/* File: malloc3.c
  
   A common mistake using dynamically
   allocated arrays.
*/

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

#define TOP 17

main() {
   double *ptr1, *ptr2, *ptr3 ;
   int i ;


   /* Get memory for an array using malloc */

   ptr1 = (double *) malloc(TOP*sizeof(double)) ;
   if (ptr1 == NULL) {
      fprintf(stderr, "malloc() failed!\n") ;
      exit(1) ;
   }


   /* Initialize array using array notation */

   for (i = 0 ; i <= TOP ; i++) { /* BIG MISTAKE */
      ptr1[i] = i*i ;
   }

   printf("Everything is fine up to now, or is it?\n") ;

   /* Get memory for an array using calloc */

   printf("Calling calloc()...\n") ;
   ptr2 = (double *) calloc(TOP, sizeof(double)) ;
   printf("... return from calloc().\n") ;

   if (ptr2 == NULL) {
      fprintf(stderr, "calloc() failed!\n") ;
      exit(1) ;
   }

   /* Initialize array using pointer arithmetic */

   ptr3 = ptr2 ;
   for (i = 0 ; i < TOP ; i++) {
      *(ptr3++)  = i*i ;
   }


   /* Print array contents */

   printf("Array pointed by ptr1:\n") ;
   for(i = 0 ; i < TOP ; i++) {
      printf("%3.0f ", ptr1[i]) ;
   }
   printf("\n\n") ;

   printf("Array pointed by ptr2:\n") ;
   for(i = 0 ; i < TOP ; i++) {
      printf("%3.0f ", ptr2[i]) ;
   }
   printf("\n\n") ;
}