Segfault in OCIHandleFree for a statement after closing the connection

Question

my app has lots of statements allocated at any one time.
if the oracle connection is lost (due to temporary network problems, etc), my app detects the connection loss. when the connection is lost, the app destroys the old connection, and then tries to create a new connection. once it gets a new connection, the app goes through and destroys its old statements.
but, sometimes a segfault occurs in the call to OCIHandleFree.
when the old connection is destroyed, does it also free up all memory allocated for the statement too? so I'm basically doing a double free when I try to call OCIHandleFree on the statements?
btw, by 'destroy old connection': the app is using the oralib wrapper around the oci library. when an oralib instance is destroyed, it first switches the server handle to OCI_ATTR_NONBLOCKING_MODE, then calls OCISessionEnd, OCIServerDetach, then OCIHandleFree for each of the svc_context, session, error, and server handles.
after that, a new oralib instance is created, which makes a new connection to oracle.
then after that, the old statements will all be passed to OCIHandleFree.
is there any obvious problem with that? thanks!

Answer 1

It is very important to close them as you might have a resource leak. Many people think that since Java is garbage collected, they don't have to worry about memory. While this is true, it should not be take to the extreme.
public void method throws SQLException
     Connection conn = DriverManager.getConnection();
     Statement stmnt  = conn.createStatement();
     ResultSet results = stmnt.executeQuery("SELECT * FROM table;");
     results.close();
     stmnt.close();
     conn.close();
}The above code looks correct, but in fact it is not completely correct. It is not completely correct, because the release of resources is not ensured. If an exception occurs midway, it's possible that the resources will not be properly released.
Here is the correct code.
public void method throws SQLException
     Connection conn = null;
     Statement stmnt = null;
     ResultSet results = null;
     try
          conn = DriverManager.getConnection();
          stmnt = conn.createStatement();
          results = stmnt.executeQuery("SELECT * FROM table;");
     finally
          if ( results ! = null )
               results.close();
          if ( stmnt != null )
               stmnt.close();
          if ( conn != null )
               conn.close();
}The finally block ensures that even if an exception occurs we will release our resources. You have to make sure they're not null to avoid NullPointerExceptions.