fix aliasing-based undefined behavior in mbsrtowcs

[musl] / src / math / __rem_pio2f.c

diff --git a/src/math/__rem_pio2f.c b/src/math/__rem_pio2f.c
index 838e1fc..4473c1c 100644 (file)
--- a/src/math/__rem_pio2f.c
+++ b/src/math/__rem_pio2f.c
@@ -22,12 +22,19 @@
 
 #include "libm.h"
 
+#if FLT_EVAL_METHOD==0 || FLT_EVAL_METHOD==1
+#define EPS DBL_EPSILON
+#elif FLT_EVAL_METHOD==2
+#define EPS LDBL_EPSILON
+#endif
+
 /*
  * invpio2:  53 bits of 2/pi
  * pio2_1:   first 25 bits of pi/2
  * pio2_1t:  pi/2 - pio2_1
  */
 static const double
+toint   = 1.5/EPS,
 invpio2 = 6.36619772367581382433e-01, /* 0x3FE45F30, 0x6DC9C883 */
 pio2_1  = 1.57079631090164184570e+00, /* 0x3FF921FB, 0x50000000 */
 pio2_1t = 1.58932547735281966916e-08; /* 0x3E5110b4, 0x611A6263 */
@@ -35,7 +42,8 @@ pio2_1t = 1.58932547735281966916e-08; /* 0x3E5110b4, 0x611A6263 */
 int __rem_pio2f(float x, double *y)
 {
        union {float f; uint32_t i;} u = {x};
-       double tx[1],ty[1],fn;
+       double tx[1],ty[1];
+       double_t fn;
        uint32_t ix;
        int n, sign, e0;
 
@@ -43,8 +51,7 @@ int __rem_pio2f(float x, double *y)
        /* 25+53 bit pi is good enough for medium size */
        if (ix < 0x4dc90fdb) {  /* |x| ~< 2^28*(pi/2), medium size */
                /* Use a specialized rint() to get fn.  Assume round-to-nearest. */
-               fn = x*invpio2 + 0x1.8p52;
-               fn = fn - 0x1.8p52;
+               fn = (double_t)x*invpio2 + toint - toint;
                n  = (int32_t)fn;
                *y = x - fn*pio2_1 - fn*pio2_1t;
                return n;