tt>union</tt> pointer</td></tr>
<tr class="even">
<td class="convin">Function cdata</td><td class="convop">take function address</td><td class="convout">Function pointer</td></tr>
<tr class="odd">
<td class="convin">Any other cdata</td><td class="convop">no conversion</td><td class="convout">C type</td></tr>
</table>
<p>
To pass a Lua object, other than a cdata object, as a specific type,
you need to override the conversion rules: create a temporary cdata
object with a constructor or a cast and initialize i