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

[Lennart Sorensen]

On Tue, Nov 01, 2016 at 07:37:33PM +0200, Adrian Bunk wrote:
> On Tue, Nov 01, 2016 at 01:08:03PM -0400, Lennart Sorensen wrote:
> > On Tue, Nov 01, 2016 at 12:22:19PM -0400, Lennart Sorensen wrote:
> > > On Tue, Nov 01, 2016 at 04:34:01PM +0200, Adrian Bunk wrote:
> > > > This doesn't looks wrong to me.
> > > > 
> > > > Note that depending on the software --enable-altivec can either mean
> > > > - compile unconditionally for AltiVec, or
> > > > - enable AltiVec parts with autodetection to only use them when the
> > > >   hardware supports it
> > > 
> > > Well in VLC it means build with -maltivec among other things.
> > > 
> > > > As I already wrote, vlc contains AltiVec-specific code and autodetection 
> > > > for using it only when the hardware supports it.
> > > > 
> > > > This should be enabled on all ppc ports, except the SPE one.
> > > > 
> > > > --enable-altivec also adding -maltivec elsewhere is a bug.
> > > 
> > > Well it certainly appears to have been done on purpose in the configure
> > > script.  Maybe it is a bug.  Perhaps I should poke it a bit...
> > > 
> > > > And due to this bug the whole AltiVec autodetection in vlc is
> > > > pretty useless.
> > > 
> > > Well if it has such auto detection, then yes it is.
> > 
> > I currently suspect:
> > 
> > configure.ac:
> > ...
> >   ])
> >   VLC_RESTORE_FLAGS
> >   AS_IF([test "${ac_cv_c_altivec}" != "no"], [
> >     CPPFLAGS="${CPPFLAGS} ${ac_cv_c_altivec}"  <-- this looks wrong
> >     AC_DEFINE(CAN_COMPILE_C_ALTIVEC, 1, [Define to 1 if C AltiVec extensions are available.])
> >     VLC_ADD_CFLAGS([libvlccore],[${ac_cv_c_altivec}])
> >     ALTIVEC_CFLAGS="$ALTIVEC_FLAGS ${ac_cv_c_altivec} ${ac_cv_c_altivec_abi}"
> > ...
> > 
> > I think that line should not be there since all over CPPFLAGS is used as
> > part of the COMPILE variable, meaning not just CFLAGS gets -maltivec when
> > needed through ALTIVEC_CFLAGS, but in fact everywhere that has CPPFLAGS
> > gets it, meaning everything.
> 
> I was more suspecting the VLC_ADD_CFLAGS() would be the problem,
> but since the build log says "-maltivec -maltivec" it is actually
> likely that this is wrong in more than one place.

Well that looks like it only adds it for libvlccore.

-- 
Len Sorensen