explain the last line of output

Question

deleting pointer from.heap meaning?

https://code.sololearn.com/cLolR7k33Pe7/?ref=app

Answer 1

as you have deleted the pointer p now points nowhere. The value it prints is random junk.

Answer 2

@Krupesh; it frees up that memory address for reuse. p still has the memory address, it points to something else or nothing. thus the problem. To make deleting pointers safe'r' empty the pointer *p = nullptr; after deleting it or use smart pointers.

edit: empty the pointers "after" deleting them.

Answer 3

** Just to clarify incase you didnt get notified of the edit.

delete p;
*p = nullptr;

Answer 4

Yes and that's why pointers are dangerous if you use them badly. When you create a pointer, it automatically points on something in the memory.
If you don't attribute something of your code, it can point on anything in the memory ! Such as another variable necessary to an other programm... Then if you do '(*p)++', the programm can crash.
If it is part if the operating system it could occures damages on the computer.

Answer 5

To delete a pointer, you have to allocate it dynamically. You need pointers on pointers...
int **p; // this is a pointer on a pointer...
If you delete a pointer you'll delete its value (adress of the variable pointed) but it won't affect the variable pointed.

Answer 6

thanks jay and jojo.
:)

Answer 7

just want to clarify,
by deleting pointer we mean, the variable address stored inside pointer is erased . ?

Answer 8

got that, thanks @jay

Answer 9

#include <iostream>
using namespace std;

int main()
{
int *p = new int; // request memory
*p = 5; // store value

cout << p <<endl<< *p << endl;

delete p; // free up the memory

cout << p <<endl<< *p << endl;

return 0;
}
/*Output:

address 1
5
address 1 (same as before)
some big no. of type int (STRANGE)

*/