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Re: [PATCH] getpt: use /dev/pts/ptmx as default ptmx master
- From: Zack Weinberg <zackw at panix dot com>
- To: Christian Brauner <christian dot brauner at ubuntu dot com>
- Cc: ebiederm at xmission dot com, GNU C Library <libc-alpha at sourceware dot org>
- Date: Thu, 15 Mar 2018 10:02:56 -0400
- Subject: Re: [PATCH] getpt: use /dev/pts/ptmx as default ptmx master
- References: <firstname.lastname@example.org>
On Thu, Mar 15, 2018 at 8:06 AM, Christian Brauner
> For a long time now Linux has placed the ptmx character device directly
> under the devpts mount at /dev/pts/ptmx.
Exactly which kernel version started doing this?
> It is time to start switching to using /dev/pts/ptmx and use /dev/ptmx as a
> fallback only.
Application code is entitled to do open ('/dev/ptmx", O_RDWR) itself
rather than calling posix_openpt. It is not OK to break those
applications. That was the recommended practice prior to the
introduction of posix_openpt, and I am suspicious of posix_openpt not
existing on still-reasonable portability targets.
Since /dev/ptmx must stick around for the sake of those applications,
I am inclined to say that libc's posix_openpt should continue using
/dev/ptmx as well, in order to ensure that that configuration
continues to be tested. I am also inclined to say that, on new
kernels where the devpts filesystem provides the ptmx node, using a
bind-mount rather than a symlink for /dev/ptmx is a misconfiguration
(and on older kernels, obviously it needs to be an actual device