Re: An unsigned overflow in luai_makeseed()

AFAIK it's the signed overflow that is considered UB, and unsigned
operations are defined with modular arithmetic, no?

On Tue, Feb 17, 2026, 11:50 Sergey Bronnikov <[email protected]> wrote:

> Hello,
>
> the function luai_makeseed() in lauxlib.c has the following expression [1]:
>
> res ^= (res >> 3) + (res << 7) + buff[i];
>
> where res has type "unsigned integer". This arithmetic has an unsigned
> overflow.
> This is of course undefined behavior from a language point of view, but
> maybe it is used here intentionally?
>
> 1.
> https://github.com/lua/lua/blob/c6b484823806e08e1756b1a6066a3ace6f080fae/lauxlib.c#L1167
>
> Sergey
>
> --
> You received this message because you are subscribed to the Google Groups
> "lua-l" group.
> To unsubscribe from this group and stop receiving emails from it, send an
> email to [email protected].
> To view this discussion visit
> https://groups.google.com/d/msgid/lua-l/c36ec376-99a3-4869-9881-46eb9dde1a6cn%40googlegroups.com
> <https://groups.google.com/d/msgid/lua-l/c36ec376-99a3-4869-9881-46eb9dde1a6cn%40googlegroups.com?utm_medium=email&utm_source=footer>
> .
>

-- 
You received this message because you are subscribed to the Google Groups "lua-l" group.
To unsubscribe from this group and stop receiving emails from it, send an email to [email protected].
To view this discussion visit https://groups.google.com/d/msgid/lua-l/CAKmTuAKUWPd-maRYyVF1ZvkHM_jm9FtA1%2BwbyC-BVdZCTYSPDQ%40mail.gmail.com.