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

[Lennart Sorensen]

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 will try compile testing that as soon as I have the system ready.

-- 
Len Sorensen