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- Subject: Re: Can lua_next() error?
- From: "Soni \"They/Them\" L." <fakedme@...>
- Date: Mon, 16 Apr 2018 20:51:12 -0300
On 2018-04-16 01:49 PM, Viacheslav Usov wrote:
On Mon, Apr 16, 2018 at 6:04 PM, Roberto Ierusalimschy
<email@example.com <mailto:firstname.lastname@example.org>> 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.
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