c++ - when the shared pointers gets destroyed? -

i reading following piece of code explained comments.

#include <memory>  struct myclass {     ~myclass() {         cout << "dtor" << endl;     } };  void myfunc() {     shared_ptr<myclass> sp2;     {         shared_ptr<myclass> sp( new myclass);         myclass& obj = *sp;         sp2 = sp; // ok, resource shared         myclass& obj2 = *sp; // ok, both pointers point same resource         // sp destroyed here, yet no freeing: sp2 still alive     }     cout << "out of inner block" << endl;     // sp2 destroyed here, reference count goes 0, memory freed } 

my question is, how come both pointers point same resource myclass& obj2 = *sp;? , why sp destroyed @ point reach comment // sp2 destroyed here, reference count goes 0, memory freed?

my question how come both pointers point same resource myclass& obj2 = *sp;?

that not make sense. meant:

myclass& obj2 = *sp2; // ok, both pointers point same resource                  ^^^ sp2, not sp 

and why sp destroyed @ the place commented?

that's because sp constructed in nested scope introduced

shared_ptr<myclass> sp2; {  // starts new scope   .... } // ends scope 

at end of nested scope, automatic variables destructed.

from standard:

3.7.3 automatic storage duration [basic.stc.auto]

1 block-scope variables explicitly declared register or not explicitly declared static or extern have automatic storage duration. storage these entities lasts until block in created exits.