path: root/contrib/libs/protoc/src/google/protobuf/compiler/cpp/cpp_helpers.cc

// Protocol Buffers - Google's data interchange format
// Copyright 2008 Google Inc.  All rights reserved.
// https://developers.google.com/protocol-buffers/
//
// 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 with the
// distribution.
//     * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

// Author: kenton@google.com (Kenton Varda)
//  Based on original Protocol Buffers design by
//  Sanjay Ghemawat, Jeff Dean, and others.

#include <google/protobuf/compiler/cpp/cpp_helpers.h>

#include <cstdint>
#include <functional>
#include <limits>
#include <map>
#include <queue>
#include <unordered_set>
#include <vector>

#include <google/protobuf/stubs/common.h>
#include <google/protobuf/stubs/logging.h>
#include <google/protobuf/compiler/cpp/cpp_options.h>
#include <google/protobuf/compiler/cpp/cpp_names.h>
#include <google/protobuf/descriptor.pb.h>
#include <google/protobuf/descriptor.h>
#include <google/protobuf/compiler/scc.h>
#include <google/protobuf/io/printer.h>
#include <google/protobuf/io/zero_copy_stream.h>
#include <google/protobuf/dynamic_message.h>
#include <google/protobuf/wire_format.h>
#include <google/protobuf/wire_format_lite.h>
#include <google/protobuf/stubs/strutil.h>
#include <google/protobuf/stubs/substitute.h>
#include <google/protobuf/stubs/hash.h>

#include <google/protobuf/port_def.inc>

namespace google {
namespace protobuf {
namespace compiler {
namespace cpp {

namespace {

static const char kAnyMessageName[] = "Any";
static const char kAnyProtoFile[] = "google/protobuf/any.proto";

TProtoStringType DotsToColons(const TProtoStringType& name) {
  return StringReplace(name, ".", "::", true);
}

static const char* const kKeywordList[] = {  //
    "NULL",
    "alignas",
    "alignof",
    "and",
    "and_eq",
    "asm",
    "auto",
    "bitand",
    "bitor",
    "bool",
    "break",
    "case",
    "catch",
    "char",
    "class",
    "compl",
    "concept",
    "const",
    "const_cast",
    "consteval",
    "constexpr",
    "constinit",
    "continue",
    "decltype",
    "default",
    "delete",
    "do",
    "double",
    "dynamic_cast",
    "else",
    "enum",
    "explicit",
    "export",
    "extern",
    "false",
    "float",
    "for",
    "friend",
    "goto",
    "if",
    "inline",
    "int",
    "long",
    "mutable",
    "namespace",
    "new",
    "noexcept",
    "not",
    "not_eq",
    "nullptr",
    "operator",
    "or",
    "or_eq",
    "private",
    "protected",
    "public",
    "register",
    "reinterpret_cast",
    "requires",
    "return",
    "short",
    "signed",
    "sizeof",
    "static",
    "static_assert",
    "static_cast",
    "struct",
    "switch",
    "template",
    "this",
    "thread_local",
    "throw",
    "true",
    "try",
    "typedef",
    "typeid",
    "typename",
    "union",
    "unsigned",
    "using",
    "virtual",
    "void",
    "volatile",
    "wchar_t",
    "while",
    "xor",
    "xor_eq"};

static std::unordered_set<TProtoStringType>* MakeKeywordsMap() {
  auto* result = new std::unordered_set<TProtoStringType>();
  for (const auto keyword : kKeywordList) {
    result->emplace(keyword);
  }
  return result;
}

static std::unordered_set<TProtoStringType>& kKeywords = *MakeKeywordsMap();

TProtoStringType IntTypeName(const Options& options, const TProtoStringType& type) {
  if (options.opensource_runtime) {
    return "::PROTOBUF_NAMESPACE_ID::" + type;
  } else {
    return "::" + type;
  }
}

void SetIntVar(const Options& options, const TProtoStringType& type,
               std::map<TProtoStringType, TProtoStringType>* variables) {
  (*variables)[type] = IntTypeName(options, type);
}
bool IsEagerlyVerifiedLazyImpl(const FieldDescriptor* field,
                               const Options& options,
                               MessageSCCAnalyzer* scc_analyzer) {
  return false;
}

}  // namespace

bool IsLazy(const FieldDescriptor* field, const Options& options,
            MessageSCCAnalyzer* scc_analyzer) {
  return IsLazilyVerifiedLazy(field, options) ||
         IsEagerlyVerifiedLazyImpl(field, options, scc_analyzer);
}

void SetCommonVars(const Options& options,
                   std::map<TProtoStringType, TProtoStringType>* variables) {
  (*variables)["proto_ns"] = ProtobufNamespace(options);

  // Warning: there is some clever naming/splitting here to avoid extract script
  // rewrites.  The names of these variables must not be things that the extract
  // script will rewrite.  That's why we use "CHK" (for example) instead of
  // "GOOGLE_CHECK".
  if (options.opensource_runtime) {
    (*variables)["GOOGLE_PROTOBUF"] = "GOOGLE_PROTOBUF";
    (*variables)["CHK"] = "GOOGLE_CHECK";
    (*variables)["DCHK"] = "GOOGLE_DCHECK";
  } else {
    // These values are things the extract script would rewrite if we did not
    // split them.  It might not strictly matter since we don't generate google3
    // code in open-source.  But it's good to prevent surprising things from
    // happening.
    (*variables)["GOOGLE_PROTOBUF"] =
        "GOOGLE3"
        "_PROTOBUF";
    (*variables)["CHK"] =
        "CH"
        "ECK";
    (*variables)["DCHK"] =
        "DCH"
        "ECK";
  }

  SetIntVar(options, "int8", variables);
  SetIntVar(options, "uint8", variables);
  SetIntVar(options, "uint32", variables);
  SetIntVar(options, "uint64", variables);
  SetIntVar(options, "int32", variables);
  SetIntVar(options, "int64", variables);
  (*variables)["string"] = "TProtoStringType";
}

void SetUnknownFieldsVariable(const Descriptor* descriptor,
                              const Options& options,
                              std::map<TProtoStringType, TProtoStringType>* variables) {
  TProtoStringType proto_ns = ProtobufNamespace(options);
  TProtoStringType unknown_fields_type;
  if (UseUnknownFieldSet(descriptor->file(), options)) {
    unknown_fields_type = "::" + proto_ns + "::UnknownFieldSet";
    (*variables)["unknown_fields"] =
        "_internal_metadata_.unknown_fields<" + unknown_fields_type + ">(" +
        unknown_fields_type + "::default_instance)";
  } else {
    unknown_fields_type =
        PrimitiveTypeName(options, FieldDescriptor::CPPTYPE_STRING);
    (*variables)["unknown_fields"] = "_internal_metadata_.unknown_fields<" +
                                     unknown_fields_type + ">(::" + proto_ns +
                                     "::internal::GetEmptyString)";
  }
  (*variables)["unknown_fields_type"] = unknown_fields_type;
  (*variables)["have_unknown_fields"] =
      "_internal_metadata_.have_unknown_fields()";
  (*variables)["mutable_unknown_fields"] =
      "_internal_metadata_.mutable_unknown_fields<" + unknown_fields_type +
      ">()";
}

