Unresolved externals when trying to connect to mysql with C++ in Visual Studio 2013

Question

I am trying to connect to mysql with C++ in Visual Studio 2013. I am using Release Configuration. I already put the directories

C:\mysql-5.7.11-winx64\lib C:\Program Files\MySQL\Connector.C++ 1.1\include C:\boost_1_60_0

in C/C++ general-->Additional Dependencies, VC++ Directories and Linker general->Additional Dependencies

and I also added mysqlcppconn-static.lib and libmysql.lib on Linker-->Input.

And now I am getting an error of error LNK1120: 2 unresolved externals
error LNK2001: unresolved external symbol _get_driver_instance
error LNK2001: unresolved external symbol _WinMain@16

How do I fix this? Thanks!

/* Standard C++ includes */
#include <stdlib.h>
#include <iostream>

/*
  Include directly the different
  headers from cppconn/ and mysql_driver.h + mysql_util.h
  (and mysql_connection.h). This will reduce your build time!
*/
#include "mysql_connection.h"

#include <cppconn/driver.h>
#include <cppconn/exception.h>
#include <cppconn/resultset.h>
#include <cppconn/statement.h>
#include <cppconn/prepared_statement.h>

using namespace std;

int main(void)
{
cout << endl;
cout << "Let's have MySQL count from 10 to 1..." << endl;

try {
  sql::Driver *driver;
  sql::Connection *con;
  sql::Statement *stmt;
  sql::ResultSet *res;
  sql::PreparedStatement *pstmt;

  /* Create a connection */
  driver = get_driver_instance();
  con = driver->connect("tcp://127.0.0.1:3306", "root", "root");
  /* Connect to the MySQL test database */
  con->setSchema("test");

  stmt = con->createStatement();
  stmt->execute("DROP TABLE IF EXISTS test");
  stmt->execute("CREATE TABLE test(id INT)");
  delete stmt;

  /* '?' is the supported placeholder syntax */
  pstmt = con->prepareStatement("INSERT INTO test(id) VALUES (?)");
  for (int i = 1; i <= 10; i++) {
    pstmt->setInt(1, i);
    pstmt->executeUpdate();
  }
  delete pstmt;

  /* Select in ascending order */
  pstmt = con->prepareStatement("SELECT id FROM test ORDER BY id ASC");
  res = pstmt->executeQuery();

  /* Fetch in reverse = descending order! */
  res->afterLast();
  while (res->previous())
    cout << "\t... MySQL counts: " << res->getInt("id") << endl;
  delete res;

  delete pstmt;
  delete con;

} catch (sql::SQLException &e) {
  cout << "# ERR: SQLException in " << __FILE__;
  cout << "(" << __FUNCTION__ << ") on line " 
     << __LINE__ << endl;
  cout << "# ERR: " << e.what();
  cout << " (MySQL error code: " << e.getErrorCode();
  cout << ", SQLState: " << e.getSQLState() <<  " )" << endl;
}

cout << endl;

return EXIT_SUCCESS;
}

TriskalJM TriskalJM · Accepted Answer · 2016-03-30T16:46:27

You've got a couple of problems occurring.

The first is that your project settings appear to be expecting a Windows application, not a console application, as evidenced by trying to find the symbol _WinMain@16 instead of main. Double-check your project settings.
The second is that you're trying to link statically, but at least in some versions of mysql, you need to define a preprocessor directive in order for symbols to be visible to the rest of your code. Specifically, _get_driver_instance(), since this was a function added for those linking against the mysql libraries dynamically. Try defining mysqlcppconn_EXPORTS in the project settings and rebuild.

Unresolved externals when trying to connect to mysql with C++ in Visual Studio 2013

1 Answers