Solved

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

Posted on 2003-10-27
6
217 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
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
Enabling OSINT in Activity Based Intelligence

Activity based intelligence (ABI) requires access to all available sources of data. Recorded Future allows analysts to observe structured data on the open, deep, and dark web.

 
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

How to run any project with ease

Manage projects of all sizes how you want. Great for personal to-do lists, project milestones, team priorities and launch plans.
- Combine task lists, docs, spreadsheets, and chat in one
- View and edit from mobile/offline
- Cut down on emails

Join & Write a Comment

When writing generic code, using template meta-programming techniques, it is sometimes useful to know if a type is convertible to another type. A good example of when this might be is if you are writing diagnostic instrumentation for code to generat…
What is C++ STL?: STL stands for Standard Template Library and is a part of standard C++ libraries. It contains many useful data structures (containers) and algorithms, which can spare you a lot of the time. Today we will look at the STL Vector. …
The viewer will learn how to pass data into a function in C++. This is one step further in using functions. Instead of only printing text onto the console, the function will be able to perform calculations with argumentents given by the user.
The viewer will learn additional member functions of the vector class. Specifically, the capacity and swap member functions will be introduced.

706 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

Need Help in Real-Time?

Connect with top rated Experts

12 Experts available now in Live!

Get 1:1 Help Now