title: Link errors compiling a mixed objective-C/C++ project with C++11 support in xcode 4.5.2
body: <p>I am trying to compile a workspace of 3 projects with C++11 support. This set of projects has successfully compiled and linked using LLVM compiler defaults. In addition, the c++ code has previously compiled on a number of compilers including g++, llvm, msvc, sun, irix etc so it is very clean code.</p>
  
  <p>Under the c++ language dialect section of the workspace build settings there are 3 line items:</p>
  
  <p>c language dialect<br>
  c++ language dialect<br>
  c++ standard library  </p>
  
  <p>Using the settings:</p>
  
  <p>c language dialect: compiler default<br>
  c++ language dialect: compiler default<br>
  c++ standard library: libc++ (LLVM c++ standard library with c++11 support)  </p>
  
  <p>I can successfully compile but get many link errors. Some are from our own functions and some are from standard functions. Here is a sample of link errors to standard functions:</p>
  
  <p>(null): "std::string::find_last_of(char const*, unsigned long) const", referenced from:
  (null): "std::string::size() const", referenced from:</p>
  
  <p>It seemed clear that I was linking to the wrong standard library, so I investigated changing  various options above. Changing the dialect to -std=c++11 even broke my compilation. I could not find a combination that worked for me.</p>
  
  <p>Can you suggest what might be wrong?</p>
  
  <p>EDIT: my motivation for doing this is that I want to use std::thread in my c++ code that interfaces with objective-c (and have that c++ code still be portable)</p>