diff -durpN postgresql.3/doc/src/sgml/libpq.sgml postgresql.4/doc/src/sgml/libpq.sgml
--- postgresql.3/doc/src/sgml/libpq.sgml	2012-11-30 09:29:49.703286090 +0100
+++ postgresql.4/doc/src/sgml/libpq.sgml	2013-01-02 16:54:43.783565292 +0100
@@ -588,6 +588,27 @@ void PQfinish(PGconn *conn);
      </listitem>
     </varlistentry>

+    <varlistentry id="libpq-pqfinishsafe">
+     <term><function>PQfinishSafe</function><indexterm><primary>PQfinishSafe</></></term>
+     <listitem>
+      <para>
+       A macro that calls <function>PQfinish</function> and sets
+       the pointer to NULL afterwards.
+<synopsis>
+#define PQfinishSafe(conn) do { PQfinish(conn); conn = NULL; } while (0)
+</synopsis>
+      </para>
+
+      <para>
+       The <structname>PGconn</> pointer (being NULL) is safe to use
+       after this macro. Every function that deals with a
+       <structname>PGconn</> pointer considers a non-NULL pointer as valid.
+       Using a stale pointer may result in a crash. Setting the pointer
+       to NULL makes calling such functions a no-op instead.
+      </para>
+     </listitem>
+    </varlistentry>
+
     <varlistentry id="libpq-pqreset">
      <term><function>PQreset</function><indexterm><primary>PQreset</></></term>
      <listitem>
@@ -2753,6 +2774,29 @@ void PQclear(PGresult *res);
        </para>
       </listitem>
      </varlistentry>
+
+     <varlistentry id="libpq-pqclearsafe">
+      <term><function>PQclearSafe</function><indexterm><primary>PQclearSafe</></></term>
+      <listitem>
+       <para>
+        A macro to call <function>PQclear</function> and set
+        the pointer to NULL afterwards.
+<synopsis>
+#define PQclearSafe(res) do { PQclear(res); res = NULL; } while (0)
+</synopsis>
+       </para>
+
+       <para>
+        Calling <function>PQclear</function> leaves a stale
+        <structname>PGresult</structname> pointer. Calling
+        functions that deal with <structname>PGresult</structname>
+        objects afterwards may result in a crash. Setting the
+        <structname>PGresult</structname> pointer to NULL makes
+        calling such functions a no-op instead.
+       </para>
+      </listitem>
+     </varlistentry>
+
     </variablelist>
    </para>
   </sect2>
diff -durpN postgresql.3/src/interfaces/libpq/libpq-fe.h postgresql.4/src/interfaces/libpq/libpq-fe.h
--- postgresql.3/src/interfaces/libpq/libpq-fe.h	2013-01-02 09:19:03.929522614 +0100
+++ postgresql.4/src/interfaces/libpq/libpq-fe.h	2013-01-02 16:52:41.236683245 +0100
@@ -256,6 +256,9 @@ extern PGconn *PQsetdbLogin(const char *
 /* close the current connection and free the PGconn data structure */
 extern void PQfinish(PGconn *conn);

+/* macro to close the current connection and set the conn pointer to NULL */
+#define PQfinishSafe(conn) do { PQfinish(conn); conn = NULL; } while (0)
+
 /* get info about connection options known to PQconnectdb */
 extern PQconninfoOption *PQconndefaults(void);

@@ -472,6 +475,9 @@ extern int	PQsendDescribePortal(PGconn *
 /* Delete a PGresult */
 extern void PQclear(PGresult *res);

+/* Macro to delete a PGresult and set the res pointer to NULL */
+#define PQclearSafe(res) do { PQclear(res); res = NULL; } while (0)
+
 /* For freeing other alloc'd results, such as PGnotify structs */
 extern void PQfreemem(void *ptr);