[m-rev.] for post-commit review: Upgrade Boehm GC to v7.6.12 and libatomic_ops to v7.6.8

[Peter Wang]

On Thu, 2 Apr 2020 16:36:10 +1100 (AEDT), Julien Fischer <jfischer at opturion.com> wrote:
> 
> Hi Peter,
> 
> On Thu, 2 Apr 2020, Peter Wang wrote:
> 
> > boehm_gc:
> >    Update boehm_gc submodule to release-7_6-mercury-20190402.
> >
> > NEWS:
> >    Announce change.
> >
> > diff --git a/NEWS b/NEWS
> > index 00865c7bb..4d2ba06e1 100644
> > --- a/NEWS
> > +++ b/NEWS
> > @@ -244,6 +244,8 @@ Changes to the Mercury implementation
> >   Another consequence is that the `--trail-size` and `--trail-size-kwords`
> >   runtime options no longer have any effect, and are deprecated.
> > 
> > +* We have upgraded the bundled Boehm GC to v7.6.12 and libatomic_ops to v7.6.8.
> 
> If the upgrade fixes any specific issues with Mercury you should list
> them here as well.

There's a few changes that might be interesting but nothing that I've
specifically hit.

v7.6.14 looks to have some interesting fixes for Windows. I was
originally intending to upgrade to that, but it hasn't been marked as
released yet so I thought it better to wait.

The reason I was looking through the GC changes is because we (yeslogic)
are seeing some weird crashes on Windows on Travis CI, that we haven't
been able to reproduce elsewhere. A rare GC bug might explain it, or it
could be something else.

> 
> As I recall, there's some git submodule magic required to update
> existing workspaces.  Could you please remind us (well, me at least!)
> what that is?

This should do it:  git submodule update --recursive

Peter