[Development] RFC: handling of C++ feature test macros

[Ville Voutilainen]

On Thu, 19 Sep 2019 at 16:29, Giuseppe D'Angelo via Development
<development at qt-project.org> wrote:
>
> On 19/09/2019 14:56, Ville Voutilainen wrote:
> > I think Peppe's concern, while somewhat theoretical, is a valid one.
> > I'll talk to SG10 about this so that
> > we hopefully never run into the problem in practice.
>
> Thanks! This would also bring up the question on whether it's of any
> importance what values the feature-testing macros are defined to :-)

I already know the answer to that question; it depends on the macro,
and in some cases
different versions have very different meanings. When the features
evolve in ways
that suggest there's a need for detection, the values of existing
macros are bumped.
That might not necessarily mean an incompatibility for users who just
use the older version of the
feature.