Date: Thu, 5 Jul 2012 00:32:01 +0900 From: Taku YAMAMOTO <taku@tackymt.homeip.net> To: Dimitry Andric <dim@FreeBSD.org> Cc: freebsd-current@freebsd.org Subject: Re: FYI: SIGBUS with world built by clang Message-ID: <20120705003201.bb297e8a.taku@tackymt.homeip.net> In-Reply-To: <4FF45C6E.1080000@FreeBSD.org> References: <20120704233316.70ec8654.taku@tackymt.homeip.net> <4FF45C6E.1080000@FreeBSD.org>
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On Wed, 04 Jul 2012 17:08:30 +0200
Dimitry Andric <dim@FreeBSD.org> wrote:
> On 2012-07-04 16:33, Taku YAMAMOTO wrote:
> > For people having SIGBUS with clang-build world + gcc-build binaries,
> >
> >
> > In short words, for any libraries (and never forget about rtld-elf!)
> > which are potentially called from arbitrary binaries,
> > compile them with either -mstackrealign or -mstack-alignment=8!
> >
> > The detail is as follows.
> >
> > I've observed that clang carelessly expects the stack being aligned at
> > 16 byte boundary.
>
> Eh, this is a requirement of the amd64 ABI. Any compiler that *doesn't*
> align the stack on 16-byte boundaries is basically broken. Or are you
> experiencing this on i386? Even there, 16-byte alignment would be much
> better in combination with SSE instructions (which arent' enabled by
> default, btw).
Oops, I had to be clear about that!
Yes, the experiment was took on i386 (actually -march=pentium4).
> Note that you would get the same issue with newer versions of gcc, which
> will also assume this alignment.
Interesting, but the base gcc we currently have won't on i386, I think.
(I occationally get bitten by similar problem when using -ftree-vectorize)
--
-|-__ YAMAMOTO, Taku
| __ < <taku@tackymt.homeip.net>
- A chicken is an egg's way of producing more eggs. -
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