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Destructor VS delete

Started by wah_on_2 Apr 21, 2002 at 8:41 AM 4 replies 450+ views

Original Post

Apr 21, 2002 at 8:41 AM

If i created a object dynamically, should i call the object destructor or delete the object directly? and why? e.g.

  
class aThing
{
public:
   aThing(....);
   virtual ~aThing();
   ................
}

void main()
aThing *p;
p = new aThing(....);
               //<----delete p;

               //<----p->~aThing();

               //which one is better?

}

Also, if the aThing class contains a data member that is a objectA. If i use delete p;, will the objectA deleted? Thanks

VolkerG

Apr 21, 2002 at 8:49 AM

For an object created with new you must call delete. The destructor won''t free the memory the object uses on the heap.

Waverider

Apr 21, 2002 at 9:04 AM

The destructor is called just before the deletion takes place. It shouldn't be called directly.

If you have a data member in aThing that is a class, then when the delete for the aThing object is called, the data member will also be removed from memory, after the destructor for the data member is called.

[edited by - Waverider on April 21, 2002 10:06:02 AM]

[edited by - Waverider on April 21, 2002 10:07:23 AM]

Arild Fines

Apr 21, 2002 at 9:07 AM

quote:
Original post by Waverider
It shouldn''t be called directly.

Unless you have been using placement new.

wah_on_2

Apr 21, 2002 at 9:20 AM

I clear now. Thank you.

what is placement new?

Martee

Apr 21, 2002 at 11:49 AM

Placement new is the method by which you can specify the address that an object is allocated at. As Arild said, you must manually call the destructor in this case. Here's a quick example:

      
class SomeCoolClass
{
	...
};


int main(int argc, char* argv[])
{	
	char* buffer = new char[sizeof(SomeCoolClass)];
	SomeCoolClass* p = new (buffer) SomeCoolClass;
		
	p->~SomeCoolClass();
	delete[] buffer;

	return 0;
}

[edited by - Martee on April 21, 2002 12:51:06 PM]

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