tests/test-dup2.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
  19 #include <config.h>
  20
  21 #include <unistd.h>
  22
  23 #include "signature.h"
  24 SIGNATURE_CHECK (dup2, int, (int, int));
  25
  26 #include <errno.h>
  27 #include <fcntl.h>
  28
  29 #if HAVE_SYS_RESOURCE_H
  30 # include <sys/resource.h>
  31 #endif
  32
  33 #include "binary-io.h"
  34
  35 #if GNULIB_TEST_CLOEXEC
  36 # include "cloexec.h"
  37 #endif
  38
  39 #if defined _WIN32 && ! defined __CYGWIN__
  40 /* Get declarations of the native Windows API functions.  */
  41 # define WIN32_LEAN_AND_MEAN
  42 # include <windows.h>
  43 /* Get _get_osfhandle.  */
  44 # if GNULIB_MSVC_NOTHROW
  45 #  include "msvc-nothrow.h"
  46 # else
  47 #  include <io.h>
  48 # endif
  49 #endif
  50
  51 #include "macros.h"
  52
  53 /* Tell GCC not to warn about the specific edge cases tested here.  */
  54 #if _GL_GNUC_PREREQ (13, 0)
  55 # pragma GCC diagnostic ignored "-Wanalyzer-fd-leak"
  56 # pragma GCC diagnostic ignored "-Wanalyzer-fd-use-without-check"
  57 #endif
  58
  59 /* Return non-zero if FD is open.  */
  60 static int
  61 is_open (int fd)
  62 {
  63 #if defined _WIN32 && ! defined __CYGWIN__
  64   /* On native Windows, the initial state of unassigned standard file
  65      descriptors is that they are open but point to an
  66      INVALID_HANDLE_VALUE, and there is no fcntl.  */
  67   return (HANDLE) _get_osfhandle (fd) != INVALID_HANDLE_VALUE;
  68 #else
  69 # ifndef F_GETFL
  70 #  error Please port fcntl to your platform
  71 # endif
  72   return 0 <= fcntl (fd, F_GETFL);
  73 #endif
  74 }
  75
  76 #if GNULIB_TEST_CLOEXEC
  77 /* Return non-zero if FD is open and inheritable across exec/spawn.  */
  78 static int
  79 is_inheritable (int fd)
  80 {
  81 # if defined _WIN32 && ! defined __CYGWIN__
  82   /* On native Windows, the initial state of unassigned standard file
  83      descriptors is that they are open but point to an
  84      INVALID_HANDLE_VALUE, and there is no fcntl.  */
  85   HANDLE h = (HANDLE) _get_osfhandle (fd);
  86   DWORD flags;
  87   if (h == INVALID_HANDLE_VALUE || GetHandleInformation (h, &flags) == 0)
  88     return 0;
  89   return (flags & HANDLE_FLAG_INHERIT) != 0;
  90 # else
  91 #  ifndef F_GETFD
  92 #   error Please port fcntl to your platform
  93 #  endif
  94   int i = fcntl (fd, F_GETFD);
  95   return 0 <= i && (i & FD_CLOEXEC) == 0;
  96 # endif
  97 }
  98 #endif /* GNULIB_TEST_CLOEXEC */
  99
 100 #if !O_BINARY
 101 # define set_binary_mode my_set_binary_mode
 102 static int
 103 set_binary_mode (_GL_UNUSED int fd, _GL_UNUSED int mode)
 104 {
 105   return 0;
 106 }
 107 #endif
 108
 109 /* Return non-zero if FD is open in the given MODE, which is either
 110    O_TEXT or O_BINARY.  */
 111 static int
 112 is_mode (int fd, int mode)
 113 {
 114   int value = set_binary_mode (fd, O_BINARY);
 115   set_binary_mode (fd, value);
 116   return mode == value;
 117 }
 118
 119 int
 120 main (void)
 121 {
 122   const char *file = "test-dup2.tmp";
 123   char buffer[1];
 124   int bad_fd = getdtablesize ();
 125   int fd = open (file, O_CREAT | O_TRUNC | O_RDWR, 0600);
 126
 127   /* Assume std descriptors were provided by invoker.  */
 128   ASSERT (STDERR_FILENO < fd);
 129   ASSERT (is_open (fd));
 130   /* Ignore any other fd's leaked into this process.  */
 131   close (fd + 1);
