From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED.blaine.gmane.org!not-for-mail From: Matthew Leach Newsgroups: gmane.emacs.bugs Subject: bug#37564: [PATCH] don't export LINES and COLUMNS env vars in term to fix ncurses applications Date: Tue, 01 Oct 2019 20:24:14 +0100 Message-ID: <87o8z0few1.fsf@mattleach.net> References: <87y2y5lfnb.fsf@1e0.co.uk> <83eezxatsv.fsf@gnu.org> <87tv8slb6w.fsf@mattleach.net> <83a7aka1q5.fsf@gnu.org> <87sgocfh8c.fsf@mattleach.net> <83y2y48f8u.fsf@gnu.org> Mime-Version: 1.0 Content-Type: text/plain Injection-Info: blaine.gmane.org; posting-host="blaine.gmane.org:195.159.176.226"; logging-data="7665"; mail-complaints-to="usenet@blaine.gmane.org" User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.3 (gnu/linux) Cc: 37564@debbugs.gnu.org To: Eli Zaretskii Original-X-From: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane.org@gnu.org Tue Oct 01 21:28:46 2019 Return-path: Envelope-to: geb-bug-gnu-emacs@m.gmane.org Original-Received: from lists.gnu.org ([209.51.188.17]) by blaine.gmane.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1iFNpG-0001q1-09 for geb-bug-gnu-emacs@m.gmane.org; Tue, 01 Oct 2019 21:28:46 +0200 Original-Received: from localhost ([::1]:47040 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iFNpE-0005ab-DI for geb-bug-gnu-emacs@m.gmane.org; Tue, 01 Oct 2019 15:28:44 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:47884) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iFNlg-0002wH-IO for bug-gnu-emacs@gnu.org; Tue, 01 Oct 2019 15:25:05 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1iFNle-00008i-C2 for bug-gnu-emacs@gnu.org; Tue, 01 Oct 2019 15:25:03 -0400 Original-Received: from debbugs.gnu.org ([209.51.188.43]:54228) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1iFNle-00008V-0K for bug-gnu-emacs@gnu.org; Tue, 01 Oct 2019 15:25:02 -0400 Original-Received: from Debian-debbugs by debbugs.gnu.org with local (Exim 4.84_2) (envelope-from ) id 1iFNld-0005mS-RU for bug-gnu-emacs@gnu.org; Tue, 01 Oct 2019 15:25:01 -0400 X-Loop: help-debbugs@gnu.org Resent-From: Matthew Leach Original-Sender: "Debbugs-submit" Resent-CC: bug-gnu-emacs@gnu.org Resent-Date: Tue, 01 Oct 2019 19:25:01 +0000 Resent-Message-ID: Resent-Sender: help-debbugs@gnu.org X-GNU-PR-Message: followup 37564 X-GNU-PR-Package: emacs X-GNU-PR-Keywords: patch Original-Received: via spool by 37564-submit@debbugs.gnu.org id=B37564.156995785722163 (code B ref 37564); Tue, 01 Oct 2019 19:25:01 +0000 Original-Received: (at 37564) by debbugs.gnu.org; 1 Oct 2019 19:24:17 +0000 Original-Received: from localhost ([127.0.0.1]:34816 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1iFNku-0005lP-Gr for submit@debbugs.gnu.org; Tue, 01 Oct 2019 15:24:16 -0400 Original-Received: from mx0.mattleach.net ([176.58.118.143]:53080) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1iFNkr-0005lD-KF for 37564@debbugs.gnu.org; Tue, 01 Oct 2019 15:24:15 -0400 Original-Received: by mx0.mattleach.net (Postfix, from userid 99) id 91D9961C91; Tue, 1 Oct 2019 20:24:12 +0100 (BST) Original-Received: from hopton.mattleach.net (92.40.249.172.threembb.co.uk [92.40.249.172]) by mx0.mattleach.net (Postfix) with ESMTPSA id A292461C21; Tue, 1 Oct 2019 20:24:11 +0100 (BST) In-Reply-To: <83y2y48f8u.fsf@gnu.org> (Eli Zaretskii's message of "Tue, 01 Oct 2019 21:58:25 +0300") X-BeenThere: debbugs-submit@debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.51.188.43 X-BeenThere: bug-gnu-emacs@gnu.org List-Id: "Bug reports for GNU Emacs, the Swiss army knife of text editors" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane.org@gnu.org