whether JIT was actually used for a
particular match, you should arrange for a JIT callback function to be set up
as described in the section entitled
<a href="#stackcontrol">"Controlling the JIT stack"</a>
below, even if you do not need to supply a non-default JIT stack. Such a
callback function is called whenever JIT code is about to be obeyed. If the
execution options are not right for JIT execution, the callback function is not
obeyed.
</P>
<P>
If the JIT compiler finds an unsupported item, no JIT data 