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

fusl/src/locale/setlocale.c

Index: fusl/src/locale/setlocale.c
diff --git a/fusl/src/locale/setlocale.c b/fusl/src/locale/setlocale.c
new file mode 100644
index 0000000000000000000000000000000000000000..8dae5a4e8e446b9027aff4bdd5005a6b1c43142b
--- /dev/null
+++ b/fusl/src/locale/setlocale.c
@@ -0,0 +1,70 @@
+#include <locale.h>
+#include <stdlib.h>
+#include <string.h>
+#include "locale_impl.h"
+#include "libc.h"
+#include "atomic.h"
+
+static char buf[LC_ALL*(LOCALE_NAME_MAX+1)];
+
+static char *setlocale_one_unlocked(int cat, const char *name)
+{
+	const struct __locale_map *lm;
+
+	if (name) libc.global_locale.cat[cat] = lm = __get_locale(cat, name);
+	else lm = libc.global_locale.cat[cat];
+
+	return lm ? (char *)lm->name : "C";
+}
+
+char *__strchrnul(const char *, int);
+
+char *setlocale(int cat, const char *name)
+{
+	static volatile int lock[2];
+
+	if ((unsigned)cat > LC_ALL) return 0;
+
+	LOCK(lock);
+
+	/* For LC_ALL, setlocale is required to return a string which
+	 * encodes the current setting for all categories. The format of
+	 * this string is unspecified, and only the following code, which
+	 * performs both the serialization and deserialization, depends
+	 * on the format, so it can easily be changed if needed. */
+	if (cat == LC_ALL) {
+		int i;
+		if (name) {
+			char part[LOCALE_NAME_MAX+1] = "C.UTF-8";
+			const char *p = name;
+			for (i=0; i<LC_ALL; i++) {
+				const char *z = __strchrnul(p, ';');
+				if (z-p <= LOCALE_NAME_MAX) {
+					memcpy(part, p, z-p);
+					part[z-p] = 0;
+					if (*z) p = z+1;
+				}
+				setlocale_one_unlocked(i, part);
+			}
+		}
+		char *s = buf;
+		for (i=0; i<LC_ALL; i++) {
+			const struct __locale_map *lm =
+				libc.global_locale.cat[i];
+			const char *part = lm ? lm->name : "C";
+			size_t l = strlen(part);
+			memcpy(s, part, l);
+			s[l] = ';';
+			s += l+1;
+		}
+		*--s = 0;
+		UNLOCK(lock);
+		return buf;
+	}
+
+	char *ret = setlocale_one_unlocked(cat, name);
+
+	UNLOCK(lock);
+
+	return ret;
+}