Re: Can lua_next() error?

["Soni \"They/Them\" L." <fakedme@...>]

On 2018-04-16 01:49 PM, Viacheslav Usov wrote:
> On Mon, Apr 16, 2018 at 6:04 PM, Roberto Ierusalimschy 
> <roberto@inf.puc-rio.br <mailto:roberto@inf.puc-rio.br>> wrote:
>
> > Practically all functions in the Lua-C API can crash, when called 
> with invalid arguments.
>
> In the referenced thread, the C-language arguments given to the 
> function were not invalid. It was the content of the Lua stack that 
> was problematic for that function.

As far as the Lua C API is concerned, stack values are function 
arguments. How else would you pass tables to functions? They don't exist 
outside the Lua state.

> In the "checking for safety" context, that means the stack's content 
> should be validated, if it is accepted from another party.
>
> > I believe this happens with most C libraries.
>
> No, not really. It is one thing if a parameter in a C function is a 
> pointer, then the argument simply has to point to a valid memory 
> location. It is quite another when it is a kind of a "handle", then it 
> is rather typical for a function to return an error result if the 
> argument has an invalid or unsuitable value. See POSIX/read(), for 
> example. Lua's stack indices look more like handles than pointers to 
> me, but that, of course, can be just me.
>
> Cheers,
> V.

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