Re: USE_LANGUAGES and wrappers

[Greg Troxel <gdt%lexort.com@localhost>]

Joerg Sonnenberger <joerg%bec.de@localhost> writes:

> On Wed, Jul 19, 2023 at 02:13:53PM +0000, nia wrote:
>> "cwrappers should always default to oldest version of the C/C++ standard
>> unless -std=XX is given" is not quite as trivial but should also be doable.
>
> This is going to seriously annoy any one using a compiler defaulting to
> a newer language mode when it also introduces any ABI differences. So
> when given a choice between pissing off users on modern system and some
> fallout on outdated systems, I'm strongly inclined to go with the
> former.

Do people really think it's ok for a compiler to change ABI for varying
--std arguments?

Don't we have this issue already with programs that explicitly set
--std, as we have apparently agreed?

Can you describe actual situations with ABI differences?  If so, doesn't
that mean that one cannot soundly mix code built with different C++
versions?  And doesn't that lead to c++11-foo and c++14-foo package
variants, like py38 and py39?

Do you have alternative suggestions for a check to ensure that packages
do not build code that exceeds the declared language version?