TProtoStringType UnderscoresToCamelCase(const TProtoStringType& input,
                                   bool cap_next_letter) {
  TProtoStringType result;
  // Note:  I distrust ctype.h due to locales.
  for (int i = 0; i < input.size(); i++) {
    if ('a' <= input[i] && input[i] <= 'z') {
      if (cap_next_letter) {
        result += input[i] + ('A' - 'a');
      } else {
        result += input[i];
      }
      cap_next_letter = false;
    } else if ('A' <= input[i] && input[i] <= 'Z') {
      // Capital letters are left as-is.
      result += input[i];
      cap_next_letter = false;
    } else if ('0' <= input[i] && input[i] <= '9') {
      result += input[i];
      cap_next_letter = true;
    } else {
      cap_next_letter = true;
    }
  }
  return result;
}

const char kThickSeparator[] =
    "// ===================================================================\n";
const char kThinSeparator[] =
    "// -------------------------------------------------------------------\n";

bool CanInitializeByZeroing(const FieldDescriptor* field) {
  if (field->is_repeated() || field->is_extension()) return false;
  switch (field->cpp_type()) {
    case FieldDescriptor::CPPTYPE_ENUM:
      return field->default_value_enum()->number() == 0;
    case FieldDescriptor::CPPTYPE_INT32:
      return field->default_value_int32() == 0;
    case FieldDescriptor::CPPTYPE_INT64:
      return field->default_value_int64() == 0;
    case FieldDescriptor::CPPTYPE_UINT32:
      return field->default_value_uint32() == 0;
    case FieldDescriptor::CPPTYPE_UINT64:
      return field->default_value_uint64() == 0;
    case FieldDescriptor::CPPTYPE_FLOAT:
      return field->default_value_float() == 0;
    case FieldDescriptor::CPPTYPE_DOUBLE:
      return field->default_value_double() == 0;
    case FieldDescriptor::CPPTYPE_BOOL:
      return field->default_value_bool() == false;
    default:
      return false;
  }
}

TProtoStringType ClassName(const Descriptor* descriptor) {
  const Descriptor* parent = descriptor->containing_type();
  TProtoStringType res;
  if (parent) res += ClassName(parent) + "_";
  res += descriptor->name();
  if (IsMapEntryMessage(descriptor)) res += "_DoNotUse";
  return ResolveKeyword(res);
}

TProtoStringType ClassName(const EnumDescriptor* enum_descriptor) {
  if (enum_descriptor->containing_type() == nullptr) {
    return ResolveKeyword(enum_descriptor->name());
  } else {
    return ClassName(enum_descriptor->containing_type()) + "_" +
           enum_descriptor->name();
  }
}

TProtoStringType QualifiedClassName(const Descriptor* d, const Options& options) {
  return QualifiedFileLevelSymbol(d->file(), ClassName(d), options);
}

TProtoStringType QualifiedClassName(const EnumDescriptor* d,
                               const Options& options) {
  return QualifiedFileLevelSymbol(d->file(), ClassName(d), options);
}

TProtoStringType QualifiedClassName(const Descriptor* d) {
  return QualifiedClassName(d, Options());
}

TProtoStringType QualifiedClassName(const EnumDescriptor* d) {
  return QualifiedClassName(d, Options());
}

TProtoStringType ExtensionName(const FieldDescriptor* d) {
  if (const Descriptor* scope = d->extension_scope())
    return StrCat(ClassName(scope), "::", ResolveKeyword(d->name()));
  return ResolveKeyword(d->name());
}

TProtoStringType QualifiedExtensionName(const FieldDescriptor* d,
                                   const Options& options) {
  GOOGLE_DCHECK(d->is_extension());
  return QualifiedFileLevelSymbol(d->file(), ExtensionName(d), options);
}

TProtoStringType QualifiedExtensionName(const FieldDescriptor* d) {
  return QualifiedExtensionName(d, Options());
}

TProtoStringType Namespace(const TProtoStringType& package) {
  if (package.empty()) return "";
  return "::" + DotsToColons(package);
}

TProtoStringType Namespace(const FileDescriptor* d, const Options& options) {
  TProtoStringType ret = Namespace(d->package());
  if (IsWellKnownMessage(d) && options.opensource_runtime) {
    // Written with string concatenation to prevent rewriting of
    // ::google::protobuf.
    ret = StringReplace(ret,
                        "::google::"
                        "protobuf",
                        "::PROTOBUF_NAMESPACE_ID", false);
  }
  return ret;
}

TProtoStringType Namespace(const Descriptor* d, const Options& options) {
  return Namespace(d->file(), options);
}

TProtoStringType Namespace(const FieldDescriptor* d, const Options& options) {
  return Namespace(d->file(), options);
}

TProtoStringType Namespace(const EnumDescriptor* d, const Options& options) {
  return Namespace(d->file(), options);
}

TProtoStringType DefaultInstanceType(const Descriptor* descriptor,
                                const Options& options) {
  return ClassName(descriptor) + "DefaultTypeInternal";
}

TProtoStringType DefaultInstanceName(const Descriptor* descriptor,
                                const Options& options) {
  return "_" + ClassName(descriptor, false) + "_default_instance_";
}

TProtoStringType DefaultInstancePtr(const Descriptor* descriptor,
                               const Options& options) {
  return DefaultInstanceName(descriptor, options) + "ptr_";
}

TProtoStringType QualifiedDefaultInstanceName(const Descriptor* descriptor,
                                         const Options& options) {
  return QualifiedFileLevelSymbol(
      descriptor->file(), DefaultInstanceName(descriptor, options), options);
}

TProtoStringType QualifiedDefaultInstancePtr(const Descriptor* descriptor,
                                        const Options& options) {
  return QualifiedDefaultInstanceName(descriptor, options) + "ptr_";
}

TProtoStringType DescriptorTableName(const FileDescriptor* file,
                                const Options& options) {
  return UniqueName("descriptor_table", file, options);
}

