weird behavior of stringstream and RecordWriter (c++ experts, please help)

[Chenyun Dai]

Hi C++ experts,

I have a weird behavior of my c++ code:

File* csv_file = File::OpenOrDie(FLAGS_tagless_csv_output_file, "w");

  RecordWriter csv_writer(csv_file);

  while (database_->NextResult()) {

    int64 attribute_id = database_->GetInt64(0);

    int64 owner_account_id = database_->GetInt64(1);

    int64 client_account_id = database_->GetInt64(2);

    stringstream output_line;

    output_line << attribute_id << "," << owner_account_id << ","

                << client_account_id << "\n";

    LOG(INFO) << output_line.str();

    string test = output_line.str();

    csv_writer.Write(test);

  }

  CHECK(csv_writer.Close());

  // Ensure query executed successfully.                                                                                     

  CHECK(database_->Finish());

the above code compiled successfully.

However,

File* csv_file = File::OpenOrDie(FLAGS_tagless_csv_output_file, "w");

  RecordWriter csv_writer(csv_file);

  while (database_->NextResult()) {

    int64 attribute_id = database_->GetInt64(0);

    int64 owner_account_id = database_->GetInt64(1);

    int64 client_account_id = database_->GetInt64(2);

    stringstream output_line;

    output_line << attribute_id << "," << owner_account_id << ","

                << client_account_id << "\n";

    LOG(INFO) << output_line.str();

    csv_writer.Write(output_line.str());

  }

  CHECK(csv_writer.Close());

  // Ensure query executed successfully.                                                                                     

  CHECK(database_->Finish());

  return true;

won't work with following compilation error:

./file/base/recordio.h:1401:3: error: implicit instantiation of undefined template 'ERROR_TYPE_MUST_BE_POD<false>'

  ENFORCE_POD(T);

  ^

./base/type_traits.h:418:14: note: expanded from macro 'ENFORCE_POD'

           = sizeof(ERROR_TYPE_MUST_BE_POD<                               \

             ^

./file/base/recordio.h:884:12: note: in instantiation of function template specialization 'RecordWriter::DispatchWrite<std::basic_string<char> >' requested here

    return DispatchWrite(value, &value);

           ^

contentads/usertargeting/dashboard/tagless/tagless-dashboard-extraction.cc:82:16: note: in instantiation of function template specialization 'RecordWriter::Write<std::basic_string<char> >' requested here

    csv_writer.Write(output_line.str());

               ^

./base/type_traits.h:414:30: note: template is declared here

template <bool IsPod> struct ERROR_TYPE_MUST_BE_POD;

                             ^

1 error generated.

why this error exits? Does it have anything to do with the difference between std::string and google3 string????? If so, how to avoid?

Cheers,

Chenyun