C++ deleting a pointer when there are 2 pointers pointing to the same memory locations

Question

Lets say, I have one pointer

int *l1 = new int[100*100];

int *l2 = l1;

Now, l1 & l2 both point to the same sequ

Answer 1

int *l1 = new int[100*100];

With this statement, Integer array of 100*100 is created, i.e. (10,000 *4 bytes). In C int is 4 byte.

With statement,

int *l2 = l1;

delete [] l1;

Answer 2

Here's an analogy which may help you understand.

A pointer is like the address of an apartment building.

Many people may have the address of the same building.

If one of them changes the array (think of renovating the building) everyone will see it as they are all looking at the same thing.

When you 'delete' the array you mark the apartment building as condemned and available for re-development.

Many people may continue to have the address of the now condemned building after it is deleted.

If they reference the array after it's deleted (the building was condemned) it may, or may not, still be present. It depends on if the city got around to demolishing the condemned building. It's not safe to do but there's nothing preventing you from doing it. Sometimes you get lucky and the building is still there. Sometimes you'll find something new was built in that place. Sometimes the building falls down on you.

Answer 3

I2 is not deleted. I2 is now a pointer pointing to a place where you have no idea what is stored. This is because delete[] I1 deletes the variable I1 references not the pointer itself.

Answer 4

i2 still points to the same place, but that memory has now been freed. Trying to access anything through it is undefined behaviour, which means your values may be printed, or your house may catch on fire. It's not up to you.

To be pedantic, neither i1 nor i2 are deleted, but the memory they pointed to is. They still retain their same values, but the memory there can now be reused for other things. It's unsafe to use a pointer that has been passed to delete because the memory might already have something else there.