TProtoStringType FileDllExport(const FileDescriptor* file, const Options& options) {
  return UniqueName("PROTOBUF_INTERNAL_EXPORT", file, options);
}

TProtoStringType SuperClassName(const Descriptor* descriptor,
                           const Options& options) {
  if (!HasDescriptorMethods(descriptor->file(), options)) {
    return "::" + ProtobufNamespace(options) + "::MessageLite";
  }
  auto simple_base = SimpleBaseClass(descriptor, options);
  if (simple_base.empty()) {
    return "::" + ProtobufNamespace(options) + "::Message";
  }
  return "::" + ProtobufNamespace(options) + "::internal::" + simple_base;
}

TProtoStringType ResolveKeyword(const TProtoStringType& name) {
  if (kKeywords.count(name) > 0) {
    return name + "_";
  }
  return name;
}

TProtoStringType FieldName(const FieldDescriptor* field) {
  TProtoStringType result = field->name();
  LowerString(&result);
  if (kKeywords.count(result) > 0) {
    result.append("_");
  }
  return result;
}

TProtoStringType EnumValueName(const EnumValueDescriptor* enum_value) {
  TProtoStringType result = enum_value->name();
  if (kKeywords.count(result) > 0) {
    result.append("_");
  }
  return result;
}

int EstimateAlignmentSize(const FieldDescriptor* field) {
  if (field == nullptr) return 0;
  if (field->is_repeated()) return 8;
  switch (field->cpp_type()) {
    case FieldDescriptor::CPPTYPE_BOOL:
      return 1;

    case FieldDescriptor::CPPTYPE_INT32:
    case FieldDescriptor::CPPTYPE_UINT32:
    case FieldDescriptor::CPPTYPE_ENUM:
    case FieldDescriptor::CPPTYPE_FLOAT:
      return 4;

    case FieldDescriptor::CPPTYPE_INT64:
    case FieldDescriptor::CPPTYPE_UINT64:
    case FieldDescriptor::CPPTYPE_DOUBLE:
    case FieldDescriptor::CPPTYPE_STRING:
    case FieldDescriptor::CPPTYPE_MESSAGE:
      return 8;
  }
  GOOGLE_LOG(FATAL) << "Can't get here.";
  return -1;  // Make compiler happy.
}

TProtoStringType FieldConstantName(const FieldDescriptor* field) {
  TProtoStringType field_name = UnderscoresToCamelCase(field->name(), true);
  TProtoStringType result = "k" + field_name + "FieldNumber";

  if (!field->is_extension() &&
      field->containing_type()->FindFieldByCamelcaseName(
          field->camelcase_name()) != field) {
    // This field's camelcase name is not unique.  As a hack, add the field
    // number to the constant name.  This makes the constant rather useless,
    // but what can we do?
    result += "_" + StrCat(field->number());
  }

  return result;
}

TProtoStringType FieldMessageTypeName(const FieldDescriptor* field,
                                 const Options& options) {
  // Note:  The Google-internal version of Protocol Buffers uses this function
  //   as a hook point for hacks to support legacy code.
  return QualifiedClassName(field->message_type(), options);
}

TProtoStringType StripProto(const TProtoStringType& filename) {
  /*
   * TODO(github/georgthegreat) remove this proxy method
   * once Google's internal codebase will become ready
   */
  return compiler::StripProto(filename);
}

const char* PrimitiveTypeName(FieldDescriptor::CppType type) {
  switch (type) {
    case FieldDescriptor::CPPTYPE_INT32:
      return "::google::protobuf::int32";
    case FieldDescriptor::CPPTYPE_INT64:
      return "::google::protobuf::int64";
    case FieldDescriptor::CPPTYPE_UINT32:
      return "::google::protobuf::uint32";
    case FieldDescriptor::CPPTYPE_UINT64:
      return "::google::protobuf::uint64";
    case FieldDescriptor::CPPTYPE_DOUBLE:
      return "double";
    case FieldDescriptor::CPPTYPE_FLOAT:
      return "float";
    case FieldDescriptor::CPPTYPE_BOOL:
      return "bool";
    case FieldDescriptor::CPPTYPE_ENUM:
      return "int";
    case FieldDescriptor::CPPTYPE_STRING:
      return "TProtoStringType";
    case FieldDescriptor::CPPTYPE_MESSAGE:
      return nullptr;

      // No default because we want the compiler to complain if any new
      // CppTypes are added.
  }

  GOOGLE_LOG(FATAL) << "Can't get here.";
  return nullptr;
}

TProtoStringType PrimitiveTypeName(const Options& options,
                              FieldDescriptor::CppType type) {
  switch (type) {
    case FieldDescriptor::CPPTYPE_INT32:
      return IntTypeName(options, "int32");
    case FieldDescriptor::CPPTYPE_INT64:
      return IntTypeName(options, "int64");
    case FieldDescriptor::CPPTYPE_UINT32:
      return IntTypeName(options, "uint32");
    case FieldDescriptor::CPPTYPE_UINT64:
      return IntTypeName(options, "uint64");
    case FieldDescriptor::CPPTYPE_DOUBLE:
      return "double";
    case FieldDescriptor::CPPTYPE_FLOAT:
      return "float";
    case FieldDescriptor::CPPTYPE_BOOL:
      return "bool";
    case FieldDescriptor::CPPTYPE_ENUM:
      return "int";
    case FieldDescriptor::CPPTYPE_STRING:
      return "TProtoStringType";
    case FieldDescriptor::CPPTYPE_MESSAGE:
      return "";

      // No default because we want the compiler to complain if any new
      // CppTypes are added.
  }

  GOOGLE_LOG(FATAL) << "Can't get here.";
  return "";
}

const char* DeclaredTypeMethodName(FieldDescriptor::Type type) {
  switch (type) {
    case FieldDescriptor::TYPE_INT32:
      return "Int32";
    case FieldDescriptor::TYPE_INT64:
      return "Int64";
    case FieldDescriptor::TYPE_UINT32:
      return "UInt32";
    case FieldDescriptor::TYPE_UINT64:
      return "UInt64";
    case FieldDescriptor::TYPE_SINT32:
      return "SInt32";
    case FieldDescriptor::TYPE_SINT64:
      return "SInt64";
    case FieldDescriptor::TYPE_FIXED32:
      return "Fixed32";
    case FieldDescriptor::TYPE_FIXED64:
      return "Fixed64";
    case FieldDescriptor::TYPE_SFIXED32:
      return "SFixed32";
    case FieldDescriptor::TYPE_SFIXED64:
      return "SFixed64";
    case FieldDescriptor::TYPE_FLOAT:
      return "Float";
    case FieldDescriptor::TYPE_DOUBLE:
      return "Double";

    case FieldDescriptor::TYPE_BOOL:
      return "Bool";
    case FieldDescriptor::TYPE_ENUM:
      return "Enum";

    case FieldDescriptor::TYPE_STRING:
      return "String";
    case FieldDescriptor::TYPE_BYTES:
      return "Bytes";
    case FieldDescriptor::TYPE_GROUP:
      return "Group";
    case FieldDescriptor::TYPE_MESSAGE:
      return "Message";

