On Wed, Jul 10, 2019 at 2:34 AM Florian Weimer <fweimer@redhat.com> wrote:

> * Szabolcs Nagy:
>
> > it is clear that 0L is a conforming definition for all
> > conforming c++ compilers.
> >
> > it is less clear if __null is so in all compilers that
> > define __GNUC__.
>
> Why wouldn't something like this be valid for current C++ versions?
>
> static inline constexpr decltype(nullptr) __null{};
> #define NULL __null
>
> I don't see a requirement that NULL must be an expression that can be
> evaluated by the preprocessor.


Is this just for the purposes of argument, or, why would you want to do
that? More sanely, yes, `#define NULL nullptr` would now also be a
conforming definition, but that is an undesirable change in practice for a
variety of compatibility reasons. Toolchains have remained with `#define
NULL __null`, and seem likely to continue to do so indefinitely.

I feel like this thread is kinda going off on a tangent now. Inventing new
and unique ways to define NULL in C++ doesn't really seem a useful thing to
do be doing here...