[OT] The Usual Arithmetic Confusions

[Dukc]

On Thursday, 3 February 2022 at 21:01:30 UTC, Ola Fosheim Grøstad 
wrote:
> On Thursday, 3 February 2022 at 20:56:04 UTC, Dukc wrote:
>> We could allow undefined behaviour only in `@system` code, and 
>> realistically,
>
> How exactly is this relevant for @safe?

We cannot allow undefined behaviour in `@safe` code. That means 
that any integer that would have undefined semantics for 
overflows could not be used at `@safe`.

Well, asserting no overflow would be fine. With a `-release` 
switch, it'd behave like the c++ signed int. But not otherwise. 
In fact this is already doable:

```D
import core.checkedint;
bool check;
auto x = mulu(a,b,check);
assert(!check);
```

Not sure if the compiler will take advantage of overflow being 
undefined behaviour here in release mode, though.