bug#33154: 27.0.50; create_process on Darwin should not invoke setsid() after vfork() [PATCH]

[Alan Third <alan@idiocy.org>]

On Tue, Nov 06, 2018 at 11:41:46PM -0800, Paul Eggert wrote:
> Filipp Gunbin wrote:
> > In your patch, we don't detach from current (Emacs's) controlling
> > terminal before doing TIOCSCTTY.
> 
> Ah, OK. I see also that vfork won't work on Darwin if pty mode is used,
> since Emacs wants to create a new session and Darwin setsid always fails in
> a vforked child that has not yet execed.
> 
> However, your patch introduces another duplicate of the open/TIOCNOTTY/close
> fallback code, making three duplicates in all. How about if we coalesce
> these duplicates into a function and then call that function? Also, I think
> we can call the function from just two places (not three). Furthermore, I
> think it'd be more robust if Emacs does setsid everywhere (with a fallback
> to open/TIOCNOTTY/close everywhere TIOCNOTTY is available), not just Darwin.
> Proposed patch (against master) attached.

I only have two tests I know of to try here and they both pass with
this patch:

1. M‐x shell RET bg REST

doesn’t report that there’s no job control.

2. (benchmark 1 '(call-process "/usr/bin/true" nil nil nil))

Returns times in the order of 3ms, which is what we’d expect to see.

I’m not even sure if they’re really relevant, tbh. Is there anything
else I should try?
-- 
Alan Third