ra
  pcre_jit_callback  callback
  void               *data
</pre>
The <i>extra</i> argument must be the result of studying a pattern with
PCRE_STUDY_JIT_COMPILE etc. There are three cases for the values of the other
two options:
<pre>
  (1) If <i>callback</i> is NULL and <i>data</i> is NULL, an internal 32K block
      on the machine stack is used.

  (2) If <i>callback</i> is NULL and <i>data</i> is not NULL, <i>data</i> must be
      a valid JIT stack, the result of calling <b>pcre_jit_stack_alloc()</b>.