 132   close (fd + 2);
 133   ASSERT (!is_open (fd + 1));
 134   ASSERT (!is_open (fd + 2));
 135
 136   /* Assigning to self must be a no-op.  */
 137   ASSERT (dup2 (fd, fd) == fd);
 138   ASSERT (is_open (fd));
 139
 140   /* The source must be valid.  */
 141   errno = 0;
 142   ASSERT (dup2 (-1, fd) == -1);
 143   ASSERT (errno == EBADF);
 144   close (99);
 145   errno = 0;
 146   ASSERT (dup2 (99, fd) == -1);
 147   ASSERT (errno == EBADF);
 148   errno = 0;
 149   ASSERT (dup2 (AT_FDCWD, fd) == -1);
 150   ASSERT (errno == EBADF);
 151   ASSERT (is_open (fd));
 152
 153   /* If the source is not open, then the destination is unaffected.  */
 154   errno = 0;
 155   ASSERT (dup2 (fd + 1, fd + 1) == -1);
 156   ASSERT (errno == EBADF);
 157   ASSERT (!is_open (fd + 1));
 158   errno = 0;
 159   ASSERT (dup2 (fd + 1, fd) == -1);
 160   ASSERT (errno == EBADF);
 161   ASSERT (is_open (fd));
 162
 163   /* The destination must be valid.  */
 164   errno = 0;
 165   ASSERT (dup2 (fd, -2) == -1);
 166   ASSERT (errno == EBADF);
 167   if (bad_fd > 256)
 168     {
 169       ASSERT (dup2 (fd, 255) == 255);
 170       ASSERT (dup2 (fd, 256) == 256);
 171       ASSERT (close (255) == 0);
 172       ASSERT (close (256) == 0);
 173     }
 174   ASSERT (dup2 (fd, bad_fd - 1) == bad_fd - 1);
 175   ASSERT (close (bad_fd - 1) == 0);
 176   errno = 0;
 177   ASSERT (dup2 (fd, bad_fd) == -1);
 178   ASSERT (errno == EBADF);
 179
 180   /* Using dup2 can skip fds.  */
 181   ASSERT (dup2 (fd, fd + 2) == fd + 2);
 182   ASSERT (is_open (fd));
 183   ASSERT (!is_open (fd + 1));
 184   ASSERT (is_open (fd + 2));
 185
 186   /* Verify that dup2 closes the previous occupant of a fd.  */
 187   ASSERT (open ("/dev/null", O_WRONLY, 0600) == fd + 1);
 188   ASSERT (dup2 (fd + 1, fd) == fd);
 189   ASSERT (close (fd + 1) == 0);
 190   ASSERT (write (fd, "1", 1) == 1);
 191   ASSERT (dup2 (fd + 2, fd) == fd);
 192   ASSERT (lseek (fd, 0, SEEK_END) == 0);
 193   ASSERT (write (fd + 2, "2", 1) == 1);
 194   ASSERT (lseek (fd, 0, SEEK_SET) == 0);
 195   ASSERT (read (fd, buffer, 1) == 1);
 196   ASSERT (*buffer == '2');
 197
 198 #if GNULIB_TEST_CLOEXEC
 199   /* Any new fd created by dup2 must not be cloexec.  */
 200   ASSERT (close (fd + 2) == 0);
 201   ASSERT (dup_cloexec (fd) == fd + 1);
 202   ASSERT (!is_inheritable (fd + 1));
 203   ASSERT (dup2 (fd + 1, fd + 1) == fd + 1);
 204   ASSERT (!is_inheritable (fd + 1));
 205   ASSERT (dup2 (fd + 1, fd + 2) == fd + 2);
 206   ASSERT (!is_inheritable (fd + 1));
 207   ASSERT (is_inheritable (fd + 2));
 208   errno = 0;
 209   ASSERT (dup2 (fd + 1, -1) == -1);
 210   ASSERT (errno == EBADF);
 211   ASSERT (!is_inheritable (fd + 1));
 212 #endif
 213
 214   /* On systems that distinguish between text and binary mode, dup2
 215      reuses the mode of the source.  */
 216   set_binary_mode (fd, O_BINARY);
 217   ASSERT (is_mode (fd, O_BINARY));
 218   ASSERT (dup2 (fd, fd + 1) == fd + 1);
 219   ASSERT (is_mode (fd + 1, O_BINARY));
 220   set_binary_mode (fd, O_TEXT);
 221   ASSERT (is_mode (fd, O_TEXT));
 222   ASSERT (dup2 (fd, fd + 1) == fd + 1);
 223   ASSERT (is_mode (fd + 1, O_TEXT));
 224
 225   /* Clean up.  */
 226   ASSERT (close (fd + 2) == 0);
 227   ASSERT (close (fd + 1) == 0);
 228   ASSERT (close (fd) == 0);
 229   ASSERT (unlink (file) == 0);
 230
 231   return test_exit_status;
 232 }