Add a "fork" of musl as //fusl.

fusl/src/math/frexp.c

Index: fusl/src/math/frexp.c
diff --git a/fusl/src/math/frexp.c b/fusl/src/math/frexp.c
new file mode 100644
index 0000000000000000000000000000000000000000..27b6266ed0c1d7c5dadd06ecc186a994fdcd1c52
--- /dev/null
+++ b/fusl/src/math/frexp.c
@@ -0,0 +1,23 @@
+#include <math.h>
+#include <stdint.h>
+
+double frexp(double x, int *e)
+{
+	union { double d; uint64_t i; } y = { x };
+	int ee = y.i>>52 & 0x7ff;
+
+	if (!ee) {
+		if (x) {
+			x = frexp(x*0x1p64, e);
+			*e -= 64;
+		} else *e = 0;
+		return x;
+	} else if (ee == 0x7ff) {
+		return x;
+	}
+
+	*e = ee - 0x3fe;
+	y.i &= 0x800fffffffffffffull;
+	y.i |= 0x3fe0000000000000ull;
+	return y.d;
+}