title: What are the differences between -std=c++11 and -std=gnu++11?
body: <p>What are the differences between <code>-std=c++11</code> and <code>-std=gnu++11</code> as compilation parameter for gcc and clang? Same question with <code>c99</code> and <code>gnu99</code>? I know about C++ and C standards, it's the differences in the parameters that interest me.</p>
  
  <p>I've read somewhere that it has to do with some extensions but it is not clear to me which ones and how to choose between one or the other for a new project.</p>