Received: from malur.postgresql.org ([217.196.149.56])
	by arkaria.postgresql.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256)
	(Exim 4.89)
	(envelope-from <pgsql-bugs-owner+archive@lists.postgresql.org>)
	id 1i0RbL-0000Oq-Jt
	for pgsql-bugs@arkaria.postgresql.org; Wed, 21 Aug 2019 14:28:39 +0000
Received: from localhost ([127.0.0.1] helo=malur.postgresql.org)
	by malur.postgresql.org with esmtp (Exim 4.89)
	(envelope-from <pgsql-bugs-owner+archive@lists.postgresql.org>)
	id 1i0RbK-0008AD-DN
	for pgsql-bugs@arkaria.postgresql.org; Wed, 21 Aug 2019 14:28:38 +0000
Received: from makus.postgresql.org ([2001:4800:3e1:1::229])
	by malur.postgresql.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256)
	(Exim 4.89)
	(envelope-from <tgl@sss.pgh.pa.us>)
	id 1i0RbK-00082Y-1D
	for pgsql-bugs@lists.postgresql.org; Wed, 21 Aug 2019 14:28:38 +0000
Received: from sss.pgh.pa.us ([66.207.139.130])
	by makus.postgresql.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256)
	(Exim 4.92)
	(envelope-from <tgl@sss.pgh.pa.us>)
	id 1i0RbH-0001U9-Pq
	for pgsql-bugs@lists.postgresql.org; Wed, 21 Aug 2019 14:28:36 +0000
Received: from sss1.sss.pgh.pa.us (localhost [127.0.0.1])
	by sss.pgh.pa.us (8.14.4/8.14.4) with ESMTP id x7LESVT5030821;
	Wed, 21 Aug 2019 10:28:31 -0400
From: Tom Lane <tgl@sss.pgh.pa.us>
To: Alvaro Herrera <alvherre@2ndquadrant.com>
cc: Michael Paquier <michael@paquier.xyz>, Andres Freund <andres@anarazel.de>,
        Dilip Kumar <dilipbalaut@gmail.com>, jungleboogie0@gmail.com,
        pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #15964: vacuumdb.c:187:10: error: use of undeclared
 identifier 'FD_SETSIZE'
In-reply-to: <20190821141636.GA26948@alvherre.pgsql>
References: <20190821141636.GA26948@alvherre.pgsql>
Comments: In-reply-to Alvaro Herrera <alvherre@2ndquadrant.com>
	message dated "Wed, 21 Aug 2019 10:16:36 -0400"
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-ID: <30819.1566397711.1@sss.pgh.pa.us>
Date: Wed, 21 Aug 2019 10:28:31 -0400
Message-ID: <30820.1566397711@sss.pgh.pa.us>
List-Id: <pgsql-bugs.lists.postgresql.org>
List-Help: <https://lists.postgresql.org/manage/>
List-Subscribe: <https://lists.postgresql.org/manage/>
List-Post: <mailto:pgsql-bugs@lists.postgresql.org>
List-Owner: <mailto:pgsql-bugs-owner@lists.postgresql.org>
List-Archive: <https://www.postgresql.org/list/pgsql-bugs>
Precedence: bulk

Alvaro Herrera <alvherre@2ndquadrant.com> writes:
> I guess the other possibility is that there exists an operating system
> that returns file descriptors higher than its FD_SETSIZE, when some fds
> below FD_SETSIZE are still available.  Doesn't seem realistic.

I think POSIX requires open() to select the lowest unused FD.  Otherwise
tricks like closing and reopening stdout wouldn't work reliably.

			regards, tom lane