XEmacs 21.4.19: Problem with customized folders on Windows XP

[Tony Freixas]

Benson Margulies wrote:
> Can you point me at some description of how to get off the ground as an
> XEmacs contributor.
stephen at xemacs.org wrote:
> Please do it this way:
>
> #define DONT_CHECK_DIRECTORY_WRITABLE
> #if !defined(MS_WINDOWS) || !defined(DONT_CHECK_DIRECTORY_WRITABLE)
>         /* code that does the wrong thing on windows */
> #endif
>
> and send a patch to xemacs-patches.
Benson, feel free to take this on--I don't have the time or the
expertise. Here's what I did on my system using the XEmacs 21.4.19 source:

In src/fileio.c:

DEFUN ("file-writable-p", Ffile_writable_p, 1, 1, 0, /*
Return t if file FILENAME can be written or created by you.
*/
       (filename))
{
  /* This function can GC.  GC checked 1997.04.10. */
  Lisp_Object abspath, dir;
  Lisp_Object handler;
  struct stat statbuf;
  struct gcpro gcpro1;

  CHECK_STRING (filename);
  abspath = Fexpand_file_name (filename, Qnil);

  /* If the file name has special constructs in it,
     call the corresponding file handler.  */
  GCPRO1 (abspath);
  handler = Ffind_file_name_handler (abspath, Qfile_writable_p);
  UNGCPRO;
  if (!NILP (handler))
    return call2 (handler, Qfile_writable_p, abspath);

  if (xemacs_stat ((char *) XSTRING_DATA (abspath), &statbuf) >= 0)
    return (check_writable ((char *) XSTRING_DATA (abspath))
        ? Qt : Qnil);


//   GCPRO1 (abspath);
//   dir = Ffile_name_directory (abspath);
//   UNGCPRO;
//   return (check_writable (!NILP (dir) ? (char *) XSTRING_DATA (dir)
//: "")
//       ? Qt : Qnil);

  //AF The check_writable() method doesn't work correctly on NTFS so
  //we are going to lie

  return Qt;
}

With Stephen's suggestion, the commented out section would become:

#if !defined(MS_WINDOWS) || !defined(DONT_CHECK_DIRECTORY_WRITABLE)

  GCPRO1 (abspath);
  dir = Ffile_name_directory (abspath);
  UNGCPRO;
  return (check_writable (!NILP (dir) ? (char *) XSTRING_DATA (dir)
              : "")
      ? Qt : Qnil);

#else
 
  return Qt;
 
#endif

The "right" solution would be to fix the check_writable function in the
same file:

static int
check_writable (const char *filename)
{
#ifdef MS_WINDOWS
  // Use correct access control for Windows
  // Needs to work for FAT, FAT32, NTFS and ???
  // Filename can be a file, directory, junction point(?), shortcut(??)
#else
#ifdef HAVE_EACCESS
  return (eaccess (filename, W_OK) >= 0);
#else
  /* Access isn't quite right because it uses the real uid
     and we really want to test with the effective uid.
     But Unix doesn't give us a right way to do it.
     Opening with O_WRONLY could work for an ordinary file,
     but would lose for directories.  */
  return (access (filename, W_OK) >= 0);
#endif
#endif
}

If you don't plan to take this on, let me know and I'll try to submit a
patch for the stop-gap solution.

-- 
Tony Freixas
Tiger Heron LLC
tony at tigerheron.com
http://www.tigerheron.com

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