Bug#842513: vlc: immediate crash on launch on powerpc

[Lennart Sorensen]

On Mon, Oct 31, 2016 at 11:13:00PM +0200, Adrian Bunk wrote:
> This actually looks like a bug in upstream configure.ac to me:
>     VLC_ADD_CFLAGS([libvlccore],[${ac_cv_c_altivec}])
>     ALTIVEC_CFLAGS="$ALTIVEC_FLAGS ${ac_cv_c_altivec} ${ac_cv_c_altivec_abi}"
>     VLC_ADD_CFLAGS([deinterlace],[${ac_cv_c_altivec} ${ac_cv_c_altivec_abi}])
> 
> It is correct that this adds -maltivec to AltiVec-specific code,
> and vlc has proper autodetection to run this only when AltiVec
> is actually present.
> 
> The VLC_ADD_CFLAGS here look just wrong - it is not the job of 
> configure.ac to add such flags to generic code (whatever march
> and hardware features are present is defined through compiler
> defaults and the CFLAGS passed by the user).

Actually what looks really wrong is that debian/rules builds ffmpeg with
--disable-altivec and then builds vlc with --enable-altivec.

Since powerpc can't assume you have altivec, perhaps vlc shouldn't be
built with it, or at least ought to have justification for why it is
done that way.  Maybe it was thought that no CPU without altivec would
be powerful enough to bother using vlc, but I think that may not in fact
be a valid assumption these days.

Certainly a 2.5GHz e5500 core is pretty decent performance, but has
no altivec.

-- 
Len Sorensen