return number of bytes output

src/libbio/bvprint.c

diff --git a/src/libbio/bvprint.c b/src/libbio/bvprint.c
index 84a2ff2..60b105f 100644
--- a/src/libbio/bvprint.c
+++ b/src/libbio/bvprint.c
@@ -32,8 +32,7 @@
 	fmtlocaleinit(&f, nil, nil, nil);
 	n = fmtvprint(&f, fmt, arg);
 	bp->ocount = (char*)f.to - (char*)f.stop;
+	if(n == 0)
+		n = f.nfmt;
 	return n;
 }
-
-
-