On 04/06/23 17:42, Sergey Bugaev via Libc-alpha wrote:
> This internal definition makes it possible to use O_IGNORE_CTTY in
> the glibc codebase unconditionally, no matter whether the current port
> provides it or not (i.e. both on Hurd and on Linux). Along with the
> definition, this adds a small guide on when O_IGNORE_CTTY is to be used.
>
> The following commit will actually make use of O_IGNORE_CTTY
> throughout the glibc codebase.
>
> Signed-off-by: Sergey Bugaev <buga...@gmail.com>
> ---
> include/fcntl.h | 15 +++++++++++++++
> 1 file changed, 15 insertions(+)
>
> diff --git a/include/fcntl.h b/include/fcntl.h
> index be435047..d788db2e 100644
> --- a/include/fcntl.h
> +++ b/include/fcntl.h
> @@ -33,6 +33,21 @@ extern int __openat_2 (int __fd, const char *__path, int
> __oflag);
> extern int __openat64_2 (int __fd, const char *__path, int __oflag);
>
>
> +/* Makes open () & friends faster on the Hurd, but can only be used (without
> + altering user-visible behavior) when we're sure that the file we're
> opening
> + is not (at the moment) our controlling terminal. Use this when:
> + - opening well-known files internally (utmp, nss db);
> + - opening files with user-specified names that can not reasonably be ttys
> + (sem_open, shm_open);
> + - opening new (previously unused) ttys (openpty).
> + Don't use this when:
> + - doing a general-purpose open () with a user-controlled path that could
> + well be "/dev/tty" (fopen). */
> +#ifndef O_IGNORE_CTTY
> +# define O_IGNORE_CTTY 0
> +#endif
> +
I think it would be better to add a sysdeps/unix/sysv/linux/fcntl.h which
defines O_IGNORE_CTTY unconditionally and include the default one (either
directly or though include_next.h). We currently are trying to avoid the
"#ifdef ...", so a code that does not define, where is should, would fail
at compile time.
> +
> #if IS_IN (rtld)
> # include <dl-fcntl.h>
> #endif
