usr: libc: Add math.h + musl math impl portexpt

Signed-off-by: Ian Moffett <ian@osmora.org>

1 files changed, 8 insertions, 0 deletions

diff --git a/lib/libc/src/musl-math/copysign.c b/lib/libc/src/musl-math/copysign.c
new file mode 100644
index 0000000..b09331b
--- /dev/null
+++ b/lib/libc/src/musl-math/copysign.c
@@ -0,0 +1,8 @@
+#include "libm.h"
+
+double copysign(double x, double y) {
+	union {double f; uint64_t i;} ux={x}, uy={y};
+	ux.i &= -1ULL/2;
+	ux.i |= uy.i & 1ULL<<63;
+	return ux.f;
+}