delete this ? what does it mean ?

david112 (29)
Hi ,

Given this code 


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#include <iostream>
using namespace std;

class A{
public:
        A(){x=1;}
        void func2() {delete this;}
        int x;
};


int main(){

	A a12;
	a12.func2();
	return 0;
}


what does it mean when I say "
delete this;
"

thanks, Davi
Athar (4466)
The object calls delete on itself.
Since a12 was not created using new, this results in undefined behavior (most likely, it will crash).
david112 (29)
There are no compilation errors

meaning is that if we fix that little peace of code , like this : 

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#include <iostream>
using namespace std;

class A{
public:
        A(){x=1;}
        ~A() {cout << "dtor" << endl;}
        void func2() {delete this;}
        int x;
};


int main(){

	A a12;
	cout << a12.x << endl;
	a12.func2();
	cout << a12.x << endl;
	return 0;
}


the output is : 

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1
dtor
1
dtor



Okay , and now if we use dynamic allocation: 

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#include <iostream>
using namespace std;

class A{
public:
        A(){x=1;}
        ~A() {cout << "dtor of A" << endl;}
        void func2() {delete this;}
        int x;
};


int main(){

	A *pa = new A();
	pa->func2();
	cout << pa->x << endl;
	delete pa;
	cout << pa->x << endl;
	return 0;

}


I use new and the output is 
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dtor of A
3280896
dtor of A
3280896


but I can't see that the program does indeed crash ...
ZED0815 (117)
"this" is a pointer to the object itself, "delete" de-allocates the memory pointed to by the argument. In this case the class would "kill itself" by freeing the memory block where it sits. Anyway: don't do it! Its dangerous to do it implicitly as that and hidden from the users eye... ask yourself what would happen if you add a line cout << a12.x before returning?!
david112 (29)
@ZED0815 : please look at my last reply :)
ZED0815 (117)
Oh yes because you proggy is small and fast...so you de-allocate the memory yes? a12 kinds-of still points to a point in memory where the object happens to be...now consider you create a new object in the mean time, the space in memory is free and pretty so your program decides to place the new object where a12 used to be. now a12 points to some memory inside a different object...what happens is a huge fuckup!
ZED0815 (117)
yes I was too lame ;)
wtf (670)
why would you want to delete this anyway?
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