bug#71500: 28.2; Can't create/open .gpg file name contains non-ascii encoding in windows

[Eli Zaretskii <eliz@gnu.org>]

> Date: Sat, 29 Jun 2024 21:39:38 +0900
> From: Kazuhiro Ito <kzhr@d1.dion.ne.jp>
> Cc: 71500@debbugs.gnu.org,
> 	billy.hotwind@gmail.com
> 
> > > As Tatsuya wrote, epg--start function calls gpg2 program with setting
> > > :coding property to raw-text, thus each argument should be encoded in
> > > proper coding system by a caller.  The problem would occur on any OS
> > > whose file name coding system was not utf-8.
> > > 
> > > For example, in case of epg-decrypt-file, following change is required
> > > if we need to set :coding property to raw-text for ENCODING.
> > > 
> > > diff --git a/lisp/epg.el b/lisp/epg.el
> > > index 7bec91f616d..59870761565 100644
> > > --- a/lisp/epg.el
> > > +++ b/lisp/epg.el
> > > @@ -1468,7 +1468,10 @@ epg-decrypt-file
> > >        (progn
> > >  	(setf (epg-context-output-file context)
> > >                (or plain (make-temp-file "epg-output")))
> > > -	(epg-start-decrypt context (epg-make-data-from-file cipher))
> > > +	(epg-start-decrypt context
> > > +                           (epg-make-data-from-file
> > > +                            (encode-coding-string
> > > +                             cipher file-name-coding-system)))
> > >  	(epg-wait-for-completion context)
> > >  	(epg--check-error-for-decrypt context)
> > >  	(unless plain
> > 
> > Thanks, but this doesn't look right to me.  The problem is likely in
> > the fact that epg--start sets the encoding/decoding for the epg
> > process to raw-text in a way that is too broad: it affects not only
> > how we encode and decode text sent to and received from GnuPG, but
> > also how its command-line arguments are encoded.  And that's not what
> > we want.
> > 
> > So I think the right fix is in epg--start: instead of setting :coding
> > as part of the make-process call, it should call
> > set-process-coding-system _after_ the make-process call, so that
> > raw-text will affect only the text we send and receive from gpg.
> > 
> > Can you try such a change and see if it fixes the problem?
> 
> I tested attached patch and confirmed the issue was resolved.

Thanks, installed on the emacs-30 release branch, and closing the bug.

> I'm not sure that :coding setting for decoding in make-process can
> be removed.  I mean, I don't know whether Emacs can receive output
> from process between make-process and set-process-coding-system.

Emacs is a single-threaded program, so until epg--start returns, no
output can be received and decoded by Emacs from the gpg sub-process.
So this is safe.