DMARC-Filter: OpenDMARC Filter v1.4.2 delorie.com 53EBoWIC989449
Authentication-Results: delorie.com; dmarc=pass (p=none dis=none) header.from=cygwin.com
Authentication-Results: delorie.com; spf=pass smtp.mailfrom=cygwin.com
DKIM-Filter: OpenDKIM Filter v2.11.0 delorie.com 53EBoWIC989449
Authentication-Results: delorie.com;
	dkim=pass (1024-bit key, unprotected) header.d=cygwin.com header.i=@cygwin.com header.a=rsa-sha256 header.s=default header.b=F96eCvjv
X-Recipient: archive-cygwin AT delorie DOT com
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org DC5BE385840D
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cygwin.com;
	s=default; t=1744631430;
	bh=iT7vD3d4XtXPp+a1Glqprt/rvQcGlxKWTl0T/K7f1ls=;
	h=Date:To:Subject:In-Reply-To:References:List-Id:List-Unsubscribe:
	 List-Archive:List-Post:List-Help:List-Subscribe:From:Reply-To:Cc:
	 From;
	b=F96eCvjvsRVRpbmuFtk+VPsJEp0LNyhXb430TuonULJjrdn/P0i8qzoSdpd2awoCy
	 daBpC+Kvg7Puu4PvGIJve1x/syJ2XJvrWMAE1jCkCPn5LKkkB+Us+5WRQvFxMtedOv
	 6OEvDa0VYh6uSka7Pu7fMFVNgtLepyRiFKzArpYs=
X-Original-To: cygwin AT cygwin DOT com
Delivered-To: cygwin AT cygwin DOT com
DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org C8A683858C54
ARC-Filter: OpenARC Filter v1.0.0 sourceware.org C8A683858C54
ARC-Seal: i=1; a=rsa-sha256; d=sourceware.org; s=key; t=1744631405; cv=none;
 b=Q1PPB1iiixU9MzUseHjoUWSh65EXqFX/gS23tTzPYhXB9vYTinXrYIxO5YuvI47xIg2Hn6WUlpjvuVJkh47+GE48h1/APaD9v34Uy8H4YAWed4i7fwYestg40TUo7R5RPERQPjvrgbQv3bxrZfJvgtHQ0ejwtppjiv/OzmhmQmM=
ARC-Message-Signature: i=1; a=rsa-sha256; d=sourceware.org; s=key;
 t=1744631405; c=relaxed/simple;
 bh=W1i8BuaAELGmA/aRe09XxcARcE2iUno4fo5nu139sMM=;
 h=DKIM-Signature:Date:From:Message-ID:To:Subject:MIME-Version;
 b=td9OFIaO/IWb/q51VKDSWfvb8S5nO4gTKfgw/tPbV98So69e+RXKVyU8beWwlMQOmsq/8pPB0czH44NRXm+CvEmLWL/P3a96Z2SddubXhejpnO6imbRwzXTNG6aN7w0YahpjUlsUydFYSLTJDizl4eBLggtfCiWXe0RIt49Maao=
ARC-Authentication-Results: i=1; server2.sourceware.org
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org C8A683858C54
X-Yandex-Fwd: 1
Date: Mon, 14 Apr 2025 14:35:53 +0300
X-Mailer: The Bat! (v9.3.4) Professional
Message-ID: <178356831.20250414143553@yandex.ru>
To: Bruno Haible <bruno AT clisp DOT org>, cygwin AT cygwin DOT com
Subject: Re: /dev/null regression in Cygwin 3.6.1
In-Reply-To: <10514352.ICPdZLu4VQ@nimes>
References: <10514352 DOT ICPdZLu4VQ AT nimes>
MIME-Version: 1.0
X-BeenThere: cygwin AT cygwin DOT com
X-Mailman-Version: 2.1.30
Precedence: list
List-Id: General Cygwin discussions and problem reports <cygwin.cygwin.com>
List-Unsubscribe: <https://cygwin.com/mailman/options/cygwin>,
 <mailto:cygwin-request AT cygwin DOT com?subject=unsubscribe>
List-Archive: <https://cygwin.com/pipermail/cygwin/>
List-Post: <mailto:cygwin AT cygwin DOT com>
List-Help: <mailto:cygwin-request AT cygwin DOT com?subject=help>
List-Subscribe: <https://cygwin.com/mailman/listinfo/cygwin>,
 <mailto:cygwin-request AT cygwin DOT com?subject=subscribe>
From: Andrey Repin via Cygwin <cygwin AT cygwin DOT com>
Reply-To: cygwin AT cygwin DOT com
Cc: Andrey Repin <anrdaemon AT yandex DOT ru>
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Errors-To: cygwin-bounces~archive-cygwin=delorie DOT com AT cygwin DOT com
Sender: "Cygwin" <cygwin-bounces~archive-cygwin=delorie DOT com AT cygwin DOT com>

Greetings, Bruno Haible!

> In Gnulib, we have a unit test that compiles the program below as a
> native Windows program (either with mingw or with MSVC), that exercises
> the Gnulib select() function
>  
> <https://git.savannah.gnu.org/gitweb/?p=gnulib.git;a=blob;f=lib/select.c;h=5a58d6ee47f5b10413d97cb7a1996d424eefc796;hb=HEAD>

> Then it does (in a Cygwin shell):

>   rm -f t-select-in.tmp
>   ./test-select-fd.exe r 0 t-select-in.tmp < /dev/null
>   cat t-select-in.tmp

> Up to Cygwin 3.6.0, the contents of the file t-select-in.tmp was "1",
> like on most other OSes, indicating that the program can read() from
> file descriptor 0.

But "< /dev/null" literally means "don't read from STDIN".
As far as I recall (correct me if I'm wrong), READING from /dev/null is
undefined and may result in undetermined behavior.

> In Cygwin 3.6.1, the contents of the file t-select-in.tmp is "0",
> indicating that read()ing from file descriptor 0 would block.
> This is a regression.

What I've gathered is that in most cases reading from /dev/null should
immediately return EOF.


-- 
With best regards,
Andrey Repin
Monday, April 14, 2025 14:31:08

Sorry for my terrible english...


-- 
Problem reports:      https://cygwin.com/problems.html
FAQ:                  https://cygwin.com/faq/
Documentation:        https://cygwin.com/docs.html
Unsubscribe info:     https://cygwin.com/ml/#unsubscribe-simple