Re: C++ language: Cloneable cl*****

On 6 mai, 20:46, Krzysztof Czainski <1czaj...@[EMAIL PROTECTED]
> wrote:

> I don't understand where do I require default-constructible?

My bad, I had incorrectly read.


> Can You perhaps
> see a way to avoid usage of new?

struct Cloneable
{
     virtual std::size_t sizeof_() const = 0; // returns size of object
     virtual void clone(void* p) const = 0;   // performs placement-new
on p, copying the object
};

then, for example

const A& a = B();
A* copy;

try
{
     copy = static_cast<A*>(::operator new(a.sizeof_()));
     a.clone(copy);
}
catch(...)
{
     ::operator delete(copy);
     throw;
}

That way the user can choose how to allocate the memory.

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