UTop exits reporting an exception after requiring core

[janilcgarcia]

Whenever I #require "core";; (core from JaneStreet) during a UTop session, I receive the following report on a #quit;;:

Raised at Topdirs.dir_quit in file "toplevel/topdirs.ml", line 66, characters 18-52
Called from Topcommon.try_run_directive in file "toplevel/topcommon.ml", line 335, characters 34-38
Called from Topeval.execute_phrase in file "toplevel/byte/topeval.ml", line 177, characters 6-42
Re-raised at Topeval.execute_phrase in file "toplevel/byte/topeval.ml", line 180, characters 4-13
Called from UTop_main.execute_phrase.(fun) in file "src/lib/uTop_main.ml", line 762, characters 14-48
Called from UTop_main.loop in file "src/lib/uTop_main.ml", line 852, characters 18-49
Re-raised at Location.report_exception.loop in file "parsing/location.ml", line 938, characters 14-25
Called from UTop.get_message in file "src/lib/uTop.ml", line 129, characters 2-11
Called from UTop_main.loop in file "src/lib/uTop_main.ml", line 871, characters 21-61
Called from UTop_main.main_aux in file "src/lib/uTop_main.ml", line 1630, characters 8-17
Called from UTop_main.main_internal in file "src/lib/uTop_main.ml", line 1646, characters 4-25

I doesn't actually cause any issue, but its annoying and it may be hiding some more troubling issue. I was not sure whether I should report the issue here or on JaneStreet's repo.

I'm using opam + ocaml 4.14.0. Here are the package versions:

astring                     0.8.5
base                        v0.15.0
base-bigarray               base
base-bytes                  base
base-threads                base
base-unix                   base
base_bigstring              v0.15.0
base_quickcheck             v0.15.0
bin_prot                    v0.15.0
camlp-streams               5.0.1
cmdliner                    1.1.1
core                        v0.15.0
core_bench                  v0.15.0
core_kernel                 v0.15.0
core_unix                   v0.15.0
cppo                        1.6.9
csexp                       1.5.1
dot-merlin-reader           4.6
dune                        3.4.1
dune-build-info             3.4.1
dune-configurator           3.4.1
either                      1.0.0
expect_test_helpers_core    v0.15.0
fieldslib                   v0.15.0
fix                         20220121
fpath                       0.7.3
int_repr                    v0.15.0
jane-street-headers         v0.15.0
jst-config                  v0.15.1
lambda-term                 3.3.1
logs                        0.7.0
lwt                         5.6.1
lwt_react                   1.2.0
menhir                      20220210
menhirLib                   20220210
menhirSdk                   20220210
merlin                      4.6-414
merlin-lib                  4.6-414
mew                         0.1.0
mew_vi                      0.5.0
num                         1.4
ocaml                       4.14.0
ocaml-base-compiler         4.14.0
ocaml-compiler-libs         v0.12.4
ocaml-config                2
ocaml-options-vanilla       1
ocaml-version               3.5.0
ocaml_intrinsics            v0.15.2
ocamlbuild                  0.14.1
ocamlfind                   1.9.5
ocamlformat                 0.24.1
ocp-indent                  1.8.1
ocplib-endian               1.2
odoc-parser                 2.0.0
parsexp                     v0.15.0
ppx_assert                  v0.15.0
ppx_base                    v0.15.0
ppx_bench                   v0.15.0
ppx_bin_prot                v0.15.0
ppx_cold                    v0.15.0
ppx_compare                 v0.15.0
ppx_custom_printf           v0.15.0
ppx_derivers                1.2.1
ppx_disable_unused_warnings v0.15.0
ppx_enumerate               v0.15.0
ppx_expect                  v0.15.0
ppx_fields_conv             v0.15.0
ppx_fixed_literal           v0.15.0
ppx_hash                    v0.15.0
ppx_here                    v0.15.0
ppx_ignore_instrumentation  v0.15.0
ppx_inline_test             v0.15.0
ppx_jane                    v0.15.0
ppx_let                     v0.15.0
ppx_log                     v0.15.0
ppx_module_timer            v0.15.0
ppx_optcomp                 v0.15.0
ppx_optional                v0.15.0
ppx_pipebang                v0.15.0
ppx_sexp_conv               v0.15.1
ppx_sexp_message            v0.15.0
ppx_sexp_value              v0.15.0
ppx_stable                  v0.15.0
ppx_string                  v0.15.0
ppx_typerep_conv            v0.15.0
ppx_variants_conv           v0.15.0
ppxlib                      0.27.0
re                          1.10.4
react                       1.2.2
result                      1.5
seq                         base
sexp_pretty                 v0.15.0
sexplib                     v0.15.1
sexplib0                    v0.15.1
spawn                       v0.15.1
splittable_random           v0.15.0
stdio                       v0.15.0
stdlib-shims                0.3.0
textutils                   v0.15.0
textutils_kernel            v0.15.0
time_now                    v0.15.0
timezone                    v0.15.0
topkg                       1.0.5
trie                        1.0.0
typerep                     v0.15.0
uchar                       0.0.2
utop                        2.10.0
uucp                        14.0.0
uuseg                       14.0.0
uutf                        1.0.3
variantslib                 v0.15.0
yojson                      2.0.1
zed                         3.2.0

[emillon]

This is because of Backtrace.initialize_module in base. The problem can be reduced, without core, to:

utop # Printexc.record_backtrace true;;
utop # #quit;;

This differs from the behavior of the ocaml toplevel, which exits directly.

I'm not sure what's the best fix is. We can probably exit directly in the Exit_with_status case below:

utop/src/lib/uTop_main.ml

Lines 1634 to 1651 in bbd9a6e

	let main_internal ~initial_env =
	let exit_status = ref 2 in
	try
	main_aux ~initial_env
	with exn ->
	(match exn with
	| Unix.Unix_error (error, func, "") ->
	Printf.eprintf "%s: %s: %s\n" app_name func (Unix.error_message error)
	| Unix.Unix_error (error, func, arg) ->
	Printf.eprintf "%s: %s(%S): %s\n" app_name func arg (Unix.error_message error)
	#if OCAML_VERSION >= (4,12,0)
	| Compenv.Exit_with_status e -> exit_status := e
	#endif
	| exn ->
	Printf.eprintf "Fatal error: exception %s\n" (Printexc.to_string exn));
	Printexc.print_backtrace stderr;
	flush stderr;
	exit !exit_status