fix aliasing-based undefined behavior in mbsrtowcs

[musl] / src / math / copysign.c

diff --git a/src/math/copysign.c b/src/math/copysign.c
index 038b8b4..b09331b 100644 (file)
--- a/src/math/copysign.c
+++ b/src/math/copysign.c
@@ -1,11 +1,8 @@
 #include "libm.h"
 
 double copysign(double x, double y) {
-       union dshape ux, uy;
-
-       ux.value = x;
-       uy.value = y;
-       ux.bits &= (uint64_t)-1>>1;
-       ux.bits |= uy.bits & (uint64_t)1<<63;
-       return ux.value;
+       union {double f; uint64_t i;} ux={x}, uy={y};
+       ux.i &= -1ULL/2;
+       ux.i |= uy.i & 1ULL<<63;
+       return ux.f;
 }