// CS 1621 Fall 2005
// Handout demonstrating lifetime issues in C++

#include <iostream>
using namespace std;

void tester()
{
   static int stat = 0; // static variable
   int aut = 0;         // stack-dynamic variable
   stat++;   aut++;
   cout << "Stat. var: " << stat << " Auto. var: " << aut << endl;
}

int * getloc()
{
   cout << "Allocating heap-dynamic variable.  Will remain " << endl
        << "until explicit deallocation or end of program. " << endl;
   int * temp = new int;  // temp is stack-dynamic variable, but
   return temp;           // new int allocated is heap-dynamic
}

void loseloc(int * ptr)
{
   cout << "About to deallocate heap-dynamic var." << endl;
   delete ptr;
}

int main()
{
   for (int i = 1; i <= 5; i++)  tester();
   int * ptr = getloc(); // points to heap-dynamic variable
   *ptr = 100;           // give value to location
   cout << "Heap-dynamic: " << ptr << " is " << *ptr << endl;

   // Heap dynamic variable's asserted lifetime is here

   loseloc(ptr);
   int * p2 = new int;
   cout << "Heap-dynamic: " << p2 << " is " << *p2 << endl;
   

   // However the delete call in C++ does not reset the value of the
   // pointer nor does it make the memory inaccessible.  Thus, we can 
   // still access the variable and the heap-dynamic memory even after
   // it has been deleted.  This is called a "dangling reference".
   // Naturally, this is not wise and can lead to serious logic errors.  
   // We will discuss this and other pointer issues in more detail when
   // we discuss memory management.
   *ptr = 250;
   cout << "Heap-dynamic: " << ptr << " is " << *ptr << endl;
   cout << "Heap-dynamic: " << p2 << " is " << *p2 << endl;
}