title: Compiler showing 'pi' symbol on error
body: <p>I was testing some code on <a href="http://coliru.stacked-crooked.com/" rel="noreferrer">Coliru</a>, and I got a strange output. I went down the code and could reproduce it with this simple <a href="http://coliru.stacked-crooked.com/a/66324d1cbd4985bf" rel="noreferrer">piece of code</a>:</p>
  
  <pre><code>int main()
  {
      &amp;pi;
  }
  </code></pre>
  
  <p>The output on g++:</p>
  
  <p><img src="https://i.stack.imgur.com/JlROt.png" alt="output on g++"></p>
  
  <p>clang:</p>
  
  <p><img src="https://i.stack.imgur.com/BbE1J.png" alt="output on clang"></p>
  
  <p>For instance, using just <code>pi</code> (without the address-of) shows the expected result:</p>
  
  <pre><code>main.cpp:3:5: error: 'pi' was not declared in this scope
      pi;
      ^
  </code></pre>
  
  <p>I tried to reproduce this on my machine, using g++ 4.9.2 and on others sites but I could not.</p>
  
  <p>Is this some bug on this site, some config of these compilers ?</p>
  
  <p>And why only using the address-of operator (<code>&amp;</code>) shows this symbol ?</p>