Re: glibc 2.21 - Machine maintainers, please test your machines.

["H.J. Lu" <hjl dot tools at gmail dot com>]

On Mon, Jan 26, 2015 at 4:50 AM, Torvald Riegel <triegel@redhat.com> wrote:
> 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

Yes.

> 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.

I don't want a noop.  I want compiler not to generate a noop at all.


-- 
H.J.