Fix copy# for Microsoft C compiler

Microsoft CL doesn't support #n and requires the more strictly correct
directive #line

Signed-off-by: David Allsopp <david.allsopp@metastack.com>

CHANGES.md

@@ -26,6 +26,8 @@ next
 
 - Fix doc generation when several private libraries have the same name (#369)
 
+- Fix copy# for C/C++ with Microsoft C compiler (#353)
+
 1.0+beta16 (05/11/2017)
 -----------------------
 

src/action.ml

@@ -596,7 +596,13 @@ let rec exec t ~ectx ~dir ~env_extra ~stdout_to ~stderr_to =
     Io.with_file_in (Path.to_string src) ~f:(fun ic ->
       Io.with_file_out (Path.to_string dst) ~f:(fun oc ->
         let fn = Path.drop_build_context src in
-        Printf.fprintf oc "# 1 %S\n" (Path.to_string fn);
+        let directive =
+          if List.mem (Path.extension fn) ~set:[".c"; ".cpp"; ".h"] then
+            "line"
+          else
+            ""
+        in
+        Printf.fprintf oc "#%s 1 %S\n" directive (Path.to_string fn);
         Io.copy_channels ic oc));
     return ()
   | System cmd ->

src/path.ml

@@ -426,4 +426,6 @@ let change_extension ~ext t =
   let t = try Filename.chop_extension t with Not_found -> t in
   t ^ ext
 
+let extension = Filename.extension
+
 let pp = Format.pp_print_string

src/path.mli

@@ -112,4 +112,6 @@ val rm_rf : t -> unit
 (** Changes the extension of the filename (or adds an extension if there was none) *)
 val change_extension : ext:string -> t -> t
 
+val extension : t -> string
+
 val pp : t Fmt.t