size_t (*size)(struct _malloc_zone_t *zone, const void *ptr); /* returns the size of a block or 0 if not in this zone; must be fast, especially for negative answers */
void *(*malloc)(struct _malloc_zone_t *zone, size_t size);
void *(*calloc)(struct _malloc_zone_t *zone, size_t num_items, size_t size); /* same as malloc, but block returned is set to zero */
size_t (*size)(struct _malloc_zone_t *zone, const void *ptr); /* returns the size of a block or 0 if not in this zone; must be fast, especially for negative answers */
void *(*malloc)(struct _malloc_zone_t *zone, size_t size);
void *(*calloc)(struct _malloc_zone_t *zone, size_t num_items, size_t size); /* same as malloc, but block returned is set to zero */