return 0;;
return 0;
map_pages(pages)    int pages;{    caddr_t result, tail;    result = (caddr_t)pageround((u_long)sbrk(0));    tail = result + (pages << malloc_pageshift);    if (brk(tail)) {#ifdef EXTRA_SANITY	wrterror("(ES): map_pages fails\n");#endif /* EXTRA_SANITY */	return 0;    }    last_index = ptr2index(tail) - 1;    malloc_brk = tail;    if ((last_index+1) >= malloc_ninfo && !extend_pgdir(last_index))	return 0;;    return result;}