new/delete problems, please help

Hi,
I ran across this problem with the new/delete operators:
I allocate an array with new then perform some operations on it.
Then when use delete my debugger screams: 'unmapped memory exception'.
In the same code I also allocate a second array, perform almost the same operations and it deletes allright. Both of these pointers are mebers of a class and the delete operations performs from a public method of the class. The delete-statements looks like this:

Code:

---

if(pointer!=nil)
      delete pointer;

---

can anyone tell me my mistake here...?
It's really annoying as hell!!!
Never had these problems before...

//btq

To delete an array, use:

delete [] pointer;

ok, so I found part of the problem still no solution!
These pointers points to Bla, a class I've made.
I declare the as:

Code:

---

Bla *one;
Bla *two;

---

If I delete two I get the error. However, if declare it as:

Code:

---

Bla *two;
Bla *one;

---

,I can't delete one instead...?
How come??

thanks
/btq

[edit]
I tried use delete [] pointer; but I got the same error...

Please post some code.

it goes a little somthing like this:

Code:

---

class Note{
    public:
    int p, v, s, d;
    void SetNote(int, int, int, int);
    Note();
}

Note::Note(){
    p=0;
    d=0;
    v=0;
    s=0;
}

class Seq{
    ...
    Note *oldN;
    Note *newN;
    int count;
    void Select();
    Seq();
    ...
}

Seq::Seq(){
...
newN = new Note[count];

}

void Seq::Select(){
...
...
    oldN=new Note[count];
    for(i=0;i<count;i++)
        oldN[i] = newN[i];
    if(newN!=nil)
        delete newN; //<--THIS PRODUCES THE ERROR!!!
...
...
}

---

hmm...obviously this isn't the full code but I thought since the code is rather big and on another computah I only include the parts. Hopfully the above is enough to discover the error...:)

//btq

you've already been given the answer to your problem!

if you do this:

blah = new something[number];

then use:

delete [] blah;

not

delete blah;

Code:

---

>    if(newN!=nil)
>        delete newN; //<--THIS PRODUCES THE ERROR!!!

---

I've never seen nil used. Isn't it NULL? Maybe this is something I haven't learned.

However the above code may be your problem, as you never set newN to NULL after deleting it. Try this and see what happens:

Code:

---

    if(newN!=NULL)
    {
        delete [] newN; //<--THIS PRODUCES THE ERROR!!!
        newN = NULL;
    }

---

Also, I'm assuming you have count initialized to some value. It isn't automatically initialized to 0.

well, it seems that I did had gotten my question answerd. The strange part is that this didn't work the first time.
How come delete array; works sometimes?. I guess the answer is that it might work but sometimes it doesn't so you're better off with delete [] array;...? Or am I way off(as I usually am)?

Oh, and nil is the same as null i.e:

Code:

---

#define NULL 0L
#define nil NULL

---

thanks for yer help...:)

/btq

I have no idea if the above has any side-effects. Most probably not. But 0 is an integer and should be viewed that way.

Probably is best to code #define NULL 0

If not for anything else, at least to avoid possible implicit casts when freeing dynamic memory.

>How come delete array; works sometimes?. I guess the answer is that it might work but sometimes it doesn't so you're better off with delete [] array;...? Or am I way off(as I usually am)?

I can't explain why it works sometimes. I have to admit I've accidently forgot the [] before, and delete seemingly worked fine. However just because my program didn't bomb doesn't mean it deleted the memory properly. Behind the scenes this may cause a memory leak, which will make the operating system unstable at some time in the future. Every time your program is run, it gets loaded into a different place in memory, so it may run one time, and bomb the next time.

It's kind of analogous to the case where a programmer writes a program which runs fine at school. They then take it home and compile it and it won't run. Is it the home compiler's fault? Probably not, there's probably a bug in their code which didn't show up on their school computer.