Re: Recent failures on buildfarm member hornet

I wrote:
> I'm tempted to propose the attached small code rearrangement, which
> might dissuade the compiler from thinking it can get away with this.
> While I concur with your point that an old xlc version might not be
> that exciting, there could be other compilers doing the same thing
> in the future.

After thinking about it a bit more, I'm not even convinced that what
xlc seems to be doing is illegal per C spec. There are no sequence
points within

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

and therefore there's an argument to be made that the compiler
doesn't have to care whether any side-effects of list_concat() occur
before or after the evaluation of makeInteger(ndirectargs).
If the potential side-effects of list_concat() can be disregarded
until the end of this statement, then the code change is perfectly legal.

Maybe some very careful language-lawyering could prove differently,
but it's not as open-and-shut as one could wish. So now I'm thinking
that we need this patch anyway, xlc or not.

regards, tom lane