Re: right() returns the whole string for the most negative n

Hi David,

Thanks for the review!

On Wed, Aug 26, 2026 at 8:55 PM David Rowley <dgrowleyml(at)gmail(dot)com> wrote:
>
> On Wed, 26 Aug 2026 at 00:33, Daniel Gustafsson <daniel(at)yesql(dot)se> wrote:
> >
> > > On 25 Aug 2026, at 14:18, Dagfinn Ilmari Mannsåker <ilmari(at)ilmari(dot)org> wrote:
> > >
> > > Instead of open-coding this, how about about using pg_neg_s32_overflow?
> > >
> > > if (pg_neg_s32_overflow(n, &n))
> > > n = PG_INT32_MAX;
> >
> > Yes, that's indeed a good idea.
>
> I do see a few places where we do check for PG_INT32_MIN instead of
> using pg_neg_s32_overflow(). The example in [1] does end up with less
> code as a result of using pg_neg_s32_overflow(), so it might be worth
> removing all applicable examples that use the other method from master
> as a follow-up. It'd be worth verifying it doesn't make anything worse
> for build systems that don't have __builtin_sub_overflow().

I verified that converting them is safe on platforms without
__builtin_sub_overflow() -- there, pg_neg_s{16,32,64}_overflow() inline to
exactly the same "if (a == PG_INTnn_MIN) ...; *result = -a;" code that is
being replaced, so the generated code is unchanged (I confirmed the
fallback path is bit-for-bit equivalent to the manual form, including at
the INT_MIN boundary).

Rather than pile that cleanup onto this bug-fix thread, I'll send it as a
separate follow-up so this fix can be considered on its own. Will post
that shortly and CC you three.

>
> David
>
> [1] https://godbolt.org/z/sfxY847E4

--
Regards,
Ewan Young