Enabled the preprocessing by CPP of #include directives in Ligo.

Now it is possible to write anywhere in a Ligo source file

and have error messages refer to the correct file and line. This
is done by extending the lexer to recognise #line
directives (generated by CPP).

I added the stage "cpp" for the --verbose command-line option: if
given, the preprocessed source file is created in the current
directory with the name <input>.pp.li, where <input>.li is the
original input file. Also the CPP command actually run is
printed.

I added setter to modules [Pos] and [Region].

EvalOpt.ml

@@ -20,7 +20,7 @@ let help () =
   print_endline "  -q, --quiet            No output, except errors (default)";
   print_endline "      --columns          Columns for source locations";
   print_endline "      --bytes            Bytes for source locations";
-  print_endline "      --verbose=<stages> cmdline, ast";
+  print_endline "      --verbose=<stages> cmdline, cpp, ast";
   print_endline "      --version          Commit hash on stdout";
   print_endline "  -h, --help             This help";
   exit 0

Lexer.mll

@@ -46,13 +46,30 @@ let reset_file ~file buffer =
   let open Lexing in
   buffer.lex_curr_p <- {buffer.lex_curr_p with pos_fname = file}
 
-let reset_line line_num buffer =
+let reset_line ~line buffer =
+  assert (line >= 0);
   let open Lexing in
-  buffer.lex_curr_p <- {buffer.lex_curr_p with pos_lnum = line_num}
+  buffer.lex_curr_p <- {buffer.lex_curr_p with pos_lnum = line}
 
-let reset ~file ?(line=1) buffer =
-  (* Default value per the [Lexing] standard module convention *)
-  reset_file ~file buffer; reset_line line buffer
+let reset_offset ~offset buffer =
+  assert (offset >= 0);
+  Printf.printf "[reset] offset=%i\n" offset;
+  let open Lexing in
+  let bol = buffer.lex_curr_p.pos_bol in
+  buffer.lex_curr_p <- {buffer.lex_curr_p with pos_cnum = bol (*+ offset*)}
+
+let reset ?file ?line ?offset buffer =
+  let () =
+    match file with
+      Some file -> reset_file ~file buffer
+    |      None -> () in
+  let () =
+    match line with
+      Some line -> reset_line ~line buffer
+    |      None -> () in
+  match offset with
+    Some offset -> reset_offset ~offset buffer
+  |        None -> ()
 
 (* Rolling back one lexeme _within the current semantic action_ *)
 
@@ -192,12 +209,12 @@ module Make (Token: TOKEN) : (S with module Token = Token) =
 
     (* STATE *)
 
-    (* Beyond tokens, the result of lexing is a state (a so-called
-       _state monad_). The type [state] represents the logical state
-       of the lexing engine, that is, a value which is threaded during
-       scanning and which denotes useful, high-level information
-       beyond what the type [Lexing.lexbuf] in the standard library
-       already provides for all generic lexers.
+    (* Beyond tokens, the result of lexing is a state. The type
+       [state] represents the logical state of the lexing engine, that
+       is, a value which is threaded during scanning and which denotes
+       useful, high-level information beyond what the type
+       [Lexing.lexbuf] in the standard library already provides for
+       all generic lexers.
 
          Tokens are the smallest units used by the parser to build the
        abstract syntax tree. The state includes a queue of recognised
@@ -427,6 +444,7 @@ module Make (Token: TOKEN) : (S with module Token = Token) =
 
 let utf8_bom   = "\xEF\xBB\xBF" (* Byte Order Mark for UTF-8 *)
 let nl         = ['\n' '\r'] | "\r\n"
+let blank      = ' ' | '\t'
 let digit      = ['0'-'9']
 let natural    = digit | digit (digit | '_')* digit
 let integer    = '-'? natural
@@ -446,6 +464,7 @@ let symbol     = ';' | ','
                | '#' | '|' | "->" | ":=" | '=' | ':'
                | "||" | "&&" | '<' | "<=" | '>' | ">=" | "=/="
                | '+' | '-' | '*' | '.' | '_' | '^'
+let string     = [^'"' '\\' '\n']*  (* For strings of #include *)
 
