gl/open.c

   1 /* Open a descriptor to a file.
   2    Copyright (C) 2007-2010 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 <http://www.gnu.org/licenses/>.  */
  16
  17 /* Written by Bruno Haible <bruno@clisp.org>, 2007.  */
  18
  19 #include <config.h>
  20
  21 /* Get the original definition of open.  It might be defined as a macro.  */
  22 #define __need_system_fcntl_h
  23 #include <fcntl.h>
  24 #undef __need_system_fcntl_h
  25 #include <sys/types.h>
  26
  27 static inline int
  28 orig_open (const char *filename, int flags, mode_t mode)
  29 {
  30   return open (filename, flags, mode);
  31 }
  32
  33 /* Specification.  */
  34 #include <fcntl.h>
  35
  36 #include <errno.h>
  37 #include <stdarg.h>
  38 #include <string.h>
  39 #include <sys/types.h>
  40 #include <sys/stat.h>
  41 #include <unistd.h>
  42
  43 #ifndef REPLACE_OPEN_DIRECTORY
  44 # define REPLACE_OPEN_DIRECTORY 0
  45 #endif
  46
  47 int
  48 open (const char *filename, int flags, ...)
  49 {
  50   mode_t mode;
  51   int fd;
  52
  53   mode = 0;
  54   if (flags & O_CREAT)
  55     {
  56       va_list arg;
  57       va_start (arg, flags);
  58
  59       /* We have to use PROMOTED_MODE_T instead of mode_t, otherwise GCC 4
  60          creates crashing code when 'mode_t' is smaller than 'int'.  */
  61       mode = va_arg (arg, PROMOTED_MODE_T);
  62
  63       va_end (arg);
  64     }
  65
  66 #if (defined _WIN32 || defined __WIN32__) && ! defined __CYGWIN__
  67   if (strcmp (filename, "/dev/null") == 0)
  68     filename = "NUL";
  69 #endif
  70
  71 #if OPEN_TRAILING_SLASH_BUG
  72   /* If the filename ends in a slash and one of O_CREAT, O_WRONLY, O_RDWR
  73      is specified, then fail.
  74      Rationale: POSIX <http://www.opengroup.org/susv3/basedefs/xbd_chap04.html>
  75      says that
  76        "A pathname that contains at least one non-slash character and that
  77         ends with one or more trailing slashes shall be resolved as if a
  78         single dot character ( '.' ) were appended to the pathname."
  79      and
  80        "The special filename dot shall refer to the directory specified by
  81         its predecessor."
  82      If the named file already exists as a directory, then
  83        - if O_CREAT is specified, open() must fail because of the semantics
  84          of O_CREAT,
  85        - if O_WRONLY or O_RDWR is specified, open() must fail because POSIX
  86          <http://www.opengroup.org/susv3/functions/open.html> says that it
  87          fails with errno = EISDIR in this case.
  88      If the named file does not exist or does not name a directory, then
  89        - if O_CREAT is specified, open() must fail since open() cannot create
  90          directories,
  91        - if O_WRONLY or O_RDWR is specified, open() must fail because the
  92          file does not contain a '.' directory.  */
  93   if (flags & (O_CREAT | O_WRONLY | O_RDWR))
  94     {
  95       size_t len = strlen (filename);
  96       if (len > 0 && filename[len - 1] == '/')
  97         {
  98           errno = EISDIR;
  99           return -1;
 100         }
 101     }
 102 #endif
 103
 104   fd = orig_open (filename, flags, mode);
 105
 106 #if REPLACE_FCHDIR
 107   /* Implementing fchdir and fdopendir requires the ability to open a
 108      directory file descriptor.  If open doesn't support that (as on
 109      mingw), we use a dummy file that behaves the same as directories
 110      on Linux (ie. always reports EOF on attempts to read()), and
 111      override fstat() in fchdir.c to hide the fact that we have a
 112      dummy.  */
 113   if (REPLACE_OPEN_DIRECTORY && fd < 0 && errno == EACCES
 114       && (flags & O_ACCMODE) == O_RDONLY)
 115     {
 116       struct stat statbuf;
 117       if (stat (filename, &statbuf) == 0 && S_ISDIR (statbuf.st_mode))
 118         {
 119           /* Maximum recursion depth of 1.  */
 120           fd = open ("/dev/null", flags, mode);
 121           if (0 <= fd)
 122             fd = _gl_register_fd (fd, filename);
 123         }
 124       else
 125         errno = EACCES;
 126     }
 127 #endif
 128
 129 #if OPEN_TRAILING_SLASH_BUG
 130   /* If the filename ends in a slash and fd does not refer to a directory,
 131      then fail.
 132      Rationale: POSIX <http://www.opengroup.org/susv3/basedefs/xbd_chap04.html>
 133      says that
 134        "A pathname that contains at least one non-slash character and that
 135         ends with one or more trailing slashes shall be resolved as if a
 136         single dot character ( '.' ) were appended to the pathname."
 137      and
 138        "The special filename dot shall refer to the directory specified by
 139         its predecessor."
 140      If the named file without the slash is not a directory, open() must fail
 141      with ENOTDIR.  */
 142   if (fd >= 0)
 143     {
 144       /* We know len is positive, since open did not fail with ENOENT.  */
 145       size_t len = strlen (filename);
 146       if (filename[len - 1] == '/')
 147         {
 148           struct stat statbuf;
 149
 150           if (fstat (fd, &statbuf) >= 0 && !S_ISDIR (statbuf.st_mode))
 151             {
 152               close (fd);
 153               errno = ENOTDIR;
 154               return -1;
 155             }
 156         }
 157     }
 158 #endif
 159
 160 #if REPLACE_FCHDIR
 161   if (!REPLACE_OPEN_DIRECTORY && 0 <= fd)
 162     fd = _gl_register_fd (fd, filename);
 163 #endif
 164
 165   return fd;
 166 }