Module Location

module Location: sig .. end

Source code locations (ranges of positions), used in parsetree.

Warning: this module is unstable and part of compiler-libs.

type t = Warnings.loc = {
   loc_start : Lexing.position;
   loc_end : Lexing.position;
   loc_ghost : bool;

Note on the use of Lexing.position in this module. If pos_fname = "", then use !input_name instead. If pos_lnum = -1, then pos_bol = 0. Use pos_cnum and re-parse the file to get the line and character numbers. Else all fields are correct.

val none : t

An arbitrary value of type t; describes an empty ghost range.

val is_none : t -> bool

True for Location.none, false any other location

val in_file : string -> t

Return an empty ghost range located in a given file.

val init : Lexing.lexbuf -> string -> unit

Set the file name and line number of the lexbuf to be the start of the named file.

val curr : Lexing.lexbuf -> t

Get the location of the current token from the lexbuf.

val symbol_rloc : unit -> t
val symbol_gloc : unit -> t
val rhs_loc : int -> t

rhs_loc n returns the location of the symbol at position n, starting at 1, in the current parser rule.

val rhs_interval : int -> int -> t
val get_pos_info : Lexing.position -> string * int * int

file, line, char

type 'a loc = {
   txt : 'a;
   loc : t;
val mknoloc : 'a -> 'a loc
val mkloc : 'a -> t -> 'a loc

Input info

val input_name : string ref
val input_lexbuf : Lexing.lexbuf option ref
val input_phrase_buffer : Buffer.t option ref

Toplevel-specific functions

val echo_eof : unit -> unit
val separate_new_message : Format.formatter -> unit
val reset : unit -> unit

Rewriting path

val rewrite_absolute_path : string -> string

rewrite_absolute_path path rewrites path to honor the BUILD_PATH_PREFIX_MAP variable if it is set. It does not check whether path is absolute or not. The result is as follows:

  • If BUILD_PATH_PREFIX_MAP is not set, just return path.
  • otherwise, rewrite using the mapping (and if there are no matching prefixes that will just return path).


val rewrite_find_first_existing : string -> string option

rewrite_find_first_existing path uses a BUILD_PATH_PREFIX_MAP mapping and tries to find a source in mapping that maps to a result that exists in the file system. There are the following return values:

  • None, means either
    • BUILD_PATH_PREFIX_MAP is not set and path does not exists, or
    • no source prefixes of path in the mapping were found,
  • Some target, means target exists and either
    • BUILD_PATH_PREFIX_MAP is not set and target = path, or
    • target is the first file (in priority order) that path mapped to that exists in the file system.
  • Not_found raised, means some source prefixes in the map were found that matched path, but none of them existed in the file system. The caller should catch this and issue an appropriate error message.


val rewrite_find_all_existing_dirs : string -> string list

rewrite_find_all_existing_dirs dir accumulates a list of existing directories, dirs, that are the result of mapping a potentially abstract directory, dir, over all the mapping pairs in the BUILD_PATH_PREFIX_MAP environment variable, if any. The list dirs will be in priority order (head as highest priority).

The possible results are:

  • [], means either
    • BUILD_PATH_PREFIX_MAP is not set and dir is not an existing directory, or
    • if set, then there were no matching prefixes of dir.
  • Some dirs, means dirs are the directories found. Either
    • BUILD_PATH_PREFIX_MAP is not set and dirs = [dir], or
    • it was set and dirs are the mapped existing directories.
  • Not_found raised, means some source prefixes in the map were found that matched dir, but none of mapping results were existing directories (possibly due to misconfiguration). The caller should catch this and issue an appropriate error message.


val absolute_path : string -> string

absolute_path path first makes an absolute path, s from path, prepending the current working directory if path was relative. Then s is rewritten using rewrite_absolute_path. Finally the result is normalized by eliminating instances of '.' or '..'.

Printing locations

val show_filename : string -> string

In -absname mode, return the absolute path for this filename. Otherwise, returns the filename unchanged.

val print_filename : Format.formatter -> string -> unit
val print_loc : Format.formatter -> t -> unit
val print_locs : Format.formatter -> t list -> unit

