[build] Fix compiler warnings on some gcc versions

xfer_buffer() uses intf_get_dest_op() to obtain the destination
interface for xfer_deliver(), in order to check that this is the same
interface which provides xfer_buffer().  The return value from
intf_get_dest_op() (which contains the actual method implementing
xfer_deliver()) is not used.

On some gcc versions, this triggers a "value computed is not used"
warning, since the explicit type cast included within the
intf_get_dest_op() macro is treated as a "value computed".

Fix by explicitly casting the result of intf_get_dest_op() to void.

Reported-by: Matthew Helton <mwhelton@gmail.com>
Reported-by: James A. Peltier <jpeltier@sfu.ca>
Signed-off-by: Michael Brown <mcb30@ipxe.org>

diff --git a/src/core/xferbuf.c b/src/core/xferbuf.c
index afc72ae765582b83b9fb14d56f89a33897f1e26a..240118557b27440f9a5053e915f2b4980b33ee90 100644 (file)
--- a/src/core/xferbuf.c
+++ b/src/core/xferbuf.c
@@ -309,7 +309,7 @@ struct xfer_buffer * xfer_buffer ( struct interface *intf ) {
        /* Check that this operation is provided by the same interface
         * which handles xfer_deliver().
         */
-       intf_get_dest_op ( intf, xfer_deliver, &xfer_deliver_dest );
+       ( void ) intf_get_dest_op ( intf, xfer_deliver, &xfer_deliver_dest );
 
        if ( op && ( dest == xfer_deliver_dest ) ) {
                xferbuf = op ( object );