Original-Sender: "bug-gnu-emacs" Xref: news.gmane.org gmane.emacs.bugs:168077 Archived-At: Eli Zaretskii writes: >> From: Matthew Leach >> Cc: 37564@debbugs.gnu.org >> Date: Tue, 01 Oct 2019 19:33:39 +0100 >> >> >> I'm curious as to which programs you are referring? AFAIK, if a program >> >> tries to read the LINES and COLUMNS environment variables, using >> >> `getenv()', they don't exist. >> > >> > What makes you say that? >> >> If I run the C program in my previous post in an xterm and resize I get: >> >> getenv: (null) (null) >> ioctl: 24 80 >> getenv: (null) (null) >> ioctl: 42 169 >> >> You can see that doing getenv() on LINES and COLUMNS returns a null >> pointer. I've tested this same behaviour on gnome-terminal and numerous >> other terminal emulators. > > I simply tried "env | fgrep LINES" and I do see the variable, although > it wasn't there before I launched Emacs. I would expect the variable to be there when inside Emacs as it has exported it. You should find that it won't exist if ran outside Emacs, for example in xterm. > 'env' is just another program accessing the environment, right? I have > no idea why your test program doesn't see that, but then I'm far from > being an expert on these issues. Indeed, it does see the variables if I run inside Emacs. If I run it outside then they are not there, on my machine anyway. >> > Emacs exports these variables into the environment that is passed to >> > child subprocesses, so those subprocesses will definitely see them >> > using getenv. >> >> I'm no expert on how these things work but it doesn't appear to be the >> way that it's done, on my machine anyway. Perhaps there are programs >> that uses these variables on MacOS or Windows? > > I tried the above on a Trisquel GNU/Windows machine, FWIW. I'm running on Arch GNU/Linux this end. >> I'm testing this on the latest Emacs Git version. I can see that >> window-adjust-process-window-size-function is used in term.el however, >> this doesn't appear to update the environment variables exported to the >> terminal process. > > AFAIR, it's supposed to send the corresponding ioctl command, in > addition to setting LINES and COLUMNS. > >> If I run the same program with term on Emacs git and >> resize I get: >> >> getenv: 31 80 >> ioctl: 30 89 >> getenv: 31 80 >> ioctl: 30 90 >> getenv: 31 80 >> ioctl: 30 91 >> getenv: 31 80 >> ioctl: 31 92 >> getenv: 31 80 >> ioctl: 31 93 >> getenv: 31 80 >> ioctl: 31 94 >> ... >> >> Notice that the values returned by getenv don't change. > > Again, the "env | fgrep LINES" method does show the change when I > resize the window on the machine I tried this, so I'm unsure why you > don't see it. Ah, indeed if I try and resize and print the variable it has updated: matthew@hopton ~ $ env | grep -i lines LINES=30 matthew@hopton ~ $ env | grep -i lines LINES=12 I think the issue is that the environment can't be while a process is running; the environment variables are fixed when the program has started. For a ncurses application this presents a problem as LINES and COLUMNS can't be updated when the window size is changed and the program handles a SIGWINCH. You can see that on the output above. >> Given that this functionality is broken, I'm suggesting that we don't >> export the variables. > > I don't agree that it's broken; it isn't for me. I think someone who > understands more than I do about this stuff should chime in and > explain why we see such different results. I think the above explains what's going on. Perhaps that's why terminal emulators don't export LINES and COLUMNS to programs so an ioctl() is used instead? -- Matt