LNK2019 error in C++
<p>I'm getting this weird linker error:</p>

<pre><code>Error   1   error LNK2019: unresolved external symbol "public: virtual __thiscall Data::~Data(void)" (??1Data@@UAE@XZ) referenced in function "public: virtual __thiscall Job::~Job(void)" (??1Job@@UAE@XZ) C:\...\Job.obj

Error   2   error LNK2019: unresolved external symbol "public: __thiscall List::DataNode::DataNode(class List::DataNode const &amp;)" (??0DataNode@List@@QAE@ABV01@@Z) referenced in function "public: __thiscall List::List(class List const *)" (??0List@@QAE@PBV0@@Z)    C:\...\List.obj
</code></pre>

<p>from the first error description, it might have something to do with a destructor.</p>

<p>I have an empty and abstract data class with a pure virtual destructor:</p>

<pre><code>virtual ~Data()=0;
</code></pre>

<p>and a class Job which derives from data, with a trivial implementation of the destructor:</p>

<pre><code>Job::~Job()
{
}
</code></pre>

<p>Can you spot a problem? How can I fix it?
Thanks!</p>
