title: Can #if pre-processor directives be nested in C++?
body: <p>I have a question about Pre-processor directives in c++:</p>
  
  <p>For example:</p>
  
  <pre><code>#ifndef QUESTION
  
  //some code here
  
  #ifndef QUESTION
  
  //some code here
  
  #endif
  
  #endif
  </code></pre>
  
  <p>Can we use it in this way, and can the C++ compiler match the <code>ifndef</code> and <code>endif</code> in the right way?</p>