Re: virtual destructor 101

From:

Dragan Milenkovic <dragan@plusplus.rs>

Newsgroups:

comp.lang.c++.moderated

Date:

Wed, 20 Oct 2010 21:49:53 CST

Message-ID:

<i9mm08$vht$1@speranza.aioe.org>

On 10/20/2010 10:31 AM, Bronek Kozicki wrote:

On 19/10/2010 09:53, Dragan Milenkovic wrote:

Doesn't matter which standard. Here is on GCC-4.4

class Stack {
protected:
virtual ~Stack() = 0;
public:
virtual void foo() = 0;
};

Stack * create_stack();
void delete_stack(Stack *); // should call this one!

int main() {
Stack * stack = create_stack();
delete stack; // ERROR! virtual ~Stack is protected
}

Which is by the standard. And it works just fine to support
encapsulating memory management for Stack into factory functions.
But I still feel that this is a wrong place for making memory
management contracts.

Destructor is not memory management contract - overloaded operator new
and delete are.

Destructor belongs to object lifetime management (it's broader subject
than memory!), which I call "object ownership contract". This contract
is an important part of class' interface. If it's missused for memory
management, tough. Making up more rules won't make the language easier
to master.

Thank you for correcting my terminology. I actually meant "ownership
contract". But I disagree that this is a part of the interface of Stack.
It may only be a part of the interface of an implementation as
the choice of ownership and creation can and should be put there.

--
Dragan

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