[135847] trunk/dports/science/volk

[Michael Dickens]

OK; I think I get the point now; thanks for that additional information,
Ryan.

I think the key here is "support", in the sense of what MacPorts will
guarantee is supposed to work (configurations MacPorts supports):

* MacPorts -does not guarantee- that libstdc++ will work for C++11
support (when using any GCC or Clang); use of it is purely on a port by
port basis as to whether or not it will work. MacPorts will not formally
support this configuration, even if it does work for some ports.

* MacPorts does formally support libc++ and C++11 under specific
versions of Clang (>= 500; 3.3+). Whether using C++11 and libc++ does
work or not then depends on the actual programming used by the port, but
that's beyond the direct scope of what MacPorts provides and guarantees.

OK; fine; I think I get where you're coming from now. Given that I've
tested my ports using both configurations, and they both work, I'm
sticking with keeping both in place. Many of my customers come from the
Linux world and want to initially use GCC; in this manner I can direct
them on how to keep using GCC for now but transition to Clang as they
upgrade their OS and/or get new hardware. As you (or LV) wrote: doing so
might work on a port by port basis, and, as it turns out, it does for
many of my ports. - MLD

On Wed, May 6, 2015, at 08:07 PM, Ryan Schmidt wrote:
> The point is:
> 
> If you want C++11 on a Mac, you need libc++. So you either need 10.9 or
> later, or you need to switch to libc++ on 10.7 or 10.8. Users can switch
> to libc++ on 10.7 or 10.8 by editing macports.conf, and then rebuilding
> all ports. See the wiki page:
> 
> https://trac.macports.org/wiki/LibcxxOnOlderSystems
> 
> We have not switched default installations of MacPorts on 10.7 and 10.8
> to use libc++ because we do not have buildbots set up for this case, and
> not many developers have tested this configuration, and also MacPorts
> base does not contain code that could facilitate an easy upgrade to this
> configuration.
> 
> Using libgcc's libstdc++ for C++11 support is not something we're
> prepared to support in MacPorts. Mixing two different C++ libraries --
> including Apple's libstdc++ and libgcc's libstdc++ -- can lead to
> problems that we want to avoid.
> 
> The simplest answer is that users who want C++11 should use OS X 10.9 or
> later.