From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from pigeon.gentoo.org ([208.92.234.80] helo=lists.gentoo.org) by finch.gentoo.org with esmtp (Exim 4.60) (envelope-from ) id 1P92PF-0008Jc-9A for garchives@archives.gentoo.org; Thu, 21 Oct 2010 21:10:41 +0000 Received: from pigeon.gentoo.org (localhost [127.0.0.1]) by pigeon.gentoo.org (Postfix) with SMTP id EA45CE08DD for ; Thu, 21 Oct 2010 21:10:36 +0000 (UTC) Received: from mail-ew0-f53.google.com (mail-ew0-f53.google.com [209.85.215.53]) by pigeon.gentoo.org (Postfix) with ESMTP id 6D96CE07CC for ; Thu, 21 Oct 2010 21:07:20 +0000 (UTC) Received: by ewy10 with SMTP id 10so119271ewy.40 for ; Thu, 21 Oct 2010 14:07:19 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:received:from:to:subject:date :user-agent:cc:references:in-reply-to:mime-version:content-type :content-transfer-encoding:message-id; bh=00W008efYwyy7zMYVLScda8xzyXtDGNJunYyX9y5Tzs=; b=S3VbStwafe+VTFQSovzIfCxYTiacSSwCaJY0BRm1FGRcaMW0uYX6O+c+uInO1lPnnl 6iJ/qIADgNtF0GPncPcuwP11dreyDAa3AxJZan3aCS9Vb40v4oscL/KY3OL/mjTqArYi Ig/gwqNfiV228r1mwWLxUpllkqKaRDBG2t12Y= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=from:to:subject:date:user-agent:cc:references:in-reply-to :mime-version:content-type:content-transfer-encoding:message-id; b=YZ8kL84Eo3pllWhWNq80qOXnZylC3IOaPA5ZOVZXsPYxQ4kaIGxOp5GtUKIFmQtESv +++TBWdz0PlV+3WTpoJu3Aqv9A1pBzIeJWwJmUF24+brc64qOKTknWLTbcq50h/H9LxS HujZKiE49JiAjOrp9J9TrQ4KykdRuh0W1SXac= Received: by 10.14.119.7 with SMTP id m7mr1324529eeh.40.1287695239825; Thu, 21 Oct 2010 14:07:19 -0700 (PDT) Received: from nazgul.localnet (196-215-2-42.dynamic.isadsl.co.za [196.215.2.42]) by mx.google.com with ESMTPS id x54sm2282047eeh.17.2010.10.21.14.07.16 (version=TLSv1/SSLv3 cipher=RC4-MD5); Thu, 21 Oct 2010 14:07:17 -0700 (PDT) From: Alan McKinnon To: gentoo-user@lists.gentoo.org Subject: Re: [gentoo-user] gcc upgrade - rebuild everything? Date: Thu, 21 Oct 2010 23:07:50 +0200 User-Agent: KMail/1.13.5 (Linux/2.6.35-ck-r4; KDE/4.5.2; x86_64; ; ) Cc: Grant References: In-Reply-To: Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-Id: Gentoo Linux mail X-BeenThere: gentoo-user@lists.gentoo.org Reply-to: gentoo-user@lists.gentoo.org MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <201010212307.50617.alan.mckinnon@gmail.com> X-Archives-Salt: aa14fbd7-c203-4595-ad18-757943ce7f53 X-Archives-Hash: b4149943cc66a56c082965da1711bee6 Apparently, though unproven, at 21:58 on Thursday 21 October 2010, Grant did opine thusly: > I just upgraded from gcc-4.4.3-r2 to gcc-4.4.4-r2 and I'm wondering if > I really need to rebuild everything as it says in the guide: > > http://www.gentoo.org/doc/en/gcc-upgrading.xml No, you do not need to do this. The document is over-reaching (see below) I ran a mixture of 4.4.3 and 4.4.4 for ages, completely trouble-free. > If not, when is it necessary? When you have an ABI change in the code generated by the compiler. In other words, when code generated by this version is incompatible with code generated by that version, and you have both on the same system. This has not happened for a long time in gcc-land. Now, about that official doc. Your question comes up with unbelievable regularity and every time the poster references that doc. But it is not necessary to do what the doc says, and a long time ago I think I figured it out. The author's intention is less to give you the absolute complete total 100% truth that will always work out just fine, and more to reduce the amount of clutter in his inbox or on b.g.o. The rules about how to detect when a rebuild of world is needed are complex and most readers simply will not understand them - they don't understand compiler internals (how many people DO?). But if you tell people to just rebuild world every time, and weird funny lurking problems are likely to just get fixed as a side effect, no real harm is done. Does it hurt the author? No. Does it reduce the amount of bugs he has to deal with on the rare occasion it is needed? Yes. What does the user lose? Nothing much, more cpu cycles get used, more bits flip on a disk, your video card gets a work out scrolling all that text. Will you waste time? Yes. Will you break stuff? No. So rebuild world if it makes you feel better. But you don't need to this time. The authors of gcc will certainly notify the entire world and it's dogs when you do need to. -- alan dot mckinnon at gmail dot com