bug#46256: [feature/native-comp] AOT eln files ignored if run from build tree

[Eli Zaretskii]

> Cc: 46256@debbugs.gnu.org
> Date: Thu, 18 Feb 2021 21:00:29 +0000
> From:  Andrea Corallo via "Bug reports for GNU Emacs,
>  the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
> 
> >> Last queston: do reverse slashes '\' appear somewhere in those
> >> filenames?  This was issue I tried to fix with the blind patch I've
> >> sent.
> >
> > As Eli pointed out, that is not the problem: forward slashes are ok.
> 
> I understand they are handled, but here as we do a substitution we must
> substitute what's coming in.
> 
> As you have the possibility to debug this piece of code on Windows
> please have a look at this (or try my blind patch if you haven't).

If the problem is with hashing file names, you will have to
canonicalize them first, including resolving the letter-case issue,
the forward/back-slashes issue, and also the issue with those pesky
numerical tails Windows sometimes produces.  We have a function
Fw32_long_file_name for that purpose, I think you should use it (if
you need it for C strings, we could add a wrapper around
w32_get_long_filename to do that instead).  This assumes that you are
talking about existing files; if that assumption is not true, we will
need a slightly different strategy.