memset_ptr is a const (we can't change its value) volatile (its value might change on its own) pointer to a function which taking three arguments (void * , int,

memset_ptr is a const (we can't change its value) volatile (its value might change on its own) pointer to a function which taking three arguments (void * , int, size_t) and returning void *; and the memset_ptr symbol does not have external linkage and is initialized to "memset".