Toplevel-specific location highlighting

val highlight_terminfo : Lexing.lexbuf -> Format.formatter -> t list -> unit

Reporting errors and warnings

The type of reports and report printers

type msg = (Format.formatter -> unit) loc 
val msg : ?loc:t ->
('a, Format.formatter, unit, msg) format4 -> 'a
type report_kind = 
| Report_error
| Report_warning of string
| Report_warning_as_error of string
| Report_alert of string
| Report_alert_as_error of string
type report = {
   kind : report_kind;
   main : msg;
   sub : msg list;
type report_printer = {
   pp : report_printer -> Format.formatter -> report -> unit;
   pp_report_kind : report_printer ->
report -> Format.formatter -> report_kind -> unit
   pp_main_loc : report_printer ->
report -> Format.formatter -> t -> unit
   pp_main_txt : report_printer ->
report ->
Format.formatter -> (Format.formatter -> unit) -> unit
   pp_submsgs : report_printer ->
report -> Format.formatter -> msg list -> unit
   pp_submsg : report_printer ->
report -> Format.formatter -> msg -> unit
   pp_submsg_loc : report_printer ->
report -> Format.formatter -> t -> unit
   pp_submsg_txt : report_printer ->
report ->
Format.formatter -> (Format.formatter -> unit) -> unit

A printer for reports, defined using open-recursion. The goal is to make it easy to define new printers by re-using code from existing ones.

Report printers used in the compiler

val batch_mode_printer : report_printer
val terminfo_toplevel_printer : Lexing.lexbuf -> report_printer
val best_toplevel_printer : unit -> report_printer

Detects the terminal capabilities and selects an adequate printer

Printing a report

val print_report : Format.formatter -> report -> unit

Display an error or warning report.

val report_printer : (unit -> report_printer) ref

Hook for redefining the printer of reports.

The hook is a unit -> report_printer and not simply a report_printer: this is useful so that it can detect the type of the output (a file, a terminal, ...) and select a printer accordingly.

val default_report_printer : unit -> report_printer

Original report printer for use in hooks.

Reporting warnings

Converting a Warnings.t into a report

val report_warning : t -> Warnings.t -> report option

report_warning loc w produces a report for the given warning w, or None if the warning is not to be printed.

val warning_reporter : (t -> Warnings.t -> report option) ref

Hook for intercepting warnings.

val default_warning_reporter : t -> Warnings.t -> report option

Original warning reporter for use in hooks.

Printing warnings

val formatter_for_warnings : Format.formatter ref
val print_warning : t -> Format.formatter -> Warnings.t -> unit

Prints a warning. This is simply the composition of report_warning and print_report.

val prerr_warning : t -> Warnings.t -> unit

Same as print_warning, but uses !formatter_for_warnings as output formatter.

Reporting alerts

Converting an Alert.t into a report

val report_alert : t -> Warnings.alert -> report option

report_alert loc w produces a report for the given alert w, or None if the alert is not to be printed.

val alert_reporter : (t -> Warnings.alert -> report option) ref

Hook for intercepting alerts.

val default_alert_reporter : t -> Warnings.alert -> report option

Original alert reporter for use in hooks.

Printing alerts

val print_alert : t -> Format.formatter -> Warnings.alert -> unit

Prints an alert. This is simply the composition of report_alert and print_report.

val prerr_alert : t -> Warnings.alert -> unit

Same as print_alert, but uses !formatter_for_warnings as output formatter.

val deprecated : ?def:t -> ?use:t -> t -> string -> unit

Prints a deprecation alert.

val alert : ?def:t ->
?use:t -> kind:string -> t -> string -> unit

Prints an arbitrary alert.

val auto_include_alert : string -> unit

Prints an alert that -I +lib has been automatically added to the load path

val deprecated_script_alert : string -> unit

deprecated_script_alert command prints an alert that command foo has been deprecated in favour of command ./foo

Reporting errors

type error = report 

An error is a report which report_kind must be Report_error.

val error : ?loc:t -> ?sub:msg list -> string -> error
val errorf : ?loc:t ->
?sub:msg list ->
('a, Format.formatter, unit, error) format4 -> 'a
val error_of_printer : ?loc:t ->
?sub:msg list ->
(Format.formatter -> 'a -> unit) -> 'a -> error
val error_of_printer_file : (Format.formatter -> 'a -> unit) -> 'a -> error

Automatically reporting errors for raised exceptions

val register_error_of_exn : (exn -> error option) -> unit

Each compiler module which defines a custom type of exception which can surface as a user-visible error should register a "printer" for this exception using register_error_of_exn. The result of the printer is an error value containing a location, a message, and optionally sub-messages (each of them being located as well).

val error_of_exn : exn -> [ `Already_displayed | `Ok of error ] option
exception Error of error

Raising Error e signals an error e; the exception will be caught and the error will be printed.

exception Already_displayed_error

Raising Already_displayed_error signals an error which has already been printed. The exception will be caught, but nothing will be printed

val raise_errorf : ?loc:t ->
?sub:msg list ->
('a, Format.formatter, unit, 'b) format4 -> 'a
val report_exception : Format.formatter -> exn -> unit

Reraise the exception if it is unknown.