Using -std=c++11 with the macports gcc-4.7 compiler

[Clemens Lang]

On Thu, Jan 17, 2013 at 12:25:57PM -0800, Jeremy Huddleston Sequoia wrote:
> In this case, there are two host C++ runtimes: the old libstdc++ (from
> gcc-4.2.1) and the new libc++ (llvm.org). clang lets you choose which
> one you build against.

OK. Thanks for the explanation. There's some information I couldn't find
on the libc++ website: It claims it supports C++11, but does that also
mean I can build older C++ code against this library?
If that's possible the only bit missing to be able to build everything
against one library is forcing g++ to build and link against libc++.

> The problem is that g++ doesn't support libc++ (AFAIK).

Oh, so that's the bit of information I was lacking, causing me to wonder
why we tried to get this right with multiple C++ stdlib implementations.

However, other people seem to be facing the same problem, too, and it
seems there _is_ a way to have g++ use libc++ (although I have not
verified this):
http://sylvestre.ledru.info/blog/sylvestre/2012/08/15/libc_new_c_standard_library_in_debian

> I'm thinking more along the lines of preventative analysis.  I'd
> rather have the potion to put into the record some notation of what
> C++ runtime the port is using, and if another port is linking against
> it, that port's Portfile can assert that their C++ runtime matches all
> their dependencies.

While that would theoretically work it still might be a problem for
developers using MacPorts. Imagine lib A is built against libc++, lib B
is built against libstdc++. Now a developer wants to write a tool T
linking against lib A _and_ lib B.

-- 
Clemens Lang