deleting a pointer that was not created with new

**sigur47** · 01-22-2012

Hi, i am wri

Code:

delete current;
                    current=0;

ting a linked list and i would like to know how to delete a pointer that was not created with new.I have tried delete but it does not work.I know that in c , i use free();

Code:

void LinkedListCollection::remove(int item){
    intListElement *previous;
    intListElement *current;
    current=this->head_;
    if(lookup(item==1))
    {
        /*incase the item is in the head
         */
        if(current->num==item)
            this->head_=this->head_->next;
        else
        {
            previous=current;
            current=current->next;
            while(current!=0)
            {
                if(current->num==item)
                {
                    //i would like to delete my current but it wont work for me
                    previous->next=current->next;
                    //delete current;
                    current=0;
                }
                else
                    previous=current;
                    current=current->next;
                
                
             }
        }//else
    }//if
    
    
}

**Salem** · 01-22-2012

> i would like to know how to delete a pointer that was not created with new
The answer is you don't.

If you used malloc(), then you use free()
If you used new, then you use delete.
If you used new[ ] then you use delete[ ]
Anything else is undefined behaviour.

**sigur47** · 01-22-2012

Originally Posted by Salem

> i would like to know how to delete a pointer that was not created with new
The answer is you don't.

If you used malloc(), then you use free()
If you used new, then you use delete.
If you used new[ ] then you use delete[ ]
Anything else is undefined behaviour.

i assigned objects to my pointer like something like this
current=this->head_;

**laserlight** · 01-22-2012

Maybe you just need to set it to be a null pointer.

**sigur47** · 01-22-2012

Originally Posted by laserlight

Maybe you just need to set it to be a null pointer.

Thats what i did i assingned the pointer to null but wont that cause memory leak because that memory has not be deallocated

**laserlight** · 01-22-2012

Originally Posted by sigur47

Thats what i did i assingned the pointer to null but wont that cause memory leak because that memory has not be deallocated

The memory will be deallocated when the object that the pointer used to point to goes out of scope (or when the program ends, if the object has static storage duration).

**sigur47** · 01-22-2012

Originally Posted by laserlight

The memory will be deallocated when the object that the pointer used to point to goes out of scope (or when the program ends, if the object has static storage duration).

I have run the code and my delete method does not work it still contains the item that i deleted.Can you spot any error in my code.

**laserlight** · 01-22-2012

For starters, this looks wrong: lookup(item==1)

Maybe you intended to write: lookup(item) == 1

What does lookup do, anyway?

**sigur47** · 01-22-2012

Originally Posted by laserlight

For starters, this looks wrong: lookup(item==1)

Maybe you intended to write: lookup(item) == 1

What does lookup do, anyway?

Wow i am so sloppy and careless.Look up checks to see if the item is in the linked list before it goes to delete it.

**laserlight** · 01-22-2012

Great, but aren't you already doing that with your current->num==item checks?

**sigur47** · 01-22-2012

Originally Posted by laserlight

For starters, this looks wrong: lookup(item==1)

Maybe you intended to write: lookup(item) == 1

What does lookup do, anyway?

I have solved my problem but i might like to hear your own views on the way i implement my method

**sigur47** · 01-22-2012

[QUOTE=laserlight;1084941]Great, but aren't you already doing that with your current->num==item checks?[/QUOTEThats true so i am repeating code twice on second thoughts

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