source: vendor/gzip/1.3.11/lib/dup-safer.c

/* Invoke dup, but avoid some glitches.

   Copyright (C) 2001, 2004, 2005, 2006 Free Software Foundation, Inc.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2, or (at your option)
   any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software Foundation,
   Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */

/* Written by Paul Eggert.  */

#include <config.h>

#include "unistd-safer.h"

#include <fcntl.h>

#include <unistd.h>
#ifndef STDERR_FILENO
# define STDERR_FILENO 2
#endif

/* Like dup, but do not return STDIN_FILENO, STDOUT_FILENO, or
   STDERR_FILENO.  */

int
dup_safer (int fd)
{
#if defined F_DUPFD && !defined FCHDIR_REPLACEMENT
  return fcntl (fd, F_DUPFD, STDERR_FILENO + 1);
#else
  /* fd_safer calls us back, but eventually the recursion unwinds and
     does the right thing.  */
  return fd_safer (dup (fd));
#endif
}