title: String concatenation using preprocessor
body: <p>is it possible to concatenate strings during preprocessing?</p>
  
  <p>I found this example</p>
  
  <pre><code>#define H "Hello "
  #define W "World!"
  #define HW H W
  
  printf(HW); // Prints "Hello World!"
  </code></pre>
  
  <p>However it does not work for me - prints out "Hello" when I use <code>gcc -std=c99</code></p>
  
  <p><strong>UPD</strong> This example looks like working now. However, is it a normal feature of c preprocessor?</p>