Re: Why is parula failing?

On Mon, 15 Apr 2024 at 16:02, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> David Rowley <dgrowleyml(at)gmail(dot)com> writes:
> > If GetNowFloat() somehow was returning a negative number then we could
> > end up with a large delay. But if gettimeofday() was so badly broken
> > then wouldn't there be some evidence of this in the log timestamps on
> > failing runs?
>
> And indeed that too. I'm finding the "compiler bug" theory
> palatable. Robins mentioned having built the compiler from
> source, which theoretically should work, but maybe something
> went wrong? Or it's missing some important bug fix?
>
> It might be interesting to back the animal's CFLAGS down
> to -O0 and see if things get more stable.

The last 25 consecutive runs have passed [1] after switching
REL_12_STABLE to -O0 ! So I am wondering whether that confirms that
the compiler version is to blame, and while we're still here,
is there anything else I could try?

If not, by Sunday, I am considering switching parula to gcc v12 (or even
v14 experimental - given that massasauga [2] has been pretty stable since
its upgrade a few days back).

Reference:
1.
https://buildfarm.postgresql.org/cgi-bin/show_history.pl?nm=parula&br=REL_12_STABLE
2.
https://buildfarm.postgresql.org/cgi-bin/show_history.pl?nm=massasauga&br=REL_12_STABLE
-
robins