libiberty/lrealpath.c

   1 /* Libiberty realpath.  Like realpath, but more consistent behavior.
   2    Based on gdb_realpath from GDB.
   3
   4    Copyright (C) 2003-2019 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., 51 Franklin Street - Fifth Floor,
  21    Boston, MA 02110-1301, 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 #else
  68   /* cygwin has realpath, so it won't get here.  */
  69 # if defined (_WIN32)
  70 #  define WIN32_LEAN_AND_MEAN
  71 #  include <windows.h> /* for GetFullPathName */
  72 # endif
  73 #endif
  74
  75 char *
  76 lrealpath (const char *filename)
  77 {
  78   /* Method 1: The system has a compile time upper bound on a filename
  79      path.  Use that and realpath() to canonicalize the name.  This is
  80      the most common case.  Note that, if there isn't a compile time
  81      upper bound, you want to avoid realpath() at all costs.  */
  82 #if defined(REALPATH_LIMIT)
  83   {
  84     char buf[REALPATH_LIMIT];
  85     const char *rp = realpath (filename, buf);
  86     if (rp == NULL)
  87       rp = filename;
  88     return strdup (rp);
  89   }
  90 #endif /* REALPATH_LIMIT */
  91
  92   /* Method 2: The host system (i.e., GNU) has the function
  93      canonicalize_file_name() which malloc's a chunk of memory and
  94      returns that, use that.  */
  95 #if defined(HAVE_CANONICALIZE_FILE_NAME)
  96   {
  97     char *rp = canonicalize_file_name (filename);
  98     if (rp == NULL)
  99       return strdup (filename);
 100     else
 101       return rp;
 102   }
 103 #endif
 104
 105   /* Method 3: Now we're getting desperate!  The system doesn't have a
 106      compile time buffer size and no alternative function.  Query the
 107      OS, using pathconf(), for the buffer limit.  Care is needed
 108      though, some systems do not limit PATH_MAX (return -1 for
 109      pathconf()) making it impossible to pass a correctly sized buffer
 110      to realpath() (it could always overflow).  On those systems, we
 111      skip this.  */
 112 #if defined (HAVE_REALPATH) && defined (HAVE_UNISTD_H)
 113   {
 114     /* Find out the max path size.  */
 115     long path_max = pathconf ("/", _PC_PATH_MAX);
 116     if (path_max > 0)
 117       {
 118         /* PATH_MAX is bounded.  */
 119         char *buf, *rp, *ret;
 120         buf = (char *) malloc (path_max);
 121         if (buf == NULL)
 122           return NULL;
 123         rp = realpath (filename, buf);
 124         ret = strdup (rp ? rp : filename);
 125         free (buf);
 126         return ret;
 127       }
 128   }
 129 #endif
 130
 131   /* The MS Windows method.  If we don't have realpath, we assume we
 132      don't have symlinks and just canonicalize to a Windows absolute
 133      path.  GetFullPath converts ../ and ./ in relative paths to
 134      absolute paths, filling in current drive if one is not given
 135      or using the current directory of a specified drive (eg, "E:foo").
 136      It also converts all forward slashes to back slashes.  */
 137 #if defined (_WIN32)
 138   {
 139     char buf[MAX_PATH];
 140     char* basename;
 141     DWORD len = GetFullPathName (filename, MAX_PATH, buf, &basename);
 142     if (len == 0 || len > MAX_PATH - 1)
 143       return strdup (filename);
 144     else
 145       {
 146         /* The file system is case-preserving but case-insensitive,
 147            Canonicalize to lowercase, using the codepage associated
 148            with the process locale.  */
 149         CharLowerBuff (buf, len);
 150         return strdup (buf);
 151       }
 152   }
 153 #endif
 154
 155   /* This system is a lost cause, just duplicate the filename.  */
 156   return strdup (filename);
 157 }