EXTRA_STACK
int inuse = cast_int(L->top - L->stack) + EXTRA_STACK;
lua_assert(L->stack_last - L->stack == L->stacksize - EXTRA_STACK);
L->stack_last = L->stack + newsize - EXTRA_STACK;
int needed = cast_int(L->top - L->stack) + n + EXTRA_STACK;
int goodsize = inuse + (inuse / 8) + 2*EXTRA_STACK;
L1->stack_last = L1->stack + L1->stacksize - EXTRA_STACK;