Help with bit-field semantics in C and C++

[Mike Stump]

On Tuesday, August 24, 2004, at 03:02  PM, David Carlton wrote:
> I'm certainly not intending to be clever here.  I would say, actually,
> that I'm trying to be as naive as possible in my reading.

That is in general dangerous.

> I dunno.  I ran this example:
>
>   enum Small { Zero = 0, One = 1, Two = 2, Three = 3 };
>
>   Small x = (Small) 7;
>
>   switch ( x ) {
>     case Zero:
>       return zero();
>     case One:
>       return one();
>     case Two:
>       return two();
>     case Three:
>       return three();
>   }
>
> by a couple of people who walked by my cubicle, before showing them
> the standard.  Their first reaction is that they would expect the
> switch statement to fall through.

That doesn't surprise me.

> When I showed them the standard, they agreed that it wouldn't fall 
> through.

Then they misread the standard.  The conversion is unspecified, there 
is nothing that prohibits it from having the value 7 and from the 
switch statement from falling through.

> * Users would be disappointed if the above example were to, say, core
>   dump (which is behavior that is being proposed in some messages on
>   this thread).

Agreed.