Re: Switching x86_64-linux-gnu to GNU2 TLS descriptors by default

[Andrew Pinski <pinskia@gmail.com>]

On Wed, Dec 13, 2023 at 1:08 PM Andrew Pinski <pinskia@gmail.com> wrote:
>
> On Wed, Dec 13, 2023 at 6:19 AM Florian Weimer via Gcc <gcc@gcc.gnu.org> wrote:
> >
> > I feel like I have asked this before.  Currently, GCC uses calls to
> > __tls_get_addr to obtain the address of global-dynamic TLS variables.
> > On other architectures with support for GNU2 TLS descriptors, those are
> > used by default.
> >
> > Should we flip the default to GNU2 descriptors?  Support has been
> > available in glibc for a long, long time.  Is there any other reason for
> > not doing this?  On the glibc side, the behavior regarding lazy
> > initialization and symbol binding does not change whether the old or new
> > interface is used.
>
> Just FYI, the last time this was asked was 6 years ago but maybe
> things has changed since:
> https://inbox.sourceware.org/gcc-patches/CAMe9rOp_68qpdLz25PoHa1ewB6pGQuVv_+H5bXGFhU05MH9+Vg@mail.gmail.com/

Oh I noticed that was a bug filed before that asking for testcases to
be added for it on x86_64 but it looks like it was not implemented:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=48868

So it might even be broken.

Thanks,
Andrew


>
> Thanks,
> Andrew
>
> >
> > Thanks,
> > Florian
> >