Question

Check out this code

#include<stdio.h>

int main()
{

 const int a=7;
 int *p=&a;
 (*p)++;
 printf("*p=%d\np=%u\na=%d\n&a%u",*p,p,a,&a);
 getch();
}

The output you get for this is

*p=8
p=1245064
a=8
&a1245064

How is this possible?? We declared variable a as constant. Doesnt this mean that the location pointed to by a can never be changed during the course of pgm execution??

Answer 1

That’s undefined behavior – in your case it is working as you described, but it could just as well crash the program or cause any other problems. In your case const doesn’t prevent the compiler from allocating the variable in modifiable memory, so you technically can modify it by obtaining a pointer to that variable and working through the pointer.