delete - hot to

i have a set of objects of class A as a data member of an object of class B using dynamic memory allocation. In A i got strings with dma.

delete [] A;

gives me a segmentation fault...

it works just fine if A is a string, what is the difference in what i'm doing?

Code:

A* tmpacct;
		tmpacct = new A[arraySize + s];
		for(int i = 0; i<size; i++){
			tmpacct[i] = savings[i];
		}
		// CRAPS OUT HERE ____________________________
		delete [] savings;
		savings = new A[arraySize + s];
		for(int i = 0; i<size; i++){
			savings[i] = tmpacct[i];
		}
		delete [] tmpacct;

		arraySize = arraySize + s;

>> In A i got strings with dma
There could be problems in A's constructor.
There could be problems in A's destructor.
If A doesn't have an overloaded equals operator (and copy constructor) then you could be performing shallow copies of A, which would be bad is A is calling delete in it's destructor.

Use this opportunity to start learning how to use your debugger to track down these issues.

gg

ok, i've pinpointed it to this:

Code:

class A {

   char * cr; //No memory allocation yet.
  
public:
   //...............
   ~A();
};

and it craps out here:

Code:

A::~A() {
	if(cr) {
                // on the next line : 
		delete [] cr;
	}
}

now, cr is just a string of characters... this looks like the book, i'm confused...

what debugger? I compile with c++ on aix (as per requirements)...

Originally Posted by Codeplug

If A doesn't have an overloaded equals operator (and copy constructor) then you could be performing shallow copies of A, which would be bad if A is calling delete in it's destructor.

Here's a program entitled "When Shallow Copy'n Goes Wrong".
Run it, it should be educational...

Code:

#include <iostream>
using namespace std;

class A
{
    char *str;

public:
    A() 
    {
        str = new char[100];
        
        cout << "constructor  -  new 0x" 
             << hex << (int)str << dec << endl;
    }//constuctor

    ~A()
    {
        cout << "destructor - delete 0x"
             << hex << (int)str << dec << endl << flush;

        delete[] str;
    }//destructor
};//A

int main()
{
    A a, b;

    a = b;

    return 0;
}//main

>> what debugger?
gdb

gg

great, that gdb is amazing, i had no ideea there's a debugger for prompt.
I was under the impression that only heavy-graphical-interface applications have a debugger.
(you learn something every day).

thanks!