lib/fstatat.c

   1 /* Work around an fstatat bug on Solaris 9.
   2
   3    Copyright (C) 2006, 2009-2017 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 <https://www.gnu.org/licenses/>.  */
  17
  18 /* Written by Paul Eggert and Jim Meyering.  */
  19
  20 /* If the user's config.h happens to include <sys/stat.h>, let it include only
  21    the system's <sys/stat.h> here, so that orig_fstatat doesn't recurse to
  22    rpl_fstatat.  */
  23 #define __need_system_sys_stat_h
  24 #include <config.h>
  25
  26 /* Get the original definition of fstatat.  It might be defined as a macro.  */
  27 #include <sys/types.h>
  28 #include <sys/stat.h>
  29 #undef __need_system_sys_stat_h
  30
  31 #if HAVE_FSTATAT
  32 static int
  33 orig_fstatat (int fd, char const *filename, struct stat *buf, int flags)
  34 {
  35   return fstatat (fd, filename, buf, flags);
  36 }
  37 #endif
  38
  39 /* Write "sys/stat.h" here, not <sys/stat.h>, otherwise OSF/1 5.1 DTK cc
  40    eliminates this include because of the preliminary #include <sys/stat.h>
  41    above.  */
  42 #include "sys/stat.h"
  43
  44 #include <errno.h>
  45 #include <fcntl.h>
  46 #include <string.h>
  47
  48 #if HAVE_FSTATAT && HAVE_WORKING_FSTATAT_ZERO_FLAG
  49
  50 # ifndef LSTAT_FOLLOWS_SLASHED_SYMLINK
  51 #  define LSTAT_FOLLOWS_SLASHED_SYMLINK 0
  52 # endif
  53
  54 /* fstatat should always follow symbolic links that end in /, but on
  55    Solaris 9 it doesn't if AT_SYMLINK_NOFOLLOW is specified.
  56    Likewise, trailing slash on a non-directory should be an error.
  57    These are the same problems that lstat.c and stat.c address, so
  58    solve it in a similar way.
  59
  60    AIX 7.1 fstatat (AT_FDCWD, ..., 0) always fails, which is a bug.
  61    Work around this bug if FSTATAT_AT_FDCWD_0_BROKEN is nonzero.  */
  62
  63 int
  64 rpl_fstatat (int fd, char const *file, struct stat *st, int flag)
  65 {
  66   int result = orig_fstatat (fd, file, st, flag);
  67   size_t len;
  68
  69   if (LSTAT_FOLLOWS_SLASHED_SYMLINK || result != 0)
  70     return result;
  71   len = strlen (file);
  72   if (flag & AT_SYMLINK_NOFOLLOW)
  73     {
  74       /* Fix lstat behavior.  */
  75       if (file[len - 1] != '/' || S_ISDIR (st->st_mode))
  76         return 0;
  77       if (!S_ISLNK (st->st_mode))
  78         {
  79           errno = ENOTDIR;
  80           return -1;
  81         }
  82       result = orig_fstatat (fd, file, st, flag & ~AT_SYMLINK_NOFOLLOW);
  83     }
  84   /* Fix stat behavior.  */
  85   if (result == 0 && !S_ISDIR (st->st_mode) && file[len - 1] == '/')
  86     {
  87       errno = ENOTDIR;
  88       return -1;
  89     }
  90   return result;
  91 }
  92
  93 #else /* ! (HAVE_FSTATAT && HAVE_WORKING_FSTATAT_ZERO_FLAG) */
  94
  95 /* On mingw, the gnulib <sys/stat.h> defines 'stat' as a function-like
  96    macro; but using it in AT_FUNC_F2 causes compilation failure
  97    because the preprocessor sees a use of a macro that requires two
  98    arguments but is only given one.  Hence, we need an inline
  99    forwarder to get past the preprocessor.  */
 100 static int
 101 stat_func (char const *name, struct stat *st)
 102 {
 103   return stat (name, st);
 104 }
 105
 106 /* Likewise, if there is no native 'lstat', then the gnulib
 107    <sys/stat.h> defined it as stat, which also needs adjustment.  */
 108 # if !HAVE_LSTAT
 109 #  undef lstat
 110 #  define lstat stat_func
 111 # endif
 112
 113 /* Replacement for Solaris' function by the same name.
 114    <http://www.google.com/search?q=fstatat+site:docs.sun.com>
 115    First, try to simulate it via l?stat ("/proc/self/fd/FD/FILE").
 116    Failing that, simulate it via save_cwd/fchdir/(stat|lstat)/restore_cwd.
 117    If either the save_cwd or the restore_cwd fails (relatively unlikely),
 118    then give a diagnostic and exit nonzero.
 119    Otherwise, this function works just like Solaris' fstatat.  */
 120
 121 # define AT_FUNC_NAME fstatat
 122 # define AT_FUNC_F1 lstat
 123 # define AT_FUNC_F2 stat_func
 124 # define AT_FUNC_USE_F1_COND AT_SYMLINK_NOFOLLOW
 125 # define AT_FUNC_POST_FILE_PARAM_DECLS , struct stat *st, int flag
 126 # define AT_FUNC_POST_FILE_ARGS        , st
 127 # include "at-func.c"
 128 # undef AT_FUNC_NAME
 129 # undef AT_FUNC_F1
 130 # undef AT_FUNC_F2
 131 # undef AT_FUNC_USE_F1_COND
 132 # undef AT_FUNC_POST_FILE_PARAM_DECLS
 133 # undef AT_FUNC_POST_FILE_ARGS
 134
 135 #endif /* !HAVE_FSTATAT */