title: How to get the size of a user defined struct? (sizeof)
body: <p>I've got a structure with C representation:</p>
  
  <pre><code>struct Scard_IO_Request {
      proto: u32,
      pciLength: u32
  }
  </code></pre>
  
  <p>when I want to ask the <code>sizeof</code> (like in C <code>sizeof()</code>) using:</p>
  
  <p><code>mem::sizeof&lt;Scard_IO_Request&gt;();</code></p>
  
  <p>I get compilation error:</p>
  
  <pre><code>"error: `sizeof` is a reserved keyword"
  </code></pre>
  
  <p>Why can't I use this <code>sizeof</code> function like in C? Is there an alternative?</p>