On Thu, May 19, 2011 at 14:54:28 +1000, Peter Hutterer wrote: > X.Org Bug 36986 <http://bugs.freedesktop.org/show_bug.cgi?id=36986> > > Signed-off-by: Peter Hutterer <[email protected]> > --- > > On Wed, May 18, 2011 at 12:45:05AM -0700, Keith Packard wrote: > > On Wed, 18 May 2011 13:30:44 +1000, Peter Hutterer > > <[email protected]> wrote: > > > > > + const int sz_dbl = sizeof(double); > > > /* force alignment with double */ > > > - union align_u { ValuatorClassRec valc; double d; } *align; > > > + union align_u { > > > + ValuatorClassRec valc; > > > + double d[(sizeof(ValuatorClassRec) + sz_dbl - 1)/sz_dbl]; > > > + } *align; > > > > This doesn't make sense to me. The requirement for the union is that you > > be able to allocate an array of them and store into each element: > > > > union align_u foo[12]; > > > > foo[0].d = 0.0; > > foo[1].d = 1.0; > > > > This should require double alignment for the entire union, even though > > 'd' is far smaller than 'valc'. > > > > Of course, on a 32-bit x86 machine, doubles can be stored without > > penalty on 4-byte boundaries, so the union is only aligned to 52 bytes. > > > > Can you explain why this alignment isn't acceptable in this context? > > because I naïvely thought that we needed double alignment on 32 bit too and > the test was written that way. Oh well, how about this patch instead then. > it just disables the alignment check on 32 bit. > Maybe check for __alignof__(double) instead of sizeof(double)?
Cheers, Julien _______________________________________________ [email protected]: X.Org development Archives: http://lists.x.org/archives/xorg-devel Info: http://lists.x.org/mailman/listinfo/xorg-devel
