title: Using grpc with QtCreator, undefined reference to `grpc::...`
body: <p>I am trying to write some code in C++ in QtCreator to connect to a <code>grpc</code> server when I get this compiler error:</p>
  
  <pre><code>/some/path/serverproxy.cpp:40: error: undefined reference to `grpc::InsecureChannelCredentials()'
  </code></pre>
  
  <p>Here's my <code>grpc</code> includes at the top of <code>serverproxy.cpp</code></p>
  
  <pre><code>#include &lt;grpc++/channel.h&gt;
  #include &lt;grpc++/create_channel.h&gt;
  #include &lt;grpc++/security/credentials.h&gt;
  </code></pre>
  
  <p>and the error comes from this line:</p>
  
  <pre><code>somenamespace::NewStub(
          grpc::CreateChannel("someaddress",
                              grpc::InsecureChannelCredentials()))};
  </code></pre>
  
  <p>I tried adding existing files and adding these headers in QtCreator (although it would be very strange to have to do that manually for the headers to all external libraries), but it didn't work. They are located at <code>/usr/local/include/grpc++/**/*.h</code>.
  Also tried adding <code>INCLUDEPATH += /usr/local/include</code> to my <code>.pro</code> file.</p>
  
  <p>I also tried cleaning the project, running <code>qmake</code> and building again.</p>
  
  <p>What do I have to do to be able to use these <code>grpc++</code> functions?</p>