Re: Recent failures on buildfarm member hornet

On Mon, Oct 05, 2020 at 08:42:15PM -0400, Tom Lane wrote:
> hornet has failed its last five runs with
>
> 2020-10-05 22:45:42.784 UTC [34734498:40] pg_regress/create_aggregate LOG: statement: create aggregate my_percentile_disc(float8 ORDER BY anyelement) (
> stype = internal,
> sfunc = ordered_set_transition,
> finalfunc = percentile_disc_final,
> finalfunc_extra = true,
> finalfunc_modify = read_write
> );
> TRAP: FailedAssertion("variadicArgType != InvalidOid", File: "pg_aggregate.c", Line: 216, PID: 34734498)
>
> After looking at the commits immediately preceding the first failure, and
> digging around in the aggregate-related code, it seems like commit
> cc99baa43 (Improve pg_list.h's linitial(), lsecond() and co macros)
> must've broke it somehow. The nearest thing that I can see to a theory
> is that where DefineAggregate does
> numDirectArgs = intVal(lsecond(args));
> it's coming out with the wrong result, leading to a failure of the
> numDirectArgs-vs-numArgs sanity check in AggregateCreate.

Building the tree with -O0 suppresses the problem. (xlc does not have -O1.)
Building just aggregatecmds.c and pg_aggregate.c that way does not, so I
suppose the damage arose elsewhere.

> But how could
> that be? I hesitate to blame the compiler twice in one week. OTOH, it's
> a not-very-mainstream compiler on a not-very-mainstream architecture.

A compiler bug is plausible. The compiler is eight years old, and we're not
seeing the problem on 32-bit (mandrill) or on 2019-vintage xlc (hoverfly).
Shall I make this animal use -O0 on v14+?