...
#include <stdio.h>     //  Added line
...
int main(void)
{
  //  Sample call to sprintf() to demo changes in the memory map.
  char stack_buf[64];  //  Added line
  bss_var = sprintf(stack_buf, "%d %d", bss_var, data_var);  //  Added line

  //  Lines below not changed.
  int stack_var = bss_var++ + data_var++;
  int i;
  gpio_setup();
  ...