Feedback on clang change (#53194)

[Marcus Calhoun-Lopez]

It is hard to argue with your position.
For my own personal work, I have no need of my own proposals.
My main motivation has been to support Qt and GNU Octave on the widest possible set of systems (and close a couple of tickets).
I am hoping that the proposals will cause minimal disruption at least.
Thank you for the feedback.

-Marcus

> On Jan 31, 2017, at 1:35 PM, Chris Jones <jonesc at hep.phy.cam.ac.uk> wrote:
> 
> Hi,
> 
> To be blunt, i am not in favour of any of your proposals. I do not think we should have any update that allows builds to default to using macports stdlibc++. Old (ancient in my view) systems where the system c++ runtime is stdlibc++ should be allowed to die the graceful death they deserve. On other systems, when the system clang compiler does not support the features a specific port requires, then those ports can blacklist those compilers such that the macports clang compilers, using libc++, are preferred. Thats it, nothing else.
> 
> Chris
> 
>> On 31 Jan 2017, at 6:48 pm, Marcus Calhoun-Lopez <mcalhoun at macports.org> wrote:
>> 
>> In the recent mailing list discussion on C++11, there were no comments on the specific aspects of the proposal
>> (https://lists.macports.org/pipermail/macports-dev/2017-January/thread.html#35173).
>> There is one aspect in particular that I would like to ask about: the proposed changes to clang (https://trac.macports.org/ticket/53194).
>> Any comments would be greatly appreciated.
>> 
>> There are three ways to allow clang to refer to MacPorts libstdc++.
>> 
>> 1) Create a *default* variant to have -stdlib=libstdc++ refer to MacPorts libstdc++.
>>   This was quite rightly rejected because clang should be “as compatible with the host as possible.”
>>   I only bring it up because the required patch is simpler.
>> 
>> 2) Create a new command switch -stdlib=macports-libstdc++ to refer to MacPorts libstdc++.
>> 
>> 3) Create a new subport clang-libstdcxx for which -stdlib=libstdc++ refers to MacPorts libstdc++.
>>   Again, a reason to do this is because the required patch is simpler.
>> 
>> #2 is already in the development versions of clang
>> (https://github.com/macports/macports-ports/commit/c68d69b898fece7fea96b61ae0dd33650f628289
>> and
>> https://github.com/macports/macports-ports/commit/49bd2ee7c1e54f290cb6fe07a084de8a2abddb66),
>> but for my purposes, the variant would have to be the default.
>> 
>> Patches for all three proposal are attached to the ticket.
>> 
>> Thank you,
>> Marcus
>