XXXX all calloc() implementations should check overflow

*** 205,219 ****
  
  void *
  calloc(size_t num, size_t size)
  {
          void *  mp;
  
!         num *= size;
!         if ((mp = malloc(num)) == NULL)
                  return (NULL);
!         (void) memset(mp, 0, num);
          return (mp);
  }
  
  void *
  realloc(void *ptr, size_t size)
--- 205,231 ----
  
  void *
  calloc(size_t num, size_t size)
  {
          void *  mp;
+         size_t  total;
  
!         if (num == 0 || size == 0) {
!                 total = 0;
!         } else {
!                 total = num * size;
! 
!                 /* check for overflow */
!                 if (total / num != size) {
!                         errno = ENOMEM;
                          return (NULL);
!                 }
!         }
! 
!         if ((mp = malloc(total)) == NULL)
!                 return (NULL);
!         (void) memset(mp, 0, total);
          return (mp);
  }
  
  void *
  realloc(void *ptr, size_t size)