Re: Fix compilation failure against LLVM 11

Hi Andres,
On the mensiversary of the last response, what can I do to help move
this along (aside from heeding the advice "don't use LLVM HEAD")?

Michael Paquier expressed concerns over flippant churn upthread:

On Mon, Apr 27, 2020 at 10:19 PM Andres Freund wrote:
AF> On 2020-04-28 13:56:23 +0900, Michael Paquier wrote:
MP> > On Mon, Apr 27, 2020 at 07:48:54AM -0700, Jesse Zhang wrote:
JZ> > > Are you expressing a concern against "churning" this part of the
JZ> > > code in reaction to upstream LLVM changes? I'd agree with you in
JZ> > > general. But then the question we need to ask is "will we need
JZ> > > to revert this 3 weeks from now if upstream reverts their
JZ> > > changes?", or "we change X to Y now, will we need to instead
JZ> > > change X to Z 3 weeks later?".
> >
MP> > My concerns are a mix of all that, because we may finish by doing
MP> > the same verification work multiple times instead of fixing all
MP> > existing issues at once. A good thing is that we may be able to
MP> > conclude rather soon, it looks like LLVM releases a new major
MP> > version every 3 months or so.
>
AF> Given the low cost of a change like this, and the fact that we have
AF> a buildfarm animal building recent trunk versions of llvm, I think
AF> it's better to just backpatch now.

For bystanders: Andres and I seemed to agree that this is unlikely to be
flippant (in addition to other benefits mentioned below). We haven't
discussed more on this, though I'm uncertain we had a consensus.

>
JZ> > > In that frame of mind, the answer is simply "no" w.r.t this
JZ> > > patch: it's removing an #include that simply has been dead: the
JZ> > > upstream change merely exposed it.
> >
MP> > The docs claim support for LLVM down to 3.9. Are versions older
MP> > than 8 fine with your proposed change?
>
AF> I'll check.
>

How goes the checking? I was 99% certain it'd work but that might have
been my excuse to be lazy. Do you need help on this?

>
JZ> > > OTOH, is your concern more around "how many more dead #include
JZ> > > will LLVM 11 reveal before September?", I'm open to suggestions.
JZ> > > I personally have a bias to keep things working.
> >
MP> > This position can have advantages, though it seems to me that we
MP> > should still wait to see if there are more issues popping up.
>
AF> What's the benefit? The cost of checking this will be not
AF> meaningfully lower if there's other things to check as well, given
AF> their backward compat story presumably is different.

For bystanders: Andres and I argued for "fixing this sooner and
backpatch" and Michael suggested "wait longer and whack all moles". We
have waited, and there seems to be only one mole (finding all dead
unbroken "include"s was left as an exercise for the reader). Have we
come to an agreement on this?

Cheers,
Jesse