      // No default because we want the compiler to complain if any new
      // types are added.
  }
  GOOGLE_LOG(FATAL) << "Can't get here.";
  return "";
}

TProtoStringType Int32ToString(int number) {
  if (number == std::numeric_limits<int32_t>::min()) {
    // This needs to be special-cased, see explanation here:
    // https://gcc.gnu.org/bugzilla/show_bug.cgi?id=52661
    return StrCat(number + 1, " - 1");
  } else {
    return StrCat(number);
  }
}

static TProtoStringType Int64ToString(int64_t number) {
  if (number == std::numeric_limits<int64_t>::min()) {
    // This needs to be special-cased, see explanation here:
    // https://gcc.gnu.org/bugzilla/show_bug.cgi?id=52661
    return StrCat("int64_t{", number + 1, "} - 1");
  }
  return StrCat("int64_t{", number, "}");
}

static TProtoStringType UInt64ToString(uint64_t number) {
  return StrCat("uint64_t{", number, "u}");
}

TProtoStringType DefaultValue(const FieldDescriptor* field) {
  return DefaultValue(Options(), field);
}

TProtoStringType DefaultValue(const Options& options, const FieldDescriptor* field) {
  switch (field->cpp_type()) {
    case FieldDescriptor::CPPTYPE_INT32:
      return Int32ToString(field->default_value_int32());
    case FieldDescriptor::CPPTYPE_UINT32:
      return StrCat(field->default_value_uint32()) + "u";
    case FieldDescriptor::CPPTYPE_INT64:
      return Int64ToString(field->default_value_int64());
    case FieldDescriptor::CPPTYPE_UINT64:
      return UInt64ToString(field->default_value_uint64());
    case FieldDescriptor::CPPTYPE_DOUBLE: {
      double value = field->default_value_double();
      if (value == std::numeric_limits<double>::infinity()) {
        return "std::numeric_limits<double>::infinity()";
      } else if (value == -std::numeric_limits<double>::infinity()) {
        return "-std::numeric_limits<double>::infinity()";
      } else if (value != value) {
        return "std::numeric_limits<double>::quiet_NaN()";
      } else {
        return SimpleDtoa(value);
      }
    }
    case FieldDescriptor::CPPTYPE_FLOAT: {
      float value = field->default_value_float();
      if (value == std::numeric_limits<float>::infinity()) {
        return "std::numeric_limits<float>::infinity()";
      } else if (value == -std::numeric_limits<float>::infinity()) {
        return "-std::numeric_limits<float>::infinity()";
      } else if (value != value) {
        return "std::numeric_limits<float>::quiet_NaN()";
      } else {
        TProtoStringType float_value = SimpleFtoa(value);
        // If floating point value contains a period (.) or an exponent
        // (either E or e), then append suffix 'f' to make it a float
        // literal.
        if (float_value.find_first_of(".eE") != TProtoStringType::npos) {
          float_value.push_back('f');
        }
        return float_value;
      }
    }
    case FieldDescriptor::CPPTYPE_BOOL:
      return field->default_value_bool() ? "true" : "false";
    case FieldDescriptor::CPPTYPE_ENUM:
      // Lazy:  Generate a static_cast because we don't have a helper function
      //   that constructs the full name of an enum value.
      return strings::Substitute(
          "static_cast< $0 >($1)", ClassName(field->enum_type(), true),
          Int32ToString(field->default_value_enum()->number()));
    case FieldDescriptor::CPPTYPE_STRING:
      return "\"" +
             EscapeTrigraphs(CEscape(field->default_value_string())) +
             "\"";
    case FieldDescriptor::CPPTYPE_MESSAGE:
      return "*" + FieldMessageTypeName(field, options) +
             "::internal_default_instance()";
  }
  // Can't actually get here; make compiler happy.  (We could add a default
  // case above but then we wouldn't get the nice compiler warning when a
  // new type is added.)
  GOOGLE_LOG(FATAL) << "Can't get here.";
  return "";
}

// Convert a file name into a valid identifier.
TProtoStringType FilenameIdentifier(const TProtoStringType& filename) {
  TProtoStringType result;
  for (int i = 0; i < filename.size(); i++) {
    if (ascii_isalnum(filename[i])) {
      result.push_back(filename[i]);
    } else {
      // Not alphanumeric.  To avoid any possibility of name conflicts we
      // use the hex code for the character.
      StrAppend(&result, "_",
                      strings::Hex(static_cast<uint8_t>(filename[i])));
    }
  }
  return result;
}

TProtoStringType UniqueName(const TProtoStringType& name, const TProtoStringType& filename,
                       const Options& options) {
  return name + "_" + FilenameIdentifier(filename);
}

// Return the qualified C++ name for a file level symbol.
TProtoStringType QualifiedFileLevelSymbol(const FileDescriptor* file,
                                     const TProtoStringType& name,
                                     const Options& options) {
  if (file->package().empty()) {
    return StrCat("::", name);
  }
  return StrCat(Namespace(file, options), "::", name);
}

// Escape C++ trigraphs by escaping question marks to \?
TProtoStringType EscapeTrigraphs(const TProtoStringType& to_escape) {
  return StringReplace(to_escape, "?", "\\?", true);
}

