Solved

How do I delete a pointer (a pointer to an object) ?

Posted on 2003-10-27
6
252 Views
Last Modified: 2010-04-02
Hi C++ experts,

   I have some questions in the following code :
--------------------------------
  class A{
  } ;

  A *p = new A ;
  delete p ;
---------------------------------
  the "delete p" deletes the object "new A", but the pointer p is still there. How do I delete the pointer itself ?
Also, will p be destroyed automatically if it goes out of scope ?
Thanks a lot !!!

meow ...........

0
Comment
Question by:meow00
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
6 Comments
 
LVL 19

Expert Comment

by:Dexstar
ID: 9627835
meow00:

> the "delete p" deletes the object "new A", but the pointer p is still there.
> How do I delete the pointer itself ?
> Also, will p be destroyed automatically if it goes out of scope ?

Yeah, you don't have to "delete" anything unless it is created by "new".  A* p is creating on the stack without "new", so it will just be destroyed when it goes out of scope.  FYI:  You have to "delete p" before p goes out of scope or else there will be no way to delete it.

Hope that helps,
Dex*
0
 
LVL 86

Expert Comment

by:jkr
ID: 9627877
>>How do I delete the pointer itself ?

You mean the value the pointer has?

#define SAFE_DELETE(x) { delete x; x = NULL;}
0
 
LVL 1

Author Comment

by:meow00
ID: 9627892
I see ....
and I am wondering that : is there a certain kind of "destructor" which can be called explicitly to delete the pointer p ? or actually there is no way to do that ? we can only wait until it goes out of scope or the program terminates ?
Thanks a lot !!!
0
Independent Software Vendors: We Want Your Opinion

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

 
LVL 1

Author Comment

by:meow00
ID: 9627918
Actually ... I don't mean the value the pointer has, what I mean is the
"pointer variable p " ... I want to destroy it ... thanks.
0
 
LVL 1

Expert Comment

by:fsign21
ID: 9627953
The pointer p itself will be destroyed automatically if it goes out of scope.

The allocated object will be not deallocated if it goes out of scope, unless you call delete p.

We had a similar question recenly:
http://www.experts-exchange.com/Programming/Programming_Languages/Cplusplus/Q_20772740.html
0
 
LVL 19

Accepted Solution

by:
Dexstar earned 50 total points
ID: 9627960
meow00:

> Actually ... I don't mean the value the pointer has, what I mean is the
> "pointer variable p " ... I want to destroy it ... thanks.

Like I said before.  You can't "destroy it", except to let it fall out of scope.  One way to do is, is to put the use of it inside of {}'s.  Those will tell your compiler to control the scope more tightly.  For example:

void Whatever()
{
     int i = 5;

     {
          int* p = new int;

          *p = i;
   
          delete p;
     } // p will fall out of scope here

     // Try to use p here, and you'll get an error!
}

Dex*
0

Featured Post

Industry Leaders: We Want Your Opinion!

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Introduction This article is a continuation of the C/C++ Visual Studio Express debugger series. Part 1 provided a quick start guide in using the debugger. Part 2 focused on additional topics in breakpoints. As your assignments become a little more …
Go is an acronym of golang, is a programming language developed Google in 2007. Go is a new language that is mostly in the C family, with significant input from Pascal/Modula/Oberon family. Hence Go arisen as low-level language with fast compilation…
The goal of the video will be to teach the user the difference and consequence of passing data by value vs passing data by reference in C++. An example of passing data by value as well as an example of passing data by reference will be be given. Bot…
The viewer will learn how to clear a vector as well as how to detect empty vectors in C++.

726 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question