toupper, tolower, strlen и кириллица - C++

int _tmain(int argc, _TCHAR* argv[])
  {
  setlocale(LC_ALL, "Russian");
  wchar_t str[80];
  wcscpy_s(str, L"тест");
  std::wcout << str << endl; 
  for (size_t i = 0; str[i]; ++i)
    str[i] = towupper(str[i]);
  std::wcout << str << endl;
  return 0;
  }