Writing a deep copy - copying pointer value

Question

In writing a copy constructor for a class that holds a pointer to dynamically allocated memory, I have a question.

How can I specify that I want the value of the pointer

Answer 1

You allocate new object

class Foo
{
    Foo(const Foo& other)
    {
        // deep copy
        p = new int(*other.p); 

        // shallow copy (they both point to same object)
        p = other.p;
    }

    private:
        int* p;
};

Answer 2

I do not see the context, but the code you posted doesn't seem like copying the pointer, it is exactly what you ask for — copying whatever it points to. Provided that foo points to the allocated object.

Answer 3

I assume your class looks like this.

class Bar {
   Foo* foo;
   ...
}

In order to do a deep copy, you need to create a copy of the object referenced by 'bar.foo'. In C++ you do this just by using the new operator to invoke class Foo's copy constructor:

Bar(const Bar & bar)
{
    this.foo = new Foo(*(bar.foo));
}

Note: this solution delegates the decision of whether the copy constructor new Foo(constFoo &) also does a 'deep copy' to the implementation of the Foo class... for simplicity we assume it does the 'right thing'!

[Note... the question as written is very confusing - it asks for the 'value of the pointer of the copied from object' that doesn't sound like a deep copy to me: that sounds like a shallow copy, i.e. this.

Bar(const Bar & bar)
{
    this.foo = bar.foo;
}

I assume this is just innocent confusion on the part of the asker, and a deep copy is what is wanted.]