title: GCC and Clang not warning on unused exception variable
body: <p>Consider the following useless code--specifically, the <code>int k</code> in the <code>catch</code> clause:</p>
  
  <pre><code>int main()
  {
      try
      {
          throw 0;
      }
      catch(int k)
      {
      }
  
      return 0;
  }
  </code></pre>
  
  <p>When compiled with g++ (version 8.3.0) and clang++ (8.0.0) with <code>-Wall -Wextra</code>, no warnings are emitted despite the unused <code>k</code> variable. Visual Studio does warn, which is how I discovered this difference in a project of mine.</p>
  
  <p>Is this a bug in GCC and Clang, or am I misunderstanding the <code>-Wunused</code> set of flags?</p>