// Escaped function name to eliminate naming conflict.
TProtoStringType SafeFunctionName(const Descriptor* descriptor,
                             const FieldDescriptor* field,
                             const TProtoStringType& prefix) {
  // Do not use FieldName() since it will escape keywords.
  TProtoStringType name = field->name();
  LowerString(&name);
  TProtoStringType function_name = prefix + name;
  if (descriptor->FindFieldByName(function_name)) {
    // Single underscore will also make it conflicting with the private data
    // member. We use double underscore to escape function names.
    function_name.append("__");
  } else if (kKeywords.count(name) > 0) {
    // If the field name is a keyword, we append the underscore back to keep it
    // consistent with other function names.
    function_name.append("_");
  }
  return function_name;
}

bool IsStringInlined(const FieldDescriptor* /* descriptor */,
                     const Options& /* options */) {
  return false;
}

static bool HasLazyFields(const Descriptor* descriptor, const Options& options,
                          MessageSCCAnalyzer* scc_analyzer) {
  for (int field_idx = 0; field_idx < descriptor->field_count(); field_idx++) {
    if (IsLazy(descriptor->field(field_idx), options, scc_analyzer)) {
      return true;
    }
  }
  for (int idx = 0; idx < descriptor->extension_count(); idx++) {
    if (IsLazy(descriptor->extension(idx), options, scc_analyzer)) {
      return true;
    }
  }
  for (int idx = 0; idx < descriptor->nested_type_count(); idx++) {
    if (HasLazyFields(descriptor->nested_type(idx), options, scc_analyzer)) {
      return true;
    }
  }
  return false;
}

// Does the given FileDescriptor use lazy fields?
bool HasLazyFields(const FileDescriptor* file, const Options& options,
                   MessageSCCAnalyzer* scc_analyzer) {
  for (int i = 0; i < file->message_type_count(); i++) {
    const Descriptor* descriptor(file->message_type(i));
    if (HasLazyFields(descriptor, options, scc_analyzer)) {
      return true;
    }
  }
  for (int field_idx = 0; field_idx < file->extension_count(); field_idx++) {
    if (IsLazy(file->extension(field_idx), options, scc_analyzer)) {
      return true;
    }
  }
  return false;
}

static bool HasRepeatedFields(const Descriptor* descriptor) {
  for (int i = 0; i < descriptor->field_count(); ++i) {
    if (descriptor->field(i)->label() == FieldDescriptor::LABEL_REPEATED) {
      return true;
    }
  }
  for (int i = 0; i < descriptor->nested_type_count(); ++i) {
    if (HasRepeatedFields(descriptor->nested_type(i))) return true;
  }
  return false;
}

bool HasRepeatedFields(const FileDescriptor* file) {
  for (int i = 0; i < file->message_type_count(); ++i) {
    if (HasRepeatedFields(file->message_type(i))) return true;
  }
  return false;
}

static bool IsStringPieceField(const FieldDescriptor* field,
                               const Options& options) {
  return field->cpp_type() == FieldDescriptor::CPPTYPE_STRING &&
         EffectiveStringCType(field, options) == FieldOptions::STRING_PIECE;
}

static bool HasStringPieceFields(const Descriptor* descriptor,
                                 const Options& options) {
  for (int i = 0; i < descriptor->field_count(); ++i) {
    if (IsStringPieceField(descriptor->field(i), options)) return true;
  }
  for (int i = 0; i < descriptor->nested_type_count(); ++i) {
    if (HasStringPieceFields(descriptor->nested_type(i), options)) return true;
  }
  return false;
}

bool HasStringPieceFields(const FileDescriptor* file, const Options& options) {
  for (int i = 0; i < file->message_type_count(); ++i) {
    if (HasStringPieceFields(file->message_type(i), options)) return true;
  }
  return false;
}

static bool IsCordField(const FieldDescriptor* field, const Options& options) {
  return field->cpp_type() == FieldDescriptor::CPPTYPE_STRING &&
         EffectiveStringCType(field, options) == FieldOptions::CORD;
}

static bool HasCordFields(const Descriptor* descriptor,
                          const Options& options) {
  for (int i = 0; i < descriptor->field_count(); ++i) {
    if (IsCordField(descriptor->field(i), options)) return true;
  }
  for (int i = 0; i < descriptor->nested_type_count(); ++i) {
    if (HasCordFields(descriptor->nested_type(i), options)) return true;
  }
  return false;
}

bool HasCordFields(const FileDescriptor* file, const Options& options) {
  for (int i = 0; i < file->message_type_count(); ++i) {
    if (HasCordFields(file->message_type(i), options)) return true;
  }
  return false;
}

static bool HasExtensionsOrExtendableMessage(const Descriptor* descriptor) {
  if (descriptor->extension_range_count() > 0) return true;
  if (descriptor->extension_count() > 0) return true;
  for (int i = 0; i < descriptor->nested_type_count(); ++i) {
    if (HasExtensionsOrExtendableMessage(descriptor->nested_type(i))) {
      return true;
    }
  }
  return false;
}

bool HasExtensionsOrExtendableMessage(const FileDescriptor* file) {
  if (file->extension_count() > 0) return true;
  for (int i = 0; i < file->message_type_count(); ++i) {
    if (HasExtensionsOrExtendableMessage(file->message_type(i))) return true;
  }
  return false;
}

static bool HasMapFields(const Descriptor* descriptor) {
  for (int i = 0; i < descriptor->field_count(); ++i) {
    if (descriptor->field(i)->is_map()) {
      return true;
    }
  }
  for (int i = 0; i < descriptor->nested_type_count(); ++i) {
    if (HasMapFields(descriptor->nested_type(i))) return true;
  }
  return false;
}

bool HasMapFields(const FileDescriptor* file) {
  for (int i = 0; i < file->message_type_count(); ++i) {
    if (HasMapFields(file->message_type(i))) return true;
  }
  return false;
}

static bool HasEnumDefinitions(const Descriptor* message_type) {
  if (message_type->enum_type_count() > 0) return true;
  for (int i = 0; i < message_type->nested_type_count(); ++i) {
    if (HasEnumDefinitions(message_type->nested_type(i))) return true;
  }
  return false;
}

bool HasEnumDefinitions(const FileDescriptor* file) {
  if (file->enum_type_count() > 0) return true;
  for (int i = 0; i < file->message_type_count(); ++i) {
    if (HasEnumDefinitions(file->message_type(i))) return true;
  }
  return false;
}

bool ShouldVerify(const Descriptor* /* descriptor */,
                  const Options& /* options */,
                  MessageSCCAnalyzer* /* scc_analyzer */) {
  return false;
}

bool ShouldVerify(const FileDescriptor* /* file */,
                  const Options& /* options */,
                  MessageSCCAnalyzer* /* scc_analyzer */) {
  return false;
}

bool IsStringOrMessage(const FieldDescriptor* field) {
  switch (field->cpp_type()) {
    case FieldDescriptor::CPPTYPE_INT32:
    case FieldDescriptor::CPPTYPE_INT64:
    case FieldDescriptor::CPPTYPE_UINT32:
    case FieldDescriptor::CPPTYPE_UINT64:
    case FieldDescriptor::CPPTYPE_DOUBLE:
    case FieldDescriptor::CPPTYPE_FLOAT:
    case FieldDescriptor::CPPTYPE_BOOL:
    case FieldDescriptor::CPPTYPE_ENUM:
      return false;
    case FieldDescriptor::CPPTYPE_STRING:
    case FieldDescriptor::CPPTYPE_MESSAGE:
      return true;
  }

