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 #ifdef HAVE_FCNTL_H
  53 #include <fcntl.h>
  54 #endif
  55
  56 /* On GNU libc systems the declaration is only visible with _GNU_SOURCE.  */
  57 #if defined(HAVE_CANONICALIZE_FILE_NAME) \
  58     && defined(NEED_DECLARATION_CANONICALIZE_FILE_NAME)
  59 extern char *canonicalize_file_name (const char *);
  60 #endif
  61
  62 #if defined(HAVE_REALPATH)
  63 # if defined (PATH_MAX)
  64 #  define REALPATH_LIMIT PATH_MAX
  65 # else
  66 #  if defined (MAXPATHLEN)
  67 #   define REALPATH_LIMIT MAXPATHLEN
  68 #  endif
  69 # endif
  70 #else
  71   /* cygwin has realpath, so it won't get here.  */
  72 # if defined (_WIN32)
  73 #  define WIN32_LEAN_AND_MEAN
  74 #  include <windows.h> /* for GetFullPathName */
  75 # endif
  76 #endif
  77
  78 char *
  79 lrealpath (const char *filename)
  80 {
  81   /* Method 1: The system has a compile time upper bound on a filename
  82      path.  Use that and realpath() to canonicalize the name.  This is
  83      the most common case.  Note that, if there isn't a compile time
  84      upper bound, you want to avoid realpath() at all costs.  */
  85 #if defined(REALPATH_LIMIT)
  86   {
  87     char buf[REALPATH_LIMIT];
  88     const char *rp = realpath (filename, buf);
  89     if (rp == NULL)
  90       rp = filename;
  91     return strdup (rp);
  92   }
  93 #endif /* REALPATH_LIMIT */
  94
  95   /* Method 2: The host system (i.e., GNU) has the function
  96      canonicalize_file_name() which malloc's a chunk of memory and
  97      returns that, use that.  */
  98 #if defined(HAVE_CANONICALIZE_FILE_NAME)
  99   {
 100     char *rp = canonicalize_file_name (filename);
 101     if (rp == NULL)
 102       return strdup (filename);
 103     else
 104       return rp;
 105   }
 106 #endif
 107
 108   /* Method 3: Now we're getting desperate!  The system doesn't have a
 109      compile time buffer size and no alternative function.  Query the
 110      OS, using pathconf(), for the buffer limit.  Care is needed
 111      though, some systems do not limit PATH_MAX (return -1 for
 112      pathconf()) making it impossible to pass a correctly sized buffer
 113      to realpath() (it could always overflow).  On those systems, we
 114      skip this.  */
 115 #if defined (HAVE_REALPATH) && defined (HAVE_UNISTD_H)
 116   {
 117     /* Find out the max path size.  */
 118     long path_max = pathconf ("/", _PC_PATH_MAX);
 119     if (path_max > 0)
 120       {
 121         /* PATH_MAX is bounded.  */
 122         char *buf, *rp, *ret;
 123         buf = (char *) malloc (path_max);
 124         if (buf == NULL)
 125           return NULL;
 126         rp = realpath (filename, buf);
 127         ret = strdup (rp ? rp : filename);
 128         free (buf);
 129         return ret;
 130       }
 131   }
 132 #endif
 133
 134   /* The MS Windows method.  If we don't have realpath, we assume we
 135      don't have symlinks and just canonicalize to a Windows absolute
 136      path.  GetFullPath converts ../ and ./ in relative paths to
 137      absolute paths, filling in current drive if one is not given
 138      or using the current directory of a specified drive (eg, "E:foo").
 139      It also converts all forward slashes to back slashes.  */
 140 #if defined (_WIN32)
 141   {
 142     char buf[MAX_PATH];
 143     char* basename;
 144     DWORD len = GetFullPathName (filename, MAX_PATH, buf, &basename);
 145     if (len == 0 || len > MAX_PATH - 1)
 146       return strdup (filename);
 147     else
 148       {
 149         /* The file system is case-preserving but case-insensitive,
 150            Canonicalize to lowercase, using the codepage associated
 151            with the process locale.  */
 152         CharLowerBuff (buf, len);
 153         return strdup (buf);
 154       }
 155   }
 156 #endif
 157
 158   /* This system is a lost cause, just duplicate the filename.  */
 159   return strdup (filename);
 160 }
 161
 162 /* Return true when FD file descriptor exists.  */
 163
 164 int
 165 is_valid_fd (int fd)
 166 {
 167 #if defined(_WIN32)
 168   HANDLE h = (HANDLE) _get_osfhandle (fd);
 169   return h != (HANDLE) -1;
 170 #else
 171   return fcntl (fd, F_GETFD) >= 0;
 172 #endif
 173 }