Years ago The Commander and Bart Locanthi used JIT
in the form of some C that write machine code into an
array of chars, cast it to a function pointer, and called it.
(I appologise if the details are not correct but this is the idea).

I have a need for such a thing again - trying to speed up
a compressed video decoder.

Anyone done such a thing this millenium? Does the x86 data execution
prevention mean you just cannot do this - my targets are desktop OSs
other than plan9 (sadly).

-Steve