Integer overflow and underflow semantics

[Alex Rønne Petersen]

On 05-05-2012 13:06, bearophile wrote:
> Alex Rønne Petersen:
>
>> I don't think the language really makes it clear whether overflows and
>> underflows are well-defined. Do we guarantee that for any integral
>> type T, T.max + 1 == T.min and T.min - 1 == T.max?
>>
>> This is relevant in particular for GDC and LDC since they target a lot
>> of weird architectures.
>
> In a good system language I'd like to see something better than what's
> present in C#. So I'd like the language to offer the programmer the
> choice of 3 or 4 different semantics in integral operations:
>
> 1) A shared standard semantics that overflows, as in Java;
> 2) A semantics that overflows, that adapts to the fastest available on
> the CPU, as in C;
> 3) Shared standard overflows with unsigned values and run-time errors
> when a signed value overflows (or goes out of its range).
> 4) Run-time errors when every signed or unsigned value overflows (or
> goes out of its range), as in Ada.
>
> Bye,
> bearophile

Good point. The wrapping rule described in my OP should be the default 
IMO. Then perhaps the other modes could be activated with an @attribute 
of sorts?

-- 
- Alex