c++ - Covariant clone function misunderstanding -

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this question related recent 1 polymorphism not working function return values of same data type (base , inherited class)

consider code:

#include <iostream> #include <typeinfo>  class base { public:     virtual  base * clone()     {         base * bp = new base ;         return bp ;     } };  class derived: public base { public:     derived * clone() override     {         derived * dp = new derived ;         return dp ;     } };  int main()  {     base * bp = new derived;     auto funky = bp->clone();     std::cout << typeid(funky).name() << std::endl; }

the output p4base (i.e. pointer-to-base). why this? bp->clone() should invoke covariant virtual derived* derived::clone via base* pointer, type of bp->clone() should derived*, not base*.

the declaration

auto funky = bp->clone();

is equivalent to

base* funky = bp->clone();

since base::clone returns base*.

checking type of pointer yields base*.

checking type of pointee different matter, when base type polymorphic. , in presented code base polymorphic because clone virtual. understand more of functionality, check type of pointee instead of type of pointer.


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