Segmentation fault in the test suite under GHC 9.2.1

[Roman Cheplyaka]

I pushed the branch ghc-9.2.1, which builds inline-r with GHC 9.2.1.

The inline-r:test:tests test suite fails with

[nix-shell:~/HaskellR]$ ./inline-r/.stack-work/dist/x86_64-linux-nix/Cabal-3.6.0.0/build/tests/tests -j 1 -p events
Unit tests
  events
    addInputHandler increases handler count:    OK
    removeInputHandler decreases handler count: OK
    file events (select):                       Segmentation fault (core dumped)

Interestingly, if I run just that test, it passes:

[nix-shell:~/HaskellR]$ ./inline-r/.stack-work/dist/x86_64-linux-nix/Cabal-3.6.0.0/build/tests/tests -p 'file events'
Unit tests
  events
    file events (select): OK

So there must be some kind of interaction with the previous tests.

[Roman Cheplyaka]

Also reproduced on the CI:

https://github.com/tweag/HaskellR/runs/4762036549?check_suite_focus=true

Looks like it's the interaction with the addInputHandler test that causes this:

[nix-shell:~/HaskellR]$ ./inline-r/.stack-work/dist/x86_64-linux-nix/Cabal-3.6.0.0/build/tests/tests -p '/file events/ || /addInputHandler increases/'
Unit tests
  events
    addInputHandler increases handler count: OK
    file events (select):                    Segmentation fault (core dumped)

[Roman Cheplyaka]

I think what's going on here is that the addInputHandler test adds an input handler, then de-allocates the handler function (via freeHaskellFunPtr). Then at some point R decides to call that function, which leads to a segfault.