#include <stdio.h>
#include <stdlib.h>

int string_length(char * my_string)
{
  int counter = 0;
  while(1)
  {
    if (my_string[counter] != 0)
    {
      counter++;
    }
    else
    {
      break;
    }
  }

  return counter;
}


char * copy_string(char * input)
{
  int length = string_length(input);
  char * result = (char *) malloc(sizeof(char) * (length + 1));

  int i;
  for (i = 0; i <= length; i++)
  {
    result[i] = input[i];
  }

  return result;
}



struct person
{
  char * name;
  int age;
};


void foo(struct person * p1)
{
  p1->age = 30;
  p1->name = copy_string("john");
}


int main()
{
  struct person p;
  p.name = copy_string("mary");

  foo(&p);
  // note that p.name changes in foo.
  printf("p.name = %s\n", p.name);
}