Compiler-dependent infinitely loop bug by stack allocation policy

infinitely_loop_bug_by_stack_allocation.cpp

/*

g++ main.cpp -W -Wall
./a.out
addr x : 7ffc853ffcf4
addr y : 7ffc853ffcf8
addr diff: -4
addr i    : 7ffc853ffce4
addr array: 7ffc853ffcf0
curr addr : 7ffc853ffcf0
curr addr : 7ffc853ffcf4
curr addr : 7ffc853ffcf8


clang main.cpp -W -Wall
./a.out
addr x : 7ffd5dfc3abc
addr y : 7ffd5dfc3ab8
addr diff: 4
addr i    : 7ffd5dfc3ab8
addr array: 7ffd5dfc3ab0
curr addr : 7ffd5dfc3ab0
curr addr : 7ffd5dfc3ab4
curr addr : 7ffd5dfc3ab0
curr addr : 7ffd5dfc3ab4
curr addr : 7ffd5dfc3ab0
ERROR: Infinitely Loop!!!
*/

/*
Reference
http://stackoverflow.com/questions/1102049/order-of-local-variable-allocation-on-the-stack
 */
#include <cstdio>

void simple_addr_order()
{
  int x;
  int y;
  int diff = (unsigned long)&x - (unsigned long)&y;
  printf("addr x : %lx\n", (unsigned long)&x);
  printf("addr y : %lx\n", (unsigned long)&y);
  printf("addr diff: %d\n", diff);
}

void buggy_loop()
{
  const int ARRAY_SIZE = 2;

  int i = 1234;
  int array[ARRAY_SIZE];

  printf("addr i    : %lx\n", (unsigned long)&i);
  printf("addr array: %lx\n", (unsigned long)array);

  int loop_count = 0;
  for(i = 0 ; i <= ARRAY_SIZE ; ++i) {
    array[i] = 0;
    printf("curr addr : %lx\n", (unsigned long)&array[i]);

    loop_count++;
    if(loop_count > ARRAY_SIZE + 2) {
      printf("ERROR: Infinitely Loop!!!\n");
      break;
    }
  }
}

int main()
{
  simple_addr_order();
  buggy_loop();
  return 0;
}