  GOOGLE_LOG(FATAL) << "Can't get here.";
  return false;
}

FieldOptions::CType EffectiveStringCType(const FieldDescriptor* field,
                                         const Options& options) {
  GOOGLE_DCHECK(field->cpp_type() == FieldDescriptor::CPPTYPE_STRING);
  if (options.opensource_runtime) {
    // Open-source protobuf release only supports STRING ctype.
    return FieldOptions::STRING;
  } else {
    // Google-internal supports all ctypes.
    return field->options().ctype();
  }
}

bool IsAnyMessage(const FileDescriptor* descriptor, const Options& options) {
  return descriptor->name() == kAnyProtoFile;
}

bool IsAnyMessage(const Descriptor* descriptor, const Options& options) {
  return descriptor->name() == kAnyMessageName &&
         IsAnyMessage(descriptor->file(), options);
}

bool IsWellKnownMessage(const FileDescriptor* file) {
  static const std::unordered_set<TProtoStringType> well_known_files{
      "google/protobuf/any.proto",
      "google/protobuf/api.proto",
      "google/protobuf/compiler/plugin.proto",
      "google/protobuf/descriptor.proto",
      "google/protobuf/duration.proto",
      "google/protobuf/empty.proto",
      "google/protobuf/field_mask.proto",
      "google/protobuf/source_context.proto",
      "google/protobuf/struct.proto",
      "google/protobuf/timestamp.proto",
      "google/protobuf/type.proto",
      "google/protobuf/wrappers.proto",
  };
  return well_known_files.find(file->name()) != well_known_files.end();
}

static bool FieldEnforceUtf8(const FieldDescriptor* field,
                             const Options& options) {
  return true;
}

static bool FileUtf8Verification(const FileDescriptor* file,
                                 const Options& options) {
  return true;
}

// Which level of UTF-8 enforcemant is placed on this file.
Utf8CheckMode GetUtf8CheckMode(const FieldDescriptor* field,
                               const Options& options) {
  if (field->file()->syntax() == FileDescriptor::SYNTAX_PROTO3 &&
      FieldEnforceUtf8(field, options)) {
    return Utf8CheckMode::kStrict;
  } else if (GetOptimizeFor(field->file(), options) !=
                 FileOptions::LITE_RUNTIME &&
             FileUtf8Verification(field->file(), options)) {
    return Utf8CheckMode::kVerify;
  } else {
    return Utf8CheckMode::kNone;
  }
}

static void GenerateUtf8CheckCode(const FieldDescriptor* field,
                                  const Options& options, bool for_parse,
                                  const char* parameters,
                                  const char* strict_function,
                                  const char* verify_function,
                                  const Formatter& format) {
  switch (GetUtf8CheckMode(field, options)) {
    case Utf8CheckMode::kStrict: {
      if (for_parse) {
        format("DO_(");
      }
      format("::$proto_ns$::internal::WireFormatLite::$1$(\n", strict_function);
      format.Indent();
      format(parameters);
      if (for_parse) {
        format("::$proto_ns$::internal::WireFormatLite::PARSE,\n");
      } else {
        format("::$proto_ns$::internal::WireFormatLite::SERIALIZE,\n");
      }
      format("\"$1$\")", field->full_name());
      if (for_parse) {
        format(")");
      }
      format(";\n");
      format.Outdent();
      break;
    }
    case Utf8CheckMode::kVerify: {
      format("::$proto_ns$::internal::WireFormat::$1$(\n", verify_function);
      format.Indent();
      format(parameters);
      if (for_parse) {
        format("::$proto_ns$::internal::WireFormat::PARSE,\n");
      } else {
        format("::$proto_ns$::internal::WireFormat::SERIALIZE,\n");
      }
      format("\"$1$\");\n", field->full_name());
      format.Outdent();
      break;
    }
    case Utf8CheckMode::kNone:
      break;
  }
}

void GenerateUtf8CheckCodeForString(const FieldDescriptor* field,
                                    const Options& options, bool for_parse,
                                    const char* parameters,
                                    const Formatter& format) {
  GenerateUtf8CheckCode(field, options, for_parse, parameters,
                        "VerifyUtf8String", "VerifyUTF8StringNamedField",
                        format);
}

void GenerateUtf8CheckCodeForCord(const FieldDescriptor* field,
                                  const Options& options, bool for_parse,
                                  const char* parameters,
                                  const Formatter& format) {
  GenerateUtf8CheckCode(field, options, for_parse, parameters, "VerifyUtf8Cord",
                        "VerifyUTF8CordNamedField", format);
}

void FlattenMessagesInFile(const FileDescriptor* file,
                           std::vector<const Descriptor*>* result) {
  for (int i = 0; i < file->message_type_count(); i++) {
    ForEachMessage(file->message_type(i), [&](const Descriptor* descriptor) {
      result->push_back(descriptor);
    });
  }
}

bool HasWeakFields(const Descriptor* descriptor, const Options& options) {
  for (int i = 0; i < descriptor->field_count(); i++) {
    if (IsWeak(descriptor->field(i), options)) return true;
  }
  return false;
}

bool HasWeakFields(const FileDescriptor* file, const Options& options) {
  for (int i = 0; i < file->message_type_count(); ++i) {
    if (HasWeakFields(file->message_type(i), options)) return true;
  }
  return false;
}

bool UsingImplicitWeakFields(const FileDescriptor* file,
                             const Options& options) {
  return options.lite_implicit_weak_fields &&
         GetOptimizeFor(file, options) == FileOptions::LITE_RUNTIME;
}

bool IsImplicitWeakField(const FieldDescriptor* field, const Options& options,
                         MessageSCCAnalyzer* scc_analyzer) {
  return UsingImplicitWeakFields(field->file(), options) &&
         field->type() == FieldDescriptor::TYPE_MESSAGE &&
         !field->is_required() && !field->is_map() && !field->is_extension() &&
         !field->real_containing_oneof() &&
         !IsWellKnownMessage(field->message_type()->file()) &&
         field->message_type()->file()->name() !=
             "net/proto2/proto/descriptor.proto" &&
         // We do not support implicit weak fields between messages in the same
         // strongly-connected component.
         scc_analyzer->GetSCC(field->containing_type()) !=
             scc_analyzer->GetSCC(field->message_type());
}

