C++ exception-less C-style error handling

err_code.cpp

#include <iostream>
#include <string>
#include <system_error>

struct PersonError {
  enum {
    TOO_OLD = 1,
    NAME_TOO_SHORT = 2,
  };
};

class PersonCategory : public std::error_category {
 public:
  const char *name() const noexcept override { return "Person"; }

  std::string message(int err_value) const override {
    switch (err_value) {
      case PersonError::TOO_OLD:
        return "Person too old";
      case PersonError::NAME_TOO_SHORT:
        return "Person's name is too short";
      default:
        return "Unknown error value";
    }
  }
};

static const PersonCategory PERSON_CATEGORY;

class Person {
 public:
  Person(std::string name, int age, std::error_code &err)
      : name_(name), age_(age) {
    if (age > 100) {
      err = std::error_code{PersonError::TOO_OLD, PERSON_CATEGORY};
      return;
    }
    if (name.size() < 2) {
      err = std::error_code{PersonError::NAME_TOO_SHORT, PERSON_CATEGORY};
      return;
    }
  }

 private:
  std::string name_;
  int age_;
};

void handlePeople(std::error_code &err) {
  for (int i = 0; i < 101; i++) {
    Person bob{"Bob", i, err};
    if (err) return;
  }
}

int main() {
  std::error_code err{};
  handlePeople(err);
  if (err) {
    std::cout << "Error: " << err.message() << "\n";
    return -1;
  }

  return 0;
}