Question

I’m getting this weird linker error:

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 &)" (??0DataNode@List@@QAE@ABV01@@Z) referenced in function "public: __thiscall List::List(class List const *)" (??0List@@QAE@PBV0@@Z)    C:\...\List.obj

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

I have an empty and abstract data class with a pure virtual destructor:

virtual ~Data()=0;

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

Job::~Job()
{
}

Can you spot a problem? How can I fix it?
Thanks!

Answer 1

You need to provide definition for a pure virtual destructor.

C++03 12.4 Destructors
Para 7:

A destructor can be declared virtual (10.3) or pure virtual (10.4); if any objects of that class or any derived class are created in the program, the destructor shall be defined. If a class has a base class with a virtual destructor, its destructor (whether user- or implicitly- declared) is virtual.