Re: GetBufferDescriptor() being called for local buffers from MarkBufferDirtyHint()

Hi,

On Thu, 11 Jun 2026 at 03:44, Michael Paquier <michael(at)paquier(dot)xyz> wrote:

> On Wed, Jun 10, 2026 at 10:36:22AM -0400, Andres Freund wrote:
> > I think it *should* blow up. It doesn't because we're lacking assertions
> in
> > GetBufferDescriptor(). But I don't think the assertions added in the
> patch are
> > quite right.
> >
> > We can't trivially add the correct assertions, because somebody though
> it was
> > a good idea to give GetBufferDescriptor() a uint32 parameter, which seems
> > completely wrong to me.
>
> This one is not as old as I expected: 3ac88fddd92c. You're right that
> switching that to be signed would be a correct first step forward.
>

Given the discussion here, I tried making the buffer descriptor accessors
take
a signed index and adding range assertions.

Most callers already pass signed buffer indexes derived from Buffer values
(e.g. buffer - 1, or -buffer - 1 for local buffers). The only caller I
found
that passes an unsigned value to GetBufferDescriptor() is ClockSweepTick(),
and
that normalizes the value before returning it, so it should still be less
than
NBuffers.

The change looked fairly straightforward to me, unless I'm missing
something.
I also made the same change for GetLocalBufferDescriptor(), since it has the
same uint32 signature and takes local buffer indexes.

Thoughts?

Regards,
Ayush