lib/fstatat.c

   1 /* Work around an fstatat bug on Solaris 9.
   2
   3    Copyright (C) 2006, 2009-2024 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 #ifdef __osf__
  40 /* Write "sys/stat.h" here, not <sys/stat.h>, otherwise OSF/1 5.1 DTK cc
  41    eliminates this include because of the preliminary #include <sys/stat.h>
  42    above.  */
  43 # include "sys/stat.h"
  44 #else
  45 # include <sys/stat.h>
  46 #endif
  47
  48 #include "stat-time.h"
  49
  50 #include <errno.h>
  51 #include <fcntl.h>
  52 #include <stdlib.h>
  53 #include <string.h>
  54
  55 #if HAVE_FSTATAT && HAVE_WORKING_FSTATAT_ZERO_FLAG
  56
  57 # ifndef LSTAT_FOLLOWS_SLASHED_SYMLINK
  58 #  define LSTAT_FOLLOWS_SLASHED_SYMLINK 0
  59 # endif
  60
  61 static int
  62 normal_fstatat (int fd, char const *file, struct stat *st, int flag)
  63 {
  64   return stat_time_normalize (orig_fstatat (fd, file, st, flag), st);
  65 }
  66
  67 /* fstatat should always follow symbolic links that end in /, but on
  68    Solaris 9 it doesn't if AT_SYMLINK_NOFOLLOW is specified.
  69    Likewise, trailing slash on a non-directory should be an error.
  70    These are the same problems that lstat.c and stat.c address, so
  71    solve it in a similar way.
  72
  73    AIX 7.1 fstatat (AT_FDCWD, ..., 0) always fails, which is a bug.
  74    Work around this bug if FSTATAT_AT_FDCWD_0_BROKEN is nonzero.  */
  75
  76 int
  77 rpl_fstatat (int fd, char const *file, struct stat *st, int flag)
  78 {
  79   int result = normal_fstatat (fd, file, st, flag);
  80   size_t len;
  81
  82   if (LSTAT_FOLLOWS_SLASHED_SYMLINK || result != 0)
  83     return result;
  84   len = strlen (file);
  85   if (flag & AT_SYMLINK_NOFOLLOW)
  86     {
  87       /* Fix lstat behavior.  */
  88       if (file[len - 1] != '/' || S_ISDIR (st->st_mode))
  89         return 0;
  90       if (!S_ISLNK (st->st_mode))
  91         {
  92           errno = ENOTDIR;
  93           return -1;
  94         }
  95       result = normal_fstatat (fd, file, st, flag & ~AT_SYMLINK_NOFOLLOW);
  96     }
  97   /* Fix stat behavior.  */
  98   if (result == 0 && !S_ISDIR (st->st_mode) && file[len - 1] == '/')
  99     {
 100       errno = ENOTDIR;
 101       return -1;
 102     }
 103   return result;
 104 }
 105
 106 #else /* ! (HAVE_FSTATAT && HAVE_WORKING_FSTATAT_ZERO_FLAG) */
 107
 108 /* On mingw, the gnulib <sys/stat.h> defines 'stat' as a function-like
 109    macro; but using it in AT_FUNC_F2 causes compilation failure
 110    because the preprocessor sees a use of a macro that requires two
 111    arguments but is only given one.  Hence, we need an inline
 112    forwarder to get past the preprocessor.  */
 113 static int
 114 stat_func (char const *name, struct stat *st)
 115 {
 116   return stat (name, st);
 117 }
 118
 119 /* Likewise, if there is no native 'lstat', then the gnulib
 120    <sys/stat.h> defined it as stat, which also needs adjustment.  */
 121 # if !HAVE_LSTAT
 122 #  undef lstat
 123 #  define lstat stat_func
 124 # endif
 125
 126 /* Replacement for Solaris' function by the same name.
 127    <https://www.google.com/search?q=fstatat+site:docs.oracle.com>
 128    First, try to simulate it via l?stat ("/proc/self/fd/FD/FILE").
 129    Failing that, simulate it via save_cwd/fchdir/(stat|lstat)/restore_cwd.
 130    If either the save_cwd or the restore_cwd fails (relatively unlikely),
 131    then give a diagnostic and exit nonzero.
 132    Otherwise, this function works just like Solaris' fstatat.  */
 133
 134 # define AT_FUNC_NAME fstatat
 135 # define AT_FUNC_F1 lstat
 136 # define AT_FUNC_F2 stat_func
 137 # define AT_FUNC_USE_F1_COND AT_SYMLINK_NOFOLLOW
 138 # define AT_FUNC_POST_FILE_PARAM_DECLS , struct stat *st, int flag
 139 # define AT_FUNC_POST_FILE_ARGS        , st
 140 # include "at-func.c"
 141 # undef AT_FUNC_NAME
 142 # undef AT_FUNC_F1
 143 # undef AT_FUNC_F2
 144 # undef AT_FUNC_USE_F1_COND
 145 # undef AT_FUNC_POST_FILE_PARAM_DECLS
 146 # undef AT_FUNC_POST_FILE_ARGS
 147
 148 #endif /* !HAVE_FSTATAT */