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


On Mon, 2015-01-26 at 05:50 -0800, H.J. Lu wrote:
> On Mon, Jan 26, 2015 at 5:48 AM, Andreas Schwab <schwab@suse.de> wrote:
> > "H.J. Lu" <hjl.tools@gmail.com> writes:
> >
> >> 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.
> >
> > The compiler may generate code to take advantage of the bigger
> > alignment, which will fail if not fulfilled (this is not just about
> > unaligned accesses).
> >
> 
> Failure shouldn't happen on x32 in this case.
> 

Then please provide a *detailed* comment why this is the case along with
the alignment change in x86 semaphore.h.  Given that we're discussing
whether this is safe or not, I think we should have detailed
documentation.  And this will also help conclude the discussion.


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