title: Including header file defined by macro
body: <p>I need to provide configuration file, which will describe which STL header files to include. I have found that usually it is done by defining a lot of HAVE_XXX_HEADER macros. I wonder if there's something wrong with explicitly providing header name in a macro. Then instead of testing each variant:</p>
  
  <pre><code>#if defined(HAVE_TR1_UNORDERED_MAP_HEADER)
  #include &lt;tr1/unordered_map&gt;
  #elseif (...)
  #endif
  </code></pre>
  
  <p>you could simply have:</p>
  
  <pre><code>#define UNORDERED_MAP_HEADER &lt;tr1/unordered_map&gt;
  (...)
  #include UNORDERED_MAP_HEADER
  </code></pre>
  
  <p>which in addition brings flexibility, since header name is not hard coded inside configured file.</p>