Merge pull request #1636 from ocaml/macos-stats

fix for issue #1634

CHANGES.md

@@ -7,6 +7,8 @@ unreleased
 - skip directories when looking up programs in the PATH (#1628, fixes
   #1616, @diml)
 
+- Use `lsof` on macOS to implement `--stats` (#1636, fixes #1634, @xclerc)
+
 - Generate `dune-package` files for every package. These files are installed and
   read instead of `META` files whenever they are available (#1329, @rgrinberg)
 

src/stats.ml

@@ -5,9 +5,30 @@ let enabled = ref false
 module Fd_count = struct
   type t = Unknown | This of int
 
+  let try_to_use_lsof () =
+    (* note: we do not use the Process module here, because it would
+       create a circular dependency *)
+    let temp = Filename.temp_file "dune" ".lsof" in
+    let stdout =
+      Unix.openfile temp [O_WRONLY; O_CREAT; O_TRUNC; O_SHARE_DELETE] 0o666
+    in
+    let prog = "/usr/sbin/lsof" in
+    let argv = [prog; "-w"; "-p"; string_of_int (Unix.getpid ())] in
+    let pid = Spawn.spawn ~prog ~argv ~stdout () in
+    Unix.close stdout;
+    match Unix.waitpid [] pid with
+    | _, Unix.WEXITED 0 ->
+      let num_lines = List.length (Io.input_lines (open_in temp)) in
+      This (num_lines - 1) (* the output contains a header line *)
+    | _ -> Unknown
+
   let get () =
     match Sys.readdir "/proc/self/fd" with
-    | exception _ -> Unknown
+    | exception _ ->
+      begin match try_to_use_lsof () with
+      | exception _ -> Unknown
+      | value -> value
+      end
     | files -> This (Array.length files - 1 (* -1 for the dirfd *))
 
   let map2 ~f a b =