lib/lstat.c

   1 /* Work around a bug of lstat on some systems
   2
   3    Copyright (C) 1997-2006, 2008-2024 Free Software Foundation, Inc.
   4
   5    This file is free software: you can redistribute it and/or modify
   6    it under the terms of the GNU Lesser General Public License as
   7    published by the Free Software Foundation; either version 2.1 of the
   8    License, or (at your option) any later version.
   9
  10    This file 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 Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public License
  16    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  17
  18 /* written by 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_lstat doesn't recurse to
  22    rpl_lstat.  */
  23 #define __need_system_sys_stat_h
  24 #include <config.h>
  25
  26 #if !HAVE_LSTAT
  27 /* On systems that lack symlinks, our replacement <sys/stat.h> already
  28    defined lstat as stat, so there is nothing further to do other than
  29    avoid an empty file.  */
  30 typedef int dummy;
  31 #else /* HAVE_LSTAT */
  32
  33 /* Get the original definition of lstat.  It might be defined as a macro.  */
  34 # include <sys/types.h>
  35 # include <sys/stat.h>
  36 # undef __need_system_sys_stat_h
  37
  38 static int
  39 orig_lstat (const char *filename, struct stat *buf)
  40 {
  41   return lstat (filename, buf);
  42 }
  43
  44 /* Specification.  */
  45 # ifdef __osf__
  46 /* Write "sys/stat.h" here, not <sys/stat.h>, otherwise OSF/1 5.1 DTK cc
  47    eliminates this include because of the preliminary #include <sys/stat.h>
  48    above.  */
  49 #  include "sys/stat.h"
  50 # else
  51 #  include <sys/stat.h>
  52 # endif
  53
  54 # include "stat-time.h"
  55
  56 # include <string.h>
  57 # include <errno.h>
  58
  59 /* lstat works differently on Linux and Solaris systems.  POSIX (see
  60    "pathname resolution" in the glossary) requires that programs like
  61    'ls' take into consideration the fact that FILE has a trailing slash
  62    when FILE is a symbolic link.  On Linux and Solaris 10 systems, the
  63    lstat function already has the desired semantics (in treating
  64    'lstat ("symlink/", sbuf)' just like 'lstat ("symlink/.", sbuf)',
  65    but on Solaris 9 and earlier it does not.
  66
  67    If FILE has a trailing slash and specifies a symbolic link,
  68    then use stat() to get more info on the referent of FILE.
  69    If the referent is a non-directory, then set errno to ENOTDIR
  70    and return -1.  Otherwise, return stat's result.  */
  71
  72 int
  73 rpl_lstat (const char *file, struct stat *sbuf)
  74 {
  75   int result = orig_lstat (file, sbuf);
  76
  77   /* This replacement file can blindly check against '/' rather than
  78      using the ISSLASH macro, because all platforms with '\\' either
  79      lack symlinks (mingw) or have working lstat (cygwin) and thus do
  80      not compile this file.  0 len should have already been filtered
  81      out above, with a failure return of ENOENT.  */
  82   if (result == 0)
  83     {
  84       if (S_ISDIR (sbuf->st_mode) || file[strlen (file) - 1] != '/')
  85         result = stat_time_normalize (result, sbuf);
  86       else
  87         {
  88           /* At this point, a trailing slash is permitted only on
  89              symlink-to-dir; but it should have found information on the
  90              directory, not the symlink.  Call 'stat' to get info about the
  91              link's referent.  Our replacement stat guarantees valid results,
  92              even if the symlink is not pointing to a directory.  */
  93           if (!S_ISLNK (sbuf->st_mode))
  94             {
  95               errno = ENOTDIR;
  96               return -1;
  97             }
  98           result = stat (file, sbuf);
  99         }
 100     }
 101   return result;
 102 }
 103
 104 #endif /* HAVE_LSTAT */