Re: [PATCH v3 2/2] Use O_IGNORE_CTTY where appropriate

[Paul Eggert]

On 2023-06-04 13:42, Sergey Bugaev via Libc-alpha wrote:
> -  int flags = O_RDONLY | O_NONBLOCK | O_DIRECTORY | O_CLOEXEC;
> +  int flags = O_RDONLY | O_NONBLOCK | O_DIRECTORY | O_CLOEXEC | O_IGNORE_CTTY;

Why is O_IGNORE_CTTY useful here? O_DIRECTORY means that the file cannot 
be a tty. (If GNU/Hurd is sending an extra RPC in this case, surely 
that's a performance bug that should be fixed in _hurd_port2fd or 
whatever, not in every 'open' caller.)

> -         open_flags = O_RDWR | O_CREAT | O_EXCL | O_CLOEXEC;
> +         open_flags = O_RDWR | O_CREAT | O_EXCL | O_CLOEXEC | O_IGNORE_CTTY;

Similarly, why is O_IGNORE_CTTY useful here? O_CREAT | O_EXCL means that 
the file cannot be a tty. (There are a couple of instances of this.)

> I'm still interested in whether there could be a way to pass
> O_IGNORE_CTTY when using fopen () too -- but that doesn't have to block
> this patchset either.

I suppose fopen could add a new 'T' flag, as a GNU extension, that would 
add O_IGNORE_CTTY to the open flags.