glibc 2.21 - Machine maintainers, please test your machines.

[Torvald Riegel]

On Mon, 2015-01-26 at 04:44 -0800, H.J. Lu wrote:
> On Mon, Jan 26, 2015 at 1:24 AM, Andreas Schwab <schwab@suse.de> wrote:
> > "H.J. Lu" <hjl.tools@gmail.com> writes:
> >
> >> It doesn't change the size, only increases alignment from 4 bytes to 8 bytes.
> >
> > Alignment is part of the ABI.
> >
> 
> For x32, we can increase alignment from 4 bytes to 8 bytes without breaking
> existing binaries.

But you'd still have to do the alignment check at runtime, because you
can't expect the application to have used the new headers with proper
alignment.  Or are you saying that the alignment is just a performance
thing in the particular case of x32, because the atomics work either
way?  If so, then using __alignof__(sem_t) in Chris' patch would be good
because then to_new_sem would resolve to a noop in x32 with your
alignment change applied.