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 1QcTKr-00044J-PZ for garchives@archives.gentoo.org; Fri, 01 Jul 2011 02:20:01 +0000 Received: from pigeon.gentoo.org (localhost [127.0.0.1]) by pigeon.gentoo.org (Postfix) with SMTP id 636D11C010; Fri, 1 Jul 2011 02:18:27 +0000 (UTC) Received: from lo.gmane.org (lo.gmane.org [80.91.229.12]) by pigeon.gentoo.org (Postfix) with ESMTP id 03DA51C010 for ; Fri, 1 Jul 2011 02:18:26 +0000 (UTC) Received: from list by lo.gmane.org with local (Exim 4.69) (envelope-from ) id 1QcTJK-0002kc-12 for gentoo-amd64@lists.gentoo.org; Fri, 01 Jul 2011 04:18:26 +0200 Received: from ip68-231-22-224.ph.ph.cox.net ([68.231.22.224]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Fri, 01 Jul 2011 04:18:26 +0200 Received: from 1i5t5.duncan by ip68-231-22-224.ph.ph.cox.net with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Fri, 01 Jul 2011 04:18:26 +0200 X-Injected-Via-Gmane: http://gmane.org/ To: gentoo-amd64@lists.gentoo.org From: Duncan <1i5t5.duncan@cox.net> Subject: [gentoo-amd64] Re: GCC-4.5.2 Has Serious Problems Date: Fri, 1 Jul 2011 02:18:15 +0000 (UTC) Message-ID: References: <20110630174530.9bcbcd47.frank.peters@comcast.net> <20110630210429.fbcd8904.frank.peters@comcast.net> Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-Id: Gentoo Linux mail X-BeenThere: gentoo-amd64@lists.gentoo.org Reply-to: gentoo-amd64@lists.gentoo.org Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 X-Complaints-To: usenet@dough.gmane.org X-Gmane-NNTP-Posting-Host: ip68-231-22-224.ph.ph.cox.net User-Agent: Pan/0.135 (Tomorrow I'll Wake Up and Scald Myself with Tea; GIT 275cfc3 branch-testing) Content-Transfer-Encoding: quoted-printable X-Archives-Salt: X-Archives-Hash: e9a993f498e61a4c0353d96190bad70b Frank Peters posted on Thu, 30 Jun 2011 21:04:29 -0400 as excerpted: > On Fri, 01 Jul 2011 02:44:36 +0300 Nikos Chantziaras > wrote: >=20 >> And here you can read more thorough information about strict aliasing: >>=20 >> http://labs.qt.nokia.com/2011/06/10/type-punning-and-strict-aliasin= g >>=20 > You've saved the day in more ways than one. >=20 > A few days ago I posted about a possible problem with a floating point > test called the UCBTEST. After examining the source code of this test, > I see violations of aliasing rules throughout. It's hard to efficiently > manipulate variables without them. >=20 > Of course, this code was written before the C99 standard and so is > exempt. But the use of "-fno-strict-aliasing" will apply with the > UCBTEST as well. Truthfully, I thought sure this was a direct follow-on to that! So I'm=20 happy to see that the same cause and solutions apply. =3D:^) As I said in an earlier post, tho, expect there to be more problems like=20 that with code of that age as time goes on, because they're well past the= =20 easy optimizations now, and into stuff like this. So it may be wise to=20 keep an eye out and test the minor gcc version bumps with an eye toward=20 such issues. They generally put out a porting guide, etc, with the new=20 version, that you can read for clues in case the tests start doing=20 unexpected things again. =20 (If you pay attention to flameeyes' blog, he tends to cover such things=20 reasonably early on after release of a new gcc version as well, as he=20 does tinderbox runs to see how bad the interaction of the new version is=20 with the current gentoo ~arch tree as a whole and eventually to test that= =20 the latest ~arch packages are updated or patched to fix the problem,=20 before that gcc version gets unmasked to ~arch. By no means do I agree=20 with everything he says, but he really is an asset to gentoo and would be= =20 sorely missed should one of his sick episodes make it impossible for him=20 to continue, or if he simply decided he had better things to do with his=20 time. The switch to --as-needed in Gentoo's default ldflags was largely=20 due to his work, explaining the issues for other devs, testing and filing= =20 bugs, helping with the hard cases, and in general pushing it until it=20 happened, for instance, and every single gentoo user benefits from that=20 in the form of less mandatory rebuilds, every time they update. It may=20 well have happened without him, but it might have taken a decade longer,=20 too. And because gentoo devs normally push those patches upstream where=20 they can, that has been a benefit to the entire FLOSS community, not just= =20 gentoo, as well, reducing "dependency hell" for everyone.) --=20 Duncan - List replies preferred. No HTML msgs. "Every nonfree program has a lord, a master -- and if you use the program, he is your master." Richard Stallman