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

fusl/src/stdio/fgetwc.c

Index: fusl/src/stdio/fgetwc.c
diff --git a/fusl/src/stdio/fgetwc.c b/fusl/src/stdio/fgetwc.c
new file mode 100644
index 0000000000000000000000000000000000000000..e455cfec408bc101c7c15077e68d45f4491e3395
--- /dev/null
+++ b/fusl/src/stdio/fgetwc.c
@@ -0,0 +1,61 @@
+#include "stdio_impl.h"
+#include "locale_impl.h"
+#include <wchar.h>
+#include <errno.h>
+
+static wint_t __fgetwc_unlocked_internal(FILE *f)
+{
+	mbstate_t st = { 0 };
+	wchar_t wc;
+	int c;
+	unsigned char b;
+	size_t l;
+
+	/* Convert character from buffer if possible */
+	if (f->rpos < f->rend) {
+		l = mbrtowc(&wc, (void *)f->rpos, f->rend - f->rpos, &st);
+		if (l+2 >= 2) {
+			f->rpos += l + !l; /* l==0 means 1 byte, null */
+			return wc;
+		}
+		if (l == -1) {
+			f->rpos++;
+			return WEOF;
+		}
+	} else l = -2;
+
+	/* Convert character byte-by-byte */
+	while (l == -2) {
+		b = c = getc_unlocked(f);
+		if (c < 0) {
+			if (!mbsinit(&st)) errno = EILSEQ;
+			return WEOF;
+		}
+		l = mbrtowc(&wc, (void *)&b, 1, &st);
+		if (l == -1) return WEOF;
+	}
+
+	return wc;
+}
+
+wint_t __fgetwc_unlocked(FILE *f)
+{
+	locale_t *ploc = &CURRENT_LOCALE, loc = *ploc;
+	if (f->mode <= 0) fwide(f, 1);
+	*ploc = f->locale;
+	wchar_t wc = __fgetwc_unlocked_internal(f);
+	*ploc = loc;
+	return wc;
+}
+
+wint_t fgetwc(FILE *f)
+{
+	wint_t c;
+	FLOCK(f);
+	c = __fgetwc_unlocked(f);
+	FUNLOCK(f);
+	return c;
+}
+
+weak_alias(__fgetwc_unlocked, fgetwc_unlocked);
+weak_alias(__fgetwc_unlocked, getwc_unlocked);