[FFmpeg-devel] [PATCH] fix h264_deblock_sse2.asm segfaults on clang/x86-32

[Reimar Döffinger]

On Wed, Sep 01, 2010 at 02:01:36AM -0400, Ronald S. Bultje wrote:
> Hi,
> 
> On Wed, Sep 1, 2010 at 1:53 AM, Reimar D?ffinger
> <Reimar.Doeffinger at gmx.de> wrote:
> > On Tue, Aug 31, 2010 at 07:06:09PM -0400, Ronald S. Bultje wrote:
> >> on fate/clang/freebsd/x86-32 [1], all h264 tests fail with a sigbus.
> >> There's some alignment issues in the sse2 asm. The asm appears to
> >> assume that the caller function guarantees a certain alignment, which
> >> is (IMO) not necessarily true. If the function is called directly from
> >> C, stack can have any alignment, depending on the compiler used, so
> >> the functions shouldn't assume any specific alignment imo.
> >
> > We already use
> > attribute_align_arg
> 
> Alex brought that up also. That sets alignment of stack in functions,
> not functions called by functions (afaics). Since these are compiled
> by yasm, they're unaffected by that.
> 
> Or clang is buggy, who knows... :-).

No it's not, I just considered it reasonable to assume that any
non-ancient compiler wouldn't needlessly clobber stack alignment.