From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lists.gentoo.org ([140.105.134.102] helo=robin.gentoo.org) by nuthatch.gentoo.org with esmtp (Exim 4.60) (envelope-from ) id 1GTnaC-0003X4-Db for garchives@archives.gentoo.org; Sat, 30 Sep 2006 22:45:20 +0000 Received: from robin.gentoo.org (localhost [127.0.0.1]) by robin.gentoo.org (8.13.8/8.13.6) with SMTP id k8UMiUE5008590; Sat, 30 Sep 2006 22:44:30 GMT Received: from mail.bouton.name (ns.bouton.name [70.85.16.101]) by robin.gentoo.org (8.13.8/8.13.6) with ESMTP id k8UMgatf007435 for ; Sat, 30 Sep 2006 22:42:36 GMT Received: from [192.168.55.3] (adsl.bouton.name [82.227.97.166]) by mail.bouton.name (Postfix) with ESMTP id 3CB24BA63 for ; Sun, 1 Oct 2006 00:42:35 +0200 (CEST) Message-ID: <451EF2DA.1010301@bouton.name> Date: Sun, 01 Oct 2006 00:42:34 +0200 From: Lionel Bouton User-Agent: Thunderbird 1.5.0.5 (X11/20060920) Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-Id: Gentoo Linux mail X-BeenThere: gentoo-dev@gentoo.org Reply-to: gentoo-dev@lists.gentoo.org MIME-Version: 1.0 To: gentoo-dev@lists.gentoo.org Subject: Re: [gentoo-dev] [RFC] CFLAGS paragraph for the GWN References: <451ED52E.5030407@bouton.name> <200609301748.08239.vapier@gentoo.org> In-Reply-To: <200609301748.08239.vapier@gentoo.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Archives-Salt: 2d005c7d-f889-4cdb-ab5b-75cada50c433 X-Archives-Hash: 5e8ed3ab3885b4b49b5dab30d93625ee Mike Frysinger wrote the following on 30.09.2006 23:48 : > [...] > `man gcc` always seemed fine to me > > in fact, lets read the -ffast-math section: > -ffast-math > This option should never be turned on by any -O option since it can > result in incorrect output for programs which depend on an exact > implementation of IEEE or ISO rules/specifications for math func- > tions. > > this flag is never safe to use in CFLAGS > > Indeed, I'll add a reminder to adventurous users to check `man gcc` (I believe I added fast-math following an example somewhere on the web instead of checking the man page). >> link='http://gentoo-wiki.com/CFLAGS_matrix' >> > > no way will our documentation link to gentoo-wiki.com > > The GWN paragraph is mainly a 'heads-up' kind of thing, no more. Don't confuse the GuideXML extract with an official documentation extract, GWN uses GuideXML too :-) >> If possible, I'd like to expand the list of 3.4.6 -> 4.1.1 upgrade >> problems which are linked to experimental CFLAGS >> > > i find maintaining a list of "safe" CFLAGS on a per-gcc basis to be a waste of > time ... but that's just me > That's not the idea. The main idea is to remind people that playing with CFLAGS is allowed, as long as you remember to revert to safe CFLAGS before reporting bugs. As I wasted one dev time by forgetting to check my CFLAGS, I merely thought that maybe this wasn't a common reflex for other users too (fast-math was the only unsafe flag I used, I'm pretty conservative and simply was mistaken because roughly 2 years ago I didn't check the proper source of information: the man page). Maybe very few bug reports are caused by inadequate CFLAGS. If my problem is an uncommon exception I won't press the matter further, there would be no point to do so. I'll wait and see if other devs are aware of common CFLAGS gotchas plaguing bugzilla. Lionel. -- gentoo-dev@gentoo.org mailing list