Re: [gentoo-dev] [RFC] C++ standard in ebuilds

[Guilherme Amadio <amadio@gentoo.org>]

On Mon, Sep 17, 2018 at 10:24:48AM -0700, Matt Turner wrote:
> I don't understand what a potential solution would be.
> 
> The various projects use -std=c++XXX because that's what their code
> requires. -std=c++XXX can't generally be changed. If a dependent
> project is incompatible that's no different than any other case of
> incompatible dependencies in Gentoo.
> 
> I think -std=c++XXX discussions before happened because gcc changed
> the C++ ABI with -std=c++11. I don't think that's particularly
> relevant here, since as far as I know different -std=c++XXX values
> don't change the ABI with current gcc.
> 
> So I guess my understanding is that there isn't a problem different
> than existing incompatible dependencies, but maybe I have
> misunderstood you.

My concern is with, say, package foo that depends on both bar and baz,
and bar and baz support from C++11 to C++17, but must be compiled with
the same version of the standard so that foo can link against both of
them without having a broken ABI. I think that depending on bar[c++14],
or having a similar mechanism to Python to handle "same version of the
standard" with ${CXXSTD_REQUIRED_USE} or similar in an eclass would be
nice.

Cheers,
-Guilherme