Date: Sat, 13 Sep 2014 20:30:12 +0200 From: Dimitry Andric <dim@FreeBSD.org> To: Andrey Chernov <ache@freebsd.org> Cc: toolchain@freebsd.org Subject: Re: clang makes segfaulting code with -march=core2 on i386 Message-ID: <CC121A4D-A6D0-430B-B15F-BFB48C5FB6E6@FreeBSD.org> In-Reply-To: <5414865A.6030101@freebsd.org> References: <54130AD0.8090103@freebsd.org> <A212D7AF-4DA7-4043-BB73-1746A5C2F42F@FreeBSD.org> <54133E1E.9030105@freebsd.org> <54135B24.5040905@freebsd.org> <54135D0B.7060701@freebsd.org> <6FDF432B-8245-4BC7-952B-DFFEEA106D6F@FreeBSD.org> <5414865A.6030101@freebsd.org>
next in thread | previous in thread | raw e-mail | index | archive | help
--Apple-Mail=_FD0B8BBC-223F-4B45-8F17-6B995FBDE8C9 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=koi8-r On 13 Sep 2014, at 20:00, Andrey Chernov <ache@freebsd.org> wrote: > On 13.09.2014 20:45, Dimitry Andric wrote: >> After some massaging of gcc's source to disable its built-in segfault >> handlers, I get this backtrace: > > Do you get this with my core or finally able to reproduce it by yourself? I was able to reproduce it, on stable/10. I could not reproduce it on head, but that is how it sometimes goes with this kind of issue. :) >> I think it's most likely this is some type of undefined behavior in gcc, >> which leads to randomly corrupted tree values. Of course, it could also >> be a clang bug, but I don't see any "64-bit" instructions in there at >> all. >> >> This needs to be investigated further, but it's very hard to understand >> what is going on the guts of gcc's parser. Let alone to reduce this to >> some sort of reproducible test case. > > By first glance I see a lots of <optimized out> things. It is known that > in edge cases gcc preserves more "unused" values than clang. It can be > the possible case. I'll try to lower -O level preserving -march=core2 > and see. It seems to work for me with -O1 -march=core2, and while valgrind does complain a little, the warnings are all benign. I'll see if I can "mix and match" a few -O2 and -O1 compiled objects, to zero in on where the problematic area(s) are. -Dimitry --Apple-Mail=_FD0B8BBC-223F-4B45-8F17-6B995FBDE8C9 Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename=signature.asc Content-Type: application/pgp-signature; name=signature.asc Content-Description: Message signed with OpenPGP using GPGMail -----BEGIN PGP SIGNATURE----- Version: GnuPG/MacGPG2 v2.0.22 (Darwin) iEYEARECAAYFAlQUjUgACgkQsF6jCi4glqMLcQCePX11qOw/Gh+jUTUzCw4iV0DK URYAoJKWrTC0w3eXhnxzLsJgvdg7s9os =IAJV -----END PGP SIGNATURE----- --Apple-Mail=_FD0B8BBC-223F-4B45-8F17-6B995FBDE8C9--
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?CC121A4D-A6D0-430B-B15F-BFB48C5FB6E6>