While hacking CI tests for domainslib I discovered a test that would trigger an assertion failure under the debug runtime on ARM32 only. I've confirmed locally on a Raspberry Pi 2 with both 5.0.0 and 5.1.0~alpha1.

To recreate:

• fork https://github.com/jmid/domainslib/tree/lu-decomposition-abort
• opam install domain-local-await lockfree
• dune exec test/LU_decomposition_multicore.exe

Done: 38% (17/44, 27 left) (jobs: 0)### OCaml runtime: debug mode ###
[00] file runtime/fiber.c; line 182 ### Assertion failed: Stack_high(stack) - Stack_base(stack) == wosize || Stack_high(stack) - Stack_base(stack) == wosize + 1
Aborted

I am now building an opam switch for 5.1.0+trunk (which follows the ocaml/ocaml 5.1 branch) after yesterday's many cherry picks, to see whether any of them should fix it. I'll share the results here once it is ready (it is slow... 😅)