> > For my money, if the only plausible use of a feature-test macro would be to
> > control a #error directive, that's not enough justification to create the
> > macro. Here's how SD-6 already says it:

> OK, I think this is an entirely reasonable position. On that basis, I think
> we do not want a macro for N4051. (I think we also don't want a
> __cpp_digit_separators macro; how do we feel about removing it from our
> recommendations?)

Here's an elliptical answer: we have a precedent for doing this; see N3659,
for shared_mutex. We made a mistake, and we corrected it, without trying to
cover up the fact of the mistake.

Clark