title: In Xcode 4.5, what is "Compiler Default" for "C++ Standard Library" and "C++ Language Dialect"?
body: <p>What is the value of "Compiler Default" for "C++ Standard Library" and "C++ Language Dialect" in Xcode 4.5?</p>
  
  <p>My guess is libstdc++ and GNU++98, but it would be nice to have clarification.</p>
  
  <p>From the <a href="https://developer.apple.com/library/mac/#releasenotes/DeveloperTools/RN-Xcode/_index.html#//apple_ref/doc/uid/TP40001051-SW174" rel="nofollow">Xcode 4.5 release notes</a>:</p>
  
  <blockquote>
    <p>Projects created using this Xcode release use the new libc++
    implementation of the standard C++ library. The libc++ library is
    available only on iOS 5.0 and later and OS X 10.7 and later. 12221787</p>
    
    <p>To enable deployment on earlier releases of iOS and OS X in your
    project, set the C++ Standard Library build setting to libstdc++ (Gnu
    C++ standard library).</p>
  </blockquote>
  
  <p>I notice that creating a new project explicitly sets GNU++11 and libc++, but "Compiler Default" is probably something else.</p>