title: "Clang: error: no input files" in OS X
body: <p>Following <a href="https://stackoverflow.com/a/19427300/702977">this solution</a>, I use <code>#include "...frontend/tokens.mll"</code> in my <code>lexer.mll</code>, then I use <code>cpp -P frontend/lexer.mll -o frontend/gen/lexer.mll</code> to generate the complete mll file. This solution worked before under Ubuntu. </p>
  
  <p>Now, I try to do this in <code>Mac OS 10.11.1</code>, it gives an error <code>clang: error: no input files</code>.</p>
  
  <p><code>gcc -v</code> returns</p>
  
  <pre><code>Configured with: --prefix=/Library/Developer/CommandLineTools/usr --with-gxx-include-dir=/usr/include/c++/4.2.1
  Apple LLVM version 7.3.0 (clang-703.0.29)
  Target: x86_64-apple-darwin15.0.0
  Thread model: posix
  InstalledDir: /Library/Developer/CommandLineTools/usr/bin
  </code></pre>
  
  <p>I don't see where I use XCode, or PCH file. Does anyone know how I should configure the environment to make <code>cpp</code> work?</p>
  
  <p><strong>Edit 1:</strong></p>
  
  <p><code>cpp --version</code> returns</p>
  
  <pre><code>Apple LLVM version 7.3.0 (clang-703.0.29)
  Target: x86_64-apple-darwin15.0.0
  Thread model: posix
  InstalledDir: /Library/Developer/CommandLineTools/usr/bin
  </code></pre>
  
  <p>And an example from the comment:</p>
  
  <p><a href="https://i.stack.imgur.com/DB6EC.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/DB6EC.png" alt="enter image description here"></a></p>