title: Is there a g++ compiler flag to check if code builds in both c++11 and C++03
body: <p>I have two applications that depend on an internal in house library. One application uses other external libraries that are not ABI compatible with c++11. For this application I must compile my internal library without c++11. </p>
  
  <p>The other application has no external dependencies and I would like to use some c++11 features in it. </p>
  
  <p>I will probably end up modifying the internal library that both these applications depend on. Is there a flag in g++ that will alert me if I am adding features to the internal library that exist in c++11 but not in c++03?</p>