tests/test-dup3.c

   1 /* Test duplicating file descriptors.
   2    Copyright (C) 2009-2025 Free Software Foundation, Inc.
   3
   4    This program is free software: you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation, either version 3 of the License, or
   7    (at your option) any later version.
   8
   9    This program is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License
  15    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  16
  17 /* Written by Eric Blake <ebb9@byu.net>, 2009,
  18    and Bruno Haible <bruno@clisp.org>, 2009.  */
  19
  20 #include <config.h>
  21
  22 #include <unistd.h>
  23
  24 #include "signature.h"
  25 SIGNATURE_CHECK (dup3, int, (int, int, int));
  26
  27 #include <errno.h>
  28 #include <fcntl.h>
  29
  30 #if defined _WIN32 && ! defined __CYGWIN__
  31 /* Get declarations of the native Windows API functions.  */
  32 # define WIN32_LEAN_AND_MEAN
  33 # include <windows.h>
  34 /* Get _get_osfhandle.  */
  35 # if GNULIB_MSVC_NOTHROW
  36 #  include "msvc-nothrow.h"
  37 # else
  38 #  include <io.h>
  39 # endif
  40 #endif
  41
  42 #include "binary-io.h"
  43 #include "macros.h"
  44
  45 /* Return true if FD is open.  */
  46 static bool
  47 is_open (int fd)
  48 {
  49 #if defined _WIN32 && ! defined __CYGWIN__
  50   /* On native Windows, the initial state of unassigned standard file
  51      descriptors is that they are open but point to an
  52      INVALID_HANDLE_VALUE, and there is no fcntl.  */
  53   return (HANDLE) _get_osfhandle (fd) != INVALID_HANDLE_VALUE;
  54 #else
  55 # ifndef F_GETFL
  56 #  error Please port fcntl to your platform
  57 # endif
  58   return 0 <= fcntl (fd, F_GETFL);
  59 #endif
  60 }
  61
  62 /* Return true if FD is not inherited to child processes.  */
  63 static bool
  64 is_cloexec (int fd)
  65 {
  66 #if defined _WIN32 && ! defined __CYGWIN__
  67   HANDLE h = (HANDLE) _get_osfhandle (fd);
  68   DWORD flags;
  69   ASSERT (GetHandleInformation (h, &flags));
  70   return (flags & HANDLE_FLAG_INHERIT) == 0;
  71 #else
  72   int flags;
  73   ASSERT ((flags = fcntl (fd, F_GETFD)) >= 0);
  74   return (flags & FD_CLOEXEC) != 0;
  75 #endif
  76 }
  77
  78 int
  79 main ()
  80 {
  81   int use_cloexec;
  82   int bad_fd = getdtablesize ();
  83
  84 #if O_CLOEXEC
  85   for (use_cloexec = 0; use_cloexec <= 1; use_cloexec++)
  86 #else
  87   use_cloexec = 0;
  88 #endif
  89     {
  90       const char *file = "test-dup3.tmp";
  91       int fd = open (file, O_CREAT | O_TRUNC | O_RDWR, 0600);
  92       int o_flags;
  93       char buffer[1];
  94
  95       o_flags = 0;
  96 #if O_CLOEXEC
  97       if (use_cloexec)
  98         o_flags |= O_CLOEXEC;
  99 #endif
 100
 101       /* Assume std descriptors were provided by invoker.  */
 102       ASSERT (STDERR_FILENO < fd);
 103       ASSERT (is_open (fd));
 104       /* Ignore any other fd's leaked into this process.  */
 105       close (fd + 1);
 106       close (fd + 2);
 107       ASSERT (!is_open (fd + 1));
 108       ASSERT (!is_open (fd + 2));
 109
 110       /* Assigning to self is invalid.  */
 111       errno = 0;
 112       ASSERT (dup3 (fd, fd, o_flags) == -1);
 113       ASSERT (errno == EINVAL);
 114       ASSERT (is_open (fd));
 115
 116       /* If the source is not open, then the destination is unaffected.  */
 117       errno = 0;
 118       ASSERT (dup3 (fd + 1, fd + 2, o_flags) == -1);
 119       ASSERT (errno == EBADF);
 120       ASSERT (!is_open (fd + 2));
 121       errno = 0;
 122       ASSERT (dup3 (fd + 1, fd, o_flags) == -1);
 123       ASSERT (errno == EBADF);
 124       ASSERT (is_open (fd));
 125
 126       /* The destination must be valid.  */
 127       errno = 0;
 128       ASSERT (dup3 (fd, -2, o_flags) == -1);
 129       ASSERT (errno == EBADF);
 130       if (bad_fd > 256)
 131         {
 132           ASSERT (dup3 (fd, 255, 0) == 255);
 133           ASSERT (dup3 (fd, 256, 0) == 256);
 134           ASSERT (close (255) == 0);
 135           ASSERT (close (256) == 0);
 136         }
 137       ASSERT (dup3 (fd, bad_fd - 1, 0) == bad_fd - 1);
 138       ASSERT (close (bad_fd - 1) == 0);
 139       errno = 0;
 140       ASSERT (dup3 (fd, bad_fd, o_flags) == -1);
 141       ASSERT (errno == EBADF);
 142
 143       /* Using dup3 can skip fds.  */
 144       ASSERT (dup3 (fd, fd + 2, o_flags) == fd + 2);
 145       ASSERT (is_open (fd));
 146       ASSERT (!is_open (fd + 1));
 147       ASSERT (is_open (fd + 2));
 148       if (use_cloexec)
 149         ASSERT (is_cloexec (fd + 2));
 150       else
 151         ASSERT (!is_cloexec (fd + 2));
 152
 153       /* Verify that dup3 closes the previous occupant of a fd.  */
 154       ASSERT (open ("/dev/null", O_WRONLY, 0600) == fd + 1);
 155       ASSERT (dup3 (fd + 1, fd, o_flags) == fd);
 156       ASSERT (close (fd + 1) == 0);
 157       ASSERT (write (fd, "1", 1) == 1);
 158       ASSERT (dup3 (fd + 2, fd, o_flags) == fd);
 159       ASSERT (lseek (fd, 0, SEEK_END) == 0);
 160       ASSERT (write (fd + 2, "2", 1) == 1);
 161       ASSERT (lseek (fd, 0, SEEK_SET) == 0);
 162       ASSERT (read (fd, buffer, 1) == 1);
 163       ASSERT (*buffer == '2');
 164
 165       /* Clean up.  */
 166       ASSERT (close (fd + 2) == 0);
 167       ASSERT (close (fd) == 0);
 168       ASSERT (unlink (file) == 0);
 169     }
 170
 171   return test_exit_status;
 172 }