delete[] - Pointers

[leourb]

I have a question. I have written a little program that uses pointers and does simple things with those. I have only a question about delete[] function.

If I have

	int* p1 = new int[10] {100, 101, 102, 103, 104, 105, 106, 107, 108, 109};   // Allocate and initialize with curly braces parentheses
	                                                                         // a new pointer.
	cout << endl;
	print_array10(cout, p1);

	delete[] p1;

	int* p1 = new int[11] { 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110 };

even if I delete[] pointed memory from free store, why compiler says that I multiple initialize the pointer? Once destroyed I am able to create, if I want, another one with the same name but different random address, don't I?

Thanks!

[Peter87]

You are declaring the variable p1 twice in the same scope which is not allowed. If you remove int* from the last line it should compile without errors.

[leourb]

So even if I destroy before create it again saw that they are in the same scope compiler returns me an error right?

[Disch]

new[] creates an unnamed block of memory. Let's call that memory 'foo':

int* p1 = new int[10] {100, 101, 102, 103, 104, 105, 106, 107, 108, 109};

Here, 'foo' is the array of 10 integers.
'p1' is a local pointer which points to the first element in that array.

delete does not actually delete the pointer, it deletes what the pointer points to (in this case, 'foo'):

delete[] p1;

Here, 'foo' is deleted and no longer exists.
'p1' still exists as a local pointer. Only now it points to bad memory.

int* p1  // <-  this creates p1 AGAIN which will cause an error 

Remember that p1 still exists -- it's just 'foo' that doesn't exist any more. So if you want to have 'p1' point to a new buffer... let's say.... 'foo2':

// get rid of the int* declaration, and just reuse p1:
p1 = new int[11] { 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110 };

// this will create a new array 'foo2', and will make 'p1' point to the first element 

[leourb]

Thanks.. All clear now! :D