Re: [PATCH] Decorate string_view members with nonnull attribute

[Jonathan Wakely <jwakely at redhat dot com>]

On 14/06/18 20:02 +0300, Ville Voutilainen wrote:
> On 14 June 2018 at 19:57, Jonathan Wakely <jwakely@redhat.com> wrote:
> > > [macro.names]/2 forbids #defining macros with the same names as the
> > > standard attributes.
> > > The programs Martin shows as examples are not valid.
> >
> >
> > But nonnull isn't a standard attribute though. So we can't use
> > [[gnu::xxx]] attributes in libstdc++ and have to use __attribute__
> > instead.
>
> Oops, indeed. But for gnu-attributes, surely we can decide whatever we
> want about what's
> valid and what's not?

We could say that #defining 'nonnull' and/or 'gnu' as a macro is
undefined, but then programs that the standard says are valid would
fail to compile, and we'd be a non-conforming implementation.

We can use __attribute__(__nonnull__)) so that we accept those
programs (and be a conforming implementation). Why would we choose to
be non-conforming when we don't have to?

We can use [[gnu::__nonnull__]] but that would still reject programs
that #define gnu so maybe we want the front-end to also recognise
__gnu__ as our attribute namespace.