math: Fix UB in expm1

Building with ubsan triggers:

UBSAN: Undefined behaviour in ../sysdeps/ieee754/dbl-64/s_expm1.c:242:4 left shift of 4294967271 by 20 cannot be represented in type 'int'

Since at the time k is always positive, just cast to uint32_t.

diff --git a/sysdeps/ieee754/dbl-64/s_expm1.c b/sysdeps/ieee754/dbl-64/s_expm1.c
index 1cafeca9c02381a1ef8bdce21b0f45dfe879ce9f..557178f33d1d98b11c8deb31ccae6f4c1a3da749 100644 (file)
--- a/sysdeps/ieee754/dbl-64/s_expm1.c
+++ b/sysdeps/ieee754/dbl-64/s_expm1.c
@@ -239,7 +239,7 @@ __expm1 (double x)
          uint32_t high;
          y = one - (e - x);
          GET_HIGH_WORD (high, y);
-         SET_HIGH_WORD (y, high + (k << 20));  /* add k to y's exponent */
+         SET_HIGH_WORD (y, high + ((uint32_t)k << 20));  /* add k to y's exponent */
          return y - one;
        }
       t = one;