Windows release quality

[Ben Gamari]

Phyx <lonetiger at gmail.com> writes:

> Hi Andreas,
>
> GHC 8.6.4 not supporting profiling libs was the first thing mentioned in
> the release email
>
>  - A regression resulting in segmentation faults on Windows introduced
>    by the fix for #16071 backported in 8.6.3. This fix has been reverted,
>    meaning that 8.6.4 is once again susceptible to #16071. #16071 will
>    be fixed in GHC 8.8.1.
>
> It was also stated that it would be back in 8.8.1. At this point there
> was no way to get profiling libs on 8.6.x without a major backport of
> linker changes from master. The choice was made to revert the change
> and release 8.6.4 without profiling libraries because of a stack
> allocation bug that was dormant for years but completely killed the 32
> bit distribution. That said the changelog linked to the wrong issue,
> the second two should have been #15934 but that's not hard to figure
> out by looking at the ticket.
>
I will reiterate that having functional profiling in 8.6.4 was never
in the cards (unless a contributor was willing to step up to backport
Phyx's linker patch).

However, I will also say that the fact that the omission of the
profiling libraries and haddock from the release tarball (#16408) was
not my intention. Rather this was an accidental side-effect of an
oversight in the release CI job. This is something I only realized
rather recently (leading to !516) and thought I would fix after when I
re-spun the Windows tarballs to include an i386 build.

In hindsight I should have advertised this more widely and perhaps even
pulled the bindist. However, in my defense I did not expect it to more
than a few days to get the fixes through CI and have a new set of
bindists ready for release. On the whole I agree that it is not fair to
users to expect them to discover this sort of thing by browsing the
issue tracker. This is something that I will improve on in the future.

In general I'm not sure how to handle signalling of release stability.
Tamar has done an absolutely amazing job keeping the Windows boat afloat
(and even improving it, c.f. his new IO manager), However, I cannot deny
that there are indeed issues, as evidenced by the fact that my patch
making Windows a mandatory-green CI platforms needs to disable quite a
number of flaky or failing tests. Should we be signalling that this is
stable? It's hard to say; many of these cases are rather niche. Needless
to say if there's consensus that this doesn't constitute a production
ready compiler then I will advocate adjusting the priorities of our
efforts at Well-Typed to put more weight on fixing the Windows issues.

Cheers,

- Ben

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