rem: return (char *) memcpy (new, s, len);
add: return memcpy (new, s, len);
context: __strndup (const char *s, size_t n){  size_t len = strnlen (s, n);  char *new = malloc (len + 1);  if (new == NULL)    return NULL;  new[len] = '\0';  return (char *) memcpy (new, s, len);}