Fix trace_dbg to tolerate call without any value parameters

Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>

diff --git a/src/utils.rs b/src/utils.rs
index f12ec31f0649be244d00801ce4545ce8fbbccdf8..79cc592bb62749e8c698e57232770e768941a6d6 100644 (file)
--- a/src/utils.rs
+++ b/src/utils.rs
@@ -332,6 +332,7 @@ fn matches_doesnot_test() {
 macro_rules! trace_dbg {
   ($msg:expr $(,$val:expr)*) => {
     if log_enabled!(log::Level::Trace) {
+      #[allow(unused_mut)]
       let mut buf = format!("{}", &$msg);
       $( write!(&mut buf, " {}={:?}", stringify!($val), &$val).unwrap(); )*
       trace!("{}", buf);