User code must not modify the DispatcherContext field at any time.
DispatcherContext (DISPATCHERCONTEXT) - output A pointer to a reserved
field that receives state information on nested exceptions and collided
unwinds. This field returns information to either the exception
dispatcher (in the case of nested exceptions) or to the unwind routine
(in the case of collided unwinds). User code must not modify the
DispatcherContext field at any time.
When the system's exception handler is called (it is already registered
by the exception dispatcher), the exception handler returns NESTED and
fills in the DispatcherContext field with the address of the
EXCEPTIONREGISTRATIONRECORD corresponding to the exception handler most
recently called by the exception dispatcher. This indicates how far the
exception dispatcher progressed through the call chain before the
nesting occurred. The EH_NESTED_CALL bit is set in the
EXCEPTIONREPORTRECORD flags field for each exception handler that is
called between handler of the exception dispatcher and the establisher
of the most recently called handler.
In the case of a collided unwind, the exception handler registered by
the unwind dispatcher will return COLLIDED_UNWIND and the
DispatcherContext field will contain a pointer to the target frame of
the current unwind.
