Barry Schwarz wrote:
> On Wed, 17 Oct 2007 13:35:44 GMT, "James Kuyper Jr."
> <jameskuyper@verizon.net> wrote:
>
> >Barry Schwarz wrote:
> >> On Sun, 14 Oct 2007 12:44:02 +0000 (UTC), $)CHarald van D )& k
> >> <truedfx@gmail.com> wrote:
> >...
> >>> Undefined behaviour is inherently implementation dependent.
> >>>
> >> Implementation dependent implies that the behavior will be consistent
> >> on a particular implementation (the same today as it was yesterday).
> >
> >Citation, please?
> >
> >"Implementation-dependent behavior" isn't a term defined in the C
> >standard. It's normal English meaning is only that the behavior depends
> >upon which implementation you use, which is certainly true for undefined
> >behavior. I don't see any implication that the behavior has to be
> >consistent.
>
> If the behavior is implementation-dependent (I agree with your normal
> meaning), and if the implementation doesn't changed, it is reasonable
> to conclude that the behavior won't either. If it does, then it
> depends on something other (or something more) than the
> implementation. Undefined behavior offers no such assurances.

To say that something depends upon one thing is not the same as saying
that it depends only upon that thing.

If, with implementation A, the behavior depends upon the day of the
week, and with implementation B the behavior depends upon whether or
not the current month has an 'r' in it, then the behavior is
implementation dependent, even though knowing which implementation
you're using is not sufficient to determine what the behavior actually
is. The behavior is also, in both cases, time dependent, which does
not conflict with the fact that it is also implementation-dependent.