ocaml 4.02.3: internal error raised from Exn.Code_error

[avsm]

In the ctypes build of the dune port, 4.02.3 is specifically raising some internal errors in dune that aren't happening on later versions of the compiler. Sadly, 4.02.3 is still one of the support compiler versions so we need to worry about it :-)

See https://travis-ci.com/avsm/ocaml-ctypes/jobs/168302505 for a full run. The tree that is exhibiting the problem is in https://github.com/avsm/ocaml-ctypes/tree/dune-port and tracked as a PR in yallop/ocaml-ctypes#588

- /-----------------------------------------------------------------------
- | Internal error: Fiber.Execution_context.forward_error: error handler raised.
- | Stdune__Exn.Code_error(_)
- | Called from file "camlinternalLazy.ml", line 25, characters 17-27
- | Re-raised at file "camlinternalLazy.ml", line 32, characters 10-11
- | Called from file "src/errors.ml", line 77, characters 17-47
- | Called from file "format.ml", line 1175, characters 28-44
- | Called from file "src/stdune/option.ml", line 23, characters 14-17
- | Called from file "src/fiber/fiber.ml", line 243, characters 6-18
- | Called from file "src/fiber/fiber.ml", line 56, characters 6-20
- | 
- | Original exception was: Stdune__Exn.Code_error(_)
- | Called from file "camlinternalLazy.ml", line 25, characters 17-27
- | Re-raised at file "camlinternalLazy.ml", line 32, characters 10-11
- | Called from file "src/errors.ml", line 77, characters 17-47
- | Called from file "format.ml", line 1175, characters 28-44
- | Called from file "src/stdune/option.ml", line 23, characters 14-17
- | Called from file "src/fiber/fiber.ml", line 243, characters 6-18
- \-----------------------------------------------------------------------

[rgrinberg]

Sadly, this seems to be a sandboxing issue that I can't reproduce on OSX. What's even more strange that I couldn't reproduce it in one of your docker images either (with pinning). I'll see if I can produce a branch that will improve the error messages in this case.

[rgrinberg]

@avsm would you mind running this again against #1739 ?

This should give us a better error message. Sorry for the trouble, but I can't reproduce locally.

[avsm]

Hm this is with the pin now successfully in place, but no more extra output as far as I can tell https://travis-ci.org/ocamllabs/ocaml-ctypes/jobs/476067840#L657

Maybe the exception printer is raising? Exceptions raised by exception printers are silently ignored by Printexc.to_string.

[rgrinberg]

Okay, I think I found the error. Will post a fix shortly.

[avsm]

Hm, I still see the same error with a pin to latest dune master:
https://travis-ci.org/ocamllabs/ocaml-ctypes/jobs/476974038

- /-----------------------------------------------------------------------
- | Internal error: Fiber.Execution_context.forward_error: error handler raised.
- | Stdune__Exn.Code_error(_)
- | Called from file "camlinternalLazy.ml", line 25, characters 17-27
- | Re-raised at file "camlinternalLazy.ml", line 32, characters 10-11
- | Called from file "src/errors.ml", line 77, characters 17-47
- | Called from file "format.ml", line 1175, characters 28-44
- | Called from file "src/stdune/option.ml", line 23, characters 14-17
- | Called from file "src/fiber/fiber.ml", line 56, characters 6-20
- | 
- | Original exception was: Stdune__Exn.Code_error(_)
- | Called from file "camlinternalLazy.ml", line 25, characters 17-27
- | Re-raised at file "camlinternalLazy.ml", line 32, characters 10-11
- | Called from file "src/errors.ml", line 77, characters 17-47
- | Called from file "format.ml", line 1175, characters 28-44
- | Called from file "src/stdune/option.ml", line 23, characters 14-17
- | Called from file "src/fiber/fiber.ml", line 243, characters 6-18
- \-----------------------------------------------------------------------

[avsm]

I just noticed that it seems to happen in dune subst, not dune build

[rgrinberg]

You probably forgot to update things. Line 77 in errors.ml doesn't exist anymore.

[avsm]

Argh, it's because opam pin -n with a pin depends doesn't actually install the updated dune without an opam upgrade. Sorry...