c++ - 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.

Is that true?

Answer 1

No, it's not true. If a function needs a pointer and has nothing to do with ownership, then I strongly believe that a regular pointer should be passed for the following reasons:

• No ownership, therefore you don't know what kind of a smart pointer to pass
• If you pass a specific pointer, like shared_ptr, then you won't be able to pass, say, scoped_ptr

The rule would be this - if you know that an entity must take a certain kind of ownership of the object, always use smart pointers - the one that gives you the kind of ownership you need. If there is no notion of ownership, never use smart pointers.

Example1:

void PrintObject(shared_ptr<const Object> po) //bad
{
    if(po)
      po->Print();
    else
      log_error();
}

void PrintObject(const Object* po) //good
{
    if(po)
      po->Print();
    else
      log_error();
}

Example2:

Object* createObject() //bad
{
    return new Object;
}

some_smart_ptr<Object> createObject() //good
{
   return some_smart_ptr<Object>(new Object);
}