Two error-reporting conventions for a command-parser

I need to implement some function and I would like to report about a fail made inside a function. If function doesn't fail I need to get a some result (for example, std::string). I see two ways to implement function:

// 1. report with exception
std::string foo() {
  std::string ret;
  ... // solving str
  if (is_fail())
    throw ...;
  return ret;
}

// 2. report with return value
bool foo(const std::string &str) {
  ... // solving str
  return is_fail();
}

What way is more preferable and why? Or, maybe, there is the best way I didn't write?

The following is the original code for both cases.

namespace fs = boost::filesystem;
namespace po = boost::program_options;

/////////////////////////////////////////////////
// 1. report with exception
fs::path parse(int argc, char *argv[]) {
  fs::path ret;
  po:options_description desc("Program options");
  desc.add_options()
    ("help,h", "Show help")
    ("output,o", po::value<fs::path>(&ret), "Output folder")
    ;
  po::variables_map vm;
  const po::parsed_options opts = po::command_line_parser(argc, argv).options(desc).run();
  po::store(opts, vm);
  ...
  return ret;
}

int main(int argc, char *argv[]) {
  fs::path output;
  try {
    output = parse(argc, argv);
  } catch (const std::exception &e) { 
    cout << e.what() << std::endl;
    return 1;
  }
  ...
}

//////////////////////////////////////////////////////
// 2. report with return value
bool parse(int argc, char *argv[], fs::path &output) {
  po:options_description desc("Program options");
  desc.add_options()
    ("help,h", "Show help")
    ("output,o", po::value<fs::path>(&output), "Output folder")
    ;
  po::variables_map vm;
  try {
    const po::parsed_options opts = po::command_line_parser(argc, argv).options(desc).run();
    po::store(opts, vm);
  } catch (const std::exception &e) { 
    cout << e.what() << endl;
    return false; 
  }
  ...
  return true;
}

int main(int argc, char *argv[]) {
  fs::path output;
  if (!parse(argc, argv, output))
    return 1;
  ...
}

Actually speed is not critical here and parse function performs just once. Maybe, there is not big deal to choose right answer. However, I would like to know what good practice is.