c++ Login Function

#include <iostream>
#include <string>
using namespace std;

int ret, retu;
string pass_in, user_in, log;
string user = "Simon";
string pass = "test";

int checkLogin() {
  cout << "Username: ";
  getline (cin, user_in);
  cout << "Password: ";
  getline (cin, pass_in);
  if(user_in == "" || pass_in == "") {
             ret = 2;
  }
  else {
             if(user_in == user && pass_in == pass) {
                        ret = 0;
             }
             else {
                        ret = 1;
             }
  }
  return ret;
}
string retLogin(int ret) {
  switch(ret) {
              case 0:
                   log = "Access Granted.\n";
                   break;
              case 1:
                   log = "Access Denied.\n";
                   break;
              case 2:
                   log = "Fill in all fields.\n";
                   break;
              default:
                   log = "Access Denied.\n";
                   break;
  }
  return log;
}

int main ()
{
  ret = checkLogin();
  cout << retLogin(ret);
  cin.get();
}

#include <iostream>
#include <string>
using namespace std;
 
int ret, retu;
string pass_in, user_in, log;
string user = "Simon";
string pass = "test";
 
int checkLogin() {
  cout << "Username: ";
  getline (cin, user_in);
  cout << "Password: ";
  getline (cin, pass_in);
  if(user_in == "" || pass_in == "") {
             ret = 2;
  }
  else {
             if(user_in == user && pass_in == pass) {
                        ret = 0;
             }
             else {
                        ret = 1;
             }
  }
  return ret;
}
string retLogin(int ret) {
  switch(ret) {
              case 0:
                   log = "Access Granted.\n";
                   break;
              case 1:
                   log = "Access Denied.\n";
                   break;
              case 2:
                   log = "Fill in all fields.\n";
                   break;
              default:
                   log = "Access Denied.\n";
                   break;
  }
  return log;
}
 
int main ()
{
  ret = checkLogin();
  cout << retLogin(ret);
  cin.get();
}

int main ()
{
  do
  {
     ret = checkLogin();
     cout << retLogin(ret);
     cin.get();
   }
   while(ret == 1 OR ret == 2)
}

int main ()
{
  do
  {
     ret = checkLogin();
     cout << retLogin(ret);
     cin.get();
   }
   while(ret == 1 OR ret == 2)
}