warning when built w/o concurrent-output

diff --git a/BuildFlags.hs b/BuildFlags.hs
index bfdbb00d68f830f1234de840251148cb86bd1b25..dfebedb61fce7a38552faf4bca59a339a68be292 100644 (file)
--- a/BuildFlags.hs
+++ b/BuildFlags.hs
@@ -67,6 +67,8 @@ buildFlags = filter (not . null)
 #endif
 #ifdef WITH_CONCURRENTOUTPUT
        , "ConcurrentOutput"
+#else
+#warning Building without ConcurrentOutput
 #endif
 #ifdef WITH_DNS
        , "DNS"