lib/fstatat.c

   1 /* Work around an fstatat bug on Solaris 9.
   2
   3    Copyright (C) 2006, 2009-2019 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 && HAVE_WORKING_FSTATAT_ZERO_FLAG
  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 "stat-time.h"
  45
  46 #include <errno.h>
  47 #include <fcntl.h>
  48 #include <string.h>
  49
  50 #if HAVE_FSTATAT && HAVE_WORKING_FSTATAT_ZERO_FLAG
  51
  52 # ifndef LSTAT_FOLLOWS_SLASHED_SYMLINK
  53 #  define LSTAT_FOLLOWS_SLASHED_SYMLINK 0
  54 # endif
  55
  56 static int
  57 normal_fstatat (int fd, char const *file, struct stat *st, int flag)
  58 {
  59   return stat_time_normalize (orig_fstatat (fd, file, st, flag), st);
  60 }
  61
  62 /* fstatat should always follow symbolic links that end in /, but on
  63    Solaris 9 it doesn't if AT_SYMLINK_NOFOLLOW is specified.
  64    Likewise, trailing slash on a non-directory should be an error.
  65    These are the same problems that lstat.c and stat.c address, so
  66    solve it in a similar way.
  67
  68    AIX 7.1 fstatat (AT_FDCWD, ..., 0) always fails, which is a bug.
  69    Work around this bug if FSTATAT_AT_FDCWD_0_BROKEN is nonzero.  */
  70
  71 int
  72 rpl_fstatat (int fd, char const *file, struct stat *st, int flag)
  73 {
  74   int result = normal_fstatat (fd, file, st, flag);
  75   size_t len;
  76
  77   if (LSTAT_FOLLOWS_SLASHED_SYMLINK || result != 0)
  78     return result;
  79   len = strlen (file);
  80   if (flag & AT_SYMLINK_NOFOLLOW)
  81     {
  82       /* Fix lstat behavior.  */
  83       if (file[len - 1] != '/' || S_ISDIR (st->st_mode))
  84         return 0;
  85       if (!S_ISLNK (st->st_mode))
  86         {
  87           errno = ENOTDIR;
  88           return -1;
  89         }
  90       result = normal_fstatat (fd, file, st, flag & ~AT_SYMLINK_NOFOLLOW);
  91     }
  92   /* Fix stat behavior.  */
  93   if (result == 0 && !S_ISDIR (st->st_mode) && file[len - 1] == '/')
  94     {
  95       errno = ENOTDIR;
  96       return -1;
  97     }
  98   return result;
  99 }
 100
 101 #else /* ! (HAVE_FSTATAT && HAVE_WORKING_FSTATAT_ZERO_FLAG) */
 102
 103 /* On mingw, the gnulib <sys/stat.h> defines 'stat' as a function-like
 104    macro; but using it in AT_FUNC_F2 causes compilation failure
 105    because the preprocessor sees a use of a macro that requires two
 106    arguments but is only given one.  Hence, we need an inline
 107    forwarder to get past the preprocessor.  */
 108 static int
 109 stat_func (char const *name, struct stat *st)
 110 {
 111   return stat (name, st);
 112 }
 113
 114 /* Likewise, if there is no native 'lstat', then the gnulib
 115    <sys/stat.h> defined it as stat, which also needs adjustment.  */
 116 # if !HAVE_LSTAT
 117 #  undef lstat
 118 #  define lstat stat_func
 119 # endif
 120
 121 /* Replacement for Solaris' function by the same name.
 122    <https://www.google.com/search?q=fstatat+site:docs.oracle.com>
 123    First, try to simulate it via l?stat ("/proc/self/fd/FD/FILE").
 124    Failing that, simulate it via save_cwd/fchdir/(stat|lstat)/restore_cwd.
 125    If either the save_cwd or the restore_cwd fails (relatively unlikely),
 126    then give a diagnostic and exit nonzero.
 127    Otherwise, this function works just like Solaris' fstatat.  */
 128
 129 # define AT_FUNC_NAME fstatat
 130 # define AT_FUNC_F1 lstat
 131 # define AT_FUNC_F2 stat_func
 132 # define AT_FUNC_USE_F1_COND AT_SYMLINK_NOFOLLOW
 133 # define AT_FUNC_POST_FILE_PARAM_DECLS , struct stat *st, int flag
 134 # define AT_FUNC_POST_FILE_ARGS        , st
 135 # include "at-func.c"
 136 # undef AT_FUNC_NAME
 137 # undef AT_FUNC_F1
 138 # undef AT_FUNC_F2
 139 # undef AT_FUNC_USE_F1_COND
 140 # undef AT_FUNC_POST_FILE_PARAM_DECLS
 141 # undef AT_FUNC_POST_FILE_ARGS
 142
 143 #endif /* !HAVE_FSTATAT */