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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