[Haskell-cafe] Debugging a test suite freeze

David Feuer david.feuer at gmail.com
Thu Dec 1 04:15:47 UTC 2022

I don't see anything about test suites freezing/looping in that
ticket. Did you mean a different one? Note: it seems pretty clear that
my test suite is *not* looping: when it freezes, the process doesn't
burn CPU or memory. It seems there's a deadlock somewhere, but it's
all *extremely* mysterious to me. Most mysteriously, only the last
test case seems to lead to this problem, and it does so even when
*dramatically* simplified in various ways (e.g., if I just `liftIO
(print s)` instead of traversing with an arbitrary function, and then
finish off with `3 === 3`). It would be easy to believe that the
problem was in my Hedgehog test case generation code if not for the
fact that it works reliably on all versions of GHC from 7.8 through
9.2! So either something is wrong with GHC 9.4 or using 9.4 is getting
me a bad version of some dependency.

On Wed, Nov 30, 2022 at 10:36 PM Doug Burke <dburke.gw at gmail.com> wrote:
> I had a test suite loop indefinitely with ghc 9.4.3 - see
> https://gitlab.haskell.org/ghc/ghc/-/issues/22416 - but to be honest I
> don't really understand what the code did that lead to the problem, so
> dont know how relevant it is for you.
> Doug
> On Wed, Nov 30, 2022 at 5:46 PM David Feuer <david.feuer at gmail.com> wrote:
> >
> > In particular, I think tasty does some tricky concurrency. Have there been changes in that recently, either in GHC itself or in async, that might be responsible?
> >
> > On Wed, Nov 30, 2022, 5:33 PM David Feuer <david.feuer at gmail.com> wrote:
> >>
> >> The logict-sequence test suite consistently freezes up on the last
> >> test when compiled with GHC 9.4.3. logict-sequence and its test suite
> >> don't do anything special with that GHC/base version as far as I can
> >> see, or anything particularly strange in general, so I'm pretty
> >> confident the problem lies elsewhere. My best guesses are hedgehog,
> >> tasty, and tasty-hedgehog. Has anyone else run into weird issues with
> >> any/all of these on GHC 9.4.3?
> >>
> >> David
> >
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