program crash uppon deleteing pointer to an array

Question

upon trying to delete the pointer obs I get a crash (im suspecting garbage data) if I run this and enter 1 and fill out the questions, the array increments right, and is able to delete. but upon running this and entering 1 twice (both filling out data). I get a crash. the array is incremented, and holds both sets of data that I have entered. also I am unable to use vectors, due to this being a school project.

#include <fstream> 
#include <iostream> 
#include <iomanip> 
#include <string>

using namespace std; 

#include "fileStuff.h"

bool menu();
bool menuOptions(int option);
void fileIO();
void listAll(interact * obs, int arryO);
interact addOne(interact * obs, int size); 
interact subOne(interact * obs, int size);

int main() 
{ 

    bool isRunning = true;
    while (isRunning)
    {
        isRunning = menu();
    }
    return 0; 
}
interact addOne(interact * obs, int size)
{
    interact *temp = new interact[size];
    cout << temp[0].getBagId() << " from method." << endl;
    for (int i = 0; i < size ; i++)
    {   
        cout << temp[i].getBagId() << endl;

        temp[i] = obs[i];

    }

    return *temp;
}
interact subOne(interact * obs, int size)
{
    return *obs;
}
bool menu()
{
    int option = 0;
    cout << "1: add new backpack. " << endl
        << "2: delete a backpack "<< endl
        << "3: sort ascending by id " << endl
        << "4: sort descending by id " << endl
        << "5: list all backpacks " << endl
        << "6: quit" << endl;
    cin >> option;
    return menuOptions(option);
}

bool menuOptions(int option)
{
    static int arrayO = 0;
    cout << arrayO << endl;
    static interact *obs = new interact[arrayO];
    fileStuff test;
    int tempBagId = 0, tempInvSpaces = 0, tempAmtOfItemsInInv = 0;
    double tempInvMaxWeight = 0.0;
    string tempBagType, tempBagCondish;
    int t = 0 ;
    int i = 0;
    switch (option)
    {
    case 1:
        cout << "bagId? ";
        cin >> tempBagId;
        cout << "How many inv spaces? ";
        cin >> tempInvSpaces;
        cout << "How much weight can the bag hold? ";
        cin >> tempInvMaxWeight;

        obs[arrayO].setBagId(tempBagId);
        obs[arrayO].setInvSpaces(tempInvSpaces);
        obs[arrayO].setInvMaxWeight(tempInvMaxWeight);

        //      test.writeToFile(obs, arrayO);
        cout << "all stored" << endl;

        arrayO++;
        *obs = addOne(obs, arrayO);
        cout << obs[0].getBagId() << "ERE" << endl;
        break;

    case 5:
        //list all
        listAll(obs, arrayO);
        break;

    case 6:
        obs = NULL;
        delete obs;
        //      exit(0);
        return false;
        break;
    default:
        break;
    }
}


void listAll(interact * obs, int arryO)
{
    int i = 0;
    for (i; i <= arryO; i++)
    {
        cout << (obs + i)->getBagId() << endl;
        cout << (obs + i)->getInvSpaces() << endl;
        cout << (obs + i)->getInvMaxWeight() << endl;
    }
}

Answer 1

You allocate obs with

static interact *obs = new interact[arrayO];

But deallocate it with:

delete obs;

Use delete[] instead.

---

Also you're clearing obs before you delete it, which never has a chance of working properly.

---

As pointed out by @piwi, the second time you don't initialize it, because it's a static variable.

---

Frankly, though, the purpose of dynamic allocation is unclear for me here. Aside from the fact that it shouldn't be a static in the first place, but a class instance instead, you can just use value semantics and std::array.

Answer 2

Your code has multiple errors. The memory corruption starts, though, when you allocate an array of size array0 and then access obs[array0]. The index is one too many already, and as array0 gets bigger it just goes further off the end of your allocated array.

Also, your addOne function is completely wrong. It allocates a new, larger array, carefully copies the data into it, then returns the contents of the first element of the new array (not the new array itself). The new array itself is just discarded (leaked), since you don't return the pointer to it.

As to the actual delete, Bartek is of course correct that it should be delete[], but in any case you only ever delete a null pointer:

obs = NULL;
delete obs;

This doesn't do anything to the array that obs used to point to before you assigned a null pointer to obs.