Re: Call CalculateShmemSize() only once

Hi Ashutosh,

Thanks for the patch. LGTM overall.

On Mon, Nov 2, 2026 at 6:12 PM Ashutosh Bapat
<ashutosh(dot)bapat(dot)oss(at)gmail(dot)com> wrote:

> > Should we ERROR if it is called more than once? That might need some
> > special handling for the restart_after_crash case.
> >
>
> With this change, a second call to ShmemGetRequestedSize() during the
> same shared-memory initialization cycle fails
> Assert(shmem_request_state == SRS_REQUESTING) in assertion-enabled
> builds. This also detects repeated calls through CalculateShmemSize().
> I think an assertion is sufficient here because this is an internal
> lifecycle invariant, consistent with the other state-transition
> assertions. Attempts to register requests after sizing are still
> rejected by the existing runtime checks.
>
> For restart_after_crash, ResetShmemAllocator() resets the state to
> SRS_INITIAL. The request callbacks then start a fresh request phase,
> allowing the size to be calculated again for the new segment.
>

Erroring out can help to stop the misake where it occurs. A build
without assert could accept the bad call, then fail later somewhere
else. It might make the problem a bit hard to understand. That said,
assert seems ok here since we haven't found code can make that bad
call.

A nit - the new state in code is SRS_SIZED, but the commit message
says SRS_SIZING.

--
Regards,
Xuneng Zhou
HighGo Software Co., Ltd.