Checking if a pointer is allocated

How can I check if my pointer has allocated memory?

I want to use delete [] on it, but I can't unless I know its already allocated... and a bool won't work well... how can I check a memory address to see if

address = new char[blah]

has been executed?

Code:

---

                        if (operand.charptr != NULL)
                        {
                                cout << "Freed";
                                delete [] operand.charptr;
                        }
                        if (operand.charptr == NULL)
                        {
                                operand.charptr = new char[strlen(temp)];
                                strcpy(operand.charptr,temp);
                        }

---

Thats what I was trying to do.

well usually you do

Code:

---

int *ptr = new int;

if(ptr==NULL){
  cout<<"Allocation error";
}

---

how would I do what I'm trying to do?

It doesn't seem to ever do the delete because it never outputs the string

well it looks like you're trying to delete the pointer if there already is one, and then create a new one. you can just take out the if statements and do

Code:

---

delete [] operand.charptr;
operand.charptr = new char[strlen(temp)];
strcpy(operand.charptr,temp);

---

because even with the if statements, it will do the same thing

and im not quite sure, you might have to do
operand.charptr = new char[strlen(temp)+1];
to accomodate for the null character at the end

eh yeah.

Let me explain again:

The first time this is run, there is NO allocation.

Every time after, there is. I can't delete it the first time, obviously

oh, then you don't need a delete[] if you're allocating it for the first time..you only can delete if you've allocated it with new at least one time already

Quote:

---

Originally posted by the Wookie
oh, then you don't need a delete[] if you're allocating it for the first time..you only can delete if you've allocated it with new at least one time already

---

I know, which is why I have this post. . .

I need to know how to check whether or not delete[] should be used.

Quote:

---

Originally posted by Trauts
The first time this is run, there is NO allocation.

---

you dont need it if its the first time though

Quote:

---

Originally posted by the Wookie
you dont need it if its the first time though

---

I KNOW THAT!!! This might be run more than once, however, and I want to free the memory, but I can't do that the first time! The second time I absolutely have to.

lol ok, its in a loop or something? what do you mean run more than once?

Initially set the pointer to NULL. delete and delete[] take no action on a NULL pointer. So first time through itt'l be NULL, and delete'ing it will do nothing.

create a new int that counts runtimes... if it's set to zero, don't delete, if it's set to anything other (true) then delete... just increment it after every run... there's probably better ways than that though...

Quote:

---

Originally posted by Eibro
Initially set the pointer to NULL. delete and delete[] take no action on a NULL pointer. So first time through itt'l be NULL, and delete'ing it will do nothing.

---

thats what i said..apparently thats not what he wanted

Code:

---

// operand.charptr needs to be initialized to NULL

if( operand.charptr != NULL )
{
        cout << "Freed";
        delete [] operand.charptr;
        operand.charptr = NULL; // new !
}
if( operand.charptr == NULL ) // always true now, obsolete
{
        operand.charptr = new char[strlen(temp)];
        strcpy(operand.charptr,temp);
}

---