Integer overflow and underflow semantics

[bearophile]

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