> A reasonable question... but why ask about it for just this one
> case?

Simply because I needed to start somewhere. :-/

Trust me, I'm not done asking questions like this. I just wanted to
have some discussion of this one before introducing the next one.

> __cpp_auto_deduction was one that came up most recently. If you
> need portability, you just don't rely on auto deduction from a
> braced-initializer-list. If you want a T, you use parens; if you
> want an initializer_list<T>, you say so.

I have been wondering about that one as well.

> I've not surveyed the other macros with an eye towards which would
> be useful for writing portable code. My unsubstantiated guess is
> that a large fraction aren't useful for portability, beyond just
> giving a clear #error message.

Indeed.

Remember that SG10 really started work at the Bristol meeting -- at the
point when the feature set of C++14 was just being completed. As a result,
we were racing to try to make sure that C++14 wasn't published far in
advance of any kind of feature-testing recommendation.

This time around, we should be under considerably less time pressure, so we
can afford to think more about the rationale, and define only the macros
that will really be useful in the real world.

Clark