Andrea Corallo via "Bug reports for GNU Emacs, the Swiss army knife of
text editors" <bug-gnu-emacs@gnu.org> writes:

> Eli Zaretskii <eliz@gnu.org> writes:
>
>>> From: Andrea Corallo <akrl@sdf.org>
>>> Cc: 48578@debbugs.gnu.org
>>> Date: Tue, 25 May 2021 12:34:27 +0000
>>> 
>>> +  /* Use `file-truename' or fall back to 'realpath' `expand-file-name'
>>> +     when the first is not available.  (`file-truename' is not
>>> +     available only for a short phases of the bootstrap before file.el
>>> +     is loaded).  */
>>> +
>>> +  if (NILP (Ffboundp (intern_c_string ("file-truename"))))
>>> +    {
>>> +#ifndef WINDOWSNT
>>> +      char *file_normalized = realpath (SSDATA (filename), NULL);
>>> +#else
>>> +      char *file_normalized = ??? ;
>>> +#endif
>>> +      filename = Fexpand_file_name (build_string (file_normalized), Qnil);
>>> +      xfree (file_normalized);
>>> +    }
>>> +  else
>>> +    filename = CALL1I (file-truename, filename);
>>>  
>>>    if (NILP (Ffile_exists_p (filename)))
>>>      xsignal1 (Qfile_missing, filename);
>>
>> Thanks, I will try that.  But why not use realpath at all times, even
>> if file-truename is available?  They do the same thing, AFAIK, no?
>
> AFAIK yes but the file-truename implementation didn't look sufficiently
> trivial to be sure they are really equivalent with the quick skim I had.
>
> I agree with the idea of using always one (realpath), should be also
> easier to ideantify issues in case.
>
> Attached the updated patch.

Well... attached updating also the comment.

  Andrea