 (* RULES *)
 
@@ -487,6 +506,43 @@ and scan state = parse
          let state  = scan_line thread state lexbuf |> push_line
          in scan state lexbuf }
 
+  (* Management of #include CPP directives
+
+    An input Ligo program may contain GNU CPP (C preprocessor)
+    directives, and the entry modules (named *Main.ml) run CPP on them
+    in traditional mode:
+
+    https://gcc.gnu.org/onlinedocs/cpp/Traditional-Mode.html
+
+      The main interest in using CPP is that it can stand for a poor
+    man's (flat) module system for Ligo thanks to #include
+    directives, and the traditional mode leaves the markup mostly
+    undisturbed.
+
+      Some of the #line resulting from processing #include directives
+    deal with system file headers and thus have to be ignored for our
+    purpose. Moreover, these #line directives may also carry some
+    additional flags:
+
+    https://gcc.gnu.org/onlinedocs/cpp/Preprocessor-Output.html
+
+    of which 1 and 2 indicate, respectively, the start of a new file
+    and the return from a file (after its inclusion has been
+    processed).
+  *)
+
+| '#' blank* ("line" blank+)? (integer as line) blank+
+    '"' (string as file) '"' {
+    let  _, _, state = sync state lexbuf in
+    let flags, state = scan_flags state [] lexbuf in
+    let           () = ignore flags in
+    let line         = int_of_string line
+    and file         = Filename.basename file in
+    let pos          = state.pos#set ~file ~line ~offset:0 in
+    let state        = {state with pos} in
+    scan state lexbuf
+  }
+
   (* Some special errors
 
      Some special errors are recognised in the semantic actions of the
@@ -517,6 +573,18 @@ and scan state = parse
 | _ as c { let region, _, _ = sync state lexbuf
            in fail region (Unexpected_character c) }
 
+(* Scanning CPP #include flags *)
+
+and scan_flags state acc = parse
+  blank+          { let _, _, state = sync state lexbuf
+                    in scan_flags state acc lexbuf          }
+| integer as code { let _, _, state = sync state lexbuf in
+                    let acc = int_of_string code :: acc
+                    in scan_flags state acc lexbuf          }
+| nl              { List.rev acc, push_newline state lexbuf }
+| eof             { let _, _, state = sync state lexbuf
+                    in List.rev acc, state       (* TODO *) }
+
 (* Finishing a string *)
 
 and scan_string thread state = parse

LexerMain.ml

@@ -9,9 +9,38 @@ let () = Printexc.record_backtrace true
 let external_ text =
   Utils.highlight (Printf.sprintf "External error: %s" text); exit 1;;
 
+(* Preprocessing the input source and opening the input channels *)
+
+let prefix =
+  match EvalOpt.input with
+    None | Some "-" -> "temp"
+  | Some file ->  Filename.(file |> basename |> remove_extension)
+
+let suffix = ".pp.li"
+
+let pp_input =
+  if Utils.String.Set.mem "cpp" EvalOpt.verbose
+  then prefix ^ suffix
+  else let pp_input, pp_out = Filename.open_temp_file prefix suffix
+       in close_out pp_out; pp_input
+
+let cpp_cmd =
+  match EvalOpt.input with
+    None | Some "-" ->
+      Printf.sprintf "cpp -traditional-cpp - -o %s" pp_input
+  | Some file ->
+      Printf.sprintf "cpp -traditional-cpp %s -o %s" file pp_input
+
+let () =
+  if Utils.String.Set.mem "cpp" EvalOpt.verbose
+  then Printf.eprintf "%s\n%!" cpp_cmd;
+  if Sys.command cpp_cmd <> 0 then
+    external_ (Printf.sprintf "the command \"%s\" failed." cpp_cmd)
+
 (* Running the lexer on the input file *)
 
 module Lexer = Lexer.Make (LexToken)
 
+
 let () = Lexer.trace ~offsets:EvalOpt.offsets
-                     EvalOpt.mode EvalOpt.input EvalOpt.cmd
+                     EvalOpt.mode (Some pp_input) EvalOpt.cmd

