lib/dup2.c

   1 /* Duplicate an open file descriptor to a specified file descriptor.
   2
   3    Copyright (C) 1999, 2004-2007, 2009-2013 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 HAVE_DUP2
  29
  30 # undef dup2
  31
  32 # if (defined _WIN32 || defined __WIN32__) && ! defined __CYGWIN__
  33
  34 /* Get declarations of the native Windows API functions.  */
  35 #  define WIN32_LEAN_AND_MEAN
  36 #  include <windows.h>
  37
  38 #  include "msvc-inval.h"
  39
  40 /* Get _get_osfhandle.  */
  41 #  include "msvc-nothrow.h"
  42
  43 static int
  44 ms_windows_dup2 (int fd, int desired_fd)
  45 {
  46   int result;
  47
  48   /* If fd is closed, mingw hangs on dup2 (fd, fd).  If fd is open,
  49      dup2 (fd, fd) returns 0, but all further attempts to use fd in
  50      future dup2 calls will hang.  */
  51   if (fd == desired_fd)
  52     {
  53       if ((HANDLE) _get_osfhandle (fd) == INVALID_HANDLE_VALUE)
  54         {
  55           errno = EBADF;
  56           return -1;
  57         }
  58       return fd;
  59     }
  60
  61   /* Wine 1.0.1 return 0 when desired_fd is negative but not -1:
  62      http://bugs.winehq.org/show_bug.cgi?id=21289 */
  63   if (desired_fd < 0)
  64     {
  65       errno = EBADF;
  66       return -1;
  67     }
  68
  69   TRY_MSVC_INVAL
  70     {
  71       result = dup2 (fd, desired_fd);
  72     }
  73   CATCH_MSVC_INVAL
  74     {
  75       errno = EBADF;
  76       result = -1;
  77     }
  78   DONE_MSVC_INVAL;
  79
  80   if (result == 0)
  81     result = desired_fd;
  82
  83   return result;
  84 }
  85
  86 #  define dup2 ms_windows_dup2
  87
  88 # endif
  89
  90 int
  91 rpl_dup2 (int fd, int desired_fd)
  92 {
  93   int result;
  94
  95 # ifdef F_GETFL
  96   /* On Linux kernels 2.6.26-2.6.29, dup2 (fd, fd) returns -EBADF.
  97      On Cygwin 1.5.x, dup2 (1, 1) returns 0.
  98      On Cygwin 1.7.17, dup2 (1, -1) dumps core.
  99      On Haiku, dup2 (fd, fd) mistakenly clears FD_CLOEXEC.  */
 100   if (desired_fd < 0)
 101     fd = desired_fd;
 102   if (fd == desired_fd)
 103     return fcntl (fd, F_GETFL) == -1 ? -1 : fd;
 104 # endif
 105
 106   result = dup2 (fd, desired_fd);
 107
 108   /* Correct an errno value on FreeBSD 6.1 and Cygwin 1.5.x.  */
 109   if (result == -1 && errno == EMFILE)
 110     errno = EBADF;
 111 # if REPLACE_FCHDIR
 112   if (fd != desired_fd && result != -1)
 113     result = _gl_register_dup (fd, result);
 114 # endif
 115   return result;
 116 }
 117
 118 #else /* !HAVE_DUP2 */
 119
 120 /* On older platforms, dup2 did not exist.  */
 121
 122 # ifndef F_DUPFD
 123 static int
 124 dupfd (int fd, int desired_fd)
 125 {
 126   int duplicated_fd = dup (fd);
 127   if (duplicated_fd < 0 || duplicated_fd == desired_fd)
 128     return duplicated_fd;
 129   else
 130     {
 131       int r = dupfd (fd, desired_fd);
 132       int e = errno;
 133       close (duplicated_fd);
 134       errno = e;
 135       return r;
 136     }
 137 }
 138 # endif
 139
 140 int
 141 dup2 (int fd, int desired_fd)
 142 {
 143   int result = fcntl (fd, F_GETFL) < 0 ? -1 : fd;
 144   if (result == -1 || fd == desired_fd)
 145     return result;
 146   close (desired_fd);
 147 # ifdef F_DUPFD
 148   result = fcntl (fd, F_DUPFD, desired_fd);
 149 #  if REPLACE_FCHDIR
 150   if (0 <= result)
 151     result = _gl_register_dup (fd, result);
 152 #  endif
 153 # else
 154   result = dupfd (fd, desired_fd);
 155 # endif
 156   if (result == -1 && (errno == EMFILE || errno == EINVAL))
 157     errno = EBADF;
 158   return result;
 159 }
 160 #endif /* !HAVE_DUP2 */