Re: Recent failures on buildfarm member hornet

Noah Misch <noah@leadboat.com> writes:
> On Tue, Oct 06, 2020 at 09:56:49PM -0400, Tom Lane wrote:
>> Now that *is* surprising.  Could you poke a little further to determine
>> which module is getting miscompiled?  (gram.o seems like the next most
>> likely bet.)

> gram.o was it.  (The way I rebuilt gram.o also rebuilt parser.o and scan.o,
> but those seem far less likely.)

This suggests that the problem is misoptimization of gram.y's
makeOrderedSetArgs:

    /* don't merge into the next line, as list_concat changes directargs */
    ndirectargs = list_length(directargs);

    return list_make2(list_concat(directargs, orderedargs),
                      makeInteger(ndirectargs));

I think that if the compiler did what the comment says not to, it'd match
this symptom.  However, I'm baffled as to why our recent pg_list.h changes
would've affected that.

            regards, tom lane