title: Specifying 64-bit alignment
body: <p>Given a structure definition like</p>
  
  <pre><code>struct foo {
      int a, b, c;
  };
  </code></pre>
  
  <p>What's the best (simplest, most reliable and portable) way to specify that it should always be aligned to a 64-bit address, even on a 32-bit build? I'm using C++11 with GCC 4.5.2, and hoping to also support Clang.</p>