From: Philip Guenther <guenther@gmail.com>
Subject: Re: Implement tcgetwinsize and tcsetwinsize
To: enh <enh@google.com>
Cc: finxx <me@finxx.xyz>, tech@openbsd.org
Date: Sun, 23 Feb 2025 15:38:46 -0800

On Sun, Feb 23, 2025 at 3:24 PM enh <enh@google.com> wrote:
>
> On Sun, Feb 23, 2025 at 2:14 PM finxx <me@finxx.xyz> wrote:
> >
> > tcgetwinsize(3) and tcsetwinsize(3) have existed in POSIX for years,
>
> well, since 2024's issue 8 anyway.
>
> > and
> > been supported on the other BSDs for just as long. This patch implements
> > them in libc.
> >
> > diff 11d817a3382201927643a2ae0a36dcc4048bfb0b HEAD
> > commit - 11d817a3382201927643a2ae0a36dcc4048bfb0b
> > commit + c077581a317e8f39c250c631d6d29b01a97e7f8a
> > blob - 6eb2cca93e5f1c834a57a03af4a4b3fe27c64ce1
> > blob + 18cf144e7a06b88f2514407c57cda12d192d7709
> > --- lib/libc/Symbols.list
> > +++ lib/libc/Symbols.list
> > @@ -1700,9 +1700,11 @@ tcflush
> >  tcgetattr
> >  tcgetpgrp
> >  tcgetsid
> > +tcgetwinsize
> >  tcsendbreak
> >  tcsetattr
> >  tcsetpgrp
> > +tcsetwinsize
> >
> >  /* thread */
> >  _rthread_debug
> > blob - 85c1d52273c9cb24478c2c7e67a79bbdd86dae51
> > blob + a1aff88ae34741f62149e88c69c93f6b5b7326c6
> > --- lib/libc/termios/Makefile.inc
> > +++ lib/libc/termios/Makefile.inc
> > @@ -4,6 +4,7 @@
> >
> >  SRCS+= cfgetispeed.c cfgetospeed.c cfmakeraw.c cfsetispeed.c cfsetospeed.c \
> >         cfsetspeed.c tcdrain.c tcflow.c tcflush.c tcgetattr.c tcgetpgrp.c \
> > -       tcsendbreak.c tcsetattr.c tcsetpgrp.c tcgetsid.c
> > +       tcsendbreak.c tcsetattr.c tcsetpgrp.c tcgetsid.c tcgetwinsize.c \
> > +       tcsetwinsize.c
> >
> >  MAN+=  tcgetpgrp.3 tcsendbreak.3 tcsetattr.3 tcsetpgrp.3 tcgetsid.3
> > blob - /dev/null
> > blob + c41b49129a7c60230f20f727ce90f7e4b089cd30 (mode 644)
> > --- /dev/null
> > +++ lib/libc/termios/tcgetwinsize.c
> > @@ -0,0 +1,24 @@
> > +/*
> > + * Copyright (c) 2025 Finxx <me@finxx.xyz>
> > + *
> > + * Permission to use, copy, modify, and distribute this software for any
> > + * purpose with or without fee is hereby granted, provided that the above
> > + * copyright notice and this permission notice appear in all copies.
> > + *
> > + * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
> > + * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
> > + * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
> > + * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
> > + * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
> > + * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
> > + * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
> > + */
> > +
> > +#include <sys/ioctl.h>
> > +#include <termios.h>
> > +
> > +int
> > +tcgetwinsize(int fd, struct winsize *winsize_p)
> > +{
> > +       return (ioctl(fd, TIOCGWINSZ, winsize_p));
> > +}
> > blob - /dev/null
> > blob + 7e652d5f8457bb752b724c14cbfbdd9dc15f0564 (mode 644)
> > --- /dev/null
> > +++ lib/libc/termios/tcsetwinsize.c
> > @@ -0,0 +1,24 @@
> > +/*
> > + * Copyright (c) 2025 Finxx <me@finxx.xyz>
> > + *
> > + * Permission to use, copy, modify, and distribute this software for any
> > + * purpose with or without fee is hereby granted, provided that the above
> > + * copyright notice and this permission notice appear in all copies.
> > + *
> > + * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
> > + * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
> > + * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
> > + * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
> > + * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
> > + * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
> > + * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
> > + */
> > +
> > +#include <sys/ioctl.h>
> > +#include <termios.h>
> > +
> > +int
> > +tcsetwinsize(int fd, const struct winsize *winsize_p)
> > +{
> > +       return (ioctl(fd, TIOCSWINSZ, winsize_p));
> > +}
> > blob - 681c29489138850507516a8ef6bc346bed04e4e9
> > blob + 62a2d7a676481ae3fd947c15e237d4a5b018c1ca
> > --- sys/sys/termios.h
> > +++ sys/sys/termios.h
> > @@ -272,6 +272,8 @@ int tcdrain(int);
> >  int    tcflow(int, int);
> >  int    tcflush(int, int);
> >  int    tcsendbreak(int, int);
> > +int    tcgetwinsize(int, struct winsize *);
> > +int    tcsetwinsize(int, const struct winsize *);
> >
> >  #if __XPG_VISIBLE >= 420 || __POSIX_VISIBLE >= 200809
>
> this makes me wonder whether tcgetwinsize()/tcsetwinsize() should be
> guarded by __POSIX_VISIBLE too?

Yes.  There are other, visibility bits missing in libc, struct winsize
needs to be moved to the specified header (also with proper guards), a
manpage needs to be written, and then there's the hard part: verify
the window size is reset on first open for all the terminal drivers.


Philip Guenther