Add tentative support for OCaml 5.3

[cristianoc]

The cmt format has changed, this tries to support value dependencies just based on the type of what's available in the new Cmt_format.cmt_infos.

#202

[cristianoc]

This tentatively tries to extract the old cmt_value_dependencies.

[cristianoc]

The dependencies seems to have changed, currently none are found, and this attempt does not seem to work either:

let extractValueDependencies (cmt_infos : Cmt_format.cmt_infos) =
#if OCAML_VERSION >= (5, 3, 0)
  let deps = ref [] in
  let ident_occurrences = cmt_infos.cmt_ident_occurrences in
  Printf.eprintf "ident_occurrences: %d\n" (List.length ident_occurrences);
  let process_id ({Location.txt; loc}, res) = match res with
     | Shape_reduce.Resolved uid | Resolved_alias (uid, _) | Approximated (Some uid) ->
      (match Types.Uid.Tbl.find_opt cmt_infos.cmt_uid_to_decl uid with  
      | Some (Value v) ->
        deps := (loc, v.val_loc) :: !deps
      | Some (Type td) ->
        deps := (loc, td.typ_loc) :: !deps
      | Some (Value_binding vb) ->
        deps := (loc, vb.vb_loc) :: !deps
      | Some (Module_binding mb) ->
        deps := (loc, mb.mb_loc) :: !deps
      | Some (Module_type mt) ->
        deps := (loc, mt.mtd_loc) :: !deps
      | Some (Constructor cd) ->
        deps := (loc, cd.cd_loc) :: !deps
      | Some (Class c) ->
        deps := (loc, c.ci_loc) :: !deps
      | Some (Class_type ct) ->
        deps := (loc, ct.ci_loc) :: !deps
      | Some (Extension_constructor ec) ->
        deps := (loc, ec.ext_loc) :: !deps
      | Some (Label ld) ->
        deps := (loc, ld.ld_loc) :: !deps
      | Some (Module m) ->
        deps := (loc, m.md_loc) :: !deps
      | Some (Module_substitution ms) ->
        deps := (loc, ms.ms_loc) :: !deps
      | _ -> ())
     | _ -> () in
  List.iter process_id ident_occurrences;
  List.rev !deps

Moving this to draft.

[fantazio]

Hi @cristianoc ! Shameless plug here, this problem has been solved in the dead_code_analyzer (LexiFi/dead_code_analyzer#38) and you might be inspired by a similar solution.

TL;DR: the cmt_infos.cmt_value_dependencies is replaced by cmt_infos.cmt_declaration_dependencies, and one needs to read the cmt_infos.cmt_uid_to_decl to recreate the old association. A very important trick is that the table in the current cmt_infos may not be complete (see https://github.com/ocaml/ocaml/blob/5.3.0/typing/shape.mli), in which case it must be read in multiple .cmt and .cmti files to gather all the necessary information.

[cristianoc]

Sweet, thank you! This seems to work.

…

On Mon, 11 May 2026 at 18:19, Corentin De Souza ***@***.***> wrote: *fantazio* left a comment (rescript-lang/reanalyze#203) <#203 (comment)> Hi @cristianoc <https://github.com/cristianoc> ! Shameless plug here, this problem has been solved in the dead_code_analyzer ( LexiFi/dead_code_analyzer#38 <LexiFi/dead_code_analyzer#38>) and you might be inspired by a similar solution. TL;DR: the cmt_infos.cmt_value_dependencies is replaced by cmt_infos.cmt_declaration_dependencies, and one needs to read the cmt_infos.cmt_uid_to_decl to recreate the old association. A very important trick is that the table in the current cmt_infos may not be complete (see https://github.com/ocaml/ocaml/blob/5.3.0/typing/shape.mli), in which case it must be read in multiple .cmt and .cmti files to gather all the necessary information. — Reply to this email directly, view it on GitHub <#203 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AB4YVF2O7H5YMVSMLYZR4OT42H4PTAVCNFSM6AAAAACYZMM2TCVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHM2DIMRSGU3DEOJWGQ> . You are receiving this because you were mentioned.Message ID: ***@***.***>

[JonoPrest]

Hey @cristianoc

I can see this is WIP but I took this branch for a spin on the rescript-compiler itself. I built it against a 5.3 switch, ran dune build @check, then -dce-cmt _build/default. It runs cleanly end to end, but the cross-module reference tracking looks pretty off. It flags a lot of clearly-live stuff as dead. The one that jumped out was ast_helper is a dead module for example. Same thing for Lam_compile and Js_dump. Anything local to a module seems right, but as soon as something is exported via its .mli and used elsewhere, those uses seem to disappear and it gets called dead.

Either way still lots of useable warnings for dce, excited for this to work 💪🏼

[cristianoc]

Hey @cristianoc

I can see this is WIP but I took this branch for a spin on the rescript-compiler itself. I built it against a 5.3 switch, ran dune build @check, then -dce-cmt _build/default. It runs cleanly end to end, but the cross-module reference tracking looks pretty off. It flags a lot of clearly-live stuff as dead. The one that jumped out was ast_helper is a dead module for example. Same thing for Lam_compile and Js_dump. Anything local to a module seems right, but as soon as something is exported via its .mli and used elsewhere, those uses seem to disappear and it gets called dead.

Either way still lots of useable warnings for dce, excited for this to work 💪🏼

Might be worth checking whether it has to do with this (copied from the readme):

Make sure that dune builds both .cmt and .cmti files by enabling bytecode compilation. This is normally done by adding (modes byte exe) to the executable stanza in your dune file (see ocaml/dune#3182):

[JonoPrest]

Might be worth checking whether it has to do with this (copied from the readme):

Make sure that dune builds both .cmt and .cmti files by enabling bytecode compilation. This is normally done by adding (modes byte exe) to the executable stanza in your dune file (see ocaml/dune#3182):

I ran it with dune build @check, and I can see all the .cmt and .cmi files in _build/default