Associate a user-defined error structure with the connection

• Use the mi_set_connection_user_data() function in the calling function to bind the structure to a connection descriptor (an MI_CONNECTION structure).
• Use the mi_get_connection_user_data() function in the callback to obtain the structure that is bound to the connection descriptor.

int main (argc, argv)
   int argc;
   char **argv;
{
   MI_CONNECTION *conn = NULL;
   MI_CALLBACK_HANDLE *cback_hndl;
   char query[300];
   mi_integer ret;
   DB_ERROR_BUF error_buff;

   conn = mi_open(argv[1], NULL, NULL);
   if ( conn == NULL )
      /* do something appropriate */
      ...
   cback_hndl = mi_register_callback(conn, MI_Exception,
      (MI_VOID)clntexcpt_callback2, NULL, NULL);
   ret = mi_set_connection_user_data(conn,
      (MI_VOID)&error_buff);
   if ( ret == MI_ERROR )
      /* do something appropriate */
      ...
   ret = send_command(conn, query);
   if ( ret == MI_ERROR)
      {
      fprintf(stderr, "MI_Exception: level = %d",
         error_buff.error_level);
      fprintf(stderr, "SQLSTATE='%s'\n",
         error_buff.sqlstate);
      fprintf(stderr, "message = '%s'\n",
         error_buff.error_msg);
      }
   /* do something appropriate */
   ...
}

void clntexcpt_callback2(event_type, conn, event_info,
      user_data)
   MI_EVENT_TYPE event_type;
   MI_CONNECTION *conn; /* user-defined error buffer here */
   void *event_info;
   void *user_data;
{
   DB_ERROR_BUF *error_buf

   mi_get_connection_user_data(conn, (void **)&error_buf)
   error_buf->error_type = event_type;
   if ( event_type == MI_Exception )
      {
      error_buf->error_level = mi_error_level(event_info);
      mi_error_sql_state(event_info, error_buf->sqlstate, 6);
      mi_errmsg(event_info, error_buf->error_msg, MSG_SIZE-1);
      }
   else
      fprintf(stderr,
         "Warning! clntexcpt_callback2() fired for event "
         "%d", event_type);
   return;
}