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.