Use '%p' directive, and print handle's address if the address is null and the handle doesn't have a name. This fixes the following compilation error: interface/efi/efi_debug.c:334:3: error: '%s' directive argument is null [-Werror=format-overflow=] Signed-off-by: Valentine Barshak <gvaxon@gmail.com> Signed-off-by: Michael Brown <mcb30@ipxe.org>