ParserMain.ml

@@ -34,12 +34,40 @@ let lib_path =
             in List.fold_right mk_I libs ""
 *)
 
+(* Preprocessing the input source and opening the input channels *)
+
+let prefix =
+  match EvalOpt.input with
+    None | Some "-" -> "temp"
+  | Some file ->  Filename.(file |> basename |> remove_extension)
+
+let suffix = ".pp.li"
+
+let pp_input =
+  if Utils.String.Set.mem "cpp" EvalOpt.verbose
+  then prefix ^ suffix
+  else let pp_input, pp_out = Filename.open_temp_file prefix suffix
+       in close_out pp_out; pp_input
+
+let cpp_cmd =
+  match EvalOpt.input with
+    None | Some "-" ->
+      Printf.sprintf "cpp -traditional-cpp - -o %s" pp_input
+  | Some file ->
+      Printf.sprintf "cpp -traditional-cpp %s -o %s" file pp_input
+
+let () =
+  if Utils.String.Set.mem "cpp" EvalOpt.verbose
+  then Printf.eprintf "%s\n%!" cpp_cmd;
+  if Sys.command cpp_cmd <> 0 then
+    external_ (Printf.sprintf "the command \"%s\" failed." cpp_cmd)
+
 (* Instanciating the lexer *)
 
 module Lexer = Lexer.Make (LexToken)
 
 let Lexer.{read; buffer; get_pos; get_last; close} =
-  Lexer.open_token_stream EvalOpt.input
+  Lexer.open_token_stream (Some pp_input)
 
 and cout = stdout
 

Pos.ml

@@ -7,6 +7,8 @@ type t = <
 
   set_file   : string -> t;
   set_line   : int -> t;
+  set_offset : int -> t;
+  set        : file:string -> line:int -> offset:int -> t;
   new_line   : string -> t;
   add_nl     : t;
 
@@ -44,8 +46,20 @@ let make ~byte ~point_num ~point_bol =
     val    point_bol = point_bol
     method point_bol = point_bol
 
-    method set_file file = {< byte = Lexing.{byte with pos_fname = file} >}
-    method set_line line = {< byte = Lexing.{byte with pos_lnum  = line} >}
+    method set_file file =
+      {< byte = Lexing.{byte with pos_fname = file} >}
+
+    method set_line line =
+      {< byte = Lexing.{byte with pos_lnum = line} >}
+
+    method set_offset offset =
+      {< byte = Lexing.{byte with pos_cnum = byte.pos_bol + offset} >}
+
+    method set ~file ~line ~offset =
+      let pos = self#set_file file in
+      let pos = pos#set_line line in
+      let pos = pos#set_offset offset
+      in pos
 
     (* The string must not contain '\n'. See [new_line]. *)
 

Pos.mli

@@ -36,6 +36,8 @@ type t = <
 
   set_file   : string -> t;
   set_line   : int -> t;
+  set_offset : int -> t;
+  set        : file:string -> line:int -> offset:int -> t;
 
   (* The call [pos#new_line s], where the string [s] is either "\n" or
      "\c\r", updates the position [pos] with a new line. *)

Region.ml

@@ -10,6 +10,7 @@ type t = <
 
   shift_bytes     : int -> t;
   shift_one_uchar : int -> t;
+  set_file        : string -> t;
 
   (* Getters *)
 
@@ -55,6 +56,11 @@ let make ~(start: Pos.t) ~(stop: Pos.t) =
         and stop  = stop#shift_one_uchar len
         in {< start = start; stop = stop >}
 
+      method set_file name =
+        let start = start#set_file name
+        and stop  = stop#set_file name
+        in {< start = start; stop = stop >}
+
       (* Getters *)
 
       method file      = start#file

Region.mli

@@ -24,10 +24,12 @@ type t = <
      translation of region [region] of [n] bytes forward in the
      file. The call [region#shift_one_uchar n] is similar, except that
      it assumes that [n] is the number of bytes making up one unicode
-     point. *)
+     point. The call [region#set_file f] sets the file name to be
+     [f]. *)
 
   shift_bytes     : int -> t;
   shift_one_uchar : int -> t;
+  set_file        : string -> t;
 
   (* Getters *)