Re: [PATCH] Cygwin: pinfo: Align CTTY behavior to the statement of POSIX.

[Corinna Vinschen <corinna-cygwin@cygwin.com>]

Hi Takashi,

On Dec 20 21:41, Takashi Yano wrote:
> POSIX states "A terminal may be the controlling terminal for at most
> one session."
> https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap11.html
> 
> However, in cygwin, multiple sessions could be associated with the
> same TTY. This patch aligns CTTY behavior to the statement of POSIX.
> 
> Signed-off-by: Takashi Yano <takashi.yano@nifty.ne.jp>
> ---
>  winsup/cygwin/fhandler/termios.cc | 6 +++++-
>  winsup/cygwin/mm/cygheap.cc       | 2 ++
>  winsup/cygwin/pinfo.cc            | 4 +++-
>  3 files changed, 10 insertions(+), 2 deletions(-)

Do you want to handle this as bug (3.4) or extension (3.5)?

> diff --git a/winsup/cygwin/pinfo.cc b/winsup/cygwin/pinfo.cc
> index e086ab9a8..749a4064c 100644
> --- a/winsup/cygwin/pinfo.cc
> +++ b/winsup/cygwin/pinfo.cc
> @@ -528,7 +528,9 @@ _pinfo::set_ctty (fhandler_termios *fh, int flags)
>  {
>    tty_min& tc = *fh->tc ();
>    debug_printf ("old %s, ctty device number %y, tc.ntty device number %y flags & O_NOCTTY %y", __ctty (), ctty, tc.ntty, flags & O_NOCTTY);
> -  if (fh && (ctty <= 0 || ctty == tc.ntty) && !(flags & O_NOCTTY))
> +  if (tc.getsid () && tc.getsid () != pid)
> +    ; /* Do not attach if another session already attached to the CTTY. */

I'm sure I'm missing something, but I'm a bit puzzled about the

  tc.getsid () != pid

test here.  If that's not the case, this process is the process group
leader and already has a controlling tty, isn't it?


Thanks,
Corinna