enabling libc++ by default when building with clang

[David Chisnall]

On 17 Sep 2012, at 20:10, Brooks Davis wrote:

> One key question is, when do we want to throw this switch?  Do we do it
> now so people using clang start using it sooner or do we wait until
> we've switched the default compiler and things have settled a bit?

As dim says, enabling it does not mean requiring things to use it.  I would like to flip this switch as soon as possible so that it's easy for ports people maintaining C++ ports to see if their stuff breaks with -stdlib=libc++.  A few have already tested this, but I'd like to see much wider testing.  

The more important switches to worry about are:

- Changing the default for -stdlib= to libc++ (it's currently libstdc++.  I think I'll probably make it libc++ when std={c,gnu}++11 soon)
- Removing libstdc++ from base and putting it in the compat9 port.

These have the potential to impact users significantly.  Simply having libc++.{so,a} on their system does not unless they explicitly choose to test it.

David