Fix null pointer dereference in "\c" psql command.

nmisch · nmisch · commit 6087bf1a198e · 2015-07-08T20:44:27.000-04:00
The psql crash happened when no current connection existed.  (The second
new check is optional given today's undocumented NULL argument handling
in PQhost() etc.)  Back-patch to 9.0 (all supported versions).
diff --git a/src/bin/psql/command.c b/src/bin/psql/command.c
@@ -1260,7 +1260,8 @@ do_connect(char *dbname, char *user, char *host, char *port)
 	 * syntax.
 	 */
 	keep_password =
-		((strcmp(user, PQuser(o_conn)) == 0) &&
+		(o_conn &&
+		 (strcmp(user, PQuser(o_conn)) == 0) &&
 		 (!host || strcmp(host, PQhost(o_conn)) == 0) &&
 		 (strcmp(port, PQport(o_conn)) == 0) &&
 		 !has_connection_string);
