C++17

[Marcus Calhoun-Lopez]

Greetings,

There are two pull requests [1,2] that would allow C++17 with the line:
    compiler.cxx_standard 2017

There are two stumbling blocks:
    1) consensus has been elusive on the default values of compiler.cxx_standard and compiler.c_standard [3,4]
    2) there is a concern that the change would negatively impact performance to an unacceptable level [5].

1) is easy to fix once we decide.
It does not matter to me personally since I do not use the older systems.

I am not sure how to fix 2) since I do not know how to implement caching in the base code.

Please forgive me if this is more information than was requested, but I am hoping to move this pull request forward, and any help would be appreciated.

-Marcus

[1] https://github.com/macports/macports-base/pull/88
[2] https://github.com/macports/macports-ports/pull/2772
[3] https://github.com/macports/macports-base/pull/88#discussion_r193841635
[4] https://github.com/macports/macports-base/pull/88#discussion_r228771280
[5] https://github.com/macports/macports-base/pull/88#issuecomment-435279559

> On Dec 8, 2018, at 12:17 PM, Mojca Miklavec <mojca at macports.org> wrote:
> 
> Hi,
> 
> What's the up-to-date recommendation for ports requiring C++17?
> 
> There were several different approaches, some of them probably still
> in PR queue, and I kind of lost track about what a port should do now
> to minimize the effort & copy-paste errors, both now and in the
> future.
> 
> (I would like to avoid the error-prone process of manually
> blacklisting a zillion of compilers in each individual port.)
> 
> Thank you,
>    Mojca