title: C++ no 'object' file generated
body: <p>This is some code to get an environment variable from inside Qt, however, it seems Qt's <code>QProcessEnvironment::systemEnvironment()</code> only reflect a new environment variable change after reboot. So I am thinking about using getenv.
  However I got <code>"error C2220: warning treated as error - no 'object' file generated"</code> from this :</p>
  
  <pre><code>QProcessEnvironment env = QProcessEnvironment::systemEnvironment();
  const QString ENGINE_ROOT = env.value("ENGINE_ROOT", "") != "" ? 
  env.value("ENGINE_ROOT","") : QString(getenv("ENGINE_ROOT"));
  </code></pre>
  
  <p>Don't tell me something like disable /WX or lower W4 to W3, I don't want to hear this, I want to know exactly what cause </p>
  
  <blockquote>
    <p>no 'object' file generated</p>
  </blockquote>
  
  <p>.</p>