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

fusl/src/stdio/__fdopen.c

Index: fusl/src/stdio/__fdopen.c
diff --git a/fusl/src/stdio/__fdopen.c b/fusl/src/stdio/__fdopen.c
new file mode 100644
index 0000000000000000000000000000000000000000..8d6ce813e45ec8ed880e1680d38fb409b4f63000
--- /dev/null
+++ b/fusl/src/stdio/__fdopen.c
@@ -0,0 +1,60 @@
+#include "stdio_impl.h"
+#include <stdlib.h>
+#include <sys/ioctl.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <string.h>
+
+FILE *__fdopen(int fd, const char *mode)
+{
+	FILE *f;
+	struct winsize wsz;
+
+	/* Check for valid initial mode character */
+	if (!strchr("rwa", *mode)) {
+		errno = EINVAL;
+		return 0;
+	}
+
+	/* Allocate FILE+buffer or fail */
+	if (!(f=malloc(sizeof *f + UNGET + BUFSIZ))) return 0;
+
+	/* Zero-fill only the struct, not the buffer */
+	memset(f, 0, sizeof *f);
+
+	/* Impose mode restrictions */
+	if (!strchr(mode, '+')) f->flags = (*mode == 'r') ? F_NOWR : F_NORD;
+
+	/* Apply close-on-exec flag */
+	if (strchr(mode, 'e')) __syscall(SYS_fcntl, fd, F_SETFD, FD_CLOEXEC);
+
+	/* Set append mode on fd if opened for append */
+	if (*mode == 'a') {
+		int flags = __syscall(SYS_fcntl, fd, F_GETFL);
+		if (!(flags & O_APPEND))
+			__syscall(SYS_fcntl, fd, F_SETFL, flags | O_APPEND);
+		f->flags |= F_APP;
+	}
+
+	f->fd = fd;
+	f->buf = (unsigned char *)f + sizeof *f + UNGET;
+	f->buf_size = BUFSIZ;
+
+	/* Activate line buffered mode for terminals */
+	f->lbf = EOF;
+	if (!(f->flags & F_NOWR) && !__syscall(SYS_ioctl, fd, TIOCGWINSZ, &wsz))
+		f->lbf = '\n';
+
+	/* Initialize op ptrs. No problem if some are unneeded. */
+	f->read = __stdio_read;
+	f->write = __stdio_write;
+	f->seek = __stdio_seek;
+	f->close = __stdio_close;
+
+	if (!libc.threaded) f->lock = -1;
+
+	/* Add new FILE to open file list */
+	return __ofl_add(f);
+}
+
+weak_alias(__fdopen, fdopen);