I will leave it to Ben to expand on the timeline.
As for !10479 the decision to merge this in 9.14 has been made on 15th
of July.
Since 9.14 is going to be an LTS release, ultimately the choice was between:
* A increased workload for many backports over the next years by pushing
it to 9.16.
Accompanied by a further delay of resolving bugs related to
polymorphic specialisation.
* The risk of introducing bugs through landing it now and a potential
delay of 9.16
While bugs are always a risk, pushing it to 9.16 is unlikely to
meaningfully reduce the number of bugs landing
this will incur. In the end those bugs will need to be fixed, be that in
9.14.2 or 9.16.2.
It's not uncommon to identify *some* bugs in patches on master. However
with !10479 there
has been more testing than usual on the MR pre-merge. Including not just
head.hackage but also
other packages. Reducing the risk associated with this somewhat.
With 9.14 having a planned lifetime of potentially three years,
backporting through this change
would add up to a fairly high cost over time. Which is the main argument
for landing this patch in 9.14.
This was discussed in the GHC call and ultimately we came to the
conclusion that given the resources
available, and the state and nature of the patch landing it for 9.14 is
the preferable option.
Since then not much has changed. While pushing the MR back to 9.16 *now*
would be possible,
it's unclear this would change the release date meaningfully. After all
there are other unresolved blockers
for the first alpha for 9.14. It's also worth pointing out that most of
the delays on 9.14 had to do with toolchain issues
and were not related to this patch being included at all.
Should !10479 become the sole blocker for a number of days, or should a
large number of issues be discovered
that can be traced back to it during the alpha it would make sense to
reevaluate this decision. We have never
ruled out this option completely.
However today I still believe going forward with !10479 being included
in 9.14 is in the best interest of the GHC
project. Especially because it will reduce the cost of maintaining the
LTS branch going forward.
Cheers
Andreas
On 12/08/2025 13:27, Matthew Pickering wrote:
Hi,
Thanks for the update Ben. Can you clarify the timeline now?
It seems that there is a plan to merge !10479 into the 9.14 branch.
https://gitlab.haskell.org/ghc/ghc/-/merge_requests/10479
!10479 appears to be a very significant patch which touches many
sensitive areas of the compiler. I believe regressions will be
reported due to this patch.
It also will be merged two months after the merge deadline for the
branch and the release schedule seems to have already slipped
significantly.
Therefore, I believe it would be prudent to delay merging this one
until the 9.16 release so that regressions can be discovered and fixed
before it is released to users.
Cheers,
Matt
On Tue, Aug 12, 2025 at 12:25 PM Andreas Klebinger via ghc-devs
<[email protected]> wrote:
I'm merely forwarding this from ghc-releases for those not following there:
Hi all,
A brief update on the GHC 9.14 release status. As noted last time, the
release process has been held up by a few significant bodies of on-going
work:
- the upgrade of the Windows toolchain which has revealed a number of
linking issues,
- enabling support for LLVM 20 (#26267), along with the resolution of
a few correctness issues which were uncovered in the process (#26109)
- the resolution to #23109, a rather invasive correctness fix which we
want to ensure is adequately tested prior to the release,
At this point we have resolved, or are close to resolving, all of these
issues. We expect that #23109 will land today, with the resolution to
#26109 hopefully landing shortly thereafter.
One wrinkle here is a late request for a boot library bump (#26268)
which has had a number of knock-on effects. We are still trying to
land this in `master`; we tentatively plan to backport but given how
the state of the release process we will not delay the release if things
do not go smoothly.
Once the above has happened we will backport to `ghc-9.14` and begin
preparation of the first alpha release. This may happen as soon as
Thursday.
Cheers,
- Ben
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