When should I use raw pointers over smart pointers?

Question

After reading this answer, it looks like it is a best practice to use smart pointers as much as possible, and to reduce the usage of \"normal\"/raw pointers to minimum.

Answer 1

The use of smart pointers is always recommended because they clearly document the ownership.

What we really miss, however, is a "blank" smart pointer, one that does not imply any notion of ownership.

template 
class ptr // thanks to Martinho for the name suggestion :)
{
public:
  ptr(T* p): _p(p) {}
  template  ptr(U* p): _p(p) {}
  template  ptr(SP const& sp): _p(sp.get()) {}

  T& operator*() const { assert(_p); return *_p; }
  T* operator->() const { assert(_p); return _p; }

private:
  T* _p;
}; // class ptr

This is, indeed, the simplest version of any smart pointer that may exist: a type that documents that it does not own the resource it points too.