INTERNAL_APPLICATION.md

The reference files for this example are in the internal_app directory.

The reference takes place in /tmp/docs/optional_arguments/code_constructs, which is a copy of the code_constructs directory. Reported locations may differ depending on the location of the source files.

The compilation command is :

make -C internal_app build

The analysis command is :

make -C internal_app analyze

The compile + analyze command is :

make -C internal_app

First run

Code:

(* internal_app_lib.mli *)
val max : ?min:'a -> 'a -> 'a -> 'a
val min : ?max:'a -> 'a -> 'a -> 'a

(* internal_app_lib.ml *)
let max ?min x y =
  let max x y = if x > y then x else y in
  let res = max x y in
  match min with
  | None -> res
  | Some m -> max m res

let min ?max x y =
  let min x y = if x < y then x else y in
  let res = min x y in
  match max with
  | None -> res
  | Some m -> min m res

let () =
  let max = max 0 42 in
  let min = min ~max 100 200 in
  assert (min = max)

Before looking at the analysis results, let's look at the code.

There are 2 functions defined and exported by Internal_app_lib: max and min. They both have an optional argument, and both functions are used internally. Neither is used externally. Optional argument ?min of max is never used. Optional argument ?max of min is always used.

Compile and analyze:

$ make -C internal_app
make: Entering directory '/tmp/docs/opt_args/code_constructs/internal_app'
ocamlopt -bin-annot internal_app_lib.mli internal_app_lib.ml
dead_code_analyzer --nothing -Oa all -On all .
Scanning files...
 [DONE]

.> OPTIONAL ARGUMENTS: ALWAYS:
=============================
/tmp/docs/opt_args/code_constructs/internal_app/internal_app_lib.ml:9: ?max

Nothing else to report in this section
--------------------------------------------------------------------------------


.> OPTIONAL ARGUMENTS: NEVER:
============================
/tmp/docs/opt_args/code_constructs/internal_app/internal_app_lib.ml:2: ?min

Nothing else to report in this section
--------------------------------------------------------------------------------


make: Leaving directory '/tmp/docs/opt_args/code_constructs/internal_app'

As expected, ?max is reported always used and ?min never used.

Because all the uses of the functions are inside their compilation unit, the analyzer reports locations in the .ml and not the .mli. This is the opposite of the External application example.

Fixing the reports

Code:

(* internal_app_lib.mli *)
val max : 'a -> 'a -> 'a
val min : max:'a -> 'a -> 'a -> 'a

(* internal_app_lib.ml *)
let max x y =
  if x > y then x else y

let min ~max x y =
  let min x y = if x < y then x else y in
  let res = min x y in
  min max res

let () =
  let max = max 0 42 in
  let min = min ~max 100 200 in
  assert (min = max)

We removed ?min from function max and simplified its body. We transformed ?max into a mandatory labeled argument ~max in function min.

The signatures of the functions in the .mli have been changed accordingly.

Note

Because the functions min and max are exported but not used outside their compilation unit, the analyzer can report them as unused exported values, and we could simply remove them from the .mli. More details available in the Exported values documentation.

Compile and analyze:

$ make -C internal_app
make: Entering directory '/tmp/docs/opt_args/code_constructs/internal_app'
ocamlopt -bin-annot internal_app_lib.mli internal_app_lib.ml
dead_code_analyzer --nothing -Oa all -On all .
Scanning files...
 [DONE]

.> OPTIONAL ARGUMENTS: ALWAYS:
=============================

Nothing else to report in this section
--------------------------------------------------------------------------------


.> OPTIONAL ARGUMENTS: NEVER:
============================

Nothing else to report in this section
--------------------------------------------------------------------------------


make: Leaving directory '/tmp/docs/opt_args/code_constructs/internal_app'

The analyzer does not report anything. Our work here is done.