From owner-freebsd-hackers Thu Oct 10 12:39:59 2002 Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id EDFAE37B401; Thu, 10 Oct 2002 12:39:57 -0700 (PDT) Received: from conure.mail.pas.earthlink.net (conure.mail.pas.earthlink.net [207.217.120.54]) by mx1.FreeBSD.org (Postfix) with ESMTP id 7DA6D43E9E; Thu, 10 Oct 2002 12:39:57 -0700 (PDT) (envelope-from tlambert2@mindspring.com) Received: from pool0397.cvx21-bradley.dialup.earthlink.net ([209.179.193.142] helo=mindspring.com) by conure.mail.pas.earthlink.net with esmtp (Exim 3.33 #1) id 17zjA0-00067e-00; Thu, 10 Oct 2002 12:39:53 -0700 Message-ID: <3DA5D741.FB59AE1B@mindspring.com> Date: Thu, 10 Oct 2002 12:38:41 -0700 From: Terry Lambert X-Mailer: Mozilla 4.79 [en] (Win98; U) X-Accept-Language: en MIME-Version: 1.0 To: Bruce Evans Cc: Craig Rodrigues , freebsd-standards@FreeBSD.ORG, freebsd-hackers@FreeBSD.ORG Subject: Re: Problem detecting POSIX symbolic constants References: <20021010213351.X8598-100000@gamplex.bde.org> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG Bruce Evans wrote: > _POSIX_REALTIME_SIGNALS is defined to 0: > This means that the interface may work, and that it exists in headers and > libraries, so applications may reference it in normal ways. It may fail > at runtime; applications must use sysconf() to determine if it is actually Alternately, they can say "Screw you, OS designer!" and use it as if it were "-1", so that they don't have to add all sorts of runtime garbage to their programs, with multiple alternate code paths, etc.. Makes for much more readable code. > _POSIX_REALTIME_SIGNALS is undefined: > Apparently the same as when it is defined to 0, except you cannot assume > that anything related to it works until you call sysconf(), so you must > not reference its interfaces statically, and must use a dll or something > that references it. The dll is presumably available on systems that > support it but not (except possibly a dummy version) on systems that > don't support it. > > I think the case where the symbol is undefined should never be implemented > in practice. It can be reduced to the case where the symbol is 0 using > dynamic linkage with the complications for linkage not visible to the > application. I think you will have to go back in time, for this to happen. As things stand today, there are systems where it's undefined that were implemented before the symbol was a twinkle in some feature-test weenie on the POSIX committee's eye. -- Terry To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message