c++ - method on deleted instance of class still work? -

i have code on visual c++ 2010

#include <iostream> #include <string>  using namespace std;  class human { private:     int magic;     int health;     string name; public:     int getmagic() const;     int gethealth() const;     human(int, string);     ~human();  }; //helper int human::gethealth() const {     cout <<"this returns human::health" << endl;     return human::health;  } int human::getmagic() const {     cout <<"this returns this->magic"<< endl;     return this->magic;  }  //con/destructor human::human(int a, int b, string c): health(a), magic(b), name(c) {     cout<<c<<" born!"<<endl; } human::~human()  {     cout <<this->name << " killed!" << endl; }  int main (){     human lucife(20,10,"lucife");     cout << lucife.gethealth()<<endl;     cout << lucife.getmagic()<<endl;     lucife.~human();      cout << lucife.gethealth()<<endl;     cout << lucife.getmagic()<<endl;     cout<<endl;       lucife.~human();      system("pause");  } 

and when run it:

lucife born! returns human::health; 20 returns this->magic 10 lucife killed! returns human::health 20 returns this->magic 10  killed! 

i have 3 questions:

1. after killed instance "lucife" first time, why did 2 methods gethealth() , getmagic() still worked?
2. the second time called ~human() on instance "lucife", why didn't print out "lucife killed!" first time? happened here? name value deleted?
3. does return human::health , return this->health mean same thing? tried , see there no difference. think both of them return health of instance on method called ("lucife" in case).

many you

as @r , @rupesh mentioned, seeing behavior that's undefined.

however, if may provide little more explanation what's going on in specific code in specific environment, might it.

1. after killed instance "lucife" first time, why did 2 methods gethealth() , getmagic() still worked?

first of all, not call object's destructor explicitly that. automatically fired out of scope main. that's never practice.

the reason can still invoke gethealth() , getmagic() functions first hidden argument this.

you might surprised if see

class aaa { public:     void f() { std::cout << "hello world" << std::endl; } }  ((aaa*) 0)->f(); 

able compiled , running okay. (depending on environment).

so if invoked destructor explicitly in middle of scope hoping literally destruct inside, might still able reach this without dereferencing nullptr , give this intended functions luck.

2. the second time called ~human() on instance "lucife", why didn't print out "lucife killed!" first time? happened here? name value deleted?

it's because when human::~human() fired, destructor of std::string gets fired, ends tidying.

3. does return human::health , return this->health mean same thing? tried , see there no difference. think both of them return health of instance on method called ("lucife" in case).

no, different. in code, human::health converted this->health because used inside class human.