CODEWITHSUNDEEP
c++exception
Otto Müller
Otto Müller

Reputation: 1

MySQL C++ connector loop

#include <iostream>
#include <sstream>
#include <string>

#include <mysql_connection.h>
#include <mysql_driver.h>
#include <mysql_error.h>

#include <cppconn/driver.h>
#include <cppconn/exception.h>

using namespace std;
using namespace sql;
using namespace mysql;
int main()
{
 Connection* con = nullptr;
 MySQL_Driver *driver = get_mysql_driver_instance();
 const SQLString server = "server.de";
 const SQLString user = "userName";
 const SQLString password = "password";

 while (1)
 {
  try {
   con = driver->connect(server, user, password);
  }
  catch (SQLException e) {
   printf("Fehler SQL Connect: %s \n", e.getSQLStateCStr());
   delete driver;
  }
  catch (...) {
   cerr << "Fehler SQL Connnect" << endl;
  }
  if (con)
  {
   con->close();
   delete con;
  }
  boost::detail::Sleep(5000);
 }
 return 0;
}

I wrote this code and hoped it would run in an endless loop even, if the connect statement failed. What happens is: After the first time the connect failes it goes to the first catch statement and writes "Fehler SQL Connect: HY000" as I expect. The next time the connect failes the program breakes and in VS2017 I see 'te923021119.exe has triggered a breakpoint' Why doesn't the program try to connect endlessly? ncb

Upvotes: 0

Views: 91

Answers (1)

AbbysSoul
AbbysSoul

Reputation: 403

In your exception handled you call delete driver; This call destroys the driver object. It is not clear if it the right thing to do - as it is not clear if get_mysql_driver_instance() gives you the ownership of a dynamically allocated object with new. But regardless - in the next iteration your program attempts to use driver - which has been destroyed. So - methinks don't call delete driver;. Better yet - use smart pointers to communicate ownership semantic clearly. std::unique_ptr may be a good option.

Upvotes: 1

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