Re: Future of C++
On Aug 7, 12:11 pm, Andre Kaufmann <akfmn...@t-online.de> wrote:
Eugene Gershnik wrote:
Nonsense. First of all there is nothing wrong with having a non-
virtual *protected* destructor in a base class. Second introducing
But what it's good for (not to make it virtual) - besides having perhaps
a smaller vtable ?
You might want to have an interface that is destroyed through some
means different from 'delete'. A classical example is intrusive
reference counting:
class Base
{
public:
virtual void add_ref() const = 0;
virtual void sub_ref() const = 0;
protected:
Base() {}
~Base() {}
};
class Derived
{
public:
static Base * get_instance()
{ return new Derived(); }
void add_ref() const
{ ++m_ref_count; }
void sub_ref() const
{ if (--m_ref_count == 0) delete this; }
private:
Derived() : m_ref_count(1)
{}
Derived(const Derived &);
void operator=(const Derived &);
private:
mutable int m_ref_count;
};
The idea is to make sure that Derived lifetime is only manipulated via
add_ref/sub_ref and nobody accidentally delete-s it.
--
Eugene
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