[Ffmpeg-devel] about ff_check_alignment()

[Trent Piepho]

On Sun, 11 Feb 2007, Mario Rossi wrote:
> On 2/11/07, Dominik 'Rathann' Mierzejewski <dominik at rangers.eu.org> wrote:
> > > on recent (anything after and including the pentium 1) x86
> > > -mpreferred-stack-boundary=3 is the absolute minimum
> > > on cpus with SSE* or altivec or similar SIMD instruction sets 4 is needed
> >
> > Just a thought... why not add it to default CFLAGS then?
> > Something along the lines of
> > check_cflags -mpreferred-stack-boundary=4
> > in configure.
>
> I've tried to remove ALL
>
> -mpreferred-stack-boundary=2
>
> from xine's Makefiles and the warning disappears.
>
> I've tried to remove ONLY the ones under libffmeg but it looked like
> it was not enough... (I could be wrong on this last point).

You're right, it's not enough.  They way stack alignment works, a function
must not only be compiled with the necessary mpreferred-stack-boundary, but
the function that called it must have a preferred-stack-boundary that is at
least as big, and again for the function that called that one, and so on.