Fixes Trac ticket #445 Python DBI driver crash under Windows when fetching rows from cursor on closed connection.

After an ODBC connection is closed the ODBC spec requires that the driver close and free all resources. The crash is actually expected!

Added check for exception for to fetchall so that exceptions raised 
by fetchone are not lost.

Added quick/simply fix to check connection status on fetch. The old
approach for the original IngresDBI driver was to maintain a dict of
cursors in the connection and when the connection was closed, close
all the cursors. This is not present in this pure C extension.
Really should return back to that technique. Checking the connection
for each single fetch is a needless overhead.

NOTE problem did not occur under Linux, it appears the Unix Ingres
ODBC driver (CLI manager) returns errors when a cursor for a closed
connection is used (or we just got lucky).


git-svn-id: http://code.ingres.com/ingres/drivers/python/main@2112 45b5d43f-8932-4c86-835a-3654e5842839

Author: clach04

dbi/iidbiconn.c

@@ -435,7 +435,6 @@ dbi_connect( IIDBI_DBC *pdbc)
 /*{
 ** Name: dbi_connectionClose - Issue a rollback and close the connection.
 **
-Corrected driver to call with an r3 installatioCorrected driver to call with an r3 installation
 ** Inputs:
 **     None.
 **

dbi/iidbicurs.c

@@ -175,7 +175,7 @@ RETCODE BindParameters(IIDBI_STMT *pstmt, unsigned char isProc);
 ** Name: dbi_cursorClose - Close the cursor
 **
 ** Description:
-**     Close the cursor
+**     Close the ODBC cursor (not the DBI cursor)
 **
 ** Inputs:
 **     None.

dbi/ingresdbi.c

@@ -237,6 +237,24 @@
 **      Trac ticket 446 error on execute with empty parm iterable
 **      Created IIDBI_IsTrue(), which is now used to check (bind) 
 **      parameters for execute and executemany.
+**  20-Oct-2009 (clach04)
+**      Trac ticket 445 crash under Windows when fetching rows from cursor
+**      on closed connection.
+**      Added check for exception for to fetchall so that exceptions raised
+**      by fetchone are not lost.
+**      Added quick/simply fix to check connection status on fetch. The old
+**      approach for the original IngresDBI driver was to maintain a dict of
+**      cursors in the connection and when the connection was closed, close
+**      all the cursors. This is not present in this pure C extension.
+**      Really should return back to that technique. Checking the connection
+**      for each single fetch is a needless overhead.
+**      NOTE problem did not occur under Linux, it appears the Unix Ingres
+**      ODBC driver (CLI manager) returns errors when a cursor for a closed
+**      connection is used. The Windows Ingres ODBC driver crashes. The
+**      Windows crash is actually expected behavior based on the ODBC spec
+**      calls to (for instance) fetch on a closed session will be using
+**      invalid pointers as the driver is responsible for free'ing each
+**      connection/cursror resource. Other Windows ODBC drivers also crash.
 **/
 
 static PyObject *IIDBI_Warning;
@@ -4314,9 +4332,27 @@ static PyObject *IIDBI_cursorFetch(IIDBI_CURSOR *self)
     PyObject *exception;
     char *errMsg;
     int result = FALSE;
+    IIDBI_CONNECTION *connection;
 
     DBPRINTF(DBI_TRC_RET)("%p: IIDBI_cursorFetch {{{1\n", self);
 
+    connection = self->connection;
+    /* Py_INCREF(connection); we don't intend to use this and we have the GIL so no need to increment */
+    if (connection == (IIDBI_CONNECTION *)Py_None)
+    {
+        exception = IIDBI_InternalError; 
+        errMsg = "Invalid connection object";
+        result = IIDBI_handleError((PyObject *)self, exception, errMsg);
+        goto errorExit;
+    }
+    else
+    {
+        if (connection->closed && !self->closed)
+        {
+            IIDBI_cursorClose(self); /* FIXME check return and exceptions...*/
+        }
+    }
+
     if (self->closed)
     {
         exception = IIDBI_InterfaceError; 
@@ -4929,6 +4965,7 @@ static PyObject *IIDBI_cursorFetchAll(IIDBI_CURSOR *self)
 {
     PyObject *list = NULL;
     PyObject *row = NULL;
+    PyObject *lastexception = NULL;
     int dbistat = 0;
     PyObject *exception;
     char *errMsg;
@@ -4956,10 +4993,18 @@ static PyObject *IIDBI_cursorFetchAll(IIDBI_CURSOR *self)
 
     if (row == NULL)
     {
-        DBPRINTF(DBI_TRC_STAT)("fetchall call to IIDBI_cursorFetch got null\n");
-        exception = IIDBI_DatabaseError;
-        errMsg = "Error fetching rows";
-        result = IIDBI_handleError((PyObject *)self, exception, errMsg);
+        lastexception = PyErr_Occurred();
+        if (lastexception == NULL)
+        {
+            if (PyErr_GivenExceptionMatches(lastexception, IIDBI_Error))
+            {
+                /* We have an unhandled (non-IngresDBI) exception */
+                DBPRINTF(DBI_TRC_STAT)("fetchall call to IIDBI_cursorFetch got null\n");
+                exception = IIDBI_DatabaseError;
+                errMsg = "Error fetching rows";
+                result = IIDBI_handleError((PyObject *)self, exception, errMsg);
+            }
+        }
         goto errorExit;
     }
 
@@ -5306,7 +5351,7 @@ static PyObject *IIDBI_connClose(IIDBI_CONNECTION *self)
 ** Name: IIDBI_cursorClose
 **
 ** Description:
-**     Close a cursor object.
+**     Close a DBI cursor object.
 **
 ** Inputs:
 **     self - cursor object.