lib/stat.c

   1 /* Work around the bug in some systems whereby stat/lstat succeeds when
   2    given the zero-length file name argument.  The stat/lstat from SunOS4.1.4
   3    has this bug.
   4    Copyright (C) 1997-2002 Free Software Foundation, Inc.
   5
   6    This program is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 2, or (at your option)
   9    any later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program; if not, write to the Free Software Foundation,
  18    Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
  19
  20 /* written by Jim Meyering */
  21
  22 #include <config.h>
  23
  24 #include <sys/types.h>
  25 #include <sys/stat.h>
  26 #include <errno.h>
  27 #ifndef errno
  28 extern int errno;
  29 #endif
  30 #ifdef LSTAT
  31 # include <string.h>
  32
  33 # if HAVE_STDLIB_H
  34 #  include <stdlib.h>
  35 # endif
  36
  37 # ifdef STAT_MACROS_BROKEN
  38 #  undef S_ISLNK
  39 # endif
  40
  41 # ifndef S_ISLNK
  42 #  ifdef S_IFLNK
  43 #   define S_ISLNK(m) (((m) & S_IFMT) == S_IFLNK)
  44 #  else
  45 #   define S_ISLNK(m) 0
  46 #  endif
  47 # endif
  48
  49 # ifndef HAVE_DECL_FREE
  50 "this configure-time declaration test was not run"
  51 # endif
  52 # if !HAVE_DECL_FREE
  53 void free ();
  54 # endif
  55
  56 char *xmalloc ();
  57
  58 /* lstat works differently on Linux and Solaris systems.  POSIX (see
  59    `pathname resolution' in the glossary) requires that programs like `ls'
  60    take into consideration the fact that FILE has a trailing slash when
  61    FILE is a symbolic link.  On Linux systems, the lstat function already
  62    has the desired semantics (in treating `lstat("symlink/",sbuf)' just like
  63    `lstat("symlink/.",sbuf)', but on Solaris it does not.
  64
  65    If FILE has a trailing slash and specifies a symbolic link,
  66    then append a `.' to FILE and call lstat a second time.  */
  67
  68 static int
  69 slash_aware_lstat (const char *file, struct stat *sbuf)
  70 {
  71   size_t len;
  72   char *new_file;
  73
  74   int lstat_result = lstat (file, sbuf);
  75
  76   if (lstat_result != 0 || !S_ISLNK (sbuf->st_mode))
  77     return lstat_result;
  78
  79   len = strlen (file);
  80   if (file[len - 1] != '/')
  81     return lstat_result;
  82
  83   /* FILE refers to a symbolic link and the name ends with a slash.
  84      Append a `.' to FILE and repeat the lstat call.  */
  85
  86   /* Add one for the `.' we'll append, and one more for the trailing NUL.  */
  87   new_file = xmalloc (len + 1 + 1);
  88   memcpy (new_file, file, len);
  89   new_file[len] = '.';
  90   new_file[len + 1] = 0;
  91
  92   lstat_result = lstat (new_file, sbuf);
  93   free (new_file);
  94
  95   return lstat_result;
  96 }
  97 #endif /* LSTAT */
  98
  99 /* This is a wrapper for stat/lstat.
 100    If FILE is the empty string, fail with errno == ENOENT.
 101    Otherwise, return the result of calling the real stat/lstat.
 102
 103    This works around the bug in some systems whereby stat/lstat succeeds when
 104    given the zero-length file name argument.  The stat/lstat from SunOS4.1.4
 105    has this bug.  */
 106
 107 /* This function also provides a version of lstat with consistent semantics
 108    when FILE specifies a symbolic link and has a trailing slash.  */
 109
 110 #ifdef LSTAT
 111 # define rpl_xstat rpl_lstat
 112 # define xstat_return_val(F, S) slash_aware_lstat (F, S)
 113 #else
 114 # define rpl_xstat rpl_stat
 115 # define xstat_return_val(F, S) stat (F, S)
 116 #endif
 117
 118 int
 119 rpl_xstat (const char *file, struct stat *sbuf)
 120 {
 121   if (file && *file == 0)
 122     {
 123       errno = ENOENT;
 124       return -1;
 125     }
 126
 127   return xstat_return_val (file, sbuf);
 128 }