0x000000000040083b in reverse (s=0x400b2b "hello") at pointersExample.c:72
72        *q = *p;

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


struct book
{
  char* title;
  int   pages;
  float price;
};


void modifyInt (int *li)
{
  *li *= 2;
}


void modifyStruct (struct book* lb)
{
  char* newTitle = "The best book";

  free(lb->title);
  lb->title = malloc((strlen(newTitle) + 1) * sizeof(char));
  strcpy(lb->title, newTitle);

  lb->pages=350;
  lb->price=20.25;
}


void modifyString (char* lw)
{
  int i;
  int strLen = strlen(lw);

  for (i=0; i<strLen; i++)
    if( (*(lw+i) >= 97) && (*(lw+i) <= 122) )
      *(lw+i) -= 32; // Converts letters to upper case.
}


void reverse (char* s)
{
  char* aux;
  char* p;
  char* q;

  p = s;
  int len = strlen(s);
  aux = (char*) malloc ((len + 1) * sizeof(char));

  printf("s=%s\n", s);

  printf("strlen(s)=%d\n", len); 
  *(aux+len) = 0; // End string mark.
  len--; 
  while (*p != 0)
  {
    *(aux+len) = *p;
    len--;
    p++;
  }
  printf("aux=%s\n", aux);

  // Copy aux to s.
  p = aux;
  q = s;
  while (*p != 0)
  {
    *q = *p;
    p++;
    q++;
  }

  printf("aux=%s\n", aux);
  printf("s=%s\n", s);
}


int main()
{
  int iv = 10;
  struct book *mynewbook;
  int len;
  char* words1;
  char* initial_words = "hello_pleased_to_met_you" ;
  char* tmp = "hello";

  printf ("\niv = %d\n", iv);
  modifyInt(&iv);
  printf ("After calling modifyInt, iv = %d\n\n", iv);

  mynewbook = (struct book*)malloc (sizeof (struct book));
  if (mynewbook == NULL)
    return -1;

  len = strlen("Unknown"); 
  mynewbook->title = (char*) malloc ((len + 1) * sizeof(char));
  strcpy(mynewbook->title, "Unknown");
  mynewbook->pages=0;
  mynewbook->price=0.0;
  printf ("mynewbook: title = %s, pages=%d, price=%f\n",
           mynewbook->title, mynewbook->pages, mynewbook->price); 
  modifyStruct(mynewbook);
  printf ("After calling modifyStruct: mynewbook: title = %s, pages=%d, price=%f\n\n",
            mynewbook->title, mynewbook->pages, mynewbook->price); 

  len = strlen(initial_words); 
  words1 = (char*) malloc ((len + 1) * sizeof(char));
  strcpy(words1, initial_words);
  printf ("words1 = %s\n", words1);
  modifyString(words1);
  printf ("After calling modifyString: words1 = %s\n\n", words1);

  printf("tmp=%s\n" , tmp);
  reverse(tmp);
  printf("After calling reverse: tmp=%s\n\n" , tmp);

  return 0;
}