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

fusl/src/stdlib/strtod.c

Index: fusl/src/stdlib/strtod.c
diff --git a/fusl/src/stdlib/strtod.c b/fusl/src/stdlib/strtod.c
new file mode 100644
index 0000000000000000000000000000000000000000..461dcf858e0c3acadf9754c56c8ec4c9af052a8c
--- /dev/null
+++ b/fusl/src/stdlib/strtod.c
@@ -0,0 +1,40 @@
+#include <stdlib.h>
+#include "shgetc.h"
+#include "floatscan.h"
+#include "stdio_impl.h"
+#include "libc.h"
+
+static long double strtox(const char *s, char **p, int prec)
+{
+	FILE f = {
+		.buf = (void *)s, .rpos = (void *)s,
+		.rend = (void *)-1, .lock = -1
+	};
+	shlim(&f, 0);
+	long double y = __floatscan(&f, prec, 1);
+	off_t cnt = shcnt(&f);
+	if (p) *p = cnt ? (char *)s + cnt : (char *)s;
+	return y;
+}
+
+float strtof(const char *restrict s, char **restrict p)
+{
+	return strtox(s, p, 0);
+}
+
+double strtod(const char *restrict s, char **restrict p)
+{
+	return strtox(s, p, 1);
+}
+
+long double strtold(const char *restrict s, char **restrict p)
+{
+	return strtox(s, p, 2);
+}
+
+weak_alias(strtof, strtof_l);
+weak_alias(strtod, strtod_l);
+weak_alias(strtold, strtold_l);
+weak_alias(strtof, __strtof_l);
+weak_alias(strtod, __strtod_l);
+weak_alias(strtold, __strtold_l);