Re: Acceptable indicies

[liam mail <liam.list@...>]

On 31 August 2011 14:56, liam mail <liam.list@googlemail.com> wrote:
> On 31 August 2011 14:21, Luiz Henrique de Figueiredo
> <lhf@tecgraf.puc-rio.br> wrote:
>>> But how do you validate, say, an index you give to a C function that
>>> queries the Lua stack?
>>
>> Use lua_type. The manual says that it returns LUA_TNONE for a non-valid index.
>>
>>
> Only a non valid acceptable index, a non valid non acceptable index is
> undefined and there is no way to determine if an index is non valid
> non acceptable.
>
> Liam
>

What I should really say is an non acceptable index which is greater
than the stackspace plus extra space plus 1 (end of an array can be
used to compare an index inside the array) is undefined, this is due
to index2adr if I understand correctly. For example using index 30
when stackspace is 20 and extraspace is 5* then the following is UB in
C.
if (o >= L->top)

* numbers pulled out of the air.