Re: An unsigned overflow in luai_makeseed()

AFAIK unsigned overflow is and always was defined in both C and C++ to just
be modulo arithmetics.

On Tue, 17 Feb 2026 at 10:50, 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
>
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