Add dup3(), based on F_DUP2FD and F_DUP2FD_CLOEXEC fcntls.

I removed functionality not proposed for POSIX in Austin group issue #411.
A man page (my own) and test cases will follow in later commits.

PR:		176233
Submitted by:	Jukka Ukkonen

include/unistd.h

@@ -493,6 +493,7 @@ const char *
 int	 crypt_set_format(const char *);
 int	 des_cipher(const char *, char *, long, int);
 int	 des_setkey(const char *key);
+int	 dup3(int, int, int);
 int	 eaccess(const char *, int);
 void	 endusershell(void);
 int	 exect(const char *, char * const *, char * const *);

lib/libc/gen/Makefile.inc

@@ -31,6 +31,7 @@ SRCS+=	__getosreldate.c \
 	disklabel.c \
 	dlfcn.c \
 	drand48.c \
+	dup3.c \
 	elf_utils.c \
 	erand48.c \
 	err.c \

lib/libc/gen/Symbol.map

@@ -383,6 +383,7 @@ FBSD_1.2 {
 FBSD_1.3 {
 	clock_getcpuclockid;
 	dirfd;
+	dup3;
 	 fdlopen;
 	__FreeBSD_libc_enter_restricted_mode;
 	getcontextx;

lib/libc/gen/dup3.c

@@ -0,0 +1,59 @@
+/*-
+ * Copyright (c) 2012 Jukka A. Ukkonen
+ * All rights reserved.
+ *
+ * This software was developed by Jukka Ukkonen for FreeBSD.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include "namespace.h"
+#include <unistd.h>
+#include <fcntl.h>
+#include <errno.h>
+#include "un-namespace.h"
+
+int
+__dup3(int oldfd, int newfd, int flags)
+{
+	int how;
+
+	if (oldfd == newfd) {
+		errno = EINVAL;
+		return (-1);
+	}
+
+	if (flags & ~O_CLOEXEC) {
+		errno = EINVAL;
+		return (-1);
+	}
+
+	how = (flags & O_CLOEXEC) ? F_DUP2FD_CLOEXEC : F_DUP2FD;
+
+	return (_fcntl(oldfd, how, newfd));
+}
+
+__weak_reference(__dup3, dup3);
+__weak_reference(__dup3, _dup3);