MessageAnalysis MessageSCCAnalyzer::GetSCCAnalysis(const SCC* scc) {
  if (analysis_cache_.count(scc)) return analysis_cache_[scc];
  MessageAnalysis result;
  if (UsingImplicitWeakFields(scc->GetFile(), options_)) {
    result.contains_weak = true;
  }
  for (int i = 0; i < scc->descriptors.size(); i++) {
    const Descriptor* descriptor = scc->descriptors[i];
    if (descriptor->extension_range_count() > 0) {
      result.contains_extension = true;
    }
    for (int i = 0; i < descriptor->field_count(); i++) {
      const FieldDescriptor* field = descriptor->field(i);
      if (field->is_required()) {
        result.contains_required = true;
      }
      if (field->options().weak()) {
        result.contains_weak = true;
      }
      switch (field->type()) {
        case FieldDescriptor::TYPE_STRING:
        case FieldDescriptor::TYPE_BYTES: {
          if (field->options().ctype() == FieldOptions::CORD) {
            result.contains_cord = true;
          }
          break;
        }
        case FieldDescriptor::TYPE_GROUP:
        case FieldDescriptor::TYPE_MESSAGE: {
          const SCC* child = analyzer_.GetSCC(field->message_type());
          if (child != scc) {
            MessageAnalysis analysis = GetSCCAnalysis(child);
            result.contains_cord |= analysis.contains_cord;
            result.contains_extension |= analysis.contains_extension;
            if (!ShouldIgnoreRequiredFieldCheck(field, options_)) {
              result.contains_required |= analysis.contains_required;
            }
            result.contains_weak |= analysis.contains_weak;
          } else {
            // This field points back into the same SCC hence the messages
            // in the SCC are recursive. Note if SCC contains more than two
            // nodes it has to be recursive, however this test also works for
            // a single node that is recursive.
            result.is_recursive = true;
          }
          break;
        }
        default:
          break;
      }
    }
  }
  // We deliberately only insert the result here. After we contracted the SCC
  // in the graph, the graph should be a DAG. Hence we shouldn't need to mark
  // nodes visited as we can never return to them. By inserting them here
  // we will go in an infinite loop if the SCC is not correct.
  return analysis_cache_[scc] = result;
}

void ListAllFields(const Descriptor* d,
                   std::vector<const FieldDescriptor*>* fields) {
  // Collect sub messages
  for (int i = 0; i < d->nested_type_count(); i++) {
    ListAllFields(d->nested_type(i), fields);
  }
  // Collect message level extensions.
  for (int i = 0; i < d->extension_count(); i++) {
    fields->push_back(d->extension(i));
  }
  // Add types of fields necessary
  for (int i = 0; i < d->field_count(); i++) {
    fields->push_back(d->field(i));
  }
}

void ListAllFields(const FileDescriptor* d,
                   std::vector<const FieldDescriptor*>* fields) {
  // Collect file level message.
  for (int i = 0; i < d->message_type_count(); i++) {
    ListAllFields(d->message_type(i), fields);
  }
  // Collect message level extensions.
  for (int i = 0; i < d->extension_count(); i++) {
    fields->push_back(d->extension(i));
  }
}

void ListAllTypesForServices(const FileDescriptor* fd,
                             std::vector<const Descriptor*>* types) {
  for (int i = 0; i < fd->service_count(); i++) {
    const ServiceDescriptor* sd = fd->service(i);
    for (int j = 0; j < sd->method_count(); j++) {
      const MethodDescriptor* method = sd->method(j);
      types->push_back(method->input_type());
      types->push_back(method->output_type());
    }
  }
}

bool GetBootstrapBasename(const Options& options, const TProtoStringType& basename,
                          TProtoStringType* bootstrap_basename) {
  if (options.opensource_runtime) {
    return false;
  }

  std::unordered_map<TProtoStringType, TProtoStringType> bootstrap_mapping{
      {"net/proto2/proto/descriptor",
       "net/proto2/internal/descriptor"},
      {"net/proto2/compiler/proto/plugin",
       "net/proto2/compiler/proto/plugin"},
      {"net/proto2/compiler/proto/profile",
       "net/proto2/compiler/proto/profile_bootstrap"},
  };
  auto iter = bootstrap_mapping.find(basename);
  if (iter == bootstrap_mapping.end()) {
    *bootstrap_basename = basename;
    return false;
  } else {
    *bootstrap_basename = iter->second;
    return true;
  }
}

bool IsBootstrapProto(const Options& options, const FileDescriptor* file) {
  TProtoStringType my_name = StripProto(file->name());
  return GetBootstrapBasename(options, my_name, &my_name);
}

bool MaybeBootstrap(const Options& options, GeneratorContext* generator_context,
                    bool bootstrap_flag, TProtoStringType* basename) {
  TProtoStringType bootstrap_basename;
  if (!GetBootstrapBasename(options, *basename, &bootstrap_basename)) {
    return false;
  }

  if (bootstrap_flag) {
    // Adjust basename, but don't abort code generation.
    *basename = bootstrap_basename;
    return false;
  } else {
    TProtoStringType forward_to_basename = bootstrap_basename;

    // Generate forwarding headers and empty .pb.cc.
    {
      std::unique_ptr<io::ZeroCopyOutputStream> output(
          generator_context->Open(*basename + ".pb.h"));
      io::Printer printer(output.get(), '$', nullptr);
      printer.Print(
          "#ifndef PROTOBUF_INCLUDED_$filename_identifier$_FORWARD_PB_H\n"
          "#define PROTOBUF_INCLUDED_$filename_identifier$_FORWARD_PB_H\n"
          "#include \"$forward_to_basename$.pb.h\"  // IWYU pragma: export\n"
          "#endif  // PROTOBUF_INCLUDED_$filename_identifier$_FORWARD_PB_H\n",
          "forward_to_basename", forward_to_basename, "filename_identifier",
          FilenameIdentifier(*basename));

      if (!options.opensource_runtime) {
        // HACK HACK HACK, tech debt from the deeps of proto1 and SWIG
        // protocoltype is SWIG'ed and we need to forward
        if (*basename == "net/proto/protocoltype") {
          printer.Print(
              "#ifdef SWIG\n"
              "%include \"$forward_to_basename$.pb.h\"\n"
              "#endif  // SWIG\n",
              "forward_to_basename", forward_to_basename);
        }
      }
    }

