bug#31901: Incorrect make-network-process + nowait state handling for non-existing unix sockets in emacs-26.1

[Eli Zaretskii]

Ping!

Lars, could you please look into this?

> From: Noam Postavsky <npostavs@gmail.com>
> Date: Sun, 01 Jul 2018 11:21:06 -0400
> Cc: Lars Ingebrigtsen <larsi@gnus.org>, 31901@debbugs.gnu.org
> 
> tags 31901 + confirmed
> quit
> 
> Mike Kazantsev <mk.fraggod@gmail.com> writes:
> 
> > As far as I can tell, this is not documented behavior, definitely
> > unexpected, breaks all old code that used unix sockets, and probably
> > unintentional, i.e. a bug.
> 
> It seems to be due to this is_non_blocking_client check in
> connect_network_socket:
> 
>   if (s < 0)
>     {
>       /* If non-blocking got this far - and failed - assume non-blocking is
>          not supported after all.  This is probably a wrong assumption, but
>          the normal blocking calls to open-network-stream handles this error
>          better.  */
>       if (p->is_non_blocking_client)
>         return;
> 
>       report_file_errno ((p->is_server
>                           ? "make server process failed"
>                           : "make client process failed"),
>                          contact, xerrno);
>     }
> 
> In Emacs 25, this check was directly in Fmake_network_process before the
> process object creation code, so we would just return nil in that case.
> Seems to have changed, I assume accidentally, in [1: e09c0972c3].
> 
> [1: e09c0972c3]: 2016-01-28 23:50:47 +0100
>   Refactor make_network_process
>   
> https://git.savannah.gnu.org/cgit/emacs.git/commit/?id=e09c0972c350e9411683b509414fc598cbf387d3
> 
> 
> 
>