[ocaml5-issue] Segfault on s390x in Effect test

[jmid]

After merging #381 to main I spotted a multicoretests-ci failure on s390x for 5.2+trunk
https://ocaml-multicoretests.ci.dev:8100/job/2023-08-17/073031-ci-ocluster-build-e8d54d#L1589

random seed: 97230569
generated error  fail  pass / total     time test name

[ ]     0     0     0     0 / 20000     0.0s Lin DSL ref int test with Effect
[ ]     0     0     0     0 / 20000     0.0s Lin DSL ref int test with Effect (generating)
[✓] 20000     0     0 20000 / 20000     0.4s Lin DSL ref int test with Effect

[ ]     0     0     0     0 / 20000     0.0s Lin DSL ref int64 test with Effect
[✓] 20000     0     0 20000 / 20000     0.4s Lin DSL ref int64 test with Effect

[ ]     0     0     0     0 / 20000     0.0s Lin DSL CList int test with Effect
[✓] 20000     0     0 20000 / 20000     0.4s Lin DSL CList int test with Effect

[ ]     0     0     0     0 / 20000     0.0s Lin DSL CList int64 test with Effect
[✓] 20000     0     0 20000 / 20000     0.5s Lin DSL CList int64 test with Effect

[ ]     0     0     0     0 / 20000     0.0s negative Lin DSL ref int test with EffectFile "src/neg_tests/dune", line 92, characters 7-27:
92 |  (name lin_tests_dsl_effect)
            ^^^^^^^^^^^^^^^^^^^^
(cd _build/default/src/neg_tests && ./lin_tests_dsl_effect.exe --verbose)
Command got signal SEGV.

After focusing and cleaning up I now have a reproducer in the https://github.com/ocaml-multicore/multicoretests/commits/s390x-crash-repro branch that consistently fails in the CI on both 5.1+trunk and 5.2+trunk.

I will open an OCaml issue for it shortly.

[jmid]

Reported upstream in ocaml/ocaml#12486

[jmid]

Closing as this was fixed and cherry-picked to 5.1.0~rc3 in ocaml/ocaml#12530