lib/dup2.c

   1 /* Duplicate an open file descriptor to a specified file descriptor.
   2
   3    Copyright (C) 1999, 2004-2007, 2009-2011 Free Software Foundation, Inc.
   4
   5    This program is free software: you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation; either version 3 of the License, or
   8    (at your option) any later version.
   9
  10    This program is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  17
  18 /* written by Paul Eggert */
  19
  20 #include <config.h>
  21
  22 /* Specification.  */
  23 #include <unistd.h>
  24
  25 #include <errno.h>
  26 #include <fcntl.h>
  27
  28 #if (defined _WIN32 || defined __WIN32__) && ! defined __CYGWIN__
  29 /* Get declarations of the Win32 API functions.  */
  30 # define WIN32_LEAN_AND_MEAN
  31 # include <windows.h>
  32 #endif
  33
  34 #if HAVE_DUP2
  35
  36 # undef dup2
  37
  38 int
  39 rpl_dup2 (int fd, int desired_fd)
  40 {
  41   int result;
  42 # if (defined _WIN32 || defined __WIN32__) && ! defined __CYGWIN__
  43   /* If fd is closed, mingw hangs on dup2 (fd, fd).  If fd is open,
  44      dup2 (fd, fd) returns 0, but all further attempts to use fd in
  45      future dup2 calls will hang.  */
  46   if (fd == desired_fd)
  47     {
  48       if ((HANDLE) _get_osfhandle (fd) == INVALID_HANDLE_VALUE)
  49         {
  50           errno = EBADF;
  51           return -1;
  52         }
  53       return fd;
  54     }
  55   /* Wine 1.0.1 return 0 when desired_fd is negative but not -1:
  56      http://bugs.winehq.org/show_bug.cgi?id=21289 */
  57   if (desired_fd < 0)
  58     {
  59       errno = EBADF;
  60       return -1;
  61     }
  62 # elif !defined __linux__
  63   /* On Haiku, dup2 (fd, fd) mistakenly clears FD_CLOEXEC.  */
  64   if (fd == desired_fd)
  65     return fcntl (fd, F_GETFL) == -1 ? -1 : fd;
  66 # endif
  67   result = dup2 (fd, desired_fd);
  68 # ifdef __linux__
  69   /* Correct a Linux return value.
  70      <http://git.kernel.org/?p=linux/kernel/git/stable/linux-2.6.30.y.git;a=commitdiff;h=2b79bc4f7ebbd5af3c8b867968f9f15602d5f802>
  71    */
  72   if (fd == desired_fd && result == (unsigned int) -EBADF)
  73     {
  74       errno = EBADF;
  75       result = -1;
  76     }
  77 # endif
  78   if (result == 0)
  79     result = desired_fd;
  80   /* Correct a cygwin 1.5.x errno value.  */
  81   else if (result == -1 && errno == EMFILE)
  82     errno = EBADF;
  83 # if REPLACE_FCHDIR
  84   if (fd != desired_fd && result != -1)
  85     result = _gl_register_dup (fd, result);
  86 # endif
  87   return result;
  88 }
  89
  90 #else /* !HAVE_DUP2 */
  91
  92 /* On older platforms, dup2 did not exist.  */
  93
  94 # ifndef F_DUPFD
  95 static int
  96 dupfd (int fd, int desired_fd)
  97 {
  98   int duplicated_fd = dup (fd);
  99   if (duplicated_fd < 0 || duplicated_fd == desired_fd)
 100     return duplicated_fd;
 101   else
 102     {
 103       int r = dupfd (fd, desired_fd);
 104       int e = errno;
 105       close (duplicated_fd);
 106       errno = e;
 107       return r;
 108     }
 109 }
 110 # endif
 111
 112 int
 113 dup2 (int fd, int desired_fd)
 114 {
 115   int result = fcntl (fd, F_GETFL) < 0 ? -1 : fd;
 116   if (result == -1 || fd == desired_fd)
 117     return result;
 118   close (desired_fd);
 119 # ifdef F_DUPFD
 120   result = fcntl (fd, F_DUPFD, desired_fd);
 121 #  if REPLACE_FCHDIR
 122   if (0 <= result)
 123     result = _gl_register_dup (fd, result);
 124 #  endif
 125 # else
 126   result = dupfd (fd, desired_fd);
 127 # endif
 128   if (result == -1 && (errno == EMFILE || errno == EINVAL))
 129     errno = EBADF;
 130   return result;
 131 }
 132 #endif /* !HAVE_DUP2 */