volatile semantics

[Paul Schlie]

> Geoffrey Keating writes:
>
> int i;

- merely means: allocate and treat all references to the object as
  referencing an unqualified int object, unless re-qualified within a
  more local scope.

> without 'volatile', then this object cannot be modified unknown to the
> implementation, even if someone also writes '(*(volatile int *)&i) = 1'.

- merely means: treat the object being referenced as volatile qualified int
  object (as the standard specifies, although it may result in an undefined
  behavior, nothing more or less; as although the object may have not been
  initially declared as being volatile, the program within the context of
  this particular references has asserted that it must be treated as such,
  thereby implying it's value must be assigned, and/or presumed to have been
  possibly modified beyond the logical view of the program).

  const, volatile, and restrict are all logically equivalent in this
  regard; regardless of whether or not an object was declared as being
  originally qualified, or subsequently declared as being so within the more
  restricted scope of a function via it's parameter declaration, or single
  reference via a qualified cast.  Where although inconsistent references to
  any single object may result in an undefined behavior, it should be clear
  there's no value in attempting to rationalize any more creative less
  consistent interpretation, as it will be no more correct, and only likely
  unnecessarily complicating to both the implementation and programmer.