math: add fma TODO comments about the underflow issue

[musl] / src / math / fmal.c

diff --git a/src/math/fmal.c b/src/math/fmal.c
index ccbe434..87e30fc 100644 (file)
--- a/src/math/fmal.c
+++ b/src/math/fmal.c
@@ -262,6 +262,8 @@ long double fmal(long double x, long double y, long double z)
                /*
                 * There is no need to worry about double rounding in directed
                 * rounding modes.
+                * TODO: underflow is not raised correctly, example in downward rounding:
+                * fmal(0x1.0000000001p-16000L, 0x1.0000000001p-400L, -0x1p-16440L)
                 */
                fesetround(oround);
                adj = r.lo + xy.lo;