Re: Is it ok to assume luaL_ref() won't return 0 ?

[Rena <hyperhacker@...>]

On Aug 5, 2016 10:09 AM, "书呆彭, Peng Yi" <nerditation@outlook.com> wrote:
>
> 在 2016/8/5 19:22, Niccolo Medici 写道:
>>
>> Let's say I have a C 'int' variable that holds a reference (what
>> luaL_ref() returns). At the start of the program it's initialized to
>> zero. Can I assume that zero means that it doesn't hold a reference,
>> or must I explicitly initialize it to LUA_NOREF (which happens to be
>> -2) ?
>>
>> (It's not that I'm being lazy. In reality I have several huge arrays
>> of references (allocated and zero'ed with calloc()), not just one
>> variable, and I want to skip the loops that are to initialize them.)
>>
>> A bonus question: if it's ok to assume luaL_ref() won't return 0, then
>> why does LUA_NOREF equal -2 instead of simply being 0 ?
>>
>
> the manual says:
>
>     A reference is a unique integer key.
>     As long as you do not manually add integer keys into table t, luaL_ref ensures the uniqueness of the key it returns.
>     The constant LUA_NOREF is guaranteed to be different from any reference returned by luaL_ref.
>
>
> all luaL_ref can guarantee is the uniqueness. current implementation use only positive integer keys.
>
> Lua 5.3 use index 0 as a special key to keep track the unref-ed slots as a linked free list.
>
> but it should be considered as implementation detail I think.
>
>
> --
> the nerdy Peng / 书呆彭 / Sent from Thunderbird
>
>
>

But isn't LUA_NOREF == 0?