glibc 2.21 - Machine maintainers, please test your machines.

[Torvald Riegel]

On Mon, 2015-01-26 at 23:56 +0100, Andreas Schwab wrote:
> Torvald Riegel <triegel@redhat.com> writes:
> 
> > I don't think so, because in a badly 4B-aligned (ie, no 8B-aligned) use,
> > struct new_sem is at offset 4 of the semaphore.  If you copy that to a
> > 8B-aligned semaphore just bit-by-bit, then the actual data will still
> > start at offset 4, but to_new_sem will assume offset 0.
> 
> It is undefined to use a copy of a sem_t in any of the semaphore calls.

I think we all agree on that.  Nonetheless, as I mentioned previously,
I'm not actually aware of where in POSIX (or C?) this would be
explicitly forbidden.  So if you know that, I'd be interested in getting
a reference.