Interesting C + + questions: Invoking a destructor or not invoking a destructor

1. The following procedure does not call destructors.

Class ABC; 
void del (ABC *pobj) {
	delete pobj;
}

Class abc{public
: 
	ABC () {
		printf ("abc\r\n");
	}
	~abc () {
		printf ("~abc\r\n");
	}
;

void main (void)
{
	ABC *pobj = new abc;
	Del (pobj);
}

2. The following procedure will call the destructor

Class abc{public
: 
	ABC () {
		printf ("abc\r\n");
	}
	~abc () {
		printf ("~abc\r\n");
	}
;

void del (ABC *pobj) {
	delete pobj;
}

void main (void)
{
	ABC *pobj = new abc;
	Del (pobj);
}

3. The reasons are as follows:

Here is the class of the predecessor declaration problem, the 1 function del () just know that ABC is a class, but do not know the address of its destructor, so cannot call its destructor.