[ocaml5-issue] Gc.counters unsafe root registration

[jmid]

The Gc test in #469 triggered an issue with Gc.counters, which has recently been fixed on trunk: ocaml/ocaml#13370.
As a memory unsafety issue, this may result in segfaults, BUS error, or abort with Fatal error: allocation failure during minor GC on 5.2.0 or earlier versions.

For example, this 5.2 bytecode workflow yielded
https://github.com/ocaml-multicore/multicoretests/actions/runs/10612162062/job/29413248806

random seed: 160569551
generated error fail pass / total     time test name

[ ]    0    0    0    0 / 1000     0.0s STM Gc test sequential
[ ]    0    0    0    0 / 1000     0.0s STM Gc test sequential (generating)
[✓] 1000    0    0 1000 / 1000    48.0s STM Gc test sequential

[ ]    0    0    0    0 / 1000     0.0s STM Gc test parallel
Fatal error: allocation failure during minor GC
File "src/gc/dune", line 4, characters 7-16:
4 |  (name stm_tests)
           ^^^^^^^^^
(cd _build/default/src/gc && ./stm_tests.exe --verbose)
Command got signal ABRT.
[ ]  100    0    0  100 / 1000    12.6s STM Gc test parallel

[jmid]

Closing this as it is fixed in both 5.2.1, in the upcoming 5.3, and on trunk.