Re: Non-decimal integer literals

On Tue, 29 Nov 2022 at 23:11, Dean Rasheed <dean(dot)a(dot)rasheed(at)gmail(dot)com> wrote:
>
> On Wed, 23 Nov 2022 at 08:56, David Rowley <dgrowleyml(at)gmail(dot)com> wrote:
> >
> > On Wed, 23 Nov 2022 at 21:54, David Rowley <dgrowleyml(at)gmail(dot)com> wrote:
> > > I wonder if you'd be better off with something like:
> > >
> > > while (*ptr && isxdigit((unsigned char) *ptr))
> > > {
> > > if (unlikely(tmp & UINT64CONST(0xF000000000000000)))
> > > goto out_of_range;
> > >
> > > tmp = (tmp << 4) | hexlookup[(unsigned char) *ptr++];
> > > }
> >
> > Here's a delta diff with it changed to work that way.
> >
>
> This isn't correct, because those functions are meant to accumulate a
> negative number in "tmp".

Looks like I didn't quite look at that code closely enough.

To make that work we could just form the non-decimal versions in an
unsigned integer of the given size and then check if that's become
greater than -PG_INTXX_MIN after the loop. We'd then just need to
convert it back to its negative form.

i.e:

uint64 tmp2 = 0;
ptr += 2;
while (*ptr && isxdigit((unsigned char) *ptr))
{
if (unlikely(tmp2 & UINT64CONST(0xF000000000000000)))
goto out_of_range;

tmp2 = (tmp2 << 4) | hexlookup[(unsigned char) *ptr++];
}

if (tmp2 > -PG_INT64_MIN)
goto out_of_range;
tmp = -((int64) tmp2);

David