Do CO++ signed types have modulo semantics?

[Paul Schlie]

> From: Daniel Berlin <dberlin@dberlin.org>
>> Overall, I guess I still simply believe the the first rule of optimization
>> is to preserve existing semantics unless explicitly authorized otherwise,
>> and then only if accompanied with corresponding warnings for all potentially
>> behavior altering assumptions applied.
> 
> It is, you just believe that semantics exist where they don't.

- Agreed, I do believe that an implementation should strive to define
  likely useful and consistent behaviors for those which the standard
  has defined as being undefined.

 As an implementation which chooses not define a specific behavior for one
 specified as being undefined, which it may, as an undefined behavior may
 invoke any behavior, then it remains undefined.  And may correspondingly
 yield an truly undefined resulting behavior if ever presumed to differ
 from the factual behavior which the compiler would otherwise produce;
 therefore of likely dubious value.