Q:  I have a unit that does a callback function (from a DLL).  In this unit, I have declared a global variable.  When I do the callback, it is unable to 'see' the global variable.  Both functions are in the same unit.  Why is this and what do I do?

A:  Turn off smart callbacks and add this:

{$K-}

Because of how things are being passed to the CPU (register manipulation) the scope has changed through a callback.