[osg-submissions] osg::Object::clone

[Daniel Trstenjak]

Hi Valery,

> I suggest to you to override type of returning value in realizations of
> functions osg::Object::clone and osg::Object::cloneType in derived
> classes. In this case one will be able to write simply "osg::Transform*
> sTrans = sExistentTrans->clone();" instead of "osg::Transform* sTrans =
> dynamic_cast<osg::Transform*>(sExistentTrans->clone());".

It's not a good idea. The return value of the 'clone' method is
different (gcc 4.1.1) in dependency of the type of the pointer holding
the object.

class A {
   public:
      virtual A* clone() const { return new A(); }
};

class B: public A {
   public:
      virtual B* clone() const { return new B(); }
};

int main() {
   B* b1 = new B();
   B* b2 = b1->clone();

   A* a  = new B();
   B* b3 = a->clone();
}


Greetings,
Daniel

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 Daniel Trstenjak                                 Tel. +49 (0)7071-9457-264
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