title: fatal error C1189: #error : core.hpp header must be compiled as C++
body: <p>I am building a C application that uses OpenCV.</p>
  
  <p>when compiling, I get the following error:</p>
  
  <pre><code>fatal error C1189: #error :  core.hpp header must be compiled as C++
  </code></pre>
  
  <p>I did not find how to resolve this error.</p>
  
  <p>How to use OpenCV from a C project?</p>