> If two compilers have rvalue references and move constructors, but only
> one defines the macro, the body of inline function f will be different
> between implementations. This is a trivial example -- you can come up
> with similar cases for just about any language feature.

But once we come up with a recommendation for a macro to define when a feature is implemented, wouldn't an implementation that has the feature but doesn't define the macro be considered flawed/buggy? I won't go so far as to say "non-conforming", but certainly not of high quality.

I'm not sure I see the value of taking such perversity into account.

Clark