math: fix expf(-NAN) and exp2f(-NAN) to return -NAN instead of 0

expf(-NAN) was treated as expf(-large) which unconditionally
returns +0, so special case +-NAN.
reported by Petr Hosek.

diff --git a/src/math/exp2f.c b/src/math/exp2f.c
index cf6126e..296b634 100644 (file)
--- a/src/math/exp2f.c
+++ b/src/math/exp2f.c
@@ -91,6 +91,8 @@ float exp2f(float x)
        /* Filter out exceptional cases. */
        ix = u.i & 0x7fffffff;
        if (ix > 0x42fc0000) {  /* |x| > 126 */
+               if (ix > 0x7f800000) /* NaN */
+                       return x;
                if (u.i >= 0x43000000 && u.i < 0x80000000) {  /* x >= 128 */
                        x *= 0x1p127f;
                        return x;

diff --git a/src/math/expf.c b/src/math/expf.c
index 16e9afe..feee2b0 100644 (file)
--- a/src/math/expf.c
+++ b/src/math/expf.c
@@ -39,6 +39,8 @@ float expf(float x)
 
        /* special cases */
        if (hx >= 0x42aeac50) {  /* if |x| >= -87.33655f or NaN */
+               if (hx > 0x7f800000) /* NaN */
+                       return x;
                if (hx >= 0x42b17218 && !sign) {  /* x >= 88.722839f */
                        /* overflow */
                        x *= 0x1p127f;