Get constant strings through stubs.

src/dune

@@ -1,6 +1,17 @@
 (library
  (name lilv)
  (public_name lilv)
- (libraries ctypes ctypes.foreign)
+ (libraries lilv.stubs ctypes ctypes.foreign)
+ (c_names lilv_generated_stubs)
  (c_library_flags "-llilv-0")
 )
+
+(rule
+ (targets lilv_generated_stubs.ml)
+ (deps    (:gen ./generator/gen_stubs.exe))
+ (action  (run %{gen} ml %{targets})))
+
+(rule
+ (targets lilv_generated_stubs.c)
+ (deps    (:gen ./generator/gen_stubs.exe))
+ (action  (run %{gen} c %{targets})))

src/generator/dune

@@ -0,0 +1,4 @@
+(executable
+ (name gen_stubs)
+ (modules gen_stubs)
+ (libraries lilv.stubs ctypes.stubs))

src/generator/gen_stubs.ml

@@ -0,0 +1,26 @@
+let c_headers = "
+#include <lv2.h>
+
+static char *ocaml_lv2_core_uri() {
+  return LV2_CORE_URI;
+}
+"
+
+let () =
+  let mode = Sys.argv.(1) in
+  let fname = Sys.argv.(2) in
+  let oc = open_out_bin fname in
+  let format =
+    Format.formatter_of_out_channel oc
+  in
+  let fn =
+    match mode with
+      | "ml" -> Cstubs.write_ml
+      | "c"  ->
+         Format.fprintf format "%s@\n" c_headers;
+         Cstubs.write_c
+      | _    -> assert false
+  in
+  fn format ~prefix:"ocaml_lilv" (module Lilv_stubs.Def);
+  Format.pp_print_flush format ();
+  close_out oc

src/lilv.ml

@@ -1,6 +1,8 @@
 open Ctypes
 open Foreign
 
+module Stubs = Lilv_stubs.Def(Lilv_generated_stubs)
+
 module LV2 = struct
   type handle = unit ptr
   let handle : handle typ = ptr void
@@ -23,7 +25,7 @@ module LV2 = struct
     seal descriptor
 
   module Core = struct
-    let uri = "http://lv2plug.in/ns/lv2core"
+    let uri = Stubs.core_uri ()
 
     let prefix s = uri ^ "#" ^ s
 

src/stubs/dune

@@ -0,0 +1,8 @@
+(env
+  (dev
+     (flags (:standard -warn-error -A))))
+
+(library
+ (name lilv_stubs)
+ (public_name lilv.stubs)
+ (libraries ctypes.stubs))

src/stubs/lilv_stubs.ml

@@ -0,0 +1,7 @@
+open Ctypes
+
+module Def (F : Cstubs.FOREIGN) = struct
+  open F
+
+  let core_uri = foreign "ocaml_lv2_core_uri" (void @-> returning string)
+end