Re: [RFC] Mitigating unexpected arithmetic overflow

[Linus Torvalds]

On Thu, 9 May 2024 at 11:48, Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote:
>
> FWIW, the thing that somewhat worries me about having a helper along
> the lines of combine_to_u64(low, high) is that
>         foo->splat = combine_to_u64(something, something_else);
> would be inviting hard-to-catch brainos -
>         foo->splat = combine_to_u64(something_else, something);

Yeah, we'd have to be very clear about naming and ordering. So it
would probably have to be something like

        result = combine_to_u64_hi_lo(high, low);

to be easy to use.

The good news is that if you *do* get it wrong despite clear naming,
the resulting value will be so obviously wrong that it's generally a
"Duh!" thing if you do any testing what-so-ever.

Of course, I say that as somebody who always points out that I haven't
tested my own patches at all, and they are "something like this,
perhaps?".

But having "hi_lo" kind of naming would hopefully make it really
obvious even when just looking at the source code.

              Linus