requiring a heap-based objects

[ES Kim]

MEC++ Item 17 explains how to require an object be constructed only
on heap. No automatic, no static objects, that is. But I can't
find how to enforce the requirement for derived classes too.

1. make the base destructor private
No class can be derived from the base. Game over.

2. make the base destructor protected
Derived destructors should be also protected to meet the requirement,
but all bets are off once you forget to declare explicit destructor.
(It's the way most of us do most of the time.)

Any suggestion to enforce the requirement?

 

[Maxim Yegorushkin]

MEC++ Item 17 explains how to require an object be constructed only
on heap. No automatic, no static objects, that is. But I can't

Why would you want to do that?

find how to enforce the requirement for derived classes too.

1. make the base destructor private
No class can be derived from the base. Game over.

2. make the base destructor protected
Derived destructors should be also protected to meet the requirement,
but all bets are off once you forget to declare explicit destructor.
(It's the way most of us do most of the time.)

Another way is to provide interfaces and factory functions, so that a user
has no way to create an object but to invoke the factory:

struct some
{
virtual ~some() {}
virtual void foo() = 0;
};
std::auto_ptr<some> create_some();

 

[Hendrik Schober]

MEC++ Item 17 explains how to require an object be constructed only
on heap. No automatic, no static objects, that is. But I can't
find how to enforce the requirement for derived classes too.
[...]

Wouldn't this work

class heap_base {
public:
void destroy() {delete this;}
private:
virtual ~heap_base() {}
};

or am I missing something?

Schobi

--
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I'm Schobi at suespammers dot org

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