> and users must
  define it to <code class="literal">1</code> to enable the new ABI.)
</p><p> Although the changes were made for C++11 conformance, the choice of ABI
  to use is independent of the <code class="option">-std</code> option used to compile
  your code, i.e. for a given GCC build the default value of the
  <span class="symbol">_GLIBCXX_USE_CXX11_ABI</span> macro is the same for all dialects.
  This ensures that the <code class="option">-std</code> does not change the ABI, so
  that it is straig