Hello,


I'm using ocamlbuild and menhir to compile my project. I was faced with some small issues and decided to try some small patches on the menhir source code, which I explain below.


1)      Error found with --infer options have bad location
When ocamlbuild invoke menhir to file which is in a sub-directory, ie launch the command "menhir --infer MyDir/MyParser.mly", if I have a type error in my parser, I get the message

File "MyParser.mly", line 32, characters 41-42: ...

Instead of

File "MyDir/MyParser.mly", line 32, characters 41-42: ...

I understand this is because in the generated file MyDir/MyParser.ml, the #line directives are written
                # 239 " MyParser.mly "
instead of
                # 239 "MyDir/MyParser.mly "

So I try to make a little change in menhir's source files. In file error.ml, I commented out the "Filename.basename" :
let set_filename name =
  basename := Some ((* Filename.basename  *)name);
  filemark := Mark.fresh()

and idem in back.ml :
let write program =
  let module P = Printer.Make (struct
    let filename = Settings.base ^ ".ml"
    let f = open_out filename
    let locate_stretches =
      if Settings.infer then
      (* Typechecking should not fail at this stage. Omit #line directives. *)
      None
      else
      Some ((* Filename.basename *) filename)
    let raw_stretch_action = false
  end) in
  P.program program

This is correct the issue but I do not know if it is the good correction. At least, this seems the way ocamlyacc works.


2)      Ocamlbuild, menhir and the -table option

Ocamlbuild fails is menhir is used with "-table" option because it does'nt link with the MenhirLib library (--table option is required when grammar becomes large). So I changed the two menhir's makefiles to generate .cma and .cmxa and create the following ocamlbuild's plugin:
open Ocamlbuild_plugin;;
open Command;;

let menhirLibDir () =
  Command.execute( Cmd (Sh "menhir --suggest-comp-flags --table > tmp.txt"));
  let path = match string_list_of_file ( "tmp.txt") with
    | [_;path] -> path
    | _ -> assert false in
  rm_f "tmp.txt";
  path
;;

dispatch begin function
| After_rules ->
  let menhirLibDir = menhirLibDir () in
  ocaml_lib ~extern:true ~dir:menhirLibDir ~tag_name:"use_menhir_table" "menhirLib";
  flag [ "ocaml" ; "menhir";"use_menhir_table" ] (S[A "--table"]);
| _ -> ()
end;;

and with the following _tags flag, it compiles:
<**/*.ml>: use_menhir_table
<**/*.mly>: explain, use_menhir_table
true: use_menhir
<**/*.{byte,native}>: use_menhir_table

Maybe could this changes be integrated in the official myocamlbuild source files ?



3)      Menhir (like ocamlyacc) only raise a warning when it finds  a shift/reduce or reduce/reduce conflict.

I propose to add an option "--conflict-is-error" which make menhir fail if it finds conflicts. Changes are very small in menhir source code. I have added the option in Setting.ml and change the "report statistic" code from


let () =
  if !shift_reduce = 1 then
    Error.warning "one state has shift/reduce conflicts."
  else if !shift_reduce > 1 then
    Error.warning (Printf.sprintf "%d states have shift/reduce conflicts." !shift_reduce);
  if !reduce_reduce = 1 then
    Error.warning "one state has reduce/reduce conflicts."
  else if !reduce_reduce > 1 then
    Error.warning (Printf.sprintf "%d states have reduce/reduce conflicts." !reduce_reduce)



to


let () =
  let print = if !Settings.conflict_is_error then (fun s -> Error.signalN [] ("Error: "^s)) else Error.warning in
  if !shift_reduce = 1 then
    print "one state has shift/reduce conflicts."
  else if !shift_reduce > 1 then
    print (Printf.sprintf "%d states have shift/reduce conflicts." !shift_reduce);
  if !reduce_reduce = 1 then
    print "one state has reduce/reduce conflicts."
  else if !reduce_reduce > 1 then
    print (Printf.sprintf "%d states have reduce/reduce conflicts." !reduce_reduce)


Could these patches be integrated in Menhir next release ?

Daniel Weil

PS : as the menhir-list doesn't seems to work, I'm using the caml-list.




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