Re: [LuaJIT ffi] Misleading error message?

[Mike Pall <mikelu-1107@...>]

Thomas Lauer wrote:
> At any rate, I think being able to compare any value against nil
> without having the comparison itself trigger an error to be an
> important feature.

The FFI data types are strictly typed and behave accordingly. In
fact, it's just a convenience that you can compare them with other
Lua object types at all. Otherwise all such comparisons would
return false.

That however implies implicit conversions, e.g. '1LL == 1' is
really '1LL == ffi.cast("int64_t", 1)'. As with all implicit
conversions one has to be very careful and very conservative (or
you end up with something like PHP). That's why 'nil' is turned
into 'ffi.cast("void *", 0)' and only compares to pointer-like
objects and nothing else.

If you really, really need to find out whether something is a nil
object without ever raising errors, then use 'type(v) == "nil"'.

--Mike