libiberty/lrealpath.c

   1 /* Libiberty realpath.  Like realpath, but more consistent behavior.
   2    Based on gdb_realpath from GDB.
   3
   4    Copyright 2003 Free Software Foundation, Inc.
   5
   6    This file is part of the libiberty library.
   7
   8    This program is free software; you can redistribute it and/or modify
   9    it under the terms of the GNU General Public License as published by
  10    the Free Software Foundation; either version 2 of the License, or
  11    (at your option) any later version.
  12
  13    This program is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16    GNU General Public License for more details.
  17
  18    You should have received a copy of the GNU General Public License
  19    along with this program; if not, write to the Free Software
  20    Foundation, Inc., 59 Temple Place - Suite 330,
  21    Boston, MA 02111-1307, USA.  */
  22
  23 /*
  24
  25 @deftypefn Replacement {const char*} lrealpath (const char *@var{name})
  26
  27 Given a pointer to a string containing a pathname, returns a canonical
  28 version of the filename.  Symlinks will be resolved, and ``.'' and ``..''
  29 components will be simplified.  The returned value will be allocated using
  30 @code{malloc}, or @code{NULL} will be returned on a memory allocation error.
  31
  32 @end deftypefn
  33
  34 */
  35
  36 #include "config.h"
  37 #include "ansidecl.h"
  38 #include "libiberty.h"
  39
  40 #ifdef HAVE_LIMITS_H
  41 #include <limits.h>
  42 #endif
  43 #ifdef HAVE_STDLIB_H
  44 #include <stdlib.h>
  45 #endif
  46 #ifdef HAVE_UNISTD_H
  47 #include <unistd.h>
  48 #endif
  49 #ifdef HAVE_STRING_H
  50 #include <string.h>
  51 #endif
  52
  53 /* On GNU libc systems the declaration is only visible with _GNU_SOURCE.  */
  54 #if defined(HAVE_CANONICALIZE_FILE_NAME) \
  55     && defined(NEED_DECLARATION_CANONICALIZE_FILE_NAME)
  56 extern char *canonicalize_file_name (const char *);
  57 #endif
  58
  59 #if defined(HAVE_REALPATH)
  60 # if defined (PATH_MAX)
  61 #  define REALPATH_LIMIT PATH_MAX
  62 # else
  63 #  if defined (MAXPATHLEN)
  64 #   define REALPATH_LIMIT MAXPATHLEN
  65 #  endif
  66 # endif
  67 #endif
  68
  69 char *
  70 lrealpath (filename)
  71      const char *filename;
  72 {
  73   /* Method 1: The system has a compile time upper bound on a filename
  74      path.  Use that and realpath() to canonicalize the name.  This is
  75      the most common case.  Note that, if there isn't a compile time
  76      upper bound, you want to avoid realpath() at all costs.  */
  77 #if defined(REALPATH_LIMIT)
  78   {
  79     char buf[REALPATH_LIMIT];
  80     const char *rp = realpath (filename, buf);
  81     if (rp == NULL)
  82       rp = filename;
  83     return strdup (rp);
  84   }
  85 #endif /* REALPATH_LIMIT */
  86
  87   /* Method 2: The host system (i.e., GNU) has the function
  88      canonicalize_file_name() which malloc's a chunk of memory and
  89      returns that, use that.  */
  90 #if defined(HAVE_CANONICALIZE_FILE_NAME)
  91   {
  92     char *rp = canonicalize_file_name (filename);
  93     if (rp == NULL)
  94       return strdup (filename);
  95     else
  96       return rp;
  97   }
  98 #endif
  99
 100   /* Method 3: Now we're getting desperate!  The system doesn't have a
 101      compile time buffer size and no alternative function.  Query the
 102      OS, using pathconf(), for the buffer limit.  Care is needed
 103      though, some systems do not limit PATH_MAX (return -1 for
 104      pathconf()) making it impossible to pass a correctly sized buffer
 105      to realpath() (it could always overflow).  On those systems, we
 106      skip this.  */
 107 #if defined (HAVE_REALPATH) && defined (HAVE_UNISTD_H)
 108   {
 109     /* Find out the max path size.  */
 110     long path_max = pathconf ("/", _PC_PATH_MAX);
 111     if (path_max > 0)
 112       {
 113         /* PATH_MAX is bounded.  */
 114         char *buf, *rp, *ret;
 115         buf = malloc (path_max);
 116         if (buf == NULL)
 117           return NULL;
 118         rp = realpath (filename, buf);
 119         ret = strdup (rp ? rp : filename);
 120         free (buf);
 121         return ret;
 122       }
 123   }
 124 #endif
 125
 126   /* This system is a lost cause, just duplicate the filename.  */
 127   return strdup (filename);
 128 }