/protobuf/stubs/common.h>
+#include <google/protobuf/stubs/once.h>
 namespace google {
 namespace protobuf {
 namespace internal {
@@ -59,8 +60,17 @@ namespace internal {
 LIBPROTOBUF_EXPORT double Infinity();
 LIBPROTOBUF_EXPORT double NaN();
 
-// Constant used for empty default strings.
-LIBPROTOBUF_EXPORT extern const ::std::string kEmptyString;
+// Default empty string object. Don't use the pointer directly. Instead, call
+// GetEmptyString() to get the reference.
+LIBPROTOBUF_EXPORT extern const ::std::string* empty_string_;
+LIBPROTOBUF_EXPORT extern ProtobufOnceType empty_string_once_init_;
+
+LIBPROTOBUF_EXPORT void InitEmptyString();
+
+LIBPROTOBUF_EXPORT inline const ::std::string& GetEmptyString() {
+  GoogleOnceInit(&empty_string_once_init_, &InitEmptyString);
+  return *empty_string_;
+}
 
 // Defined in generated_message_reflection.cc -- not actually part of the lite
 // library.

src/google/protobuf/repeated_field.h

@@ -383,7 +383,7 @@ class LIBPROTOBUF_EXPORT StringTypeHandlerBase {
   static void Clear(string* value) { value->clear(); }
   static void Merge(const string& from, string* to) { *to = from; }
   static const Type& default_instance() {
-    return ::google::protobuf::internal::kEmptyString;
+    return ::google::protobuf::internal::GetEmptyString();
   }
 };