(closure).
</p>
<p>
This can happen implicitly due to the usual conversions, e.g. when
passing a Lua function to a function pointer argument. Or you can use
<tt>ffi.cast()</tt> to explicitly cast a Lua function to a
C&nbsp;function pointer.
</p>
<p>
Currently only certain C&nbsp;function types can be used as callback
functions. Neither C&nbsp;vararg functions nor functions with
pass-by-value aggregate argument or result types are supported. There
are no restrictions for the kind of Lua functions that can be