title: error: conversion from long int to non-scalar type, comparing an iterator to null
body: <p>Hello I hope someone can explain this problem. This is the code:</p>
  
  <pre><code>class Memory{
  public:
     PacketPtr   pkt;
     MemoryPort* port;
     MemCtrlQueueEntry(){};
  </code></pre>
  
  <p>};</p>
  
  <p>And after I do:</p>
  
  <pre><code>std::list&lt;Memory*&gt;::iterator lastIter = NULL;
  </code></pre>
  
  <p>And I get the following error:</p>
  
  <pre><code> error: conversion from long int to non-scalar type std::_List_iterator&lt;DRAMMemory::MemCtrlQueueEntry*&gt; requested
  </code></pre>
  
  <p>Where is the problem, of initializing the iterator to NULL?.</p>