    {
      std::unique_ptr<io::ZeroCopyOutputStream> output(
          generator_context->Open(*basename + ".proto.h"));
      io::Printer printer(output.get(), '$', nullptr);
      printer.Print(
          "#ifndef PROTOBUF_INCLUDED_$filename_identifier$_FORWARD_PROTO_H\n"
          "#define PROTOBUF_INCLUDED_$filename_identifier$_FORWARD_PROTO_H\n"
          "#include \"$forward_to_basename$.proto.h\"  // IWYU pragma: "
          "export\n"
          "#endif  // "
          "PROTOBUF_INCLUDED_$filename_identifier$_FORWARD_PROTO_H\n",
          "forward_to_basename", forward_to_basename, "filename_identifier",
          FilenameIdentifier(*basename));
    }

    {
      std::unique_ptr<io::ZeroCopyOutputStream> output(
          generator_context->Open(*basename + ".pb.cc"));
      io::Printer printer(output.get(), '$', nullptr);
      printer.Print("\n");
    }

    {
      std::unique_ptr<io::ZeroCopyOutputStream> output(
          generator_context->Open(*basename + ".pb.h.meta"));
    }

    {
      std::unique_ptr<io::ZeroCopyOutputStream> output(
          generator_context->Open(*basename + ".proto.h.meta"));
    }

    // Abort code generation.
    return true;
  }
}

static bool HasExtensionFromFile(const Message& msg, const FileDescriptor* file,
                                 const Options& options,
                                 bool* has_opt_codesize_extension) {
  std::vector<const FieldDescriptor*> fields;
  auto reflection = msg.GetReflection();
  reflection->ListFields(msg, &fields);
  for (auto field : fields) {
    const auto* field_msg = field->message_type();
    if (field_msg == nullptr) {
      // It so happens that enums Is_Valid are still generated so enums work.
      // Only messages have potential problems.
      continue;
    }
    // If this option has an extension set AND that extension is defined in the
    // same file we have bootstrap problem.
    if (field->is_extension()) {
      const auto* msg_extension_file = field->message_type()->file();
      if (msg_extension_file == file) return true;
      if (has_opt_codesize_extension &&
          GetOptimizeFor(msg_extension_file, options) ==
              FileOptions::CODE_SIZE) {
        *has_opt_codesize_extension = true;
      }
    }
    // Recurse in this field to see if there is a problem in there
    if (field->is_repeated()) {
      for (int i = 0; i < reflection->FieldSize(msg, field); i++) {
        if (HasExtensionFromFile(reflection->GetRepeatedMessage(msg, field, i),
                                 file, options, has_opt_codesize_extension)) {
          return true;
        }
      }
    } else {
      if (HasExtensionFromFile(reflection->GetMessage(msg, field), file,
                               options, has_opt_codesize_extension)) {
        return true;
      }
    }
  }
  return false;
}

static bool HasBootstrapProblem(const FileDescriptor* file,
                                const Options& options,
                                bool* has_opt_codesize_extension) {
  static auto& cache = *new std::unordered_map<const FileDescriptor*, bool>;
  auto it = cache.find(file);
  if (it != cache.end()) return it->second;
  // In order to build the data structures for the reflective parse, it needs
  // to parse the serialized descriptor describing all the messages defined in
  // this file. Obviously this presents a bootstrap problem for descriptor
  // messages.
  if (file->name() == "net/proto2/proto/descriptor.proto" ||
      file->name() == "google/protobuf/descriptor.proto") {
    return true;
  }
  // Unfortunately we're not done yet. The descriptor option messages allow
  // for extensions. So we need to be able to parse these extensions in order
  // to parse the file descriptor for a file that has custom options. This is a
  // problem when these custom options extensions are defined in the same file.
  FileDescriptorProto linkedin_fd_proto;
  const DescriptorPool* pool = file->pool();
  const Descriptor* fd_proto_descriptor =
      pool->FindMessageTypeByName(linkedin_fd_proto.GetTypeName());
  // Not all pools have descriptor.proto in them. In these cases there for sure
  // are no custom options.
  if (fd_proto_descriptor == nullptr) return false;

  // It's easier to inspect file as a proto, because we can use reflection on
  // the proto to iterate over all content.
  file->CopyTo(&linkedin_fd_proto);

  // linkedin_fd_proto is a generated proto linked in the proto compiler. As
  // such it doesn't know the extensions that are potentially present in the
  // descriptor pool constructed from the protos that are being compiled. These
  // custom options are therefore in the unknown fields.
  // By building the corresponding FileDescriptorProto in the pool constructed
  // by the protos that are being compiled, ie. file's pool, the unknown fields
  // are converted to extensions.
  DynamicMessageFactory factory(pool);
  Message* fd_proto = factory.GetPrototype(fd_proto_descriptor)->New();
  fd_proto->ParseFromString(linkedin_fd_proto.SerializeAsString());

  bool& res = cache[file];
  res = HasExtensionFromFile(*fd_proto, file, options,
                             has_opt_codesize_extension);
  delete fd_proto;
  return res;
}

FileOptions_OptimizeMode GetOptimizeFor(const FileDescriptor* file,
                                        const Options& options,
                                        bool* has_opt_codesize_extension) {
  if (has_opt_codesize_extension) *has_opt_codesize_extension = false;
  switch (options.enforce_mode) {
    case EnforceOptimizeMode::kSpeed:
      return FileOptions::SPEED;
    case EnforceOptimizeMode::kLiteRuntime:
      return FileOptions::LITE_RUNTIME;
    case EnforceOptimizeMode::kCodeSize:
      if (file->options().optimize_for() == FileOptions::LITE_RUNTIME) {
        return FileOptions::LITE_RUNTIME;
      }
      if (HasBootstrapProblem(file, options, has_opt_codesize_extension)) {
        return FileOptions::SPEED;
      }
      return FileOptions::CODE_SIZE;
    case EnforceOptimizeMode::kNoEnforcement:
      if (file->options().optimize_for() == FileOptions::CODE_SIZE) {
        if (HasBootstrapProblem(file, options, has_opt_codesize_extension)) {
          GOOGLE_LOG(WARNING) << "Proto states optimize_for = CODE_SIZE, but we "
                          "cannot honor that because it contains custom option "
                          "extensions defined in the same proto.";
          return FileOptions::SPEED;
        }
      }
      return file->options().optimize_for();
  }

  GOOGLE_LOG(FATAL) << "Unknown optimization enforcement requested.";
  // The phony return below serves to silence a warning from GCC 8.
  return FileOptions::SPEED;
}

bool EnableMessageOwnedArena(const Descriptor* /* desc */) {
  return false;
}

}  // namespace cpp
}  // namespace compiler
}  // namespace protobuf
}  // namespace google