[Bug libstdc++/54005] Use __atomic_always_lock_free in libstdc++ is_lock_free instead of __atomic_is_lock_free

[egallager at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=54005

--- Comment #19 from Eric Gallager <egallager at gcc dot gnu.org> ---
(In reply to Jonathan Wakely from comment #18)
> (In reply to Hans-Peter Nilsson from comment #16)
> > (In reply to Jonathan Wakely from comment #14)
> > > Can we close this?
> > 
> > No.  IIUC, we're still/again using __atomic_is_lock_free with alignment
> > deduced from the current object rather than the type (even though it's now a
> > proxy-object; the faked pointer is constructed from the alignment of the
> > current object).
> 
> It's constructed from __alignof(_M_i) and since r221945 that is given a
> fixed alignment:
> 
>       static constexpr int _S_alignment =
> 	sizeof(_ITp) > alignof(_ITp) ? sizeof(_ITp) : alignof(_ITp);
> 
>       alignas(_S_alignment) __int_type _M_i;
> 
> So it will be the same for all objects of the type.
> 
> There was an additional fix in r227878 for Bug 65913.
> 
> > So, r221701 was wrong to change from null to the alignment-deduced
> > fake-pointer.
> 
> I think the current code is right, and per-type.
> 
> I still want to close this.

With what resolution? FIXED? WORKSFORME?