title: list iterators not compatible unordered_map
body: <p>I have a fairly large project that implements Dijkstra's algorithm to simulate a network sending packets I've run into an issue I have never seen before;</p>
  
  <p>I have managed to narrow the problem down to this:</p>
  
  <pre><code>//Member function of vertex
  unordered_map&lt;Vertex *, int&gt; getEdges()
  {
      return _edges; //same data type as return type
  }
  //Call to member function 
  Vertex *t = //Arbitrary vertex
  unordered_map&lt;Vertex*, int&gt; edges = t-&gt;getEdges();
  </code></pre>
  
  <p>For some reason on the call to this function I receive the error 'list iterators not compatible'. Does anyone understand why this is happening? </p>
  
  <p>EDIT: 
  removed temporarily</p>
  
  <p>EDIT2: 
  Turns out I was getting an empty unordered_map back from getEdges() due to a last minute change I made. Apparently this can cause the 'list iterators not compatible'. </p>
  
  <p>For the sake of other people learning from my mistakes i'll upload the code to a more permanent location in a bit.</p>