--- a/libm/s_floor.c
+++ b/libm/s_floor.c
@@ -81,3 +81,18 @@ libm_hidden_proto(floor)
 	return x;
 }
 libm_hidden_def(floor)
+
+
+libm_hidden_proto(trunc)
+double
+trunc(double x)
+{
+	if (!finite (x))
+		return x;
+
+	if (x < 0.0)
+		return - floor (-x);
+	else
+		return floor (x);
+}
+libm_hidden_def(trunc)
