Question

For a program of mine I made a small function to clear the various std::vectors of pointers that I have.

template <class S>
void clearPtrVector(std::vector<S*> &a,int size)
{
    for(size_t i = 0; i < size; i++)
         delete a[i];

    a.clear();
}

I must have done something wrong here though since when calling this function in a destructor like so :

clearPtrVector(neurons,neurons.size());

I get the following undefined reference two times:

undefined reference to `void clearPtrVector<Neuron>(std::vector<Neuron*,std::allocator<Neuron*> >&, int)'

I have to admit I am not familiar with what the std::allocator is, so I can not guess what the problem might be here. Any help is really appreciated. Thanks in advance!

-Lefteris

Answer 1

Hot Fix

Write following instead:

  template <class Vector>
  void clearPtrVector(Vector &a)
  {
    for(size_t i = 0; i < a.size(); i++)
         delete a[i];

    a.clear();
  }

Make sure you define the template somewhere where compiler can see it before each use of the template. If you do not create a declaration, you should be safe, as otherwise you should get a compile error. If you do create a declaration for any reason, be double carefull to include definition everywhere as needed.

Redesign

That said, I think the proper solution would be to rethink your design and to use a container which will handle the destruction properly, so that you do not have to do it manually, which is tedious, and almost impossible to do correctly if you need exception safety. Use std::shared_ptr instead of raw pointers, or std::auto_ptr with a container which is able to hold them (std::vector cannot store auto_ptr values). One possible solution would be to use Boost Pointer Container